Patent Publication Number: US-2021177415-A1

Title: Stapling adjunct attachment

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. patent application Ser. No. 16/931,759 filed on Jul. 17, 2020, entitled “Stapling Adjunct Attachment,” which is a continuation of U.S. patent application Ser. No. 15/436,394, now U.S. Pat. No. 10,716,564, filed on Feb. 17, 2017, entitled “Stapling Adjunct Attachment,” each of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD 
     Methods and devices are provided for securing one or more adjunct materials to an end effector of a surgical instrument. 
     BACKGROUND 
     Surgical staplers are used in surgical procedures to close openings in tissue, blood vessels, ducts, shunts, or other objects or body parts involved in the particular procedure. The openings can be naturally occurring, such as passageways in blood vessels or an internal organ like the stomach, or they can be formed by the surgeon during a surgical procedure, such as by puncturing tissue or blood vessels to form a bypass or an anastomosis, or by cutting tissue during a stapling procedure. 
     Most staplers have a handle with an elongate shaft having an end effector with a pair of movable opposed jaws for engaging and stapling tissue. The staples are typically contained in a staple cartridge, which can house multiple rows of staples and that is often disposed in one of the jaws for ejection of the staples to the surgical site. In use, the jaws are positioned to engage tissue, and the device is actuated to eject staples through the tissue. Some staplers include a knife configured to travel between rows of staples in the staple cartridge to longitudinally cut the stapled tissue between the stapled rows. 
     While surgical staplers have improved over the years, a number of problems still present themselves. One common problem is that leaks can occur due to the staple forming holes when penetrating the tissue or other object in which it is disposed. Blood, air, gastrointestinal fluids, and other fluids can seep through the openings formed by the staples, even after the staple is fully formed. The tissue being treated can also become inflamed due to the trauma that results from stapling. Still further, staples, as well as other objects and materials that can be implanted in conjunction with procedures like stapling, generally lack some characteristics of the tissue in which they are implanted. For example, staples and other objects and materials can lack the natural flexibility of the tissue in which they are implanted. A person skilled in the art will recognize that it is often desirable for tissue to maintain as much of its natural characteristics as possible after staples are disposed therein. 
     Accordingly, there remains a need for improved devices and methods for stapling tissue, blood vessels, ducts, shunts, or other objects or body parts such that leaking and inflammation is minimized while substantially maintaining the natural characteristics of the treatment region. 
     SUMMARY 
     Methods for stapling tissue are provided. In one embodiment, the method can include positioning an adjunct on one of first and second jaws of an end effector of a surgical stapler. The adjunct can have an adhesive thereon that maintains the adjunct on the jaw. The method can also include positioning tissue between the first and second jaws, and actuating the surgical stapler to cause the first and second jaws to move from an open position to a closed position in which the tissue is engaged therebetween. A first attachment mechanism on the adjunct can prevent stretching of at least a portion of the adjunct. 
     In one embodiment, the first attachment mechanism can be at least one post formed on one of the adjunct and the jaw, and at least one bore formed on the other one of the adjunct and the jaw for receiving the post. In further aspects, a second attachment mechanism on the adjunct can prevent sliding of the adjunct relative to the jaw having the adjunct disposed thereon. The second attachment mechanism on the adjunct can prevent lateral sliding and/or longitudinal sliding of the adjunct relative to a longitudinal axis of the jaw. In other aspects, a second attachment mechanism on the adjunct can prevent curling of a distal-most end of the adjunct when the tissue is positioned between the first and second jaws. 
     In another embodiment, a method for stapling tissue is provided and includes positioning an adjunct on at least one jaw of first and second jaws of an end effector of a surgical stapler. The adjunct can be maintained on the at least one jaw in a first state in which the adjunct is at least partially stretched over the at least one jaw. The method can also include positioning tissue between the first and second jaws, and actuating the surgical stapler to cause the first and second jaws to move from an open position to a closed position in which the tissue is engaged therebetween. Actuation of the surgical stapler can cause the adjunct to transition from the first state to a second state such that the adjunct in the second state at least partially separates from the at least one jaw. 
     In certain embodiments, actuation of the surgical stapler can include causing a cutting element of the surgical stapler to move to thereby cut through at least a portion of the adjunct to cause the adjunct to transition from the first state to the second state. The cutting element can cut through at least a portion of the attachment feature as the cutting element moves. In further embodiments, actuation of the surgical stapler can cause staples to be deployed to thereby penetrate through at least a portion of the adjunct to cause the adjunct to transition from the first state to the second state. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       This invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of one embodiment of a surgical stapler; 
         FIG. 2  is an exploded view of a distal portion of the surgical stapler of  FIG. 1 ; 
         FIG. 3  is a perspective view of a firing bar of the surgical stapler of  FIG. 1 ; 
         FIG. 4  is a perspective view of another embodiment of a surgical stapler having a modular shaft; 
         FIG. 5  is a perspective view of an embodiment of a circular surgical stapler; 
         FIG. 6  is a partially exploded view of an end effector including a pair of opposed jaws and a cartridge; 
         FIG. 7  is a perspective view of another embodiment of an end effector having an anvil assembly coupled to a cartridge with an adjunct secured to the anvil assembly and an adjunct secured to the cartridge; 
         FIG. 8  is a cross-sectional view of one embodiment of an end effector having an adjunct material secured to a cartridge with a suture that extends around the cartridge; 
         FIG. 9A  is a perspective view of another embodiment of an end effector having an anvil assembly coupled to a cartridge with an adjunct secured to an anvil plate of the anvil assembly and an adjunct secured to the cartridge using at least one suture; 
         FIG. 9B  is a top perspective view of a portion of the anvil plate of  FIG. 9A  showing suture attachment points along the top surface of the anvil plate; 
         FIG. 9C  is a bottom perspective view of a portion of the cartridge of  FIG. 9A  showing the suture attachment points along the underside of the cartridge; 
         FIG. 10A  is a perspective view of a portion of a cartridge having suture attachment points on opposed sides of the cartridge according to another embodiment; 
         FIG. 10B  is a perspective view of the portion of the cartridge of  FIG. 10A  showing a pan coupled to the cartridge and positioned over the suture attachment points; 
         FIG. 11  is a cross-sectional view of an anvil plate having anvil surface features that mate with upper jaw cavities along an upper jaw member of an end effector according to yet another embodiment; 
         FIG. 12A  is an exploded view of one embodiment of a frame configured to couple to an adjunct material and a jaw; 
         FIG. 12B  is a perspective top view of the frame coupled to the jaw of  FIG. 12A ; 
         FIG. 13A  is an exploded view of another embodiment of a frame configured to couple to a jaw and an adjunct material; 
         FIG. 13B  is a perspective top view of the frame coupled to the jaw of  FIG. 13A , with the adjunct material coupled to a tissue-facing surface of the frame; 
         FIG. 13C  is a cross section view of the frame coupled to the jaw of  FIG. 13B , with the frame having a plurality of retaining features that secure the adjunct material to the tissue-facing surface of the frame; 
         FIG. 13D  is a cross section view of the frame coupled to the jaw of  FIG. 13B ; 
         FIG. 13E  is an exploded view of the frame of  FIG. 13A  and the jaw showing an outward facing surface of the jaw having attachment arm features; 
         FIG. 14A  is a perspective view of yet another embodiment of a frame configured as an overlay extending around a jaw with a tissue facing surface of the overlay having two rows of retaining features; 
         FIG. 14B  is a cross-sectional view of a portion of an end effector of  FIG. 14A  showing a first overlay coupled to the jaw and a second overlay coupled to another jaw with a first and second adjunct material, respectively, releasably coupled thereon; 
         FIG. 14C  is a perspective view of an applicator member configured to apply the first and second adjunct materials to the first and second overlays of  FIG. 14B ; 
         FIG. 15  is a perspective, partial cutaway view of one embodiment of a cartridge having an adjunct releasably retained thereon via a retainer; 
         FIG. 16  is a perspective, partial cutaway view of a portion of the cartridge and retainer of  FIG. 15 ; 
         FIG. 17  is a side view of a portion of the cartridge, retainer, and adjunct of  FIG. 15 ; 
         FIG. 18  is another side view of a portion of the cartridge, retainer, and adjunct of  FIG. 15 ; 
         FIG. 19  is a perspective, partial cutaway view of another embodiment of a cartridge having an adjunct releasably retained thereon via a retainer; 
         FIG. 20  is a perspective, partial cutaway view of yet another embodiment of a cartridge having an adjunct releasably retained thereon via a retainer; 
         FIG. 21  is another perspective, partial cutaway view of the cartridge, retainer, and adjunct of  FIG. 20 ; 
         FIG. 22  is a side view of a portion of the cartridge and retainer of  FIG. 20 ; 
         FIG. 23  is a perspective, partial cutaway view of another embodiment of a cartridge having an adjunct releasably retained thereon; 
         FIG. 24  is a side view of a portion of the cartridge and adjunct of  FIG. 23  pre-assembly; 
         FIG. 25  is a side view of the portion of the assembled cartridge and adjunct of  FIG. 24 ; 
         FIG. 26  is a perspective view of an embodiment of an anvil and a retainer coupled thereto; 
         FIG. 27  is an exploded view of the anvil and retainer of  FIG. 26 ; 
         FIG. 28  is a perspective view of a retaining element of the retainer of  FIG. 27 ; 
         FIG. 29  is a perspective view of another embodiment of an anvil and a retainer coupled thereto; 
         FIG. 30  is an exploded view of the anvil and retainer of  FIG. 29 ; 
         FIG. 31  is a top view of a lower jaw member of a surgical stapler showing a portion of an adjunct disposed thereon; 
         FIG. 32  is a perspective view of a single staple driver with an adjunct releasing mechanism; 
         FIG. 33  is a perspective view of a double staple driver with an adjunct releasing mechanism; 
         FIG. 34  is a cross-sectional side view of another embodiment of a portion of a lower jaw member of a surgical stapler with an adjunct releasing mechanism; 
         FIG. 35  is a perspective view of one embodiment of an end effector in accordance with the described techniques; 
         FIG. 36  is a perspective view of the cartridge body of the end effector of  FIG. 35 ; 
         FIG. 37  is another perspective view of the cartridge body of the end effector of  FIG. 35 ; 
         FIG. 38  is a perspective view of the adjunct material releasably retained on at least one jaw of the end effector of  FIG. 35 ; 
         FIG. 39  is a top view of the end effector of  FIG. 35 , showing the jaws of the end effector in a closed position; 
         FIG. 40  is a perspective view of another embodiment of an end effector in accordance with the described techniques; 
         FIG. 41  is a top view of the adjunct material releasably retained on the anvil of the end effector of  FIG. 40 ; 
         FIG. 42  is a top view of the adjunct material releasably retained on the cartridge of the end effector of  FIG. 40 ; 
         FIG. 43  is a perspective, partially cut-away view of one embodiment of an anvil of an end effector in accordance with the described techniques; and 
         FIG. 44  is a side view of a portion of the anvil of  FIG. 43 . 
         FIG. 45  is a perspective view of a jaw of an end effector that has an adjunct material releasably secured thereto; 
         FIG. 46A  is a perspective view an adjunct that has contractible attachment features disposed on a jaw of an end effector before the adjunct is coupled to the jaw; 
         FIG. 46B  is a perspective view of the adjunct of  FIG. 47A , illustrating the adjunct coupled to the jaw by application of heat; 
         FIG. 47A  is another perspective view an adjunct that has contractible attachment features disposed on a jaw of an end effector before the adjunct is coupled to the jaw; 
         FIG. 47B  is a perspective view of the adjunct of  FIG. 48A , illustrating the adjunct coupled to the jaw by application of heat; 
         FIG. 48A  is a top view of one embodiment of a loader; 
         FIG. 48B  is a cross-sectional view of the loader of  FIG. 49A ; 
         FIG. 49A  is a perspective view of a jaw and an adjunct configured to be releasably coupled to the jaw; 
         FIG. 49B  is a perspective view of the jaw of  FIG. 50A , illustrating the adjunct releasably coupled to the jaw; 
         FIG. 50  is an exploded view of a jaw of an end effector and at least partially stretchable adjunct material configured to be releasably coupled to the jaw; 
         FIG. 51  is a schematic view of the adjunct material of  FIG. 51 , illustrating areas of the adjunct material configured to have non-stretchable portions; 
         FIG. 52A  is a cross-sectional view of a jaw of an end effector and at least partially stretchable adjunct material to be releasably coupled to the jaw; 
         FIG. 52B  is a cross-sectional view of the jaw of  FIG. 53A , illustrating the adjunct material releasably coupled to the jaw; 
         FIG. 53A  is a cross-sectional view of jaws of an end effector and a loader prior to adjuncts being releasably coupled to the jaws; 
         FIG. 53B  is a cross-sectional view of the jaws and the loader of  FIG. 54A , illustrating the jaws and the loader while the adjuncts are being transferred from the loader to the jaws; 
         FIG. 53C  is a cross-sectional view of the jaws and the loader of  FIG. 54A , illustrating the jaws and the loader after the adjuncts have been transferred from the loader to the jaws and are releasably coupled to the jaws; 
         FIG. 54  is a perspective view of one embodiment of an adjunct coupled to an end effector jaw by suction; 
         FIG. 55A  is a cross-sectional view of the end effector jaw and adjunct of  FIG. 54  showing the adjunct prior to contact with a tissue contacting surface of the jaw; 
         FIG. 55B  is a cross-sectional view of the end effector jaw and adjunct of  FIG. 55A  showing the adjunct attached to the tissue contacting surface of the jaw by suction; 
         FIG. 55C  is a cross-sectional view of the end effector jaw and adjunct of  FIG. 55A  showing the adjunct punctured by staples; 
         FIG. 56A  is a perspective view of another embodiment of an adjunct coupled to an end effector jaw by suction; 
         FIG. 56B  is a perspective disassembled view of a portion of the adjunct of  FIG. 56A ; 
         FIG. 57A  is a cross-sectional view of the end effector jaw of  FIG. 56A  showing the adjunct prior to contact with a tissue contacting surface of the jaw; 
         FIG. 57B  is a cross-sectional view of the end effector jaw and adjunct of  FIG. 57A  showing the adjunct attached to the tissue contacting surface of the jaw by suction; 
         FIG. 57C  is a cross-sectional view of the end effector jaw and adjunct of  FIG. 57A  showing the adjunct punctured by staples; 
         FIG. 58  is a perspective disassembled view of a portion of an adjunct according to another embodiment; 
         FIG. 59  is a perspective, partial cut-away view of a jaw of an end effector having an adjunct material releasably mounted thereon in accordance with the described techniques; 
         FIG. 60  is a cross-sectional view of a portion of the jaw of  FIG. 59  with the adjunct material; 
         FIG. 61  is a perspective view of a distal portion of an end effector having an adjunct material releasably mounted thereon in accordance with the described techniques; 
         FIG. 62A  is a top view of a portion of an adjunct material having “non-retaining” female features used in accordance with the described techniques; 
         FIG. 62B  is a top view of “non-retaining” male features that can be formed on a jaw for mating with the adjunct material of  FIG. 62A , in accordance with the described techniques; 
         FIG. 62C  is a top view of the adjunct material of  FIG. 62A  having its “non-retaining” female features encompassing the “non-retaining” male features of  FIG. 62B ; 
         FIG. 63  is a perspective, partial cut-away view of an adjunct material having a backing layer in accordance with the described techniques; 
         FIG. 64  is a perspective, partial cut-away view of another adjunct material having a backing layer in accordance with the described techniques; 
         FIG. 65  is a perspective, partially exploded view of a distal portion of a jaw of an end effector and an adjunct material configured to be releasably mounted on the jaw in accordance with the described techniques; 
         FIG. 66  is a bottom view of the adjunct material of  FIG. 65 , illustrating the adjunct material when it is retained at a treatment site in a patient; 
         FIG. 67A  illustrates an example of an adjunct releasably retained to a tissue facing surface of a surgical stapler device; 
         FIG. 67B  illustrates a cross-sectional view of a tissue clamped between an upper jaw and a lower jaw of the surgical stapler device; 
         FIG. 67C  illustrates a perspective view of an embodiment of a distal end of a firing bar of the surgical stapler device; 
         FIG. 68A  is a side view of an embodiment of a jaw of an end effector, illustrating the jaw in a pre-fired configuration; 
         FIG. 68B  is a side view of the jaw of  FIG. 68A , illustrating the jaw in a fired configuration; 
         FIG. 69  illustrates a perspective view of an example of an adjunct removal system; 
         FIG. 70  illustrates a top-down view of a jaw of an end effector; 
         FIG. 71  illustrates a perspective, partially cut-away view of the jaw of the end effector of  FIG. 70 ; 
         FIG. 72  is a perspective view of one embodiment of an adjunct coupled to an end effector jaw by a hybrid attachment mechanism; 
         FIG. 73  is a cross-sectional view of the end effector jaw of  FIG. 1 , showing a portion of the adjunct of  FIG. 72  coupled thereto; 
         FIG. 74  is another cross-sectional view of the end effector jaw of  FIG. 1 , showing a portion of the adjunct of  FIG. 72  coupled thereto; 
         FIG. 75  is a perspective view of another embodiment of an adjunct coupled to an end effector jaw of  FIG. 1 ; 
         FIG. 76  is another perspective view of another embodiment of an adjunct coupled to an end effector jaw of  FIG. 1 ; 
         FIG. 77  is perspective, exploded view of a jaw of an end effector and an adjunct material configured to be coupled to the jaw via a polymer layer; 
         FIG. 78  is a cross-sectional view of a portion of the adjunct material of  FIG. 78  coupled to the jaw of the end effector via the polymer layer; 
         FIG. 79  is a top view of an adjunct loading member; 
         FIG. 80  is a cross-sectional view of the adjunct loading member of  FIG. 79 ; 
         FIG. 81A  is a cross-sectional view of an adjunct loading member configured to apply an adjunct material to first and second jaws of an end effector; 
         FIG. 81B  is a cross-sectional view of the adjunct loading member of  FIG. 81A , illustrating the adjunct material applied to the first and second jaws of the end effector; 
         FIG. 82  is a perspective view of an adjunct loading member; 
         FIG. 83A  is a cross-sectional view of a portion of an adjunct loading member configured to apply an adjunct material to a jaw of an end effector using a curable adhesive; 
         FIG. 83B  is a cross-sectional view of the adjunct loading member of  FIG. 83A , illustrating the adjunct loading member when load is applied thereto; 
         FIG. 83C  is a cross-sectional view of the adjunct loading member of  FIG. 83A , illustrating the adjunct loading member when load is applied thereto and the adhesive is being cured; 
         FIG. 84A  is a cross-sectional view of a portion of an adjunct loading member configured to apply an adjunct material to first and second jaws of an end effector using a curable adhesive; 
         FIG. 84B  is a cross-sectional view of the adjunct loading member of  FIG. 84A , illustrating the adjunct loading member when load is applied thereto; 
         FIG. 85  is a perspective view of an adjunct loading member; 
         FIG. 86A  is a cross-sectional view of a portion of an adjunct material releasably coupled to a first jaw of an end effector using an adhesive; 
         FIG. 86B  is a cross-sectional view of the adjunct material of  FIG. 86A , illustrating staples fired from a second jaw of the end effector and the end effector causing the adhesive to break; 
         FIG. 86C  is a cross-sectional view of the adjunct material of  FIG. 86A , illustrating the adjunct material separated from the end effector; 
         FIG. 87  is a perspective view of one embodiment of an adjunct loader for use with a surgical stapler; 
         FIG. 88  is a top view of the adjunct loader of  FIG. 87 ; 
         FIG. 89  is a cross-sectional side view of the adjunct loader of  FIG. 87 ; 
         FIG. 90  is a perspective view of another embodiment of an adjunct loader for use with a surgical stapler; 
         FIG. 91  is a top view of the adjunct loader of  FIG. 90 ; 
         FIG. 92  is a cross-sectional side view of the adjunct loader of  FIG. 90 ; 
         FIG. 93  is a cross-sectional side view of another embodiment of an adjunct loader for use with a surgical stapler; 
         FIG. 94  is a cross-sectional side view of the adjunct loader of  FIG. 93 ; 
         FIG. 95  is a cross-sectional side view of another embodiment of an adjunct loader for use with a surgical stapler; 
         FIG. 96  is a cross-sectional view of the adjunct loader of  FIG. 95 ; 
         FIG. 97  is a perspective view of a jaw of an end effector having an adjunct material releasably mounted thereon using an attachment feature in accordance with the described techniques; 
         FIG. 98  is a perspective partial view of the jaw with the adjunct material of  FIG. 97 ; 
         FIG. 99  is a perspective view of a side of the jaw of  FIG. 97  that is opposed to a tissue-contacting side thereof, illustrating end features of the attachment feature; 
         FIG. 100  is another perspective view of a jaw of an end effector having an adjunct material releasably mounted thereon using an attachment feature in accordance with the described techniques; 
         FIG. 101  is a schematic diagram illustrating an example of a roughness portion that can be formed on the jaw of  FIG. 97  and the jaw of  FIG. 100 ; 
         FIG. 102  is a perspective view of an upper side of a jaw of an end effector having an adjunct material releasably mounted thereon using a spindle-type attachment feature in accordance with the described techniques; 
         FIG. 103  is a perspective view of a jaw of an end effector configured to releasably retain thereon an adjunct material using an attachment feature in accordance with the described techniques; 
         FIG. 104  is a perspective, partially transparent view of the jaw of  FIG. 103 , illustrating the attachment feature releasably retaining the adjunct material on the jaw; 
         FIG. 105  is a perspective view of a jaw of an end effector configured to releasably retain thereon first and second adjunct materials; 
         FIG. 106  is a perspective view of the jaw of  FIG. 105 , illustrating the first and second adjunct materials releasably retained on the jaw; 
         FIG. 107  is another perspective view of a jaw of an end effector configured to releasably retain thereon first and second adjunct materials; 
         FIG. 108  is a perspective view of a portion of the first and second adjunct materials of  FIG. 16 , illustrating a tab in one of the adjunct materials engaging with a slot in another one of the adjunct materials; 
         FIG. 109  is a perspective view of a jaw of an end effector configured to releasably retain thereon an adjunct material; 
         FIG. 110A  is a schematic diagram illustrating a portion of the adjunct material of  FIG. 109 ; 
         FIG. 110B  is a schematic diagram illustrating the portion of the adjunct material of  FIG. 110A  in engagement with a portion of the jaw of  FIG. 109 ; 
         FIG. 111  is a perspective, partially exploded view of an end effector having an adjunct material releasably mounted thereon in accordance with the described techniques; 
         FIG. 112  is a partially exploded side view of the end effector of  FIG. 111 ; 
         FIG. 113A  is a cross-sectional view of a portion of the adjunct material and a polymer layer material of  FIG. 112 ; 
         FIG. 113B  is a cross-sectional view of a portion of the end effector of  FIG. 112  having the adjunct material with the polymer layer material releasably retained thereon; 
         FIG. 114  is a perspective view of an end effector having an adjunct material releasably mounted thereon in accordance with the described techniques; 
         FIG. 115  is a perspective view of an applicator member configured to apply the adjunct material to the end effector of  FIG. 114 ; 
         FIG. 116  is a cross-sectional view of a portion of the end effector of  FIG. 114  having the adjunct material releasably retained thereon; 
         FIG. 117  is a perspective, partially exploded view of an end effector having first and second adjunct materials releasably mounted thereon in accordance with the described techniques; 
         FIG. 118  is a perspective, partially exploded view of the end effector of  FIG. 117 , illustrating the first and second adjunct materials applied to a tissue in a patient; 
         FIG. 119  is a perspective view of an applicator member configured to apply the first and second adjunct materials to the end effector of  FIG. 117 ; 
         FIG. 120  is a perspective, schematic view of a jaw of an end effector having recesses formed thereon that are configured to mate with portions of an adjunct material in accordance with the described techniques; 
         FIG. 121  is a perspective, schematic view of the jaw of  FIG. 120  and of an applicator member configured to cause the portions of the adjunct material to be received in the recesses in the jaw; 
         FIG. 122  is a perspective, schematic view of the jaw of  FIG. 120 , illustrating the portions of the adjunct material received in the recesses in the jaw using the applicator member; 
         FIG. 123  is a perspective view of an end effector having an adjunct material releasably mounted thereon in accordance with the described techniques; 
         FIG. 124  is a cross-sectional view of a portion of the end effector of  FIG. 123  having the adjunct material releasably retained thereon; 
         FIG. 125  is a perspective view of an end effector having an adjunct material releasably mounted thereon in accordance with the described techniques; 
         FIG. 126  is a perspective view of an applicator member configured to apply the adjunct material to the end effector of  FIG. 125 ; 
         FIG. 127  is a cross-sectional view of a portion of the end effector of  FIG. 125  having the adjunct material releasably retained thereon; 
         FIG. 128A  is a perspective view of one embodiment of an applicator delivering a flowable adjunct precursor to a tissue; 
         FIG. 128B  is a perspective view of another embodiment of an applicator delivering a flowable adjunct precursor to a tissue; 
         FIG. 128C  is a perspective view of a mesh employed in combination with a flowable adjunct precursor delivered to a tissue; 
         FIG. 128D  is a perspective view of a stapler engaging tissue having an adjunct formed from any of the adjunct precursor of  FIGS. 128A-128C ; 
         FIG. 128E  is a perspective view illustrating the tissue and adjunct of  FIG. 128D  after delivery of a plurality of staples therethrough and the tissue is cut through the adjunct; 
         FIG. 129A  is an expanded perspective view of another embodiment of an adjunct and a portion of an end effector of an adjunct delivery device configured to deliver the adjunct to a tissue treatment site; 
         FIG. 129B  is a perspective view of a tissue after deposition of the adjunct thereon by the adjunct delivery device of  FIG. 129A ; 
         FIG. 130A  is a perspective view of one embodiment of a stapler engaging the tissue and adjunct of  FIG. 129B ; 
         FIG. 130B  is a perspective view of the tissue and adjunct of  FIG. 129B  after delivery of a plurality of staples therethrough; 
         FIG. 131A  is a perspective view of a tissue and an alternative embodiment of an adjunct including a plurality of lateral flanges configured to guide a stapler with respect to the adjunct; 
         FIG. 131B  is a perspective view of a stapler engaging the adjunct and the tissue of  FIG. 131A ; 
         FIG. 131C  is a perspective view the adjunct and tissue of  FIG. 8B  after delivery of the plurality of staples therethrough and the tissue is cut through the adjunct; 
         FIG. 132A  is an expanded perspective view of another embodiment of an adjunct system configured for use with a surgical stapler; and 
         FIG. 132B  is a perspective view of the adjunct system of  FIG. 132A  positioned on a tissue after delivery of a plurality of staples therethrough and the tissue is cut through the adjunct system. 
     
    
    
     DETAILED DESCRIPTION 
     Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those skilled in the art will understand that the devices, systems, and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention. 
     Further, in the present disclosure, like-named components of the embodiments generally have similar features, and thus within a particular embodiment each feature of each like-named component is not necessarily fully elaborated upon. Additionally, to the extent that linear or circular dimensions are used in the description of the disclosed systems, devices, and methods, such dimensions are not intended to limit the types of shapes that can be used in conjunction with such systems, devices, and methods. A person skilled in the art will recognize that an equivalent to such linear and circular dimensions can easily be determined for any geometric shape. Sizes and shapes of the systems and devices, and the components thereof, can depend at least on the anatomy of the subject in which the systems and devices will be used, the size and shape of components with which the systems and devices will be used, and the methods and procedures in which the systems and devices will be used. 
     It can be desirable to use one or more biologic materials and/or synthetic materials, collectively referred to herein as “adjuncts” or “buttresses,” in conjunction with surgical instruments to help improve surgical procedures. While a variety of different surgical end effectors can benefit from the use of adjuncts, in some exemplary embodiments the instrument can be a surgical stapler. When used in conjunction with a surgical stapler, the adjunct(s) can be disposed between and/or on jaws of the stapler, incorporated into a staple cartridge disposed in the jaws, or otherwise placed in proximity to the staples. When staples are deployed, the adjunct(s) can remain at the treatment site with the staples, in turn providing a number of benefits. For example, the adjunct(s) may reinforce tissue at the treatment site, preventing tearing or ripping by the staples at the treatment site. Tissue reinforcement may be needed to keep the staples from tearing through the tissue if the tissue is diseased, is healing from another treatment such as irradiation, medications such as chemotherapy, or other tissue property altering situation. In some instances, the adjunct(s) may minimize tissue movement in and around the staple puncture sites that can occur from tissue deformation that occurs after stapling (e.g., lung inflation, gastrointestinal tract distension, etc.). It will be recognized by one skilled in the art that a staple puncture site may serve as a stress concentration and that the size of the hole created by the staple will grow when the tissue around it is placed under tension. Restricting the tissues movement around these puncture sites can minimize the size the holes may grow to under tension. In some instances, the adjunct(s) can be configured to wick or absorb beneficial fluids, e.g., sealants, blood, glues, that further promote healing, and in some instances, the adjunct(s) can be configured to degrade to form a gel, e.g., a sealant, that further promotes healing. In some instances, the adjunct(s) can be used to help seal holes formed by staples as they are implanted into tissue, blood vessels, and various other objects or body parts. The adjunct(s) may also affect tissue growth through the spacing, positioning and/or orientation of any fibers or strands associated with the adjunct(s). Furthermore, in some circumstances, an adjunct can be useful in distributing pressure applied by the staple thereby reducing the possibility of a staple pulling through a tissue (which can be friable) and failing to fasten the tissue as intended (so-called “cheese wiring”). Additionally, the adjunct can be at least partially stretchable and can thus allow at least partial natural motion of the tissue (e.g., expansion and contraction of lung tissue during breathing) In some embodiments, a staple line can be flexible as described, for example, in U.S. Pat. Pub. No. 2016/0089142 entitled “Method for Creating a Flexible Staple Line,” filed on Sep. 26, 2014, which is hereby incorporated by reference herein in its entirety. 
     Coupling an adjunct material to one or both jaws of an end effector can be tedious and time consuming for a user, which can undesirably prolong surgical procedures. Furthermore, surgical procedures can be prolonged when more than one adjunct material is applied to a jaw, such as for consecutive stapling with an adjunct material. As such, various adjunct frame embodiments are described herein that are configured to releasably attach an adjunct material thereto and to efficiently couple to a jaw of an end effector of a surgical instrument. The adjunct frames can thus provide an efficient way to couple an adjunct material to a jaw. The adjunct frames are also configured to release the adjunct material when desired, such as after the adjunct material has been cut by a knife of the end effector and/or after firing of staples by the end effector. The adjunct frames can release the adjunct material while maintaining coupling between the adjunct frame and the respective jaw. This can ensure that the frame is not left at the surgical site, which would require additional procedure time to retrieve the frame and could result in complications. Instead, the user can retract the end effector with the adjunct frame still attached, thereby allowing the user to reload the adjunct frame with another adjunct material or decouple the adjunct frame from the jaw. 
     Surgical Stapling Instruments 
     A variety of surgical instruments can be used in conjunction with the adjunct(s) and/or medicant(s) disclosed herein. “Adjuncts” are also referred to herein as “adjunct materials.” The surgical instruments can include surgical staplers. A variety of surgical staplers can be used, for example linear surgical staplers and circular staplers. In general, a linear stapler can be configured to create longitudinal staple lines and can include elongate jaws with a cartridge coupled thereto containing longitudinal staple rows. The elongate jaws can include a knife or other cutting element capable of creating a cut between the staple rows along tissue held within the jaws. In general, a circular stapler can be configured to create annular staple lines and can include circular jaws with a cartridge containing annular staple rows. The circular jaws can include a knife or other cutting element capable of creating a cut inside of the rows of staples to define an opening through tissue held within the jaws. The staplers can be used in a variety of tissues in a variety of different surgical procedures, for example in thoracic surgery or in gastric surgery. 
       FIG. 1  illustrates one example of a linear surgical stapler  10  suitable for use with one or more adjunct(s) and/or medicant(s). The stapler  10  generally includes a handle assembly  12 , a shaft  14  extending distally from a distal end  12   d  of the handle assembly  12 , and an end effector  30  at a distal end  14   d  of the shaft  14 . The end effector  30  has opposed lower and upper jaws  32 ,  34 , although other types of end effectors can be used with the shaft  14 , handle assembly  12 , and components associated with the same. As shown in  FIG. 2 , the lower jaw  32  has a staple channel  56  (see  FIG. 2 ) configured to support a staple cartridge  40 , and the upper jaw  34  has an anvil surface  33  that faces the lower jaw  32  and that is configured to operate as an anvil to help deploy staples of the staple cartridge  40  (the staples are obscured in  FIGS. 1 and 2 ). At least one of the opposed lower and upper jaws  32 ,  34  is moveable relative to the other lower and upper jaws  32 ,  34  to clamp tissue and/or other objects disposed therebetween. In some implementations, one of the opposed lower and upper jaws  32 ,  34  may be fixed or otherwise immovable. In some implementations, both of the opposed lower and upper jaws  32 ,  34  may be movable. 
     Components of a firing system can be configured to pass through at least a portion of the end effector  30  to eject the staples into the clamped tissue. In various implementations a knife blade  36  (see  FIG. 3 ) or other cutting element can be associated with the firing system to cut tissue during the stapling procedure. The cutting element can be configured to cut tissue at least partially simultaneously with the staples being ejected. In some circumstances, it may be advantageous if the tissue is cut after the staples have been ejected and the tissue is secured. Thus, if a surgical procedure requires that a tissue captured between the jaws be severed, the knife blade  36  is advanced to sever the tissue grasped between the jaws after the staples have been ejected from the staple cartridge  40 . 
     Operation of the end effector  30  can begin with input from a user, e.g., a clinician, a surgeon, etc., at the handle assembly  12 . The handle assembly  12  can have many different configurations designed to manipulate and operate the end effector  30  associated therewith. In the illustrated example, the handle assembly  12  has a pistol-grip type housing  18  with a variety of mechanical and/or electrical components disposed therein to operate various features of the instrument  10 . For example, the handle assembly  12  can include a rotation knob  26  mounted adjacent the distal end  12   d  thereof which can facilitate rotation of the shaft  14  and/or the end effector  30  with respect to the handle assembly  12  about a longitudinal axis L of the shaft  14 . The handle assembly  12  can further include clamping components as part of a clamping system actuated by a clamping trigger  22  and firing components as part of the firing system that are actuated by a firing trigger  24 . The clamping and firing triggers  22 ,  24  can be biased to an open position with respect to a stationary handle  20 , for instance by a torsion spring. Movement of the clamping trigger  22  toward the stationary handle  20  can actuate the clamping system, described below, which can cause the jaws  32 ,  34  to collapse towards each other and to thereby clamp tissue therebetween. Movement of the firing trigger  24  can actuate the firing system, described below, which can cause the ejection of staples from the staple cartridge  40  disposed therein and/or the advancement the knife blade  36  to sever tissue captured between the jaws  32 ,  34 . A person skilled in the art will recognize that various configurations of components for a firing system, mechanical, hydraulic, pneumatic, electromechanical, robotic, or otherwise, can be used to eject staples and/or cut tissue. 
     As shown in  FIG. 2 , the end effector  30  of the illustrated implementation has the lower jaw  32  that serves as a cartridge assembly or carrier and the opposed upper jaw  34  that serves as an anvil. The staple cartridge  40 , having a plurality of staples therein, is supported in a staple tray  37 , which in turn is supported within a cartridge channel of the lower jaw  32 . The upper jaw  34  has a plurality of staple forming pockets (not shown), each of which is positioned above a corresponding staple from the plurality of staples contained within the staple cartridge  40 . The upper jaw  34  can be connected to the lower jaw  32  in a variety of ways, although in the illustrated implementation the upper jaw  34  has a proximal pivoting end  34   p  that is pivotally received within a proximal end  56   p  of the staple channel  56 , just distal to its engagement to the shaft  14 . When the upper jaw  34  is pivoted downwardly, the upper jaw  34  moves the anvil surface  33  and the staple forming pockets formed thereon move toward the opposing staple cartridge  40 . 
     Various clamping components can be used to effect opening and closing of the jaws  32 ,  34  to selectively clamp tissue therebetween. As illustrated, the pivoting end  34   p  of the upper jaw  34  includes a closure feature  34   c  distal to its pivotal attachment with the staple channel  56 . Thus, a closure tube  46 , whose distal end includes a horseshoe aperture  46   a  that engages the closure feature  34   c , selectively imparts an opening motion to the upper jaw  34  during proximal longitudinal motion and a closing motion to the upper jaw  34  during distal longitudinal motion of the closure tube  46  in response to the clamping trigger  22 . As mentioned above, in various implementations, the opening and closure of the end effector  30  may be effected by relative motion of the lower jaw  32  with respect to the upper jaw  34 , relative motion of the upper jaw  34  with respect to the lower jaw  32 , or by motion of both jaws  32 ,  34  with respect to one another. 
     The firing components of the illustrated implementation includes a firing bar  35 , as shown in  FIG. 3 , having an E-beam  38  on a distal end thereof. The firing bar  35  is encompassed within the shaft  14 , for example in a longitudinal firing bar slot  14   s  of the shaft  14 , and guided by a firing motion from the handle  12 . Actuation of the firing trigger  24  can affect distal motion of the E-beam  38  through at least a portion of the end effector  30  to thereby cause the firing of staples contained within the staple cartridge  40 . As illustrated, guides  39  projecting from a distal end of the E-Beam  38  can engage a wedge sled  47 , shown in  FIG. 2 , which in turn can push staple drivers  48  upwardly through staple cavities  41  formed in the staple cartridge  40 . Upward movement of the staple drivers  48  applies an upward force on each of the plurality of staples within the cartridge  40  to thereby push the staples upwardly against the anvil surface  33  of the upper jaw  34  and create formed staples. 
     In addition to causing the firing of staples, the E-beam  38  can be configured to facilitate closure of the jaws  32 ,  34 , spacing of the upper jaw  34  from the staple cartridge  40 , and/or severing of tissue captured between the jaws  32 ,  34 . In particular, a pair of top pins and a pair of bottom pins can engage one or both of the upper and lower jaws  32 ,  34  to compress the jaws  32 ,  34  toward one another as the firing bar  35  advances through the end effector  30 . Simultaneously, the knife  36  extending between the top and bottom pins can be configured to sever tissue captured between the jaws  32 ,  34 . 
     In use, the surgical stapler  10  can be disposed in a cannula or port and disposed at a surgical site. A tissue to be cut and stapled can be placed between the jaws  32 ,  34  of the surgical stapler  10 . Features of the stapler  10  can be maneuvered as desired by the user to achieve a desired location of the jaws  32 ,  34  at the surgical site and the tissue with respect to the jaws  32 ,  34 . After appropriate positioning has been achieved, the clamping trigger  22  can be pulled toward the stationary handle  20  to actuate the clamping system. The clamping trigger  22  can cause components of the clamping system to operate such that the closure tube  46  advances distally through at least a portion of the shaft  14  to cause at least one of the jaws  32 ,  34  to collapse towards the other to clamp the tissue disposed therebetween. Thereafter, the firing trigger  24  can be pulled toward the stationary handle  20  to cause components of the firing system to operate such that the firing bar  35  and/or the E-beam  38  are advanced distally through at least a portion of the end effector  30  to effect the firing of staples and optionally to sever the tissue captured between the jaws  32 ,  34 . 
     Another example of a surgical instrument in the form of a linear surgical stapler  50  is illustrated in  FIG. 4 . The stapler  50  can generally be configured and used similar to the stapler  10  of  FIG. 1 . Similar to the surgical instrument  10  of  FIG. 1 , the surgical instrument  50  includes a handle assembly  52  with a shaft  54  extending distally therefrom and having an end effector  60  on a distal end thereof for treating tissue. Upper and lower jaws  64 ,  62  of the end effector  60  can be configured to capture tissue therebetween, staple the tissue by firing of staples from a cartridge  66  disposed in the lower jaw  62 , and/or to create an incision in the tissue. In this implementation, an attachment portion  67  on a proximal end of the shaft  54  can be configured to allow for removable attachment of the shaft  54  and the end effector  60  to the handle assembly  52 . In particular, mating features  68  of the attachment portion  67  can mate to complementary mating features  71  of the handle assembly  52 . The mating features  68 ,  71  can be configured to couple together via, e.g., a snap fit coupling, a bayonet type coupling, etc., although any number of complementary mating features and any type of coupling can be used to removably couple the shaft  54  to the handle assembly  52 . Although the entire shaft  54  of the illustrated implementation is configured to be detachable from the handle assembly  52 , in some implementations, the attachment portion  67  can be configured to allow for detachment of only a distal portion of the shaft  54 . Detachable coupling of the shaft  54  and/or the end effector  60  can allow for selective attachment of a desired end effector  60  for a particular procedure, and/or for reuse of the handle assembly  52  for multiple different procedures. 
     The handle assembly  52  can have one or more features thereon to manipulate and operate the end effector  60 . By way of non-limiting example, a rotation knob  72  mounted on a distal end of the handle assembly  52  can facilitate rotation of the shaft  54  and/or the end effector  60  with respect to the handle assembly  52 . The handle assembly  52  can include clamping components as part of a clamping system actuated by a movable trigger  74  and firing components as part of a firing system that can also be actuated by the trigger  74 . Thus, in some implementations, movement of the trigger  74  toward a stationary handle  70  through a first range of motion can actuate clamping components to cause the opposed jaws  62 ,  64  to approximate toward one another to a closed position. In some implementations, only one of the opposed jaws  62 ,  24  can move to move the jaws  62 ,  64  to the closed position. Further movement of the trigger  74  toward the stationary handle  70  through a second range of motion can actuate firing components to cause the ejection of the staples from the staple cartridge  66  and/or the advancement of a knife or other cutting element (not shown) to sever tissue captured between the jaws  62 ,  64 . 
     One example of a surgical instrument in the form of a circular surgical stapler  80  is illustrated in  FIG. 5 . The stapler  80  can generally be configured and used similar to the linear staplers  10 ,  50  of  FIGS. 1 and 4 , but with some features accommodating its functionality as a circular stapler. Similar to the surgical instruments  10 ,  50 , the surgical instrument  80  includes a handle assembly  82  with a shaft  84  extending distally therefrom and having an end effector  90  on a distal end thereof for treating tissue. The end effector  90  can include a cartridge assembly  92  and an anvil  94 , each having a tissue-contacting surface that is substantially circular in shape. The cartridge assembly  92  and the anvil  94  can be coupled together via a shaft  98  extending from the anvil  94  to the handle assembly  82  of the stapler  80 , and manipulating an actuator  85  on the handle assembly  82  can retract and advance the shaft  98  to move the anvil  94  relative to the cartridge assembly  92 . The anvil  94  and cartridge assembly  92  can perform various functions and can be configured to capture tissue therebetween, staple the tissue by firing of staples from a cartridge  96  of the cartridge assembly  92  and/or can create an incision in the tissue. In general, the cartridge assembly  92  can house a cartridge containing the staples and can deploy staples against the anvil  94  to form a circular pattern of staples, e.g., staple around a circumference of a tubular body organ. 
     In one implementation, the shaft  98  can be formed of first and second portions (not shown) configured to releasably couple together to allow the anvil  94  to be detached from the cartridge assembly  92 , which may allow greater flexibility in positioning the anvil  94  and the cartridge assembly  92  in a body of a patient. For example, the first portion of the shaft  98  can be disposed within the cartridge assembly  92  and extend distally outside of the cartridge assembly  92 , terminating in a distal mating feature. The second portion of the shaft  98  can be disposed within the anvil  94  and extend proximally outside of the cartridge assembly  92 , terminating in a proximal mating feature. In use, the proximal and distal mating features can be coupled together to allow the anvil  94  and cartridge assembly  92  to move relative to one another. 
     The handle assembly  82  of the stapler  80  can have various actuators disposed thereon that can control movement of the stapler. For example, the handle assembly  82  can have a rotation knob  86  disposed thereon to facilitate positioning of the end effector  90  via rotation, and/or the trigger  85  for actuation of the end effector  90 . Movement of the trigger  85  toward a stationary handle  87  through a first range of motion can actuate components of a clamping system to approximate the jaws, i.e. move the anvil  94  toward the cartridge assembly  92 . Movement of the trigger  85  toward the stationary handle  87  through a second range of motion can actuate components of a firing system to cause the staples to deploy from the staple cartridge assembly  92  and/or cause advancement of a knife to sever tissue captured between the cartridge assembly  92  and the anvil  94 . 
     The illustrated examples of surgical stapling instruments  10 ,  50 ,  80  provide only a few examples of many different configurations, and associated methods of use, that can be used in conjunction with the disclosures provided herein. Although the illustrated examples are all configured for use in minimally invasive procedures, it will be appreciated that instruments configured for use in open surgical procedures, e.g., open linear staplers as described in U.S. Pat. No. 8,317,070 entitled “Surgical Stapling Devices That Produce Formed Staples Having Different Lengths” and filed Feb. 28, 2007, can be used in conjunction with the disclosures provided herein. Greater detail on the illustrated examples, as well as additional examples of surgical staplers, components thereof, and their related methods of use, are provided in U.S. Pat. Pub. No. 2015/0277471 entitled “Systems And Methods For Controlling A Segmented Circuit” and filed Mar. 26, 2014, U.S. Pat. Pub. No. 2013/0256377 entitled “Layer Comprising Deployable Attachment Members” and filed Feb. 8, 2013, U.S. Pat. No. 8,393,514 entitled “Selectively Orientable Implantable Fastener Cartridge” and filed Sep. 30, 2010, U.S. Pat. No. 8,317,070 entitled “Surgical Stapling Devices That Produce Formed Staples Having Different Lengths” and filed Feb. 28, 2007, U.S. Pat. No. 7,143,925 entitled “Surgical Instrument Incorporating EAP Blocking Lockout Mechanism” and filed Jun. 21, 2005, U.S. Pat. Pub. No. 2015/0134077 entitled “Sealing Materials For Use In Surgical Stapling” and filed Nov. 8, 2013, entitled “Sealing Materials for Use in Surgical Procedures, and filed on Nov. 8, 2013, U.S. Pat. Pub. No. 2015/0134076, entitled “Hybrid Adjunct Materials for Use in Surgical Stapling,” and filed on Nov. 8, 2013, U.S. Pat. Pub. No. 2015/0133996, entitled “Positively Charged Implantable Materials and Method of Forming the Same,” and filed on Nov. 8, 2013, U.S. Pat. Pub. No. 2015/0129634, entitled “Tissue Ingrowth Materials and Method of Using the Same,” and filed on Nov. 8, 2013, U.S. Pat. Pub. No. 2015/0133995, entitled “Hybrid Adjunct Materials for Use in Surgical Stapling,” and filed on Nov. 8, 2013, U.S. Pat. Pub. No. 2015/0272575, entitled “Surgical Instrument Comprising a Sensor System,” and filed on Mar. 26, 2014, and U.S. Pat. Pub. No. 2015/0351758, entitled “Adjunct Materials and Methods of Using Same in Surgical Methods for Tissue Sealing,” and filed on Jun. 10, 2014, which are hereby incorporated by reference herein in their entireties. 
     Implantable Adjuncts 
     As indicated above, various implantable adjuncts are provided for use in conjunction with surgical stapling instruments. The adjuncts can have a variety of configurations, and can be formed from various materials. In general, an adjunct can be formed from one or more of a film, a foam, an injection molded thermoplastic, a vacuum thermoformed material, a fibrous structure, and hybrids thereof. The adjunct can also include one or more biologically-derived materials and one or more drugs. Each of these materials is discussed in more detail below. 
     An adjunct can be formed from a foam, such as a closed-cell foam, an open-cell foam, or a sponge. An example of how such an adjunct can be fabricated is from animal derived collagen, such as porcine tendon, that can then be processed and lyophilized into a foam structure. Gelatin can also be used and processed into a foam. Examples of various foam adjuncts are further described in previously mentioned U.S. Pat. No. 8,393,514 entitled “Selectively Orientable Implantable Fastener Cartridge” and filed Sep. 30, 2010. 
     An adjunct can also be formed from a film formed from any suitable material or combination thereof discussed below. The film can include one or more layers, each of which can have different degradation rates. Furthermore, the film can have various regions formed therein, for example, reservoirs that can releasably retain therein one or more medicants in a number of different forms. The reservoirs having at least one medicant disposed therein can be sealed using one or more different coating layers which can include absorbable or non-absorbable polymers. The film can be formed in various ways. For example, it can be an extruded or a compression molded film. The medicants can also be absorbed onto the film or bound to the film via non-covalent interactions such as hydrogen bonding. 
     An adjunct can also be formed from injection molded thermoplastic or a vacuum thermoformed material. Examples of various molded adjuncts are further described in U.S. Pat. Pub. No. 2013/0221065 entitled “Fastener Cartridge Comprising A Releasably Attached Tissue Thickness Compensator” and filed Feb. 8, 2013, which is hereby incorporated by reference in its entirety. The adjunct can also be a fiber-based lattice which can be a woven fabric, knitted fabric or non-woven fabric such as a melt-blown, needle-punched or thermal-constructed loose woven fabric. An adjunct can have multiple regions that can be formed from the same type of lattice or from different types of lattices that can together form the adjunct in a number of different ways. For example, the fibers can be woven, braided, knitted, or otherwise interconnected so as to form a regular or irregular structure. The fibers can be interconnected such that the resulting adjunct is relatively loose. Alternatively, the adjunct can include tightly interconnected fibers. The adjunct can be in a form of a sheet, tube, spiral, or any other structure that can include compliant portions and/or more rigid, reinforcement portions. The adjunct can be configured such that certain regions thereof can have more dense fibers while others have less dense fibers. The fiber density can vary in different directions along one or more dimensions of the adjunct, based on an intended application of the adjunct. 
     The adjunct can be formed from woven, knitted, or otherwise interconnected fibers, which allows the adjunct to be stretched. For example, the adjunct can be configured to stretch in a direction along its longitudinal axis and/or in a lateral direction that is perpendicular to the longitudinal axis. While being stretchable in at least two dimensions (e.g., X and Y directions), the adjunct can provide reinforcement along its thickness (e.g., a Z direction) such that it stretches but resists tearing and pull-through by the staples. Non-limiting examples of adjuncts that are configured to be implanted such that they can stretch with the tissue are described in the above-mentioned U.S. Pat. Pub. No. 2016/0089142 entitled “Method for Creating a Flexible Staple Line,” filed on Sep. 26, 2014, which is hereby incorporated by reference herein in its entirety. 
     The adjunct can also be a hybrid construct, such as a laminate composite or melt-locked interconnected fiber. Examples of various hybrid construct adjuncts are further described in U.S. Pat. No. 9,282,962 entitled “Adhesive Film Laminate” and filed Feb. 8, 2013, and in U.S. Pat. No. 7,601,118 entitled “Minimally Invasive Medical Implant And Insertion Device And Method For Using The Same” and filed Sep. 12, 2007, which are hereby incorporated by reference in their entireties. 
     The adjuncts in accordance with the described techniques can be formed from various materials. The materials can be used in various embodiments for different purposes. The materials can be selected in accordance with a desired therapy to be delivered to tissue so as to facilitate tissue in-growth. The materials can include bioabsorbable and biocompatible polymers, including homopolymers and copolymers. Bioabsorbable polymers can be absorbable, resorbable, bioresorbable, or biodegradable polymers. 
     An adjunct can also include active agents, such as active cell culture (e.g., diced autologous tissue, agents used for stem cell therapy (e.g., Biosutures and Cellerix S.L.), hemostatic agents, and tissue healing agents. 
     The adjuncts can releasably retain therein at least one medicant that can be selected from a large number of different medicants. Medicants include, but are not limited to, drugs or other agents included within, or associated with, the adjunct that have a desired functionality. The medicants include, but are not limited to, for example, antimicrobial agents such as antibacterial and antibiotic agents, antifungal agents, antiviral agents, anti-inflammatory agents, growth factors, analgesics, anesthetics, tissue matrix degeneration inhibitors, anti-cancer agents, hemostatic agents, and other agents that elicit a biological response. The adjuncts can also be made from or include agents that enhance visibility during imaging, such as, for example, echogenic materials or radio-opaque materials. 
     Examples of various adjuncts and various techniques for releasing medicants from adjuncts are further described in U.S. patent application Ser. No. 14/840,613 entitled “Medicant Eluting Adjuncts and Methods of Using Medicant Eluting Adjuncts” and filed Aug. 31, 2015, which is hereby incorporated by reference in its entirety. 
     Surgical End Effector Adjunct Attachment 
     Various exemplary devices, systems and methods for releasably retaining an adjunct material on an end effector of a surgical instrument are described herein. In a typical surgical stapler end effector, the anvil has a preconfigured set of staple pockets formed therein and configured to receive and form staples fired from the cartridge. As a result, the end effector can only be used with staple cartridges having staple cavities that align with the anvil. Accordingly, in an exemplary embodiment, various anvil plates are provided having varying staple pocket configurations for use with different staple cartridges. The anvil plate can mate to the upper jaw of an end effector, and a cartridge designed for use with that particular anvil plate can be inserted into the lower jaw of the end effector. As such, the end effector can create a variety of staple configurations by switching out the anvil assembly and/or cartridge. Furthermore, adjunct materials can be releasably secured to either the cartridge or anvil plate using one or more restraining elements. For example, the adjunct materials can be pre-attached to the anvil plate and/or the cartridge (e.g., during manufacturing) and can be released from the anvil plate and/or cartridge during firing of the end effector (e.g., advancing a knife along the end effector to fire staples and cut tissue, adjunct material, and any restraining elements), as will be described in greater detail below. 
       FIG. 6  illustrates one embodiment of an end effector  1100  including upper and lower jaws  1102 ,  1104 , respectively, that can pivot between open and closed configurations. As shown in  FIG. 6 , a staple cartridge  1106  can be configured to releasably couple to the lower jaw member  1104 , and can include staple cavities  1108  having staples disposed therein. The upper jaw  1102  can be in the form of an anvil having staple pockets  1103  formed therein and configured to receive and form staples fired from the cartridge  1106 . Both the upper jaw  1102  and cartridge  1106  can include knife slots  1124 , 1110 , respectively, configured to allow a knife to advance therealong. 
     As shown in  FIG. 6 , an anvil assembly  1120  can be configured to releasably couple to an inward tissue-facing surface  1107  of the cartridge  1106  and/or an inward-facing surface  1103  of the upper jaw  1102 . The anvil assembly  1120  can include an anvil plate  1128  having a rectangular shape that can extend along either the upper jaw  1102  or cartridge  1106 . The anvil plate  1128  can include an anvil adapter  1126  along an outward-facing surface of the anvil plate  1128 . The anvil adapter  1126  can include plate features configured to mate with jaw features along the inward-facing surface  1103  of the upper jaw  1102  (see, for example,  FIG. 11 ) thereby assisting with securing the alignment between the anvil plate  1128  and the upper jaw  1102 . The anvil plate  1128  can further include staple pockets  1130  (shown as imprints along an outward-facing surface of the anvil plate  1128 ) that are recessed along an inward tissue-facing surface  1129  of the anvil plate  1128 . The staple pockets  1130  can be arranged along the anvil plate  1128  such that each staple pocket  1130  corresponds to a staple cavity  1108  of the cartridge  1106  for assisting with forming the staples (e.g., stapling tissue together and/or adjunct to tissue). The anvil plate  1128  can include a knife channel  1132  that extends longitudinally along the anvil plate  1128  and that is configured to allow a knife to advance therealong. 
     In some embodiments, the anvil plate  1128  can include one or more alignment features  1134  that can assist with maintaining alignment between the anvil plate  1128  and the upper jaw  1102 . For example, as shown in  FIG. 6 , the anvil plate  1128  can include proximal and distal alignment features  1134  that extend upward from the outward-facing surface of the anvil plate  1128  toward the upper jaw  1102 . The alignment features  1134  can be configured as tabs that mate with one or more recesses, slots, through-holes, etc., in the upper jaw  1102 . Depending on the configuration of the upper jaw  1102 , the alignment features  1134  may slide longitudinally within the recesses, slots, through holes, etc., of the upper jaw  1102  as the jaw members move between the open and closed positions thus maintaining alignment between the anvil plate  1128  and the upper jaw  1102  during opening and closing of the jaws. Additionally, the alignment features  1134  can function to maintain alignment between the anvil plate  1128  and the cartridge  1106 . Proper alignment between the anvil plate  1128  and the cartridge  1106  ensures that staples contact staple pockets  1130 , and form properly, when fired from the cartridge  1106 . 
     As shown in  FIG. 6 , the anvil assembly  1120  can also include one or more attachment features  1138  for coupling the anvil plate  1128  to the cartridge  1106 , such as to the inward tissue-facing surface  1107  of the cartridge  1106 . In some embodiments, as shown in  FIG. 6 , the attachment features  1138  can include at least one bracket. The bracket can extend between the anvil plate  1128  and cartridge  1106  and can allow the anvil plate  1128  to pivot (e.g., along with the upper jaw) between an open and closed configuration relative to the cartridge  1106 . In some embodiments, the attachment features  1138  can function as a hinge and biasing element that biases the anvil plate  1128  to the open configuration thereby allowing the anvil plate  1128  to pivot and follow the upper jaw  1102  when the jaws open. 
     The attachment features  1138  of the anvil assembly  1120 , and the inward tissue-facing surface  1107  of the cartridge  1106 , can include coupling features  1140 ,  1112 , respectively. The coupling features  1140 ,  1112  can be in the form of through-holes that enable, for example, pins  1142 , rivets, or similar features, to extend therethrough and connect the coupling features  1140  of the anvil assembly  1120  to the coupling features  1112  on the cartridge  1106 . This configuration allows the anvil plate  1128  and cartridge  1106  to be releasably coupled together thereby allowing the end effector to provide various stapling configurations by switching out either the cartridge  1106  or anvil plate  1128 . As such, the replaceable cartridge  1106  and anvil assembly  1120  can provide an advantage over end effectors that are, for example, limited to the configuration of the staple pockets in the anvil. 
     Furthermore, it can be desirable for an end effector to include features and/or components that facilitate releasable attachment of an adjunct to the end effector. For example, an adjunct can be attached, including pre-attached during manufacturing or prior to a surgical procedure, to the end effector using a restraining element, such as a suture. In one embodiment, the suture can be elongated and made out of, for example, a thermoplastic such as polydioxanone (PDS), an elastic material, and/or any other biocompatible material suitable for securing the adjunct to the end effector. In some embodiments, the restraining element can be continuous or non-continuous with opposing ends of the restraining element anchored to a part of the anvil assembly and/or cartridge. When the stapler is fired, staples can fire through the tissue and adjunct toward the anvil to be formed. A knife can travel through knife channels in the cartridge, anvil plate, and upper jaw thereby cutting the restraining element and releasing the adjunct from the end effector to allow the adjunct to remain at the surgical site. 
       FIG. 7  illustrates an anvil assembly  1220  releasably coupled to a cartridge  1206  with a first adjunct material  1244  coupled to an inward tissue-facing surface of an anvil plate  1228  of an anvil assembly  1220 , and a second adjunct material  1246  coupled to an inward tissue-facing surface of the cartridge  1206 . The first and second adjuncts  1244 ,  1246  can each be secured to the anvil assembly  1220  and cartridge  1206 , respectively, using one or more restraining elements or sutures  1248 . Each suture  1248  can extend around the first adjunct  1244  and anvil plate  1228  or around the second adjunct  1246  and cartridge  1206 , thereby securing the first or second adjuncts  1244 ,  1246  to the respective anvil plate  1228  or cartridge  1206 . 
     As shown in  FIG. 7 , the cartridge  1206  and/or a cartridge pan  1214  (coupled to the cartridge  1206 ) can include one or more cartridge notches  1256 , and the anvil plate  1228  of the anvil assembly  1220  can include one or more anvil notches  1266 . For example, the notches  1256 ,  1266  can be shaped as curved recesses and can be configured to allow a part of the suture  1248  to sit therein for maintaining a position of the suture  1248  relative to either the anvil plate  1228  or cartridge  1206 . The notches  1256 ,  1266  can thus assist with preventing the suture  1248  from slipping and unsecuring a position of either the first or second adjunct  1244 ,  1246  relative to the anvil plate or cartridge, respectively. 
     For example, the first adjunct  1244  can be secured to an inward tissue-facing surface of the anvil plate  1228  by a pair of sutures  1248  (e.g., one suture  1248  positioned adjacent at a distal end of the anvil plate  1228  and one suture  1248  positioned adjacent a proximal end of the anvil plate  1228 ) that wrap around the first adjunct  1244  and anvil plate  1228 . As shown in  FIG. 7 , portions of the proximally and distally positioned sutures  1248  can be positioned in anvil notches  1266  along a side of the anvil plate  1228 . The notches  1266  can prevent the sutures  1248  from shifting or slipping longitudinally along the anvil plate  1228 , thereby ensuring that the sutures  1248  secure the first adjunct to the anvil plate  1228 . 
     Similarly, the second adjunct  1246  can be secured to an inward tissue-facing surface of the cartridge  1206  by a pair of sutures  1248  (e.g., one suture  1248  positioned adjacent a distal end of the cartridge  1206  and one suture  1248  positioned adjacent a proximal end of the cartridge  1206 ) that wrap around the second adjunct  1246  and cartridge  1206 . As shown in  FIG. 7 , portions of the proximally and distally positioned sutures  1248  can be positioned in cartridge notches  1256  along a side of the cartridge  1206  and/or cartridge pan  1214 . The cartridge notches  1256  can prevent the sutures  1248  from shifting or slipping longitudinally along the cartridge  1206  thereby ensuring that the sutures  1248  secure the second adjunct  1246  to the cartridge  1206 . 
     As shown in  FIG. 7 , the first adjunct  1244  can include first adjunct notches  1262  along opposing sides of the first adjunct  1244 , and the second adjunct  1246  can include second adjunct notches  1263  along opposing sides of the second adjunct  1246 . The first and second adjuncts  1244 ,  1246  can be made of the same material, or they can be made of different materials. The first adjunct notches  1262  can be positioned along the first adjunct  1244  such that first adjunct notches  1262  align with the anvil notches  1266  when the first adjunct  1244  is properly aligned with the anvil plate  1228  (e.g., the adjunct surface area of the first adjunct covers the inward tissue-facing surface of the anvil plate  1228 ). As such, when the suture  1248  extends around the first adjunct  1244  and anvil plate  1228  and along the first adjunct notches  1262  and anvil notches  1266 , the suture  1248  secures a desired positioning between the first adjunct  1244  and the anvil plate  1228 . Similarly, the second adjunct notches  1263  can be positioned along the second adjunct  1246  such that the second adjunct notches  1263  align with the cartridge notches  1256  when the second adjunct  1246  is properly aligned with the cartridge  1206  (e.g., the second adjunct surface area of the second adjunct covers the inward tissue-facing surface of the cartridge  1206 ). As such, when the suture  1248  extends around the second adjunct  1246  and cartridge  1206  and along the second adjunct notches  1263  and cartridge notches  1256 , the suture  1248  secures a desired positioning between the second adjunct  1246  and the cartridge  1206 . Each of the sutures  1248  can be made of the same material, or one or more of the sutures  1248  can be made of a different material. 
