Patent Publication Number: US-11648007-B2

Title: Compressible knitted adjuncts with varying fiber features

Description:
FIELD 
     Compressible knitted adjuncts and methods of using the same are provided. 
     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. 
     Some surgical staplers require a surgeon to select the appropriate staples having the appropriate staple height for the tissue being stapled. For example, a surgeon could select tall staples for use with thick tissue and short staples for use with thin tissue. In some instances, however, the tissue being stapled does not have a consistent thickness and, thus the staples cannot achieve the desired fired configuration at each staple site. As a result, a desirable seal at or near all of the stapled sites cannot be formed, thereby allowing blood, air, gastrointestinal fluids, and other fluids to seep through the unsealed sites. 
     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, and therefore are unable to withstand the varying intra-tissue pressures at the implantation site. This can lead to undesirable tissue tearing, and consequently leakage, at or near the staple site. 
     Accordingly, there remains a need for improved devices and methods that address current issues with surgical staplers. 
     SUMMARY 
     Stapling assemblies for use with a surgical stapler are provided. In one exemplary embodiment, a stapling assembly includes a cartridge and a knitted adjunct. The cartridge has a plurality of staples disposed therein and configured to be deployed into tissue. The knitted adjunct is configured to be releasably retained on the cartridge such that the adjunct can be attached to tissue by the plurality of staples in the cartridge. The adjunct has first end, a second end, and a longitudinal axis extending therebetween. The adjunct can include a first compression zone formed of at least first fibers and second fibers, and the second fibers can be interconnected to the first fibers and arranged in a generally first columnar configuration such that the first compression zone has a first compression strength. The adjunct can include a second compression zone formed of at least the first fibers and third fibers that are different than the second fibers. The third fibers can be interconnected to the first fibers and arranged in a generally second columnar configuration such that the second compression zone has a second compression strength. The first compression strength can be different than the second compression strength such that the adjunct has a variable compression strength. 
     In some embodiments, the second fibers can be monofilament fibers and the third fibers can be multifilament fibers. 
     In some embodiments, the first compression zone can include fourth fibers that interconnected to the second fibers. 
     The second compression zone can have a variety of configurations. For example, in some embodiments, the second compression zone can include fourth fibers that interconnected to the third fibers. In other embodiments, at least a portion of the second compression zone can be positioned about a perimeter of the adjunct. 
     In some embodiments, the interconnections between the first and second fibers can form a tissue-contacting surface of the adjunct and the interconnections between the first and third fibers can form a cartridge-contacting surface of the adjunct. 
     In some embodiments, the first and second fibers can be interconnected to each other at first knots, in which the first and third fibers can be interconnected to each other at second knots that differ from the first knots. 
     In some embodiments, the first knots and second knots can differ in tightness. 
     In some embodiments, the cartridge can include a slot formed therein and extending along at least a portion of a longitudinal axis thereof, and the first compression zone can be configured to at least partially overlap with the slot when the adjunct is attached to the cartridge. 
     In another exemplary embodiment, a stapling assembly for use with a surgical stapler includes a cartridge and a knitted adjunct. The cartridge has a plurality of staples disposed therein and a slot formed therein and extending along a longitudinal axis of the cartridge and configured to receive a cutting element. The knitted adjunct is configured to be releasably retained on the cartridge such that the adjunct can be attached to tissue by the plurality of staples in the cartridge. The adjunct includes a tissue-contacting layer formed of at least first fibers that are configured to substantially prevent movement of the adjunct relative to the cartridge when tissue slides across the adjunct, a cartridge-contacting layer formed of at least second fibers, and first spacer fibers and second fibers that are different than the first spacer fibers. The first and second spacer fibers can be intertwined with and extend between the tissue-contacting layer and the cartridge contacting layers to thereby connect the layers together. The first spacer fibers can be positioned within a first region of the adjunct that is configured to overlap at least a portion of the slot, and the second spacer fibers can be positioned within a second region of the adjunct that at least partially borders the first region. 
     In some embodiments, the first region of the adjunct can have a first compression strength and the second region of the adjunct can have a second compression strength that is greater than the first compression strength. 
     In some embodiments, the second section of the adjunct can be positioned about at least a portion of an outer-most perimeter of the adjunct. 