     Although the cartridge notches  1256 , anvil notches  1266 , and first and second adjunct notches  1262 ,  1263  are shown as U-shaped cutouts, any one of the cartridge notches  1256 , anvil notches  1266 , and first and second adjunct notches  1262 ,  1263  can have any number of shapes and/or sizes that allow a part of suture to extend therealong for securing the suture in position relative to either the anvil plate  1228  or cartridge  1206 . For example, any one of the cartridge notches  1256 , anvil notches  1266 , and first and second adjunct notches  1262 ,  1263  can be V-shaped, squared, or any other geometry. Furthermore, any number of notches (e.g., cartridge notches  1256 , anvil notches  1266 , and first and second adjunct notches  1262 ,  1263 ) and lengths of suture  1248  can be used to secure the position of either the first or second adjuncts  1244 ,  1246 . Alternatively, rather than notches  1256 ,  1266 , the cartridge  1206 , cartridge pan  1214 , and/or the anvil plate  1228 , can include holes through which sutures  1248  can be threaded. Similarly, the adjuncts  1244 ,  1246  can include holes that align with holes on the cartridge  1206 , cartridge pan  1214 , and/or anvil plate  1228 . Sutures can be threaded through the holes in the adjuncts  1244 ,  1246  and through the holes in the cartridge  1206 , cartridge pan  1214 , and/or the anvil plate  1228 , to retain the adjuncts  1244 ,  1246  on inward tissue-facing surfaces of the cartridge  1206  and the anvil plate  1228 . 
     In some embodiments, it can be desirable to angle a suture extending around the adjunct material and cartridge to ensure that the adjunct is detached from the cartridge after at least one staple has been deployed (e.g., thereby securing the adjunct to the tissue). 
       FIG. 8  illustrates upper and lower jaws  1302 ,  1304  in a closed configuration, clamped around tissue  1346 , with an adjunct  1344  secured to an inward tissue-facing surface of a cartridge  1306  that is seated within the lower jaw  1304 . As shown in  FIG. 8 , the adjunct  1344  is secured to the cartridge  1306  using a suture  1348  that extends around the adjunct  1344  and cartridge  1306  at an angle (la). For example, the suture  1348  can extend along the adjunct  1344  at a location proximal to the location at which the suture  1348  extends around the back side of the cartridge  1306 . As such, as shown in  FIG. 8 , a side view of the suture  1348  extending around the adjunct  1344  and cartridge  1306  shows the suture  1348  extending at an angle (la) across the side of the cartridge  1306 . As illustrated in  FIG. 8 , a knife  1338  can be configured to advance along the cartridge  1306  to cut the tissue  1346 , suture,  1348 , and adjunct  1344 , using a knife blade  1336 . The knife  1338  can also be configured to drive staples  1347  from the cartridge  1306  as it advances along the cartridge  1306 . As the knife advances along the length of the cartridge  1306 , it can push a wedge sled  1340 , which can push staple drivers  1342  that hold staples  1347  in a tissue-facing direction to form the staples  1347 . The angling of the suture  1348  can ensure that the suture  1348  is in a position to be cut without being stapled to the tissue  1346 . The angled suture  1348  can be positioned such that the knife blade  1336  is the first part of the knife  1338  that contacts the suture  348  in order to cause the angled suture  1348  to be cut approximately upon contact with the knife  1338 . 
     Alternatively or in addition to using continuous restraining elements, such as continuous sutures or lengths of suture that couple end to end, one or more non-continuous restraining elements that anchor opposing ends of the restraining elements to components of the cartridge and/or anvil assembly can be used. 
       FIGS. 9A-9C  illustrate another embodiment of an anvil assembly  1420  releasably coupled to a cartridge  1406  with a cartridge pan  1414  coupled to a bottom side of the cartridge  1406 . As shown in  FIGS. 9A-9C , a first adjunct material  1444  can be coupled to an inward tissue-facing surface of the anvil plate  1428  of the anvil assembly  1420  and a second adjunct material  1446  can be coupled to an inward-tissue facing surface of the cartridge  1406 . The first and second adjuncts  1444  and  1446  can be secured to the anvil assembly  1420  and cartridge  1406  with one or more sutures  1448 . Furthermore, the anvil assembly  1420  and/or cartridge  1406  can include one or more suture attachment sites  1456  that are configured to couple a part (e.g., opposing ends) of the suture  1448  thereto. As shown in  FIGS. 9B and 9C , at least one pair of attachments sites  1456  can be positioned along an outward-facing surface of the anvil plate  1428  of the anvil assembly  1420  (as shown in  FIGS. 9A and 9B ), and another pair of attachment sites  1456  can be positioned along an outward-facing surface of the cartridge  1406  and/or an outward-facing surface of the cartridge pan  1414  (as shown in  FIG. 9C ). 
     The suture  1448 , and more particularly each of the opposing ends of the suture  1448 , can be heat staked, welded, or otherwise adhered to the attachment sites  1456 . In some implementations, the attachment site  1456  can include a texture that assists with securing the suture  1448  to the attachment site. For example, the attachment site  1456  can be roughened or otherwise made to include a textured surface. The cartridge  1406  and/or anvil assembly  1420  can include one or more attachment site  1456 , and each attachment site  1456  can include any of a variety of sized and shaped surface areas. For example, the attachment sites  1456  can have various shapes, such as circular, triangular, or any other shaped surface area. Additionally, some attachment sites  1456  can be coated with a material that improves the attachment of the suture  1448 . Alternatively or in addition, small posts, barbs or hooks can be used at the attachment sites  1456  to secure the suture  1448  in place. Although two sutures  1448  and two pairs of attachment sites  1456  are used to secure each adjunct  1444 ,  1446  in  FIGS. 9A-9C , any number of sutures and attachment sites can be used to secure the adjuncts to the anvil plate and/or cartridge. 
       FIGS. 10A-10B  illustrate another embodiment of a suture  1548  extending across a second adjunct  1546  for securing the second adjunct  1546  to a cartridge  1506 . As shown in  FIG. 10A , opposed ends of the suture can be secured to attachment sites  1556  positioned along opposed sides of the cartridge  1506 . More than one suture  1548  can be secured across the second adjunct and secured to attachment sites  1556  positioned on opposed sides of the cartridge  1506  or lower jaw  1514 . Similarly, opposed ends of suture can be secured to attachment sites positioned along opposed sides of the anvil plate or other part of the anvil assembly. 
     Additionally or alternatively, as shown in  FIG. 10B , a pan  1516  can be releasably coupled to the cartridge  1506  such that an inner surface of the pan  1516  can provide a compressive force against the ends of the suture  1548 , thereby further securing the coupling between the ends of the suture  1548  and the attachment sites  1556 . The pan  1516  can also protect the ends of the suture  1548  from being dislodged from the cartridge  1506  as the cartridge  1506  is inserted into a channel of a lower jaw of an end effector. Various other components can be coupled to either the cartridge and/or anvil plate for providing additional securing forces at the point of attachment between the suture and attachment sites, which are within the scope of the is disclosure. 
       FIG. 11  illustrates anvil features  1670  that can extend from an outward-facing surface  1671  of the anvil plate  1628  and that are configured to mate with jaw features  1672  (e.g., cavities) that extend into an inward-facing surface  1673  of the upper jaw  1602 . The anvil features  1670  can have a similar shape as the jaw features  1672  such that, when mated, the outward-facing surface of the anvil plate  1628  can be restricted from sliding against the inward-facing surface of the upper jaw  1602 , thereby assisting with maintaining a preferred alignment between the anvil plate  1628  and the upper jaw  1602 . The anvil features  1670  and/or jaw features  1672  can include stamped metal and/or elastomer and can have any number of a variety of shapes and sizes. Furthermore, it is within the scope of this disclosure for the cartridge and/or lower jaw to include features that mate with corresponding features along the lower jaw for assisting with maintaining a desired position of the cartridge relative to the lower jaw. 
     Surgical End Effector Adjunct Attachment 
     Various exemplary devices, systems and methods are provided for releasably retaining a frame with an adjunct to a jaw of an end effector of a surgical instrument. In certain exemplary embodiments, the frame can include retaining features for coupling an adjunct to a tissue-facing surface of the frame, thereby releasably coupling the adjunct material to the jaw of the end effector. In some implementations, the frame can include a plurality of retaining features that are configured to engage the adjunct material thereby creating a tension in the adjunct material, which can further assist with securing the frame to the jaw. The frame can also include various attachment features (e.g., attachment arms) that are configured to assist with releasably coupling the frame to the jaw. 
     In other embodiments, a removable applicator can be member provided for retaining at least one adjunct material and for aligning and coupling the adjunct material to a frame that is already secured to the jaw. Thus, in some implementations the jaws can be manipulated to engage the adjunct material retained by the applicator member, thereby mounting the adjunct onto the end effector. In particular, a force applied to the applicator member can cause the applicator member to release the at least one adjunct material and to transfer the at least one adjunct material to at least one respective frame secured to a jaw of the end effector. 
       FIGS. 12A and 12B  illustrate one exemplary embodiment of a frame  2100  that is configured to releasably couple to an upper jaw  2102  of an end effector and to releasably retain an adjunct material (not shown) on a tissue-facing surface  2105  of the frame  2100 . As shown, the frame  2100  can be in the form of an elongated body  2106  having an outward facing surface  2108  that can mate to and extend along an anvil surface  2103  of an anvil of the upper jaw  2102 . One or more pairs of attachment arms  2110  can extend from the elongated body  2106 , with each pair of attachment arms  2110  extending from opposing sides of the elongated body  2106  and arching towards a longitudinal axis of the elongated body  2106 . The attachment arms  2110  can have a shape that is similar to an outer profile of the outward facing surface of the upper jaw  2102 , thereby allowing the attachment arms to extend around a part of the outward facing surface of the upper jaw  2102  for securing the frame  2110  to the upper jaw  2102 . Although the frame  2110  is shown and described as being configured for releasably securing to the upper jaw  2102 , the frame  2100  can be configured for releasably securing to the upper jaw and/or lower jaw without departing from the scope of this disclosure. 
     Some embodiments of the attachment arms  2110  can be made out of a compliant and or elastic material that allows the attachment arms  2110  to deform or spread apart. The compliant and/or elastic attachment arms  2110  can assist with coupling the frame  2100  to the upper jaw  2102 , as well as provide a compressive force against the outward facing surface of the upper jaw  2102  thereby securing the attachment and position of the frame  2100  to the upper jaw  2102 . For example, the frame  2100  can be coupled to the upper jaw  2102  by guiding a distal end of the upper jaw  2102  through a space created by the attachment arms  2110  and/or spreading the attachment arms  2110  to allow the upper jaw  2102  to be positioned within the arcs of the attachment arms  2110 . 
     The frame  2100  can be made out of one or more of a variety of materials, including compliant and/or elastic materials. For example, the frame can be made out of any number of materials (e.g., surgical grade), such as metals and polymers, without departing the scope of this disclosure. 
     In some embodiments, the upper jaw  2102  and/or frame  2100  can include a locking mechanism that assists with releasably securing the frame  2100  to the upper jaw  2102 . For example, the upper jaw  2102  can include a locking feature at a proximal end that interacts and locks the frame  2100  to the upper jaw  2102  when the frame  2100  is loaded onto the upper jaw  2102 . Furthermore, the upper jaw  2102  and/or frame  2100  can include a release feature (e.g., shown as a tab  2107  in  FIG. 12B ) that is configured to force or allow the release of the frame  2100  from the upper jaw  2102  when acted upon (e.g., pushed or pivoted). 
     As discussed above, the tissue facing surface  2105  of the frame  2100  can be configured to releasably secure an adjunct material thereto for allowing the adjunct material to be stapled to tissue and to remain at a surgical site. The frame  2100  can be configured such that the adjunct material can be secured to the frame  2100 , however, the adjunct material can also be uncoupled from the frame  2100  thereby allowing the adjunct material, and not the frame  2100 , to remain at the surgical site. Various attachment techniques can be utilized to mate an adjunct to the frame, such as an adhesive, fasteners, or any other chemical or mechanical attachment techniques. 
       FIGS. 13A-13E  illustrate another embodiment of a frame  2200  that can be releasably coupled to a jaw of an end effector, such as an upper jaw  2202 . The frame  2200  can be configured to releasably retain an adjunct material  2220  to thereby releasably secure the adjunct material  2220  to the upper jaw  2202 . Similar to the embodiment above, the frame  2200  can be coupled to either the upper and/or lower jaw without departing from the scope of this disclosure. As shown in  FIGS. 13B-13E , the frame  2200  can include attachment arms  2210  that extend from an elongated body  2206  of the frame  2200  and that can be shaped to conform to an outward facing surface of the upper jaw  2202 . As such, the attachment arms  2210  can assist with securing the position of the frame  2200  and adjunct  2220  relative to the upper jaw  2202 , such as before and during firing of staples. 
     As shown, the tissue facing surface  2205  of the frame  2200  can include a plurality of retaining features  2222  positioned along the length of the elongated body  2206 . The plurality of retaining features  2222  can be configured to releasably secure the adjunct material  2220  to the frame  2200  such that the adjunct material  2220  can remain securely coupled to the frame  2200  at least until firing of a knife along the end effector thereby cutting the adjunct material  2220 . The retaining features  2222  can be shaped and engaged with the adjunct material  2220  such that they allow the adjunct material  2220  to release attachment from the frame  2200  after the adjunct material  2220  has been cut and as the end effector moves away from the surgical site after firing of the staples. The frame  2200  can remain coupled to the end effector, such as the upper jaw, as the adjunct is released. A user can subsequently decouple the frame  2200  from the jaw or load another adjunct material  2220  onto the frame  2200 . As such, the frame  2200  is configured such that the adjunct material  2220  is allowed to remain at the surgical site and the frame  2200  remains attached to the end effector so that the frame  2200  is not left at the surgical site and can either be reused or disposed of. 
     As shown in  FIG. 13A , the frame  2200  can include at least one slot or opening  2226  that extends along a length of the elongate body  2206 . Each opening  2226  can be configured to allow staples to pass therethrough and into the adjunct and tissue engaged between the jaws, thereby stapling the adjunct material  2220  to adjacent tissue. The openings  2226  can be shaped such that they surround the staple cavities of the cartridge and/or staple forming cavities of the anvil surface thereby allowing the firing of the staples without the frame  2200  interfering or getting stapled to tissue. 
     The frame  2200  can also include a hinge  2230  along a length of the elongate body  2206  that allows the elongate body  2206  to apply tension to the adjunct. As shown in  FIG. 13A , the hinge  2230  can extend along a longitudinal axis of the elongated body  2206  and can include a V-shaped profile. The V-shaped hinge  2230  can be configured to extend a distance within a knife slot  2211  of the upper jaw  2202  when the frame is coupled to the upper jaw, as shown in  FIGS. 13C-13D . This can allow a knife to advance along the knife slot  2211  and cut the adjunct material  2220  without interference from the frame  2200 . In an exemplary embodiment, however, the hinge  2230  can be formed from a material that can be cut by the knife as it is advanced through the knife slot  2211 . Cutting of the hinge  2230  can assist with releasing the adjunct from the frame  2200 , as will be discussed in more detail below. 
       FIGS. 13C-13D  illustrate the frame  2200  coupled to the upper jaw, with the hinge  2230  extending into the knife slot  2211 . The adjunct material  2220  is also shown coupled to a plurality of retaining features  2222 . The retaining features  2222  can be made out of a rigid, semi-rigid, or flexible material and can include a hook or securing feature  2223  that extends outward away from the longitudinal axis of the elongate body  2206 . This configuration of the retaining features  2222  can allow a first side of the adjunct material  2220  to be secured to a plurality of retaining features  2222  positioned on a first side of the hinge  2230 . The adjunct material  2220  can then be pulled so that it is under tension before securing a second side of the adjunct material  2220  to the retaining features  2222  positioned on a second side of the hinge  2230 , as shown in  FIG. 13C . The retaining features  2222  on the first side of the hinge  2230  can thus pull in an opposite direction from the retaining features  2222  on the second side of the hinge  2230  thereby placing the adjunct material under tension. The retaining features  2222  can also deform or bend when the adjunct material  2220  is under tension thereby further securing the adjunct material  2220  to the frame  2200 . Furthermore, having the retaining features engage the adjunct material  2220  under tension can pull opposing sides of the elongate body  2206  closer together thereby allowing the hinge  2230  to form a first angle  2232   a  and further securing the frame  2200  to the upper jaw  2202 . 
     As mentioned above, a knife can be advanced along the knife slot  2211  thereby cutting the adjunct material  2220  as well as cutting at least part of the hinge  2230 . By cutting the adjunct material  2220  positioned adjacent the knife slot  2211 , the tension in the adjunct material  2220  caused by the retaining features  2222  pulling on the adjunct material from opposing sides of the knife slot  2211  can be released. When this tension along the adjunct material  2220  is released, the retaining features  2222  can reform (e.g., straighten) thereby allowing the adjunct material  2220  to be pulled off of the frame, such as after being stapled. The opposing sides of the elongate body to  2205  can also move further apart when the tension along the adjunct material  2220  is released, which can allow the hinge  2230  to form a second angle  2232   b  (see  FIG. 13D ). The second angle  2232   b  can be larger than the first angle  2232   a  thereby allowing the opposing sides of the elongate body  2206  to move further apart from each other, such as for allowing a user to decouple the frame  2200  from the upper jaw  2202 . Similarly, if a part of the hinge  2230  is cut, the opposing sides of the elongate body  2206  can move further apart to allow a user to decouple the frame from the upper jaw  2202 . In some embodiments, the frame can include an adhesive and/or one or more features that can couple to a part of the knife slot to further assist in securing the frame to the upper jaw  2202 . 
       FIG. 13E  illustrates the outward facing surface  2221  of the upper jaw  2202  having attachment arm coupling features  2240  therealong that are configured to prevent attachment arms  2210  of the frame  2200  from moving relative to a length of the upper jaw  2202 , such as when the frame  2200  is coupled to the upper jaw  2202 . As shown, each attachment arm coupling feature  2240  can include a recess that has a shape and depth that allows an attachment arm  2210  to be seated therein to prevent the attachment arm  2210  from sliding out of the attachment arm coupling features  2240  and/or along the length of the upper jaw  2202 . For example, the attachment arm coupling feature  2240  can be in the form of a recessed band that extends at an arc perpendicular to the longitudinal axis of the upper jaw. 
     Because the attachment arm coupling features  2240  can prevent the frame  2200  from sliding along the upper jaw  2202  even during loading of the frame  2200  onto the upper jaw  2202 , the frame  2200  can be snapped on by deforming (e.g., elastically) the attachment arms  2210  to allow the upper jaw  2202  to fit within the confines of the attachment arms  2210 . The attachment arms can be aligned with the attachment arm coupling features  2240  such that each of the attachment arms  2210  can spring towards the outward facing surface and into a corresponding attachment arm coupling feature  2240 . Once coupled, the attachment arms  2210  and attachment arm coupling features  2240  can prevent the frame  2200  from sliding along the upper jaw  2202  thereby ensuring a desired positioning of the adjunct material  2220  relative to the upper jaw  2202 . 
     As mentioned above, the frames  22100 ,  2200  can be configured to mate to either the upper and/or lower jaws. In addition, a frame can be coupled or mounted to a jaw of an end effector prior to having an adjunct coupled to the frame. As such, a user may need to align and mount an adjunct material to the frame when the frame is coupled to the jaw. Some frames can be reusable such that more than one adjunct can be used with a single frame.  FIGS. 14A-14B  illustrate a reusable frame that can be coupled to either the upper or lower jaw of the end effector and, as shown in  FIG. 14C , an applicator member can be used to position and assist with mounting at least one adjunct material onto a respective frame coupled to either the upper or lower jaw. 
       FIG. 14A  illustrates an embodiment of a frame  2300  including an overlay  2350  that is configured to extend along a part of an upper jaw  2302 . In some embodiments, the overlay  2350  can include a flexible elongated tubular member that can slide over the upper jaw  2302  thereby covering an anvil surface  2303  of the upper jaw  2302 . In some embodiments, the overlay  2350  can include an elongated surface that can cover the anvil surface  2303  and can further include edges that wrap around one or more sides of the upper jaw to thereby secure the overlay to the upper jaw. The overlay  2350  can further include an adhesive material that can assist with securing the position of the overlay  2350  relative to the upper jaw  2302 . A tissue facing surface  2305  of the overlay  2350  can include at least one row of retaining features  2322  that are configured to assist with coupling an adjunct material  2320  thereto. For example, the tissue facing surface  2305  of the overlay  2350  can include two rows of retaining features  2322  with each row positioned along opposing sides of the anvil surface  2303  when the overlay  2350  is coupled to the upper jaw  2302 . 
       FIG. 14B  illustrates the upper and lower jaws  2302 ,  2304  each having an overlay  2350   a ,  2350   b  covering an outer surface thereof. As shown in  FIG. 14B , an adjunct material  2320  can be releasably mated to both of the upper and lower jaws  2302 ,  2304 . The adjunct material  2320  can include at least one row of complimentary retaining features  2325  that are configured to engage and releasably secure to at least one row of retaining features  2322  along the overlay  2350 . For example, the adjunct material  2320  can include two rows of complimentary retaining features  2325 , with each row positioned along opposing sides of the adjunct material  2320  such that they align with the two rows of retaining features  2322  along the overlay  2350 , as shown in  FIG. 14B . As such, the adjunct material  2320  can be coupled to an overlay  2350  by aligning the rows of retaining features  2322  along the overlay  2350  with the rows of complimentary retaining features  2325  along the adjunct material  2320 . Once aligned, the retaining features  2322  and complimentary retaining features  2325  can be engaged thereby releasably securing the adjunct material  2320  to the overlay  2350 . The engagement between the retaining features  2322  and complimentary retaining features  2325  can be strong enough to maintain the position of the adjunct material  2320  relative to the overlay  2350  prior to firing of staples, while allowing the adjunct material  2320  to uncouple and remain stapled at the surgical site after firing of the staples. The retaining features  2322  and/or complimentary retaining features  2325  can have various configurations, such as hook and loop members, various self-adhering materials, snap-fit features, etc. Furthermore, although the retaining features  2322  and complimentary retaining features  2325  are shown and described as being formed into rows along the overlay and adjunct material  2320 , respectively, the retaining features  2322  and complimentary retaining features  2325  can have any number of shapes and configurations. For example, positioning retaining features  2322  and complimentary retaining features  2325  along opposing sides of the anvil surface  2203  (when the overlay  2350  is coupled to the upper jaw) allows the retaining features  2322  and complimentary retaining features  2325  to not interfere with either the advancing of the knife and/or firing of staples, however, other configurations can also achieve this. 
     One or both of the adjunct materials  2320  can be releasably retained on the overlays  2350   a ,  2350   b  coupled to the upper and lower jaws  2302 ,  2304 , respectively, using an applicator member  2360  shown in  FIG. 14C . The applicator member  2360  can be in the form of a frame-like holder configured to releasably retain one or both of the adjunct materials  2320   a ,  2320   b . In the illustrated example, the applicator member  2360  is in the form of first (e.g., bottom) and second (e.g., top) generally rectangular housings  2324 ,  2326  coupled to one another as shown in  FIG. 14C . As also shown in  FIG. 14C , the first and second housing  2324 ,  2326  can engage edges of the long sides of the adjunct materials  2320   a ,  2320   b  therebetween. In other words, the applicator member  2360  can be in the shape of a generally U-shaped frame that surrounds an outer perimeter of at least two sides (e.g., long sides) of one or two adjunct materials. In particular, as shown in  FIG. 14C , the applicator member  2360  can expose the complimentary retaining features  2325  thereby allowing the complimentary retaining features  2325  to align with and couple to the retaining features  2322  along the overlay  2350 . It should be appreciated that the adjunct materials  2320   a ,  2320   b  and the first and second housings  2324 ,  2326  of the applicator member  2360  encompassing them can be symmetrical. Thus, either of the adjunct materials  2320   a ,  2320   b  can be applied to either overlay  2350   a ,  2350   b  coupled to the upper or lower jaw  2302 ,  2304 , respectively. 
     The applicator member  2360  can be formed from any suitable material (e.g., plastic), and its walls can be relatively thin and it can be disposable. In use, to transfer the adjunct materials  2320   a ,  2320   b  to the overlays  2350   a ,  2350   b , respectively, the upper or lower jaws  2302 ,  2304  can be clamped together into the opening in the applicator member  2360 , with the complimenting retaining features  2325  of the adjunct materials  2320   a ,  2320   b  aligned with the retaining features  2322  along the overlays  2350   a ,  2350   b . In this way, force applied by the jaws  2302 ,  2304  can cause the adjunct materials  2320   a ,  2320   b  to separate from the applicator member  2360  and to be engaged with the overlays  2350   a ,  2350   b . In particular, in this example, as force is applied to the applicator member  2360  by the jaws  2302 ,  2304  of the end effector, the complimentary retaining features  2325  of the adjunct materials  2320   a ,  2320   b  are securely coupled to the retaining features  2322  along the overlays  2350   a ,  2350   b.    
     After the adjunct materials  2320   a ,  2320   b  are transferred to the overlays positioned over the upper and lower jaws  2302 ,  2304 , the jaws can be opened and the applicator member  2360  can be separated from the end effector. The overlays  2350   a ,  2350   b  attached to the upper and lower jaws  2302 ,  2304  can thus be mated with their respective adjunct materials  2320   a ,  2320   b , as shown in  FIG. 14B , and can then be used as desired in a surgical procedure. 
     It should be appreciated that the applicator member  2360  is shown to releasably retain two adjunct materials  2320   a ,  2320   b  by way of example only, and the applicator member  2360  or a similar component configured to releasably hold at least one adjunct material  2320  can be used to transfer an adjunct material  2320  only to a single frame or overlay coupled to the end effector. Moreover, the applicator member can be used to attach one or more adjuncts to any of the frames and/or jaws disclosed herein. 
     Surgical Adjunct Retaining Mechanism 
     An adjunct can be releasably retained on an end effector of a surgical tool, such as a surgical stapler, using a plurality of retaining elements. The retaining elements can be configured to retain the adjunct to the end effector with a mechanical force until a force is applied to the adjunct that overcomes the mechanical force, thereby allowing release of the adjunct from the end effector and into a patient&#39;s body where it may provide any number of benefits, as discussed above. The force can be applied to the adjunct in the normal course of use of the surgical tool, such as in the course of deploying staples from the end effector, which may facilitate ease of use since a user need not take any special action to release the adjunct. The retaining elements can be configured to releasably retain the adjunct to the end effector without using an adhesive, which may make the system easier to assemble, may facilitate release of the adjunct from the end effector since adhesive may require application of a higher force to release an adjunct, and/or may prevent staple cavities or other components of a surgical tool from being clogged by or otherwise compromised in function by the adhesive. The retaining elements can be on a retainer releasably coupled to the end effector. Existing end effectors may be retrofitted with a retainer and/or existing staple cartridges may be coupled to the retainer. Existing end effectors that include a metal pan may have the pan modified to include the features of a retainer as described herein. 
       FIG. 15  illustrates one embodiment of a staple cartridge  3100  coupled to a retainer  3102  including a plurality of retaining elements  3104  configured to releasably retain an adjunct  3106  to the staple cartridge  3100 . The staple cartridge  3100  is generally configured and used similar to the staple cartridge  40  of  FIGS. 1 and 2 , e.g., has a plurality of staple cavities  3108  in a tissue-facing surface  3110  thereof that each seat a staple therein (the staples are obscured in  FIG. 15 ), is configured to have a sled moved therethrough to push the staples out of the staple cavities  3108 , has a longitudinal slot  3112  through which a knife or other cutting element can translate to cut tissue, etc. The staple cartridge  3100  is releasably seated in a lower jaw  3114  of an end effector of a surgical tool. The cartridge  3100  is seated in the retainer  3102 , which is seated in a channel in the lower jaw  3114 . The sled that translates along the cartridge  3100  can thus translate along an inner bottom surface of the retainer  3102 . The lower jaw  3114  includes a coupling mechanism  3116  that couples the lower jaw  3114  to an upper jaw of the end effector that is configured to cooperate with the lower jaw  3114  to engage and staple tissue, as discussed above. 
     The retainer  3102  in this illustrated embodiment is in the form of a pan or tray that has a bottom with opposed sidewalls extending upwardly therefrom. The cartridge  3100  is fixedly seated in the retainer  3102  in this illustrated embodiment, e.g., is not removable from the retainer  3102 . The cartridge  3100  and the retainer  3102  are thus configured to be removably and replaceably seated in the lower jaw  3114  as a unit. The cartridge  3100  being fixed to the retainer  3102  may help ensure that the retaining elements  3104  are in a desirable location relative to the cartridge  3100 , which may help the adjunct  3102  be desirably positioned over the cartridge&#39;s tissue-facing surface  3110  and/or may help ensure alignment of the retaining elements  3104  with cut-outs or pockets  3118  formed in the cartridge  3100 , which are also shown in  FIG. 16  and are discussed further below. In other embodiments, a cartridge can be releasably retained in a retainer, which may allow for re-use of the retainer with different staple cartridges. The retainer in such embodiments is configured to be seated in an end effector&#39;s lower jaw either before or after the cartridge is seated in the retainer. 
     The retainer  3102  can be formed from any of a variety of materials. In an exemplary embodiment, the retainer  3102  is formed from a metal, such as stainless steel, titanium, or a shape memory metal such as Nitinol. 
     The retaining elements  3104  are longitudinally aligned and are positioned along opposed longitudinal sides  3102   a ,  3102   b  of the retainer  3102 . The retaining elements  3104  are thus positioned along opposed longitudinal sides  3100   a ,  3100   b  of the cartridge  3100 . In an exemplary embodiments, a first number of the retaining elements  3104  are on one side  3102   a  (e.g., left side) of the retainer  3102  and a second number of the retaining elements  3104  are on the other side  3102   b  (e.g., right side) of the retainer  3102 . The first and second numbers of the retaining elements  3104  can be equal, as in this illustrated embodiment in which there are eleven retaining element  3104  on each side  3102   a ,  3102   b  of the retainer  3102  for a total or twenty-two retaining elements  3104 . Having an equal number of retaining elements  3104  on opposed sides  3102   a ,  3102   b  of the retainer  3102  may help provide even securing of the adjunct  3106  to the cartridge  3100 . However, the first and second numbers of the retaining elements  3104  can vary. In an exemplary embodiment there are at least three retaining elements  3104  on each side  3102   a ,  3102   b  of the retainer  3102 . For example, one retaining element  3104  can be near a proximal end thereof for releasable attachment to the adjunct  3100  near a proximal end thereof, one retaining element  3104  can be near a distal end thereof for releasable attachment to the adjunct  3100  near a distal end thereof, and one retaining element  3104  can be near a middle thereof for releasable attachment to the adjunct  3100  near a middle thereof. Any additional retaining elements  3104  can be located between the proximal retaining element and the middle retaining element and/or between the distal retaining element and the middle retaining element. Regardless of a number of retaining elements  3104  on each side  3102   a ,  3102   b  of the retainer  3102 , the retaining elements  3104  can be equidistantly spaced therealong, as in this illustrated embodiment, which may help evenly secure the adjunct  3106  to the cartridge  3100 . 
     The retaining elements  3104  extend upwardly from the retainer  3102 , e.g., in a direction toward the upper jaw (e.g., the anvil) coupled to the lower jaw  3114 . The retaining elements  3104  thus extend in a direction  3 D 1  substantially perpendicular to a longitudinal axis  3100 A of the cartridge  3100  and a longitudinal axis  3114 A of the lower jaw  3114 . The retaining elements  3104  extending upwardly may help prevent lateral movement of the adjunct  3106  engaged therewith relative to the cartridge  3100 , which may help ensure that all of the staples in the cartridge  3100  are deployed through the adjunct  3106 , e.g., that each of the staples pierces the adjunct  3106 , which may facilitate release the adjunct  3106  from the retaining elements  3104  and the cartridge  3100 . The retaining elements  3104  each extend a distance above the tissue-facing surface  3110  of the cartridge  3100 , which allows the adjunct  3106  engaged by the retaining elements  3104  to be seated on and be substantially flat on the tissue-facing surface  3110  of the cartridge  3100 . A person skilled in the art will appreciate that although the adjunct  3106  may not be precisely flat it can nevertheless be considered to be substantially flat due to any number of factors, such as flexibility of the adjunct material and/or manufacturing tolerance at the adjunct&#39;s surface. 
     Each of the retaining elements  3104  in this illustrated embodiment is in the form of a hook. Each of the hooks is angled or oriented in a same proximal direction. The hooks are thus angled or oriented in a direction that is opposite to the distal direction that the sled translates along the cartridge  3100  and lower jaw  3114 . As the sled translates distally along the cartridge  3100  and lower jaw  3114  to eject the staples, the upward movement of the staples out of the staple cavities  3108  exerts a force, e.g., an upward force in a direction of the upper jaw against which the staples are pushed, on the adjunct  3106 . The adjunct  3106  is thus urged upwardly away from the cartridge  3100 , which causes the adjunct  3106  to be released from the retaining elements  3104  by being pushed thereof. The retaining elements  3104  can experience deformation during the release of the adjunct  3106  therefrom in response to the upward force. In other words, the pushing of the adjunct  3106  off the retaining elements  3104  may cause the hooks to bend upwardly. The force exerted by the staples being ejected through the adjunct  3106  can thus be enough to overcome the mechanical force that the retaining elements  3104  exert to hold the adjunct  3106  thereto. In other embodiments, retaining elements in the form of hooks can each be angled or oriented in a same distal direction so as to be angled in the same direction that the sled translates along the cartridge and lower jaw. In this way, the sled&#39;s distal movement can help urge disengagement of the adjunct from the retaining elements as the sled travels in a distal direction to drive staples from the cartridge. The hooks in such an embodiment would be less likely to experience plastic deformation than hooks oriented proximally and may not deform at all. 
     The retaining elements  3104  on the retainer  3102  can be integrally formed with the retainer  3102 , as in this illustrated embodiment, such as with a stamping process. The retaining elements  3104  can thus also, in an exemplary embodiment, be formed from a metal. The retaining elements  3104  can be very thin, as in this illustrated embodiment, in which case the retaining elements  3104  will have some degree of flexibility even if formed from a rigid material such as metal. This flexibility can result in plastic deformation of the retaining elements  3104  during release of the adjunct  3106  therefrom, e.g., one or more of the retaining elements  3104  may be irreversibly bent during release of the adjunct  3106 , such as by being bent upwardly during staple deployment as discussed above. In other embodiments, instead of being integral with the retainer  3102 , the retaining elements  3104  can be separate members attached thereto, such as by welding, adhesive, press fit, etc. 
     In at least some embodiments, one or more of the retaining elements  3104  can include a gripping feature thereon configured to facilitate gripping of the adjunct  3106 . The gripping feature may help prevent premature release of the adjunct  3106  from the cartridge  3100 . For example, the gripping feature can be a textured surface on the retaining element  3104  that increases friction between the retaining element  3104  and the adjunct  3106 . For another example, the gripping feature can be an enlarged tip of the retaining element  3104 , such as a bulb or ball at the retaining element&#39;s tip, which may help prevent the adjunct  3106  from prematurely sliding off the retaining element  3104  since passing over the enlarged tip will be made more difficult, e.g., require a higher force to be released therefrom. 
     The cartridge  3100  has a plurality of cut-outs or pockets  3118  formed therein. The cut-outs  3118  are longitudinally aligned and are positioned along the opposed longitudinal sides  3100   a ,  3100   b  of the cartridge  3100 . The cut-outs  3118  are aligned with the retaining elements  3114  such that each of the cut-outs  3118  has an associated retaining element  3114 . The cut-outs  3118  are each configured to seat a portion of the adjunct  3106  therein, as shown in  FIG. 15 , when the retaining elements  3104  are holding the adjunct  3106  on the cartridge  3100 . The cut-outs  3118  may thus help prevent buckling of the adjunct  3106 , which may allow the staples to more evenly advance through the adjunct  3106 . The cut-outs  3118  each have a square shape in this illustrated embodiment but can have other shapes, e.g., rectangular, semi-circular, etc. 
     The adjunct  3106  in this illustrated embodiment is a fibrous structure that includes a plurality of fibers. As shown in  FIGS. 15 and 17 , the retaining elements  3104  can extend through the adjunct  3106  so as to hook the adjunct  3106  thereto. The fibers can separate to allow the retaining elements  3104  to extend therethrough at points  3105  where the adjunct  3106  engages the retaining elements  3104 , although depending on various factors such as the tightness of the fiber&#39;s lattice structure, whether the retaining element&#39;s tips are blunted or pointed (the tips are blunted in this illustrated embodiment), and the strength of the retaining elements  3104 , the retaining elements  3104  can pierce through the fibrous structure so as to form holes therein at any one or more of the points  3105 . The retaining elements  3104  pierce through the adjunct  3106  in this illustrated embodiment. The adjunct  3106  may have pre-formed holes therein at locations where the retaining elements  3104  will extend through the adjunct  3106 , which may help the retaining elements  3104  all pass through the adjunct  3106  both during loading of the adjunct  3106  onto the retaining elements  3104  and during release of the adjunct  3106  from the retaining elements  3104 . 
     In some embodiments, the adjunct  3106  can be releasably coupled to the retaining elements  3104  in manufacturing such that the cartridge  3100 , retainer  3102 , and adjunct  3106  can be provided to a user as an assembled unit. Providing such an assembled unit may save user time since the assembly is pre-performed and/or may help ensure that the adjunct  3106  is properly secured to the cartridge  3100  and retainer  3102 . In other embodiments, the adjunct  3106  can be provided to a user as a separate element from the retainer  3102  and cartridge  3100 , which as mentioned above may be separate elements or may be fixed together as a unit. The adjunct  3106  in such embodiments can thus be configured to be coupled to the retainer  3102  and cartridge  3100  by a user. The adjunct  3106  can be coupled to the retainer  3102  and cartridge  3100  in any of a variety of ways. For example, the adjunct  3106  can be manually engaged with the retaining elements  3104  by being pressed or slid thereon by hand. For another example, an applicator tool can be configured to have the adjunct  3106  loaded thereon, and the applicator tool can be configured to engage the adjunct  3106  with the retaining elements  3104  by sliding or pressing the adjunct  3106  thereon. Use of the applicator tool may allow for more predictable engagement of the adjunct  3106  with the retaining elements  3104  than application by hand. 
       FIG. 18  illustrates another embodiment of the retaining elements  3104  engaging the adjunct  3106 . In this illustrated embodiment, the retaining elements  3104  catch various ones of interlaced fibers of the adjunct  3106  to hold the adjunct  3106  thereto. Some or all of the retaining elements  3104  may therefore not extend above the adjunct  3106 , as with the retaining element  3104  illustrated in  FIG. 18 . 
     In other embodiments, the adjunct releasably engaged with the retaining elements  3104  can have a configuration other than a fibrous structure. For example, the adjunct can be a film, and the retaining elements  3104  can extend through the film so as to hook the adjunct thereto. The film may have pre-formed holes therein at locations where the retaining elements  3104  will extend therethrough. 
       FIG. 19  illustrates another embodiment of a staple cartridge  3120  coupled to a retainer  3122  including a plurality of retaining elements  3124  configured to releasably retain an adjunct  3126  to the staple cartridge  3120 . The staple cartridge  3120  is generally configured and used similar to the staple cartridge  40  of  FIGS. 1 and 2 , e.g., has a plurality of staple cavities  3128  in a tissue-facing surface  3130  thereof that each seat a staple therein (the staples are obscured in  FIG. 19 ), is configured to have a sled moved therethrough to push the staples out of the staple cavities  3128 , has a longitudinal slot  3122  through which a knife or other cutting element can translate to cut tissue, etc. The staple cartridge  3120  is releasably seated in the lower jaw  3114  of  FIG. 15  but can be similarly seated in other types of jaws. The cartridge  3120  in this illustrated embodiment does not have any cut-outs or pockets formed therein, but in other embodiments may have a plurality of cuts-outs similar to the cut-outs  3118  of the cartridge  3100  of  FIG. 15 . The adjunct  3126  is a fibrous structure similar to the adjunct  3106  of  FIG. 15  but can have other configurations. 
     The retainer  3122  is generally configured and used similar to the retainer  3102  of  FIG. 15 . The retainer  3122  in this illustrated embodiment is in the form of a pan or tray that has a bottom with opposed sidewalls extending upwardly therefrom. The cartridge  3120  is fixedly seated in the retainer  3122 , which is seated in a channel in the lower jaw  3114 , but can instead be releasably seated in the retainer  3122 . 
     The retaining elements  3124  are also generally configured and used similar to the retaining elements  3114  of  FIG. 15 , e.g., are longitudinally aligned along opposed sides of the retainer  3122  and along opposed sides of the cartridge  3120 , extend upwardly toward the upper jaw coupled to the lower jaw  3114 , etc. However, in this illustrated embodiment, the retaining elements  3124  are in the form of pegs that extend upwardly from the retainer  3122 . The adjunct  3126  is configured to be coupled with the retaining elements  3124  by being pushed straight down thereon, such as by hand or with an applicator tool. Such loading may be easier than with retaining elements in the form of hooks, since an adjunct may need to be loaded onto hooks at an angle that may generally be less intuitive than a straight down motion. The retaining elements  3124  are integrally formed with the retainer  3122 , but similar to that discussed above, can be otherwise attached thereto. In at least some embodiments, one or more of the retaining elements  3124  can include a gripping feature thereon configured to facilitate gripping of the adjunct  3126 , similar to that discussed above. 
       FIGS. 20 and 21  illustrate another embodiment of a staple cartridge  3132  coupled to a retainer  3134  including a plurality of retaining elements  3136  configured to releasably retain an adjunct  3138  to the staple cartridge  3132 . The staple cartridge  3132  is generally configured and used similar to the staple cartridge  40  of  FIGS. 1 and 2 , e.g., has a plurality of staple cavities  3140  in a tissue-facing surface  3142  thereof that each seat a staple therein (the staples are obscured in  FIG. 20  and have already been deployed in  FIG. 21 ), is configured to have a sled  3144  moved therethrough to push the staples out of the staple cavities  3140 , has a longitudinal slot  3146  through which a knife or other cutting element can translate to cut tissue, etc. The sled  3144  is shown in a distal position in  FIG. 21  after it has slid distally a partial distance along an inner bottom surface  3134   s  of the retainer  3134  to deploy staples from the cartridge  3132 , prior to release of the adjunct  3138 , which is discussed further below. The adjunct  3138  is a fibrous structure similar to the adjunct  3106  of  FIG. 15  but can have other configurations. The retaining elements  3136  are also generally configured and used similar to the retaining elements  3114  of  FIG. 15 , e.g., are longitudinally aligned along opposed sides of the retainer  3134  and along opposed sides of the cartridge  3132 , extend upwardly toward the upper jaw coupled to the lower jaw  3114 , are in the form of hooks angled proximally, etc. 
     The staple cartridge  3132  is releasably seated in the lower jaw  3114  of  FIG. 15  but can be similarly seated in other types of jaws. The cartridge  3132  has a plurality of cut-outs or pockets  3148  formed therein, as also shown in  FIG. 22 , that are similar to the cut-outs  3118  of the cartridge  3100  of  FIG. 15 . 
     The retainer  3134  in this illustrated embodiment is in the form of a pan or tray that has a bottom with opposed sidewalls extending upwardly therefrom. The retainer  3134  is generally configured and used similar to the retainer  3102  of  FIG. 15 , but the retainer  3134  in the illustrated embodiment of  FIGS. 20-22  is movably seated in the lower jaw  3114 . The retainer  3134  is configured to move relative to the cartridge  3132  and the lower jaw  3114  to facilitate release of the adjunct  3138 . The retainer  3134  is configured to move from a locked or engaged configuration, which is shown in  FIGS. 20 and 21 , to an unlocked or unengaged configuration, which is shown in  FIG. 22 . In the locked configuration, the retaining elements  3136  each releasably engage the adjunct  3136 , e.g., “lock” the adjunct  3136  to the cartridge  3132 . In the unlocked configuration, the retaining elements  3136  are each disengaged from the adjunct  3136 , e.g., the adjunct  3136  is “unlocked” from the cartridge  3132 . 
     The retainer  3134  includes a release element  3150  configured to facilitate movement of the retainer  3134  from the locked configuration to the unlocked configuration. The release element  3150  is located in a distal portion of the retainer  3134  either at the retainer&#39;s distal edge or, as in this illustrated embodiment, just proximal to the retainer&#39;s distal edge. In this illustrated embodiment, the release element  3150  includes a pair of tabs extending upwardly from the retainer&#39;s inner bottom surface  3134   s , although there can be another number of release elements. The release element can have other configurations, such as a semi-spherical protrusion on the retainer&#39;s inner bottom surface  3134   s , a raised elongate bar on the retainer&#39;s inner bottom surface  3134   s , an elongate bar located above the retainer&#39;s inner bottom surface  3134   s  and extending between opposed inner sides of the retainer  3134 , etc. 
     The release element  3150  is configured to engage the sled  3144  to move the retainer  3134  from the locked configuration to the unlocked configuration. As discussed above, the sled  3144  is configured to slide distally along the cartridge  3134  and lower jaw  3114  on the retainer&#39;s inner bottom surface  3134   s  to deploy the staples through the staple cavities  3140 . The staples pierce through the adjunct  3138  as they are deployed, as also discussed above. The sled  3144  will contact or abut the release element  3150  as its nears the end of its distal translation along the cartridge  3134  and lower jaw  3114 . Continued distal movement of the sled  3144  with the sled  3144  contacting or abutting the release element  3150  pushes the retainer  3134  distally relative to the cartridge  3134  and lower jaw  3114 . The retaining elements  3136  attached to the retainer  3134  will thus also move distally. The distal movement of the retaining elements  3136  causes the retaining elements  3136  to slide free of the adjunct  3138  so as to release the adjunct  3138  therefrom. Thus, unlike the embodiments of the retaining elements  3104 ,  3124  of  FIGS. 15, 18, and 19  that are configured to sequentially release the adjunct coupled thereto in a proximal to distal direction, the retaining elements  3136  are configured to simultaneous release the adjunct  3138 . 
     As shown in  FIGS. 20 and 21 , the retaining elements  3134  are aligned with the cartridge&#39;s cut-outs  3148  when the retainer  3134  is in the locked configuration. As shown in  FIG. 22 , the retaining elements  3134  are not aligned with the cartridge&#39;s cut-outs  3148  when the retainer  3134  is in the unlocked configuration. The adjunct  3136  is thus free to exit the cut-outs  3148  when the retainer  3134  is in the unlocked configuration. 
     The cartridge  3132  can include open space  3152  in a distal portion thereof, as shown in  FIG. 21 . The retainer  3134  is configured to move into the open space  3152  when the retainer  3134  moves distally to move from the locked configuration to the unlocked configuration. 
     The cartridge  3132  can include a stop element in the distal portion thereof configured to contact or abut the retainer  3134  in its locked configuration. The stop element can be configured to stop the distal movement of the retainer  3134  relative to the cartridge  3132  and lower jaw  3114 . The stop element can have a variety of configurations, such as one or more tabs extending upwardly from an inner bottom surface of the cartridge  3132 , a semi-spherical protrusion on the cartridge&#39;s inner bottom surface, a raised elongate bar on the cartridge&#39;s inner bottom surface, an elongate bar located above the cartridge&#39;s inner bottom surface and extending between opposed inner sides of the cartridge  3132 , etc. 
     In an exemplary embodiment, the adjunct  3138  is releasably coupled to the retaining elements  3136  in manufacturing, which may help ensure that the retainer  3134  is in a proper location relative to the cartridge  3132  prior to staple deployment so the retainer  3134  can appropriately slide distally to release the adjunct  3138 . The adjunct  3138  can, however, instead be manually applied to the retaining elements  3136  by a user. 
     In another embodiment, instead of the sled  3144  contacting or abutting the release element  3150  to push the retainer  3134  distally relative to the cartridge  3132  and lower jaw  3114 , an E-beam that advances distally along the cartridge  3132  and lower jaw  3114  can contact or abut the release element  3150  to push the retainer  3134  distally relative to the cartridge  3132  and lower jaw  3114 . In yet another embodiment, both the sled  3144  and an E-beam can contact or abut the release element  3150  to push the retainer  3134  distally relative to the cartridge  3132  and lower jaw  3114 . 
     In another embodiment, instead of the retainer  3134  including the release element  3150 , the cartridge  3132  can include the release element  3150 . The retainer can include an opening for the release element to extend through, e.g., one opening for each of a pair of tabs extending upwardly from the cartridge. The opening and the release element are configured to cooperate to help hold the retainer in position relative to the cartridge until the sled and/or the E-beam contact or abut the release element and push the retainer distally. The release element extending from the cartridge can have elasticity to allow the release element to bend during the distal advancement of the retainer so the retainer can at least partially slide over the release element. 
     In another embodiment, instead of the sled  3144  (and/or the E-beam) contacting or abutting the release element  3150  to push the retainer  3134  distally relative to the cartridge  3132  and lower jaw  3114 , the sled  3144  (and/or the E-beam) contacting or abutting the release element  3150  can move the retainer  3134  in a downward direction such that the retaining elements  3136  move downward and out of engagement with the adjunct  3138 . The cartridge&#39;s bottom surface can slope downward distal to an initial position of the retainer to guide this downward movement of the retainer. 
       FIG. 23  illustrates another embodiment of a staple cartridge  3154  configured to releasably retain an adjunct  3156 . The staple cartridge  3154  is generally configured and used similar to the staple cartridge  40  of  FIGS. 1 and 2 , e.g., has a plurality of staple cavities  3158  in a tissue-facing surface  3160  thereof that each seat a staple therein (the staples are obscured in  FIG. 23 ), is configured to have a sled moved therethrough to push the staples out of the staple cavities  3158 , has a longitudinal slot  3162  through which a knife or other cutting element can translate to cut tissue, etc. The staple cartridge  3154  is releasably seated in a lower jaw  3164  of an end effector that is generally configured and used similar to the lower jaw  3114  of  FIG. 15 . 
     In this illustrated embodiment, the cartridge  3154  includes a plurality of retaining elements  3166  configured to releasably retain the adjunct  3156  to the cartridge  3154 . The retaining elements  3166  are in the form of pegs, similar to the retaining elements  3124  of  FIG. 19 , that extend upwardly from the tissue-facing surface  3160  of the cartridge  3154 . The retaining elements  3166  are arranged in clusters that are longitudinally aligned along opposed sides  3154   a ,  3154   b  of the cartridge  3154 . The number of retaining elements  3166  in each cluster can vary, but in an exemplary embodiment there are at least three retaining elements  3166  in each cluster. In an exemplary embodiment there are at least three clusters of retaining elements  3166  on each side  3154   a ,  3154   b  of the cartridge  3154 . For example, one cluster can be near a proximal end of the cartridge  3154  for releasable attachment to the adjunct  3156  near a proximal end thereof, one cluster can be near a distal end of the cartridge  3154  for releasable attachment to the adjunct  3156  near a distal end thereof, and one cluster can be near a middle of the cartridge  3154  for releasable attachment to the adjunct  3156  near a middle thereof. Any additional clusters can be located between the proximal cluster and the middle cluster and/or between the distal cluster and the middle cluster. Regardless of a number of clusters on each side  3154   a ,  3154   b  of the cartridge  3154 , the clusters can be equidistantly spaced therealong, as in this illustrated embodiment, which may help evenly secure the adjunct  3156  to the cartridge  3154 . In some embodiments, instead of clusters of retaining elements  3166 , the retaining elements  3166  can be individual members aligned longitudinally along the cartridge  3154 . 
     The retaining elements  3166  are integrally formed with the cartridge  3154  in this illustrated embodiment, such as by being molded therewith. In other embodiments, instead of being integral with the cartridge  3154 , the retaining elements  3166  can be separate members attached thereto, such as by welding, adhesive, press fit, etc. 
     The adjunct  3156  in this illustrated embodiment is a fibrous structure that is configured to transition from an original, non-contracted configuration to a contracted configuration under application of heat.  FIG. 24  illustrates the adjunct  3156  in the non-contracted configuration, and  FIG. 25  illustrates the adjunct  3156  in the contracted configuration. In general, the adjunct  3156  can be positioned on the cartridge&#39;s tissue-facing surface  3160  and heated at least in the areas where the retaining elements  3166  are located. The fibers of the adjunct  3156  can separate to allow the retaining elements  3166  to extend into the adjunct  3156 . The application of heat to the adjunct  3156  is configured to cause the adjunct  3156  to transition from the non-contracted configuration to the contracted configuration. The contraction of the adjunct  3156  urges the fibers thereof together to grip the retaining features  3166  and help hold the adjunct  3156  thereto. The contraction of the adjunct  3156  can cause the retaining elements  3166  to deform, as shown in  FIG. 25  in which the retaining elements  3166  have become bent from their straight configuration shown in  FIG. 24 . The deformation of the retaining elements  3166  may help grip the adjunct  3156  and thereby help hold the adjunct  3156  on the cartridge  3154  and/or may facilitate release of the adjunct  3156  since heating the adjunct  3156  can make the adjunct  3156  non-flexible. Exemplary embodiments of contractable adjuncts and of releasably coupling the adjunct to a member such as a staple cartridge or anvil are further described in U.S. application Ser. No. 15/435,891 entitled “Methods And Systems For Mating Constrictable Adjunct Materials With End Effectors” filed on even date herewith. 
     The adjuncts  3106 ,  3126 ,  3138 ,  3156  of  FIGS. 15, 18-20, and 23  are releasably coupled to a staple cartridge and a lower jaw that seats the staple cartridge. In other embodiments, an adjunct can be releasably coupled to an anvil at an upper jaw of a surgical tool. 
       FIG. 26  illustrates one embodiment of an upper jaw or anvil  3168  coupled to a retainer  3170  including a plurality of retaining elements  3172  configured to releasably retain an adjunct to the anvil  3168 .  FIG. 27  illustrates the anvil  3168  and the retainer  3170  prior to their coupling. The anvil  3168  is generally configured and used similar to the upper jaw  34  of  FIGS. 1 and 2 , e.g., has a tissue-facing surface  3174  with staple forming pockets  3176  formed thereon, has a longitudinal slot  3178  through which a knife or other cutting element can translate to cut tissue, etc. The anvil  3168  includes a coupling mechanism  3178  that couples the upper jaw  3168  to a lower jaw of the end effector that is configured to cooperate with the upper jaw  3168  to engage and staple tissue, as discussed above. 
     The retainer  3170  in this illustrated embodiment is in the form of a plate. The retainer  3170  has a longitudinal slot  3180  through which a knife or other cutting element can translate to cut tissue, etc. The slot  3180  is open at a proximal end thereof to allow the knife or other cutting elements to slide therein. The slot  3180  is thus configured to be aligned with the anvil&#39;s longitudinal slot  3178  when the retainer  3170  is coupled to the anvil  3168 . The slot  3180  extends along a partial longitudinal length of the retainer  3170  to allow the retainer  3170  to be a singular element, e.g., with a connected distal end. In other embodiments, the retainer  3170  can be a two-piece element with left and right sides providing a space therebetween through which the knife or other cutting element can translate to cut tissue, etc. 
     The retainer  3170  can be formed from any of a variety of materials. In an exemplary embodiment, the retainer  3170  is formed from a plastic or polymer such that the retainer  3170  has elasticity. 
     The retainer  3170  is configured to releasably couple to the anvil  3168  so as to be positioned over the anvil&#39;s tissue-facing surface  3174 , as shown in  FIG. 26 . The slot  3180  can be wide enough to not obscure any of the staple forming pockets  3176  on the anvil&#39;s tissue-facing surface  3174  such that staples can be deployed from a lower jaw coupled to the upper jaw  3168 , pierce through the adjunct, and be formed by the staple forming pockets  3176 . 
     The retainer  3170  includes at least one attachment mechanism  3182  configured to releasably attach the retainer  3170  to the anvil  3168 . The retainer  3170  being releasably coupled to the anvil  3168  may allow for re-use of the retainer  3170  with different anvils and/or may facilitate cleaning of the retainer  3170  and/or anvil  3168  since the retainer  3170  can be removed from the anvil  3168  prior to cleaning of one or both of the retainer  3170  and anvil  3168 . In other embodiments, the retainer  3170  can be fixed to the anvil  3168 , which may help ensure that the retaining elements  3172  are in a desirable location relative to the anvil  3168 , which may help the adjunct be desirably positioned over the anvil&#39;s tissue-facing surface  3174 . The attachment mechanism  3182  in this illustrated embodiment includes a pair of arms. The retainer  3170  in this illustrated embodiment including three pairs of arms, but can have another number of pairs in other embodiments. The arms are configured to snap around an exterior of the anvil  3168 , as shown in  FIG. 26 . 
     The attachment mechanism  3182  is integrally formed with the retainer  3170  in this illustrated embodiment. The attachment mechanism  3182  can thus also, in an exemplary embodiment, have elasticity. The attachment mechanism  3182  having elasticity may help the attachment mechanism  3182  snap around the anvil  3168 . In other embodiments, instead of being integral with the retainer  3170 , the attachment mechanism  3182  can be a separate member attached thereto. 
     The retaining elements  3172  are in the form of pegs, similar to the retaining elements  3124  of  FIG. 19 , and extend downwardly from the tissue-facing surface  3174  of the anvil  3168  in a direction toward the lower jaw coupled to the upper jaw  3168 . The retaining elements  3172  are arranged in clusters that are longitudinally aligned along opposed sides  3170   a ,  3170   b  of the retainer  3170 , similar to the clusters of the retaining elements  3166  of  FIG. 23  discussed above. Each of the clusters has two retaining elements  3172  but can have another number. The retainer  3170  has five clusters along each side  3170   a ,  3170   b  of the retainer  3170  but can have another number. 
     The retaining elements  3172  are integrally formed with the retainer  3170  in this illustrated embodiment. The retaining elements  3172  can thus also, in an exemplary embodiment, have elasticity.  FIG. 28  illustrates flexing of the retaining element  3172  allowed by the elasticity, with the retaining element  3172  in phantom showing the retaining element  3172  bent. In other embodiments, instead of being integral with the retainer  3170 , the retaining elements  3172  can be separate members attached thereto. Also, in other embodiments, the retaining elements  3172  can be integrally formed with the anvil  3168  or be separate members attached thereto such that a retainer is not used. 
     The adjunct releasably coupled to the anvil  3168  can have a variety of configurations, as discussed above. In an exemplary embodiment, the adjunct is a fibrous structure or a film. 
       FIG. 29  illustrates another embodiment of an upper jaw or anvil  3184  coupled to a retainer  3186  including a plurality of retaining elements  3188  configured to releasably retain an adjunct to the anvil  3190 .  FIG. 30  illustrates the anvil  3184  and the retainer  3186  prior to their coupling. The retaining elements  3188  are configured and used similar to the retaining elements  3172  of  FIG. 27  except that in this illustrated embodiment the proximal-most clusters on either side  3186   a ,  3186   b  of the anvil  3184  have three retaining elements  3188  each while a remainder of the clusters have two retaining elements  3188  each. 
     The retainer  3186  is generally configured and used similar to the retainer  3170  of  FIG. 27  except that in this illustrated embodiment the retainer&#39;s attachment mechanism  3190  includes a frame. The retainer  3186  in this illustrated embodiment including three frames, but can have another number of frames in other embodiments. The frames are configured to slide around an exterior of the anvil  3184  and be seated in recesses  3192  formed in the anvil&#39;s exterior surface. A distal end  3194  of the anvil  3184  can be advanced in a distal direction through a proximal-most one of the frames and continue advancing distally until the frames each align with respective ones of the recesses  3192 , thereby coupling the anvil  3184  and the retainer  3186  together. The anvil  3184  can be moved in a proximal direction relative to the retainer  3186  to remove the anvil  3184  from the retainer  3186 . The attachment mechanism  3190  can have elasticity, as discussed above, which may facilitate seating thereof in the recesses  3190  as well as facilitate removal of the anvil  3168  from the retainer  3186 . The anvil  3184  is generally configured and used similar to the anvil  3168  of  FIG. 27  except that the anvil  3184  in this illustrated embodiment includes the recesses  3192  that extend radially around its outer surface. 
     The adjunct releasably coupled to the anvil  3184  can have a variety of configurations, as discussed above. In an exemplary embodiment, the adjunct is a fibrous structure or a film. 
     Adjunct Release for Surgical Staplers 
     Various exemplary devices, systems, and methods for releasably retaining an adjunct material on an end effector of a surgical instrument are described herein. In some implementations, an adjunct material can be releasably retained on a jaw of an end effector in a manner that reduces or prevents the adjunct material from prematurely slipping off the jaw. In this way, the adjunct can be securely coupled to the end effector while a surgeon manipulates the end effector during a surgical procedure. The adjunct material can be coupled to an end effector in a variety of ways, for example by inserting portions of the adjunct into connection cavities on a tissue-facing surface of the jaw. In some embodiments, the adjunct can have tags or protrusions that extend from an outward facing surface such that the tags can be configured to be received in cavities on the tissue-facing surface of the jaw. In other implementations, the adjunct can be coupled to the tissue-facing surface of the jaw using an adhesive. The adjunct can remain coupled to the end effector until it is separated from the end effector and transferred to a treatment site in a patient, for example by a release mechanism that includes features and/or components that are configured for releasably attaching an adjunct thereto. A variety of release mechanisms can be used, such as staple deployment members and/or a cutting element that causes the adjunct to separate from the end effector. The release mechanism can thus allow a user to securely attach an adjunct to an end effector and allow the user to rapidly deploy the adjunct when desired. 