     In some embodiments, at least one of the first fibers and the second fibers can be monofilament fibers. 
     In some embodiments, the tissue-contacting layer can have a first fiber density of the first fibers, and the cartridge-contacting layer can have a second fiber density of the second fibers that are greater than the first fiber density. 
     In some embodiments, the second fibers can be configured to attach the adjunct to the cartridge. 
     The spacer fibers can have a variety of configurations. For example, in some embodiments, a portion of the spacer fibers can be configured to extend outward from the cartridge-contacting layer when the adjunct is compressed. 
     In some embodiments, the cartridge-contacting layer can include third fibers that are intertwined with at least one of the second fibers, the first spacer fibers, and second fibers. 
     The third fibers can have a variety of configurations. For example, in some embodiments, the third fibers can form traction loops that are configured to engage the cartridge to thereby retain the adjunct thereon prior to staple deployment. In other embodiments, the third fibers can be multifilament fibers. 
    
    
     
       BRIEF DESCRIPTION OF THE 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 exemplary embodiment of a conventional surgical stapling and severing device; 
         FIG.  2 A  is a top view of a staple cartridge for use with the surgical stapling and severing device of  FIG.  1   ; 
         FIG.  2 B  is a side view of the staple cartridge of  FIG.  2 A ; 
         FIG.  2 C  is a perspective view of a portion of a tissue contacting surface of the staple cartridge of  FIG.  2 A ; 
         FIG.  3    is a side view of a staple in an unfired (pre-deployed) configuration that can be disposed within the staple cartridge of the surgical cartridge assembly of  FIG.  2 A ; 
         FIG.  4    is a perspective view of a knife and firing bar (“E-beam”) of the surgical stapling and severing device of  FIG.  1   ; 
         FIG.  5    is a perspective view of a wedge sled of a staple cartridge of the surgical stapling and severing device of  FIG.  1   ; 
         FIG.  6    is a longitudinal cross-sectional view of an exemplary embodiment of a surgical stapling assembly having a compressible knitted adjunct attached to a top or deck surface of a staple cartridge; 
         FIG.  7    is a partial-schematic illustrating the adjunct of  FIGS.  6 A- 6 B  in a tissue deployed condition; 
         FIG.  8 A  is a perspective view of an exemplary embodiment of a stapling assembly having a compressible knitted adjunct releasably retained on a staple cartridge; 
         FIG.  8 B  is a cross-sectional view of the portion of the stapling assembly of  FIG.  8 A  taken at line  8 B- 8 B; 
         FIG.  9 A  is a perspective view of another exemplary embodiment of compressible knitted adjunct; 
         FIG.  9 B  is a cross-sectional view of the adjunct of  FIG.  9 A  taken at line  9 B- 9 B; 
         FIG.  10 A  is a perspective view of another exemplary embodiment of a stapling assembly having a compressible knitted adjunct releasably retained on a staple cartridge; 
         FIG.  10 B  is a top view of the stapling assembly of  FIG.  10 A ; 
         FIG.  10 C  is a cross-sectional view of the stapling assembly of  FIG.  10 B  taken at line  10 C- 10 C; 
         FIG.  10 D  is a cross-sectional view of the stapling assembly of  FIG.  10 B  taken at line  10 D- 10 D; 
         FIG.  11 A  is a perspective view of another exemplary embodiment of compressible knitted adjunct; 
         FIG.  11 B  is a cross-sectional view of the adjunct of  FIG.  11 A  taken at line  11 B- 11 B; 
         FIG.  12    is a perspective view of another exemplary embodiment of stapling assembly having a compressible knitted adjunct; 
         FIG.  13 A  is a cross-sectional view of another exemplary embodiment of a stapling assembly having a compressible knitted adjunct releasably retained on a staple cartridge; 
         FIG.  13 B  is a cross-sectional view of the compressible knitted adjunct and staple cartridge of  FIG.  13 A  in a detached configuration prior to being releasably retained; 
         FIG.  14 A  is a cross-sectional view of an exemplary embodiment of a compressible knitted adjunct in an uncompressed state; 
         FIG.  14 B  is a cross-sectional view of the adjunct of  FIG.  14 A  in a first compressed state; 
         FIG.  15 A  is a cross-sectional view of an exemplary embodiment of a compressible knitted adjunct in an uncompressed state; 
         FIG.  15 B  is a cross-sectional view of the adjunct of  FIG.  15 A  in a first compressed state; 