     Attaching an adjunct to and releasing an adjunct from an end effector can be achieved through a variety of techniques.  FIGS. 31-33  illustrate one embodiment of an end effector  4100  having an adjunct releasing mechanism.  FIG. 31  illustrates a portion of a lower jaw  4101  of the end effector  4100 , which can be disposed on a distal end of a surgical instrument, such as surgical staplers  10 ,  50  discussed above. The lower jaw  4101  can have a cartridge  4102  disposed thereon, similar to the staple cartridge  40 , that has a tissue-facing surface  4106  with an adjunct  4104  (only a portion of the adjunct  4104  is shown) disposed thereon, such as one or more of the buttresses, adjuncts, and/or medicants discussed above. 
     The cartridge  4102  can have staples disposed in staple cavities  4108  which are formed in the tissue-facing surface  4106 . The tissue-facing surface  4106  can also have a channel  4112  configured to receive a cutting element, similar to the knife blade  36 , as it moves distally therethrough. One or more connection cavities  4110  can extend between and connect the staple cavities  4108  for attaching an adjunct to the cartridge  4102 . The connection cavities  4110  can be in the form of recesses or bores, and can have a variety of configurations and shapes. For example, the connection cavities  4110  can be roughly oval in shape and smaller than the staple cavities  4108 . In other embodiments, the cavities can be circular, square, rectangular, 3-dimensional shapes, etc., and they can be larger than, equal in size to, or a combination of sizes relative to the staple cavities  4108 . The cavities  4110  can be disposed between rows of the staple cavities  4108 . However, the connection cavities  4110  can have any number of configurations, such as each staple cavity  4108  having a connection cavity  4110  adjacent thereto. While the connection cavities  4110  are formed adjacent to the staple cavities  4108  on the tissue-facing surface  4106 , they can be formed elsewhere. For example, the cavities can be formed at the interface of the cartridge and a tray, similar to tray  37 , such that some portion of the inner surface of the cavity is a surface of the cartridge, and another portion is a surface of the tray. Furthermore, connection cavities for attaching and detaching an adjunct need not be limited to the tissue-facing surface of the cartridge. For example, connection cavities can be formed along the edge of the tissue-facing surface of the cartridge such that when the end effector is assembled, a portion of the connection cavity will be formed by a staple tray similar to staple tray  37 . Alternatively, rather than connection cavities, a channel can be formed between the tissue-facing surfaces of the cartridge and the tray. Portions of the adjunct can be tucked into the channel, or adhered to the tissue-facing surface at locations proximal to the channel, during manufacturing or at any time prior to use. In such an embodiment, drivers near the outermost edge of the tissue-facing surface of the cartridge can have an adjunct releasing mechanism such that portions of the adjunct are pushed out of the channel, and/or break the adhesive bond along the channel between the adjunct and the cartridge during firing. 
     The adjunct  4104  can be configured to be releasably retained on the tissue-facing surface  4106 . The adjunct  4104  can have protrusions or tabs disposed on a surface that contacts the tissue-facing surface  4106 , and the protrusions can be configured to extend into and engage with the connection cavities  4110 . The adjunct  4104  can be configured to engage the tissue-facing surface  4106  through a variety of means. For instance, protrusions on the adjunct can be received in the connection cavities and securely attaching due to a friction fit attachment. In such an example, an adjunct can be created by extruding a film such that it has protrusions in predefined locations that correspond to locations of the connection cavities on a tissue-facing surface of a cartridge. In other embodiments, the adjunct can be made from a VICRYL® (polyglactin  910 ) material, and can include one or more backing layers made of polydioxanone (PDS). The one or more PDS layers can be fused to the VICRYL® material, and the one or more PDS layers can include protrusions that can be configured to extend into and mate with the connection cavities. In addition or alternatively, the adjunct can engage the tissue-facing surface through use of an adhesive, such as cyanoacrylate. 
     The cartridge  4102  can have one or more staple drivers  4200 ,  4300  movably disposed therein, similar to staple drivers  48 . The staple drivers  4200 ,  4300  can be configured to move upward through the staple cavities  4108  to apply an upward force on each of the plurality of staples within the cartridge  4102 . The staple driver  4200  illustrated in  FIG. 32  can have a staple portion  4202  that can have a staple channel  4208  formed on an upper end thereon and that can be configured to seat a staple therein, similar to the staple driver  48 . The driver  4200  can also have an adjunct releasing mechanism  4203  attached to a side of the staple portion  4202  and having a generally L-shaped configuration. The adjunct releasing mechanism  4203  can have a connecting element  4204  that connects the staple portion  4202  to the adjunct releasing mechanism  4203 . A post  4206  can be attached to the connecting element  4204  and it can extend upward in the same direction as the staple channel  4208  of the staple portion  4202 . The connecting element  4204  can have an upward-angled bottom  4205  that is configured to contact a wedge sled, similar to the wedge sled  47 , to allow upward movement of the driver  4200  and firing of the staples. The post  4206  can have a variety of shapes, such as a rectangular shape as illustrated in  FIG. 32 , a cylindrical shape, a square, etc. In an exemplary embodiment, the post  4206  has a shape that corresponds to a shape of the connection cavity  4110  such that the post  4206  can be received in the connection cavity  4110 . 
       FIG. 33  illustrates another embodiment of a staple driver  4300  that can be configured similar to the staple driver  4200 . However, staple driver  4300  can have first and second staple portions  4302 ,  4303  similar to the staple portion  4202  with staple channels  4308 ,  4310  disposed on upper ends of the staple portions  4302 ,  4303 , respectively. Each staple channel  4308 ,  4310  can be configured to seat a staple therein, and the staple driver  4300  can be configured to fire two staples simultaneously. The first and second staple portions  4302 ,  4303  can have an adjunct releasing mechanism  4304  coupled therebetween. The adjunct releasing mechanism  4304  can include a connecting element  4305  and a post  4306 . The connecting element  4305  extends between and connects the two staple portions  4302 ,  4303 , and it has an upward-angled bottom  4309  that is configured to contact a wedge sled, similar to the wedge sled  47 , to allow upward movement of the driver  4300  and firing of the staples. The post  4306  is attached to the connecting element  4305  and extends upward in the same direction as the staple channels  4308 ,  4310 . The post  4306  can have a variety of shapes, such as a rectangular shape as illustrated in  FIG. 32 , a cylindrical shape, a square, etc. In an exemplary embodiment, the post  4306  has a shape that corresponds to a shape of the connection cavity  4110  such that the post  4306  can be received in the connection cavity  4110 . 
     While the illustrated staple drivers  4200 ,  4300  have connecting elements between the staple portions and the adjunct releasing mechanisms, a variety of connections can be used to connect multiple staple drivers. For example, two connecting elements can be used to connect three staple drivers. One skilled in the art will appreciate that a connecting element can include multiple adjunct releasing mechanisms, that multiple connecting elements can be used in parallel or in series to connect multiple staple drivers, and that the adjunct releasing mechanisms can have any number of geometries. For example, the adjunct releasing mechanisms can be curved, or can have cross-sections that are square, circular, triangular, etc. Additionally, it is possible that not all of the adjunct releasing mechanisms are uniform. The adjunct releasing mechanisms can have sharp features, as well. For example, the detachment features can be sharpened such that they can cut away a small portion of the adjunct to detach the rest from a tissue-facing surface of a cartridge. 
     In use, the staple drivers  4200  and/or  4300  can be disposed in the cartridge  4102  and aligned with the staple cavities  4108  and the connection cavities  4110  such that the staple channels  4208 ,  4308 ,  4310  are aligned with the staple cavities  4108  and the posts  4206 ,  4306  are aligned with the connection cavities  4110 . The cartridge  4102  can be loaded with staples. The adjunct  4104  can be retained on the tissue-facing surface  4106  by, for example, having a plurality of protrusions friction fit within the connection cavities  4110 . The adjunct  4104  can be applied to the tissue-facing surface  4106  any time before use, such as during manufacture or during preparation for use, and can be applied through a variety of techniques, such as by use of an applicator. 
     A surgeon can maneuver the surgical stapler into position and clamp tissue between jaws of the end effector  4100  thereon. The surgeon can then fire the surgical stapler, causing a sled, similar to wedge sled  47 , to move distally through the cartridge  4102  of the end effector  4100 . The sled can push one or more of the staple drivers  4200 ,  4300  upwardly through the staple cavities  4108  in the staple cartridge  4102 . Upward movement of the staple drivers  4200 ,  4300  applies an upward force on each of the plurality of staples within the cartridge  4102  to thereby push the staples upwardly through the adjunct  4104  and tissue and against an anvil surface of an upper jaw of the end effector  4100  to form the staples. Upward movement of the staple drivers  4200 ,  4300  also moves the posts  4206 ,  4306  upwards. The posts  4206 ,  4306  apply an upward force on the protrusions of the adjunct  4104 , forcing the protrusions out of the connection cavities  4110  as distal ends of the posts  4206 ,  4306  enter the cavities  4110 . Forcing the protrusions from the cavities  4110  releases the adjunct  4104  from the tissue-facing surface  4106 , and the adjunct can be secured by staples to the tissue grasped by the end effector  4100 . In other embodiments, the posts  4206 ,  4306  can be configured to force the protrusions only partially out of the connection cavities  4110 , which can be sufficient to loosen the adjunct  4104  from the tissue-facing surface  4106  enough such that the staples will remove the adjunct  4104  entirely upon firing. In various embodiments, firing the surgical stapler can also cause a cutting element to translate through the cartridge  4102  along the channel  4112  to tissue while staples are fired and the adjunct  4104  is released. 
     While the adjunct  4104  can be attached to the cartridge  4102  by protrusions, as noted above, adjuncts can be attached to a cartridge of a surgical stapler through a variety of means. For example,  FIG. 34  illustrates an end effector  4400  with a cartridge  4402  and an adjunct  4404  secured thereto by an adhesive. The end effector  4400  can generally function and include components similar to end effector  4100 . For example, the end effector  4400  can include an upper jaw having an anvil (not shown) and a lower jaw  4401  with the cartridge  4402  engaged thereon. 
     The cartridge  4402  can have staples  4416  disposed in a plurality of staple cavities  4408  and a plurality of connection cavities  4410  formed in a tissue-facing surface  4406 . The connection cavities  4410  can have a variety of configurations and shapes. For example, the connection cavities  4410  can be roughly oval in shape and smaller than the staple cavities  4408 . In other embodiments, the connection cavities  4410  can be circular, square, rectangular, etc., and they can be larger than, equal in size to, or a combination of sizes relative to the staple cavities  4408 . The connection cavities  4410  can be disposed between rows of the staple cavities  4408 . However, the connection cavities  4410  can have any number of configurations. 
     The adjunct  4404  can be configured to be releasably retained on the tissue-facing surface  4406 , and the adjunct  4404  can be any of the adjuncts discussed herein. The adjunct  4404  can have adhesive disposed on a surface that contacts the tissue-facing surface  4406 . For example, there can be adhesive points  4405  between the adjunct  4404  and the tissue-facing surface  4406  around outer edges of the connection cavities  4410  that can be configured to retain the adjunct  4404  on the cartridge  4402 . However, a variety of different placements of the adhesive points  4405  is possible, such as in a grid pattern. Additionally, the adhesive can be spread uniformly on the tissue-facing surface  4406 . A variety of adhesives can be used, such as cyanoacrylate. 
     When the adjunct is attached to the cartridge with an adhesive, it can be desirable in various embodiments to prevent the adhesive from spilling into the cartridge, for example into a cutting element channel or into the staple cavities. Various adjuncts can be configured to include features that prevent or inhibit adhesive from spilling into the cartridge and/or specifically the cutting element channel of the cartridge during the attachment process. As an example, the adhesive points  4405  can be formed by including small circular molded features on a surface of the adjunct  4404  that contacts the tissue-facing surface  4406  of the cartridge  4404 . The circular molded features can act as reservoirs to form adhesive droplet attachment point insuring the adhesive, such as cyanoacrylate, does not enter the cartridge  4402  and/or the cutting element channel during attachment. In other embodiments, the adhesive can be housed within the adjunct itself, or reservoirs for adhesive can be part of an applicator used to apply the adjunct to the cartridge. For example, the reservoirs can be broken as part of clamping or pulling an activation lever on the applicator. 
     The cartridge  4402  can have one or more staple drivers  4411  movably disposed therein, similar to staple drivers  4200 ,  4300 , that can be configured to move upward through staple cavities  4408  to apply an upward force on each of the plurality of staples  4416  within the cartridge  4402 . Each staple driver  4411  can have a staple portion  4412  that can have a staple channel  4413  formed on an upper end thereof that is configured to seat a staple  4416  therein. The driver  4411  can also have an adjunct releasing mechanism attached to a side of the staple portion  4412  and having a post  4414  that is attached to the staple portion  4412  and that extends upward in the same direction as the staple channel  4413  of the staple portion  4412 . The staple driver  4411  can have an upward-angled bottom  4409  that is configured to receive a wedge sled  4420 , similar to the wedge sled  47 , to allow upward movement of the driver  4200  and firing of the staple. The post  4414  can have a variety of shapes, such as a rectangular shape, a cylindrical shape, a square shape, etc., and the post  4406  can be configured to be received in the connection cavities  4410 . 
     In use, the cartridge  4402  can have a plurality of the staple drivers  4411  disposed therein and loaded with staples  4416 . The adjunct  4404  can be retained on the tissue-facing surface  4406  by, for example, having a plurality of adhesive points  4405  between the adjunct  4404  and the tissue-facing surface  4406  around the outer edges of the connection cavities  4410 . The adjunct  4404  can be applied to the tissue-facing surface  4406  any time before use, such as during manufacture or during preparation for use, and can be applied through a variety of techniques, such as by use of an applicator. A surgeon can maneuver the surgical stapler into position and clamp tissue between jaws of the end effector  4400  thereon. The surgeon can then fire the surgical stapler, causing the sled  4420  to move distally through the cartridge  4402  of the end effector  4400 . The sled  4420  can push one or more of the staple drivers  4411  upwardly through the staple cavities  4408  in the staple cartridge  4402 . Upward movement of the staple drivers  4411  applies an upward force on each of the plurality of staples  4416  within the cartridge  4402  to thereby push the staples upwardly through the adjunct  4404  and tissue and against an anvil surface of the upper jaw of the end effector  4400  to form the staples. Upward movement of the staple drivers  4411  also moves the posts  4414  upwards. The posts  4414  can apply an upward force on the adjunct  4404 , forcing the adjunct  4404  to move upwards and breaking the adhesive points  4405  once the posts  4414  move sufficiently through the connection cavities  4411 . For example, the adhesive points  4405  can hold firm until a distalmost end of the posts  4414  crosses a plane of the tissue-facing surface  4406 . Breaking, cracking, or separating the adhesive points  4405  from between the adjunct  4404  and the tissue-facing surface  4406  releases the adjunct  4404  from the tissue-facing surface  4406 , and the adjunct  4404  can be secured by the staples  4416  to the tissue grasped by the end effector  4400 . Although a distalmost end of the posts  4414  can cross a plane of the tissue-facing surface  4406 , the posts  4414  can be configured such that they only extend even with, or below, the tissue-facing surface  4406 . In some embodiments, firing the surgical stapler can also cause a cutting element to translate through the cartridge  4402 , cutting tissue while the staples  4416  are fired and the adjunct  4404  is released. 
     While an adjunct can be attached to a lower jaw as illustrated above, an adjunct can also be attached to components of the upper jaw, such as the anvil. The upper jaw can be similar to that shown in  FIGS. 1-2 , but can include features and/or components for attaching and detaching an adjunct. For example, the upper jaw can be configured to include connection cavities and drivers that are driven by an E-beam to cause the adjunct to detach from the jaw. In various embodiments, when stapling is initiated, the components of the lower jaw can function to drive staples through tissue and the adjunct, while the drivers in the upper jaw can function to detach the adjunct from the anvil. 
     End Effector Having Extension Features for Mating with Adjuncts 
     Various exemplary techniques for releasably retaining an adjunct material on one or both jaws of an end effector of a surgical instrument are described herein. One or both of the opposed jaws can have extension elements formed thereon that extend beyond a nominal perimeter of that jaw. The extension elements are formed outside an area of the jaw&#39;s tissue-contacting and treating surface having staple-holding cavities (if the jaw is a cartridge body) or a tissue-contacting surface having staple-forming cavities (if the jaw is an anvil). An adjunct material configured to be releasably retained on the jaw can have a shape complementary to that of the jaw. 
     In some implementations, an end effector for a surgical instrument has first and second jaws, at least one of which is movable relative to the other one between open and closed positions. For example, the first jaw can have a cartridge body having on a tissue-contacting surface thereof a plurality of staple cavities configured to seat staples therein. The first jaw can have a generally rectangular nominal perimeter defining a regular perimeter around outer rows of the plurality of staple cavities. The second jaw can have or can be an anvil with a plurality of staple forming cavities formed on a tissue-contacting surface thereof. The second jaw can also have a generally rectangular nominal perimeter opposed to the nominal perimeter of the first jaw. 
     At least one of the first and second jaws can have a plurality of attachment features formed thereon on extension elements extending beyond the nominal perimeter of the at least one jaw. Each of the extension elements can have at least one attachment feature formed thereon. For example, the attachment feature can be a projection extending from the corresponding extension element. The attachment feature is configured to mate with a corresponding mating feature formed on an adjunct material that has a shape complementary to a shape of the jaw. 
       FIGS. 35, 36, 37, and 38  illustrate an example of an end effector  5100  of a surgical instrument configured to be coupled to a distal end of an elongate shaft of the surgical instrument (not shown). The end effector  5100  has a first jaw in the form a cartridge body  5102  and a second opposed jaw in the form of an anvil  5104  that are configured to clamp tissue therebetween. At least one of the cartridge body  5102  and the anvil  5104  is movable relative to the other between open and closed positions. In some embodiments, the cartridge body  5102  can seat therein a removable and replaceable cartridge. Furthermore, in some embodiments, the cartridge body  5102  can be part of a disposable loading unit coupled distally to an elongate shaft of a surgical instrument. One or both of the jaws of the end effector can have an implantable adjunct material releasably retained thereon. For example, the cartridge body  5102  can have an adjunct material  5101  shown in  FIG. 38  releasably retained thereon as discussed in more detail below. 
     The cartridge body  5102  has a tissue-contacting surface  5106  having a plurality of staple cavities  5108  (shown partially in  FIGS. 36 and 37 ) configured to seat staples therein. The tissue-contacting surface  5106  can have an adjunct material disposed thereon and may therefore not directly contact tissue. Moreover, the tissue-contacting surface  5106  is also a tissue-treating surface. The anvil  5104  has a plurality of staple forming cavities formed on a tissue-contacting (and treating) surface thereof, which are obscured in  FIG. 35 . In this example, both the cartridge body  5102  and the anvil  5104  are generally rectangular. As schematically shown in  FIG. 36 , the cartridge body  5102  has a longitudinal axis  5 A 1  and a generally rectangular nominal perimeter  5110  defining a regular perimeter around outer rows of the plurality of staple cavities  5108 . The nominal perimeter  5110  has long sides  5112   a ,  5112   b  extending along the longitudinal axis  5 A and short sides  5114   a ,  5114   b . The anvil  5104  can also have a generally rectangular nominal perimeter opposed to the nominal perimeter  5114  of the cartridge body  5102 . 
     In the example illustrated, the cartridge body  5102  has multiple extension elements  5118  extending beyond the nominal perimeter  5110 . In particular, as shown in  FIG. 35 , the extension elements  5118  protrude from the cartridge body  5102  such that they extend beyond the side walls of the cartridge body  5102 , such as a sidewall  5115  in  FIGS. 35-37 . As shown, the extension elements  5118  are formed outside the area of the cartridge body  5102  having the staple holding cavities  5108 . In this example, six extension elements  5118   a ,  5118   b ,  5118   c ,  5118   d ,  5118   e ,  5118   f  are shown formed on the cartridge body  5102 . As shown in  FIG. 36 , the extension elements  5118  are formed along at least one of the long sides  5112   a ,  5112   b  of the nominal perimeter  5114 , in the plane of the tissue-contacting surface  5106  of the cartridge body  5102 . In embodiments in which the cartridge body  5102  is in the form of a channel configured to removably and replaceably sit therein a cartridge with staples, the extension elements are formed on a body of the channel. In embodiments in which the entire cartridge body  5102  is removable and replaceable (e.g., as part of a disposable loading unit), the extension elements are formed on the cartridge body  5102 . 
     As shown, the distal-most extension elements  5118   a ,  5118   d  are formed on opposite sides from a knife channel  5105  ( FIG. 36 ) at a distal end  5102   d  of the cartridge body  5102 , adjacent to a distal tip  5103 . The extension elements  5118   b ,  5118   e  are formed more proximally on both sides of the knife channel  5105 , and the extension elements  5118   d ,  5118   f  are the closest to the proximal end  5102   p  of the cartridge body  5102 . In this example, the pairs of extension elements formed at opposed sides from the knife channel  5105  (e.g., the extension elements  5118   a ,  5118   d ) can be disposed along the same axis, which can be perpendicular to the longitudinal axis  5 A 1  of the jaw  5102 . The extension elements formed along the same side of the jaw can be spaced equidistantly from one another along the side of the jaw, or one or more of the extension elements can be spaced differently from other extension elements. 
     The extension elements  5118  can have a number of different configurations. In the example illustrated, the extension elements  5118  have a trapezoidal shape (e.g., of an isosceles trapezoid) with its longer base being the closest to the nominal perimeter of the cartridge body  5102 . However, it should be appreciated that the extension elements formed on the cartridge body can be rectangular, square, semi-circular, or they can have any other suitable shape(s), including regular and irregular shapes. Also, the cartridge body can have extension elements of two or more different configurations and/or sizes. 
     Furthermore, six extension elements  5118   a ,  5118   b ,  5118   c ,  5118   d ,  5118   e ,  5118   f  are shown by way of example only, as any suitable number of extension elements can extend beyond the nominal perimeter of the cartridge body. For example, one, two, three, four, five, or greater than six extension elements can be formed. Also, a different number of extension elements can be formed on one long side  5112   a  of the cartridge body  5102  as compared to the cartridge body&#39;s another long side  5112   b.    
     As in the implementation shown in  FIGS. 35-37 , the extension elements can be formed in the plane that is parallel to the tissue-contacting surface  5106  of the cartridge body  5102 . However, in other implementations, one or more of the extension elements can have at least a portion thereof formed at an angle to the tissue-contacting surface  5106  of the cartridge body  5102 , in a manner that does not interfere with proper operation of the end effector. The extension elements  5118   a ,  5118   b ,  5118   c ,  5118   d ,  5118   e ,  5118   f  can be formed monolithically and/or integrally with the cartridge body  5102 . Furthermore, in some embodiments, the extension elements can be separate features coupled to the cartridge body  5102  in a suitable way. 
     The cartridge body  5102  and the extension elements  5118  have a size such that the cartridge body  5102  with the cartridge body  5102  with the extension elements  5118  extending therefrom fit within a trocar providing access to a surgical site. For example, in the illustrated embodiments, the cartridge body  5102  with the extension elements  5118  is sized such that the end effector  5100  has an overall diameter smaller than 12.8 mm. As a person skilled in the art will appreciate, regardless of the specific configuration of the cartridge body or anvil, the extension elements are formed thereon such that the end effector can fit within a suitable surgical site access instrument. 
     As shown in  FIGS. 35-37 , the extension elements  5118   a ,  5118   b ,  5118   c ,  5118   d ,  5118   e ,  5118   f  have respective attachment features  5120  formed thereon. In this example, each of the extension elements  5118   a ,  5118   b ,  5118   c ,  5118   d ,  5118   e ,  5118   f  has a respective one of the attachment features  5120   a ,  5120   b ,  5120   c ,  5120   d ,  5120   e ,  5120   f  formed thereon. Each of the attachment features can be in the form of a post or a projection extending from a respective extension element perpendicular to the longitudinal axis  5 A 1  of the cartridge body  5102 . The projection can have a rounded tip or a tip having other suitable configuration. However, it should be appreciated that the attachment features formed on the extension elements  5118  can have any other various configurations. Also, in some implementations, the jaw (e.g., the cartridge body  5102 ) can have attachment features of more than one type formed thereon. 
     One or both of the cartridge body  5102  and anvil  5104  can have an adjunct material (or “adjunct”) releasably retained thereon. In the illustrated implementation, the adjunct material has a shape complementary to a shape of the jaw on which it is mounted and the adjunct material is configured to releasably mate with the attachment features formed on the extension elements of the jaw. Thus, the adjunct has a generally rectangular nominal perimeter with discrete extension elements that extend beyond the nominal perimeter in a plane parallel to a surface of the adjunct configured to contact tissue. The extension elements can be formed on the adjunct such that at least two extension elements are formed along each of long sides of the adjunct&#39;s nominal perimeter. Each of the extension elements can have at least one mating feature configured to mate with a respective attachment features formed on the jaw. 
       FIG. 38  shows the adjunct material  5101  that can be releasably retained on the tissue-contacting surface  5106  of the cartridge body  5102 . As shown in  FIG. 38 , the adjunct material  5101  has a shape that corresponds to the shape of the cartridge body  5102 —extension elements  5128 , such as elements  5128   a ,  5128   b ,  5128   c ,  5128   d ,  5128   e ,  5128   f  are formed that extend beyond a nominal perimeter  5127  in a plane parallel to a surface of the adjunct  5101  configured to contact tissue. The extension elements  5128  can be formed integrally with the adjunct material  5101  or they can be separate elements coupled to the adjunct  5101  along the nominal perimeter  5127  thereof in a suitable manner. 
     The extension elements  5128   a ,  5128   b ,  5128   c ,  5128   d ,  5128   e ,  5128   f  are configured to be disposed over the respective extension elements  5118   a ,  5118   b ,  5118   c ,  5118   d ,  5118   e ,  5118   f  extending beyond the nominal perimeter  5110  of the cartridge body  5102 . Thus, the shape of the adjunct  5101  is such that it “traces” the shape of the cartridge body  5102 . The size of the adjunct material  5101  also corresponds to the size of the cartridge body  5102 . In this way, the adjunct material  5101  is aligned with the cartridge body  5102  when the adjunct  5101  is disposed thereon. 
     The adjunct material  5101  can be configured to mate with the cartridge body  5102  in a variety of different ways. In the example illustrated, as shown in  FIG. 38 , the adjunct material  5101  has a plurality of mating features  5130 , such as mating features  5130   a ,  5130   b ,  5130   c ,  5130   d ,  5130   e ,  5130   f  that are complementary to the attachment features  5120   a ,  5120   b ,  5120   c ,  5120   d ,  5120   e ,  5120   f  formed on the cartridge body  5102  and are configured to releasably mate with the attachment features  5120   a ,  5120   b ,  5120   c ,  5120   d ,  5120   e ,  5120   f . In the illustrated implementation, the mating features are in the form of through openings formed in the adjunct material  5101 . The openings are configured so as to receive the projections therein, such that the adjunct material can be released from the engagement with the jaw when staples are ejected from staple cavities. 
     The mating features  5130   a ,  5130   b ,  5130   c ,  5130   d ,  5130   e ,  5130   f  are formed on the adjunct&#39;s extension elements  5128   a ,  5128   b ,  5128   c ,  5128   d ,  5128   e ,  5128   f  as shown in  FIG. 38 , at locations on these extension elements corresponding to the locations of the cartridge&#39;s attachment features  5120   a ,  5120   b ,  5120   c ,  5120   d ,  5120   e ,  5120   f . In this way, when the adjunct material  5101  is superimposed over the cartridge body  5102 , the mating features  5130   a ,  5130   b ,  5130   c ,  5130   d ,  5130   e ,  5130   f  align with the cartridge&#39;s attachment features  5120   a ,  5120   b ,  5120   c ,  5120   d ,  5120   e  such that each opening receives therein a corresponding projection. The cartridge&#39;s attachment features and adjunct&#39;s mating features can releasably mate via a friction fit or in other ways. 
     As shown in  FIG. 35  illustrating a partially transparent view of the anvil  5104 , the anvil  5104  can also have extension elements  5122 , such as elements  5122   a ,  5122   b ,  5122   c ,  5122   d ,  5122   e ,  5122   f , formed thereon that beyond the nominal perimeter  5124  thereof. Each of the extension elements  5122  can have a shape and size similar to that of the extension elements  5118  formed on the cartridge body  5102 . For example, as illustrated, the extension elements  5122  can be generally trapezoidal, though they can have other shapes, as the described techniques are not limited in this respect. Similar to the cartridge body  5102 , each of the extension elements  5122  can have a respective attachment feature  5126  thereon for mating with an adjunct to be releasably retained on the anvil  5104 .  FIG. 35  illustrates that each of the extension elements  5122   a ,  5122   b ,  5122   c ,  5122   d ,  5122   e ,  5122   f  can have a respective one of the attachment features  5126   a ,  5126   b ,  5126   c ,  5126   d ,  5126   e ,  5126   f  formed thereon. 
     In the illustrated implementation, the extension elements  5122  are formed on the anvil  5104  in a manner such that they do not overlap with the extension elements  5118  formed on the cartridge body  5102 . Thus, as shown in  FIG. 35  and additionally in  FIG. 37  (where a shadow or footprint  5134  of the anvil  5104  is schematically shown superimposed over the cartridge body  5102 ), the extension elements  5122  are staggered with respect to the extension elements  5118 . 
     In the described embodiments, the respective extension elements are formed on the cartridge body  5102  and the anvil  5104  such that, when the end effector  5100  is in the closed position, the cartridge body&#39;s extension elements  5118  extend beyond the nominal perimeter of the anvil  5104  and the anvil&#39;s extension elements  5122  extend beyond the nominal perimeter of the cartridge body  5102 . For example,  FIG. 39 , showing the end effector  5100  in a closed configuration, illustrates that the footprint of the cartridge body  5102  is outside the footprint of the anvil  5104  and that the extension elements  5122   a ,  5122   b ,  5122   c ,  5122   d ,  5122   e ,  5122   f  are staggered with respect to the extension elements  5118   a ,  5118   b ,  5118   c ,  5118   d ,  5118   e ,  5118   f . However, it should be appreciated that, in some implementations, all or some of the cartridge&#39;s and anvil&#39;s extension elements are not staggered with respect to one another. For example, the cartridge&#39;s and anvil&#39;s extension elements can be formed symmetrical, such that at least one of the anvil&#39;s extension elements overlaps with at least one of the cartridge&#39;s extension elements. 
       FIG. 40  additionally illustrates an end effector  5200  having a longitudinal axis  5 A 2 , which can have a configuration similar to that of the end effector  5100  ( FIGS. 35-37 and 39 ). Thus, similar to the end effector  5199 , the end effector  5200  has extension elements formed, in the example of  FIG. 40 , on both of the jaws  5202  (cartridge body) and  5204  (anvil). The extension elements formed on the cartridge body  5202  and anvil  5204  are collectively identified as extension elements  5206 ,  5208 , respectively. In this example, each of the cartridge body  5202  and anvil  5204  releasably retain thereon respective adjunct materials  5212 ,  5214  that are separately shown in  FIGS. 41 and 42 . The cartridge&#39;s extension elements  5206  and anvil&#39;s extension elements  5208  have attachment features, such as projections, configured to mate with corresponding mating features (e.g., openings) formed on adjunct materials  5212 ,  5214 , respectively. 
     As shown in  FIGS. 40-42 , the adjunct materials  5212 ,  5214  have shapes complementary to shapes of the cartridge body  5202  and anvil  5204 , respectively. In this example, the extension elements  5206  formed on the cartridge body  5202  are staggered with respect to the extension elements  5208  formed on the anvil  5204 . In a similar manner, the extension elements of the adjunct material  5212  are staggered with respect to the extension elements the adjunct material  5214 . Thus,  FIGS. 41 and 42  illustrate that, while the anvil&#39;s adjunct material  5214  has extension features  5224   a ,  5224   b  along an axis  5 B 1  (also shown in  FIG. 40 ), the cartridge body&#39;s adjunct material  5212  does not have any extension elements formed along the axis  5 B 1 . However, the cartridge body&#39;s adjunct material  5212  has extension elements  5222   a ,  5222   b  formed along an axis  5 B 2  (also shown in  FIG. 40 ), whereas the anvil&#39;s adjunct material  5214  does not have extension elements formed along the axis  5 B 2 . 
     An implantable adjunct configured to be releasably retained over a jaw of an end effector can be made from a variety of different materials described herein. For example, as discussed above, the adjunct can be formed from one or more of a film, foam, an injection molded thermoplastic, a vacuum thermoformed material, a fibrous structure, and hybrids thereof. The adjunct can also include one or more biologically-derived materials and one or more drugs. Furthermore, in the described implementations, one or more portions of the adjunct can have different properties. For example, the areas configured to be superimposed over the extensions features formed on a jaw can be configured differently from other areas of the adjunct. 
     A jaw (such as a cartridge body or an anvil) having extension elements and an adjunct material having a shape complementary to that jaw can have other features formed thereon for mating between these components. For example, in some implementations, the jaw can have attachment features in the form of recesses, through openings, or other types of features formed in the corresponding extension elements of the jaw and configured to mate with respective features formed on the adjunct material. 
     In some implementations, the opposed jaws of the end effector can have different types of adjunct materials releasably retained thereon. Furthermore, the same or different types of adjunct materials can be coupled to the opposed jaws using the same or different techniques. For example, one adjunct material can be attached to one of the jaws via mechanical features (e.g., projections on the jaw and openings on the adjunct, as discussed above), whereas another adjunct material can be attached to the opposed jaw using a suitable adhesive material. 
     In some embodiments, a cartridge body (e.g., part of a reloadable unit) can have an adjunct material attached thereon via an adhesive material, while another adjunct material can be attached to the anvil using mechanical feature, such as the projections on the jaw and openings on the adjunct. The cartridge body can be manufactured with a suitable adjunct material already retained thereon. At the same time, an adjunct material can be attached to the anvil of an end effector during surgery. 
     In some implementations, the anvil of an end effector can have mating features in the form of female features formed on the extensions of the anvil extending beyond the anvil&#39;s nominal perimeter. The female features, configured to mate with complementary features formed in an adjunct material configured to be releasably retained on the anvil, can be shaped as openings, pockets, cleats, etc. The adjunct material&#39;s mating features can be, for example, hooks, snaps, barbs, features having expandable elements (e.g., tree- or umbrella-like features) that can releasably mate with the pocket-type openings in the anvil. Furthermore, in some implementations, the anvil can have one or more three-dimensional pockets that allow an overmold feature of the adjunct to be releasably retained thereon. The overmold feature can be, for example, a projection molded into the three-dimensional pocket. It should be appreciated that at least on of the jaws of the end effector and an adjunct configured to releasably mate with that jaw can also have these features additionally or alternatively to the features described in connection with  FIGS. 35-42 . 
     Furthermore, in some embodiments, one or both of the jaws of the end effector may not have extension features formed thereon. In such embodiments, attachment features can be formed on an end effector&#39;s jaw within a nominal perimeter of the jaw.  FIGS. 43 and 44  illustrate an example of such an embodiment providing an anvil  5300  of an end effector having female features formed thereon for mating with an adjunct material  5310  that has corresponding mating features. The anvil  5300  has a tissue-contacting surface  5302  having a plurality of staple-forming pockets or cavities  5304 . The staple-forming cavities  5304  can form various patterns on the tissue-contacting surface  5302 . In this example, the staple-forming cavities  5304  are arranged in six rows extending along a longitudinal axis  5 A 3  of the anvil  5300 . As shown in  FIG. 43 , the tissue-contacting surface  5302  has attachment features  5316   a ,  5316   b ,  5316   c ,  5316   d  formed at a distal end  5300   d  of the anvil  5300  between adjacent staple-forming cavities. As shown, in this example, the attachment features  5316   a ,  5316   b ,  5316   c ,  5316   d  are formed in a row that is generally perpendicular to a longitudinal axis  5 A 3  of the anvil  5300 . 
       FIG. 44  illustrates by way of example two adjacent staple-forming cavities  5312   a ,  5314   a  having the attachment feature  5316   a  therebetween, which is in the form of an overmold cleat or pocket. Thus, the attachment feature  5316   a  and other similar attachment features are formed on the anvil&#39;s tissue-contacting surface  5302  by overmolding a suitable polymeric material (or a polymer blend or a copolymer) between adjacent staple-forming cavities at selected locations on the tissue-contacting surface  5302 . The attachment features  5316   b ,  5316   c ,  5316   d , as well as other attachment features formed on the tissue-contacting surface  5302 , can be formed in a similar manner and are not shown in detail. 
       FIG. 44  also illustrates that the adjunct material  5310  (which is shown partially in  FIG. 43 ) has a mating feature  5318   a  configured to be received within the pocket  5316   a . The mating feature  5318   a  can be in the form of an expandable (e.g., umbrella-like) mating feature extending through a thickness of the adjunct  5310  and a portion of which expands upon being inserted into the pocket  5316   a . The pocket  5316   a  and the mating feature  5318   a  are configured to mate such that, when staples are ejected from a cartridge and formed against the staple-forming cavities, the mating features  5318   a  are caused to be disengaged from the pocket  5316   a.    
     As shown in  FIG. 44 , the mating feature  5318   a  can be associated with the adjunct such that its top portion  5319  seats on one side above the surface of the adjunct  5310 , its mid-portion  5321  penetrates through the adjunct&#39;s surface and extends toward the opposite side of the adjunct that comes in contact with the anvil&#39;s tissue-contacting surface  5302 , and its expandable bottom portion  5323  is disposed on the opposite side of the adjunct, within the pocket  5316   a . The expandable portion  5323  of the mating feature  5318   a  can have one or more portions (e.g., arms, wings, prongs, snaps, etc.) that are configured to expand when load is applied to the top portion  5319 . 
     In use, the adjunct material  5310  is brought in proximity to the tissue-contacting surface  5302  and force can be applied to the adjunct material  5310  to cause the mating feature  5318   a  to be received within the pocket  5316   a  such that the expandable portion  5323  is received within the pocket  5316   a  and expands to thereby releasably retain the adjunct  5310  over the tissue-contacting surface  5302 . It should be appreciated that the mating feature  5318   a  can have other configurations that allow this feature to be used to releasably retain the adjunct on the jaw. The adjunct&#39;s mating features can have a changeable configuration, e.g., such that at least a portion of the feature expands, as the exemplary mating feature  5318   a  in  FIG. 44 . As another variation, the mating feature can be in the form of a hook or other non-expandable feature configured to be received within a recess in a jaw. The load can be applied to the adjunct  5310  manually, or using a loader or applicator member which can be removably coupled to the end effector or removably coupled to the adjunct  5310 . In some embodiments, the adjunct  5310  can have an applicator (e.g., in the form of a frame of a suitable configuration disposed over the adjunct) for applying load thereto to be coupled to the adjunct  5310 . During a surgical procedure, such applicator can be utilized to cause the adjunct  5310  to be releasably retained over the jaw. 
       FIG. 43  shows that, besides the attachment features  5316   a ,  5316   b ,  5316   c ,  5316   d , the tissue-contacting surface  5302  also attachment features  5320   a ,  5320   b ,  5320   c ,  5320   d  formed at a mid-portion  5300   m  of the anvil  5300 . The tissue-contacting surface  5302  also has attachment features  5322   a ,  5322   b ,  5322   c ,  5322   d  formed at a proximal portion  5300   p  of the anvil  5300 , the locations of which are shown schematically in  FIG. 43  as these features are obscured by the adjunct  5310 . Additionally, the tissue-contacting surface  5302  has proximal-most attachment features  5324   a ,  5324   b  (obscured by the adjunct  5310 ), which locations are shown in  FIG. 43 . The attachment features  5324   a ,  5324   b  are disposed at opposite sides of an anvil knife channel  5308  extending between distal and proximal ends  5300   d ,  5300   p  of the anvil  5300 . 
     The mid-portion attachment features  5320   a ,  5320   b ,  5320   c ,  5320   d  and the proximal attachment features  5322   a ,  5322   b ,  5322   c ,  5322   d  are arranged in two respective rows generally perpendicular to the longitudinal axis  5 A 3  of the anvil  5300 . As in this example, the attachment features can be located symmetrically with respect to the anvil knife channel  5108 . Regardless of its specific location, each of the attachment features is configured to releasably mate with at least one mating feature formed on the adjunct material. Thus,  FIG. 43  schematically shows that the proximal attachment features  5322   a ,  5322   b ,  5322   c ,  5322   d  (obscured in  FIG. 43 ) are configured to mate with respective adjunct&#39;s mating feature collectively indicated as features  5326 . These mating features can be configured similar to the feature  5318   a  shown in  FIG. 44 , or in another way. 
     It should be appreciated that the attachment features in  FIG. 43  are shown to form three rows by way of example only, as attachment features can be formed on a tissue-contacting surface of a jaw at any desired locations, so as to form various patterns. Also, eight attachment features are shown by way of example, as any number of the attachment features can be formed on the jaw&#39;s tissue-contacting surface. Furthermore, although the anvil  5300  is shown in  FIGS. 43 and 44 , in some implementations, features similar to those shown in  FIGS. 43 and 44  can be formed on a cartridge body of an end effector. Also, the cartridge body and the anvil of an end effector can have respective adjuncts releasably coupled thereto via different techniques. For example, the cartridge body can have extension elements with attachment features as shown in  FIGS. 35-37  (and in  FIGS. 39 and 40 ), whereas the anvil can have openings or pockets as shown in  FIGS. 43 and 44 , or vice versa. 
     Methods and Systems for Mating Constructible Adjunct Materials with End Effectors 
     Various exemplary devices, systems, and methods for releasably retaining an adjunct material on one or both jaws of an end effector of a surgical instrument are described herein. One or both of the opposed jaws can have retaining members formed thereon that are configured to mate with an adjunct material. 
     In some implementations, an adjunct material can be releasably retained on a jaw of an end effector in a secure manner, such that a possibility of the adjunct material prematurely slipping off the jaw is decreased or eliminated. In this way, the adjunct is securely coupled to the jaw while a surgeon manipulates the end effector during a surgical procedure. The adjunct remains coupled to the jaw until it is separated from the jaw and transferred to a treatment site in a patient, for example, when staples are deployed and/or when movement of a cutting element causes the adjunct to separate from the jaw. In such implementations, the adjunct material can be coupled to a jaw of an end effector using one or more contractible attachment features. The contractible attachment features, which are configured to couple the adjunct material with retaining members or other features of the jaw, can be features formed separately from the adjunct material. Additionally or alternatively, the contractible attachment features can be interwoven into or otherwise coupled to adjunct material. 
     In some embodiments, the contractible attachment feature can be in the form of one or more strands of a shrinkable polymer. The strands can be disposed on the adjunct material and/or they can be passed through the adjunct material in one or more locations. Furthermore, in some embodiments, the attachment feature can be in the form of a plurality of polymer strands interwoven into the adjunct material. The attachment features can be formed from any suitable material(s). For example, in some implementations, they can be formed from polydioxanone (PDO) or from other material(s) having a melting temperature that is lower than that of the adjunct material. 
     Regardless of the specific configuration of the contractible attachment features and the materials from which they are formed, each attachment feature can be configured to be transitioned from an original, non-contracted configuration to a contracted configuration under application of heat. The attachment feature can be engaged with the adjunct material, and contraction of the attachment feature is effective to couple the adjunct material with retaining members formed on the jaw. Adjunct materials can be releasably coupled to one or both jaws of an end effector of a surgical instrument using the contractible attachment features described herein. 
       FIG. 45  illustrates an example of a jaw of an end effector that has an adjunct material releasably secured thereto using contractible attachment features.  FIG. 45  shows a portion of an end effector  6100  of a surgical instrument configured to be coupled to a distal end of an elongate shaft of the surgical instrument (not shown). The end effector  6100  can generally include components similar to those described with regard to  FIGS. 1-4 , and can also include features and/or components that enable adjuncts to be releasably attached thereto. Thus, similar to surgical staplers  10  ( FIG. 1 ) and  50  ( FIG. 4 ), the end effector  6100  includes an upper jaw having an anvil and an lower jaw having a cartridge body (not shown), with only the upper jaw  6102  being shown in  FIG. 45 . The lower jaw can generally include a staple cartridge that has a plurality of staple-holding cavities configured to seat staples therein, the staple-holding cavities opening on a tissue-facing surface of the cartridge. 
     As shown in  FIG. 45 , the upper jaw  6102  having an anvil  6104  can have an adjunct material  6124  (shown partially transparent) releasably retained on a tissue-facing surface  6118  of the anvil  6104  using one or more contractible attachment features  6128 , as discussed in more detail below. As schematically shown in  FIG. 45 , the anvil  6104  has staple-forming cavities  6116  formed on the tissue-facing surface  6118  thereof. As also shown, the tissue-facing surface  6118  has a knife channel  6108  configured to receive a cutting element (e.g., a knife) as it moves distally therethrough. 
     In the example illustrated, the anvil  6104  is shown in the form of a modular jaw that includes an anvil plate  6106  releasably attached to the anvil  6104  via an adapter  6110 . The anvil plate  6106  is a substantially rigid surface against which staples can be formed. In the illustrated example, the adapter  6110  can include mating features  6112  configured to mate with corresponding anvil features  6114  formed along a side of the anvil  6104  facing the opposed jaw, thereby ensuring an alignment between the anvil plate  6106  and the cartridge-facing surface of the anvil  6104 . The adapter  6110  can be, e.g., an elastomer or other compliant member, and it can be overmolded, adhered to, or otherwise coupled to the anvil plate. The adapter  6110  can be used to releasably couple the anvil plate  6106  to the anvil  6104  in a variety of ways. For example, the adapter  6110  can snap into the jaw  6102 . The modular configuration can allow interchangeably using anvil plates having different staple-forming features with the same jaw. The described techniques can be used in conjunction with various end effectors having modular jaws. For example, such end effectors are described in U.S. patent application Ser. No. 15/435,986 entitled “Surgical End Effector Adjunct Attachment,” filed on even date herewith, and U.S. patent application Ser. No. 15/385,953 entitled “Methods of Stapling Tissue” filed on Dec. 21, 2016, the entire contents of which are incorporated by reference herein. 
     In the example of  FIG. 45 , the tissue-facing surface  6118  is in the form of the surface of the anvil plate  6106  facing the adjunct material  6124 . However, it should be appreciated that the modular anvil  6104  having the anvil plate  6106  is shown by way of example only, and that the described techniques can be used to releasably couple an adjunct material to any type of a jaw, including a jaw having a tissue-facing surface non-removably coupled thereto. 
     Regardless of its particular configuration, the tissue-facing surface  6118  of the anvil  6104  has at least first and second retaining members  6122   a ,  6122   b  that are configured to couple the adjunct material  6124  to the anvil  6104 . The first retaining member  6122   a  is disposed at one side of the tissue-facing surface  6118  in proximity to one edge  6109   a  of the tissue-facing surface  6118 , and the second retaining member  6122   b  is disposed at another, opposed side of the tissue-facing surface  6118  in proximity to another, opposed edge  6109   b  thereof. In this way, the first and second retaining members  6122   a ,  6122   b  are disposed at opposed sides of the knife channel  6108 . 
     The retaining members  6122   a ,  6122   b  can have a variety of different configurations. In the example illustrated, they are in the form of generally cylindrical posts extending from the tissue-facing surface  6118 . However, the retaining members  6122   a ,  6122   b  can have other shapes, as the described implementations are not limited in this respect. For example, the retaining members can have an hour glass shape, a bulbous or widened end region, or any other shape. Additionally or alternatively, the retaining members can be curved and/or angled in any suitable manner. For example, as shown in  FIG. 45 , the retaining members  6122   a ,  6122   b  can be slightly angled away from one another towards respective edges  6109   a ,  6109   b  of the tissue-facing surface  6118 . Such configuration can assist in engaging the one or more attachment features  6128  with the retaining members  6122   a ,  6122   b , as discussed below. The retaining members can be configured in any other manner and have any other retaining features, such as, for example, one or more teeth, notches, grooves, undercuts, roughness areas, etc., that can facilitate retention of the attachment features  6128  at the retaining members. 
     Although two retaining members  6122   a ,  6122   b  are shown in  FIG. 45 , the tissue-facing surface  6118  can have any other number of retaining members (e.g., one or greater than two) configured to couple an adjunct thereto. Furthermore, the retaining members can be formed at various locations on the tissue-facing surface  6118  of the anvil  6104 . For example, in some embodiments, two or more retaining members can be formed along each edge  6109   a ,  6109   b  of the tissue-facing surface  6118 . The retaining members can be formed at any suitable distance from one another that allows securely retaining the adjunct material on the jaw&#39;s tissue-facing surface. In addition, the retaining members can be disposed symmetrically with respect to the knife channel  6108  or other features of the tissue-facing surface  6118 , or they can be formed at various other ways on the surface  6118 . 
     As shown in  FIG. 45 , in the example illustrated, each of the retaining members  6122   a ,  6122   b  is formed outside of the area of the tissue-facing surface  6118  having the staple-forming cavities  6116 . However, in some implementations, one or more of the retaining members can be formed within the area having the staple-forming cavities  6116 . 
     As mentioned above, the adjunct material  6124  is configured to releasably couple with the anvil  6104  using at least one contractible attachment feature  6128  configured to be transitioned from an original, non-contracted configuration to a contracted configuration under application of heat, as discussed in more detail below. The adjunct material  6124  can couple with the anvil  6104  in a secure manner, which helps ensure that the adjunct  6124  remains coupled to the anvil  6104  while the end effector  6100  is manipulated as desired using a surgical procedure. The adjunct  6124  is held in engagement with the anvil  6104  until an action, such as an activation of the end effector  6100  to release staples from its cartridge and/or an activation of a cutting element, is taken that causes the separation of the adjunct  6124  from the anvil  6104 . 
     To accommodate a contraction of the at least one contractible attachment feature  6128  that occurs as a result of heating, the adjunct material  6124  can be configured such that it assumes an appropriate shape and size once heating has occurred so as to couple the adjunct material  6124  to the jaw  6102 . For example, the adjunct material  6124  can be sized such that it extends beyond the perimeter of the tissue-facing surface  6118  of the anvil  6104  prior to heating, and adopts the appropriate size once heating has occurred. 
     The first and second retaining members  6122   a ,  6122   b  are configured to mate with respective mating features of the adjunct material  6124 . In particular, in the described implementation, the adjunct material  6124  includes openings  6126   a ,  6126   b  configured to receive the retaining members  6122   a ,  6122   b , respectively. In this example, the through openings  6126   a ,  6126   b  in the adjunct  6124  are generally round, though it should be appreciated that the openings  6126   a ,  6126   b  can have any other suitable shapes. 
     The openings  6126   a ,  6126   b  can have various sizes and configurations, and they can be disposed at various locations of the adjunct  6124 . For example, the openings  6126   a ,  6126   b  can be formed at locations of the adjunct material  6124  that correspond to the locations of the retaining members  6122   a ,  6122   b  formed on the anvil plate  6106 . 
     In the described implementations, as mentioned above, the retaining members  6122   a ,  6122   b  couple the adjunct  6124  to the anvil  6104  by engaging one or more contractible attachment features  6128  configured to be transitioned from an original, non-contracted configuration to a contracted configuration under application of heat. The contractible attachment features  6128  can be in the form of one or more strands of a shrinkable polymer, which can be coupled to the adjunct material  6124  at one or more locations. The adjunct material  6124  and the at least one contractible attachment feature  6128  can be made from a variety of materials. For example, in at least some embodiments, the adjunct  6124  can be made from VICRYL® (polyglactin  910 ) material, whereas the contractible attachment feature  6128  can be in the form of one or more PDO strands that can be bioabsorbable and/or biodegradable. Any other materials can be used additionally or alternatively. One or more of the strands can be coupled (e.g., removably) to the adjunct material  6124 . The PDO has a relatively low melting temperature, which is advantageous for its use in conjunction with adjuncts and attachment features. For example, the PDO has a melting temperature of 105 C°. Heat can be applied for, for example, from 30 seconds to several minutes to cause the attachment feature  6128  to transition into the contracted configuration. 
     Referring to  FIG. 45 , the contractible attachment features  6128  can be engaged with the adjunct material, and contraction of the contractible attachment feature  6128  is effective to couple the adjunct material  6124  with the retaining members  6122   a ,  6122   b . For example, the adjunct material  6124  can be disposed over the tissue-facing surface  6118  of the jaw  6102  such that adjunct&#39;s openings  6126   a ,  6126   b  receive the retaining members  6122   a ,  6122   b . In some embodiments, the adjunct material  6124  can be applied to the jaw using a loader member, as discussed below. Further, the adjunct material  6124  is associated with the at least one contractible attachment feature  6128  which can be disposed over the adjunct material  6124  such that the attachment feature  6128  is engaged with the retaining members  6122   a ,  6122   b . The attachment feature  6128  can be coupled to the adjunct material  6124 —e.g., it can be in the form of one or more strands of a shrinkable polymer, one or more of which are passed through at least one portion of the adjunct  6124 . Heat can be applied to cause at least a portion of the attachment feature  6128  to contract to thereby cause the adjunct material  6124  to couple with the retaining members  6122   a ,  6122   b  using the attachment feature  6128 . In particular, the attachment feature  6128  can be caused to transition from the original, non-contracted configuration to the contracted configuration such that, in the contracted configuration, the attachment feature  6128  is coupled to retaining members  6122   a ,  6122   b  and thereby retains the adjunct material  6124  in secure (albeit releasable) engagement with the retaining members  6122   a ,  6122   b  and thus with the anvil  6104 . 
     It should be appreciated that the adjunct materials can be attached to an end effector using various other approaches. For example, the U.S. Pat. App. No. 614/871,078 entitled “Tubular Absorbable Constructs” filed on Sep. 30, 2015, which is incorporated by reference herein in its entirety, describes another approach. 
       FIGS. 46A and 46B  illustrate an embodiment of an adjunct material or adjunct  6224  that can be disposed on a tissue facing surface of a jaw (not shown), such as a jaw having an anvil (e.g., anvil  6104  in  FIG. 45 ). It should be appreciated that the jaw can also be a jaw having a cartridge. In this example, the adjunct  6224  has a plurality of attachment features  6228  associated therewith. 
     The attachment features  6228  can be in the form of two or more attachment features. The attachment features  6228  can be, for example, strands of a shrinkable polymer, such as PDO strands that can pass through at least one portion of the adjunct material, at one or more points. For example, the PDO strands can be woven, knitted, braded into the adjunct  6224 , or otherwise associated with the adjunct  6224 . As shown by way of example, one or more of the attachment features  6228  can be coupled to the adjunct  6224  at points  6229   a ,  6229   b , though it should be appreciated that the attachment feature  6228  can be coupled to the adjunct  6224  at any number of points at any locations in the adjunct  6224 . In some cases, the adjunct  6224  can be manufactured such that the attachment features  6228  are created during the manufacturing process and are thus part of the adjunct  6224 . In other embodiments, however, some or all of the attachment features  6228  can be separate threads coupled to the adjunct  6224 . 
     In use, the adjunct  6224  can be mated with the jaw via retaining members  6222   a ,  6222   b  formed on the jaw and mating with openings  6226   a ,  6226   b  in the adjunct  6224 . As shown in  FIG. 46A , before the adjunct  6224  is securely and releasably coupled to the jaw, the attachment features  6228  are in a non-contracted configuration such that they form one or more loops that encompass both of the retaining members  6222   a ,  6222   b . As shown, the loops can be disposed in a relatively loose manner around the retaining members  6222   a ,  6222   b . As discussed above, the attachment features  6228  can be associated with the adjunct in a variety of ways. For example, they can be passed through one or more portions of the adjunct  6224 . Additionally or alternatively, the attachment features can be disposed over, and coupled to the adjunct using, e.g., an adhesive. 
     As illustrated schematically in  FIG. 46B , the adjunct  6224  can be secured to the jaw by applying heat to a region  6230  that encompasses a portion of the attachment features  6228 . Under the application of heat, the attachment features  6228  transition from the non-contracted configuration (shown in  FIG. 46A ) to a contracted configuration as shown in  FIG. 46B . In the contracted configuration, the attachment features  6228  can be arranged such that one or more loops are engaged around the retaining members  6222   a ,  6222   b  and thereby releasably retain the adjunct material  6224  over the jaw. In this way, in the contracted configuration, the loops of the attachment features  6228  are held in tension more tightly around the retaining members  6222   a ,  6222   b  than in the non-contracted configuration. Also, as mentioned above, the retaining members  6222   a ,  6222   b  are configured to have retaining features that facilitate engagement of the attachment features  6228  therewith. 
     In the example shown in  FIG. 46B , when heat is applied to a region encompassing a portion of the attachment features  6228 , the portions of the attachment features  6228  in that region contract. The heat can be applied to the attachment features  6228  in a variety of ways, as discussed in more detail below. The contraction results in the attachment features  6228  and the through openings  6226   a ,  6226   b  being tensioned around the retaining members  6222   a ,  6222   b  which thus releasably retain the adjunct  6224  over the jaw. Thus,  FIGS. 46A and 46B  illustrate that the area of the adjunct  6224  is reduced to some degree after the heat has been applied.  FIGS. 46A and 46B  also illustrate that a shape of the openings  6226   a ,  6226   b  formed the adjunct  6224  changes when the adjunct  6224  is in the contracted configuration. In particular, the openings  6226   a ,  6226   b  become more stretched as the material from which the adjunct  6224  is formed as pulled towards the middle of the adjunct  6224  due to the contraction of the attachment features  6228 , which is also shown by arrows  6223   a ,  6223   b  in  FIG. 46B . When the staples are fired and a cutting element (e.g., a knife) is activated, the attachment features  6228  are cut, thus allowing the adjunct  6224  to separate from the jaw. 
     It should be appreciated that the implementation in  FIGS. 46A and 46B  is shown by way of example only. Thus, the attachment features  6228  can be wrapped around the retaining members in many various ways. For example, as in the example illustrated, the attachment features  6228  can form one or more loops in a substantially oval pattern. As another example, the attachment features can be arranged in a figure-eight pattern around the retaining members, or they can be arranged such that one or more portions form one or more crisscross patterns over the adjunct. Also, the attachment feature(s) can be arranged around the retaining members in a substantially random way. As mentioned above, one or more of the attachment features can be coupled to (e.g., woven through) the adjunct at one or more locations. Moreover, in some implementations, one or more of the attachment features can be coupled to or interconnected with one another. 
     Furthermore, in some embodiments, the attachment features are not engaged with the retaining members. For example, the adjunct can have openings formed around its perimeter some or all of which can be engaged with (e.g., receive therethrough) the retaining members of the jaw. The contractible attachment features, which can be coupled to the adjunct in any suitable manner (e.g., passed through the adjunct one or more times, attached used an adhesive, etc.), can be disposed in a certain way, e.g., across the middle of the adjunct, such that, when they are exposed to heat, they constrict and cause the two sides of the adjunct to be pulled together. Depending on the configuration of the adjunct and the attachment features, the adjunct will constrict or deform as a result of the application of heat in a suitable manner. 
     In the example shown in  FIGS. 46A and 46B , the adjunct  6224  is secured to the tissue-facing surface of the jaw using multiple attachment features  6228 . However, in some embodiments, a single continuous attachment feature can be used to secure an adjunct to a jaw of an end effector. Such embodiments can be used, for example, if limited interconnection between the adjunct and the attachment feature is desired. In other words, the attachment feature can be coupled to the adjunct in fewer locations as compared to implementations in which two or more attachment features are used. 
       FIGS. 47A and 47B  illustrate an embodiment in which a continuous attachment feature  6328  is used to couple an adjunct material or adjunct  6324  to a jaw (not shown), such as a jaw having an anvil (e.g., anvil  6104  in  FIG. 45 ) or a jaw having a cartridge. In this example, the attachment feature  6328  is a relatively long continuous feature disposed over a portion of the adjunct  6324  as shown in  FIG. 47A . 
     As shown, the adjunct  6324  is disposed over the jaw such that retaining members  6322   a ,  6322   b  formed on the jaw are mated with through openings  6326   a ,  6326   b  in the adjunct  6324 . As also shown, the attachment feature  6328  can form one or more loops that encompass the retaining members  6322   a ,  6322   b . As shown by way of example, the attachment feature  6328  can be coupled to the adjunct  6324  at a point  6329 , though it should be appreciated that the attachment feature  6328  can be coupled to the adjunct  6324  at any number of points at any locations of the adjunct  6324 . The attachment feature  6328  can be woven into, knitted through, stitched through, or otherwise coupled to the adjunct  6324 . In addition, in some embodiments, one or more portions of the attachment feature  6328  can be coupled one another, e.g., using an adhesive. Additionally or alternatively, some of the portions can be tied, twisted, bonded together, etc. 
     In the example illustrated, as shown in  FIG. 47B , when heat is applied to a region  6330  encompassing a portion of the attachment feature  6328 , one or more portions of the attachment feature  6328  contract. As the contraction occurs, the attachment feature  6328  is brought closer towards the retaining members  6322   a ,  6322   b  such that the material of the attachment feature  6328  engages more tightly around the retaining members  6322   a ,  6322   b , thereby releasably retaining the adjunct  6324  over the jaw. In other words, the attachment feature  6328  is held in tension around the retaining members  6322   a ,  6322   b . When the staples are fired and a cutting element (e.g., a knife) is activated, the attachment feature  6328  is cut to thus allow the adjunct  6324  to separate from the jaw. 
     In this way,  FIGS. 46A, 46B, 47A, and 47B  illustrate that the adjuncts  6224 ,  6324  can be securely coupled to a jaw in a manner than allows manipulating the jaw as desired during a surgical procedure. A risk of the adjunct slipping off or otherwise being unintentionally and prematurely separated from the jaw is reduced or eliminated. 
     In the examples of  FIGS. 46A, 46B, 47A, and 47B , the attachment features can be formed from any suitable materials. For example, they can be in the form of one or more PDO strands. A density of the PDO strands can vary throughout the attachment features and thus throughout the adjunct to which the feature(s) are attached. In this way, the degree of contraction of the attachment feature(s) varies in different parts of the adjunct. In some cases, elongate PDO strands can be woven throughout the entire adjunct such that more uniform adjunct contraction can be achieved. The PDO strands can also be wrapped around the retaining members to ensure that they effectively engage the retaining members when heat is applied and contraction occurs. As another example, the attachment features can be separate from the adjunct. In such cases, upon heating, the attachment features contract, and become secured in tension between the retaining members, thereby holding the adjunct in place, but the contraction of the attachment features may not have an impact on the configuration of the adjunct. Alternatively, as discussed above, the attachment features can be attached to the adjunct at certain attachment points, which can be based on the desired configuration of the adjunct and the amount of contraction. 
     In the described embodiments, one or more attachment features can be used to releasably engage an adjunct with a jaw of an end effector using heat. The heat can be applied in a variety of ways. For example, in some embodiments, heat can be applied using a loader that is configured to apply the adjunct to the jaw.  FIGS. 48A and 48B  illustrate an example of a loader  6400  configured to apply an adjunct to a tissue-facing surface of a jaw.  FIG. 48A  shows a top view of the loader  6400 , whereas  FIG. 48B  shows a cross-sectional view of the loader  6400 . 
     As in the illustrated example, the loader  6400  in the form of a generally rectangular frame-like holder configured to releasably couple one or more adjuncts to one or both jaws of the end effector (not shown). In the illustrated example, the loader  6400  is in the form of a first (e.g., top) and second (e.g., bottom) generally rectangular housings  6402 ,  6404  coupled to one another e.g., via a coupling  6406 , as shown in  FIG. 48B . In this example, the loader  6400  can be used to apply a single adjunct to a jaw. It should be appreciated however, that, in some embodiments, a loader like the loader  6400  or a similar loader, can be used to apply a respective adjunct to each jaw of an end effector. 
     The loader  6400  includes at least one heating component  6408  configured to be activated to apply heat to attachment features, as described below. The heating component  6408  can have various configurations. For example, as shown in  FIGS. 48A and 48B , the heating component  6408  includes a resistive heating element  6414  in the form of a wire. The heating element  6414  is connected to a power source  6416 . In the illustrated example, the heating element  6414  includes higher resistance portions  6418  along its length. The locations of the higher resistance portions  6418  can correspond to regions on an adjunct to which heat is desired to be applied, e.g. region  6230  ( FIG. 46B ) or region  6330  ( FIG. 47B ). Thus, power can be applied to the heating element  6414  to cause localized heating near the higher resistance portions  6418 . In some embodiments the heating element can include a switch  6420  that closes the circuit and allows current to flow through the heating element. The switch  6420  can be operated using a suitable trigger on the loader  6400  (e.g., a button), though the heating element  6414  can be activated in other suitable ways. The heat generated by the higher resistance portions  6418  causes the attachment features that are engaged with the adjunct to contract to effectively couple the adjunct with retaining members of the jaw, thereby releasably retaining the adjunct over the tissue-facing surface of the jaw. 
     The heating component  6408  can be of any suitable type. For example, the heating component  6408  can be made of a rigid material, e.g., ceramic, that is coated with an elastic or compliant material. In some embodiments, the heating component  6408  can be in the form of a resistive wire embedded into silicone, e.g., such that the silicone is cured around the resistive wire. The resistive wire is configured to effect the heating, whereas the silicone allows for some degree of compliance when clamping a stapler onto the loader. As shown in  FIG. 48B , the heating component  6408  can be coupled to the housings  6402 ,  6404  via connecting features  6410 , e.g., brackets. 
     The loader  6400  and heating component  6408  can generally be configured such that an adjunct (not shown) can be placed on a surface, e.g., an upward facing surface  6412  of the heating component as shown in  FIG. 48B , and the jaws of the end effector can clamp over the heating component and adjunct. Although not illustrated, the loader  6400  and/or heating component  6408  can include retaining features that can releasably secure adjuncts to surfaces  6412  and  6413  such that the adjuncts can be secured to both jaws of an end effector simultaneously. For example, the heating component  6408  can have small posts or hooks that can grip the adjuncts to releasably secure them to surfaces  6412 ,  6413 . In one embodiment, the heating component  6408  is disposable and it is coupled to adjuncts secured to the surfaces  6412 ,  6413 . In such an embodiment, the loader  6400  is configured to receive a heating component  6408  with adjuncts attached thereto. The surgeon can load the heating component  6408  with the adjuncts into the loader  6400 , and attach the adjuncts to jaws of an end effector. 
     Furthermore, in some embodiments, the heating component  6408  (or a heating component having another configuration) can be in the form of two heating components disposed in the removable loader such that each of the heating components is configured to apply heat to a different adjunct that can be associated therewith (e.g., via the loader or manually). In such implementations, with reference to  FIG. 48B , for example, first and second adjuncts are placed on the surfaces  6412 ,  6413 , respectively, and heat can be applied to the adjuncts using respective heating components associated with the surfaces  6412 ,  6413 . 
     Regardless of the specific way in which the heating component  6408  is associated with the loader  6400 , the loader  6400  can be used to both deliver the adjunct to the jaw (such that the adjunct is transferred from the loader to the jaw) and to apply heat to the adjunct. In use, the loader can be placed between the jaws of the end effector that are in an open configuration. The jaws can then be clamped over the loader  6400  to thereby clamp over the heating component  6408  and the adjunct such that the adjunct is transferred onto the jaw and retaining members on the jaw enter through openings on the adjunct, as illustrated, e.g., in  FIGS. 46A and 47A . At least one attachment feature can be engaged with the adjunct, e.g., as shown for attachment features  6228 ,  6328  and adjuncts  6224 ,  6324  in  FIGS. 46A and 47A , respectively. The heating element  6414  can be activated in a suitable manner such that heat applied therefrom to the at least one attachment feature can cause the attachment feature to contract, which causes the adjunct material to couple with the first and second retaining members. 
     In some embodiments, the act of clamping the jaws onto the heating component closes the switch  6420 , thereby allowing current to flow through the heating element. Once the adjunct is secured to the jaw as desired, the jaws can be opened and removed from the heating component which allows the switch  6420  to open, thereby stopping the flow of current within the heating element  6414 . 
     In other implementations, an adjunct may not be associated with a loader, such as the loader  6400 , and the loader can be used only to apply heat to the adjunct (and thus to at least one attachment features). In such implementations, an adjunct is placed onto a tissue-facing surface of a jaw, and attachment features engaged with or disposed over the adjunct is looped around jaw&#39;s retaining members as desired to loosely secure the adjunct to the end effector. The end effector is then be clamped onto the loader with the heating component  6408  of the loader  6400 , and the heating element  6414  is powered, thereby causing localized heating near the high resistance portions  6418  of the heating element  6414 . The heat from those portions  6418  causes the attachment features that are engaged with the adjunct to contract to effectively couple the adjunct with the retaining members, thereby releasably retaining the adjunct over the tissue-facing surface of the jaw. 
     It should be appreciated that the loader  6400  is shown by way of example only. In some embodiments, a loader can use a chemical reaction to supply heat to the attachment features. For example, the loader can generally be similar to loader  6400 , but rather than using a heating component that includes a resistive heating element, the loader can use a heating component including one or more fluid or crystalline structures. By way of example, the heating element can include a number of fluid or crystalline structures that can release heat when they come in contact with each other. In some implementations clamping jaws of an end effector onto the heating component can cause internal pockets containing fluid or crystalline structures to crack, thereby allowing their internal substances to combine. When the substances combine, the mixture undergoes an exothermal chemical reaction that releases heat. The heating component can be configured such that the chemical heating elements are in the desired locations, and wherein cracking the heating elements only breaks an internal barrier and does not cause the substances to spill from the heating component. 
     Furthermore, in some embodiments, heat can be applied to an adjunct with at least one attachment feature pre-loaded thereon using a device different from a loader. For example, the adjunct can be disposed on a jaw of an end effector and heat can be applied thereto using an infrared heater, UV heater, heat gun, or any other device configured to provide heat. In some cases, the heating can be done by placing the end effector with the adjunct disposed thereon in a suitable oven, heated chamber, or other enclosure configured to apply heat. The separate heating devices can be used in embodiments in which the adjunct is pre-applied to the end effector&#39;s jaws during manufacture of the end effector. The loader, such as the loader  6400 , or a similar applicator (e.g., a small heating chamber) can be used in embodiments in which the adjunct is configured to be applied in the operating room by the surgeon or other person during or before a surgical procedure. 
     Regardless of the way in which heat is applied to the adjunct, a temperature of the heat and a duration of its application is selected so as to cause at least one attachment feature to contract and thus cause the adjunct to be attached to the jaw. For example, the heat can have a temperature of from about 6100 to about 130 degrees Celsius and it can be applied for, for example, from about 20 seconds to about 3 minutes to cause the attachment feature to transition into the contracted configuration. It should be appreciated, however, that a temperature in other ranges can be applied for any suitable time period. 
     In some applications, an adjunct can be formed such that a plurality of contractible attachment features are interwoven into the adjunct along a longitudinal axis of the adjunct and along an axis that is substantially perpendicular to the longitudinal axis of the adjunct.  FIGS. 49A and 49B  illustrate an example of such an adjunct. In particular,  FIGS. 49A and 49B  illustrate a portion of an end effector  6500  that is configured to have an adjunct  6524  coupled to a tissue-facing  6518  surface of a jaw, wherein the adjunct  6524  has contractible attachment features  6528  interwoven with the adjunct  6524  along a longitudinal axis  6 A and along a lateral axis  6 B that is substantially perpendicular to the longitudinal axis  6 A. 
     The end effector  6500  can generally include components similar to those described with regard to end effector  6100  ( FIG. 45 ). Thus, similar to the end effector  6100 , the end effector  6500  can include an upper jaw (not shown) having an anvil and a lower jaw having a cartridge body  6504 . The lower jaw includes the staple cartridge  6504  that has a plurality of staple-holding cavities  6516  configured to seat staples therein, the staple-holding cavities  6504  opening on a tissue-facing surface  6518  of the cartridge  6504 . The staple cavities can form a certain pattern on the tissue-facing surface  6518  of the cartridge  6504  which corresponds to a pattern of staple-forming cavities formed in the anvil. The cartridge  6504  includes first and second retaining members  6522   a ,  6522   b , located adjacent to opposed edges of the tissue-facing surface  6518 , and a knife channel  6508  extending between distal and proximal ends of the cartridge  6504 . 
     The retaining members  6522   a ,  6522   b  disposed on the tissue-facing surface  6518  of the cartridge  6504  are configured to releasably couple an adjunct material  6524  to the cartridge  6504 . The first retaining member  6522   a  is disposed at one side of the tissue-facing surface  6518  in proximity to one edge  6509   a  of the tissue-facing surface  6518 , and the second retaining member  6522   b  is disposed at another, opposed side of the tissue-facing surface  6518  in proximity to another, opposed edge  6509   b  thereof. In this way, the first and second retaining members  6522   a ,  6522   b  are disposed at opposed sides of the knife channel  6508 . 
     The retaining members  6522   a ,  6522   b  can have a variety of different configurations. In the example illustrated, they are in the form of generally cylindrical posts extending from the tissue-facing surface  6518 . However, the retaining members  6522   a ,  6522   b  can have other shapes, as the described implementations are not limited in this respect. For example, the retaining members  6522   a ,  6522   b  can be curved, have an hour glass shape, have a bulbous or widened end region, have notches, be angled toward the edges of the tissue-facing surface, have roughness features, etc. The retaining members can be configured in any manner suitable for assisting in retaining the adjunct on the jaw. Also, although two retaining members  6522   a ,  6522   b  are shown in  FIG. 49A , the tissue-facing surface  6518  can have any other number of retaining members (e.g., one or greater than two) configured to couple an adjunct thereto. Furthermore, the retaining members can be formed at various locations on the tissue-facing surface  6518  of the cartridge  6504 . For example, in some embodiments, two or more retaining members can be formed along each edge  6509   a ,  6509   b  of the tissue-facing surface  6518 . The retaining members can be formed at any suitable distance from one another that allows securely retaining the adjunct material on the jaw&#39;s tissue-facing surface. In addition, although in the illustrated implementations the retaining members protrude above the surface of the tissue-facing surface, in some embodiments, the retaining members can be in the form of recesses or other features disposed at least partially below the tissue-facing surface of the jaw. This can be done in implementations in which a reload includes reverse drivers. 
     As shown in  FIG. 49A , in the example illustrated, each of the retaining members  6522   a ,  6522   b  is formed outside of the area of the tissue-facing surface  6518  having the staple cavities  6516 . However, in some implementations, one or more of the retaining members can be formed within the area having the staple cavities  6516 . 
     The adjunct material  6524  is configured to releasably couple with the cartridge  6504  using a plurality attachment features  6528  configured to be transitioned from an original, non-contracted configuration to a contracted configuration under application of heat, as discussed in more detail below. The adjunct material  6524  couples with the cartridge  6504  in a secure manner, which helps ensure that the adjunct  6524  remains coupled to the cartridge  6504  while the end effector  6500  is manipulated as desired using a surgical procedure. The adjunct  6524  is held in engagement with the cartridge  6504  until an action, such as an activation of the end effector  6500  to release staples from its cartridge and/or an activation of a cutting element, is taken that causes the separation of the adjunct  6524  from the cartridge  6504 . 
     To accommodate a contraction of the at least one attachment feature  6528  that occurs as a result of heating, the adjunct material  6524  can be configured such that it assumes an appropriate shape and size once heating has occurred so as to couple the adjunct material  6524  to the cartridge  6504 . For example, the adjunct material  6524  can be sized such that it extends beyond the perimeter of the tissue-facing surface  6518  of the cartridge  6504  prior to heating, and adopts the appropriate size once heating has occurred. 
     The first and second retaining members  6522   a ,  6522   b  are configured to mate with respective mating features of the adjunct material  6524 . In particular, in the described implementation, the adjunct material  6524  includes a plurality of through openings  6526 , wherein at least first and second openings  6526   a ,  6526   b  of the openings  6526  are configured to be mated with the retaining members  6522   a ,  6522   b . It should be appreciated that, depending on the number of the retaining members, more than two of the openings  6526  can mate with respective retaining members. 
     The openings  6526  in the adjunct  6524  can have any suitable size and shape, including different sizes and shapes. In this example, the openings  6526  are generally square, though it should be appreciated that the openings  6526  can have any other suitable shapes. In the illustrated example, the attachment features  6528  can be woven through the openings  6526  as shown in  FIGS. 49A and 49B . Also, the openings  6526  can also be positioned and dimensioned to control the configuration of the adjunct and internal stress imposed upon the adjunct when heat is applied and the attachment features contract. The openings can be formed in the adjunct such that specific openings (e.g., openings  6526   a ,  6526   b ) are configured to receive corresponding retaining members. Alternatively, in some cases, when the adjunct is disposed over the jaw, the openings in the adjunct can “find” retaining members to mate with, and it may therefore not be necessary to make openings that specifically correspond to positions of the retaining members. 
     The contractible attachment features  6528  can be in the form of one or more strands of a shrinkable polymer, which can be coupled to the adjunct material  6524  at one or more locations. The adjunct  6524  can have any suitable number of attachment features interwoven into the adjunct  6524  such that at least one attachment feature is disposed along the longitudinal axis  6 A and at least one attachment feature is disposed along the lateral axis  6 B. In the example of  FIG. 49A , fours strands of shrinkable polymer are disposed along the longitudinal axis  6 A of the adjunct  6524  (two along each of the long sides) and two strands of shrinkable polymer are disposed along the lateral axis  6 B of the adjunct  6524  (closer to the distal end of the jaw  6504 ). However, it should be appreciated that the attachment features  6528  can be in the form of any suitable number of strands that can be coupled to the adjunct  6524  in any desired manner. For example, in one embodiment, one or more of the stands can be coupled to the adjunct  6524  so as to be diagonally disposed with respect to the adjunct  6524 . The strands can be coupled to the adjunct to be able to contract in a way so as to transition one or more portions of adjunct to a desirable shape and size. For example, the strands must be able to cause some of the openings in the adjunct to constrictably engage with the retaining members. In some cases, the same strand can be interwoven into the adjunct along the longitudinal axis  6 A as well as the lateral axis  6 B. 
     The adjunct material  6524  and the at least one contractible attachment feature  6528  can be made from a variety of materials. For example, in at least some embodiments, the adjunct  6524  can be made from VICRYL® (polyglactin  910 ) material, whereas the contractible attachment feature  6128  can be in the form of one or more PDO strands. Any other materials can be used additionally or alternatively. 
     In the described implementations, the retaining members  6522   a ,  6522   b  couple the adjunct  6524  to the cartridge  6504  by mating with two corresponding openings  6526   a ,  6526   b . When heat is applied, the attachment features transition from a non-contracted configuration to a contracted configuration and thereby causing the at least the openings  6526   a ,  6526   b  to constrict around the retaining members  6522   a ,  6522   b , as shown schematically in  FIG. 49B . Thus, in the contracted configuration, the attachment features  6528  are coupled to the retaining members  6522   a ,  6522   b  or cause the adjunct  6524  to couple to the retaining members  6522   a ,  6522   b . In this way, the adjunct material  6524  is retained in a secure and releasable engagement with the retaining members  6522   a ,  6522   b  and thus with the cartridge  6504 , as illustrated in  FIG. 49B . Heat can be applied to the adjunct  6524  with the attachment feature  6528  using a variety of techniques, as discussed above. For example, loader  6400  ( FIGS. 48A and 48B ), or any other device configured to provide heat can be used. 
     In the examples described above, an adjunct can be attached to a cartridge and/or anvil during manufacturing, or by a surgeon before or during a surgical procedure. The adjunct can be secured to the end effector using one or more shrinkable attachment features that can change their configuration under application of heat. In other embodiments, however, the adjunct can be releasably coupled to the jaw using other approaches that do not require application of heat. 
     Thus, in some embodiments, at least one first portion of an adjunct material or adjunct is configured to be reversibly stretched by an application of force. When the force is removed, the first portion transitions from a stretched configuration to a contracted configuration, thereby causing the adjunct material to engage a jaw of an end effector. The jaw can have one or more retaining features configured to mate with corresponding features of the adjunct. For example, first and second retaining features formed on the jaw can mate with mating features (e.g., openings) of the adjunct. Thus, the at least partially stretchable adjunct material (or portion(s) thereof) can be stretched and then allowed to contract, which causes the adjunct&#39;s mating features to engage the jaw&#39;s retaining features. In some embodiments, the adjunct can have one or more portions that are substantially non-stretchable. 
       FIG. 50  illustrates an exploded view of an example of a jaw  6602  of an end effector  6600  of a surgical instrument that has an adjunct material releasably secured thereto using an approach that does not depend on application of heat. The end effector  6600  can generally include components similar to those described with regard to  FIGS. 1-4 , and can also include features and/or components that enable adjuncts to be releasably attached thereto. Thus, similar to surgical staplers  10  ( FIG. 1 ) and  50  ( FIG. 4 ), the end effector  6600  includes an upper jaw having an anvil and an lower jaw having a cartridge body (not shown), with only the upper jaw  6602  being shown in  FIG. 50 . The lower jaw can generally include a staple cartridge that has a plurality of staple-holding cavities configured to seat staples therein, the staple-holding cavities opening on a tissue-facing surface of the cartridge. 
     As shown in  FIG. 11 , the upper jaw  6602  having an anvil  6604  has an adjunct material  6624  releasably retained on a tissue-facing surface  6618  thereof, as discussed in more detail below. The anvil  6604  has staple-forming cavities  6616  formed on the tissue-facing surface  6618 . As also shown, the tissue-facing surface  6618  has a knife channel  6608  configured to receive a cutting element (e.g., a knife). 
     As shown in  FIG. 50 , the tissue-facing surface  6618  of the anvil  6604  has at least first and second retaining members, e.g., retaining members  6622   a ,  6622   b , and can additionally include one or more retaining members, as illustrated by retaining member  6622   c . The retaining members are configured to couple the adjunct material  6624  to the anvil  6604 . In the example illustrated, the retaining members can engage with openings formed in the adjunct material  6624 , such as openings  6626   a - 6626   d , as discussed below. 
     As shown in  FIG. 50 , the retaining members  6622   a ,  6622   c  are disposed one side of the tissue-facing surface  6618  in proximity to one edge  6609   a  of the tissue-facing surface  6618 , and retaining member  6622   b  is disposed at another, opposed side of the tissue-facing surface  6618  in proximity to another, opposed edge  6609   b  thereof. It should be appreciated that the tissue-facing surface  6618  can have a fourth retaining member opposed to the retaining member  6622   c , which is not shown because of the partial view of the jaw  6604  in  FIG. 50 . The retaining members  6622   a ,  6622   b  are disposed at opposed sides of the knife channel  6608 . 
     The retaining members can have a variety of different configurations. In the example illustrated, they are in the form of curved posts, or hooks, that extend from the tissue-facing surface  6618  outward toward respective the edges  6609   a ,  6609   b . For example, the retaining member  6622   a  is curved towards the edge  6609   a , and the retaining member  6622   b  is curved towards the edge  6609   b . However, the retaining members can have other shapes, as the described implementations are not limited in this respect. For example, the retaining members can be at least partially straight, have an hour glass shape, have a bulbous or widened end region, have one or more notches, be angled toward the edges of the tissue-facing surface, have roughness features, etc. The retaining members can be configured in any suitable manner suitable for assisting in retaining the adjunct on the jaw. Also, although three retaining members  6622   a ,  6622   b  and  6622   c  are shown in  FIG. 50 , the tissue-facing surface  6618  can have any other number of retaining members (e.g., one, two, or greater than three) configured to couple an adjunct thereto. Furthermore, the retaining members can be formed at various locations on the tissue-facing surface  6618  of the anvil  6604 . For example, in some embodiments, two or more retaining members can be formed along each edge  6609   a ,  6609   b  of the tissue-facing surface  6618 . The retaining members can be formed at any suitable distance from one another that allows securely retaining the adjunct material on the jaw&#39;s tissue-facing surface. In addition, the retaining members can be disposed symmetrically with respect to the knife channel  6608  or other features of the tissue-facing surface  6618 , or they can be formed at various other ways on the surface  6618 . 
     The retaining members  6622   a ,  6622   b ,  6622   c  (and any retaining members which are not shown in  FIG. 50 ) are configured to mate with respective mating features of the adjunct material  6624 . In particular, as mentioned above, the adjunct material  6624  includes through openings  6626   a ,  6626   b ,  6626   c  configured to receive the retaining members  6622   a ,  6622   b ,  6622   c , respectively. The fourth opening  6626   d  is configured to engage a fourth retaining member, which is not shown in  FIG. 50 . The through openings  6626   a - 6626   d  in the adjunct  6624  are sized to receive therein the respective retaining members. In this example, the openings are generally round, though it should be appreciated that the openings can have any other suitable shapes. 
     In the embodiment shown in  FIG. 50 , the adjunct material  6624  is at least partially stretchable. For example, the adjunct  6624  is formed such that substantially its entire area is at least partially stretchable. The adjunct  6624  can be formed from any suitable material, for example, one or more suitable absorbable polymers. In embodiments in which the adjunct material is made from non-brittle polymers, deformations of the adjunct can be achieved through geometric changes (e.g., by reducing the adjunct&#39;s thickness until it becomes stretchy under a load, etc.). Additionally or alternatively, the adjunct material can be made at least partially stretchable by having one or more various features—for example, the adjunct can be in the form of a knitted sheet that has elasticity due to its geometry. The adjunct can be implemented as described, for example, in U.S. patent application Ser. No. 14/926,194, entitled “Extensible Buttress Assembly for Surgical Stapler,” and filed on Oct. 29, 2015, which is hereby incorporated by reference herein in its entirety. 
     In some embodiments, as in the example illustrated, the adjunct material  6624  includes at least one second, substantially non-stretchable portion. The one or more substantially non-stretchable portions can have a variety of configurations (including different configurations among the portions) and they can be disposed in any suitable manner in relation to substantially stretchable portions of the adjunct.  FIG. 50  illustrates that the adjunct material  6624  includes first and second non-stretchable portions  6628   a ,  6628   b  which can be associated with areas of the adjunct material  6624  that are disposed over the staple-forming cavities  6616  when the adjunct  6624  is placed over the jaw  6602 . Thus, one or more areas of the adjunct  6624  configured to be penetrated by the staples can be reinforced by being made substantially non-stretchable. In the illustrated implementation, the portions  6628   a ,  6628   b  are coupled to the adjunct material  6624  such that the portions  6628   a ,  6628   b  are configured to be disposed between the tissue-facing surface  6618  and the adjunct  6624 , and thus seat over the tissue-facing surface  6618 . 
     In some embodiments, it can be beneficial to attach the non-stretchable portions  6628   a ,  6628   b  to the adjunct  6624  such that portions of the adjunct  6624  disposed over the staple-forming cavities  6616  are prevented from being stretched. In particular, if portions of the adjunct  6624  that are disposed over staple-cavities  6616  are stretched, then, when the adjunct  6624  is stapled to tissue and released from the jaw  6602 , the adjunct  6624  can damage tissue by pulling on the staples as it releases tension in areas where staples are formed. In this way, the non-stretchable portions can stabilize the staples and help protecting tissue being stapled. 
     The non-stretchable portions  6628   a ,  6628   b  can be formed in any suitable manner. For example, the portions  6628   a ,  6628   b  can be separate portions coupled to the adjunct  6624 . In at least one embodiment, the portions  6628   a ,  6628   b  are formed from PDO and coupled to (e.g., laminated onto), the stretchable adjunct  6624 . As an example, the portions  6628   a ,  6628   b  can be in the form of sheet laminates that are heat-pressed or otherwise attached onto the adjunct  6624  to create the portions that are resistant to stretching. However, the portions  6628   a ,  6628   b  can be coupled to the adjunct  6624  in various other ways, as the described techniques are not limited in any specific way in which one or more portions of at least partially stretchable adjunct are made substantially non-stretchable.  FIG. 51  shows by way of example the adjunct  6624  having a first, at least partially stretchable portion  6623 . As also schematically shown in  FIG. 51 , first and second areas  6629   a ,  6629   b  of the portion  6623  of the adjunct  6624  (which is, in this example, the entire adjunct) are configured to have portions  6628   a ,  6628   b  in the form of sheet laminates coupled thereto. 
     It should be appreciated that the two separate non-stretchable portions  6628   a ,  6628   b  are shown in  FIG. 50  by way of example only. In some embodiments, one or more than two substantially non-stretchable portions can be associated with the adjunct material, and such portions can be disposed in various ways with respect to the stretchable portion(s) of the adjunct. 
     Furthermore, in at least one embodiment, the second portion can be in the form of a substantially non-stretchable second adjunct material that is coupled to the adjunct material and has any suitable size (e.g., it can have a smaller area than the “first” stretchable adjunct material). The second adjunct material is configured to reinforce and/or treat a treatment site in a patient, whereas the first stretchable adjunct material is configured to engage the first and second adjunct materials with the retaining members formed on the jaw. In some embodiments, the second adjunct can include drugs or other treating agents intended to be delivered to the treatment site. The non-stretchable portion(s) in the form of the second adjunct material can be coupled to the first adjunct material such that the second adjunct material is disposed on the tissue-facing surface of the jaw, similar to the non-stretchable portions  6628   a ,  6628   b  in  FIG. 50 . However, in some implementations, the second adjunct material can be disposed over the first adjunct material such that the stretchable adjunct material is disposed directly on the jaw. 
     It should further be appreciated that at least one substantially non-stretchable portion of the adjunct can be formed in other various ways. For example, the non-stretchable portion(s) can be part of the adjunct material. In particular, it can be in the form of at least one second portion having at least one property that is different from at least one property of other portions of the adjunct material. As an example, one or more portions of the adjunct (e.g., portions to be disposed over staple-forming or staple-holding cavities) can be more tightly woven, knitted, braded, or otherwise made non-stretchable or less stretchable than the remainder of the adjunct. 
     In use, the adjunct material  6624  is configured to be releasably coupled with the anvil  6604  by reversibly stretching at least a first portion of the adjunct (e.g., the at least partially stretchable portion) using an application of force such that, when the force is removed, the first portion transitions from a stretched configuration to a contracted configuration, thereby causing the adjunct material to be engaged with the retaining members. The adjunct material  6624  couples with the anvil  6604  in a secure manner, which helps ensure that the adjunct  6624  remains coupled to the anvil  6604  while the end effector  6100  is manipulated as desired using a surgical procedure. The adjunct  6624  is held in engagement with the anvil  6604  until an action, such as an activation of the end effector  6600  to release staples from its cartridge and/or an activation of a cutting element, is taken that causes the separation of the adjunct  6624  from the anvil  6604 . 
       FIGS. 52A and 52B  illustrate an example of a method of coupling the adjunct material  6624  with the jaw  6602 .  FIG. 52A  shows the jaw  6602  and the adjunct  6624  prior to the adjunct  6624  being coupled to the jaw  6602 . As shown schematically in  FIG. 52A , the adjunct  6624  is being stretched such that the openings  6626   a ,  6626   b  in the adjunct  6624  extend beyond the retaining members  6622   a ,  6622   b  formed on the jaw  6602 . 
     The adjunct material  6624  has at least one portion configured to be reversibly stretched using application of a force.  FIG. 52A  shows a cross-section view of the upper jaw  6602  wherein the adjunct  6624  is stretched prior to being coupled to the upper jaw  6602 , adjacent the tissue-facing surface  6618 . As illustrated by the double-ended arrow, the adjunct  6624  is stretched laterally across the tissue-facing surface  6608  of the upper jaw  6602 . In this example, non-stretchable portions  6628   a ,  6628   b  are attached to the adjunct  6624  between the adjunct  6624  and the tissue-facing surface  6618  of the upper jaw  6602  such that the areas of the adjunct  6624  having the portions  6628   a ,  6628   b  coupled thereto substantially do not stretch. In  FIG. 52A , the portions of the adjunct  6624  that do not have the portions  6628   a ,  6628   b  coupled thereto, e.g., portion  6625  and other remaining adjunct&#39;s portions, are shown stretched such that the openings  6626   a ,  6626   b  extend beyond the retaining members  6622   a ,  6622   b.    
     The at least one portion of the adjunct material  6624 , such as the portion  6625 , can be stretched using application of a force, as discussed in more detail below. When the force is removed, the stretched portion transitions from a stretched configuration to a contracted configuration, which causes the adjunct material  6624  to be engaged with the first and second retaining members  6622   a ,  6622   b . Thus,  FIG. 52B  shows the upper jaw  6602  with the adjunct coupled to the tissue-facing surface  6618  thereof via the retaining members  6622   a ,  6622   b . In particular, the retaining members  6622   a ,  6622   b  are received in openings  6626   a ,  6626   b  such that the adjunct is retained on the jaw. The adjunct material  6624  is thus held in tension by the retaining members  6626   a ,  6626   b  engaged with the openings  6626   a ,  6626   b  such that a possibility of the adjunct material  6624  prematurely slipping off the jaw is decreased or eliminated. During a surgical procedure, after the jaw  6602  with the adjunct material  6624  coupled thereto is manipulated and positioned as desired, the firing of staples and/or a cutting element releases the tension such that the adjunct material  6624  slips off the retaining members  6626   a ,  6626   b  and becomes separated from the jaw  6602 . 
     At least partially stretchable adjunct can be attached to one or both jaws of an end effector in a number of various ways. For example, in some embodiments, one or more adjuncts can be attached to jaws of an end effector using a removable loader member configured to releasably retain an adjunct material thereon until the adjunct material is applied to at least one jaw.  FIGS. 53A-53C  illustrate an example of an end effector  6700  that can be used with a member or loader  6700 , to attach one or more adjunct materials or adjuncts to the end effector  6800 . 
     The end effector  6700  can generally include components similar to those described with regard to end effector  6600 , and can also include features and/or components that facilitate attaching one or more adjuncts thereto using a loader, e.g., loader  6800 , to attach adjuncts. Thus, the end effector  6700  includes a first (upper in  FIGS. 53A-53C ) jaw  6702  having an anvil  6704  and a second (lower in  FIGS. 53A-53C ) jaw  6752  having a cartridge body. In this example, the loader  6800  is configured to apply first and second adjuncts  6724 ,  6774  to the first and second jaws  6702 ,  6752 , respectively. 
       FIG. 53A  shows a cross-sectional view of the end effector  6700 , wherein the jaws  6702 ,  6752  of the end effector  6700  are disposed over the loader  6800  prior to the adjuncts  6724 ,  6774  being coupled to the jaws  6702 ,  6752 . As shown in  FIG. 53A , in this example, the anvil  6704  includes a multi-level (e.g., a two-plane or two-level) tissue-facing surface formed of surfaces  6718 ,  6719 , wherein the surface  6718  extends in a plane closer to the cartridge  6752  and the surfaces  6719  are stepped out surfaces disposed in a plane that is further away from the cartridge  6752 . At least portions of the tissue-facing surfaces  6718 ,  6719 , have staple-forming cavities  6716  formed thereon. However, in some embodiments, the stepped surfaces  6719  may not have staple-forming cavities. The tissue-facing surface  6718  has a knife channel  6708  configured to receive a cutting element (e.g., a knife). It should be appreciated that the anvil  6704  is shown to have the two-level tissue-facing surface by way of example only, as the anvil  6704  can have a tissue-facing surface formed in substantially one planes, or, in some implementations, in more than two planes. 
     As shown in  FIG. 53A , the tissue-facing surfaces  6719  of the anvil  6704  have at least first and second retaining members  6722   a ,  6722   b  formed thereon. The tissue-facing surfaces  6719  can additionally include other retaining members, similar to those discussed above with regard to end effector  6600 . For example, each of distal and proximal ends of the tissue-facing surfaces  6719  can have two retaining members. However, other number and positions of the retaining members can be implemented additionally or alternatively. The retaining members are configured to couple the adjunct material  6724  to the anvil  6704 . In the example illustrated, the retaining members can engage with openings formed in the adjunct material, as discussed below. 
     The cartridge  6752  has a plurality of staple-holding cavities  6766  configured to seat staples therein, the staple-holding cavities  6766  opening on tissue-facing surface  6768  of the cartridge  6752 . The staple cavities can form a certain pattern on the tissue-facing surfaces  6768 , which corresponds to a pattern of the staple-forming cavities  6716  formed in the anvil  6704 . The cartridge includes first and second retaining members  6772   a ,  6772   b , located on angled surfaces  6769  that are adjacent to the tissue-facing surface  6768 . The retaining members  6772   a ,  6772   b  disposed on the angled surfaces  6769  are configured to releasably couple the adjunct material  6774  to the cartridge jaw  6752 . As also shown, the tissue-facing surface  6768  has a knife channel  6758  configured to receive a cutting element (e.g., a knife). It should be appreciated that the cartridge  6752  is shown to have the angled surfaces  6769  by way of example only, as the cartridge  6752  may not have such surfaces in other implementations, or it may have other suitable configurations. 
     The loader  6800  can have any suitable configuration. In the example illustrated, the loader  6800  can be in the form of a generally rectangular frame-like holder configured to releasably couple one or more adjuncts to one or both jaws of the end effector. As shown in  FIGS. 53A-53C , the loader  6800  can be in the form of a first (e.g., top) and second (e.g., bottom) generally rectangular housings  6802  and  6804  coupled to one another along interface A. Jaw-facing surfaces  6806 ,  6808 , of the loader  6800  can have compressible (e.g., elastic, or pliable), members or bodies  6810 ,  6812 , attached thereon. The compressible bodies  6810 ,  6812  can be made of, e.g., silicone, or any other compressible and at least partially resilient material suitable for being compressed. The elastic members  6810 ,  6812  can include gripping members  6814   a ,  6814   b ,  6816   a ,  6816   b , that extend from jaw-facing surfaces  6818 ,  6820 , respectively. 
     As illustrated in  FIG. 53A , the adjuncts  6724 ,  6774 , can be coupled to the elastic members  6810 ,  6812  of the loader  6800 , which can be done during assembly of the loader  6800 , or at any other time. The adjuncts  6724 ,  6774  can be substantially similar to adjunct  6624  ( FIGS. 52A and 52B ), and they can include openings, which can be mated with gripping members  6814   a ,  6814   b , and  6816   a ,  6816   b , to releasably secure the adjuncts to the elastic members  6810 ,  6812 . Similar to the adjunct  6624 , adjuncts  6724 ,  6774  each include first and second non-stretchable portions  6728   a ,  6728   b ,  6778   a ,  6778   b.    
     To apply the adjuncts  6724 ,  6774  to the jaws  6702 ,  6752 , the jaws  6702 ,  6752  can be clamped over the loader  6800  having the elastic members  6810 ,  6812  coupled to the adjuncts  6724 ,  6774 , as illustrated in  FIG. 53B . The clamping action causes the jaws  6702 ,  6752  to apply a force to the elastic members  6810 ,  6812  which, as a result, compress and stretch laterally, thereby causing the adjunct to also stretch, as shown in  FIG. 53B . As also shown, the elastic members  6810 ,  6812  are configured to move from their original, non-compressed configuration to a compressed configuration such that they stretch in a substantially uniform manner, such that one or more portions of the adjuncts  6724 ,  6774  can also be stretched in a substantially evenly manner. In the illustrated example, the tissue-facing surfaces  6718 ,  6768  are configured to engage the adjunct prior to the retaining members  6722   a ,  6722   b ,  6772   a ,  6772   b , which can allow the adjunct to expand without getting caught on the retaining members  6722   a ,  6722   b ,  6772   a ,  6772   b.    
     When the jaws  6702 ,  6752  are opened and the clamping force applied by the jaws  6702 ,  6752  is removed, as shown in  FIG. 53C , the adjuncts  6724 ,  6774  are released from the engagement with the elastic members  6810 ,  6812 , which at least partially return to their original, non-compressed configuration, as also shown. This causes the adjuncts  6724 ,  6774  to at least partially contract. When sufficient contraction has occurred, the adjuncts  6724 ,  6774  are separated from the loader  6800 . For example, the openings in the adjuncts  6724 ,  6774  can mate with the retaining members  6722   a ,  6722   b ,  6772   a ,  6772   b  that thus displace the gripping members  6814   a ,  6814   b ,  6816   a ,  6816   b  previously engaged with the openings. Additionally or alternatively, in some embodiments, the retaining members  6722   a ,  6722   b ,  6772   a ,  6772   b  formed on the jaws  6702 ,  6752  can engage portions of the adjuncts  6724 ,  6774  other than the openings. For example, one or more portions of the adjuncts can be stretched (as shown in  FIG. 53B ), then at least partially contracted and engaged with the retaining members  6722   a ,  6722   b ,  6772   a ,  6772   b.    
     Regardless of the specific way in which the retaining members  6722   a ,  6722   b ,  6772   a ,  6772   b  can mate with the adjuncts  6724 ,  6774 , the adjuncts  6724 ,  6754  are released from the gripping members  6814   a ,  6814   b  and become coupled to the jaws  6702 ,  6752 , as illustrated in  FIG. 53C . The adjuncts  6724 ,  6754  can be held over the jaws  6702 ,  6752  in at least partially stretched configuration. In this example, the substantially non-stretchable portions  6728   a ,  6728   b ,  6778   a ,  6778   b  of the adjuncts  6724 ,  6754  can be disposed over the jaws so as to be penetrated by the staples when the staples are ejected. The loader  6800  can then be removed. In use, after the end effector  6700  is manipulated as desired during a surgical procedure, the firing of the staples and/or a cutting element causes the adjuncts  6724 ,  6754  to separate from the jaws. 
     It should be appreciated that, although in  FIGS. 53A-53C  the loader  6800  is configured to deliver the adjuncts  6724 ,  6774  to both of the jaws  6702 ,  6752 , in some embodiments the loader  6800  can be used to apply one of the adjuncts to one of the jaws. It should also be appreciated that the loader  6800  is shown by way of example only, as at least partially stretchable adjunct can be applied to one or both jaws of an end effector using a loader having any other suitable configuration. 
     In the embodiments described above, an adjunct material can be releasably coupled to a jaw of an end effector during manufacturing of the end effector or during a surgical procedure. Furthermore, the embodiments can have different variations. For example, a jaw of an end effector having a cartridge can seat a removable and replaceable cartridge, or the entire jaw with a cartridge can be removable and replaceable. A jaw can also be part of a disposable loading unit configured to be coupled distally to a shaft of a surgical instrument. As another example, although the systems and methods for releasably retaining an adjunct material over a jaw of an end effector are described in connection with linear staplers of various configurations, it should be appreciated that the described techniques can be implemented in connection with circular surgical staplers, e.g., circular surgical stapler  80  as illustrated in  FIG. 5 . 
     Suction Attachment of an Adjunct to a Surgical Instrument 
     In general, when using an adjunct in conjunction with a surgical stapler, the adjunct can be removably attached to the end effector. The adjunct will preferably remain secured to the end effector while the end effector is positioned at a treatment site, and is removed from the end effector when staples are deployed at the treatment site to provide the benefits discussed above. However, it has been observed that adjuncts can prematurely detach from the end effector prior to staple deployment. Detachment of the adjunct from the end effector can occur in various forms, depending on the manner in which the end effector is used. For example, detachment can include vertical lift off of the adjunct from the end effector, lateral sliding of the adjunct with respect to the end effector, and/or curling of the edges of the adjunct from the surface of the end effector. The adjunct can also slide sideways when an end effector is used to clamp and twist tissue. 
       FIGS. 54-58  illustrate various exemplary devices and methods for attaching an adjunct to a surgical instrument. In general, an adjunct can include a plurality of suction members configured to attach the adjunct to an end effector jaw of surgical instrument by a suction force/partial vacuum, which in certain aspects can be generated when the adjunct is compressed against the end effector jaw. The suction members can be further configured to release the suction/partial vacuum, decoupling the adjunct from the end effector jaw at a treatment site. Embodiments of the adjuncts are discussed below in conjunction with the stapler  10 , where the suction members couple the adjunct to a tissue contacting surface  33  of the upper jaw  34  of an end effector  30 . However, a person skilled in the art will appreciate that embodiments of the suction members can be employed with any surgical instrument without limit. Furthermore, embodiments of the suction members can be employed to couple adjuncts with the tissue contacting surface  33  of the upper jaw  34 , a tissue contacting surface of the lower jaw  32 , and combinations thereof. 
       FIGS. 54-55C  illustrate an embodiment of an adjunct  7500  that includes a plurality of suction members  7502  disposed upon the tissue contacting surface  33  (e.g., an anvil surface) of the upper jaw  34  of stapling device  10 . As described in detail below, each of the suction members  7502  can be formed within the adjunct  7500  and can be configured to couple the adjunct  7500  to the upper jaw  34 . For example, the suction members  7502  can provide a suction force/partial vacuum between the adjunct  7500  and the tissue contacting surface  33  that is sufficient to inhibit lateral sliding and vertical removal of the adjunct  7500  with respect to the tissue contacting surface  33  prior to placement at a treatment site. 
     In the embodiment shown in  FIGS. 54-55C , the adjunct  7500  can be formed as a flexible laminate, including a first adjunct layer  7500   a  and a second adjunct layer  7500   b . The first and second adjunct layers  7500   a ,  7500   b  can be coupled together along a common interface. In an exemplary embodiment, the first adjunct layer  7500   a  includes the plurality of suction members  7502  and the second adjunct layer  7500   b  is substantially solid, non-permeable, and void-free. The plurality of suction members  7502  include a plurality of air pockets or voids  7504  formed beneath the surface of the first adjunct layer  7500   a  and respective openings  7506  formed in an outer surface of the first adjunct layer  7500   a . While the first and second adjunct layers  7500   a ,  7500   b  are illustrated as single layers, a person skilled in the art will appreciate that either or both of the first and second adjunct layers can be formed from two or more discrete layers fused together. 
     The plurality of suction members  7502  can be formed in a variety of ways. In one embodiment, the voids  7504  can be formed by cutting pockets having a selected shape through an inner surface and into a bulk of the first adjunct layer  7500   a , separated from the outer surface by a selected distance. In another embodiment, the first adjunct layer can be cast from a melt using a mold that defines the pockets and, optionally, the openings  7506  therein. In either scenario, respective openings  7506  can be further formed through each of the pockets to the outer surface of the first adjunct  7500   a . A diameter of each opening  7506  can be less than its corresponding pocket. Once the pockets and openings  7506  are formed, the first adjunct layer  7500   a  can be placed on the second adjunct layer  7500   b  and coupled thereto to close the pockets on all sides except for the openings  7506 , forming the voids  7504 . For example, the first and second adjunct layers  7500   a ,  7500   b  can be fused together along a common interface including the inner surface of the first adjunct layer  7500   a  by one or more of application of heat, adhesives, activation of the first and/or second adjunct layers  7500   a ,  7500   b  by a solvent, and any other mechanism for lamination of the first and second adjunct layers  7500   a ,  7500   b . A person skilled in the art will appreciate that, while  FIGS. 54 and 55A-55C  illustrate the plurality of voids  7504  as having rectilinear shapes, they can adopt any desired shape. 
     A suction force/partial vacuum can be generated between the suction members  7502  and the tissue contacting surface  33  as follows. As illustrated in  FIG. 55A , the adjunct  7500  can be oriented with the outer surface of the first adjunct layer  7500   a  opposite the tissue contacting surface  33  of the upper jaw  34 . Subsequently, the adjunct  7500  can be positioned on the upper jaw  34 , with the first adjunct layer  7500   a  contacting the tissue contacting surface  33 , and the second adjunct layer  7500   b  can be compressed against the tissue contacting surface  33 , as illustrated in  FIG. 55B . This compression can establish a partial vacuum within the plurality of voids  7504  by elastically deforming the plurality of voids  7504  and expelling air from the plurality of voids  7504  to the environment via the plurality of openings  7506 . Since the pressure of the surrounding atmosphere is greater than the pressure within the plurality of voids  7504 , the atmosphere presses the plurality of voids  7504  against the tissue contacting surface  33 , establishing the suction force/partial vacuum that secures the adjunct  7500  to the upper jaw  34 . A person skilled in the art will appreciate that, while the adjunct  7500  is illustrated as a laminate in  FIGS. 54-55C , alternative embodiments of the adjunct can be formed as a single layer that includes the plurality of suction members  7502 . 
     The adjunct  7500  can be formed from one or more materials configured to allow flexure of the adjunct  7500  and deformation (e.g., elastic deformation) of the adjunct  7500  under compression. For example, the first and second adjunct layers  7500   a ,  7500   b  can each be independently selected from materials possessing a stiffness that provides a desired degree of elastic deformation under flexure and/or compression. Examples of suitable materials can include, but are not limited to, synthetic materials and biologic materials. Synthetic materials can include biodegradable polymers such as polydioxanone (PDS), Monocryl® (poliglecaprone 25, a copolymer of glycolide and ε-caprolactone; Ethicon, Inc.), polyhydroxy acids (e.g., poly-lactides, polyglycolides, polyhydroxybutyrates, polyhydroxy-valeriates), copolymers of lactide and trimethylene carbonate, copolymers of glycolide, lactide and trimethylene carbonate, polycaprolactones, polydioxanones, synthetic or natural oligo- and polyamino acids, polyphosphazenes, polyanhydrides, polyorthoesters, polyphosphates, polyphosphonates, polyalcohols, polysaccharides, and polyethers. Biologic materials can include, but are not limited to, naturally-occurring materials (e.g., collagens, gelatin), naturally-derived materials (e.g., bioabsorbable gel films cross-linked with omega-3 fatty acids), and oxygenized regenerated cellulose (ORC). In certain embodiments, a thickness of each of the first and second adjunct layers  7500   a ,  7500   b  can be independently selected from the range of about 8 μm to about 25 μm. The arrangement of the suction members  7502  within the adjunct  7500  can be configured to facilitate deformation of the adjunct  7500  under compression. For example, as further illustrated in  FIG. 55B , at least a portion of the suction members  7502  can be formed in a pattern that substantially matches a pattern of staple-receiving cavities  7043  formed in the tissue contacting surface and aligned with the staple-receiving cavities  7043  when positioned on the upper jaw  34 . The suction members  7502  aligned in this manner can be more easily compressed against the upper jaw  34 , as compared to suction members  7502  that are not aligned because they are not supported by the upper jaw  34  (e.g., the tissue contacting surface  33  is recessed from the first adjunct layer  7500   a  by the staple-receiving cavities  7043 ). One skilled in the art will appreciate alternative embodiments of the suction members  7502  can alternatively or additionally be patterned for alignment with the pockets  41  of the tissue contacting surface of the lower jaw  32 . 
     The adjunct  7500  can also be applied to the tissue contacting surface  33  using an applicator (not shown) that facilitates compression of the adjunct  7500 . The applicator can include raised areas having a similar shape and/or distribution pattern as the staple-receiving cavities  7043 . When a raised area of the applicator is aligned with a given suction member  7502  and staple-receiving cavity  7043 , the raised area can extend within the staple-receiving cavity  7043  and compress the suction member  7502  by a greater degree than a planar applicator. One skilled in the art will appreciate alternative embodiments of the applicator can be patterned for alignment with the pockets  41  of the tissue contacting surface of the lower jaw  32 . 
     The suction members  7502  can also be configured in a variety of ways to adjust the suction force/partial vacuum. In one example, the suction force/partial vacuum of a given suction member  7502  can be raised or lowered by increasing or decreasing the volume of the plurality of voids  7504 , assuming a constant pressure difference between the atmosphere and the plurality of voids  7504 . In another example, the total suction force exerted on the adjunct  7500  by the plurality of suction members  7502  can be raised or lowered by increasing or decreasing the number of suction members  7502  within the adjunct  7500 , assuming each suction member  7502  is the same volume. Furthermore, by varying the location of suction members  7502  within the adjunct  7500 , the suction force/partial vacuum can be locally increased or decreased at selected areas of the adjunct  7500 . 
     The suction members  7502  can be further configured to release the adjunct  7500  from the tissue contacting surface  33  after penetration of staples through the adjunct  7500 , allowing the adjunct  7500  to be retained at a tissue treatment site when the end effector  30  is retracted from the tissue. In one embodiment, the suction force/partial vacuum exerted by the plurality of suction members  7502  can be tailored, as discussed above, so that the force with which the adjunct  7500  is attached to the tissue by the staples is greater than the suction force. Thus, after the staples are deployed through the adjunct  7500  and the tissue, the adjunct  7500  can be released from the tissue contacting surface  33 . In another embodiment, illustrated in  FIGS. 55B-55C , at least a portion of the suction members  7502  can be aligned with respective staple-receiving cavities  7043 . In an exemplary embodiment ( FIG. 55C ), staples  7510  fired through the adjunct  7500  and into the staple-receiving cavities  7043  can pierce the plurality of voids  7504  to break the suction/partial vacuum. 
     Embodiments of the adjunct  7500  can optionally include one or more features configured to work in combination with suction members  7502  to inhibit sliding of the adjunct  7500  when positioned on the tissue contacting surface  33 . For example, the adjunct  7500  can include one or more protruding features (not shown) that extend outward from the surface of the first adjunct layer  7500   a . These features can be dimensioned for receipt within one or more recessed areas formed within the tissue contacting surface  33 . As shown in  FIG. 54 , one embodiment of the recessed areas can include a slot  7044  formed in the upper jaw  34  that is configured to receive the knife blade  36  or other cutting element during advancement between the jaws  32 ,  34 . When the adjunct  7500  is positioned on the tissue contacting surface  33  one or more protruding features can extend within the slot  7044  and maintain the lateral position of the adjunct  7500  when experiencing shear stresses. The suction members  7502  can be distanced from the location of the protruding features to avoid interference with compression of the suction members  7502 . 
     Another embodiment of an adjunct  7700  is illustrated in  FIGS. 56A-57C . The adjunct can generally be configured and used similar to the adjunct  7500 , attaching to the tissue contacting surface  33  via suction force/partial vacuum and releasing from the tissue contacting surface  33  when staples are deployed. As shown in  FIGS. 56A-56B , the adjunct  7700  includes coupled first and second adjunct layers  7700   a ,  7700   b  and a plurality of suction members  7702 . In this implementation, the suction members  7702  can be formed as hollow protrusions extending outward from a surface of the first adjunct layer  7700   a , opposite the second adjunct layer  7700   b . The protrusions can define a plurality of air pockets  7704  in fluid communication with respective openings  7706  extending through each protrusion. While the first and second adjunct layers  7700   a ,  7700   b  are illustrated as single layers, a person skilled in the art will appreciate that either or both of the first and second adjunct layers can be formed from two or more discrete layers fused together. 
     As shown in  FIGS. 57A-57C , the adjunct  7700  can be positioned on the tissue contacting surface ( FIG. 57A ) and suction members  7702  can be compressed to expel air from the air pockets  7704  to the environment via the openings  7706 , forming a suction force/partial vacuum therein ( FIG. 57B ). The air pockets  7704  can further release the suction resulting from the partial vacuum when the staples are fired through the adjunct  7700 . In an exemplary embodiment, the suction force/partial vacuum can be released by piercing the air pockets  7704  with staples  7710 , as shown in  FIG. 57C . Alternatively or additionally, the force of the suction/partial vacuum provided by the plurality of suction members  7702  can be overcome by the strength of attachment of the staples  7710  to tissue (not shown) when the end effector  30  is removed from the tissue. A person skilled in the art will appreciate that, while  FIGS. 56A-57C  illustrate the plurality of suction members  7702  as having generally circular shapes, the suction members  7702  can adopt any desired shape. For example,  FIG. 58  illustrates an embodiment of an adjunct  7900  that includes a plurality of suction members  7902  with air pockets  7904  formed therein and having openings  7906 . As shown, the suction members  7902  have a shape that conforms to the shape of the staple-receiving cavities  7043 . 
     The plurality of suction members  7702 ,  7902  can be formed in a variety of ways. In one embodiment, protrusions can be formed by casting the first adjunct layer  7700   a  from a melt using a mold that defines voids having a selected shape therein. Subsequently, respective openings  7706 ,  7906  can be formed through each of the voids to the outer surface of the first adjunct  7700   a . A diameter of each opening  7706 ,  7906  can be less than a width of its corresponding void. After the voids and openings  7706 ,  7906  are formed, the first adjunct layer  7700   a  can be placed on the second adjunct layer  7700   b  and coupled thereto to close the voids on all sides except for the openings  7706 ,  7906 , forming the air pockets  7704 ,  7904 . For example, the first and second adjunct layers  7700   a ,  7700   b  can be fused together along a common interface including the inner surface of the first adjunct layer  7700   a  by one or more of application of heat, adhesives, activation of the first and/or second adjunct layers  7500   a ,  7500   b  by a solvent, and any other mechanism for lamination of the first and second adjunct layers  7700   a ,  7700   b.    
     The plurality of suction members  7702 ,  7902  can also be configured to inhibit lateral sliding of the adjuncts  7700 ,  7900  when positioned on the upper jaw  34 . In one embodiment, at least a portion of the suction members  7702 ,  7902  can possess a shape dimensioned for receipt within the plurality of staple-receiving cavities  7043 . For example, the shape of the suction members  7902  can be configured to mate with the plurality of staple-receiving cavities  7043 . In these implementations, when the suction members  7702 ,  7902  are received within the staple-receiving cavities  7043  and the adjunct  7700  is subjected to in-plane forces (e.g., shear forces), the lateral sides of the staple-receiving cavities  7043  can constrain the lateral motion of the suction members  7702 ,  7902 , thereby inhibiting lateral motion of the adjuncts  7700 ,  7900 . 
     In an embodiment, any of the adjuncts  7500 ,  7700 ,  7900  can also be configured to perform a healing function when positioned on tissue. Such healing functions can include, but are not limited to, delivering a medicant, reinforcing tissue, promoting tissue ingrowth or adhesions, deter adhesions, and the like. 
     Adjunct Material with Mating Features 
     In some implementations, an adjunct or adjunct material can be configured to be releasably retained on a jaw of an end effector for a surgical instrument using different types of features. Specifically, an adjunct material is provided that includes features for releasably attaching the adjunct material to the end effector and features for preventing stretching and/or displacement of the adjunct material as it is transferred to a treatment site in a patient. 
     The features for attaching the adjunct material to the end effector can be referred to as “retaining” features that are formed on the adjunct such that it can mate with respective features formed on the jaw (an anvil or a cartridge), to releasably retain the adjunct on the jaw. The adjunct is releasably retained on the jaw such that the adjunct remains attached to the jaw until the adjunct is applied to a treatment site. The adjunct additionally includes features that can be referred to as “non-retaining” features that are configured to mate with respective features on the jaw on which the adjunct is mounted such that the adjunct is able to move at least in a plane parallel to the tissue-facing surface. Such “non-retaining” features allow avoiding stretching, sliding off, and/or displacement of the adjunct material from its proper position at a treatment site to which the adjunct material is delivered when the staples are deployed. The adjunct is configured to be positioned on a jaw such that it is aligned with the staple pattern such that the staples, when ejected, penetrate the adjunct at desired locations. 
     When an end effector is deployed and tissue is clamped between the jaws such that the jaws apply force thereto, squeeze the tissue, and cause it to be penetrated by the deployed staples, the tissue is deformed. For example, portions of the tissue may flow out under the load and can form enlarged areas, which can cause the adjunct to be stretched and displaced from its intended position at the treatment site. This misalignment and displacement of the adjunct can negatively affect the proper reinforcement and/or treatment of the tissue at the surgical site with the adjunct material. Accordingly, the described techniques provide an adjunct material that includes features that prevent the undesirable stretching and/or displacement of the adjunct material. Such features of the adjunct can mate with complementary features formed on a jaw of an end effector on which the adjunct material is mounted. 
     In general, in the described implementations, a jaw of the end effector includes a plurality of male features formed on a tissue-facing surface of the jaw. The adjunct material can have a plurality of female features, with each female feature being able to encompass a corresponding one of the male features in a clearance fit such that the adjunct material is able to move with respect to the jaw on which it is mounted at least in a first plane parallel to the tissue-facing surface of the jaw. In this way, these “non-retaining” female and male features limit movement of the adjunct laterally and longitudinally (i.e. in the x and y directions), while not limiting movement of the adjunct in a vertical direction (i.e. in the z direction), which causes the adjunct to remain properly positioned during staple deployment at a treatment site. 
     The adjunct material also has at least one attachment feature configured to releasably retain the adjunct material on the at least one jaw. Such “retaining” features releasably retain the adjunct with respect to a tissue-facing surface of the jaw until the adjunct is caused to be transferred to the treatment site. Thus, the retaining features can be used to retain the adjunct on the jaw in a substantially non-movable manner. As the staples are deployed by being ejected from an end effector&#39;s cartridge, the staples cause the adjunct material to be separated from the jaw to become attached to the tissue with the staples. 
       FIG. 59  illustrates an example of a portion of the end effector  8100  having first and second opposed jaws configured to clamp tissue therebetween, in accordance with the described techniques. The end effector  8100  can be used with any suitable surgical instrument, for example, a linear surgical stapler (e.g., stapler  10  in  FIG. 1 , stapler  50  in  FIG. 4 , or any other surgical stapler) which can be suitable for use with at least one adjunct. The end effector  8100 , only a portion of which (an upper jaw or anvil  8102 ) is shown in  FIG. 59 , can be coupled to a distal end of a shaft of the surgical stapler (not shown). As shown in  FIG. 59 , the anvil  8102  has a plurality of staple-forming pockets or cavities  8104  formed on a tissue-facing surface  8106  of the anvil  8102 . The staple-forming cavities  8104  form a certain pattern on the surface of the anvil  8102  which corresponds to a pattern of staple-holding cavities in the cartridge of the end effector  8100  (not shown in  FIG. 59 ). The anvil  8102  includes an anvil knife channel  8108  extending between distal and proximal ends  8102   d ,  8102   p  of the anvil  8102 . The anvil knife channel  8108  is configured to receive a cutting element (e.g., a knife) as the cutting element moves distally through a cartridge knife slot in the staple cartridge. 
     The end effector  8100  includes an adjunct material  8105  mounted thereon, a portion of which is shown in  FIG. 59  for illustration purposes only. In the example illustrated, the generally rectangular adjunct material  8105  includes both retaining and non-retaining features for mating with the anvil of the end effector, as discussed below. It should be appreciated that the anvil  8102  is shown by way of example, as the adjunct material can also be mounted on a cartridge using the described techniques. Further, in some embodiments, both anvil and cartridge of an end effector have respective adjunct materials releasably mated thereto using both retaining and non-retaining features in accordance with the described techniques. 
     As shown in  FIG. 59 , the anvil  8102  includes non-retaining features in the form of male features, such as, in this example, four posts or projections  8110   a ,  8110   b ,  8110   c ,  8110   d  formed on the tissue-facing surface  8106  of the anvil  8102 . As also shown in  FIG. 59 , the adjunct material  8105  also has non-retaining features such as female features in the form of openings configured to encompass corresponding male features in a clearance fit. Because the adjunct material  8105  is shown only partially in  FIG. 59 , two openings  8112   c ,  8112   d  in the adjunct material  8105  formed at a proximal end  8105   p  are shown. It should be appreciated, however, that, though not shown, the adjunct material  8105  also includes two other openings at a distal end thereof that correspond to the projections  8110   a ,  8110   b  formed on the tissue-facing surface  8106  of the anvil  8102  at the anvil&#39;s distal end  8102   d.    
     The adjunct material  8105  also has one or more retaining features that releasably retain the adjunct material  8105  on the jaw  8102 . In the illustrated example, such features are in the form of a layer  8107  of an adhesive material disposed on the jaw-facing surface of the adjunct material  8105 , as shown in  FIG. 60 . The adhesive material layer  8107  can be formed on the entirety of the adjunct material  8105  or it can be disposed on one or more portions of the adjunct material  8105 . The adhesive material layer  8107  can be formed from any suitable material. For example, the adhesive material can be polydioxanone (PDO), a low molecular weight polyethylene glycol (PEG) or any other material (or a combination of materials) that can be used to attach the adjunct to the jaw. In some embodiments, the adhesive material can be a bioabsorbable and/or biodegradable pressure sensitive adhesive. 
     The female features of the adjunct material  8105  and the male features formed on the anvil  8102  can have many different configurations and the female and male features can mate in a variety of different ways. In this example, the female features of the adjunct material  8105  in the form of openings are configured to encompass the male features in the form of projections formed on the anvil  8102  in a clearance fit such that the adjunct material  8105  is able to move with respect to the anvil  8102  at least in a first plane  8114  parallel to the tissue-facing surface  8106  of the anvil  8102 , which is schematically shown in  FIG. 59 . It should be appreciated, however, that the movement of the adjunct material  8105  in the first plane  8114  is restricted to the extent that corresponds to a degree of the clearance fit between the female and male features. 