         FIG.  16 A  is a cross-sectional view of an exemplary embodiment of a compressible knitted adjunct in an uncompressed state; 
         FIG.  16 B  is a cross-sectional view of the adjunct of  FIG.  16 A  in a first compressed state; 
         FIG.  17 A  is a cross-sectional view of an exemplary embodiment of a compressible knitted adjunct in an uncompressed state; 
         FIG.  17 B  is a cross-sectional view of the adjunct of  FIG.  17 A  in a first compressed state; 
         FIG.  18 A  is a side view of an exemplary embodiment of a compressible knitted adjunct having reinforcing knots; 
         FIG.  18 B  is a bottom view of the knitted adjunct of  FIG.  18 A ; 
         FIG.  19 A  is a side view of an exemplary embodiment of a compressible knitted adjunct without reinforcing knots; 
         FIG.  19 B  is a bottom view of the knitted adjunct of  FIG.  19 A ; 
         FIG.  20    is a cross-sectional view of another exemplary embodiment of a compressible knitted adjunct; 
         FIG.  21 A  is a perspective view of another exemplary embodiment of a compressible knitted adjunct; and 
         FIG.  21 B  is a cross-sectional view of the adjunct of  FIG.  21 A  taken at line  21 B- 21 B. 
     
    
    
     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 adjuncts, systems, 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 adjuncts, 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. 
     Surgical stapling assemblies and methods for manufacturing and using the same are provided. In general, a surgical stapling assembly can include a staple cartridge having staples disposed therein and a compressible, knitted adjunct configured to be releasably retained on the staple cartridge. As discussed herein, the various adjuncts provided can be configured to compensate for variations in tissue properties, such as variations in tissue thickness, and/or to promote tissue ingrowth when the adjuncts are stapled to tissue. Further, the various adjuncts can be designed in such a way that inhibits the fraying and/or tearing thereof. This can improve the aesthetics and/or structural integrity of the adjunct. 
     An exemplary stapling assembly can include a variety of features to facilitate application of a surgical staple, as described herein and illustrated in the drawings. However, a person skilled in the art will appreciate that the stapling assembly can include only some of these features and/or it can include a variety of other features known in the art. Any stapling assembly known in the art can be used. The stapling assemblies described herein are merely intended to represent certain exemplary embodiments. Moreover, while the adjuncts are described in connection with surgical staple cartridge assemblies, the adjuncts can be used in connection with staple reloads that are not cartridge based or any type of surgical device. 
       FIG.  1    illustrates an exemplary surgical stapling and severing device  100  suitable for use with an implantable adjunct. The illustrated surgical stapling and severing device  100  includes a staple applying assembly  106  or end effector having an anvil  102  that is pivotably coupled to an elongate staple channel  104 . As a result, the staple applying assembly  106  can move between an open position, as shown in  FIG.  1   , and a closed position in which the anvil  102  is positioned adjacent to the elongate staple channel  104  to engage tissue therebetween. The staple applying assembly  106  can be attached at its proximal end to an elongate shaft  108  forming an implement portion  110 . When the staple applying assembly  106  is closed, or at least substantially closed, (e.g., the anvil  102  moves from the open position in  FIG.  1    toward the elongate staple channel) the implement portion  110  can present a sufficiently small cross-section suitable for inserting the staple applying assembly  106  through a trocar. While the device  100  is configured to staple and sever tissue, surgical devices configured to staple but not sever tissue are also contemplated herein. 
     In various instances, the staple applying assembly  106  can be manipulated by a handle  112  connected to the elongate shaft  108 . The handle  112  can include user controls such as a rotation knob  114  that rotates the elongate shaft  108  and the staple applying assembly  106  about a longitudinal axis of the elongate shaft  108 , and a closure trigger  116  which can pivot relative to a pistol grip  118  to close the staple applying assembly  106 . A closure release button  120  can be outwardly presented on the handle  112  when the closure trigger  116  is clamped such that the closure release button  120  can be depressed to unclamp the closure trigger  116  and open the staple applying assembly  106 , for example. 