     As shown in  FIG. 60  illustrating a portion of the end effector  8100 , the projection  8110 ′, representing the projections  8110   a ,  8110   b ,  8110   c ,  8110   d  formed on the tissue-facing surface  8106  of the anvil  8102 , is tapered in a direction that is perpendicular to a longitudinal axis  8 A 1  of the jaw  8102 . As further shown in  FIG. 60  illustrating a portion of the end effector  8100 , an opening  8112 ′ in the adjunct material  8105  (e.g., any of the openings  8112 ,  8112   d , or other openings) is oversized with respect to a corresponding projection  8110 ′ (e.g., any of the anvil&#39;s projections  8110   a ,  8110   b ,  8110   c ,  8110   d ) formed on the anvil  8102 . As a result, the opening  8112 ′ encompasses the projection  8110 ′ in a clearance fit such that the adjunct material  8105  is able to move with respect to the anvil  8102  at least in the first plane  8114  shown in  FIG. 59 . When the opening  8112 ′ is generally round in shape, as in the illustrated example, its diameter is larger than a largest dimension of the projection  8110 ′ in the plane parallel to a plane of the tissue-contacting surface of the jaw. 
     The configuration and size of the female feature in the form of the opening  8112 ′ is such that the male feature in the form of the projection  8110 ′ encompassed by opening  8112 ′ is not effective to retain the adjunct material  8105  in a second plane  8116  that is perpendicular to the first plane  8114 . Thus, the projection  8110 ′ is encompassed by the opening  8112 ′ such that, if the jaw  8102  with the adjunct  8105  mounted thereon were to be turned upside down, and if the projection  8110 ′ and the opening  8112 ′ were the only features used to position the adjunct  8105  over the jaw (which is not the case), the adjunct  8105  would slide off the jaw  8102  with little or no force. It should be appreciated that the planes  8114 ,  8116  are referred to as “first” and “second” for purposes of description only, and not to indicate any particular order. 
     As mentioned above, the adjunct material  8105  and the female features formed thereon can have various configurations. In the example illustrated, the openings (e.g., the openings  8112   c ,  8112   d  shown in  FIG. 59 ) in the adjunct material  8105  are generally circular in shape and they have a diameter that allows them to encompass the projections (e.g., the projections  8112   c ,  8112   d ) formed on the jaw  8102  in a clearance fit. However, it should be appreciated that the adjunct material  8105  can have openings having other shapes, which can be different from circular (e.g., oval, rectangular, square, or irregular shapes). Also, the adjunct material can include openings having the same size, or openings of different sizes and/or shapes can be formed in the adjunct material. 
     The male features, such as the projections  8110   a ,  8110   b ,  8110   c ,  8110   d  formed on the tissue-facing surface  8106  of the anvil  8102 , can be formed at any suitable locations on the anvil  8102 . The projections can be formed within an area of the tissue-facing surface  8106  occupied by the staple-forming pockets  8104 , or the projections can be formed outside of this area. Thus, in the example of  FIG. 59 , the projections  8110   a ,  8110   b  formed at the distal end  8102   d  of the anvil  8102  are offset distally from the staple-forming pockets  8104 . The projections  8110   c ,  8110   d  formed at the proximal end  8102   p  of the anvil  8102  can be formed within the anvil&#39;s area having the staple-forming pockets  8104 . However, in some embodiments, the projections  8110   c ,  8110   d  can be formed on the area of the anvil  8102  outside of the area having the staple-forming pockets  8104 . 
     In some implementations, as mentioned above, the projections on the tissue-facing surface of a jaw of the anvil can be formed within the area of the anvil having the staple-forming pockets such that the projections are formed between the staple-forming pockets. The adjunct material used in conjunction with the anvil having such projections can have corresponding female features disposed at locations of the adjunct material such that the female features can encompass the male features in a clearance fit. Furthermore, a cartridge of an end effector can have male features formed within the cartridge&#39;s area having the staple pockets (e.g., between the pockets), of the male features can be formed outside of the area having the staple pockets. 
     A jaw of an end effector can have any suitable number of male features configured to mate with corresponding adjunct&#39;s female features using the described techniques—in a non-retaining manner. The four projections  8110   a ,  8110   b ,  8110   c ,  8110   d  formed on the tissue-facing surface  8106  of the anvil  8102  are shown in  FIG. 59  by way of example only. Thus, one, two, three, or more than four projections configured to mate with corresponding female features formed on the adjunct. In embodiments in which one projection is used, it can be in the form of an elongate, narrow feature, such as a rib or a slot. Alternatively, if the adjunct is configured to be constrained proximally by the end effector (e.g., between the tissue stops of the anvil), a single distal attachment point may be sufficient to apply the adjunct to the jaw. Furthermore, in some embodiments, at least one of the female features can be configured such that a single female feature encompasses more than one male feature. For example, one opening formed in the adjunct material can encompass in a clearance fit two or more male features formed on an anvil or on a cartridge. 
     The non-retaining male and female features (i.e., the features configured to mate such that an adjunct can move with respect to the jaw on which it is mounted at least in the first plane parallel to the tissue-facing surface, and such that the adjunct is not retained in the second plane that is perpendicular to the first plane) can have various configurations. Thus, the projections and openings are shown in  FIGS. 59 and 60  by way of example only. 
     It should be appreciated that retaining attachment features (i.e., features configured to retain the adjunct with respect to the jaw on which it is mounted such that the adjunct cannot move in the first and second planes and can only be separated from the jaw when the staples are ejected) can also have various configurations. As discussed above, in the example shown in  FIGS. 59 and 60 , the attachment feature is the adhesive layer  8107  formed on the jaw-facing surface of the adjunct. Other attachment feature(s) can be used additionally or alternatively, as the described techniques are not limited to any specific attachment features configured to releasably retain the adjunct on the jaw. For example, the jaw can have one or more projections or other male features that can serve as the attachment features configured to mate with respective female features formed on the adjunct material. In some implementations, the attachment male features formed on the adjunct can be configured to mate with complementary female features formed on the jaw. Furthermore, different types of features (e.g., both female and male or combination(s) thereof) can be formed on the adjunct, which can mate with corresponding features of the jaw. The described techniques are also not limited with respect to a number of the attachment features and to specific locations of the attachment features on the jaw and on the adjunct material. 
       FIG. 61  illustrates another example of a distal portion of an end effector having features in accordance with the described techniques. The end effector can be used with any suitable surgical instrument. For example, it can be used with a linear surgical stapler, such as stapler  10  in  FIG. 1 , stapler  50  in  FIG. 4 , or any other surgical stapler. In this example, a jaw in the form of the cartridge  8202  of the end effector having staple pockets  8204  formed on a tissue-contacting surface  8206  thereof is shown. The staple pockets  8204  form several rows along a longitudinal axis  8 A 2  of the cartridge  8202 . The cartridge  8202  can be a removable and replaceable cartridge. In some embodiments, the cartridge  8202  can be part of a replaceable and disposable loading unit configured to couple distally to a shaft (not shown) of the end effector. 
     As shown in  FIG. 61 , the tissue-contacting surface  8206  of the cartridge  8202  has male features in the form of multiple projections  8210  formed along a long side of the cartridge  8202 . In this example, the projections  8210  form two rows on opposite sides of the area of the tissue-contacting surface  8206  having the staple pockets  8204 , with the rows extending parallel to the longitudinal axis  8 A 2  of the cartridge  8202 . Any suitable number of projections can be formed at a suitable distance from one another. The projections  8210  can be in the form of posts having a rounded and/or tapered head. It should be appreciated, however, that the projections  8210  can have any suitable configurations. 
     As also shown in  FIG. 61 , the cartridge  8202  can retain thereon an adjunct material  8205  having female features configured to mate with the jaw&#39;s male features in the form of the projections  8210  such that each female feature can encompass a corresponding one of the male features in a clearance fit. In this way, the adjunct material  8205  is able to move with respect to the jaw  8202  at least in a first plane  8214  parallel to the tissue-facing surface  8206  of the jaw  8202 . 
     In the example of  FIG. 61 , the adjunct  8205  is formed from at least partially stretchable or expandable material formed of fibers such that at least some portions of the adjuncts are relatively loose. For example, the adjunct can be a fiber-based lattice which can be a woven fabric, knitted fabric or non-woven fabric. The adjunct can have multiple regions that can be formed from the same type of lattice or from different types of lattices that can together form the adjunct in a number of different ways. For example, the fibers can be woven, braided, knitted, or otherwise interconnected so as to form a regular or irregular structure. The fibers can be interconnected such that the resulting adjunct is relatively loose. 
     The expandable material can be, e.g., in the form of a mesh material having fibers forming regular or irregular patterns, or a combination of regular or irregular patterns. The adjunct  8205  has a plurality of female features in the form of expandable openings  8212  formed between fibers of the expandable material. The openings  8212  can be preformed in the adjunct material  8205  such that they are formed at predetermined locations. For example, the openings  8212  can be formed in two rows along opposite long sides of the adjunct material  8205 , as shown in  FIG. 61 . In some embodiments, the expandable openings can exist in the adjunct material  8205  due to the nature of the fabric from which the adjunct material is formed. As mentioned above, the entire adjunct material or one or more portions thereof can be relatively loosely interconnected, and such loosely interconnected portions can have openings therein. In such embodiments, the male features formed on the jaw can “find” openings in the adjunct to mate with when the adjunct is placed over the jaw. 
     Regardless of the specific way in which the female features are formed in the adjunct material, the adjunct material can mate with the male features formed on the jaw because the expandable material stretches (e.g., its fibers separate) and thus enlarges in places where the male features are inserted at least through the mesh.  FIGS. 62A, 62B, and 62C  illustrate an example of openings  8212 ′ in an adjunct material  8205 ′ that can encompass posts or projections  8210 ′ formed on a jaw, such as the cartridge  8202  or other jaw (which can be an anvil). 
     As shown in  FIG. 62A , openings  8212 ′ in an adjunct material  8205 ′, three of which are labeled as openings  8217   a ,  8217   b ,  8217   c , can be present in the expandable material forming the adjunct material  8205 ′ due to the way in which the fibers of the adjunct material are interwoven. The openings  8217   a ,  8217   b ,  8217   c  exist between the interwoven fibers of the adjunct material  8205 ′ and each can be expanded, enlarged, or deformed when it receives a respective projection therein.  FIG. 62B  illustrates by way of example of three projections  8219   a ,  8219   b ,  8219   c  of the multiple projections that can be formed on the jaw, such as the cartridge  8202  in  FIG. 61  or other jaw. 
     When the adjunct material  8205 ′ is laid over the jaw, the projections  8219   a ,  8219   b ,  8219   c  are received within the openings  8217   a ,  8217   b ,  8217   c  such that the material forming the adjunct material  8205 ′ stretches over the projections  8219   a ,  8219   b ,  8219   c  in direction indicated by arrows  8220   a ,  8220   b , as shown in  FIG. 62C . The property of the material is such that it is stretched and/or deformed so that the adjunct material  8205 ′ is able to move with respect to the jaw at least in a first plane parallel to the tissue-facing surface of the jaw and so that the adjunct material is not retained in a second plane that is perpendicular to the first plane. 
     In addition to female features described above, the adjunct material  8205  in  FIG. 61  and the adjunct material  8205 ′ shown in  FIGS. 62A and 62C  also have at least one attachment feature configured to releasably retain the adjunct material on the jaw. The at least one attachment feature can be an adhesive material layer formed over at least a portion of the adjunct material, or any other type of feature(s), such as a male or female feature, or a combination thereof. The at least one attachment feature can be configured to mate with the end effector&#39;s jaw on which the adjunct is mounted, in a way corresponding to a type of the attachment feature. For example, when the attachment feature is the adhesive material layer, such adhesive material layer attaches to the jaw due to its adhesive nature. When the attachment feature is one or more openings or projections, they are configured to mate with corresponding projections or openings formed on the jaw. 
     Regardless of the specific type, number, and location of attachment feature(s) formed on the adjunct material, they are formed to retain the adjunct material on the jaw in three dimensions, such that the adjunct can be separated from the jaw when the staples are ejected from the cartridge. The adjunct&#39;s non-retaining features (e.g., various female features described herein), which do not retain the adjunct with respect to the jaw in the plane perpendicular to a plane parallel to the jaw&#39;s tissue-contacting surface, are used to prevent stretching of the adjunct material and/or displacement (e.g., slipping or sliding off) of the adjunct from the jaws of the end effector. Thus, unlike the non-retaining adjunct&#39;s features that are only used to properly position the adjunct, the attachment features serve to releasably retain the adjunct on the jaw. 
     In some embodiments, an adjunct material is formed from fibers and it comprises a backing layer non-removably attached thereto on a side of the adjunct material facing the jaw. The fibers can be a mesh, nonwoven fibers, or any other type(s) of fibers. The backing layer can have female features formed thereon for mating with respective male features formed on the jaw on which the adjunct material is mounted.  FIGS. 63 and 64  illustrate example of such adjunct material, with the jaw not shown. 
       FIG. 63  illustrates an example of an adjunct material  8300  in the form of a generally rectangular fiber layer. The adjunct material  8300  has a backing layer  8302  non-removably attached thereto on a side of the adjunct material facing the jaw of an end effector. As shown in  FIG. 63 , the backing layer  8302  has a plurality of female features in the form of openings  8304  formed thereon. The openings  8304  can mate with corresponding male features of the jaw (e.g., a cartridge or anvil). In this example, the openings  8304  are configured to mate with the male features such that not every opening mates with the jaw. Thus, a pattern and/or number of male features formed on the jaw may be different from a pattern and/or number of female features formed on the adjunct material. For example, the jaw can have fewer male features (e.g., projections such as projections  8110  ( FIG. 59 ), projections  8210  (FIG.  61 ), or any other male features) than the number of openings. In this way, for example, only some of the openings  8304  (which are oversized with respect to the male features) may surround respective male features. Thus, there is no requirement that specific openings surround specific male features. The adjunct material  8300  with multiple openings formed therein can thus be easily positioned over the jaw and the male features “find” openings that can surround the male features. The number of the male features can be selected such that it is sufficient to prevent displacement of the adjunct material from the end effector&#39;s jaw(s), in accordance with the described techniques. 
     The openings  8304  can have any suitable configuration. For example, while generally circular openings  8304  are shown in  FIG. 63 , the openings can be oval, rectangular, square, or they have can other regular or irregular shapes. Any suitable number of openings can be formed in any suitable pattern(s). 
     The backing layer  8302  can be formed from any suitable biodegradable and/or bioabsorbable material, such as, for example, polydioxanone (PDO) or any other suitable polymeric material(s). The material can be selected such that it biodegrades and/or bioabsorbs faster than the adjunct material  8320 . As shown in  FIG. 63 , the backing layer  8302  has a thickness that is smaller than that of the adjunct material  8320 . For example, in some embodiments, the height or thickness  8   h   1  of the adjunct material  8320  can be from about 0.004 inches to about 0.020 inches, whereas the height or thickness  8   h   2  of the backing layer  8302  can be from about 0.0002 inches to about 0.0012 inches. However, in some embodiments, the thickness  8   h   1  of the adjunct material can be greater—e.g., from about 0.01 inches to about 0.150 inches. The thickness  8   h   1  of the adjunct material, as well as the thickness  8   h   2  of the backing layer, can vary within other suitable ranges. 
       FIG. 64  illustrates another example of an adjunct material  8400  in the form of a generally rectangular fiber layer. The adjunct material  8400  has a backing layer  8402  non-removably attached thereto on a side of the adjunct material  8400  facing a jaw of an end effector (not shown). As shown in  FIG. 64 , the backing layer  8402  has a plurality of female features in the form of openings  8404  formed thereon. The openings  8404  can mate with corresponding male features of the jaw (e.g., a cartridge or anvil). The openings  8404  can be configured to mate with the male features such that one opening can surround two or more male features. Thus, as illustrated in  FIG. 64 , the backing layer  8402  has several (e.g., two, three, or greater than there) openings formed therein each of which can surround more than one male feature (e.g., projections, posts, etc.) formed on the jaw. For example, one opening (or “window”)  8404  can surround a group of jaw&#39;s male features. Also, in some embodiments, only some of the openings  8404  will surround two or more male features. 
     Furthermore, in some embodiments, the backing layer can have one opening. For example, it can be a relatively large opening such that the backing layer can be in the shape of a frame that is coupled to the adjunct material along a perimeter of the adjunct. The frame-shaped backing layer can couple with a jaw via male features disposed on the jaw in a certain manner. For example, four or more male features (e.g., posts) can be disposed at opposed sides at the distal and proximal ends of the jaw and the frame-shaped backing layer, with the adjunct coupled thereto, can be retained on the jaw via such features received within the opening in the backing layer. 
     The openings  8404  can have any suitable configuration and size. For example, as shown in  FIG. 64 , the openings  8404  can be rectangular. However, they can alternatively be square, round, oval, etc. Also, the adjunct material can have openings of different sizes and/or shapes. The backing layer  8402  can be formed from one or more materials similar to the backing layer  8302  in  FIG. 63 . 
     Furthermore, although not shown separately in  FIGS. 63 and 64 , each of the adjunct materials  8300  and  8400  also includes one or more attachment features configured to releasable retain the adjunct material on the jaw. The attachment feature(s) can be in the form of an adhesive material layer, female, male, or other type of features that are used to retain the adjunct material on the jaw in all three dimensions. Furthermore, in some embodiments, the material from which the backing layer (e.g., backing layer  8302  in  FIG. 63  or backing layer  8402  in  FIG. 64 ) is formed can be an adhesive material serving as an attachment layer. The adhesive material can be any suitable polymer, such as polydioxanone (PDO), a low molecular weight polyethylene glycol (PEG) or any other material (or a combination of materials) that can be used to attach the adjunct to the jaw. In some embodiments, the adhesive material can be a bioabsorbable and/or biodegradable pressure sensitive adhesive. 
     In the example of  FIGS. 63 and 64 , the backing layer non-removably attached to the adjunct material on jaw-facing surface thereof is formed substantially over entire surface of the adjunct material. In some embodiments, the backing layer can be in the form of discrete portions. In this way, while some portions of the adjunct material can be prevented from being stretched, other portions can be stretched once the adjunct material is applied to tissue at a treatment site. The adjunct material can thus move with the tissue at which it is implanted when the tissue moves, while remaining being coupled to the tissue. This may be desirable when tissue such as, for example, lung is being treated, which needs to be able to expand and contract to perform its function. Allowing the implanted adjunct material to stretch to some degree allows the tissue to heal appropriately. 
       FIGS. 65 and 66  illustrate an example of an adjunct material  8500  to be disposed over a jaw  8501  which is, in this example, a cartridge. The adjunct material  8500  can however be disposed over an anvil as well. As shown in  FIG. 65 , the adjunct material  8500  has discrete portion or panels  8502 ,  8502   b ,  8502   c  forming a backing side or layer  8502 . As shown, the panels  8502 ,  8502   b ,  8502   c  non-removably attached to the adjunct material  8500  are disposed perpendicular to a longitudinal axis  8 A 3  of the adjunct material  8500 . It should be appreciated that three panels  8502 ,  8502   b ,  8502   c  are shown by way of example only, as two or greater than three panels can span the adjunct material  8500  along a short side thereof. 
     The adjunct material  8500  can be formed from any suitable material described herein, which can be a mesh or a non-woven material. The backing layer  8502  can also be formed from any suitable material, such as a biodegradable and/or bioabsorbable material, e.g., polydioxanone (PDO) or any other suitable polymeric material(s). The material can be selected such that it biodegrades and/or bioabsorbs faster than the adjunct material  8500 . The backing layer  8502  has a thickness that is smaller than that of the adjunct material  8500 . For example, in some embodiments, the height or thickness of the adjunct material  8500  can be from about 0.004 inches to about 0.020 inches, whereas the height or thickness of the backing layer  8502  can be from about 0.0002 inches to about 0.0012 inches. 
     As shown in  FIG. 66 , illustrating by way of example a back side of the adjunct material  8500  with the panels  8502 ,  8502   b ,  8502   c  when the adjunct material  8500  is retained at the treatment side (the staples and tissue are not shown), the panels  8502 ,  8502   b ,  8502   c  prevent stretching of the portions of the adjunct material  8500  to which the panels  8502 ,  8502   b ,  8502   c  are attached. As also shown, the portions of the adjunct material  8500  between the panels  8502 ,  8502   b ,  8502   c , such as portions  8503   a ,  8503   b  in  FIG. 64 , can stretch along the longitudinal axis  8 A 3  of the adjunct material  8500  once implanted on tissue. Thus, while the panels  8502 ,  8502   b ,  8502   c  prevent undesirable excessive stretching and displacement of the adjunct material  8500  at the treatment site, the portions of the adjunct material  8500  between the panels allow the adjunct stretching where desired. 
     It should be appreciated that the number, size, and location of the panels configured to prevent stretching of portions of the adjunct material can be selected to create a desired pattern of areas at which the adjunct is coupled to the jaw (e.g., the areas coupled to the panels) and areas at which the adjunct is allowed to stretch once implanted. In some embodiments, adjunct(s) that are at least partially stretchable at some portions thereof can be used in conjunction with a staple line that can be flexible as described, for example, in the above-mentioned U.S. Pat. Pub. No. 2016/0089142 entitled “Method for Creating a Flexible Staple Line,” and filed on Sep. 26, 2014, which is hereby incorporated by reference herein in its entirety. Such implementations can be used for treatment of tissue which contracts and expands, such as lung. Furthermore, in some embodiments, the panels, such as the panels  8502 ,  8502   b ,  8502   c , can be aligned with some staples and not others along the longitudinal length of the jaw. Also, when the adjuncts with the backing layer panels are disposed on both jaws of an end effector, the panels formed on the opposed adjuncts can have a pattern (e.g., a complementary pattern) such that a staple, once ejected, passes only through one of the backing layers. The panels and spacing between panels can be selected such that the panels form irregular and non-uniform patterns, and adhesive is applied to the panels. 
     As in other examples illustrating the described techniques, the adjunct material  8500  also includes one or more attachment features which can be in the form of an adhesive material layer formed at the jaw-facing surface of the panels  8502 ,  8502   b ,  8502   c . Other attachment features can be formed additionally or alternatively. Furthermore, in some embodiments, the material from which the panels  8502 ,  8502   b ,  8502   c  are formed can be an adhesive material serving as an attachment layer. The adhesive material can be any suitable polymer, such as polydioxanone (PDO), a low molecular weight polyethylene glycol (PEG) or any other material (or a combination of materials) that can be used to attach the adjunct to the jaw. In some embodiments, the adhesive material can be a bioabsorbable and/or biodegradable pressure sensitive adhesive. 
     It should be appreciated that the adjunct materials described herein can be used with various types of end effectors that can be used in linear or circular stapler instruments. For example, it can be used in a linear surgical stapler, such as stapler  10  in  FIG. 1  or stapler  50  in  FIG. 4 , or in a circular surgical, such as stapler  80  in  FIG. 5 , or in any other surgical stapler instrument. Thus, although generally rectangular adjuncts are shown in  FIGS. 59, 61, 63, 64, 65, and 66 , the adjuncts can be created such that they have a generally circular shape and such that their retaining and non-retaining features are configured for mating with an end effector of a circular stapler instrument. Also, as mentioned above, the adjunct can have or can be associated with various types “retaining” and “non-retaining” features. 
     Furthermore, the adjunct materials described herein can include one or more medicants which can be releasably incorporated into or associated with adjuncts in many different ways. Also, the adjunct materials can have various other features in addition to the features described herein. 
     Systems for Release of Adjunct in a Surgical Stapling Device 
     Implantable adjuncts can be releasably attached to a jaw of an end effector of a surgical stapling device. The coupling can be done in various ways, for example, adhesives and/or adhesive features can be used to couple the adjunct to a surface of the jaw. This can allow manipulating the end effector with the adjunct during a surgical procedure, while the adjunct is prevented from being prematurely separated from the surface of the jaw before the adjunct is stapled to a tissue. After the adjunct has been stapled to the tissue, the adjunct can be detached from the jaw by a force exerted by the tissue (e.g., shearing force, pull, etc.). Attaching systems (e.g., those using polydioxanone adhesives) that attach the adjunct to the surface of the jaw in a secure (strong) manner can be advantageous as they ensure that the adjunct does not slip or slide off the jaw&#39;s surface prior to the stapling to the tissue. A strong attachment however can make the adjunct removal process challenging. This challenge can be obviated by including an adjunct removal mechanism or assembly in a jaw of the surgical stapling device that is configured to separate the adjunct from the jaw. 
     Accordingly, an adjunct removal mechanism can be configured to detach the adjunct from the surface of the jaw of the surgical stapler device after the adjunct has been stapled to the tissue. This can be done for example, by using a motion of a firing bar (in the surgical stapling device) from a fired position at the distal end of the end effector to an unfired position at the proximal end of the end effector. The firing bar can couple to the adjunct removal mechanism at the distal end, and return back to the proximal end (i.e., unfired position) with the adjunct removal mechanism. The adjunct removal mechanism can include an adjunct removal feature that separates the adjunct from the jaw of the surgical stapler device as the adjunct removal mechanism moves from the distal to the proximal end. 
       FIG. 67A  illustrates an example of an adjunct  9502  releasably retained to a tissue facing surface of a lower jaw  9504  of an end effector of a surgical stapler device. One or more portions of the adjunct  9502  can be attached to the lower jaw  9504  by an adhesive  9508 . The adhesive  9508  can be disposed at any suitable pattern—for example, it can be distributed between the adjunct  9502  and lower jaw  9504  at distal and proximal ends of the adjunct  9502 , as shown in  FIG. 67A . The adhesive can be, for example, a pressure sensitive adhesive (PSA). Additionally or alternately, a second adhesive, for example, cyanoacrylate (CA), can attach the adjunct  9502  to the tissue facing surface of the lower jaw  9504 . For example, as shown in  FIG. 67A , one or more portions of the adjunct  9502  can be coupled to the jaw  9504  via attachment portions or points  9506  formed from the second adhesive. It should be appreciated, however, that the first and second adhesives can be the same material (e.g., a PSA, CA, etc.), or a combination of suitable materials. The adjunct  9502  can be attached to the lower jaw  9504  by various mechanisms, for example, as described in U.S. patent application Ser. No. 15/436,183 entitled “Hybrid Mechanism for Attachment of an Adjunct to a Surgical Instrument” filed on even date herewith, the entire content of which is incorporated herein by reference. 
     As shown in  FIG. 67A , the lower jaw  9504  includes a knife channel  9509  that extends longitudinally along the length of the lower jaw  9504 . The attachment points  9506  of the second adhesive (or any other adhesive) can be distributed, for example, along and/or around the knife channel  9509 . It should be appreciated however that four attachment points  9506  are shown by way of example only, as any suitable number of attachment points can be formed at any desired pattern(s). Further, in some embodiments, the attachment points, which can be configured to be broken by a suitable release mechanism, can be formed at areas at which the adjunct was heated and pressed onto the jaw and allowed to cool and thus conform to the geometry of the jaw. In this way, one or more portions of the adjunct mechanically “grip” the jaw (in some cases, in certain textured or roughened portions of the jaw). 
       FIG. 67B  illustrates the surgical stapler device clamping on a tissue  9510 . The tissue  9510  is clamped between an upper jaw  9512  and the lower jaw  9504  of the stapler. The adjunct  9502  lies between the tissue  9510 , and the tissue facing surface of the lower jaw  9504 . Due to the adjunct  9502 , portions of the tissue facing surface do not come in direct contact with the tissue  9510 . A distal end  9513  of a firing bar  9518  (e.g., an I-Beam, an E-Beam, or otherwise configured end) extends vertically with respect to the tissue facing surface. The distal end  9513  includes flanges  9514  configured to scrape the adjunct  9502  from the tissue-facing surface of the lower jaw  9504 . For example, the flange  9514  can cause adhesive  9506  to crack and thereby release portions of the adjunct  9502  when the firing bar  9518  moves from the proximal to the distal end or vice-versa. The flanges  9514  are shown as having slanted surfaces by way of example, and they can have other configurations. 
       FIG. 67C  illustrates a perspective view of an embodiment of the distal end  9513  of the firing bar  9518 . The distal end  9513  includes a knife  9516  and the flange  9514 . As the distal end  9513  travels from a proximal end to a distal end of the stapler, the knife  9516  cut the tissue  9510 . 
       FIGS. 67A-67C  illustrate that a knife of a firing bar assembly can be used to separate an adjunct from a jaw which has the adjunct releasably coupled thereto. In some embodiments, assemblies having other configurations can be used to separate an adjunct from a jaw of an end effector in conjunction with movement of the firing bar. 
       FIGS. 68A and 68B  illustrate an example of a jaw  9600  of an end effector  9607 . The end effector  9607  can be coupled to a distal end of a shaft of a surgical stapling device (not shown). The end effector  9607  can be used in any suitable surgical instrument, for example, a linear surgical stapler (e.g., stapler  10  in  FIG. 1 , stapler  50  in  FIG. 4 , or any other surgical stapler, including a circular stapler, such as stapler  80  in  FIG. 5 ) which can be suitable for use with at least one adjunct. 
     The end effector  9607 , shown partially in  FIGS. 68A and 68B , has a first jaw having a cartridge with a plurality of staple cavities configured to seat staples therein, the staple cavities opening on a tissue-facing surface of the cartridge. For example, the end effector  9607  includes the jaw  9600  in the form of cartridge having a plurality of staple cavities  9625  configured to seat staples  9623  therein. The staple cavities  9623  open on a tissue-facing surface  9609  of the cartridge  9600 . Although not shown in FIGS.  68 A and  68 B, the end effector  9607  also includes a second jaw opposing the first jaw in the form of the cartridge  9600  and having an anvil with a plurality of staple forming cavities formed on a tissue-facing surface thereof. The first and second jaws are configured to clamp tissue therebetween. 
     The end effector  9607  also includes an implantable adjunct material releasably retained on at least one of the first and second jaws. In particular, in this example, the jaw  9600  has an adjunct material or adjunct  9610  releasably retained on the tissue facing surface  9609  thereof. Although the jaw  9600  is also referred to herein as a cartridge, it should be appreciated that the jaw  9600  can have a staple channel configured to support a staple cartridge, which can be removably and replaceably seated within the staple channel. In some embodiments, the cartridge  9600  can be part of a disposable loading unit coupled distally to a shaft of a surgical instrument. The cartridge  9600  can be part of a cartridge reload assembly that is pre-assembled with an adjunct material. In such embodiments, a suitable adjunct loader can be used to attach an adjunct material to an anvil. 
     As shown in  FIGS. 68A and 68B , the cartridge  9600  includes a firing bar  9601  configured to move longitudinally between a proximal end  9602  and a distal end  9603  of the cartridge  9600 . The firing bar  9601  moves within a knife channel  9624  formed in the cartridge  9600  that extends longitudinally along the cartridge  9600  and guides the motion of the firing bar  9601  between the proximal and distal ends  9602 ,  9603 . The knife channel  9624  can extend through a cartridge in the lower jaw. In the illustrated example, the firing bar  9601  is configured to move between an unfired position at the proximal end  9602  of the end effector  9607  and a fired position at the distal end  9603  of the end effector  9607 . 
     The firing bar  9601  can have a variety of configurations. For example, in the illustrated embodiment, the firing bar  9601  includes at least one of a knife  9608  and a staple driving assembly  9615  configured to cause the staples  9625  to fire from the staple cavities  9623  against the staple forming cavities in the anvil (not shown). The distal end of the firing bar  9601  includes a distal guide  9604 . It should be appreciated that the firing bar  9601  can have any other components additionally or alternatively. 
     In use, when tissue is clamped between the jaw  9600  with the adjunct  9610  and the anvil of the end effector  9607 , as the firing bar  9601  moves from the unfired position to the fired position, the knife  9608  cuts through the adjunct  9610 . During this motion, the guide  9604  can engage a wedge sled (not shown) that pushes the staples  9625  held in the staple cavity  9623  upwards towards an upper jaw (not shown) of the stapling device. In the process, the staples  9625  can pass through the adjunct  9610  and the tissue into the anvil of the upper jaw that faces the tissue. When the first and the second jaws clamp on the tissue, the staple forming cavities of the anvil guide the staples and cause the tissue and the adjunct  9610  to be stapled together. 
     The adjunct  9610  can be releasably retained on the tissue-facing surface  9609  of the cartridge  9600 . The adjunct  9610  can be coupled to the tissue facing surface  9609  in various manners. For example, one or more adhesives (e.g., polydioxanone (PDS), CA, etc.) can be applied between the adjunct  9610  and the tissue-facing surface  9609  to releasably retain the adjunct  9610  on the cartridge  9600 . In some embodiments, a backing layer made, e.g., of a PDS film, can be used to couple the adjunct  9610  to the jaw  9600 . The backing layer can include one or more attachment points or portions (e.g., similar to the portions  9506 ,  9508  in  FIG. 67A ) that can be formed from an adhesive configured to be transitioned to an adhering state under application of heat. In other words, the adhesive can be at least partially melted (using, e.g., a loader configured to apply heat), in which state it can be used to couple the adjunct  9610  directly or via the PDS film to the jaw. When the attachment adhesive cools, it couples the adjunct  9610  (e.g., at one or more portions) to the jaw  9600  securely. Additionally or alternatively, various other features (e.g., additional polymer layer (s), attachment features, etc.) can be used to releasably couple the adjunct  9610  to the jaw  9600 . 
     Regardless of the manner in which the adjunct  9610  is coupled to the cartridge  9600 , the adjunct  9610  is coupled to the cartridge  9600  releasably, such that it is separated from the cartridge  9600  to remain with the tissue after the tissue stapling and/or cutting is completed during a surgical procedure. In some embodiments, the adjunct  9610  can be releasably coupled to the jaw  9600  in a secure manner, such that the end effector can be manipulated as desired, without the risk of the adjunct  9610  sliding or slipping off the jaw  9600 . At the same time, such secure attachment can require certain actions to separate the adjunct  9610  from the cartridge  9600 . 
     Accordingly, in the illustrated embodiments, the end effector  9607  includes an adjunct removal assembly  9630  configured to separate the adjunct  9610  from the cartridge  9600 . The adjunct removal assembly  9630  is configured to couple to and move with the firing bar  9601  to separate the adjunct material  9610  from the end effector  9607  as the firing bar  9601  having the adjunct removal assembly  9630  coupled thereto is returned from the fired position to the unfired position, as discussed in more detail below. For example, as the adjunct removal assembly  9630  is moved proximally with the firing bar after the assembly is engaged by the firing bar, the adjunct removal assembly  9630  can break or crack attachment points (formed, e.g., by a hot-melt adhesive) between the adjunct  9610  and the cartridge  9600 . In this way, the adjunct  9610  is separated from the cartridge. 
     As shown in  FIGS. 68A and 68B , the adjunct removal assembly  9630  is disposed at the distal end  9603  of the cartridge  9600 . The adjunct removal assembly  9630  is operably associated with the cartridge  9600 . As shown in  FIG. 68A , it can be disposed at the distal end  9603  of the end effector  9607  in a configuration in which the assembly  9630  is not coupled to the firing bar  9601  when the surgical stapling device is in a pre-fired configuration. The adjunct removal assembly  9630  can reside in the cartridge  9600  and it can move longitudinally along the knife channel  9624 . In use, as the firing bar  9601  moves from the unfired position at the proximal end  9603  of the end effector  9607  to the fired position at the distal end  9602  of the end effector  9607 , as shown by an arrow  9605  in  FIG. 68A , the adjunct removal assembly  9630  couples to firing bar  9601  as discussed in more detail below. This movement results in the knife  9608  cutting tissue disposed between the jaw  9600  and the anvil (not shown). When the firing bar  9601  moves proximally from the fired position to the unfired position, as shown by an arrow  9652  in  FIG. 68B , the adjunct removal assembly  9630  coupled thereto moves with the firing bar  9601 . 
     The adjunct removal assembly  9630  can have a variety of configurations. In the example illustrated, the assembly  9630  includes an adjunct removal feature  9614  and a mating feature  9612 . The adjunct removal feature  9614 , which can have various configurations, is configured to separate the adjunct  9610  coupled to the jaw  9600  from the jaw. The mating feature  9612  is configured to mate with a respective mating feature  9620  included in the firing bar  9601  when the firing bar  9601  is actuated to achieve the firing position. 
     As shown in  FIG. 68A , in a pre-fired configuration of the end effector  9607 , the adjunct removal feature  9614  is configured to be placed between the tissue-facing surface  9609  and the adjunct  9610 . As also shown, a leading edge  9617  of the adjunct removal feature  9614  is disposed between the tissue-facing surface  9609  and the adjunct  9610 . When the firing bar  9601  has moved to the fired position and couples in this position to the adjunct removal assembly  9630 , and then moves proximally to return to the per-fired configuration, the adjunct removal feature  9614  slides between the adjunct  9610  and the tissue facing surface  9609  thereby separating the adjunct  9610  from the jaw  9600 , as shown in  FIG. 68B . The leading edge  9617  of the adjunct removal feature  9614  facilitates separation of the adjunct  9610  from the jaw  9600 .  FIG. 68B  shows the assembly  9630  coupled to the firing bar  9601  being pulled by the firing bar  9601  towards the proximal end  9602  of the end effector  9607 . As the adjunct removal feature  9614  slides, it causes the adjunct  9610  to separate from the tissue facing surface  9609  of the jaw  9600 . 
     The mating feature  9612  of the assembly  9630  is configured to mate with the mating feature  9620  of the firing bar  9601 . The mating features  9612 ,  9620  can be complementary to one another. For example, the mating feature  9612  of the assembly  9630  can be in the form of one or more protrusions, whereas the mating feature  9620  of the firing bar  9601  can be in the form of one or more openings or cavities configured to mate with the protrusion(s). The protrusions configured to mate with the cavity in the firing bar can include, e.g., a pair of bars disposed such that the firing bar sits between the bars when the adjunct removal assembly  9630  is coupled to and moves with the firing bar. In particular, the bars can have a gap between them, as shown, for example, in  FIG. 69  (pair of bars  9714   a ,  9714   b ). In use, the distal end of the firing bar  9601  can slide into the gap between the pair of bars of the mating feature  9612 .  FIG. 68B  illustrates schematically (a circle  9632 ) the mating feature  9612  of the assembly  9630  coupled to the mating feature  9620  of the firing bar  9601 . For example, the bars are snapped into the mating feature  9620  (e.g., a cavity), which can be assisted by mating elements or features that can be formed on the bars. 
     An example of a surgical method in accordance with the described techniques includes actuating the firing bar  9601  so as to move it from an unfired position at the proximal end of the end effector to the fired position in the distal end of the end effector. The adjunct removal assembly  9630  is engaged with the firing bar  9601  when the firing bar  9601  is in the fired position, and the firing bar  9601  is actuated to return it from the fired position to the unfired position such that, as the firing bar  9601  is actuated to return to the unfired position, the adjunct removal assembly  9630  is moved with the fired bar  9601  and thereby causes the adjunct material  9610  releasably retained on the jaw  9600  to be separated from that jaw. 
     It should be appreciated that the adjunct removal assembly  9630  is shown in  FIGS. 68A and 68B  to be operatively coupled to the cartridge  9600  by way of example only. Thus, in some implementations, an adjunct can be attached to a tissue-facing surface of a jaw of the surgical stapling device having an anvil. In such implementations, the adjunct removal assembly can be configured to be operatively coupled to the anvil such that it can slide longitudinally with a firing bar to separate the adjunct from a tissue-facing surface of the anvil. It should be appreciated that the adjunct may not be entirely removed from the jaw until the jaws are unclamped. Thus, the adjunct can be associated with the jaw (e.g., held against the jaw, albeit not coupled to the jaw) until the jaws are unclamped. Once the jaws are separated, the adjunct can be fully separated therefrom. 
     An adjunct removal assembly used to separate an adjunct material from a jaw of an end effector in accordance with the described techniques can have a variety of configurations.  FIG. 69  illustrates an example of a portion of an adjunct removal system or assembly  9710 . The adjunct removal assembly  9710  can be similar, for example, to adjunct removal assembly  9630  in  FIGS. 68A and 68B . The adjunct removal assembly  9710  includes a stripper plate  9712 , a mating feature  9714 , and a pair of posts  9713   a ,  9713   b  coupling the stripper plate  9712  to the mating feature  9714 . The stripper plate  9712  serves as an adjunct removal feature, and it can have various configurations. In this example, it is generally rectangular, includes an adjunct-facing surface  9708  and a leading surface  9712   b  disposed at an angle with respect to the surface  9708  and having a sharp leading edge that can facilitate the removal of the adjunct from the tissue facing surface of the cartridge. The adjunct-facing surface  9708  is configured to have an adjunct disposed thereon. 
     As shown in  FIG. 69 , the stripper plate  9712  is coupled to the pair of elongate posts  9713   a ,  9713   b  that can be attached to a mid-portion or approximately mid-portion of a side of the stripper plate  9712  that is opposed to the adjunct-facing surface  9708 . The mating feature  9714  also includes a pair of bars  9714   a ,  9714   b  extending from the ends of the posts  9713   a ,  9713   b , respectively, that are opposed to the ends of the posts coupled to the stripper plate  9712 . As shown in  FIG. 69 , the bars  9714   a ,  9714   b  extend from the posts  9713   a ,  9713   b  such that the bars  9714   a ,  9714   b  form a gap  9715  therebetween. As shown in  FIG. 69 , the posts  9713   a ,  9713   b  also include a gap therebetween, and the gap  9715  can extend between the posts  9713   a  and  9713   b . The bars  9714   a  and  9714   b  include mating features  9716   a ,  9716   b , respectively (e.g., in the form of hooks facing one another), which can slide into a cavity in the distal end of the firing bar (not shown). As the distal end of the firing bar slides between the mating feature  9714  (into the gap  9715 ), it can push the bars  9714   a ,  9714   b  in an outward lateral direction. This can generate stress in the inward lateral direction that can cause the hook features  9716   a ,  16   b  to snap inwards into the cavity in the distal end of the firing bar. The mating feature  9714  can also guide the adjunct removal assembly  9710  through the knife channel as the adjunct removal system slides longitudinally with the firing bar. 
       FIG. 70  illustrates a top view of an example of a jaw  9800  of an end effector  9807  that can be coupled to a suitable surgical stapler device (not shown). The jaw  9800  is in the form of a cartridge and it can have an adjunct (not shown) removably coupled thereto. The jaw  9700  can be similar to jaw  9600  in  FIGS. 68A and 68B  and is therefore not described in detail. The end effector  9807  includes an adjunct removal assembly  9830 , shown schematically within a dashed area  9815 , that can be similar to adjunct removal assembly  9830  shown in  FIGS. 68A and 68B . Thus, as shown in  FIG. 70 , the adjunct removal assembly  9830  includes an adjunct removal feature  9814  and a mating feature  9812  configured to mate with a corresponding mating feature of a firing bar (not shown) when the firing bar is actuated to achieve a firing position. 
     The adjunct removal feature  9814  is shown disposed along a tissue-facing surface  9809  of the cartridge  9800 . The mating feature  9812  of the of the adjunct removal assembly  9830  can guide the assembly  9830  along a knife channel  9824  when the adjunct removal assembly  9830  is coupled to and moved with the firing bar from a distal end  9802  to a proximal end  9803  of the end effector  9807 . As shown by way of example only, the tissue-facing surface  9809  of the jaw  9800  can include features (e.g., rough surfaces  9862 ) that can facilitate attachment of the adjunct (not shown) to the jaw  9800 . For example, the rough surfaces  9862  can provide traction to the adjunct and can thus allow an adhesive layer (which can have various features) between the adjunct and the surface  9809  to form a stronger bond. 
       FIG. 71  illustrates the cartridge  9800  with an adjunct  9810  removably retained thereon. The adjunct removal assembly  9830  is shown partially and  FIG. 71  illustrates a relative orientation of adjunct  9810  and the adjunct removal feature  9814  of the adjunct removal assembly  9830 . In particular, in a pre-fired configuration of the end effector  9807 , the adjunct removal feature  9814  is disposed between the jaw  9800  and the adjunct  9810 . As illustrated, the adjunct removal feature  9814  has a sharp leading edge  9864  that can scrape the adjunct  9810  from the tissue facing surface  9809  of the cartridge  9800 . As discussed above, in a fired configuration, the adjunct removal assembly couples to and moves with a firing bar (not shown) to separate the adjunct material from the cartridge  9800  as the firing bar having the adjunct removal assembly coupled thereto is returned from the fired position to the unfired position. 
     It should be appreciated that, an adjunct material can be releasably coupled to at least one jaw of an end effector using various techniques. For example, as mentioned above, the adjunct material can be coupled to the jaw using an adhesive configured to transition from a non-adhering state to an adhering state under application of heat. Non-limiting examples of the systems that can be used to releasably couple the adjunct material to a jaw of an end effector are described in a U.S. patent application Ser. No. 15/436,328 entitled “Systems for Coupling Adjuncts to an End Effector” and filed on even date therewith, the content of which is incorporated by reference herein in its entirety. 
     It should also be appreciated that an adjunct removal assembly operatively coupled to an end effector can have a variety of configurations. For example, in some embodiments, the adjunct removal assembly can include a cutting element, such as a suture, string, or wire, that is “picked up” by a firing bar (e.g., by a knife) as the firing bar returns to an unfired position. As adjunct removal assembly is moved proximally with the returning firing bar, the cutting element separates the adjunct from the jaw. 
     Hybrid Mechanism for Attachment of an Adjunct to a Surgical Instrument 
     In general, when using an adjunct in conjunction with a surgical stapler, the adjunct can be removably attached to the end effector. The adjunct will preferably remain secured to the end effector while the end effector is positioned at a treatment site, and is removed from the end effector when staples are deployed at the treatment site to provide the benefits discussed above. 
     It has been observed that adjuncts can prematurely detach from the end effector prior to staple deployment. Detachment of the adjunct from the end effector can occur in various forms, depending on the manner in which the end effector is used. For example, detachment can include vertical lift off of the adjunct from the end effector, lateral sliding of the adjunct with respect to the end effector, and/or curling of the edges of the adjunct from the surface of the end effector. The adjunct could also slide sideways when an end effector is used to clamp and twist tissue. 
     Various exemplary devices, systems, and methods for attaching an adjunct to a surgical instrument are described herein. In general, a hybrid attachment mechanism is employed to attach an adjunct to an end effector jaw of a surgical stapler. In some embodiments, the hybrid attachment mechanism includes at least two attachment mechanisms, where each mechanism is configured to inhibit at least one form of adjunct detachment from the end effector jaw. For example, a first attachment mechanism can be configured to inhibit vertical removal of the adjunct from the jaw. A second attachment mechanism can be configured to inhibit sliding of the adjunct with respect to the jaw. A third attachment mechanism can be configured to inhibit curling of the adjunct upon itself. Each of the first, second, and third attachment mechanisms can operate in concert with the others, allowing the hybrid attachment mechanism to simultaneously inhibit multiple forms of adjunct detachment. The hybrid attachment mechanism can be further configured to decouple from the end effector jaw, permitting deployment of the adjunct at a treatment site. 
     Embodiments of the hybrid attachment mechanism are discussed below in conjunction with the stapler  10 , where an adjunct is coupled to a tissue contacting surface  33  of the upper jaw  34  of an end effector  30 . However, it may be understood that embodiments of the hybrid attachment mechanism can be employed with any surgical instrument without limit. Furthermore, embodiments of the hybrid attachment mechanism can be employed to couple adjuncts with the tissue contacting surface  33  of the upper jaw  34 , a tissue contacting surface of the lower jaw  32 , and combinations thereof. 
       FIGS. 72-74  show an adjunct  10500  disposed upon a tissue contacting surface  33  (an anvil surface) of an upper jaw  34  including staple forming pockets  10043  and a hybrid attachment mechanism configured to couple the adjunct  10500  to the tissue contacting surface  33 . The hybrid attachment mechanism includes a first attachment mechanism  10502 , a second attachment mechanism  10504 , and a third attachment mechanism  10506 . 
     In one embodiment, the first attachment mechanism  10502  can be configured to maintain the adjunct  10500  on the tissue contacting surface  33 . For example, the first attachment mechanism  10502  can be configured to inhibit out-of-plane deformation of the adjunct  10500  and prevent vertical removal of the adjunct  10500  from the tissue contacting surface  33 . In a specific embodiment, the first attachment mechanism can be an adhesive  10502  (e.g., a biocompatible adhesive) that adheres the adjunct  10500  to the tissue contacting surface  33 . As illustrated in  FIGS. 72-74 , the adhesive  10502  is disposed between the tissue contacting surface  33  and the adjunct  10500 . Adhesives can include, but are not limited to, pressure sensitive adhesives (PSAs), heat activated adhesives, heat softened adhesives, ultraviolet (UV) cured adhesives, cyanoacrylate-based adhesives, moisture-softened adhesives, and hydrogel-based adhesives. 
     Mechanical properties of the adhesive  10502  can be selected within ranges suitable to ensure that out-of-plane deformation of the adjunct  10500  is inhibited during placement of the surgical stapling device  10  at a treatment site and that the adjunct  10500  is released from the tissue contacting surface  33  when secured to tissue by one or more staples. Examples of suitable mechanical properties can include, but are not limited to, adhesion strength (peak load) and load-displacement response. These mechanical properties can be measured by one or more mechanical tests including, but not limited to, tension, compression, peel (90°, 180°, T), release force, loop tack, shear, and flexure performed at service temperatures (e.g., within the range between about room temperature and body temperature). 
     While the first attachment mechanism  10502  can act to inhibit out-of-plane deformation, it may fail to prevent in-plane deformation. For example, the adhesive  10502  can stretch longitudinally in response to applied in-plane tensile stresses, such as when sliding on tissue or when the knife (e.g., knife  36 ) is fired. As a result, at least a portion of the applied in-plane tensile stress can be felt by the adjunct  10500  and can cause longitudinal elongation of the adjunct  10500 . 
     Accordingly, in another embodiment, the second attachment mechanism  10504  can be configured to inhibit in-plane (e.g., lateral and/or longitudinal) sliding or deformation of the adjunct  10500  along the tissue contacting surface  33 . In one embodiment, the second attachment mechanism  10504  can include at least one post  10504   a  formed on one of the adjunct  10500  and the tissue contacting surface  33  and a corresponding bore  10504   b  formed on the other one of the adjunct  10500  and the tissue contacting surface  33  that is configured to receive its corresponding post  10504   a . For example, the bore  10504   b  can have a diameter less than, greater than, or approximately equal to that of the post  10504   a  ( FIG. 73 ). By combining the first attachment mechanism  10502  and the second attachment mechanism  10504 , improved resistance to in-plane sliding or deformation is provided by the hybrid attachment mechanism. 
     In order to tailor the degree of resistance to in-plane sliding or deformation, the number of posts  10504   a , the size of the posts  10504   a , and their relative position with respect to the tissue contacting surface  33  can be varied. For example, as illustrated in the embodiment of  FIGS. 72-74 , multiple posts  10504   a ,  10504   b  are formed on the tissue contacting surface  33  and multiple respective bores  10504   c ,  10504   d  are formed on the adjunct  10500 . The posts  10504   a  have a relatively larger diameter than the posts  10504   b  and are positioned adjacent to the proximal end  10034   p  and distal end  10034   d  of the jaw  34 . As further illustrated in the embodiment of  FIG. 72 , the number of posts  10504   b  can be greater than the number of posts  10504   a . In this configuration, the posts  10504   a  can act to inhibit sliding of the corners of the adjunct  10500 , while the posts  10504   b  can act to inhibit stretching of the adjunct  10500  along its length. 
     Under certain circumstances, ability of the first attachment mechanism  10502  or the second attachment mechanism alone to prevent the adjunct  10500  from curling upon itself can be impaired in service. For example, in the context of the first attachment mechanism  10502 , mechanical stresses experienced by the adjunct  10500  or the jaw  34  can overcome the adhesion strength of the adhesive. Alternatively, in the context of the second attachment mechanism  10504 , mechanical stresses experienced by the adjunct  10500  or the jaw  34  can damage the posts  10504   a . In either case, the ability of the first attachment mechanism  10502  or the second attachment mechanism  10504  to prevent the adjunct  10500  from curling upon itself can be overcome. Furthermore, it is observed that curling of the adjunct  10500  tends to occur most frequently at the distal end  10034   p  of the jaw  34  because the distal end  10034   p  of the jaw can frequently experience elevated stresses due to contact with tissue during use of the end effector  30 . 
     Thus, in another embodiment, the third attachment mechanism  10506  can be configured to inhibit in-plane movement or deformation of the adjunct  10500  near a distal end of the jaw  34 . Assuming the adjunct  10500  possesses an in-plane area that is approximately the same as the area of the tissue contacting surface  33 , the third attachment mechanism  10506  can be configured to inhibit in-plane movement or deformation of a distal end of the adjunct  10500  proximate to the tissue contacting surface  33 . For example, the third attachment mechanism  10506  can be configured to apply a compressive force to a distal-most end of the adjunct  10500  when secured to a distal-most end of the jaw  34 . 
     As illustrated in the embodiment of  FIGS. 72 and 74 , in one embodiment, the third attachment mechanism  10506  can be a clip that reversibly couples to the jaw  34  to selectively permit or inhibit separation of the distal end of the adjunct  10500  from the distal-most end of the tissue contacting surface  33 . The illustrated clip includes a base  10506   a  connected to an arm  10506   b . The illustrated clip is formed in a “U” or hook shape, with the arm  10506   b  overlying the base  10506   a . A socket  10510  can be formed in the distal-most end of the jaw  34  and extends longitudinally inward therefrom and is dimensioned to receive the base  10506   a . When the illustrated clip is coupled to the jaw  34 , the arm  10506   b  extends over the adjunct  10500  and can exert the compressive force upon distal-most end of the adjunct  10500 . This compressive force prevents the distal end of the adjunct  10500  from separating from the distal-most end of the tissue contacting surface  33 . By varying the separation of the base  10506   a  and the arm  10506   b , and/or an elastic modulus of the clip, the compressive force can be varied. Alternatively, when the base  10506   a  of the clip is removed from the socket  10510 , the arm  10506   b  of the clip does not extend over the adjunct  10500  and does not exert the compressive force upon distal-most end of the adjunct  10500 , allowing separation of the distal-most end of the adjunct  10500  from the tissue contacting surface  33 . 
     The third attachment mechanism  10506  can be configured to decouple from the jaw  34  upon ejection of a staple by the firing system. For example, as illustrated in  FIGS. 72 and 74 , the base  10506   a  can be aligned with a path of the knife blade  36 . When the firing system is activated, the staples are ejected from the staple cartridge  40  and the knife blade  36  is advanced through the jaw  34 . The advancement of the knife blade  36  can be sufficient to push the base  10506   a  out of the socket  10510 , decoupling the third attachment mechanism  10506  from the jaw  34 . 
     The third attachment mechanism  10506  can be further configured to operate in combination with the second attachment mechanism  10504 . For example, as illustrated in the embodiment of  FIG. 72 , at least one post  10504   a  is formed proximal to the portion of the adjunct  10500  over which the arm  10506   b  extends and applies the compressive force. That is, when the clip is coupled to the jaw  34 , the arm  10506   b  does not overlie any of the posts  10504   a . Thus, the posts  10504   a  do not interfere with application of the compressive force to the adjunct  10500  by the arm  10506   b . Furthermore, in addition to preventing curling of the adjunct  10500  at the distal-most end of the adjunct  10500 , the compressive force exerted by the arm  10506   b  upon the adjunct  10500  can also act to inhibit in-plane sliding or deformation (longitudinally or laterally) of the distal end of the adjunct  10500 . 
       FIGS. 75 and 76  illustrate another embodiment of a hybrid attachment mechanism configured for use with the stapler  10  and coupling the adjunct  10500  to a tissue contacting surface of the jaw  32 . However, it may be understood that embodiments of the hybrid attachment mechanism can be employed with any surgical instrument without limit. Furthermore, embodiments of the hybrid attachment mechanism can be employed to couple adjuncts with the tissue contacting surface  33  of the upper jaw  34 , a tissue contacting surface of the jaw  32 , and combinations thereof. 
     The hybrid attachment mechanism can include the first attachment mechanism  10502 , the second attachment mechanism  10504 , and a fourth attachment mechanism  10800 . As illustrated in  FIG. 75 , the first attachment mechanism  10502  is provided in the form of longitudinal strips adjacent to a slot  10802  that receives the knife  36  and the second attachment mechanism  10504  is provided in the form of the posts  10504   a  and/or  10504   b  are arranged along the length of the jaw  32 , adjacent the lateral sides. 
       FIG. 76  illustrates the fourth attachment mechanism  10800  in combination with the adjunct  10500 . The fourth attachment mechanism  10800  includes sutures that encircle a periphery of the jaw  32 . For example, two sutures are positioned adjacent to a proximal end  10032   p  and a distal end  10032   d  of the jaw  32 . However, any number of sutures can be provided and their location can be varied, as necessary. The sutures are configured to exert a compressive force upon the adjunct  10500 , inhibiting longitudinal and/or lateral sliding of the adjunct  10500  with respect to the jaw  32 , as well as vertical separation of the adjunct  10500  with respect to the jaw  32 . Thus, by combining the first attachment mechanism  10502 , the second attachment mechanism  10504 , and the fourth attachment mechanism  10800 , the hybrid attachment mechanism can provide improved resistance to out-of-plane deformation, maintaining the adjunct  10500  is on the tissue contacting surface  10804 , as well as improving resistance to in-plane sliding or deformation. 
     In further embodiments, the fourth attachment mechanism  10800  can be configured to decouple from the jaw  32  to permit the adjunct  10500  to separate from the jaw  32 . For example, the sutures extend laterally across the width of the jaw  32 , intersecting the slot  10802 . When the firing system is activated, staples are ejected from the staple cartridge  40  and the knife blade  36  is advanced through the jaw  32  within the slot  10802 . The advancement of the knife blade  36  cuts the sutures, decoupling the third attachment mechanism  10506  from the jaw  34 . 
     It may be understood that, while embodiments of the hybrid attachment mechanism discussed above include the first attachment mechanism  10502 , the second attachment mechanism  10504 , and the third attachment mechanism  10506 , alternative embodiments of the hybrid attachment mechanism can include any two of the first attachment mechanism  10502 , the second attachment mechanism  10504 , the third attachment mechanism  10506 , and the fourth attachment mechanism  10800 . For example, the hybrid attachment mechanism can include the first attachment mechanism  10502  and the second attachment mechanism  10504 , without the third attachment mechanism  10506 . Alternatively, the hybrid attachment mechanism can include the first attachment mechanism  10502  and the third attachment mechanism  10506 , without the second attachment mechanism  10504 . Additionally, the hybrid attachment mechanism can include the second attachment mechanism  10504  and the third attachment mechanism  10506 , without the first attachment mechanism  10502 . Alternatively, the hybrid attachment mechanism can include the first attachment mechanism  10502  and the fourth attachment mechanism  10800 . 
     Systems for Coupling Adjuncts to an End Effector 
     Adjunct materials can be applied to one or both jaws of an end effector of a surgical instrument in various ways. For example, an adjunct material can be manually positioned on a jaw. It is desired to releasably couple an adjunct to a jaw such that the adjunct does not slip off the jaw prior to application of the adjunct to tissue when staples are fired. However, some approaches may not result in a secure enough attachment of the adjunct to a jaw. This compromises the ability of a surgeon to manipulate the surgical instrument with the adjunct as desired during the surgical procedure. 
     Accordingly, in some embodiments, systems and methods are provided for applying an adjunct material to a jaw of an end effector to be releasably retained thereon. The adjunct material can be coupled to the jaw using an adhesive that can be applied to the adjunct and/or the jaw in a controlled manner. In some implementations, the adjunct material can be coupled to the jaw via an intermediate polymer layer. 
     In some embodiments, an adjunct loading member of a loading system can be used that is configured to releasably hold at least one adjunct material. The adjunct material is configured to be transferred from the adjunct loading member to a jaw of first and second jaws of an end effector. A supporting member of a suitable configuration is configured to releasably retain the adjunct material that can be associated with the supporting member in various ways. For example, the adjunct material can be disposed on the supporting member. Additionally or alternatively, the supporting member can be in the form of retaining feature(s) releasably holding the adjunct material in the adjunct loading member. The adjunct loading member also includes an adhesive depot having an adhesive configured to transition from a non-flowable state to a flowable state upon the application of heat when the adjunct material is released from the adjunct loading member and transferred to the jaw. Once the adhesive in the flowable state is cooled, it adheres to the jaw and is thus used to retain the adjunct material on the jaw. 
     The adjunct material is configured to be released from the adjunct loading member under application of a load. The adjunct is transferred to the jaw and is caused to adhere to the jaw using the adhesive disposed in the adhesive depot when the adhesive is in the flowable state. Heat can be applied to the adhesive prior to or at least partially at the time when the adjunct is being released from the adjunct loading member to the jaw. The load can be applied by the jaws of the end effector when the adjunct loading member is clamped therebetween. Alternatively, the load can be applied to the adjunct loading member manually or in other ways. The application of at least one of load and heat causes the adhesive from the adhesive depot to be used to retain the adjunct material on the jaw of the end effector. 
       FIG. 77  illustrates an example of a portion an end effector  11100  configured to releasably retain an adjunct material on one or both of its first and second opposed jaws configured to clamp tissue therebetween, in accordance with the described techniques. The end effector  11100 , partially illustrated in  FIG. 77 , has a first jaw having a cartridge body or cartridge  11102  and a second jaw having an anvil (not shown), with the first and second jaws being configured to clamp tissue therebetween. The cartridge body  11102  is configured to releasably retain thereon an implantable adjunct material  11106 . The end effector  11100  can be coupled to a distal end of a shaft of the surgical instrument (not shown). The end effector  11100  can be used in any suitable surgical instrument, for example, a linear surgical stapler (e.g., stapler  10  in  FIG. 1 , stapler  50  in  FIG. 4 , or any other surgical stapler, including a circular stapler, such as stapler  80  in  FIG. 5 ) which can be suitable for use with at least one adjunct. 
     As shown in  FIG. 77 , the cartridge body  11102  has a plurality of staple or staple-holding cavities  11108  configured to seat staples therein, the staple-holding cavities  11108  opening on a tissue-facing surface  11110  of the cartridge  11102 . The staple cavities  11108  form a certain pattern on the surface of the cartridge  11102  which corresponds to a pattern of staple-forming cavities formed in the anvil (not shown). The cartridge  11102  includes a cutting element or knife channel  11113  extending between distal and proximal ends  11102   d ,  11102   p  of the cartridge  11102 . The knife channel  11113  is configured to receive a cutting element (e.g., a knife) as it moves distally therethrough. As shown in  FIG. 77 , the staple cavities  11108  can form three rows on both sides of the cutting element channel  11113 , though it should be appreciated that the staple cavities  11108  can form any other patterns on the tissue-facing surface  11110 . 
     The cartridge body  11102  can be in the form of a staple channel configured to support a staple cartridge, which can be removably and replaceably seated within the staple channel. Furthermore, in some embodiments, the cartridge  11102  can be part of a disposable loading unit coupled distally to a shaft of a surgical instrument. 
     In this example, the end effector  11100  is configured to releasably retain thereon the implantable adjunct material (or “adjunct”)  11106 . In the illustrated implementation, the adjunct material  11106  releasably retained on the cartridge  11102  is discussed, though it should be appreciated that the anvil can also have an adjunct material releasably retained thereon. The adjunct material  11106  can be applied to the cartridge  11102  using a loading member of a loading system, such as an adjunct loading member  11200  shown in  FIG. 79  and discussed in detail below. 
     Regardless of the configuration of the loading member, the adjunct material  11106  is configured to be transferred from the loading member to the cartridge  11102  using an adhesive depot having an adhesive configured to transition from a non-flowable state to a flowable state upon the application of heat when the adjunct material is released from the adjunct loading member and transferred to the jaw to retain the adjunct material on the jaw. The adhesive depot can have a variety of configurations and it can be configured to allow the adhesive to be released therefrom in a variety of ways. In this example, as shown in  FIG. 77 , the adhesive depot is in the form of protrusions formed on a polymer attachment layer or polymer layer  11112  disposed on a jaw-facing surface of the adjunct material  11106 , as also shown schematically in  FIG. 78 . In particular, the polymer layer  11112 , shown in  FIG. 77  with its jaw-facing surface  11115  facing up for the illustration purposes only, has a plurality of protrusions  11114  including or formed from an adhesive. In  FIG. 77 , the polymer layer  11112  has two shorter protrusions (collectively referred to as  11114   a ,  11114   b ) at each of distal and proximal ends  11112   d ,  11112   p  thereof, respectively, and two longer protrusions  11114   c  disposed between the protrusions  11114   a ,  11114   b . The pairs of protrusions  11114   a ,  11114   b ,  11114   c  are formed along a longitudinal axis  11 A 2  of the polymer layer  11112 , and symmetrically with respect to a centerline of the polymer layer  11112 . 
     As shown in  FIG. 77 , the tissue-facing surface  11110  of the cartridge  11102  can include attachment features  11116  configured to engage the protrusions  11114 . In particular, the adhesive included in the protrusions  11114  or from which the protrusions  11114  are formed can be disposed on the attachment features  11116 . The attachment features  11116  can have various configurations. For example, they can be formed as recesses in the cartridge  11102 . Additionally or alternatively, the attachment features  11116  can include a roughness pattern, which can be formed in any suitable manner. The roughness pattern can have any suitable texture. For example, in one embodiment, the attachment features  11116  can be formed by making grooves having a pattern of multiple “Xs” (or other shapes or features) on the surface of the jaw. In this example, the cartridge  11102  is shown to have six attachment features formed at the distal and proximal ends  11102   d ,  11102   p  thereof, symmetrically with respect to the channel  11113 . It should be appreciated however that a cartridge of an end effector can include any other number of the attachment features (e.g., less then eight or greater than eight). 
     The protrusions  11114  formed on the polymer layer  11112  and the attachment features  11116  formed on (or in) the cartridge  11102  can have various shapes, including different shapes. For example, they can be generally elongate and rectangular, as shown in  FIG. 77 . Additionally or alternatively, they can be square, semi-circular (e.g., having a semi-circular or oval shape as viewed from the top), and/or they can have any other suitable regular or irregular shapes. 
     In some embodiments, at least one protrusion can be formed at a location on the polymer layer corresponding to a location of an attachment feature formed on the jaw. Thus, as shown in  FIG. 77 , the six protrusions  11114  are formed on the polymer layer  11112  at locations that correspond to the locations of the six attachment features  11116 . The length and width of the protrusions  11114  can be different from those of the attachment features  11116 . In addition, in some cases, one protrusion can be disposed over more than one attachment feature, and vise versa. Thus, the protrusions formed on the polymer layer and the attachment features formed on the jaw can form various patterns and can correspond to one another in various manners. 
     Regardless of the specific number, size, and locations of adhesive protrusions formed on the polymer layer  11112 , the polymer layer  11112  is used to attach the adjunct material  11106  to the cartridge  11102 . The surface of the polymer layer  11112  that is opposed to the surface  11115  on which the protrusions  11114  are formed can be coupled to the adjunct material  11106  in various ways. For example, at least a portion of the polymer layer  11112  can be formed from a pressure-sensitive adhesive such that the adjunct material  11106  can be coupled with the polymer layer  11112  that is, in turn, coupled with the jaw. 
     In some embodiments, as shown in  FIG. 77 , the end effector  11100  can include an additional polymer layer  11118  shown in the form of two portions. The additional polymer layer  11118  can be disposed between the adjunct material  11106  and the polymer layer  11112  or between the polymer layer  11112  and the cartridge  11102 . The additional polymer layer  11118  can be formed from an adhesive configured to transition from a non-flowable state to a flowable state upon the application of heat. Thus, when the additional polymer layer  11118  is configured to be disposed between the polymer layer  11112  and the cartridge  11102 , it is effectively additionally used to couple the adjunct material  11106  to the jaw  11102 . It should be appreciated however that the additional polymer layer  11118  is optional and may not be present. 
     The adjunct material  11106  can be formed from any suitable material or a combination of materials, which are discussed above. In some embodiments, the adjunct material  11106  can have a thickness of from about 0.006 inches to about 0.008 inches. In some embodiments, the adjunct material  11106  can have a thickness of from about 0.004 inches to about 0.0160 inches. The polymer layer can have a thickness of from about 0.002 inches to about 0.025 inches, and projections  11116   d ,  11116   p  can have a height or thickness of from about 0.005 inches to about 0.025 inches. 
     As mentioned above, in the described embodiments, the adjunct material is configured to be transferred from an adjunct loading member to a jaw of an end effector.  FIGS. 79 and 80  show an example of an adjunct loading member  11200  of a loading system that is configured to release the adjunct material to retain the adjunct material in the jaw, using at least one of heat and load (force).  FIG. 79  shows a top view of the adjunct loading member  11200 , whereas  FIG. 80  shows a cross-sectional view of the adjunct loading member  11200  when it is disposed on a jaw  11202  of an end effector. 
     As in the illustrated example, the adjunct loading member  11200  can be the form of a generally rectangular frame-like holder configured to releasably couple one or more adjuncts to one or both jaws of the end effector (not shown in  FIGS. 79 and 80 ). In the illustrated example, the adjunct loading member  11200  is in the form of a first (e.g., top) and second (e.g., bottom) generally rectangular housings  11204 ,  11205  coupled to one another e.g., via a coupling member. In this example, the adjunct loading member  11200  can be used to apply a single adjunct to a jaw. It should be appreciated however, that, in some embodiments, a loader like the adjunct loading member  11200  or a similar loader, can be used to apply a respective adjunct to each jaw of an end effector. 
     As shown in  FIG. 79 , the adjunct loading member  11200  includes at least one heating component  11208  configured to be activated to apply heat to an adhesive depot having an adhesive configured to transition from a non-flowable state to adhering flowable state upon the application of heat. In this example, as shown in  FIG. 80 , the adjunct loading member  11200  can retain thereon an adjunct material  11206  and a polymer layer  11212  having protrusions  11214 . The adjunct material  11206  and the polymer layer  11212  can be similar, for example, to the adjunct material  11106  and the polymer layer  11112 , though any suitable number of the protrusions  11214  can be formed on the polymer layer  11212 . 
     As shown in  FIG. 79 , the adjunct material  11206  can be releasably retained on a supporting member  11220  that can be configured in any suitable manner so as to retain the adjunct material  11206 . The supporting member  11220  that can have or can be in the form of, for example, retaining features (not shown) configured to releasably hold the adjunct material  11206 . The adjunct material  11206  can be disposed in any suitable way with respect to the supporting member. For example, in some embodiments, the supporting member  11220  can be in the form of features formed on one or more sides of the adjunct material  11206 . In this way, when load is applied to the adjunct loading member  11200 , the supporting member  11220  is caused to release the adjunct material  11206  therefrom, thus causing the adjunct material to be transferred to a jaw of an end effector.  FIG. 80  illustrates by way of example a jaw of an end effector in the form of a cartridge  11202  that has the adjunct loading member  11200  associated wherewith. The cartridge  11202  is shown in  FIG. 80  to have the adjunct material  11206  transferred thereto and coupled thereto using the polymer layer  11212 . It should be appreciated that, although not shown in  FIG. 80 , in use, the load is applied to the adjunct loading member  11200  by a first jaw having an anvil and the second jaw having cartridge  11202  that are clamped together with the adjunct loading member  11200  disposed therebetween. 
     In the described embodiments, the adjunct material  11206  is transferred from the adjunct loading member  11200  to the cartridge  11202  under application of load and the adjunct material  11206  is caused to be retained on the cartridge  11202  using an adhesive that is caused to transition to a flowable state under application of heat. Thus, in use, the adjunct loading member  11200  releasably holding the adjunct material  11206  is positioned between the jaws of the end effector (only the cartridge  11202  of the end effector is shown in  FIG. 80 ). To transfer the adjunct material  11206  from the adjunct loading member  11200  to the jaw  11202 , the first and second jaws are approximated to thereby apply load to the adjunct loading member  11202 , which causes the adjunct material  11206  to be released from the adjunct loading member  11200 . The adjunct loading member  11200  can be configured such that it exposes the side of the polymer layer  11212  (having the adjunct  11206  coupled thereto) having the protrusions  11214 . The application of load can cause the supporting member  11220  and, in some implementations, other portions or features of the adjunct loading member  11200  to crack, break, deform (e.g., bend, flex, etc.) or otherwise change their configuration to thereby release the adjunct  11206  from the adjunct loading member  11200 . In some embodiments, the housings  11204 ,  11205  of the adjunct loading member  11200  can be configured to deform or break to release the adjunct  11206  from the adjunct loading member  11200  when the adjunct loading member  11200  is clamped between the jaws  11200  (and not shown) of the end effector such that the load is applied thereto. As such, the adjunct  11206  can be “squeezed out” of the adjunct loading member  11200 . The adjunct loading member  11200  can be disposable such that it can be discarded after the adjunct  11206  (and the polymer layer  11212  coupled thereto) is transferred to the jaw. 
     Heat is applied to at least a portion of an adhesive depot such as the protrusions  11214  of the polymer layer  11212  having an adhesive and disposed in the adjunct loading member  11200  in association with the adjunct material  11206 , which causes the adhesive to transition from a non-flowable state to adhering flowable state when the adjunct material  11206  is released from the adjunct loading member  11200  and transferred to the jaw  11202 . For example, under the application of heat, the adhesive from which the protrusions  11214  are formed can transition from a substantially non-liquid state (in which it is in the non-flowable state) to at least partially liquid state (in which the adhesive is in the flowable state). In the at least partially liquid state, the protrusions  11214  can become less viscous such that their material can flow and interconnect or adhere with the surface of the cartridge  11202 . The cartridge  11202  can have attachment features (e.g., similar to the attachment features  11116  in  FIG. 77 ) that can have the protrusions  11214  in the flowable state disposed thereon such that the protrusions  11214  on the polymer layer  11212  adhere to the surface of the cartridge  11202 . Because the polymer layer  11212  is coupled to the adjunct material  11206 , adhering the polymer layer&#39;s protrusions  11214  to the cartridge  11202  causes the adjunct material  11206  to be releasably retained on the jaw  11202 . When the material from which the protrusions  11214  are formed is cooled and thus transitions to the flowable state, the protrusions  11214  remain attached to the cartridge  11202 . 
     In some embodiments, the adjunct loading member  11200  can be activated (e.g., using a button, switch, or other suitable trigger on the member  11200  or a remote trigger), to apply heat to the polymer layer  11212  before (or as) the load is applied to the adjunct loading member  11200 . For example, the heating component  11208  can be activated before the adjunct loading member  11200  is positioned between the jaws of the end effector. The adjunct loading member  11200  can be configured to deliver to the polymer layer  11212  heat of a desired temperature (e.g., in a range of from about 105° C. to about 220° C.) for an appropriate duration of time (e.g., from about 5 seconds to about 60 seconds) such that the application of heat causes the protrusions  11214  of the polymer layer  11212  to transition from the non-flowable state to the flowable, deformable state. In some embodiments, an indicator configured to indicate that the adhesive has been sufficiently heated to the deformable state can be activated. This can be, for example, a light indicator, an audio indicator, etc. 
     Once the protrusions  11214  are in the flowable state, the adjunct loading member  11200  can be disposed between the approximated jaws that cause the protrusions  11214 , and thus the adjunct  11206  coupled thereto, to attach to the jaw  11202 . Furthermore, in some embodiments, heat can be applied once the adjunct loading member  11200  is disposed between the jaws but prior to the jaws applying the load to the adjunct loading member  11200 . As another variation, the adjunct loading member  11200  can be activated to apply heat to at least a portion of the polymer layer  11212  and adjunct  11206  at least partially simultaneously with the load being applied to the adjunct loading member  11200 . 
     Regardless of the specific timing of the application of load and heat to the adjunct  11206  and polymer layer  11212 , the adhesive of the protrusions  11214  is caused to transition to the flowable state in which the protrusions  11214  attach to the jaw  11202  thus causing, after the heat is no longer applied, the polymer layer  11212  to be attached to the jaw. The application of at least one of the load and heat can also cause the adjunct  11206  to couple to the polymer layer  11212 . 
     The heating component  11208  can have various configurations. For example, as shown in  FIG. 79 , the heating component  11208  includes a resistive heating element  11224  in the form of a wire, which is connected to a power source  11216 . In the illustrated example, as shown, the heating element  11224  includes higher resistance portions  11218  along its length. The locations of the higher resistance portions  11218  can correspond to regions on the polymer layer to which heat is desired to be applied, e.g. regions having the protrusions  11114  ( FIG. 77 ). Thus, power can be applied to the heating element  11224  to cause localized heating near the higher resistance portions  11218 . In this way, the heat is applied selectively to the polymer layer and to the adjunct material coupled thereto. 
     In some embodiments the heating element  11224  can include a switch  11230  configured to close the circuit and to allow current to flow through the heating element. The switch  11230  can be operated using a suitable trigger associated with the adjunct loading member  11200  (e.g., a button or other switch on the loader  11200  activated by closure of the end effector or by the person loading the device or a remote control), though the heating element  11224  can be activated in other suitable ways. The heat generated by the higher resistance portions  11218  causes the adhesive portions of the polymer layer, such as the protrusions, to transition to the flowable state and thus couple the polymer layer and the adjunct coupled thereto to the jaw when the polymer layer and adjunct are transferred to the jaw. 
     The heating component  11208  can be of any suitable type. For example, the heating component  11208  can be made of a rigid material, e.g., ceramic, that is coated with an elastic or compliant material. In some embodiments, the heating component  11208  can be in the form of a resistive wire embedded into silicone, e.g., such that the silicone is cured around the resistive wire. The resistive wire is configured to effect the heating, whereas the silicone allows for some degree of compliance when clamping a stapler onto the loader. The heating component  11208  can be coupled to the housings  11204 ,  11205  in any suitable manner, e.g., via brackets. 
     As mentioned above, the adjunct loading member  11200  is generally be configured such that the adjunct  11206  is releasably retained in association therewith adjunct loading member  11200  using a supporting member  11220 . The supporting member  11220  can be in the form of a surface and/or it can include retaining features that can releasably couple the adjunct  11206  and the polymer layer  11212  to the adjunct loading member  11200 . The adjunct  11206  can be disposed on the heating component  11208 , as shown schematically by way of example only in  FIG. 80 . In this way, once the heating component  11208  is activated, heat is applied to the adjunct  11206  and the polymer layer  11212  that faces the jaw  11202 . 
     In some embodiments, an adjunct loading member, which can be similar to the adjunct loading member  11200  can be configured to releasably retain first and second adjuncts, each configured to be transferred to a respective one of first and second jaws of an end effector. The adjuncts can be secured to both jaws of the end effector simultaneously. A heating component can be configured to apply heat to polymer layer&#39;s protrusions or other adhesive depots associated with the adjuncts to retain the adjuncts on the respective jaws. Furthermore, in some embodiments, the heating component can be in the form of two heating components disposed in the removable loader such that each of the heating components is configured to apply heat to a different adjunct that can be associated therewith (e.g., via the loader or manually). 
     After the adjunct  11206  is coupled to the jaw  11202  and the heat is no longer applied thereto, the adhesive from which the protrusions  11214  are formed can at least partially return to the original state, although not to the original shape. This can occur because the heat source is removed (i.e. the adjunct loading member  11200  is removed, or the power to the heaters is switched off after a set time) and the adhesive is exposed to a room temperature. This can be done while the polymer layer  11212  remains at least partially associated with the adjunct loading member  11200 . Also, the adjunct loading member  11200  can be part of a loading system including other components, and such loading system can be configured to cool the adhesive coupling the polymer layer  11212  to the jaw. For example, a cool air can be applied to the polymer layer  11212  coupled to the adjunct  11206 . In some embodiments, the cooling can be done using a separate component. 
     In some embodiments, a trigger associated with the loader (e.g., a switch) is configured to be activated to turn on the heating components once the end effector is clamped onto the loader. This causes the resistors to be heated which thus cause the polymer layer to be heated. The compression or load from the end effector causes the adhesive to flow and conform to the features on the jaw. The power to the resistors can automatically cease after a preset time (either a timer in the circuit, or the circuit can self-destruct with time/heat, or the battery can expire, etc.). After the heat is no longer applied, the polymer adhesive will cool, e.g., due to the thermal mass of the jaws. The loader, or other suitable component, can be configured to, after a time sufficient for the adhesive to cool and thus transition to an adhered state has passed, provide an indication indicating that the process of adhering the adhesive (and thus coupling the adjunct to the jaw) has been completed. The indication can be provided in any suitable way—for example, it can be a visual (e.g., light) indicator, audio indicator, any combination of a visual/audio indicator, etc. 
     Regardless of the manner in which the adhesive coupling the polymer layer  11212  to the jaw  11202  is cooled, the adhesive at least partially hardens or solidifies. The adjunct  11206  is coupled to the jaw  11202  via the polymer layer  11212  with the protrusions  11214  in a releasable manner and can thus be separated from the jaw  11202 . For example, when staples are fired from the jaw  11202 , the bond between the adhesive and the jaw  11202  can break or crack. 
     The polymer layer  11212  and the protrusions  11214  formed thereon can be made from any suitable material or a combination of materials. Also, they can be bioabsorbable and/or biodegradable. The protrusions  11214  can be formed from a material having a lower melting point than a melting point of a material from which the polymer layer  11212  is made. For example, if the material from which the protrusions  11214  are made is PDO, its melting point can be less than about 105° C. However, materials with a melting point that is less than about 180° C. can be used additionally or alternatively. When heat is applied to the polymer layer  11212  (e.g., selectively, such that portion(s) of the protrusions are exposed to heat), the adhesive of the protrusions  11214  can be transitioned to a flowable state, whereas the state of an adhesive from which the polymer layer  11212  is made does not change. 
     In some embodiments, an adhesive depot having an adhesive configured to transition from a non-flowable state to a flowable state upon the application of heat is in the form of a plurality of reservoirs. The plurality of reservoirs can be formed in a supporting layer of an adjunct loading member and each can releasably hold the adhesive. 
       FIGS. 81A and 81B  illustrate an embodiment of an adjunct loading member  11400  releasably holding first and second adjunct materials  11306 ,  11316  on first and second supporting members  11420 ,  11422 , respectively. The adjunct loading member  11400  is used to transfer the first and second adjunct materials  11306 ,  11316  to first and second jaws  11302 ,  11304  of an end effector  11300 , as discussed below. In this example, the first jaw  11302  has a cartridge (which can be removably and replaceably seated in the jaw or which can be part of a reloadable unit including the first jaw  11302  or both the first and second jaws  11302 ,  11304 ), and the second jaw  11304  has an anvil. 
     In the illustrated embodiment, the adjunct loading member  11400  is in the form of a generally rectangular member having first and second generally rectangular housings  11402 ,  11404  coupled to one another. As shown, the adjunct loading member  11400  includes an adjunct holding member  11406  extending between the housings  11402 ,  11404  and including various components. In particular, the adjunct holding member  11406  includes body members  11416   a ,  11416   b  shown in the left and right sides of the adjunct loading member  11400 , respectively, brackets  11410   a ,  11412   a  at one side of the adjunct loading member  11400  (left in  FIGS. 81A and 81B ), brackets  11410   b ,  11412   b  at another side of the adjunct loading member  11400  (right in  FIGS. 81A and 81B ), and the first and second supporting members  11420 ,  11422  extending between the body members  11416   a ,  11416   b.    
     The supporting members  11420 ,  11422  are disposed in the adjunct loading member  11400  such that their mid-portions having the first and second adjunct materials  11306 ,  11316  releasably retained thereon are not encompassed by the housings  11402 ,  11404 . The brackets  11410   a ,  11410   b  extend over the body members  11416   a ,  11416   b  at one side thereof (bottom in  FIGS. 81A and 81B ) and retain the first adjunct  11306  over the supporting member  11420 . In a similar manner, the brackets  11412   a ,  11412   b  extend over the body members  11416   a ,  11416   b  at another, opposed side thereof (top in  FIGS. 81A and 81B ) and retain the second adjunct  11316  over the supporting member  11422 . 
     As shown, each of the brackets has a straight portion (e.g., a portion  11411  of the bracket  11410   a ) extending along and over one of the body members  11416   a ,  11416   b , and a trapezoid-shaped deformable portion (e.g., a portion  11413  of the bracket  11410   a ) extending from the straight portion towards a center of the adjunct loading member  11400 . One end of each of the trapezoid-shaped deformable portion of the brackets  11410   a ,  11410   b , and  11412   a ,  11412   a  is disposed over the first and second adjunct materials  11306 ,  11316 , respectively. It should be appreciated that the brackets are shown to have the trapezoid-shaped deformable portion by way of example only, as the brackets can have any other configuration. 
     In the illustrated embodiments, the adhesive depots are in the form of reservoirs formed in the supporting members. Thus, as shown in  FIG. 81A , the supporting member  11420  has reservoirs  11424   a ,  11424   b , and the supporting member  11422  has reservoirs  11426   a ,  11426   b . Each of the reservoirs  11424   a ,  11424   b ,  11426   a ,  11426   b  releasably holds an adhesive and includes an opening through which the adhesive can be released from that reservoir. For example, in  FIG. 10 , the reservoir  11426   a  is shown to have an opening  11430   a , and other reservoirs have similar openings. As also shown, each of the adjunct materials  11306 ,  11316  includes a plurality of openings each having a reservoir with adhesive associated therewith. In particular, the adjunct material  11306  has openings  11310   a ,  11310   b  disposed adjacent to the openings in the reservoirs  11424   a ,  11424   b . Similarly, the adjunct material  11316  has openings  11312   a ,  11312   b  disposed adjacent to the openings in the reservoirs  11426   a ,  11426   b . It should be appreciated, however, that in some embodiments, the reservoirs can be configured differently—e.g., they may not have openings, but can have a breakable, meltable, or otherwise removable enclosure that allows to retain the adhesive in the reservoirs and that can be removed when it is desired to release the adhesive. Additionally or alternatively, openings configured to allow an adhesive to flow from the reservoir can be formed in the supporting member. 
     The openings, such as the openings  11310   a ,  11310   b  in the adjunct material  11306  and the openings  11312   a ,  11312   b  in the adjunct material  11316 , are formed at locations in the adjuncts at which it is desired to form attachment portions or points (made of an adhesive) that couple the adjuncts to the jaw. The opening locations in each of the adjuncts can be selected so as to facilitate attachment of the adjunct to the jaw and to also facilitate release of the adjunct from the jaw. It should be appreciated that the adjuncts  11306 ,  11316 , which are shown in  FIGS. 81A and 81B  in cross-section, can include more than two openings. Multiple openings can be formed so as to attach the adjunct to the jaw using an adhesive at more than two locations. For example, four, six, eight, or more openings can be formed in each of the adjuncts. Also, although, as in the example in  FIGS. 81A and 81B , the openings can be formed in pairs (e.g., they can be disposed symmetrically along a centerline of the adjunct), an odd number (e.g., three, five, etc.) of openings can be formed, which corresponds to an odd number of attachment points to be formed when the adjunct is coupled to the jaw. 
     The adjunct loading member  11400  has first and second heating components  11408 ,  11418  extending through the supporting members  11420 ,  11422  that are configured to apply heat to the adhesive held in the reservoirs  11424   a ,  11424   b  and  11426   a ,  11426   b , respectively, to cause the adhesive to transition from a non-flowable state to a flowable state. In some implementations, a single heating component can be used. Also, the first and second heating components  11408 ,  11418  can be parts of the same heating component. The openings  11310   a ,  11310   b ,  11312   a ,  11312   b  are configured to receive the adhesive transitioning to the flowable state when the adhesive material is released from a respective one of the reservoirs and through the opening to a jaw-facing surface of the respective adjunct material to thereby retain that adjunct material on the jaw. 
     In use, the adjunct loading member  11400  having the adjunct materials  11306 ,  11316  releasably retained thereon is disposed between the first and second jaws  11302 ,  11304  of the end effector  11300 , as shown in  FIG. 81A  that illustrates the adjunct loading member  11400  before a load is applied thereto. The load is then applied to the adjunct loading member  11400  by the first and second jaws  11302 ,  11304  that clamp the adjunct loading member  11400  therebetween, as shown in  FIG. 81B . Under the application of load exerted by the jaws, the adjunct loading member  11400  is at least partially deformed, which causes the adjunct materials  11306 ,  11316  to be transferred to the jaws  11306 ,  11316 , respectively. For example, the brackets  11410   a ,  11410   b , and the brackets  11412   a ,  11412   a  can be at least partially deformed. Also, the supporting members  11420 ,  11422 , which can be formed from a silicone or other deformable and resilient material(s), are deformed under the load, as shown in  FIG. 81B . When load is applied to the adjunct loading member  11400 , the supporting members  11420 ,  11422  apply pressure to the adjunct materials  11306 ,  11316 , which can be done in the manner that facilitates uniform application of the load to the adjunct materials. This helps apply the adjunct to the jaws in a uniform manner. 
     In the illustrated example, the adjunct loading member  11400  is configured so that the adjunct materials  11306 ,  11316  are transferred substantially simultaneously to the jaws  11306 ,  11316 . It should be appreciated, however, that in some embodiments the adjunct loading member can be configured to transfer one adjunct to an end effector&#39;s jaw. 
     Before or at the time when the load is applied to the adjunct loading member  11400 , the heating components  11408 ,  11418  are activated to cause heat to be applied to the reservoirs  11424   a ,  11424   b  and  11426   a ,  11426   b , respectively, to cause the adhesive in the reservoirs to transition from the non-flowable state to the flowable state. The adhesive can be stored in the reservoirs  11424   a ,  11424   b ,  11426   a ,  11426   b  in a substantially non-liquid state, and, under the application of heat, the adhesive can become at least partially liquid such that it can be used to couple the adjunct materials to the jaws. As shown in  FIG. 81B , when the load is applied, the adhesive is released from the reservoirs, through the openings in the adjuncts  11306 ,  11316 , and onto the surface of the jaws  11302 ,  11304 . In this way, the portions of adhesive  11427   a ,  11427   b  and  11429   a ,  11429   b  released from the reservoirs  11424   a ,  11424   b  and  11426   a ,  11426   b , respectively, are used to retain the adjunct materials on the opposed jaws of the end effector  11300 . 
     The reservoirs  11424   a ,  11424   b ,  11426   a ,  11426   b  can have any suitable configurations and they can be configured to release the adhesive stored therein in various ways. In the illustrated example, they are at least partially enclosed structures that store the adhesive. For example, they can be formed from a rigid plastic having a liquid adhesive (e.g., a pressure-sensitive adhesive) stored therein. As mentioned above, the reservoirs can have openings formed on the side thereof adjacent to the adjunct. 
     Furthermore, in some embodiments, the adjunct loading member  11400  can include a closure component that can be disposed so as to temporarily enclose one side of the reservoirs and thereby retain the adhesive therein. With reference to  FIG. 81A , such a closure component can be disposed between each of the supporting layers and a respective adjunct material. The closure (or a cap) can be a removable component that is removed to allow the adhesive to flow from the reservoirs. As another variation, the closure component can be in a form of component that can be disposed in at least two different ways with respect to the reservoirs. In particular, the closure component can have openings that can align with the openings in the reservoirs. However, before the adhesive is released from the reservoirs, the closure component can be disposed such that the openings therein are not aligned with the openings in the reservoirs and the closure is thus blocking the openings in the reservoirs and prevents release of the adhesive therefrom. The closure component can be, for example, slidable such that it can be moved to configuration in which its openings are aligned with the openings in the reservoirs. In some embodiments, the closure component can be in the form of a membrane or other thin member configured to rupture when pressure applied thereto exceeds a threshold. 
     The adjunct loading member  11400  is configured such that it can be separated from the end effector  11300  after the adjuncts  11306 ,  11316  are transferred to the jaws  11302 ,  11304  and are retained on the jaws using the adhesive. The adhesive can solidify and thus securely retain each adjunct on the jaw. In some embodiments, as discussed above, the adhesive can be allowed to solidify at a room temperature. Additionally or alternatively, it can be actively cooled using, e.g., a forced cool air. 
     The adhesive releasably retained in the reservoirs can be any suitable material. For example, it can be a flowable material such as polydioxanone (PDO), a high molecular weight poly(ethylene glycol) (PEG), or any other material. As mentioned above, the adhesive can be a pressure-sensitive adhesive. 
     Although in the illustrated embodiments heat is applied to an adhesive using an adjunct loading member, it should be appreciated that the heat can be applied in other manners. For example, in some implementations, an end effector can be configured to apply heat to the adhesive which can be releasably held in any type of an adhesive depot (e.g., a polymer layer having adhesive features, reservoirs in an adjunct loading member, etc.). The end effector can include a wire or other component that can be heated and can thus apply heat to the adhesive which thereby softens and can retain an adjunct on a jaw. In some embodiments, a separate heating component can be applied, which is not part of an end effector. 
     At least one adjunct can be applied to one or both jaws of the end effector during assembly of the end effector. For example, a jaw having a cartridge or both of the end effector&#39;s jaws can be pre-loaded with an adjunct during the assembly. In some cases, the jaw with the cartridge can be pre-loaded with an adjunct during the assembly, whereas an adjunct can be applied to the jaw having an anvil (e.g., using any of the adjunct loading members described herein) by a surgeon before or during a surgical procedure. Alternatively, as in the embodiments illustrated in  FIGS. 81A and 81B , adjuncts can be applied to both jaws of the end effector by a surgeon (this however can be done during assembly as well). 
     A configuration of an adjunct loading member can vary in different ways.  FIG. 82  illustrates an example of an adjunct loading member  11500  which can be similar to adjunct loading member  11400  in  FIGS. 81A and 81B . Thus, as shown in  FIG. 82 , the adjunct loading member  11500  includes housings  11502 ,  11504  coupled to one another. The adjunct loading member  11500  also includes supporting members  11520 ,  11522  disposed in the loading member  11500  such that the housing  11502 ,  11504  enclose the supporting members  11520 ,  11522  along their perimeters. One side of the supporting members  11520 ,  11522  is not enclosed, as shown. 
     The supporting members  11520 ,  11522  have reservoirs releasably holding an adhesive, with one of the reservoirs, a reservoir  11524   a , shown formed in the supporting layer  11520 . A top of another reservoir  11524   b  is also shown formed in the supporting member  11520 . One or both of the reservoirs and supporting members in which the reservoirs are formed can have openings that allow the adhesive stored in the reservoirs to be released therefrom. Thus, the reservoir  11524   b  is shown to have an opening  11530  above it, which can be formed in either the reservoir  11524   b  itself or in the supporting member  11520 . Also, as discussed above, a closure component can be used (not shown), and an opening can be formed in this component as well. 
       FIG. 82  shows that the adjunct loading member  11500  releasably retains therein an adjunct material  11506 , which is shown partially for illustration purposes. The adjunct material  11506  includes openings  11510  that are configured to receive the adhesive transitioning to the flowable state when the adhesive is released from a respective one of the reservoirs and through the opening to a jaw-facing surface of the respective adjunct material to thereby retain that adjunct material on the jaw. The adjunct material  11506  is releasably retained on the supporting member  11520 . It should be appreciated that, although it is obscured in  FIG. 82 , the loading member  11500  can include a second adjunct material releasably retained on the supporting member  11522 . 
     The adjunct material  11306  is releasably retained in the adjunct loading member  11500  using retainer elements  11512 , which can have any suitable configurations. Although the retainer elements  11512  on one side of the adjunct material  11306  are shown, it should be appreciated that they can also be formed on the opposed side of the adjunct material  11306 , in which case they are obscured in  FIG. 82 . Also, the retainer elements  11512  can be configured such that they can be movable—e.g., when load is applied to the adjunct loading member  11500 , the retainer elements can be caused to move towards the edges of the housings  11502 ,  11504 , such that the retainer elements release the adjunct material  11306 . 
     As shown in  FIG. 82 , a heating component  11508  coupled to a power source  11516  is disposed between the supporting members  11520 ,  11522 . The heating component  11508 , e.g., its higher resistance portions  11532  are used to apply heat to respective reservoirs to cause the adhesive stored in the reservoirs to transition from a non-flowable state to a flowable state. 
     Similar to the adjunct loading member  11400  in  FIGS. 81A and 81B , the adjunct loading member  11500  is configured to have load applied thereto to cause it to release one or more adjunct materials therefrom which are transferred to jaw(s) of an end effector and are coupled to the jaw(s) using the adhesive. 
     In some embodiments, an adhesive depot can include an adhesive that is substantially liquid in a non-cured state and that is configured to be transitioned to an adhering, cured state in which it is at least partially non-liquid. This can involve curing the adhesive, which can be done using application of ultra violet (UV) light or infrared radiation. Additionally, load (or pressure) applied to the adhesive can facilitate curing the adhesive in some instances. In the cured, at least partially non-liquid state, the adhesive is used to couple an adjunct to a jaw of an end effector. 
       FIGS. 83A-83C  illustrate an example of a portion of an adjunct loading member  11600  including a supporting member  11620  releasably retaining an adjunct material  11606 . The supporting member  11620 , which can be at least partially made from a silicone or other compressible material, includes one or more reservoirs holding an adhesive, one of which is shown as a reservoir  11614  storing an adhesive  11616 . As shown in  FIG. 83A , the reservoir  11614  is disposed adjacent to an opening  11610  in the adjunct material  11606 . The reservoir  11614  can be an enclosed structure (e.g., formed from a suitable plastic) releasably holding the liquid adhesive  11616 . The adhesive  11616  can be any suitable UV-curable adhesive, such as, for example, polyurethane, cyanoacrylate, or any other adhesive(s). 
     The adjunct material  11606  is configured to be transferred to a jaw  11602  of an end effector which is, in this example, a jaw having an anvil. The anvil  11602  can have a tissue-facing surface  11605  having staple-forming cavities or pockets  11607 . Also, as shown in  FIGS. 83A-83C , the tissue-facing surface  11605  has attachment portions, one of which is shown as an attachment portion  11612  that is configured to receive the adhesive released from the reservoir  11614 . The attachment portions can be formed between the staple-forming pockets  11607 , though they can be formed in other areas of the tissue-facing surface  11605 . In some embodiments, as shown in this example, the attachment portion  11612  can include an attachment feature  11613  made from an elastomeric material (e.g., a pad) that is coupled to the tissue-facing surface  11605 . This feature can be patterned (e.g., knurled or otherwise roughened), which facilitates adherence of the adhesive to this portion. Also, the elastomeric material allows the attachment feature  11613  to be deformed when the bond between the attachment portion  11612  on the surface  11605  and the adhesive coupled thereto (which retains an adjunct over the surface  11605 ) is broken, as discussed in more detail in the example shown in  FIGS. 86A-86C  below. 
     As shown, the adjunct loading member  11600  also includes UV light applicators  11603  configured to apply UV light to the adhesive as it is released from the adhesive reservoirs. The UV light applicators  11603  are coupled to a cable  11611  (e.g., a fiber optic cable) that couples the applicators to a UV light source. Also, in some embodiments, the UV light applicators  11603  can be associated with UV-emitting light emitting diodes (LEDs). 
       FIG. 83A  illustrates the adjunct loading member  11600  before load is applied thereto. When the load so applied to the adjunct loading member  11600  (e.g., using the jaws of the end effector, manually, etc.), the reservoir  11614  is deformed, broken, or its configuration is otherwise changed such that the adhesive  11616  is transferred from the reservoir  11614 , through the opening  11610  in the adjunct  11606 , and onto the surface of the jaw  11302 , as shown in  FIG. 83B . The adhesive  11616  is transferred to the tissue-facing surface  11605  of the jaw  11302  so as to be disposed on the surface of the attachment portion  11612 . As the adhesive  11616  is being released, the UV light applicators  11603  are activated to apply UV light to the adhesive  11616  to cause it to cure, as illustrated in  FIG. 83C . In this way, the adhesive  11616  is deposited on the surface of the jaw in the adhering, non-cured state (or only partially cured) in which it is then cured and thus attaches the adjunct  11606  to the jaw  11602 . The adjunct loading member  11600  can then be separated from the end effector. 
     It should be appreciated that the portion of the adjunct loading member  11600  is shown in  FIGS. 83A-83C  by way of example only. Also, the adjunct loading member  11600  can include multiple reservoirs with the adhesive, more than one openings can be formed in the adjunct, as well as other variations are possible. 
       FIGS. 84A and 84B  illustrate another example of an adjunct loading member  11700  configured to releasably hold first and second adjunct materials  11806 ,  11816  and to apply these adjunct materials to first and second jaws  11802 ,  11804  of an end effector  11800 . Similar to adjunct loading member  11600  in  FIGS. 83A-83C , a substantially liquid adhesive released from the adjunct loading member  11700  is configured to be cured using UV light, heat, or in other manner. As shown in  FIGS. 84A and 84B , the adjunct loading member  11700  is similar to adjunct loading member  11400  shown in  FIGS. 81A and 81B , and therefore a detailed description is not repeated. However, as mentioned above, the adjunct loading member  11700 , releasably stores in reservoirs formed in first and second supporting members  11720 ,  11722  an adhesive that is cured upon it is release from the reservoirs such that it is used to retain the adjuncts on the jaw in its cured state. 
     Describing by way of example one of the reservoirs included in the adjunct loading member  11700 , a reservoir  11824  in the supporting member  11720  is configured to provide an adhesive  11827  stored therein when load is applied to the adjunct loading member  11700  as shown in  FIG. 84B . A UV light applicator  11808  or other (e.g., infrared radiation) applicator is configured to apply UV or other radiation to the adhesive  11827  as it is released from the reservoir  11824 . In this way, the adhesive is used to retain the adjunct on the jaw as the adjunct is transferred to the jaw. 
     Any suitable component can be used to apply radiation to an adhesive to cause it to transition from a state in which it is not cured to an adhering state in which it is cured.  FIG. 85  illustrates one embodiment of an adjunct loading member  11900  that can be used to apply radiation to an adjunct material  11906 . The adjunct loading member  11900  can be generally similar to adjunct loading member  11500  in  FIG. 82  and is therefore not described in detail. In this example, an adhesive stored in a reservoir, such as a reservoir  11924  formed in a supporting member  11920  is configured to be cured when it is released from the reservoir  11924  when load is applied to the adjunct loading member  11900  and the adhesive is cured using radiation emitted from a UV applicator  11908 . Other types of radiation, however, can be used additionally or alternatively. Similar to the manner described above in connection with the adjunct loading member  11500  ( FIG. 82 ), the adhesive can be released from the reservoir and caused to flow through an adjacent opening  11510  formed in the adjunct  11906 . Although not shown in  FIG. 85 , the adjunct loading member  11900  can also have a second adjunct material releasably retained therein and configured to be transferred therefrom and attached to a second jaw of an end effector similar to the adjunct  11906 . 
     Regardless of the specific way in which an adjunct material is coupled to a jaw of an end effector, it is required to properly separate the adjunct material from the jaw when the adjunct is applied to tissue. It is desired to release the adjunct from the jaw in an efficient manner. This can be achieved, for example, by fracturing the adhesive that attaches the adjunct to the end effector.  FIG. 86A  illustrates an example of a portion of an adjunct material  111506  attached to the jaw  111504  of an end effector  111500  by an adhesive  111514 , which can be cured in a desirable manner (e.g., using a UV light applied via a loader, or in other manners). The adhesive  111514  releasably attaches the adjunct material  111506  to the jaw  111504  by being at least partially disposed in an opening  111510  formed in the adjunct material  111506 . 
     Similar to adhesive  11616  in  FIGS. 83A-83C , the adhesive  111514  in  FIG. 86A  is coupled to the jaw  111504  at an attachment region or portion  111512  on the surface of the jaw  111504 . Similar to attachment portion  11612  in  FIGS. 83A-83C , the attachment portion  111512  can have a deformable attachment feature  111513  that is patterned to facilitate coupling the adhesive thereto. The attachment feature  111513  can be formed from an elastomeric material such that it can deform when a force is applied thereto. 
     The end effector  111500  can be configured to cause the adjunct material  111506  to separate from the jaw  111504  when staples are fired from a jaw  111502  having a cartridge that is shown schematically in  FIG. 86B . For example, as shown, the jaws  111502 ,  111504  are approximated to clamp tissue  111520  therebetween and a stapler driver  111530  movably seated in the jaw  111502  causes staples  111522  to fire from staple holding cavities in the jaw  111502  so as to penetrate the tissue  111520  and the adjunct  111506 . The staples  111522  are urged into corresponding staple-forming cavities or pockets  111507  formed on the surface of the jaw  111504  such that the staples  111522  are closed and attach the adjunct  111506  to the tissue  111520 . 
     In the example illustrated, the stapler driver  111530  includes protruding members  111518  configured to push the cured adhesive  111514  towards the attachment portion  111512  and into the attachment feature  111513  (which can deform to some degree) when the staples  111522  are fired. This can cause the adhesive  111514  to break, fracture, deform, or otherwise change its configuration. In some instances the cured adhesive  111514  can be brittle and applying load thereto causes it to fracture, crack, or break. 
     It should be appreciated that only portions of the adjunct  111506  and the end effector  111500  are shown in  FIGS. 86A-86C  and that multiple attachment portions similar to the attachment portion  111512  (or having other configurations) can be formed on the jaw  111504  and are used to couple the adjunct  111506  to the jaw  111504  using the adhesive  111514 . Accordingly, multiple corresponding protruding members on the stapler driver  111530  can cause the adhesive at the corresponding attachment portions to break. In this way, the adjunct  111502  can be decoupled from the attachment region  111512  and thereby be released from the jaw  111504 . Thus,  FIG. 86C  illustrates the tissue  111520  and the adjunct  111506  stapled together by the staples  111522  and decoupled from the jaw  111504  and thus from the end effector  111500 . A portion of the adhesive  111514 , which can be a biodegradable and/or bioabsorbable material, can remain with the adjunct  111506 , as shown. 
     It should be appreciated that the described adjunct materials and systems and methods used to apply the adjunct materials to at least one jaw of an end effector can have various configurations. For example, although, as discussed above, the adjunct materials can have openings formed therein that allow an adhesive from an adhesive despot to be applied to the surface of the adjunct, in some embodiments, the openings may not be formed. In such embodiments, the adhesive can be flowed from an adhesive depot (e.g., one or more reservoirs) through pores, spaces between fabric strands, or other structures in the adjunct material. For example, the adjunct material can be porous and the adhesive are flow therethrough to a surface of the jaw. The pores can be formed at any suitable ways, and, in some instances, they can be larger at predetermined locations through which the adhesive can flow easier. 
     Adjunct Loader for Surgical Staplers 
     Various adjunct loaders are provided for cleaning and affixing an adjunct to an end effector of a surgical stapling device. While the adjunct loaders are described in connection with end effectors of surgical staplers, the adjunct loaders can be used in connection with any type of surgical device. In an exemplary embodiment, an adjunct loader can be configured to clean at least one tissue-engaging surface of an end effector on a surgical stapler, and the adjunct loader can be configured to attach an adjunct to the tissue-engaging surface of the end effector. For example, an adjunct loader can have two slots, each configured to seat at least one jaw of the end effector therein. One slot can be configured to clean the end effector, and the other slot can be configured to attach the adjunct to the end effector. The adjunct loader can thus allow a user to rapidly clean and attach an adjunct to a surgical stapler for use during an operation, increasing the speed and convenience of using adjuncts with a surgical stapler. 
     Cleaning the end effector and attaching the adjunct can be achieved through a variety of techniques.  FIGS. 87-89  illustrate one embodiment of an adjunct loader  12100 . The illustrated adjunct loader  12100  has a frame  12102 , a cleaning slot  12104 , and a loading slot  12106 . The frame  12102  can have any shape, such as a rectangular housing with a top portion  12110  and a bottom portion  12112 . The top portion  12110  and the bottom portion  12112  can snap or clip together using, for example, posts  12114  that extend from one of the top or bottom portions  12110 ,  12112  and snap into the other of the top or bottom portions  12110 ,  12112 . In other embodiments, the two portions can be closed together in any number of ways, such as being glued, sealed, or formed as a single unit. 
     The frame  12102  can have the cleaning slot  12104  and the loading slot  12106  formed therein. The cleaning slot  12104  and the loading slot  12106  can be configured to receive at least a portion of an end effector on a surgical stapler. For example, the slots  12104 ,  12106  can take the form of longitudinal openings formed in the frame  12102  and can be sized and shaped to receive a linear end effector therein, such as the elongate jaws of the surgical staplers  10 ,  50 . The slots  12104 ,  12106  can extend parallel to each other and can have open ends  12104   a ,  12106   a  on one side of the frame  12102  and closed ends  12104   b ,  12106   b  on an opposite side of the frame  12102 . The closed ends  12104   b ,  12106   b  can have a semicircular shape, but a variety of different configurations are possible. The top portion  12110  and the bottom portion  12112  of the frame  12102  can have ledges  12110   a ,  12112   a  formed along the slots  12104 ,  12106  and configured to create a groove that extends along a perimeter of at least the longitudinal edges of the slots  12104 ,  12106  when the top portion  12110  and the bottom portion  12112  are snapped together, as illustrated in  FIG. 89 . 
     Each slot  12104 ,  12106  can be configured to retain a material therein, such as a cleaning material or an adjunct. In the illustrated embodiment, each of the top portion  12110  and the bottom portion  12112  of the frame  12102  can have a plurality of fingers  12116  that extend into the slots  12104 ,  12106 . The fingers  12116  can have a variety of shapes, such as a wedge shape with a triangular cross-section as illustrated in  FIG. 87 , and can be configured to retain material between the top portion  12110  and the bottom portion  12112  within the slots  12104 ,  12106 . In the cleaning slot  12104 , the fingers  12116  can be fixed and configured to remain in place even under a pulling or tugging force. In the loading slot  12106 , the fingers can be deflectable and/or spring biased to release material held therebetween under a pulling or tugging force. For example, the fingers  12116  in the loading slot  12106  can be configured to be retractable into the frame  12102  when jaws of an end effector clamp onto an adjunct therebetween. In some embodiments, the jaws can push the fingers  12116  into the frame  12102  when engaging the adjunct thereby disengaging the fingers from the adjunct and releasing the adjunct from the loader  12100 . 
     The cleaning slot  12104  can have a cleaning pad  12120  that extends between the open end  12104   a  and the closed end  12104   b  of the cleaning slot  12104 . The cleaning pad  12120  can have a variety of shapes, such as a rectangular shape. In an exemplary embodiment, the shape corresponds to the shape of an end effector to be cleaned, such as elongate jaws of a linear surgical stapler. The cleaning pad  12120  can have a tongue  12122  that extends from one end of the cleaning pad  12120  and into the open end  12104   a  of the cleaning slot  12104 . The cleaning pad  12120  can extend the length between the two ends or can extend some distance less than entirely between the two ends, for example as illustrated in  FIG. 88  in which the cleaning pad  12120  terminates before reaching the closed end  12104   b . The cleaning pad  12120  can extend into the groove formed by the ledges  12110   a ,  12112   a  and can be held between the top portion  12110  and the bottom portion  12112  of the frame  12102  by the plurality of fingers  12116 . In some embodiments, the fingers can be configured to hold an adjunct in the loading slot  12106  (discussed in more detail below) while the cleaning pad  12120  can be configured to be secured to the frame  12102  through various other techniques. For example, the cleaning pad  12120  can be configured to be secured with holes in the pad  12120  that extend over pins in the frame  12102 . Other examples can include securing the cleaning pad  12120  by the pad  12120  being glued in place, welded in place, held in place by other posts from the housing  12102  that are formed into mushrooms with heated tooling, etc. 
     The cleaning pad  12120  can have a variety of configurations. For example, the cleaning pad  12120  can be made from an abrasive material with a cleaning solvent saturated therein and configured to remove a variety of substances, such as adhesive, tissue, and/or oily residue. The cleaning pad  12120  can be configured to remove any build-up and/or adhesive left on jaws (particularly an anvil) on an end effector left over from any previous firings with an adjunct. This cleaning can be beneficial to prevent any adhesive build up on the device, which can cause a variety of problems such as causing staples to be malformed, causing over-compression of tissue, etc. In various embodiments, a solution that aids in adhesion can also be added to the cleaning pad  12120 . The cleaning pad  12120  can be configured to be engaged by opposed jaws on an end effector of a surgical stapler, and it can be configured to clean one side of the surgical stapler, such as the anvil side or to clean both sides as may be needed. In certain embodiments, the cleaning pad  12120  can have various configurations, such as different sides of the pad with a cleaning side and a neutral side, different layers of the pad with a cleaning layer and a neutral layer, a cover or film on one side to prevent cleaning, etc. 
     The loading slot  12106  can have an adjunct  12130 , such as any of the buttresses, adjuncts, and/or medicants discussed above, Vicryl matrix, etc., disposed therein. The adjunct  12130  can have a variety of shapes, such as a rectangular shape. In an exemplary embodiment, the shape corresponds to the shape of an end effector to be cleaned, such as elongate jaws of a linear surgical stapler. The adjunct  12130  can have a tongue  12132  that extends from one end of the adjunct  12130  and into the open end  12106   a  of the loading slot  12106 . The adjunct  12130  can extend entirely between the open end  12106   a  and the closed end  12106   b  of the loading slot  12106 , or it can extend some distance less than entirely between the two ends, for example as illustrated in  FIG. 88  in which the adjunct  12130  terminates before reaching the closed end  12106   b . The adjunct  12130  can be held between the top portion  12110  and the bottom portion  12112  of the frame  12102  and can be held in place by the plurality of fingers  12116  in the groove formed by the ledges  12110   a ,  12112   a . The adjunct  12130  can be configured to be released by the fingers  12116  upon application of a threshold force on the adjunct  12130  such that the adjunct  12130  will be free from the adjunct loader  12100 . For example, the fingers  12116  can defect out of the slot as the adjunct  12130  is engaged by jaws of an end effector to thereby release the adjunct  12130 . 
     The adjunct  12130  can have a variety of configurations, as discussed above, and can have a variety of attachment mechanisms thereon, such as an adhesive coated on a surface of the adjunct  12130 . A variety of adhesives can be used, such as 50-50 PCL-PGA, other absorbable polymers such as mixes of poloxamers, natural substances such as bees wax, etc. The adhesive can be spread on one or both surfaces of the adjunct  12130 . For example, the adjunct  12130  can have an adhesive spread on upper surface  12130   a  of the adjunct  12130  that is configured to contact a tissue-facing surface of a surgical stapler. A cover  12134  can be disposed in the loading slot  12106  with the adjunct  12130 . The cover  12134  can have a variety of configurations, such as a rectangular-shaped thin sheet of material that extends between the open end  12106   a  and the closed end  12106   b  of the loading slot  12106  with the adjunct  12130 . The cover  12134  can be held between the top portion  12110  and the bottom portion  12112  of the frame  12102  with the adjunct  12130  and can cover the adhesive surface  12130   a  of the adjunct  12130 . The cover can be made from a variety of materials. For example, the cover can be a compliant but non-porous material, various plastics, etc. The cover  12134  can be configured to be manually removed, although a variety of different retraction options are possible. For example, the cover can be configured to automatically snap open upon use of the cleaning slot  12106 , be rolled up inside the adjunct loader  12100  by, for instance, having a pressure-sensitive rolling mechanism in the adjunct loader  12100  that is configured to sense clamping on the cleaning pad  12120  and then trigger rolling or retraction of the cover from the adjunct  12130 , etc. 
     In use, the jaws of a surgical stapler can first be clamped onto the cleaning pad  12120  in the cleaning slot  12104 . With the end effector engaging the cleaning pad  12120 , the jaws of the surgical stapler can be pulled out of the slot  12104 . Because the surgical stapler is still clamped on the cleaning pad  12120  as it is retracted, the cleaning pad  12120  can scrub and clean the tissue facing surface of the anvil and/or the cartridge. In some embodiments, the cleaning pad  12120  can be used to clean just the anvil side of a surgical stapler without cleaning the cartridge side, by using the various approaches discussed above. As the surgical stapler is retracted out of the slot  12104 , the fingers  12116  or other retention mechanisms can retain the cleaning pad  12120  in the cleaning slot  12104 . A user can remove the cover  12134  from the loading slot  12106  or it can be automatically removed upon cleaning, exposing the adhesive side  12130   a  of the adjunct. The user can clamp the surgical stapler onto the adjunct  12130  in the loading slot  12106  with one of the anvil or the cartridge of the surgical stapler contacting the adhesive side  12130   a . The adjunct  12130  will attach to the tissue facing surface adjacent the adhesive, and the jaws can be retracted from the slot  12106  after unclamping the jaws. Because the adjunct  12130  is attached to the surgical stapler, the adjunct will be released from the adjunct loader  12130  upon application of a threshold force, for example by having the fingers  12116  release the adjunct  12130  under application of force or by withdrawing the adjunct  12130  distally through the open end  12106   a  of the loading slot  12106 . The adjunct  12130  is ready for delivery to tissue. Provided above is an embodiment of a single-step, two-stage adjunct loader. Two step loaders are also possible, in which a user clamps a surgical stapler onto a first loader that only cleans the surgical stapler before clamping the surgical stapler onto a second, separate loader with an adjunct that loads the adjunct onto the surgical stapler (similar to the loading process described above). 
     The adjunct loader  12100  illustrates an adjunct  12130  designed to be attached to only one side of a surgical stapler, but a variety of other configurations are possible. For example,  FIGS. 90-92  illustrate an adjunct loader  12200  that is similar to the adjunct loader  12100  discussed above. The adjunct loader  12200  can have a frame  12202 , a cleaning slot  12204 , and a loading slot  12206 . The frame  12202  can have an approximate M shape with a top portion  12210  and a bottom portion  12212 . The top portion  12210  and the bottom portion  12212  can snap or clip together using, for example, posts  12214  that extend from one of the top or bottom portions  12210 ,  12212  and snap into the other of the top or bottom portions  12210 ,  12212 . The frame  12202  can have the cleaning slot  12204  and the loading slot  12206  formed therein. The slots  12204 ,  12206  can take the form of longitudinal openings formed in the frame  12202  and can be sized and shaped to receive a linear end effector of a surgical stapler therein, such as the staplers  10 ,  50 . The slots  12204 ,  12206  can extend parallel to each other and can have open ends  12204   a ,  12206   a  on one side of the frame  12202  and closed ends  12204   b ,  12206   b  on an opposite side of the frame  12202 . The top portion  12210  and the bottom portion  12212  of the frame  12202  can have ledges  12210   a ,  12212   a  formed along the slots  12204 ,  12206  and configured to create a groove that extends along at least the longitudinal edges of the slots  12204 ,  12206  when the top portion  12210  and the bottom portion  12212  are snapped together. Each of the top portion  12210  and the bottom portion  12212  of the frame  12202  can have a plurality of fingers  12216  that extend into the slots  12204 ,  12206 . The fingers  12216  can be configured to retain material between the top portion  12210  and the bottom portion  12212  within the slots  12204 ,  12206 , as described above. 
     The cleaning slot  12204  can have a cleaning pad  12220 , similar to cleaning pad  12120 , that extends between the open end  12204   a  and the closed end  12204   b  of the cleaning slot  12204 . The cleaning pad  12220  can have a rectangular shape and a tongue  12222  that extends from one end of the cleaning pad  12220  and into the open end  12204   a  of the cleaning slot  12204 . The cleaning pad  12220  can be held between the top portion  12210  and the bottom portion  12212  of the frame  12202  by the plurality of fingers  12216  and/or other means described above and the groove formed by the ledges  12210   a ,  12212   a . The cleaning pad  12220  can be made from an abrasive material with a cleaning solvent saturated therein and configured to remove adhesive from previous firings, tissue, oily residue, etc. The cleaning pad  12220  can be configured to have an end effector of a surgical stapler closed thereon and can be configured to clean both sides of the surgical stapler. 
     The loading slot  12206  can have a first and second adjunct  12230 ,  12232  similar to the adjunct  12130  discussed above. The first adjunct  12230  can be placed on top of the second adjunct  12232  in the loading slot  12206 . The adjuncts  12230 ,  12232  can have rectangular shapes, and each adjunct  12230 ,  12232  can have a tongue  12234 ,  12236  that extends from one end of the adjunct  12230 ,  12232  adjacent the open end  12206   a  of the loading slot  12206 . The adjuncts  12230 ,  12232  can extend between the open end  12206   a  and the closed end  12206   b  of the loading slot  12206 . The adjuncts  12230 ,  12232  can be held between the top portion  12210  and the bottom portion  12212  of the frame  12202  by the plurality of fingers  12216  and the groove formed by the ledges  12210   a ,  12212   a . In other embodiments, the adjunct can be configured to be secured to the loading slot in a variety of different ways. For example, these could include less adhesive or less-aggressive adhesive than on the device-contacting side of the adjunct, breakaway features that pull through holes in the adjunct, etc. The adjuncts  12230 ,  12232  can be configured to be released by the fingers  12216  upon application of a threshold force such that the adjuncts  12230 ,  12232  will be free from the adjunct loader  12200 . The adjuncts  12230 ,  12232  can have a variety of configurations, as discussed above, and can have a variety of attachment mechanisms thereon, such as an adhesive. The adhesive can be spread on an outward-facing surface  12230   a ,  12232   a  of each of the adjuncts  12230 ,  12232  so that each of the surfaces  12230   a ,  12232   a  are configured to attach to a tissue-facing surface of a surgical stapler. For example, the surface  12230   a  of the first adjunct  12230  can be configured to adhere to an anvil of a surgical stapler, while the surface  12232   a  of the second adjunct  12232  can be configured to adhere to a cartridge of the same surgical stapler. A first cover  12240  can be disposed in the loading slot  12206  in contact with the first adjunct  12230 . The first cover  12240  can be held between the top portion  12210  and the bottom portion  12212  of the frame  12202  and can cover the adhesive surface  12230   a  of the first adjunct  12230 . A second cover  12242  can be disposed in the loading slot  12206  in contact with the second adjunct  12232 . The second cover  12242  can be held between the top portion  12210  and the bottom portion  12212  of the frame  12202  and can cover the adhesive surface  12232   a  of the second adjunct  12232 . The covers  12240 ,  12242  can be made from a variety of materials, such as compliant but non-porous materials, various plastics, etc. The covers  12240 ,  12242  can be configured to be manually removed, although a variety of different retraction options are possible, as discussed above. 
     In use, an end effector of a surgical stapler can first be clamped onto the cleaning pad  12220  in the cleaning slot  12204 . While the jaws are clamped, the surgical stapler can be pulled away from the adjunct loader  12200 . The cleaning pad  12220  can scrub and clean the tissue-facing surface of each jaw as it is removed. As the surgical stapler is pulled away from the adjunct loader  12200 , the fingers  12216  will retain the cleaning pad  12220  in the cleaning slot  12204 . A user can remove the first and second covers  12240 ,  12242  from the loading slot  12206 , or they can retract automatically, exposing the adhesive sides  12230   a ,  12232   a  of the first and second adjuncts  12230 ,  12232 . The user can clamp the surgical stapler onto the adjuncts  12230 ,  12232  such that the anvil of the surgical stapler closes on the adhesive side  12230   a  of the first adjunct  12230 , and the cartridge of the surgical stapler closes on the adhesive side  12232   a  of the second adjunct  12230 . Clamping can cause the fingers  12216  to deflect, such as retracting into the frame  12202 . The first and second adjuncts  12230 ,  12232  will attach to the jaws, and the surgical stapler can be unclamped and pulled away from the adjunct loader  12200 . This motion will cause the adjuncts  12230 ,  12232  to be pulled away as well, and the adjuncts  12230 ,  12232  can then be deployed in an operation. 
     While the covers can be manually removed, covers in other embodiments can be automatically retracted upon clamping of a surgical stapler on the cleaning pad. For example,  FIGS. 93-94  illustrate an adjunct loader  12300  similar to the adjunct loader  12200 . The adjunct loader  12300  can have a frame  12302 , a cleaning slot  12304 , and a loading slot  12306 . The frame  12302  can have an approximate M shape and can have internal support structures. For example, posts  12316  can extend inward from the frame  12302  to provide support to an upper internal framework  12318  and a lower internal framework  12320 . The upper and lower internal framework  12318 ,  12320  can extend throughout an interior of the frame  12302  and be configured to provide support to material disposed within the slots  12304 ,  12306  and to facilitate receipt of the end effector. For example, the upper and lower internal framework  12318 ,  12320  can have angled ends  12318   a ,  12320   a  that extend at an angle into the slots  12304 ,  12306  to guide the jaws into the slots  12304 ,  12306 . The slots  12304 ,  12306  can take the form of longitudinal openings formed in the frame  12302  and can be sized and shaped to receive a linear end effector of a surgical stapler therein, such as the staplers  10 ,  50 . The slots  12304 ,  12306  can extend parallel to each other and can have open ends on one side of the frame  12302  and closed ends on an opposite side of the frame  12302 . 
     The cleaning slot  12304  can have a cleaning pad  12322 , similar to cleaning pad  12220 , that extends between the open end  12304   a  and the closed end  12304   b  of the cleaning slot  12304 . A cleaning support structure  12324  can be disposed in one of the outer legs of the M shaped frame  12302 , extending between an external wall  12326  of the frame  12302  and the cleaning pad  12322 , and it can be configured to hold a longitudinal edge of the cleaning pad  12322  in the cleaning slot  12304 . On an opposite side of the cleaning pad  12322  and disposed within the inner leg of the M shaped frame  12302  is a movable lever  12328  that has an approximately L shaped cross-sectional shape. A first end  12328   a  holds a longitudinal edge of the cleaning pad  12322  opposite to the cleaning support structure  12324 . The movable lever  12328  extends through an interior of the frame  12302  toward the loading slot  12306 . A second end  12328   b  of the movable lever  12328  can be disposed in contact with an adjunct cover  12330 . The cleaning support structure  12324  and the movable lever  12328  are configured to move up and down together within the frame  12302  and to be initially in contact with the angled ends  12318   a  that extend at an angle into the cleaning slot  12304 . 
     The loading slot  12306  can have an adjunct  12350  similar to the adjunct  12230  that extends between the open end  12306   a  and the closed end  12306   b  of the loading slot  12306 . A rectangular-shaped adjunct support  12346  can be disposed in one of the outer legs of the M shaped frame  12302  on the opposite side to the cleaning support structure  12324 , extending from an external wall  12342  of the frame  12302  and into the loading slot  12306 , and it can be configured to hold the adjunct  12350  in the loading slot  12306 . A spring  12344  can be disposed between the external wall  12342  and the adjunct cover  12330  and inside the outer leg of the M shaped frame  12302  with the adjunct support  12346 . 
     The cleaning pad  12322  can have a rectangular shape and a tongue that extends from one end of the cleaning pad  12322  adjacent the open end  12304   a  of the cleaning slot  12304 . The cleaning pad  12322  can be held between the upper and lower internal framework  12318 ,  12320  and can be held in the cleaning slot  12304  initially against the angled ends  12318   a . In one embodiment, the cleaning pad  12322  can be made from an abrasive material with a cleaning solvent saturated therein and configured to remove tissue and oily residue. The cleaning pad  12322  can be configured to have an end effector of a surgical stapler clamped thereon and it can be configured to clean one or both sides of the surgical stapler. 
     The adjunct  12350  can have first and second portions  12350   a ,  12350   b  similar to the adjuncts  12230 ,  12232 . The first portion  12350   a  can be placed on top of the adjunct support  12346 , and the second portion  12350   b  can be placed on bottom of the adjunct support  12346 . The first and second portions  12350   a ,  12350   b  can have rectangular shapes, and each portion  12350   a ,  12350   b  can have a tongue that extends adjacent the open end  12306   a  of the loading slot  12306 . The first and second portions  12350   a ,  12350   b  of the adjunct  12350  can extend between the open end  12306   a  and the closed end  12306   b  of the loading slot  12306 . The adjunct  12350  can be held between the upper and lower internal framework  12318 ,  12320 . The adjunct  12350  can have a variety of configurations, as discussed above, and can have a variety of attachment mechanisms thereon, such as an adhesive. The adhesive can be spread on an outward-facing surface of each of the first and second portions  12350   a ,  12350   b  so that each of the surfaces is configured to attach to a tissue-facing surface of a surgical stapler. 
     In this embodiment, the cross-sectional shape of the cover  12340  is U shaped with upper and lower horizontal sidewalls and a shorter vertical sidewall extending therebetween. The cover  12340  can be disposed in the loading slot  12306  such that it surrounds the adjunct  12350 . Each of the upper and lower sidewalls of the U shaped cover  12340  can initially extend over the first and second portions  12350   a ,  12350   b  of the adjunct  12350  and can be configured to cover and protect the adjunct  12350  until use. The vertical sidewall of the U shaped cover  12340  can be disposed within the interior of the inner leg of the M shaped frame  12302  and can contact the second end  12328   b  of the lever arm  12328 . Ends of the upper and lower sidewalls of the cover  12340  opposite the vertical sidewall can extend into the outer leg of the M shaped frame  12302  with the adjunct support  12346  and the spring  12344 , and one of the ends of the upper and lower sidewalls of the cover  12340  can be disposed in contact with the spring  12344 . 
     Initially, the cleaning pad  12322  can be held in an upper starting position in which the lever arm  12328  and the cleaning support structure  12324  support the cleaning pad  12322  and both contact the angled ends  12318   a  of the upper interior framework  12318 . The second end  12328   b  of the lever arm  12328  can extend through the interior of the frame  12302  to the loading slot  12306  and can contact the cover  12340 . The arm  12328  can act on the cover  12340  to force the cover toward the spring  12344 , keeping the spring  12344  compressed between the cover  12340  and the outer wall  12342  and keeping the cover  12340  over the adjunct  12350 . When a surgical stapler, such as the stapler  12360 , clamps onto the cleaning pad  12322 , the movement causes the cleaning pad  12322  to move downward. With movement of the cleaning pad  12322 , the cleaning support structure  12324  and the lever arm  12328  both move downward as well. As they move downward, the second end  12328   b  of the lever arm  12328  moves out of contact with the cover  12340 . As soon as the lever arm  12328  is no longer in contact with the cover  12340 , the spring  12344  decompresses and forces the cover  12340  to move toward the cleaning slot  12304  and out of the loading slot  12306 . The cover  12340  will come to rest in the inner leg of the M shaped frame  12302  with the lever arm  12328 , leaving the adjunct  12350  uncovered, as shown in  FIG. 94 . The spring  12344  can be located at only a single point along the frame  12302 , so the spring  12344  will not block access of a surgical stapler to either side of the adjunct  12350 . In some embodiments, the spring can be anchor in a center position and can be held in a stretched state by the lever. When released, the spring can be configured to retract and pull the covers to the center position. In such embodiments, there is thus no concern with the spring being too off-center to pull the covers or be in the way of the adjuncts. After a user finishes cleaning the end effector of the surgical stapler  12360 , the surgical stapler  12360  can be clamped onto the adjunct  12350  so that the first and second portions  12350   a ,  12350   b  will each attach to opposite sides of the surgical stapler  12360 , as described above. 
     Some embodiments can lack covers while still protecting the adjunct from being disturbed before a user is ready to attach the adjunct to a stapler. For example,  FIGS. 95-96  illustrate an adjunct loader  12400  similar to the adjunct loader  12300  but lacking a formal cover. The adjunct loader  12400  can have a frame  12402 , a cleaning slot  12404 , and a loading slot  12406 . The frame  12402  can have an approximate M shape and can have internal support structures. For example, posts  12416  can extend inward from the frame  12402  to provide support to an upper internal framework  12418  and a lower internal framework  12420 . The upper and lower internal framework  12418 ,  12420  can extend throughout an interior of the frame  12402  and can be configured to provide support to material disposed within the slots  12404 ,  12406 . For example, the upper and lower internal framework  12418 ,  12420  can have angled ends  12418   a ,  12420   a  that extend at an angle into the slots  12404 ,  12406  for engaging adjunct or cleaning material, and for guiding jaws into the slots  12404 ,  12406 . The cleaning slot  12404  and the loading slot  12406  can be formed in the frame  12402 . The slots  12404 ,  12406  can take the form of longitudinal openings through the frame  12402  and can be sized and shaped to receive a linear end effector of the surgical stapler therein, such as the staplers  10 ,  50 . The slots  12404 ,  12406  can extend parallel to each other and can have open ends on one side of the frame  12402  and closed ends on an opposite side of the frame  12402 . 
     The cleaning slot  12404  can have a cleaning pad  12422 , similar to cleaning pad  12322 , that extends between the open end  12404   a  and the closed end  12404   b  of the cleaning slot  12404 . A cleaning support structure  12424  is disposed in one of the outer legs of the M shaped frame  12402 , extending between an external wall  12426  of the frame  12402  and the cleaning pad  12422 , and it can be configured to hold a longitudinal edge of the cleaning pad  12422  in the cleaning slot  12404 . Unlike cleaning support structure  12324 , structure  12424  is immovable and is fixed in place. On an opposite side of the cleaning pad  12422  and disposed within the inner leg of the M shaped frame  12402  are upper and lower levers  12428 ,  12429 . The levers  12428 ,  12429  each have a long, rectangular shape and an arm  12428   a ,  12428   b  that extends into the cleaning slot  12404 . A spring  12430  is disposed between the levers  12428 ,  12429  and biases the levers  12428 ,  12429  away from each other such that the upper lever  12428  is configured to extend along the upper internal framework  12418  and the lower lever  12429  is configured to extend along the lower internal framework  12420  in an initial position. The levers  12428 ,  12429  extend through an interior of the frame  12402  toward the loading slot  12406 . Second ends  12428   b ,  12429   b  of the upper and lower levers  12428 ,  12429  are disposed above and below, respectively, upper and lower applicators  12442 ,  12443  with nozzles  12442   a ,  12443   a  that face into the loading slot  12406 . The upper and lower levers  12429 ,  12429  are configured to move up and down with application of force to the arms  12428   a ,  12429   a  that overcomes the spring force of spring  12430 . 
     The loading slot  12406  can have upper and lower adjuncts  12450 ,  12451 , similar to adjunct  12350 , that extends between the open end  12406   a  and the closed end  12406   b  of the loading slot  12406 . A rectangular-shaped adjunct support  12446  is disposed in one of the outer legs of the M shaped frame  12402  on the opposite side to the cleaning support structure  12424 , extending from an external wall  12442  of the frame  12402  across the loading slot  12406  and terminating in the inner leg of the M shaped frame  12402 , and it is configured to hold the adjuncts  12450 ,  12451  in the loading slot  12406 . 
     The cleaning pad  12422  can have a rectangular shape and a tongue that extends from one end of the cleaning pad  12422  and adjacent the open end  12404   a  of the cleaning slot  12404 . The cleaning pad  12422  can be held between the upper and lower internal framework  12418 ,  12420  and between the arms  12428   a ,  12429   a  of the upper and lower levers  12428 ,  12429 . In one embodiment, the cleaning pad  12322  can be made from an abrasive material with a cleaning solvent saturated therein and configured to remove tissue and oily residue. The cleaning pad  12422  can be configured to have an end effector of a surgical stapler closed thereon and can be configured to clean one or both sides of the surgical stapler, such as the anvil side. 
     The upper adjunct  12450  can be placed on top of the adjunct support  12446 , and the lower adjunct  12451  can be placed on bottom of the adjunct support  12446 . The adjuncts  12450 ,  12451  can have rectangular shapes, and each one can have a tongue that extends adjacent the open end  12406   a  of the loading slot  12406 . The adjuncts  12450 ,  12451  can extend between the open end  12406   a  and the closed end  12406   b  of the loading slot  12406 . The adjuncts  12450 ,  12451  can be held between the upper and lower internal framework  12418 ,  12420 . The adjuncts  12450 ,  12451  can have a variety of configurations, as discussed above, and can have a variety of attachment mechanisms. For example, the adjuncts  12450 ,  12451  can have no attachment mechanism thereon, and instead can be positioned adjacent to the upper and lower applicators  12442 ,  12443 . 
     Initially, as shown in  FIG. 95 , the upper and lower arms  12428   a ,  12429   a  are expanded above and below the cleaning pad  12422 . The second ends  12428   b ,  12429   b  can extend through the interior of the frame  12402  to the loading slot  12406  and are positioned above and below the upper and lower applicators  12442 ,  12443 . The spring  12430  keeps the upper and lower levers  12429 ,  12429  in this expanded configuration. When a surgical stapler, such as the stapler  12460 , clamps onto the cleaning pad  12422 , the stapler  12460  clamps onto the arms  12428   a ,  12429   a  of the upper and lower levers  12428 ,  12429  and forces the arms  12428   a ,  12429   a  to move toward one another against resistance of the spring  12430 . The compressing movement of the arms  12428   a ,  12429   a  cause the upper and lower levers  12428 ,  12429  to move toward one another, causing the ends  12428   b ,  12429   b  to also move toward one another. The ends  12428   b ,  12429   b  compress against the upper and lower applicators  12442 ,  12443 , causing adhesive to squirt from the nozzles  12442   a ,  12443   a  that face into the loading slot  12406 . An adhesive is thus applied to the outward facing surfaces of the adjuncts  12450 ,  12451 . A person skilled in the art will appreciate that multiple applicators can be disposed along the entire length of each adjunct, as needed. After a user finishes cleaning the surgical stapler  12460 , the surgical stapler  12460  can be clamped onto the upper and lower adjuncts  12450 ,  12451  with the newly applied adhesive so that the upper and lower adjuncts  12450 ,  12451  will each attach to opposite sides of the jaws of the surgical stapler  12460 . 
     While the adhesive is applied in this embodiment, other application methods are possible. For example, in some embodiments a heat activated or softened adhesive can be applied to the adjunct. Clamping a surgical stapler onto a cleaning side of an adjunct loader can activate a heater within the loader that can heat and/or apply a heat activated or softened adhesive to the adjunct(s). For instance, the stapler can clamp onto the adjunct, causing the loading slot to sense the presence of the stapler and hold the end effector while heating PDS attachment points that affix adjuncts to one or both sides of the end effector. In such an embodiment, lights on the adjunct loader (such as green and red LEDs) can indicate when the adjunct(s) are attached and when the adjunct loader releases the end effector. 
     The adjunct loaders are not limited to horizontal configurations or manual cleaning and loading. For example, in some embodiments a box can be used with vertical slots. The first slot can have a cleaning system to clean the end effector, similar to the methods described above or incorporating a motor, solvents, scrub brushes, etc. Another slot could apply the adjunct, similar to the methods described above or by a motorized process. In other embodiments activation of the cleaning step could automatically trigger the loading step. In various embodiments, cleaning and loading can be disposed in separate housings. 
     End Effector with Adjunct Materials 
     An adjunct can be releasably retained on a jaw of an end effector for a surgical tool using various retaining or attachment features. In some implementations, the attachment feature can be disposed over the adjunct material and it can be releasably coupled to the jaw on which the adjunct is disposed. The adjunct material can be separated from the jaw in a suitable way. For example, the attachment feature retaining the adjunct on the jaw can be cut by a suitable cutting element (e.g., a knife) as the cutting element translates distally to cut tissue retained between the jaws. In some embodiments, when staples are ejected from staple-holding cavities of a cartridge, the staples cause the adjunct material to be separated from the jaw. For example, the force with which the staples are ejected can cause the adjunct material to be disengaged from the jaw. Additionally or alternatively, one or more portions of the attachment feature, or the entire attachment feature can be biodegradable and/or bioabsorbable, and the attachment feature or a portion thereof can therefore remain with the adjunct material when it is transferred to a treatment site in a patient. 
     In some implementations, an adjunct material is releasably retained on a jaw of an end effector using an attachment feature having a retaining filament. The retaining filament can have an intermediate portion and first and second ends disposed on opposed sides of the intermediate portion. Each of the first and second ends can have a respective end feature configured to mate with the jaw. To retain the adjunct material on the jaw, the attachment feature can be arranged such that at least a part of its intermediate portion is disposed over the adjunct material and such that the first and second ends are spaced apart. The first and second ends can be disposed on a side of the jaw opposed to the tissue-facing surface, and they can be spaced apart across a cutting element channel of the jaw. It should be appreciated that, the “first” and “second,” as used herein in connection with the ends of the retaining filament or in connection with any other elements, features, or portions described herein, are used for the description purposed only, and not to indicate any particular order. 
       FIGS. 97-99  illustrate an implementation of an adjunct material  13100  releasably retained on a jaw of an end effector  13102  in accordance with the described techniques. The end effector  13102 , shown only partially in  FIG. 97 , can be used with any suitable surgical instrument, for example, a linear surgical stapler (e.g., stapler  10  in  FIG. 1 , stapler  50  in  FIG. 4 , or any other surgical stapler) that is suitable for use with at least one adjunct. The end effector  13102  can be coupled to a distal end of a shaft of the surgical stapler (not shown). The jaw of the end effector  13102  is in the form of a cartridge body  13104  with a plurality of staple cavities configured to seat staples therein. The staple cavities, which are obscured by the adjunct material  13100  in  FIG. 97 , open on a tissue-facing surface  13106  of the cartridge body  13104 . The cartridge body  13104  can be or can have a removable and replaceable cartridge retained therein, or, in some embodiments, the cartridge body  13104  can be part of a disposable loading unit removably coupled to an elongate shaft of a surgical instrument. 
     Although not shown in  FIG. 97 , the end effector  13102  also has an anvil opposing the cartridge body  13104 , with a plurality of staple forming cavities formed on a tissue-facing surface thereof. It should be appreciated that the adjunct material  13100  is shown in  FIG. 97  to be releasably retained on the jaw in the form of the cartridge body  13104  by way of example only, as an adjunct material can be retained in a similar manner on an anvil of an end effector as well. 
     As shown in  FIG. 97 , the adjunct material  13100  is retained on the cartridge body  13104  using an attachment feature in the form of an elongate retaining filament  13108 . In this implementation, the retaining filament  13108  has an intermediate portion  13110  and first and second ends  13112   a ,  13112   b  disposed on opposed sides of the intermediate portion  13110 , which are shown in  FIG. 99 . As shown in  FIG. 97 , the retaining filament  13108  is arranged on the cartridge body  13104  such that at least a part of the intermediate portion  13110  is disposed over the adjunct material  13100 . The intermediate portion  13110  of the retaining filament  13108  also encompasses opposed sides walls of the cartridge body  13104 , one of which, side wall  13105 , is shown in  FIG. 97 . 
     In this implementation, the intermediate portion  13110  of the retaining filament  13108  extends over the side walls of the cartridge body  13104  such that the first and second ends  13112   a ,  13112   b  are spaced apart. In particular, the first and second ends  13112   a ,  13112   b  are disposed on a side  13116  (back side when the end effector&#39;s jaws are closed) of the cartridge body  13104  that is opposed to the tissue-facing surface  13106  thereof, as shown in  FIG. 99 . The first and second ends  13112   a ,  13112   b  can be spaced apart across a cutting element channel  13113  of the cartridge body  13104  extending longitudinally across a mid-portion of the cartridge body  13104 . 
     At least a portion or the entirety of the retaining filament  13108  can be removably attached to the cartridge body  13104  in a variety of different ways. For example, in the illustrated embodiments, the retaining filament  13108  can be attached to the cartridge body  13104  using a hot-melt adhesive or any other suitable type of adhesive or glue material. The adhesive can be, for example, polydioxanone (PDO) that can function as an adhesive when heated. Additionally or alternatively, cyanoacrylates or UV curing adhesives can be used. 
     The retaining filament  13108  can be used to retain the adjunct material  13100  on the jaw  13104  using one or more suitable features that can be formed on the jaw and/or on the adjunct material. In the illustrated example, as shown in  FIGS. 97 and 98 , the cartridge body  13104  has retaining members  13118   a ,  13118   b  disposed at opposed sides  13120   a ,  13120   b  of the tissue-facing surface  13106  in proximity to the respective edges of the tissue-facing surface  13106 . Each of the retaining members  13118   a ,  13118   b  can be in the form of a pair of adjacent posts, each of which is configured to engage at least a part of the intermediate portion  13110  of the retaining filament  13108 .  FIG. 98 , showing the retaining member  13118   a , illustrates a pair of adjacent posts  13122   d ,  13122   p  disposed on the side  13120   a  of the tissue-facing surface  13106  of the cartridge body  13104 , in proximity to the edge  13121   a  of the tissue-facing surface  13106 . The distance between the adjacent posts  13122   d ,  13122   p  is such that the posts  13122   d ,  13122   p  engage the part of the intermediate portion  13110 , indicated in  FIG. 98  as the part  13124  that extends between the posts  13122   d ,  13122   p . The part  13124  of the retaining filament  13108  passing between the posts  13122   d ,  13122   p  can be engaged with the posts  13122   d ,  13122   p  via interference fit. As shown in  FIG. 97 , similar to the retaining member  13118   a  ( FIG. 98 ), the retaining member  13118   b  formed on the opposite side  13120   b  of the tissue-facing surface  13106  can be in the form of a pair of adjacent posts. 
     In some embodiments, the posts in a pair of posts formed on the tissue-facing surface of the jaw can be spaced from one another such that they have a portion of the retaining filament (e.g., an intermediate portion) passing therethrough without being engaged between the posts. In this way, the posts ensure that the retaining filament is positioned as desired and prevent the retaining filament from sliding proximally or distally. Additionally or alternatively, the retaining filament can be retained over the jaw&#39;s surface using adhesive which can be used to couple one or more portions of the retaining filament to the jaw. 
     As shown in  FIGS. 97 and 98 , the posts  13122   d ,  13122   p  are disposed along the edge  13121   a  such that the post  13122   d  is more distal (e.g., closer to the distal end  13104   d  of the cartridge body  13104 ) than the adjacent post  13122   p . Also, in the illustrated exemplary implementation, the posts  13122   d ,  13122   p  are offset by the same or substantially the same distance from the edge of the cartridge body  13104  such that the posts  13112   d ,  13112   p  are disposed along the same line parallel to a longitudinal axis  13 A 1  of the cartridge body  13104 . It should be appreciated, however, that the posts  13122   d ,  13122   p  can be disposed on the tissue-facing surface  13106  in other ways. Moreover, more than two posts or other retaining elements can be formed on the tissue-facing surface  13106  for engaging the part of the intermediate portion  13110 . Furthermore, in some embodiments, the retaining member can be in the form of a single element formed on the tissue-facing surface  13106 , the single element having one or more prongs, arms, or other retaining elements configured to frictionally engage an attachment features therebetween. As another options, different types of retaining members can be formed on opposed sides of the tissue-facing surface of the jaw of an end effector. 
     The adjunct material  13100  releasably retained on the tissue-facing surface  13106  of the jaw  13104  can have a variety of different configurations. As shown in  FIG. 97 , the adjunct material  13100  is generally rectangular and it is sized such that its width is substantially the same as the width of the tissue-facing surface  13106 . The length of the adjunct material  13100  can be greater than that of the tissue-facing surface  13106 —as shown in  FIG. 97 , the adjunct  13100  extends distally beyond the tissue-facing surface  13106 . This makes it possible to retain the adjunct  13100  using the retaining members  13118   a ,  13118   b  formed at close proximity to the distal end of the tissue-facing surface  13106 . 
     The adjunct material  13100  can have features that facilitate its temporary engagement with the cartridge body  13104 . Thus, as shown in  FIGS. 97 and 98 , the adjunct material  13100  has cut-outs  13126   a ,  13126   b  formed on opposite sides thereof such that the retaining members  13118   a ,  13118   b  are disposed within the cut-outs  13126   a ,  13126   b , respectively. 
     In the illustrated implementation, the cartridge body  13104  can have, in addition to the retaining members  13118   a ,  13118   b , other features that facilitate releasable attachment of the adjunct material  13100  to the cartridge body  13104 . Thus, as shown in  FIG. 99 , the side  13116  of the cartridge body  13104  opposed to the tissue-facing surface  13106  has roughened portions  13130   a ,  13130   b  which the first and second ends  13112   a ,  13112   b  of the retaining filament  13108  engage frictionally. The first and second ends  13112   a ,  13112   b  can have end features in the form of flattened leaf portions or members  13114   a ,  13114   b  (or other types of end features) formed thereon that are configured to frictionally engage with the roughened portions  13130   a ,  13130   b , respectively.  FIG. 99  illustrates that the first and second ends  13112   a ,  13112   b  with the leaf members  13114   a ,  13114   b  are spaced apart across the cutting element channel  13113  of the cartridge body  13104 . 
     The leaf portions can be formed in a variety of ways. For example, they can be pre-formed elements with a texture and/or surface features that allow them to engage the roughened portions. In some embodiments, however, the leaf portions can be formed by heat-pressing or otherwise processing end portions of the retaining filament to flatten them and thus form leaf-like ends. In such embodiments, the end portions of the retaining filament can be caused to deform and to be “pressed” onto the roughened portions. The heat pressing can be performed in a variety of ways, for example, by pressing the end portion of the retaining filament (which can be made from a thermoplastic material) into the roughened portions with a heated iron device so that the thermoplastic material is heated and cooled after mechanically “locking” into the roughened portions of the jaw. 
     The roughened portions  13130   a ,  13130   b  can be created in many different ways. In the illustrated implementation, they are formed by modifying a surface texture of a portion of the cartridge&#39;s side  13116 . For example, the portions of the cartridge&#39;s side  13116  can be knurled or otherwise roughened to create the roughened portions  13130   a ,  13130   b  of a desired size at appropriate locations.  FIG. 101  illustrates an example of a knurled or roughened portion  13140 , which can be any of the roughened portions  13130   a ,  13130   b . As shown in  FIG. 101 , the roughened portion  13140  has a regular pattern of small four-sided pyramids, though the regular pattern can be formed from elements of any other type(s). Also, the roughened portion  13140  can be an irregular rough portion configured to engage with a portion of an attachment feature, e.g., the first and second ends  13112   a ,  13112   b  with the leaf portions  13114   a ,  13114   b  or with otherwise shaped elements. 
     The roughened portions  13130   a ,  13130   b  can be created in any suitable manner. For example, they can be created by laser etching, chemically etching, heat altering (flame treated, heat pressed/stamped, etc.) or mechanically etching (grinding, sand blasting, CO 2  blasting, etc.) the surface of the jaw. In some implementations, the roughened portions  13130   a ,  13130   b  can be created by depositing certain materials (e.g., pressure-sensitive adhesives) over the surface of the cartridge body  13104 , or by otherwise modifying the texture of a portion of the side  13116  of the cartridge body  13104 . 
     Accordingly, in the example of  FIGS. 97-99 , a mid-portion of the intermediate portion  13110  of the retaining filament  13108  extends over the adjunct material  13100  and portions extending from both sides of the mid-portion encompass the opposed side walls of the cartridge body  13104  such that the spaced apart first and second ends  13112   a ,  13112   b  are disposed over the side  13116  opposed to the tissue-facing surface  13106 . The adjunct material  13100  is releasably retained on the cartridge body  13104  using the pairs of the adjacent posts  13118   a ,  13118   b  and the roughened portions  13130   a ,  13130   b.    
     The retaining filament  13108  can have any form and it can be made from any suitable materials. For example, it can be in the form of a suture, wire, cable, strap, or in any other form. It can be made from any suitable absorbable or non-absorbable polymers, examples of which include polyglactin, polyglycolic acid, catgut, polyglecaprone, polydioxanone, etc. Non-limiting examples of non-dissolvable suture materials include polypropylene, polyamide, polyester, silk, etc. In some embodiments, the retaining filament  13108  can be formed from at least partially resilient and/or pliable material such that it can be manipulated to conform to a shape of a body of a jaw which it partially encompasses. 
     The end features in the form of leaf members  13114   a ,  13114   b  formed on the first and second ends  13112   a ,  13112   b  of the retaining filament  13108 , which can be formed integrally with the retaining filament  13108  or can be coupled to the retaining filament  13108  in a suitable manner, can also be formed from any suitable material(s), including the absorbable or non-absorbable polymers mentioned above. As mentioned above, each leaf member can be formed by pressing (e.g., heat-pressing) a portion of the retaining filament onto the jaw&#39;s surface. In some implementations, the leaf members  13114   a ,  13114   b , or other members configured to engage the roughened portions  13130   a ,  13130   b , can be made from a relatively rigid material. The leaf members  13114   a ,  13114   b  can have surface features (e.g., ridges, hooks, barbs, or any other protruding features) formed thereon that allow the leaf members  13114   a ,  13114   b  to frictionally and removably engage with the roughened portions  13130   a ,  13130   b . Furthermore, in some embodiments, the leaf members  13114   a ,  13114   b  can be formed from at least partially magnetic material such that they can be magnetically retained on the roughened portions  13130   a ,  13130   b . Also, in other embodiments, the leaf members  13114   a ,  13114   b  can be coupled to the roughened portions  13130   a ,  13130   b  using a polymer-based magnetic gels, or in other manner. 
     The roughened portions can be formed at any one or more portions of the jaw that can be engaged with a retaining filament. In the implementations described above, the roughened portions can be formed on a side that is opposite to a tissue-facing surface, such as an upper side of an anvil or a backside of a cartridge. In some implementations, additionally or alternatively, regardless of their configuration(s) and the way in which they are formed, one or more roughened portions can be formed on various others portions of a jaw of an end effector. For example,  FIG. 100  shows an example of a jaw  13202  of an end effector having an adjunct material  13200  releasably retained thereon using an attachment feature. The attachment feature is in the form of a retaining filament  13201  engaged with roughened portions formed on opposed side walls of the jaw  13202 . The engagement can be chemical (e.g., using an adhesive), frictional or other mechanical engagement, or any other type of engagement, including a combination of different ways. In some embodiments, a heat pressing approach can be used to allow mechanical interlocks of complementary matches of the surface geometry. 
     In this example, the jaw  13202  is in the form of a cartridge body which can be similar to the cartridge body  13104  in  FIGS. 97-99 . The adjunct material  13200 , which can be similar to the adjunct material  13100  ( FIGS. 97-99 ) is disposed on a tissue-facing surface  13206  of the jaw  13202 . Similar to the adjunct material  13100 , the adjunct material  13200  has cut-outs  13203   a ,  13203   b  formed in proximity to a distal end  13200   d  thereof on both long sides of the adjunct  13200 . 
     As shown in  FIG. 100 , side walls of the cartridge body  13104  can be roughened, which can be done in a manner similar to a manner in which the roughened portions  13130   a ,  13130   b  are created on the cartridge body  13104 .  FIG. 100  illustrates that a portion of one of the side walls ( 13208 ) of the jaw  13202  is roughened to thus form a roughened portion  13210 . A portion  13205  of the retaining filament  13201 , encompassing the side wall of the jaw  13202 , frictionally engages the roughened portion  13210  and thereby releasably retains the adjunct material  13200  on the jaw  13202 . The opposite side of the jaw  13202 , which is not shown in  FIG. 100 , can have similar roughened portion which the retaining filament  13201  encompassing that side wall frictionally engages. The jaw  13202  can also have one or more roughened portions on a side thereof that is opposed to its tissue-facing surface  13206 , and such roughened portions can be similar to the roughened portions  13130   a ,  13130   b  of the jaw  13204  shown in  FIG. 99 . Also, although the jaw  13202  is shown without any other retaining features that can be used to temporarily engage the retaining filament  13201  with the jaw  13202 , it should be appreciated that the jaw  13202  can have other retaining features. For example, the jaw  13202  can include retaining members similar to the retaining members  13118   a ,  13118   b  in the form of pairs of adjacent posts ( FIGS. 97 and 98 ), roughened portions on the backside side of the jaw and/or any other retaining features. 
       FIG. 102  illustrates another implementation of retaining members formed on a jaw  13302  of an end effector having an adjunct material  13300  releasably retained thereon. In this example, a side  13304  (upper side) of the jaw  13302  that is opposite to a tissue-facing surface of the jaw  13302  is shown (e.g., the side  13116  of the jaw  13102  in  FIG. 99 ). In  FIG. 102 , the jaw  13302  is in the form of an anvil. However, as a person skilled in the art will appreciate, an end effector&#39;s jaw having retaining members as described in connection with  FIG. 102  can be a cartridge body. 
     The adjunct material  13300  is releasably retained on the jaw  13302  using an attachment feature in the form of a retaining filament  13301 , portions of which are shown in  FIG. 102 . The retaining filament  13301  has an intermediate portion a part of which is disposed over the adjunct  13300  (not shown in  FIG. 102 ) and other parts of which (e.g.,  13303 ) encompass the jaw&#39;s side wall. 
     The retaining filament  13301  also has first and second ends  13305   a ,  13305   b  disposed on both sides of the intermediate portion adjacent to the parts of the retaining filament  13301  encompassing the side wall of the jaw  13302 . In the example shown in  FIG. 102 , the first and second ends  13305   a ,  13305   b  are disposed on the upper side  13304  of the jaw  13302  and retained on that side via the respective retaining members. The retaining members are spindle-type retaining members  13306   a ,  13306   b  disposed on opposed sides of the surface of the jaw&#39;s side  13304  in proximity to the edges of the jaw  13302 . Each of the spindle-type retaining members  13306   a ,  13306   b  is a generally cylindrical member having a relatively small diameter and height. For example, in at least one embodiment, the diameter of the retaining members  13306   a ,  13306   b  can be about 0.060 inches, and its height can be about 0.025 inches. Regardless of its size, each of the of the spindle-type retaining members  13306   a ,  13306   b  has a radial recess formed in the member&#39;s side wall around the entire circumference of the wall. Thus,  FIG. 102  shows that the retaining members  13306   a ,  13306   b  have radial recesses  13308   a ,  13308   b , respectively. The retaining members  13306   a ,  13306   b  also have respective holding notches or recesses  13310   a ,  13310   b  that are formed along each of the member&#39;s diameter on the top side of that member. 
     It should be appreciated that the spindle-type retaining members  13306   a ,  13306   b  are shown in  FIG. 102  by way of example only, and that any other features can be used to couple the retaining filament to the jaw. For example, in some embodiments, the jaw (a cartridge or an anvil) can be configured to decrease in width so as to “grab” the filament. As another example, the jaw can have a groove with a cam feature, a post with an adjacent cam feature, or any other feature(s) configured to retain the retaining filament which can be a rope, wire, suture, thread, or any other element. 
     The radial recesses  13308   a ,  13308   b  and the holding recesses  13310   a ,  13310   b  are used to retain therein a portion of the at least one of the first and second ends  13305   a ,  13305   b . In particular, as shown in  FIG. 102 , the retaining member  13306   a  has the first end  13305   a  of the retaining filament  13301  receiving within the radial recess  13308   a  such that the first end  13305   a  is wrapped around the retaining member  13306   a . After the first end  13305   a  encircles the retaining member  13306   a  at least once, a portion of the first end  13305   a  is fittingly received through the top recess  13310   a  of the retaining member  13306   a . In this way, the first end  13305   a  of the retaining filament  13301  engages with the retaining member  13306   a.    
     The holding recesses  13310   a ,  13310   b  can have a configuration that facilitates retention of a portion of the retaining filament  13301 . For example, the holding recess  13310   b  of the retaining member  13306   b  (shown in  FIG. 102  free of the retaining filament for the illustration purposes only) has a first wider portion  13307  and a second, narrower portion  13309  extending from the first portion  13307 . The holding recess  13310   a  of the retaining member  13306   a  is configured in a similar manner. In use, after a portion of the second end  13305   b  of the retaining filament  13301  is wrapped around the radial recess  13308   b , the first portion  13307  receives therein another portion of the second end  13305   b  and this filament&#39;s portion is then received through the narrower portion  13309  of the holding recess  13310   b  so as to be fittingly retained therein. Thus, in use, the second end  13305   b  can be slightly stretched and passed through the holding recess  13310   b  so as to be retained within the recess. The first end  13305   a  is engaged with the holding recess  13310   a  in a similar manner and is shown in  FIG. 102  as being wrapped around the radial recess  13308   a  and retained within the holding recess  13310   a . In this way, both ends of the retaining filament  13301  are temporarily engaged with the jaw  13302 . 
     As in the examples above, the retaining filament  13301  can be disengaged from the jaw  13302  when a knife or other cutting element traverses a cutting element channel  13313  and thereby cuts a portion of the retaining filament  13301  disposed over the adjunct material  13300 . The rest of the retaining filament  13301  remains with the jaw  13302 . 
     It should be appreciated that, regardless of the specific configurations of attachment features (e.g., retaining filaments or other features) described herein, jaw(s) of an end effector, the attachment features, and one or more adjunct materials are configured such that the jaw having one or more adjunct materials releasably retained thereon using one or more attachment features fits within a trocar. In some embodiments, one or more attachment features (e.g., posts or other features) can be formed at a bottom of one or more recesses formed in a jaw, such that the attachment features do not affect the overall size of the jaw. The adjunct material(s) are configured to be retained on the jaw in a manner that does not interfere with normal manipulations and operation of the jaw. 
     An adjunct material can be releasably retained on an end effector&#39;s jaw using various other types of attachment features in the form of a retaining filament. For example, in some implementations, an attachment feature has an intermediate portion and first and second ends with deformable elements. The deformable elements can be configured such that, when the attachment feature is disposed over an adjunct material placed on the jaw of an end effector, the deformable elements reversibly deform and change their configuration as they are received within openings or recesses in the jaw. When the deformable elements are engaged with the recesses in the jaw, they at least partially adopt their non-deformed configuration to thus retain the attachment feature in place. 
       FIGS. 103 and 104  illustrate an example of an adjunct material  13400  configured to be releasably retained on a jaw  13402  of an end effector using an attachment feature  13401 . The attachment feature  13401  has an intermediate portion  13404  and first and second ends  13406   a ,  13406   b . The intermediate portion  13404 , in turn, includes a mid-portion  13408  and first and second arm portions  13410   a ,  13410   b  extending from opposite sides of the mid-portion  13408  and terminating at the first and second ends  13406   a ,  13406   b . As shown in  FIGS. 103 and 104 , the first and second ends  13406   a ,  13406   b  have deformable elements  13412   a ,  13412   b  configured to be reversibly deform. In this example, the deformable elements  13412   a ,  13412   b  are in the form of t-shaped barb members. However, it should be appreciated that the deformable elements  13412   a ,  13412   b  can have any other suitable configurations. For example, they can be configured as Christmas tree-type, umbrella-like, or any other types of deformable elements configured to be used to retain an adjunct material on a jaw as discussed in more detail below. 
     The jaw  13402  can be configured in many different ways. In the example of  FIGS. 103 and 104 , the jaw  13402  is in the form of a cartridge body or cartridge having a plurality of staple cavities  13403  configured to seat staples therein, the staple cavities opening on a tissue-facing surface  13405  of the cartridge  13402 . As shown in  FIG. 103 , the staple cavities  13403  form three rows on both sides of a cutting element channel  13407  extending through a mid-portion of the cartridge  13402  along a longitudinal axis  13 A 2  thereof. It should be appreciated, however, that any suitable number of the staple cavities  13403  can have any suitable pattern(s) on the tissue-facing surface  13405  of the jaw  13402 , as the described embodiments are not limited in this respect. 
     The cartridge  13402  can have suitable features configured to retain an adjunct material thereon. As shown in  FIGS. 103 and 104 , the cartridge  13402  has a first pair of recesses  13414   a ,  13414   b  formed in the tissue-facing surface  13405  thereof. The recesses of the first pair of recesses  13414   a ,  13414   b  are spaced from opposed edges of the tissue-facing surface  13405  and are disposed on opposed sides of the cutting element channel  13407  extending centrally through the cartridge  13402  along the longitudinal axis  13 A 2  thereof. The first recesses  13414   a ,  13414   b  are formed on a distal portion  13405   d  of the tissue-facing surface  13405  that is free of the staple cavities, as shown in  FIGS. 103 and 104 . In some embodiments, however, the first recesses  13414   a ,  13414   b  can be formed within the area of the tissue-facing surface  13405  having the staple cavities formed thereon. 
     The first recesses  13414   a ,  13414   b  formed in the tissue-facing surface  13405  of the cartridge  13402  can have many different configurations. In this example, the first recesses  13414   a ,  13414   b  can have a generally oval cross-sectional shape and they can be sized to allow therewithin the first and second ends  13406   a ,  13406   b  with the deformable elements  13412   a ,  13412   b . Although not shown in  FIGS. 103 and 104 , the inner walls of the first recesses  13414   a ,  13414   b  can have a configuration and size that allow the deformable elements  13412   a ,  13412   b  to be at least partially deform as they are received within the recesses  13414   a ,  13414   b  and to then return at least in part to their non-deformable configuration to thus be retained in the recesses  13414   a ,  13414   b . Furthermore, in some implementations, the first recesses  13414   a ,  13414   b  can be formed through the entire thickness of the jaw  13402  such that the deformable elements  13412   a ,  13412   b  return at least in part to their non-deformable configuration on the side of the jaw  13402  that is opposed to the tissue-facing surface  13405  of the jaw  13402 . 
     The adjunct material  13400  can have many different configurations. In the illustrated embodiment, the adjunct material  13400  is generally rectangular, with its width and length generally corresponding to the width and length of the tissue-facing surface  13405  of the cartridge  13402 . In the illustrated example, the adjunct material  13400  has features configured to retain it on the cartridge  13402 . In particular, the adjunct material  13400  has a second pair of through openings or recesses  13418   a ,  13418   b  formed therein. As shown schematically in  FIGS. 103 and 104 , the second recesses  13418   a ,  13418   b  are formed at locations in the adjunct material  13400  that correspond to the location of the first recesses  13414   a ,  13414   b  formed in the tissue-facing surface  13405  of the cartridge  13402 . Each of the second recesses  13418   a ,  13418   b  can have a size that is similar to sizes of the first recesses  13414   a ,  13414   b , or the size of each of the second recesses  13418   a ,  13418   b  can be slightly smaller than that of the first recesses  13414   a ,  13414   b.    
     In use, when the adjunct material  13400  is disposed on the tissue-facing surface  13405  of the cartridge  13402 , the adjunct&#39;s second recesses  13418   a ,  13418   b  align with the cartridge&#39;s first recesses  13414   a ,  13414   b . In this way, the second recess  13418   a  is disposed above and communicates with the first recess  13414   a , and the second recess  13418   b  is disposed above and communicates with the first recess  13414   b . The retaining filament  13301  is manipulated to cause its first and second ends  13406   a ,  13406   b  to be pushed through the adjunct&#39;s second recesses  13418   a ,  13418   b  and then to be allowed within the second recesses  13418   a ,  13418   b  in the cartridge  13402 . The mid-portion  13408  of the retaining filament  13301  is disposed over the adjunct  13400 , as shown in  FIG. 104 . The first and second arm portions  13410   a ,  13410   b  extend through the thickness of the adjunct  13400  and can at least partially extend through the body of the cartridge  13402 . 
       FIG. 103  shows the deformable elements  13412   a ,  13412   b  in their natural, non-deformed state. Thus, for example, in the non-deformed state or configuration of the element  13412   b , its prongs  13413   a ,  13413   b  are perpendicular to a post  13415 . The deformable elements  13412   a ,  13412   b  can be resiliently deformable such that, as they are passed through the second recesses  13418   a ,  13418   b  in the adjunct  13400 , under the load applied thereto, they are caused to accept at least partially non-deformed state, e.g., the prongs  13413   a ,  13413   b  of the element  13412   b  come closer to its post  13415 . In such at least partially unexpanded configuration, the elements  13412   a ,  13412   b  are then passed though the openings of the first recesses  13414   a ,  13414   b  in the jaw  13402 , upon which the elements  13412   a ,  13412   b  return at least in part to their expanded configuration, to be retained within the first recesses  13414   a ,  13414   b . Thus, in the example of the element  13412   b , the prongs  13413   a ,  13413   b  move away from the post  13415  to form an acute angle with the post  13415  or to be disposed perpendicular thereto (if they fully return to the expanded configuration). In the implementations in which the first recesses  13414   a ,  13414   b  in the jaw  13402  are in the form of through openings, the deformable elements  13412   a ,  13412   b  can expand on the surface of the jaw opposite to the tissue-facing surface  13405  thereof. In this way, for example, the prongs  13413   a ,  13413   b  will be pressed against that surface of the jaw. 
     The adjunct material  13400  releasably retained on the cartridge  13402  can be separated from the cartridge  13402  in different ways. For example, a cutting element (e.g., a knife), as it translates through the cutting element channel  13407  formed centrally in the jaw  13402 , can cut the retaining filament  13401  disposed, as shown in  FIG. 104 , above the channel  13407 . 
     It should be appreciated that the cartridge  13102  can have other features for releasably retaining therein the adjunct material  13400 . For example, in some embodiments, a proximal end  13405   p  of the tissue-facing surface  13405  can include retaining members similar to the first recesses  13414   a ,  13414   b . In such embodiments, the adjunct material  13400  can also have openings similar to the second recesses  13418   a ,  13418   b . Additionally or alternatively, other retaining features can be formed on the cartridge and/or on the adjunct. 
     In some embodiments, an end effector can have two separate adjunct materials releasably retained thereon. One (“first”) of the separate adjunct materials can be configured to be disposed on one jaw of the end effector (e.g., a cartridge body), and another (“second”) adjunct material can be configured to be disposed on another jaw of the end effector. The first and second adjunct materials have respective first and second mating features formed at proximal ends thereof. The end effector has an attachment feature formed at a proximal end thereof and configured to mate with at least one the first and second mating features of the first and second adjunct materials. 
       FIGS. 105 and 106  illustrate an implementation of an end effector  13500  having two separate adjunct materials releasably retained thereon. The end effector  13500  can have first and second jaws configured to clamp tissue therebetween, such as a jaw having a cartridge with a plurality of staple cavities configured to seat staples therein, and another, opposing jaw having an anvil with a plurality of staple forming cavities formed on a tissue-facing surface thereof. In this example, only a portion of the end effector  13500  in the form of a jaw having a cartridge body  13502  (also partially shown) is illustrated. 
     The end effector  13500  can be used with any suitable surgical instrument, for example, a linear surgical stapler (e.g., stapler  10  in  FIG. 1 , stapler  50  in  FIG. 4 , or any other surgical stapler) that is suitable for use with at least one adjunct material. The end effector  13500  can be coupled to a distal end of a shaft of the surgical stapler (not shown). The cartridge body  13502  has a plurality of staple cavities  13504  that are configured to seat staples therein and that open on a tissue-facing surface  13506  of the cartridge body  13502 . The cartridge body  13502  can be in the form of a channel that removably and replaceably seats a cartridge therein, or the cartridge body  13502  with the staples can itself be a removable and replaceable unit. Also, in some embodiments, the cartridge body  13502  holding the staples can part of a disposable loading unit removably coupled to an elongate shaft of a surgical instrument. 
     As mentioned above, the end effector  13500  has first and second adjunct materials  13512 ,  13514  configured to be releasably coupled thereto. The end effector  13500  has an attachment feature configured to mate with the first and second adjunct materials  13512 ,  13514 . Specifically, as shown in  FIG. 105 , the end effector  13500  has an attachment feature  13508  formed at a proximal end  13500   p  thereof. In this implementation, the attachment feature  13508  is coupled to a proximal end  13502  of the cartridge body  13502 , though in other implementations of the present subject matter, the attachment feature  13508  can be coupled to an anvil or to element(s) of the end effector that are not part of the cartridge or the anvil. 
     Furthermore, in the described implementation, the attachment feature  13508  is in the form of a substantially cylindrical bar  13510  positioned above the tissue-contacting surface  13506  of the cartridge body  13502  and oriented so as to be transverse to a longitudinal axis  13 A 3  of the end effector  13500 . The cylindrical bar  13510  is coupled to a support member  13511  so as to be positioned above the tissue-contacting surface  13506 , as shown in  FIG. 105 . The cylindrical bar  13510  can be integrally and/or monolithically formed with the support member  13511 , or it can be coupled to the support member  13511  in a suitable member. 
     The first adjunct material  13512  having proximal and distal ends  13512   p ,  13512   d  is configured to be releasably retained on one jaw of the end effector  13500 , such as, in this example, the cartridge body  13502 . The second adjunct material  13514  having proximal and distal ends  13514   p ,  13514   d  is configured to be releasably retained on another, opposed jaw of the end effector  13500 , such as an anvil which is not shown. Each of the first and second adjunct materials  13512 ,  13514  has a respective mating feature at the proximal end  13512   p ,  13514   p  thereof for mating with the end effector&#39;s attachment feature  13508 . In particular, as shown in  FIG. 105 , the first adjunct material  13512  has a first mating feature in the form of first open-ended loop features  13516   a ,  13516   b . Each of the first open-ended loop features  13516   a ,  13516   b  includes an arm  13515   a ,  13515   b  and an open-ended loop  13517   a ,  13517   b . As shown in  FIG. 105 , the open-ended loops  13517   a ,  13517   b  have their gaps or open ends on the top of the loops such that the open ends face away from the cartridge body  13502 , in a direction substantially transverse to the longitudinal axis  13 A 3  of the end effector  13500  and towards the opposed jaw (not shown). As also shown in  FIG. 105 , the open-ended loop features  13516   a ,  13516   b  of the first adjunct material  13512  are formed on the proximal end  13512   p  such that they are spaced away from opposed edges  13513   a ,  13513   b  of the proximal end  13512   p  and are thus formed adjacent to one another and in proximity to a mid-portion of the proximal end  13512   p.    
     The second adjunct material  13514  has a second mating feature in the form of second open-ended loop features  13518   a ,  13518   b . Each of the second open-ended loop features  13518   a ,  13518   b  includes an arm  13521   a ,  13521   b  and an open-ended loop  13523   a ,  13523   b . As shown in  FIG. 105 , the open-ended loops  13523   a ,  13523   b  have their gaps or open ends on the side of the loops such that the open ends face away from the cartridge body  13502 , in a direction substantially parallel to the longitudinal axis  13 A 3  of the end effector  13500 . The open-ended loop features  13518   a ,  13518   b  are formed on the proximal end  13514   p  of the second adjunct material  13514  such that they are adjacent to opposed edges  13519   a ,  13519   b  of the proximal end  13514   p.    
     The configurations of the mating features of the first and second adjunct materials  13512 ,  13514  allow the mating features to mate with the attachment feature  13508  as shown in  FIG. 106 . The open-ended loops of the first and second open-ended loop features  13516   a ,  13516   b ,  13518   a ,  13518   b  have circumferences that are slightly undersized relative to cylindrical bar  13510  such that the open-ended loops can slightly deform to encompass the bar  13510 . The first and second open-ended loop features  13516   a ,  13516   b ,  13518   a ,  13518   b  can be formed from at least partially resilient material such that the features can be snapped onto the bar  13510  through the gaps in the open-ended loops. The non-limiting examples of the materials include polymers such as, e.g., polydioxanone (PDO), poly(glycerol sebacate) (PGS)/poly(lactic acid) (PLA), poly(glycolic acid) (PGA)/polycaprolactone (PCL), trimethylene carbonate (TMC)/PGA, or any other suitable material or a combination of materials. 
     Further, the first and second open-ended loop features  13516   a ,  13516   b ,  13518   a ,  13518   b  are configured to engage the bar  13510  such that the first open-ended loop features  13516   a ,  13516   b  engage the bar  13510  at locations different from locations at which the second open-ended loop features  13518   a ,  13518   b  engage the bar  13510 . In particular, as shown in  FIG. 106 , the first open-ended loop features  13516   a ,  13516   b  engage the bar  13510  at the locations on the bar  13510  between the locations at which the second open-ended loop features  13518   a ,  13518   b  engage the bar  13510 . In this way, both the first and second open-ended loop features  13516   a ,  13516   b ,  13518   a ,  13518   b  movably engage the bar  13510  to thereby engage the separate first and second adjunct materials  13512 ,  13514  with the end effector  13500 . In some embodiments, the open-ended loops can be segmented in such a way that the opposing sides are not directly opposite to one another. For example, the loops can be staggered. 
     In some implementations of the current subject matter, one or both of the first and second adjunct materials  13512 ,  13514  can have additional attachment features configured to releasably couple the adjunct materials  13512 ,  13514  with the respective opposed jaws of the end effector. For example, one or more portions of the second adjunct material  13514  configured to be disposed on the anvil can be releasably coupled to the anvil using an adhesive material. Other attachment features can be formed on the second adjunct material  13514  and/or on the anvil in addition to the second open-ended loop features  13518   a ,  13518   b . Also, in some implementations, the first adjunct material  13512  can be coupled to the cartridge body  13502  using one or more additional attachment features. 
       FIG. 107  illustrates another embodiment of an end effector  13600  having first and second adjunct materials  13612 ,  13614  releasably coupled thereto via respective mating features.  FIG. 107  shows only a portion of the end effector  13600 , a cartridge body  13602 , which is configured to releasably retain thereon the first adjunct material  13612 . An opposed jaw, an anvil, which is not shown in  FIG. 107 , is configured to releasably retain thereon the second adjunct material  13614 . 
     In this implementation, the cartridge body  13602  has the first adjunct material  13612  releasably coupled thereto. The first adjunct material  13612  has a size and shape complementary to a size and shape of a tissue-facing surface of the cartridge body  13602  (obscured by the adjunct material  13612 ), and the first adjunct material  13612  can be coupled to the cartridge body  13602  using adhesive material(s) or in other suitable ways. 
     In this embodiments, the first and second adjunct materials  13612 ,  13614  have respective mating features that are configured to couple (e.g., interlock) to one another to thereby couple the first and second adjunct materials  13612 ,  13614  to one another. Thus, the first adjunct material  13612  has a slot  13616  formed at a proximal end  13612   p  thereof. The second adjunct material  13614 , which can have a size and shape complementary to a size and shape of a tissue-facing surface of the end effector&#39;s anvil (not shown), has a tab  13618  extending from a proximal end  13614   p  thereof and configured to be received within the slot  13616 .  FIG. 108  shows the tab  13618  of the second adjunct material  13614  mating with the slot  13616  of the first adjunct material  13612 . The tab  13618  can have a length such that it engages with the slot  13616  to retain the second adjunct material  13614  in engagement with the first adjunct material  13612 . Also, in use, the tab  13618 , when engaged with the slot  13616 , can operate as a tissue stop to prevent or reduce tissue from being displaced or leaked from the treatment site when the jaws of the end effector  13600  are grasping the tissue. 
     It should be appreciated that the slot  13616  in the first adjunct material  13612  and the tab  13618  in the second adjunct material  13614  are shown by way of example only, as the first and second adjunct materials  13612 ,  13614  can have any other mating features configured to couple with one another. In some embodiments, such mating features can be complementary to one another. 
     In some implementations, the first and second adjunct materials  13612 ,  13614  can be coupled to the respective jaws of the end effector  13600  using other additional features. For example, adhesive can be used to releasably couple the adjunct materials  13612 ,  13614  to the jaws. Any other attachment features can be used additionally or alternatively. 
     In some embodiments, attachment features can be formed on an adjunct material configured to be releasably disposed on a jaw of an end effector. These embodiments can be used in connection with end effectors having gripping features that extend from a shorter side of each staple pocket in a cartridge of the end effector. For example, the gripping features can be implemented in accordance with ECHELON™ Gripping Surface Technology such that each of the staple pockets has opposed extension features configured to provide a grip that holds tissue in place during firing. 
       FIGS. 109, 110A and 110B  illustrate an embodiment of a cartridge  13700  of an end effector (not shown) having gripping extensions formed at staple pockets  13704  in a tissue-contacting surface  13702 . As shown in  FIGS. 109 and 110B , each staple pocket has extension features formed at opposite sides of the pocket along a longitudinal axis of the pocket. For example, a staple pocket  13706  has first and second extension features  13706   a ,  13706   b  formed at opposed sides of the pocket  13706  along a longitudinal axis thereof. Some or all of the other staple pockets can be configured in a similar manner. The extension features  13706   a ,  13706   b  of the staple pocket  13706  typically are formed integrally with the tissue-contacting surface  13702 . 
     The extension features  13706   a ,  13706   b  of the staple pocket  13706  (as well as extension features of other staple pockets) can have any of a variety of configurations. For example, as shown in  FIG. 110B , illustrating by way of example the staple pocket  13706  in cross-section, the extension features  13706   a ,  13706   b  can be in the form of slightly curved features that are also slightly inclined towards a mid-portion of the staple pocket  13706 . It should be appreciated, however, that the extension features  13706   a ,  13706   b  can have any other configurations and that the described techniques are not limited to any particular type of extension features adjacent to staple pockets. 
     In the illustrated example, an adjunct material  13708  is configured to be releasably retained on the tissue-contacting surface  13702  of the cartridge  13700 . The adjunct material  13708  can have a plurality of mating features for releasably mating with the cartridge  13700 . In particular, in this implementation, the mating features are in the form of openings  13710  formed on the side  13712  of the adjunct material  13708  facing the tissue-contacting surface  13702 . The openings  13710  are configured to mate with the extension features formed on the cartridge  13700 . For example, openings  13710   a ,  13710   b  shown in  FIG. 109  are configured to mate with the extension features  13706   a ,  13706   b , respectively, such that the extension features  13706   a ,  13706   b  are received within the openings  13710   a ,  13710   b . Thus, the openings  13710  can be configured to fit the extension features  13706   a ,  13706   b  therewithin, such that the size of the openings  13710  corresponds to the size of the extension features  13706   a ,  13706   b . Also, the openings  13710  can be spaced from one another in accordance with a distance of the extension features  13706   a ,  13706   b  from one another, as discussed in more detail below. 
     The openings  13710  can be formed on the adjunct  13708  at predetermined locations such that each pair of openings (e.g., the openings  13710   a ,  13710   b ) is configured to be mated with corresponding extension features (e.g., the extension features  13706   a ,  13706   b ). The adjunct  13708  can have openings formed thereon that correspond to each of the staple pocket&#39;s extension features, or, in some embodiments, only some of the openings can mate with the extension features, and vice versa. In other words, the number of the openings may be different from the number of extension features. 
     The openings in the adjunct can be relatively small. For example, in at least one embodiment, they can have a diameter of about 0.010 inches, though the openings can have another diameter. In some implementations, the openings can be formed in the adjunct at certain distances from one another without taking into considerations specific pairs of extension features to mate with the pairs of openings. In such implementations, for example, when the adjunct is disposed over a cartridge and some force is applied thereto (e.g., the adjunct is pressed over a tissue-contacting surface of the cartridge), all or at least some of the openings will “find” extensions features to mate with, and vice versa. Thus, the adjunct can have multiple openings at a certain distance from one another (which can be smaller than a distance between the openings that are configured to mate with specific extension features) and at least some of these openings can mate with the extension features of the cartridge. 
     As mentioned above, in the example illustrated, the openings  13710  can be spaced from one another in accordance with a distance of the extension features  13706   a ,  13706   b  from one another. Furthermore, as in the example illustrated, the adjunct material  13708  can be made from at least partially stretchable material such that, when it is placed over the cartridge  13700  (which can be done with application of some force), one or more portions of the adjunct material  13708  can stretch. For example, the portions between at last some of the openings  13710  can stretch so that the openings at opposed sides of the portions are placed in positions for mating with respective extension features. 
     Thus, as illustrated in  FIGS. 110A and 110B , before the adjunct  13708  is placed on the cartridge  13700 , the openings  13710   a ,  13710   b  (as also shown in  FIG. 109 ) are disposed at a distance  13   d   1  from one another. When the adjunct  13708  is caused into engagement with the cartridge  13700  when force is applied thereto (via a user&#39;s hand or using any removable applicator, frame, etc.), the adjunct  13708  is caused to stretch such that the openings  13710   a ,  13710   b  move further apart from one another, as shown by arrows  13714   a ,  13714   b  in  FIG. 110B . In particular, the openings  13710   a ,  13710   b  become spaced apart at a distance  13   d   2  that is greater than the distance  13   d   1  ( FIG. 110A ), as shown in  FIG. 110B . In this way, the openings  13710   a ,  13710   b  become disposed at the distance from one another that allows them to mate with the extension features  13706   a ,  13706   b  of the staple pocket  13706  having a staple  13707  ejectably disposed therein. When the adjunct  13708  is caused to engage the tissue-contacting surface  13702  of the cartridge  13700 , portion(s) of the adjunct  13708 , including the portion between the openings  13710   a ,  13710   b  can be displaced until one or both of the openings receives the corresponding extension feature therein. In other words, the adjunct  13708  can be stretched, until the openings  13710   a ,  13710   b  in the adjunct  13708  engage with the corresponding extension features  13706   a ,  13706   b . Other openings in the adjunct engage the extension features in the cartridge in a similar manner, and the adjunct  13708  thus becomes releasably engaged with the cartridge  13700 . In embodiments in which the number of openings in the adjunct is greater that the number of extension features, at least some of the openings can engage with the extension features in a similar manner. 
     End Effector Configured to Mate with Adjunct Materials 
     In some implementations, an adjunct material is configured to be releasably retained on a jaw of an end effector for a surgical instrument using complementary mating features formed on the jaw and on the adjunct. In particular, the adjunct material can have discrete or longitudinal projections formed thereon at least at distal and proximal ends of the adjunct material. The projections are configured to be received within the complementary recesses formed in a jaw of the end effector to thereby releasably mate the adjunct material with the jaw. In some embodiments, the end effector can include an attachment feature in the form of a polymer attachment layer that can be used to attach the adjunct material to the jaw. 
     Furthermore, the end effector includes a removable applicator member configured to apply force to the adjunct material to cause the adjunct material to be releasably retained on the jaw. The applicator member can be in the form of an applicator or retainer removably coupled to the end effector, or in the form of a frame-like applicator configured to releasably hold the adjunct material, or in other forms. Thus, in some implementations, in use, the applicator member is removably coupled to the end effector and used to apply force to the adjunct material (and in some embodiments to a polymer attachment layer) to cause the projections of the adjunct material (and in some embodiments projections formed on the polymer attachment layer) to be at least partially received within corresponding recesses formed in the jaw. In other implementations, a frame-like applicator member holding at least one adjunct material is clamped between the jaws of the end effector. In this way, force is applied to the applicator member, which causes the applicator member to release the at least one adjunct material and to transfer the at least one adjunct material to at least one respective jaw of the end effector. After use, the applicator member can be separated from the end effector. 
     The described techniques can also employ other ways and structures to releasably retain an adjunct material on at least one jaw of an end effector of a surgical instrument. 
       FIGS. 111-113B  illustrate an example of an end effector  14100  configured to releasably retain an adjunct material on one or both of its first and second opposed jaws configured to clamp tissue therebetween, in accordance with the described techniques. The end effector  14100 , partially illustrated in  FIGS. 111 and 112 , has a first jaw having a cartridge body  14102  and a second jaw having an anvil  14104 . The cartridge body  14102  is configured to releasably retain thereon an implantable adjunct material  14106 . The end effector  14100  can be coupled to a distal end of a shaft of the surgical instrument (not shown). The end effector  14100  can be used in any suitable surgical instrument, for example, a linear surgical stapler (e.g., stapler  10  in  FIG. 1 , stapler  50  in  FIG. 4 , or any other surgical stapler) which can be suitable for use with at least one adjunct. 
     As shown in  FIG. 111 , the cartridge body  14102  has a plurality of staple-holding cavities  14108  configured to seat staples therein, the staple-holding cavities  14108  opening on a tissue-facing surface  14110  of the cartridge  14102 . The staple cavities  14108  form a certain pattern on the surface of the cartridge  14102  which corresponds to a pattern of staple-forming cavities (obscured in  FIG. 111 ) formed in the anvil  14104 . The cartridge body  14102 , also referred to as a cartridge, includes a cutting element channel  14113  extending between distal and proximal ends  14102   d ,  14102   p  of the cartridge  14102 . The knife channel  14113  is configured to receive a cutting element (e.g., a knife) as it moves distally therethrough. As shown in  FIG. 111 , the staple cavities  14108  can form three rows on both sides of the cutting element channel  14113 , though it should be appreciated that the staple cavities  14108  can form any other patterns on the tissue-facing surface  14110 . 
     The cartridge body  14102  can be in the form of a staple channel configured to support a staple cartridge, which can be removably and replaceably seated within the staple channel. Furthermore, in some embodiments, the cartridge  14102  can be part of a disposable loading unit coupled distally to a shaft of a surgical instrument. 
     The end effector  14100  has the implantable adjunct material (or “adjunct”) releasably mounted on one or both of the cartridge  14102  and the anvil  14104 . In the illustrated implementation, the adjunct material  14106  releasably retained on the cartridge  14102  is discussed, though it should be appreciated that the anvil  14104  can also have an adjunct material releasably retained thereon. As shown in FIGS.  111  and  112 , the end effector also includes a loading member  14105  configured to apply force to the adjunct material  14106  to cause the adjunct material  14106  to be retained on the cartridge  14102 , as discussed in more detail below. As also shown in  FIGS. 111 and 112 , and additionally illustrated in  FIGS. 113A-113B , the end effector  14100  can further include a polymer attachment layer  14107  configured to be positioned between the cartridge  14102  and the adjunct material  14106 , as also discussed in more detail below. 
     In the illustrated implementation, the cartridge  14102  can have at least one recess formed therein that opens on its tissue-facing surface  14110 , with the at least one recess being configured to mate with a respective projection formed in the adjunct  14106 . Thus, as shown in  FIGS. 111 and 112 , the cartridge  14102  has at least one first recess  14112   d  formed at the distal end  14102   d  thereof and at least one second recess  14112   p  formed at the proximal end  14102   p  thereof. In the example illustrated, some of the recesses are obscured by the adjunct  14106 , and the at least one first recess  14112   d  is in the form of two recesses formed on opposite sides of the cutting element channel  14113 . The at least one second recess  14112   p  is similarly in the form of two recesses formed on opposite sides of the cutting element channel  14113 . 
     The recesses  14112   d ,  14112   p  formed in the cartridge  14102  can have a variety of different configurations. In the illustrated example, as shown in  FIG. 111 , each of the recesses is a discrete recess that has a generally circular top cross-section such that the recess is cylindrical. It should be appreciated, however, that the recesses in the end effector&#39;s jaw, such as the cartridge, can have other configurations. For example, the recesses can be square, rectangular, semi-circular (e.g., having a semi-circular or oval shape as viewed from the top), and/or they can have any other suitable regular or irregular shapes. Regardless of their specific configuration(s), the recesses formed in the cartridge are configured to receive therein at least a portion of a respective projection formed on an adjunct material or another member, as discussed below. 
     As shown in  FIG. 112 , the adjunct material  14106  has projections that are complementary to the recesses  14112   d ,  14112   p  formed in the cartridge  14102  and that are configured to mate with the recesses  14112   d ,  14112   p  to retain the adjunct material  14106  on the cartridge  14102 . In the illustrated embodiments, the adjunct material&#39;s projection(s) are disposed at least at proximal and distal ends of the adjunct material. In particular, as shown in  FIG. 112 , the adjunct material  14106  has at least one first projection  14116   d  formed at the distal end  14106   d  thereof and at least one second projection  14116   p  formed at the proximal end  14106   p  thereof. In the example illustrated, where some of the projections are obscured, the at least one first projection  14116   d  and the at least one second projection  14116   p  are each in the form of two respective projections. 
     The adjunct material  14106  can be formed from any suitable material or a combination of materials, which are discussed above. In some embodiments, the adjunct material  14106  can have a thickness from about 0.004 inches to about 0.160 inches. In some embodiments, the adjunct material  14106  can have a thickness from about 0.006 inches to about 0.008 inches. The projections  14116   d ,  14116   p  can have a height or thickness from about 0.005 to about 0.010 inches. In some embodiments, the projections, which can be formed from an elastomeric material, can have a height in a range from about 0.005 inches to about 0.015 inches, in a range from about 0.003 inches to about 0.006 inches, or a height that varies in other ranges. However, in some embodiments, the projections  14116   d ,  14116   p  can have a height or thickness up to about 0.180 inches or greater. 
     The locations of the first projections  14116   d  and the second projections  14116   p  formed on the adjunct material  14106  correspond to the locations of the first recesses  14112   d  and the second recesses  14112   p  formed on the cartridge  14102 , respectively. However, in some embodiments, as discussed below, the first distal projections  14116   d  can be closer to one another than the first distal recesses  14112   d , and similarly the second proximal projections  14116   p  can be closer to one another than the second proximal recesses  14112   d . Furthermore, the configuration and size of the projections  14116   d ,  14116   p  corresponds to those of the recesses  14112   d ,  14112   p . In this way, the projections  14116   d ,  14116   p  can be caused to be at least partially received within the recesses  14112   d ,  14112   p , respectively. 
     For example, as shown in  FIG. 111 , the projections  14116   d ,  14116   p  configured to be at least partially received in the recesses  14112   d ,  14112   p  are complementary in shape to the recesses such that the projections  14116   d ,  14116   p  each have a generally circular top cross-section and are generally cylindrical. Furthermore, in the example of  FIG. 111 , the projections  14116   d ,  14116   p  are formed in the adjunct material  14106  such they have an open-end channel extending least partially therethrough that opens on a side  14121  of the adjunct material  14106  opposed to its side facing the cartridge  14102 . For example, the projection  14116   d , which can represent all of the projections formed on the adjunct material  14106 , is shown to have a channel  14119  extending therethrough. The channel  14119  can be formed through the entire projection or through a portion thereof such that a recess can be formed on the side  14121 . Moreover, in some implementations, the projections  14116   d ,  14116   p  formed in the adjunct material  14106  may not have a channel extending at least partially therethrough. 
     As mentioned above, in addition to the adjunct material  14106 , the end effector  14100  of the illustrated implementation includes the polymer attachment layer  14107  used in conjunction with the adjunct material  14106 . In particular, the polymer attachment layer  14107  is disposed between the cartridge  14102  and the adjunct material  14106 , as shown in  FIGS. 111 and 14112 . The polymer attachment layer  14107 , which can be made from a pressure-sensitive adhesive or other suitable material, is used as an attachment or retaining feature. For example, non-limiting examples of materials can include materials described in U.S. Pat. Pub. No. 2016/0278774 entitled “Method of Applying a Buttress to a Surgical Stapler,” filed on Mar. 25, 2015, which is hereby incorporated by reference herein in its entirety. The polymer attachment layer  14107  is configured to hold the adjunct material  14106  in a releasable engagement with the cartridge  14102 . Also, the polymer attachment layer  14107  can provide additional reinforcement to a treatment site. The polymer material  14107  can have a size that is the same or approximately the same to that of the adjunct material  14106  such the entire surface of the adjunct material  14106  is disposed on the polymer material  14107 . The polymer layer may also serve as a reservoir for medicants such as antimicrobials, chemotherapeutic agents, etc. or be radiopaque for imaging purposes. 
     As shown in  FIG. 112 , the polymer attachment layer  14107  includes distal and proximal projections  14117   d ,  14117   p  facing the cartridge  14102 .  FIG. 112  also illustrates that the distal and proximal projections  14117   d ,  14117   p  are formed on the polymer material  14107  at locations corresponding to the locations of the adjunct&#39;s projections  14116   d ,  14116   p , respectively. Thus, the distal projections  14117   d  can be spaced from the proximal projections  14117   p  along a longitudinal axis  14 A 1  of the polymer attachment layer  14107  by the same distance by which the distal projections  14116   d  are spaced from the proximal projections  14116   p . The projections  14117   d ,  14117   p  can be configured similarly to the adjunct&#39;s projections  14116   d ,  14116   p —for example, the projections  14117   d ,  14117   p  can each optionally have an open-end channel extending least partially therethrough (not shown). 
     Also, the distal and proximal projections  14117   d ,  14117   p  of the polymer attachment layer  14107  can have a length or diameter, as measured along the longitudinal axis  14 A 1 , that is similar to that of a length or diameter of the distal and proximal projections  14116   d ,  14116   p  of the adjunct material  14106 . In some embodiments, the polymer attachment layer  14107  can have a thickness from about 0.0005 inches to about 0.001 inches. The projections  14117   d ,  14117   p  can have a height or thickness from about 0.005 to about 0.010 inches. In some embodiments, the projections, which can be formed from an elastomeric material, can have a height in a range from about 0.005 inches to about 0.015 inches, in a range from about 0.003 inches to about 0.006 inches, or a height that varies in other ranges. However, in some embodiments, the projections  14116   d ,  14116   p  can have a height or thickness up to about 0.180 inches or greater. 
     The polymer attachment layer  14107  can be formed from any suitable material such as, for example, polydioxanone (PDO), PLA/PGA copolymers, or any other suitable polymeric material(s), including pressure sensitive adhesive(s). Thus, the adjunct material  14106  can be releasably engaged with the cartridge  14102  via the polymer attachment layer  14107 . The polymer layer&#39;s projections  14117   d ,  14117   p  can be formed from the same material as the rest of the polymer attachment layer  14107 . Also, in some embodiments, the distal and proximal projections  14117   d ,  14117   p  can be formed from a different material than the material forming the polymer attachment layer  14107 . Because the material forming the polymer attachment layer  14107  is biodegradable and/or bioabsorbable, the polymer attachment layer  14107  can be implanted to a treatment site together with the adjunct  14106 . It should be appreciated that, in some embodiments, the polymer attachment layer  14107  may not be present. 
     As mentioned above, the end effector  14100  can be removably coupled with the loading member  14105  having distal and proximal projections  14115   d ,  14115   p  and configured to apply force to the adjunct material  14106  to thereby cause the adjunct material  14106  to mate with the end effector  14100 . In particular, the application of force by the loading member  14105  (and thus by the distal and proximal projections  14115   d ,  14115   p  thereof) to the adjunct material  14106  causes the adjunct material&#39;s projections  14116   d ,  14116   p  to be at least partially received in the recesses  14112   d ,  14112   p  of the cartridge  14102 . Also, in embodiments such as in the example illustrated in which the polymer attachment layer  14107  is disposed between the adjunct material  14106  and the tissue-facing surface  14110  of the cartridge  14102 , the application of force by the loading member  14105  to the adjunct material  14106  and thus to the polymer attachment layer  14107  causes the polymer layer&#39;s projections  14117   d ,  14117   p  to be at least partially received in the recesses  14112   d ,  14112   p  of the cartridge  14102 . Furthermore, the adjunct material&#39;s projections  14116   d ,  14116   p  can be caused to be at least partially received within the polymer layer&#39;s projections  14117   d ,  14117   p , respectively, as discussed below. 
     The distal and proximal projections  14115   d ,  14115   p  of the loading member  14105 , each of which can be in the form of two respective projections, can be configured in a number of different ways. For example, the distal and proximal projections  14115   d ,  14115   p  can have a length (measured along a longitudinal axis  14 A 2  of the loading member  14105 ) that is similar to that of the adjunct material&#39;s projections  14116   d ,  14116   p  and the polymer layer&#39;s projections  14117   d ,  14117   p . The distal and proximal projections  14115   d ,  14115   p  can have an open-end channel extending least partially therethrough and opening on a side of the loading member  14105  facing the anvil  14104 , as shown in  FIG. 111 . However, in some implementations, one or more of the projections  14115   d ,  14115   p  may not include such channel. 
     Also, the distal and proximal projections  14115   d ,  14115   p  of the loading member  14105  can be spaced apart from one another along the longitudinal axis  14 A 2  by approximately the same distance as the adjunct material&#39;s projections  14116   d ,  14116   p  and the polymer layer&#39;s projections  14117   d ,  14117   p . In some embodiments, however, the distal and proximal projections  14115   d ,  14115   p  of the loading member  14105  can be configured and/or formed on the loading member  14105  in a different way. Furthermore, in some implementations, the loading member  14105  may not include the distal and proximal projections  14115   d ,  14115   p , or the loading member  14105  may include only one projection, or other number (e.g., more than two) projections of any suitable configurations. 
     The loading member  14105  can have a variety of different configurations. For example, the loading member  14105  can be in the form of an applicator or retainer that can be removably coupled to the end effector  14100 . For example, in the illustrated implementation, as shown in  FIGS. 111 and 112 , the member  14105  is an elongate, generally rectangular component having a length and width generally corresponding to the length and width of the tissue-contacting surface of the cartridge  14102 . The member  14105  also has a distal tongue portion  14120  in the form of a downward bent and a generally flat portion extending distally from the bend. The distal tongue portion  14120  can facilitate grip and can serve as a lever. In use, the surgeon can hold the distal tongue portion  14120  and apply force thereto in the direction towards the tissue-facing surface  14110  of the cartridge  14102  to thereby cause the member  14105  to apply load to the adjunct material  14106 . The distal tongue portion  14120  can be grasped and moved (e.g., moved away from the cartridge body  14102 ) to remove the loading member  14105  from the end effector  14100 . 
     Additionally or alternatively, the loading member  14105  can be “preloaded,” or releasably coupled with, the adjunct material  14106  and the polymer attachment layer  14107  in a suitable manner. When force is applied to the adjunct material  14106 , either by operating the loading member  14105 , or when the loading member  14105  is clamped between the cartridge and anvil  14102 ,  14104 , the adjunct material  14106 , and the polymer attachment layer  14107  (if present) are transferred to the cartridge  14102 . The loading member  14105  can then be removed from the end effector  14100 . 
     The loading member  14105  can be coupled to the end effector  14100  in many different ways. In the illustrated example, the loading member  14105  is coupled to the proximal end  14102   p  of the cartridge  14102  using one or more suitable features. For example, the loading member  14105  can have at a proximal end  14105   p  thereof a tab  14118  ( FIG. 112 ) configured to engage the proximal end  14102   p  of the cartridge body  14102 . It should be appreciated, however, that any other suitable feature(s) can be used to removably couple the member  14105  to the cartridge body  14102 . Furthermore, in some implementations, the loading member  14105  may not be coupled to the end effector  14100 —e.g., as discussed above it can be clamped between the end effector&#39;s jaws to thereby cause the adjunct material  14106  (and the polymer attachment layer  14107 , if present) to be transferred to the cartridge  14102 . 
     In some embodiments, the adjunct material  14106  and the polymer attachment layer  14107  can be coupled to the loading member  14105  in a suitable manner before the adjunct material  14106  and the polymer attachment layer  14107  are delivered to the cartridge body  14102 . Regardless of its configuration and the way in which it is used to cause the adjunct material to be releasably retained on a jaw of an end effector (e.g., the cartridge  14102 ), the loading member  14105  is configured to evenly apply force to the surface of the adjunct material  14106  such that the adjunct material  14106  becomes attached to the jaw. 
     In some embodiments, as mentioned above, projections of the adjunct material can be at least partially received within the projections the polymer layer.  FIGS. 113A and 113B  demonstrate such an example where first and second projections  14216   a ,  14216   b  of an adjunct material  14206  are at least partially received within first and second projections  14217   a ,  14217   b  of a polymer layer  14207 . The adjunct material  14206  and the polymer layer  14207  can be similar, for example, to the adjunct material and polymer layer  14106 ,  14107  ( FIGS. 111 and 112 ), respectively. It should be appreciated that. while  FIGS. 111 and 112  illustrate the adjunct material&#39;s and polymer layer&#39;s distal and proximal projections,  FIGS. 113A and 113C  show, by way of example, only respective pairs of distal projections formed on the adjunct material  14206  and the polymer layer  14207 . Thus, for example, the first and second projections  14216   a ,  14216   b  of the adjunct material  14206  can be similar to the at least one distal projection  14116   d  of the adjunct material  14106  in  FIG. 112 . It should be appreciated that the adjunct material  14206  and the polymer layer  14207  can also have respective proximal projections, similar, for example, to the at least one proximal projection  14116   p  and at least one proximal projection  14117   p  ( FIG. 112 ), respectively. 
     As shown in  FIG. 113A , the first and second projections  14216   a ,  14216   b  of the adjunct material  14206  extend from the top into the first and second projections  14217   a ,  14217   b  of the polymer layer  14207 . The adjunct material  14206  and the polymer layer  14207  can be mated in this way in a number of different ways. For example, the adjunct material  14206  can be preloaded with the polymer layer  14207 . Alternatively, the projections of the adjunct material  14206  can be mated with the projections of the polymer layer  14207  using the loading member or other component(s) configured to apply force to the adjunct material. 
     Regardless of the way in which the adjunct material  14206  is mated with the polymer layer  14207  so as to result in the structure as shown in  FIG. 113A , such adjunct material/polymer layer structure can be caused (e.g., using the loading member  14105  or another suitable component) to be engaged with the jaw of an end effector. For example,  FIG. 113B  illustrates that force can be applied (shown by arrow  14210 ) to the adjunct material  14206  mated with the polymer layer  14207  to cause the first and second projections  14217   a ,  14217   b  of polymer layer  14207  (and thus the first and second projections  14216   a ,  14216   b  of the adjunct material  14206  mated therewith) to be engaged with corresponding first and second recesses  14212   a ,  14212   b  formed in a jaw  14202 . The jaw  14202  can be a cartridge body (e.g., cartridge body  14102  in  FIGS. 111 and 112 ). However, the jaw  14202  can also be an anvil, as the described techniques can be used to releasably retain an adjunct material on an anvil of the end effector as well. 
     A distance between the first and second recesses  14212   a ,  14212   b  formed in the jaw  14202  can be greater than a distance between the first and second projections  14217   a ,  14217   b  of polymer layer  14207  (and thus between the first and second projections  14216   a ,  14216   b  of the adjunct material  14206 ), prior to mating the polymer layer  14207  and the adjunct material  14206  with the jaw  14202 . As a result of the force applied to the adjunct material  14206  mated with the polymer layer  14207 , a distance between the first and second projections  14217   a ,  14217   b  (and thus between the first and second projections  14216   a ,  14216   b ) can increase, as shown in  FIG. 113A  by arrows  14211 . In this way, as the force is applied to the adjunct material  14216  and its thickness thus decreases, the projections of the polymer layer  14207  and of the adjunct material  14206  “find” the first and second recesses  14212   a ,  14212   b  formed in the jaw  14202  to thereby releasably mate the adjunct material  14206  with the jaw  14202 . 
     Projections formed on an adjunct material in accordance with the described embodiments can have various configurations. For example, in some embodiments, the projections can be longitudinal projections formed on opposed sides of the adjunct material. The longitudinal projections formed on the adjunct material can be configured to be mated with complementary features (e.g., recesses) formed on a jaw of an end effector. 
       FIGS. 114-116  illustrate an embodiment of an end effector  14300  having a cartridge  14302  and an anvil  14304 , at least one of which can be configured to be releasably mated with an adjunct material having longitudinal projections. As shown in  FIG. 114 , the cartridge  14302  has a plurality of staple cavities  14308  configured to seat staples therein, the staple cavities formed on a tissue-facing surface  14310  of the cartridge  14302 . The anvil  14304  of the end effector  14300 , shown in  FIG. 116 , has a plurality of staple forming cavities (not shown) formed on a tissue-facing surface  14314  thereof. 
     In the illustrated implementation, the end effector  14300  can have an adjunct material releasably retained on one or both of the jaws  14302 ,  14304 . Thus, as shown in  FIG. 114 , an adjunct material  14306  can be releasably mated with the cartridge  14302 . The adjunct material  14306  has a first longitudinal projection  14316   a  formed on one side  14315   a  of the adjunct material  14306  and a second longitudinal projection  14316   b  formed on another, opposite side  14315   b  of the adjunct material  14306 . As shown, the first and second longitudinal projections  14316   a ,  14316   b  extend between distal and proximal ends  14306   d ,  14306   p  of the adjunct material  14306 . 
     The first and second longitudinal projections  14316   a ,  14316   b  of the adjunct material  14306  are configured to mate with respective first and second complementary recesses  14312   a ,  14312   b  formed in the tissue-facing surface  14310  of the cartridge  14302 . As shown in  FIG. 114 , the first and second longitudinal recesses  14312   a ,  14312   b  extend along a longitudinal axis  14 A 3  of the cartridge  14302 , are formed on opposed sides of a cutting element channel  14313 , and are each adjacent to opposed sides  14311   a ,  14311   b  of the tissue-facing surface  14310 . 
     The longitudinal projections  14316   a ,  14316   b  formed on the adjunct material  14306  can have a number of different configurations. For example, the first and second longitudinal projections  14316   a ,  14316   b  of the adjunct material  14306  have mating features  14318   a ,  14318   b  formed thereon that are configured to be at received within the corresponding recesses  14312   a ,  14312   b . In this example, the mating features  14318   a ,  14318   b  are in the form of arrows facing towards the recesses  14312   a ,  14312   b  formed in the cartridge  14302 . 
     The longitudinal projections  14316   a ,  14316   b  can be formed from at least partially flexible and/or deformable material such that, as the projections  14316   a ,  14316   b  are received within the corresponding recesses  14312   a ,  14312   b , the projections  14316   a ,  14316   b  contract to fit into the recesses and, once in the recesses, expand to be fittingly received within the recesses. Thus, the arrow-shaped mating features  14318   a ,  14318   b  extending from the adjunct material&#39;s longitudinal projections  14316   a ,  14316   b  can have a width that is greater than that of the respective recesses  14312   a ,  14312   b . When the mating features  14318   a ,  14318   b  are forced into the recesses  14312   a ,  14312   b , they can first be caused to contract as they are forced into the recesses, where they then expand to be releasably retained therein. It should be appreciated that the arrow-shaped mating features  14318   a ,  14318   b  are shown by way of example only, and the mating features formed on the projections can have any suitable configuration. For example, the mating features can be C-shaped, J-shaped, or they can have any other configuration(s), including different configurations. 
     As shown in  FIG. 116 , an adjunct material  14320  configured to be releasably retained on the anvil  14304  can have first and second longitudinal projections  14322   a ,  14322   b , which can be similar to the longitudinal projections  14316   a ,  14316   b  formed on the adjunct material  14306  configured to be releasably retained on the cartridge  14302 . For example, similar to the cartridge  14302 , the anvil  14304  can have longitudinal recesses formed therein that are configured to receive therein the longitudinal projections  14322   a ,  14322   b.    
     One or both of the adjunct materials  14306 ,  14320  can be releasably retained on the jaws  14302 ,  14304 , respectively, using an applicator member  14305  shown in  FIG. 115 . The applicator member  14305  can be in the form of a frame-like holder configured to releasably retain one or both of the adjunct materials  14306 ,  14320 . In the illustrated example, the applicator member  14305  is in the form of first (e.g., bottom) and second (e.g., top) generally rectangular housings  14324 ,  14326  coupled to one another as shown in  FIG. 115 . As also shown in  FIG. 115 , the first and second housing  14324 ,  14326  can encompass edges of the long sides of the adjunct materials  14306 ,  14320  disposed within the applicator member  14305 . In other words, the applicator member  14305  can be in the shape of a generally rectangular frame following an outer perimeter of at least two sides (e.g., long sides) of one or two adjunct materials. In particular, as shown in  FIG. 115 , the applicator member  14305  encompasses at least in part the portions of the adjunct materials  14306 ,  14320  having first and second longitudinal projections  14316   a ,  14316   b , and  14322   a ,  14322   b , respectively, extending therefrom. The rest of the surface area of the adjunct materials  14306 ,  14320  may be not encompassed by the applicator member  14305 , as shown in  FIG. 115 . The adjunct material  14320  to be retained on the anvil is disposed over the adjunct material  14306  to be retained on the cartridge. It should be appreciated that the adjunct materials  14306 ,  14320  and the first and second housings  14324 ,  14326  of the applicator member  14305  encompassing them can be symmetrical. Thus, either of the adjunct materials  14306 ,  14320  can be applied to the anvil or the cartridge. 
     The applicator member  14305  can be formed from any suitable material (e.g., plastic), and its walls can be relatively thin and it can be disposable. In use, to transfer the adjunct materials  14306 ,  14320  to the cartridge and anvil  14302 ,  14304 , respectively, the cartridge and anvil  14302 ,  14304  can be clamped over the applicator member  14305 . In this way, force applied by the jaws  14302 ,  14304  causes the adjunct materials  14306 ,  14320  to separate from the applicator member  14305  and to be engaged with the jaws  14302 ,  14304 . In particular, in this example, as force is applied to the applicator member  14305  by the jaws  14302 ,  14304  of the end effector  14300 , the longitudinal projections  14316   a ,  14316   b  formed in the adjunct material  14306  mate with the recesses  14312   a ,  14312   b  in the cartridge  14302 , and, similarly, the longitudinal projections  14322   a ,  14322   b  formed in the adjunct material  14320  mate with the complementary recesses (not shown) in the anvil  14304 . 
     After the adjunct materials  14306 ,  14320  are transferred to the cartridge and anvil  14302 ,  14304 , the cartridge and anvil  14302 ,  14304  can be opened and the applicator member  14305  can be separated from the end effector  14300 . The end effector  14300  having its cartridge and anvil  14302 ,  14304  thus mated with the adjunct materials  14306 ,  14320 , as shown in  FIG. 116 , can then be used as desired in a surgical procedure. 
     It should be appreciated that the applicator member  14305  is shown to releasably retain both of the adjunct materials  14306 ,  14320  by way of example only, as the applicator member  14305  or a similar component configured to releasably hold at least one adjunct material can be used to transfer an adjunct material only to an end effector&#39;s anvil or an end effector&#39;s cartridge. 
     In some embodiments, at least one projection formed on the adjunct material can be in the form of a plurality of discrete projections formed from an at least partially flowable or bendable material that has a changeable configuration. When a suitable applicator applies force to the adjunct material to cause each of the discrete projections to be at least partially received within a corresponding recess in a jaw of an end effector, the configuration of each of the discrete projections that is at least partially received within the corresponding recess changes to conform to a configuration of the corresponding recess. The discrete projections are configured to separate from the adjunct material and remain within the recesses in the jaw after the staples are formed against the staple forming cavities to apply the adjunct material to a tissue clamped between the end effector&#39;s jaws. 
       FIGS. 117-119  illustrate anther embodiment of an end effector  14400  having a cartridge  14402  and an anvil  14404 , at least one of which can have an adjunct material releasably retained thereon that is has projections made from an at least partially flowable material. The projections can also be formed from at least partially bendable, free-flowing, or waxy materials. In other words, the material from which the projections are formed can be deformable in various ways. For example, they can be made from polymers/elastomers may deform or bend and still retain memory of their original shape. 
     In this example, as shown in  FIG. 117 , both the cartridge  14402  and the anvil  14404  can have respective adjunct materials  14406 ,  14420  to be releasably retained thereon. As shown in  FIG. 117 , the adjunct material  14406  releasably retained on a tissue-facing surface  14410  of the cartridge  14402  has a plurality of discrete projections  14416  configured to be releasably mated with recesses  14412  formed in the tissue-facing surface  14510 . As shown in  FIG. 117 , the discrete projections  14416  are formed along a longitudinal axis  14 A 4  of the adjunct  14406 . It should be appreciated that the projections  14416  and recesses  14412  do not need to be evenly spaced and, in some embodiments, they can be disposed at varied distances from one another. The locations and number of the projections  14416  and recesses  14412  can be selected based on a desired manner of attaching the adjunct material to the end effector&#39;s jaw. Accordingly, the seven evenly spaced projections  14416  are shown in  FIG. 117  by way of example only, as suitable number of projections can be formed, and the projections can be formed asymmetrically and unevenly spaced with respect to one another. 
     The adjunct material  14420  releasably retained on a tissue-facing surface  14411  of the anvil  14402  also has a plurality of discrete projections  14421  configured to be releasably mated with recesses  14434  formed in the tissue-facing surface  14411 . It should be appreciated that each of the discrete projections  14416 ,  14421  can be formed such that it spans the entirety of, or only a portion of, the width of the respective jaw. Also, in some implementations, each of the discrete projections  14416 ,  14421  can be in the form of two projections formed on opposed sides of the tissue-facing surface of the jaw, although only one of such projections is shown in  FIG. 117 . 
     In this example, the discrete projections  14416  formed on the adjunct material  14406  and the discrete projections  14421  formed on the adjunct material  14420  have a generally rectangular shape, as shown in  FIG. 117  (where the projections of the anvil&#39;s adjunct material  14420  are shown partially separated from the anvil  14404 ). The discrete projections  14416 ,  14421  can be formed from an at least partially flowable material and can have a changeable configuration such that, when each of the discrete projections is at least partially received within a corresponding recess in the jaw, the configuration of each discrete projection changes to conform to a configuration of the corresponding recess. The at least partially flowable material can be any suitable material or a combination of materials. Examples of the materials can include a suitable polymeric material, elastomeric material (e.g., silicone), wax, and any other material(s). For example, collagen, gelatin hyaluronic acid, sodium alginate, or any other hydrogels can be used. Also, non-limiting examples of materials can include materials described in U.S. Pat. Pub. No. 2016/0278774 entitled “Method of Applying a Buttress to a Surgical Stapler,” filed on Mar. 25, 2015, which is hereby incorporated by reference herein in its entirety. 
     In some embodiments, a more rigid polymer/elastomer can be used that can be perforated/slitted at the end, such that it frays outward into a T-slot pocket, rather than deforming in bulk, which would require a material with very low shear-resistance. In some embodiments, a material from which the adjunct is formed can be used to fill out the recess on its own. This may be possible with non-woven fabrics having fibers that areable to slide/shear relative to each other. 
     Accordingly, in the illustrated implementation, each of the generally rectangular projections  14421  formed on the adjunct material  14420  to be releasably retained on the anvil  14404 , “flows” into, or conforms, to the configuration of each of the recesses  14434 , as shown in  FIG. 117 . As also shown in  FIG. 117 , the projections  14416  of the adjunct  14406  (which can also be generally rectangular projections) “flow” into the T-shaped recesses  14412  formed in the cartridge  14402  to thus conform to the shape of the recesses  14412 . 
     The adjunct materials  14406 ,  14420  can be transferred to the cartridge and anvil  14402 ,  14404  using an applicator member  14405  shown in  FIG. 119 , which can be similar to applicator member  14305  ( FIG. 115 ). Thus, as shown in  FIG. 119 , the applicator member  14405  can be a frame-like holder having first and second portions  14424 ,  14426  releasably holding the adjunct materials  14406 ,  14420 . To transfer the adjunct materials  14406 ,  14420  from the applicator member  14405  to the end effector  14400 , the jaws  14402 ,  14404  can be clamped upon the applicator member  14405 , which causes the adjunct materials  14406 ,  14420  to be mated with the cartridge and anvil  14402 ,  14404 , respectively. In particular, as discussed above, the projections, on the adjunct materials  14406 ,  14420  are received in the recesses  14412 ,  14434  in the cartridge and anvil  14402 ,  14404  so that the projections (which are formed from at least partially flowable material) change their configuration to fill in the recesses and thus adopt the shape of the recesses. Similar to the applicator member  14305  ( FIG. 115 ), after the applicator member  14405  is used to transfer the adjunct materials  14406 ,  14420  to the end effector&#39;s jaws, the applicator member  14405  can be separated from the end effector  14400 . 
     During a surgical procedure, as shown in  FIG. 118 , a tissue  14 T is clamped between the cartridge  14402  and anvil  14404  of the end effector  14400  and staples  14409  are formed against the staple forming cavities of the anvil  14404 . The ejection of the staples from the staple-holding cavities opening on the tissue-facing surface  14410  of the cartridge  14402  causes the adjunct materials  14406 ,  14420  to be released from engagement with the cartridge  14402  and anvil  14404  and to be applied to opposed sides of the tissue  14 T, as also shown in  FIG. 118 . As further shown in  FIG. 118 , the discrete projections  14416 ,  14421  separate from the adjunct materials  14406 ,  14420  applied to the tissue  14 T and remain within the recesses  14412 ,  14434 , respectively. Such embodiments can be employed in implementations where, for example, the end effector  14400  is part of a disposable loading unit configured to be coupled distally to a surgical tool and that is configured to be disposed after use. 
     In some embodiments, an adjunct material configured to be releasably retained on a jaw of an end effector can be formed from at least partially expandable or stretchable material and/or in the form of a film. The jaw, such as an anvil or a cartridge, can have one or more recesses formed therein that are configured to receive portions of the adjunct material. An applicator member, such as, e.g., loading member  14305  in  FIG. 115 , applicator member  14405  in  FIG. 119 , or a member having any other configuration that has projections formed thereon, can be used to mate the adjunct material with the jaw. For example, when the applicator member is used to apply force to the adjunct material, the projections formed on the applicator member cause portions of the adjunct material to be releasably received within the one or more recesses formed in the jaw. 
       FIGS. 120-122  illustrate one example of an implementation of an adjunct material  14506  configured to be mated with a jaw  14500  of an end effector of a surgical instrument. In this example, the jaw  14500  is shown generally as a jaw that can be either a cartridge or an anvil. Regardless of its particular configuration, the jaw  14500  can have recesses  14503  formed in a tissue-facing surface  14510  thereof. It should be appreciated that the recesses  14503  can be formed at any locations within tissue-facing surface  14510 . Also, the six recesses  14503  are shown in  FIG. 120  for illustrating purposes only, as any suitable number of recesses  14503  (e.g., less than six or greater than six) can be formed on the jaw. Also, the recesses  14503  do not need to be evenly spaced and, in some embodiments, they can be disposed at varied distances from one another. The locations and number of the recesses  14503  can be selected based on a desired manner of attaching the adjunct material to the end effector&#39;s jaw. 
     For example, the recesses  14503  can be formed in the area of the tissue-facing surface  14510  occupied by staple-forming cavities (if the jaw  14500  is an anvil) or by staple-holding cavities or pockets (if the jaw  14500  is a cartridge). As another example, one or more of the recesses  14503  can be formed in area(s) of the tissue-facing surface  14510  that does not have the staple-forming cavities or the staple-holding pockets. For example, in one embodiment, one or more recesses can be formed at a distal end of the jaw  14500  outside of the area having the staple-forming cavities or the staple-holding pockets, and one or more recesses can be formed at a proximal end of the jaw  14500  outside of the area having the staple-forming cavities or the staple-holding pockets. Furthermore, in some implementations, one or more of the recesses  14503  can be the staple-forming cavities or the staple-holding pockets. 
     The recesses  14503  are shown by way of example only as having a generally circular cross-section. However, the recesses  14503  can have other suitable shapes, as the described embodiments are not limited in this respect. One or more of the recesses  14503  can have features that facilitate their ability to retain a portion of the adjunct material therein. For example, as shown in  FIG. 121 , the recess  14503  can have retaining features  14512   a ,  14512   b  that can be in the form of hooks, teeth, rings, barbs, or retaining elements having any other configuration. It should be appreciated that one or more of the retaining features can be formed, or the recesses  14503  can be free of any additional features. 
     Regardless of the way in which the recesses  14503  are formed in the jaw  14500 , each recess (e.g., the recess  14503  shown in  FIG. 121 ) is configured to receive therein a corresponding projection or post  14515  formed on an applicator member  14505 . The applicator member  14505 , having one or more posts (one of which is shown in  FIGS. 121 and 122 ), can have any suitable configuration that enables force to be applied by the applicator member  14505  to the adjunct material  14506 . As mentioned above, the adjunct material  14506  can be formed from an at least partially stretchable material. Thus, as shown in  FIG. 122 , when force is applied by or to the applicator member  14505  (as shown by arrow  14511 ), the applicator member  14505  is brought in proximity to the tissue-facing surface  14510  such that the post  14515  is at least partially received within the recess  14503 . As a result, the post  14515  pushes a portion  14508  of the adjunct material  14506  into the recess  14503 , as also shown in  FIG. 122 . In this example, the retaining features  14512   a ,  14512   b  extending from the inner walls of the recess  14503  facilitate retention of the portion  14508  of the adjunct material  14506  within the recess  14503 . 
     Other recesses formed in the jaw  14500  can similarly receive at least partially therein posts formed on the applicator member  14505  that thus push portions of the adjunct material  14506  into the recesses. In this way, the adjunct material  14506  becomes releasably mated with the jaw  14500 . 
     The number and locations of the posts, such as the post  14515 , formed on the applicator member  14505  can correspond to those of the recesses  14503  in the jaw  14500 . Thus, each of the recesses  14503  can receive therein a portion of the adjunct material pushed into the recess using a corresponding post. In other implementations, however, only some of the recesses can receive corresponding posts therein. 
     The post  14515 , representing just one example of the multiple posts that can extend from the applicator member  14505 , is shown as a generally cylindrical element by way of example only, as the post  14515  can have other configurations. For example, the post  14515  can be mushroom-shaped (e.g., shaped as a “reversed mushroom”) or it can have a generally rectangular, square, or otherwise shaped cross-section. The size of the post  14515  can be selected such that it fits with clearance within the recess  14503  and pushes the portion  14508  of the adjunct material  14506  into the recess  14503  in a manner that allows retaining that portion  14508  in the recess  14503 , as shown in  FIG. 122 . The portion  14508  can be retained in the recess  14503  using the retaining features  14512   a ,  14512   b  as shown in  FIGS. 121 and 122 , or any other type(s) of retaining features. 
     After the adjunct material  14506  is mated with the jaw  14500  using the applicator member  14505 , the applicator member  14505  is removed, whereas the adjunct material portion  14508  remains in the recess  14503 . When the adjunct material  14506  is separated from the jaw  14500  to be transferred to a tissue at a treatment site (e.g., when staples are ejected from the jaw&#39;s cartridge), the adjunct material portion  14508  is caused to exit the recess  14503 . 
     In the illustrated example, the adjunct material  14506 , which can be in the form or a film and/or at least partially stretchable member, can be generally rectangular or it can have other configurations. The size of the adjunct material  14506  can be such that, when its portions (e.g., the portion  14508  in  FIGS. 121 and 122 ) are mated with the jaw  14500 , the adjunct material  14506  still covers a desired area of the tissue-facing surface  14510  of the jaw  14500 . In other words, the adjunct material  14506  can be oversized relative to a size of the tissue-facing surface  14510  of the jaw  14500 . Also, even though some extra material becomes available after the adjunct material&#39;s portions are released from the recesses in the jaw, this does not affect the ability of the adjunct material  14506  to reinforce and/or treat a site in a patient&#39;s body. 
     In some embodiments, an adjunct material can be releasably retained on a jaw of an end effector using a material that can change its configuration when heat is applied thereto.  FIGS. 123 and 124  illustrate an embodiment of an end effector  14600  having a cartridge body  14602  and an anvil  14604 , which can have an adjunct material  14606  configured to be retained on at least one of the cartridge body and anvil  14602 ,  14604  using an attachment layer  14607 . In particular, in the example illustrated, the attachment layer  14607  can be used to couple the adjunct material  14606  to the cartridge body  14602 , as discussed in more detail below. 
     As shown in  FIG. 123 , a tissue-facing surface  14610  of the cartridge body  14602  can have recesses  14612   a ,  14612   b  disposed outside of the area of the cartridge body  14602  having staple-holding pockets  14608 . The two recesses  14612   a ,  14612   b  formed at a distal end  14602   d  of the cartridge body  14602  are shown, and a proximal end  14602   p  of the cartridge body  14602  can have a similar pair of recesses. The recesses  14612   a ,  14612   b  are disposed at opposed sides of a cutting-element channel  14613  in the cartridge body  14602 , though the recesses  14612   a ,  14612   b  can be disposed at other areas of the tissue-facing surface  14610  of the cartridge body  14602 . 
     As shown in  FIG. 123 , the adjunct material  14606  can have retaining features  14616   a ,  14616   b  formed at a distal end  14606   d  thereof, and similar retaining features  14616   c ,  14616   d  formed at a proximal end  14606   p  thereof. In the illustrated implementation, the retaining features  14616   a ,  14616   b ,  14616   c ,  14616   d  are in the form of cupcake-like depressions in the adjunct material  14606  extending towards the cartridge body  14602  and opening on a side of the adjunct material  14606  opposite to its side facing the cartridge body  14602 . It should be appreciated, however, that the retaining features  14616   a ,  14616   b ,  14616   c ,  14616   d  can have any other shapes, and that the number of the retaining features can be different from four (e.g., less than four or greater than four). Furthermore, as in the example illustrated, the retaining features  14616   a ,  14616   b ,  14616   c ,  14616   d  can be formed as closed depressions in the adjunct material  14606 , or they can be open-ended features opening into the cartridge&#39;s recesses when the adjunct is mated therewith. 
     The distal retaining features  14616   a ,  14616   b  are configured to be received within the distal recesses  14612   a ,  14612   b  in the cartridge body  14602 . In a similar manner, the proximal retaining features  14616   c ,  14616   d  of the adjunct material  14606  are configured to be received within the proximal recesses formed in the cartridge body  14602 , which are obscured in  FIG. 123 . 
     The attachment layer  14607 , which can be formed from a suitable heat meltable material, can be used to attach the adjunct material  14606  to the cartridge body  14602 . For example, to releasably attach the adjunct material  14606  to the cartridge body  14602 , the adjunct material  14606 , which can have the attachment layer  14607  coupled thereto in a suitable manner, can be disposed on the tissue-facing surface  14610  of the cartridge body  14602 . The attachment layer  14607  can be coupled to the adjunct material  14606  or it can be disposed over the adjunct material  14606  such that the adjunct material  14606  is located between the tissue-facing surface  14610  of the cartridge body  14602  and the attachment layer  14607 . Regardless of the way in which the attachment layer  14607  is associated with the adjunct material  14606 , the adjunct material  14606  is disposed over the cartridge body  14602  such that the retaining features  14616   a ,  14616   b ,  14616   c ,  14616   d  are received within the respective recesses formed in the cartridge body  14602 . For example, the retaining features  14616   a ,  14616   b  are received within the recesses  14612   a ,  14612   b.    
     A suitable device can then be used to apply heat to the attachment layer  14607  such that at least some of its portions melt and the attachment layer&#39;s material flows into the retaining features  14616   a ,  14616   b ,  14616   c ,  14616   d  in the adjunct material  14606  that, in turn, at least partially seat within respective recesses formed in the cartridge body  14602 . In this way, the material of the attachment layer  14607  deposited within each of the retaining features  14616   a ,  14616   b ,  14616   c ,  14616   d  of the adjunct material  14606  mates the adjunct material  14606  with the cartridge body  14602 .  FIG. 124  illustrates by way of example a recess  14612 ′ in the cartridge body  14602 , which can be representative of any of the recesses (e.g.,  14612   a ,  14612   b  or others) that can be formed in the cartridge body  14602 . As shown in  FIG. 124 , the recess  14612 ′ can seat therein a respective retaining feature  14616 ′ (e.g., any of the retaining features  14616   a ,  14616   b ,  14616   c ,  14616   d ) that in turn, is lined with the material of the attachment layer  14607 . 
     The attachment layer  14607  can be formed from any suitable bioabsorbable and/or biodegradable material. Non-limiting examples of the material include polydioxanone (PDO), lactide/glycolide copolymers, poly-L-lactide, poly-L-lactide-co-D,L-lactide, poly-L-lactide-co-glycolide, poly-4-hydroxybutrate, polycaprolactone, poly lactide-co-glycolide), Poly-L-lactide. Exemplary materials are also disclosed in U.S. patent application Ser. No. 14/871,195, entitled “Compressible Adjunct Assemblies with Attachment Layers” and Ser. No. 14/871,087, entitled “Implantable Adjunct Comprising Bonded Layers.” 
     Heat of a suitable temperature such as, for example, between 80 C° and 120 C°, can be applied to the end effector  14600  in any of various ways. Though, other ranges can be used as well, including higher temperatures. For example, a suitable heater device (e.g., an infrared (IR) heater, ultraviolet (UV) heater, resistive heater, etc.) can be used. 
     In some implementations, the adjunct material  14606  and the attachment layer  14607  can be coupled to the jaw of the end effector  14600 , such as the cartridge body  14602 , using an applicator member (not shown) configured to apply the adjunct material  14606  with the attachment layer  14607  to an end effector&#39;s jaw. The applicator member can be similar, e.g., to the applicator member  14305  ( FIG. 115 ), but can also be equipped with a heating element (e.g., a resistive wire element, UV element, IR element, etc.). Similar to the applicator member  14305 , the heat-applying applicator member can releasably hold the adjunct material  14606  and the attachment layer  14607 . Regardless of the specific way in which the applicator member is configured to generate heat, in use, the applicator member can be clamped between the jaws  14602 ,  14604  of the end effector  14600  and activated to generate heat to thus melt at least portions of the attachment layer  14607 . After the attachment layer  14607  is received within the retaining features of the adjunct material  14606  (e.g., as shown in  FIG. 124 ), the jaws  14602 ,  14604  can be open and the applicator member can be separated from the end effector  14600  while leaving the adjunct material  14606  and the attachment layer  14607  mated with the end effector  14600  (in this example, with the cartridge body  14602 ). 
     It should be appreciated that, additionally or alternatively, an adjunct material can be configured to be releasably mated with an anvil in a manner similar to that shown in  FIGS. 123 and 124 . 
     In the embodiments described herein, an adjunct material for use with an end effector of a surgical instrument is provided that has at least one projection configured to mate with a corresponding at least one recess formed in the end effector. However, in other embodiments, an adjunct material can be releasably retained on a jaw of an end effector using recesses formed in the adjunct material that are configured to mate with corresponding projections formed on the jaw. 
       FIGS. 125-127  illustrate an embodiment of an end effector  14700  having a cartridge  14702  and an anvil  14704 , at least one of which can be configured to be releasably mated with an adjunct material having longitudinal channels or recesses. In this embodiment, the end effector  14700  has a cartridge  14702  and an anvil  14704  having any suitable configurations, at least one of which can be configured to be releasably mated with an adjunct material having longitudinal recesses. For example, as shown, the end effector  14700  can have adjunct materials releasably retained on both of the jaws  14702 ,  14704 . Thus, as shown in  FIG. 125 , an adjunct material  14706  can be releasably mated with the cartridge  14702 . The adjunct material  14706  has a first longitudinal recess  14717   a  formed on one side of the adjunct material  14706  and a second longitudinal recess  14717   b  formed on another, opposite side of the adjunct material  14706 . As shown, the first and second longitudinal recesses  14717   a ,  14717  extend between distal and proximal ends  14706   d ,  14 ′ 706   p  of the adjunct material  14706 . 
     The first and second longitudinal recesses  14717   a ,  14717   b  of the adjunct material  14706  are configured to mate with respective first and second complementary projections  14715   a ,  14715   b  formed on a tissue-facing surface  14710  of the cartridge  14702 . The projections  14715   a ,  14715   b  can have mating features  14718   a ,  14718   b  formed thereon that are configured to mate with the corresponding recesses  14717   a ,  14717   b  in the adjunct material  14706 . In this example, the mating features  14718   a ,  14718   b  are in the form of arrows facing towards the adjunct material  14706 , as shown in  FIGS. 125-127 . It should be appreciated that the arrow-shaped mating features  14318   a ,  14318   b  are shown by way of example only, and the mating features formed on the projections can have any suitable configuration. For example, the mating features can be C-shaped, J-shaped, or they can have any other configuration(s), including different configurations. 
     The longitudinal recesses  14717   a ,  14717   b  formed in the adjunct material  14706  can have a number of different configurations. For example, the first and second longitudinal recesses  14717   a ,  14717   b  can have a shape that is complementary to that of the first and second projections  14715   a ,  14715   b . In this way, as in the example illustrated, at least a portion of each of the first and second longitudinal recesses  14717   a ,  14717   b  can be arrow-shaped. However, the recesses  14717   a ,  14717   b  can have any other suitable configuration(s). 
     The longitudinal projections  14715   a ,  14715   b  can be formed from at least partially flexible and/or deformable material such that, as the projections  14715   a ,  14715   b  are received within the corresponding recesses  14717   a ,  14717   b  in the adjunct material  14706 , the projections  14715   a ,  14715   b  are contracted to fit into the recesses and, once in the recesses, are then expanded to be fittingly received within the recesses. 
     As shown in  FIG. 127 , an adjunct material  14720  configured to be releasably retained on the anvil  14704  can also have first and second longitudinal recesses  14723   a ,  14723   b , which can similar to the longitudinal recesses  14717   a ,  14717   b  formed on the adjunct material  14706  configured to be releasably retained on the cartridge  14702 . For example, similar to the cartridge  14702 , the anvil  14704  can have longitudinal projections formed therein that are configured to be received within the longitudinal recesses  14723   a ,  14723   b . Similar to the example shown in  FIGS. 114-116 , one or both of the adjunct materials  14706 ,  14720  can be releasably retained on the jaws  14702 ,  14704 , respectively, using an applicator member  14705  shown in  FIG. 126 . The applicator member  14705 , which can releasably retain therein the adjunct materials  14706 ,  14720 , can be similar to the applicator member  14305  ( FIG. 115 ) and is therefore not described in detail herein. 
     It should be appreciated that the adjunct materials described herein can include one or more medicants which can be releasably incorporated into or associated with adjuncts in many different ways. Also, the adjunct materials can have various other features in addition to the features described herein. 
     Methods and Devices for Delivering and Securing Adjunct Materials to a Treatment Site 
       FIG. 128A  illustrates one embodiment for depositing a flowable adjunct precursor  15500  upon a surface of a tissue  15502  by an applicator  15504 . As shown, the applicator  15504  is positioned adjacent to the tissue  15502  and activated to cause the adjunct precursor  15500  to flow from the applicator  15504  to the tissue  15502  for deposition at the treatment site. The viscosity of the adjunct precursor  15500  can be low enough to facilitate flow from the applicator  15504  to the tissue  15502  and high enough to inhibit substantial flow once deposited upon the tissue  15502 . Additionally, the rheology of the adjunct precursor  15500  can be selected to provide a shear thinning effect. As an example, the adjunct precursor  15500  can exhibit a lower viscosity during application due the shear generated and exhibit a relatively higher viscosity once applied due to the near absence of shear. 
     The adjunct precursor  15500  can be applied to one or more surfaces of the tissue  15502 . In one aspect, the adjunct precursor  15500  can be applied to opposed surfaces of the tissue  15502  at approximately the same location. In another aspect, not shown, the adjunct precursor  15500  can be applied to a first surface of the tissue  15502  and a solid adjunct, different from the adjunct precursor  15500 , can be applied to a second surface of the tissue  15502  opposite the first surface of the tissue  15502 . 
     Embodiments of the applicator  15504  can take various forms. As illustrated in  FIG. 128A , in one embodiment, the applicator  15504  can include a tubular shaft in fluid communication with a reservoir (not shown) of the adjunct precursor  15500 . Under the influence of pressure, the adjunct precursor  15500  is urged from a distal end of the applicator  15504  and onto the surface of the tissue  15502 . A person skilled in the art will appreciate that the applicator can adopt other configurations suitable for deposition of the adjunct precursor  15500  upon the tissue  15502 . As illustrated in  FIG. 128B , in another embodiment, an applicator  15506  can include a brush that contains the adjunct precursor  15500  (e.g., within bristles  15508  of the brush). 
     The adjunct precursor  15500  can be configured to solidify after deposition upon the tissue  15502  to form a solid adjunct. Solidification of the adjunct precursor  15500  to form the solid adjunct can be accomplished using various techniques, such as moistening the adjunct precursor, heating or cooling the adjunct precursor, exposing the adjunct precursor to light energy, applying a hardener to the adjunct precursor, waiting a selected time duration after deposition, etc. 
     In one embodiment, the adjunct precursor  15500  can be a biologically compatible heterogeneous mixture including one or more solid components and one or more solvents. The solvent(s) can evaporate over time due to body heat from the tissue  15502  and/or externally supplied heat, forming the solid adjunct from the remaining solid components. 
     In an alternative embodiment, the adjunct precursor  15500  can be a biologically compatible chemical composition that solidifies (e.g., cures or hardens) after exposure to one or more of light energy (e.g., ultraviolet light), heat, or one or more co-reactants (e.g., catalysts, hardeners, etc.). Solidification of the chemical composition can take the form of cross-linking between components of the chemical composition or components of the chemical composition and co-reactants. Embodiments of the adjunct precursor  15500  that are configured to solidify after exposure to one or more co-reactants can receive the co-reactants in a variety of ways. In one aspect, the co-reactant can be mixed with the adjunct precursor  15500  at a selected time prior to deposition upon the tissue  15502  (e.g., immediately prior to deposition). In another aspect, the co-reactant can be applied to the adjunct precursor  15500  after deposition (e.g., by a dropper or sprayer). In a further aspect, the co-reactant can be transferred from the surface of an object to the adjunct precursor  15500  by contact. For example, as shown in  FIG. 5C , a mesh  15510  including the co-reactant can be applied to the deposited adjunct precursor  15500  prior to solidification (e.g., over the adjunct precursor  15500  and/or embedded within the deposited adjunct precursor  15500 ). The co-reactant can be positioned on the surface of the mesh  15510  or contained within the mesh  15510  and released upon contact with the adjunct precursor  15500 . Alternatively or additionally, at least a portion of the mesh  15510  can be formed from the co-reactant. In further embodiments, the co-reactant can be provided in any combination of the above. Beneficially, use of the mesh  15510  can provide further reinforcement to the solid precursor. 
     Following solidification of the adjunct precursor  15500  to form the solid adjunct  15512 , one or more staples  15514  can be delivered through the solid adjunct  15512  and into the tissue  15502 . As illustrated in  FIGS. 128D-128E , the end effector  30  of the stapler  10  can grasp the tissue  15502  at the location of the solid adjunct  15512  using the jaws  32 ,  34  and the firing system can be actuated to eject one or more staples  15514  into the clamped tissue  15502 . As discussed above, the knife blade  36  (see  FIG. 3 ) or other cutting element can be associated with the firing system to cut the tissue  15502  during the stapling procedure, after tissue fixation has started. 
       FIGS. 129A-129B  illustrate placement of another embodiment of an adjunct  15600  upon a surface of a tissue  15602  by an adjunct delivery device  15604 . The adjunct delivery device  15604  can generally be configured and used similarly to the stapler  10  for grasping the tissue  15602 , except that the staple cartridge and firing system are omitted. As an example, the adjunct delivery device  15604  can include an elongate shaft  15606  having a non-stapling end effector  15610  at a distal end  15606   d  with opposed first and second jaws  15612 ,  15614  configured to grasp the tissue  15602  therebetween. The adjunct delivery device  15604  can further include a handle assembly (not shown) connected to a proximal end of the shaft  15606  and configured to manipulate and operate the non-stapling end effector  15610  similar to the handle assembly  12 . 
     The non-stapling end effector  15610  can be configured to secure the adjunct  15600  thereon for placement of the adjunct  15600  at a treatment site of the tissue  15602  and to release the adjunct  15600  when the tissue  15602  is engaged by the non-stapling end effector  15610 . As illustrated in  FIGS. 129A-129B , the first and second jaws  15612 ,  15614  can include approximately flat tissue contacting surfaces  15616 ,  15620  with a plurality of sockets  15622 ,  15624 . The sockets  15622 ,  15624  are configured to receive corresponding barbed pins  15626 ,  15630 . When the adjunct  15600  is positioned on the tissue contacting surfaces  15616 ,  15620 , the barbed pins  15626 ,  15630  extend through the adjunct  15600 , securing the adjunct  15600  thereto by frictional engagement. After the adjunct  15600  is positioned adjacent to the tissue  15602 , the jaws  15612 ,  15614  can be compressed to engage the tissue  15602 . The compressive force exerted by the jaws  15612 ,  15614  can drive a portion of the barbed pins  15626 ,  15630  into the tissue  15602 . Thus, when the jaws  15612 ,  15614  are retracted from the tissue  15602 , the barbed pins  15626 ,  15630  are retained in the tissue and the frictional engagement the barbed pins  15626 ,  15630  and the adjunct  15600  retains the adjunct  15600  in position on the tissue  15602  prior to stapling. 
     As shown, the adjunct  15600  can be formed from a single piece of material that includes a hinge  15632 . This hinged configuration can allow a first adjunct portion  15600   a  on one side of the hinge  15632  to be retained on the first jaw  15612  by the barbed pins  15626  and a second adjunct portion  15600   b  on the other side of the hinge  15632  to be retained on the second jaw  15614  by the barbed pins  15630 . Beneficially, because the first and second adjunct portions  15600   a ,  15600   b  are connected by the hinge  15632 , the first and second adjunct portions  15600   a ,  15600   b  remain aligned when positioned on opposing sides of the tissue  15602 . The adjunct  15600  and the barbed pins  15626  can be formed from bioabsorbable materials, as discussed above, so that they are absorbed by the body during healing. 
     Optionally, the first and second adjunct portions  15600   a ,  15600   b  can include a plurality of holes  15634  for receiving corresponding barbed pins  15626 ,  15630 . The holes  15634  can possess a diameter smaller than a diameter the barbed pins  15626 ,  15630  to facilitate frictional engagement of the adjunct  15600  with the barbed pins  15626 ,  15630 . Alternatively, the holes  15634  can be omitted and the barbed pins  15626 ,  15630  can puncture the adjunct  15600  for frictional engagement when positioned on the jaws  15612 ,  15614 . 
     Following placement of the adjunct  15600  upon the tissue  15602  by the adjunct delivery device  15604 , one or more staples  15636  can be delivered through the adjunct  15600  and into the tissue  15602 . As illustrated in  FIGS. 130A-130B , the end effector  30  of the stapler  10  can grasp the tissue  15602  at the location of the adjunct  15600  using the jaws  32 ,  34  and the firing system can be actuated to eject one or more staples  15636  into the clamped tissue  15602 . As discussed above, the knife blade  36  (see  FIG. 3 ) or other cutting element can be associated with the firing system to cut the tissue  15602  during the stapling procedure, after tissue fixation has started. 
     A person skilled in the art will appreciate that, while  FIGS. 129A-130B  illustrate the adjunct  15600  as a generally planar structure including the hinge  15632 , the adjunct  15600  can adopt any desired shape. In one example (not shown), the hinge  15632  can be omitted and adjunct can be formed from two separate pieces that are secured to respective jaws  15612 ,  15614 . 
     In another example,  FIGS. 131A-131C  illustrate a flanged adjunct  15800  configured to be positioned on a tissue  15802  by the adjunct delivery device  15604 . The flanged adjunct  15800  includes flanges  15804  along lateral edges that, when mounted on the adjunct delivery device  15604 , extend towards respective jaws  15612 ,  15614  upon which the flanged adjunct  15800  is mounted. When positioned on the tissue  15802 , the flanges  15804  can be dimensioned to facilitate alignment of a stapler  10  with the flanged adjunct  15800  for delivery of one or more staples  15806  through the flanged adjunct  15800  and tissue  15802 . Optionally, the flanged adjunct  15800  can be formed from a single, continuous piece with a hinge (not shown), as discussed above, to maintain alignment between respective portions of the flanged adjunct  15800 . In either instance, the flanged adjunct  15800  can be delivered to tissue, and subsequently the flanges  15804  can guide the jaws  15612 ,  15614  into alignment with the flanged adjunct  15800  for staple delivery. 
     Another embodiment of an adjunct system  15900  configured for use with the stapler  10  is illustrated in  FIGS. 132A-132B . The adjunct system  15900  includes an adjunct  15902  and a sheet of material  15904 , different from the adjunct  15902 . The adjunct  15902  can be configured to be attached to the first jaw  32  including the staple cartridge  40  containing a plurality of staples and the sheet of material  15904  can be configured to be attached to the second jaw  34 . In certain embodiments, the adjunct  15902  is only attached to the first jaw  32  and not the second jaw  34 . The first and second jaws  32 ,  34  can include one or more attachment mechanisms for securing the adjunct  15902  and the sheet of material  15904  thereto. Examples of attachment mechanisms can include, but not limited to, adhesives, protrusions, etc. The strength with which the attachment mechanism secures the adjunct  15902  and sheet of material  15904  to respective jaws  32 ,  34  can be sufficient to retain adjunct  15902  and sheet of material  15904  thereon during placement of the adjunct system  15900  on a tissue  15906  and to release the adjunct  15902  and the sheet of material  15904  when staples are deployed through the adjunct  15902 . As an example, when the end effector  30  fires a plurality of staples  15910  through the adjunct  15902 , the sheet of material  15904 , and the tissue  15906 , the staples  15910  can secure the adjunct  15902  to the tissue  15906  with sufficient force to retain the adjunct  15902  on the tissue  15906  when the end effector  30  is retracted from the tissue  15906  ( FIG. 132B ). 
     Terminology 
     It will be appreciated that the terms “proximal” and “distal” are used herein with reference to a user, such as a clinician, gripping a handle of an instrument. Other spatial terms such as “front” and “back” similarly correspond respectively to distal and proximal. It will be further appreciated that for convenience and clarity, spatial terms such as “vertical” and “horizontal” are used herein with respect to the drawings. However, surgical instruments are used in many orientations and positions, and these spatial terms are not intended to be limiting and absolute. 
     A person skilled in the art will appreciate that the present invention has application in conventional minimally-invasive and open surgical instrumentation as well application in robotic-assisted surgery. In some embodiments, the devices and methods described herein are provided for open surgical procedures, and in other embodiments, the devices and methods are provided for laparoscopic, endoscopic, and other minimally invasive surgical procedures. The devices may be fired directly by a human user or remotely under the direct control of a robot or similar manipulation tool. However, a person skilled in the art will appreciate that the various methods and devices disclosed herein can be used in numerous surgical procedures and applications. Those skilled in the art will further appreciate that the various instruments disclosed herein can be inserted into a body in any way, such as through a natural orifice, through an incision or puncture hole formed in tissue, or through an access device, such as a trocar cannula. For example, the working portions or end effector portions of the instruments can be inserted directly into a patient&#39;s body or can be inserted through an access device that has a working channel through which the end effector and elongated shaft of a surgical instrument can be advanced. 
     Furthermore, the devices disclosed herein can be designed to be disposed of after a single use, or they can be designed to be used multiple times. In either case, however, the device can be reconditioned for reuse after at least one use. Reconditioning can include any combination of the steps of disassembly of the device, followed by cleaning or replacement of particular pieces and subsequent reassembly. In particular, the device can be disassembled, and any number of the particular pieces or parts of the device can be selectively replaced or removed in any combination. Upon cleaning and/or replacement of particular parts, the device can be reassembled for subsequent use either at a reconditioning facility, or by a surgical team immediately prior to a surgical procedure. Those skilled in the art will appreciate that reconditioning of a device can utilize a variety of techniques for disassembly, cleaning/replacement, and reassembly. Use of such techniques, and the resulting reconditioned device, are all within the scope of the present application. 
     One skilled in the art will appreciate further features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.