     A firing trigger  122 , which can pivot relative to the closure trigger  116 , can cause the staple applying assembly  106  to simultaneously sever and staple tissue clamped therein. In various instances, multiple firing strokes can be employed using the firing trigger  122  to reduce the amount of force required to be applied by the surgeon&#39;s hand per stroke. In certain embodiments, the handle  112  can include one or more rotatable indicator wheels such as, for example, rotatable indicator wheel  124  which can indicate the firing progress. A manual firing release lever  126  can allow the firing system to be retracted before full firing travel has been completed, if desired, and, in addition, the firing release lever  126  can allow a surgeon, or other clinician, to retract the firing system in the event that the firing system binds and/or fails. 
     Additional details on the surgical stapling and severing device  100  and other surgical stapling and severing devices suitable for use with the present disclosure are described, for example, in U.S. Pat. No. 9,332,984 and in U.S. Patent Publication No. 2009/0090763, the disclosures of which are incorporated herein by reference in their entireties. Further, the surgical stapling and severing device need not include a handle, but instead can have a housing that is configured to couple to a surgical robot, for example, as described in U.S. Patent Publication No. 2019/0059889, the disclosure of which is incorporated herein by reference in its entirety. 
     As further shown in  FIG.  1   , a staple cartridge  200  can be utilized with the device  100 . In use, the staple cartridge  200  is placed within and coupled to the elongate staple channel  104 . While the staple cartridge  200  can have a variety of configurations, in this illustrated embodiment, the staple cartridge  200 , which is shown in more detail in  FIGS.  2 A- 2 B , has a proximal end  202   a  and a distal end  202   b  with a longitudinal axis L C  extending therebetween. As a result, when the staple cartridge  200  is inserted into the elongate staple channel  104  ( FIG.  1   ), the longitudinal axis L C  aligns with the longitudinal axis Ls of the elongate shaft  108 . Further, the staple cartridge  200  includes a longitudinal slot  210  defined by two opposing slot edges  210   a ,  210   b  and configured to receive at least a portion of a firing member of a firing assembly, like firing assembly  400  in  FIG.  4   , as discussed further below. As shown, the longitudinal slot  202  extends from the proximal end  202   a  toward the distal end  202   b  of the staple cartridge  200 . It is also contemplated herein that in other embodiments, the longitudinal slot  202  can be omitted. 
     The illustrated staple cartridge  200  includes staple cavities  212 ,  214  defined therein and each staple cavity  212 ,  214  is configured to removably house at least a portion of a staple (not shown). The number, shape, and position of the staple cavities can vary and can depend at least on the size and shape of the staples to be removably disposed therein. In this illustrated embodiment, the staple cavities are arranged in two sets of three longitudinal rows, with the first set of staple cavities  212  positioned on a first side of the longitudinal slot  210  and the second set of staple cavities  214  positioned on a second side of the longitudinal slot  210 . On each side of the longitudinal slot  210 , and thus for each set of rows, a first longitudinal row of staple cavities  212   a ,  214   a  extends alongside the longitudinal slot  210 , a second row of staple cavities  212   b ,  214   b  extends alongside the first row of staple cavities  212   a ,  214   b , and a third row of staple cavities  212   c ,  214   c  extends alongside the second row of staple cavities  212   b ,  214   b . For each set of rows, the first row of staple cavities  212   a ,  214   b , the second row of staple cavities  212   b ,  214   b , and the third row of staple cavities  214   c ,  214   c  are parallel to one another and the longitudinal slot  210 . Further, as shown, for each set of rows, the second row of staple cavities  212   b ,  214   b  is staggered with respect to the first and third rows of staple cavities  212   a ,  212   c ,  214   a ,  214   c . In other embodiments, the staple cavity rows in each set  212 ,  214  are not parallel to one another and/or the longitudinal slot  210 . 
     The staples releasably stored in the staple cavities  212 ,  214  can have a variety of configurations. An exemplary staple  300  that can be releasably stored in each of the staple cavities  212 ,  214  is illustrated in  FIG.  3    in its unfired (pre-deployed, unformed) configuration. The illustrated staple  300  includes a crown (base)  302  and two staple legs  304  extending from each end of the crown  302 . In this embodiment, the crown  302  extends in a linear direction and the staple legs  304  have the same unformed height, whereas in other embodiments, the crown can be a step up crown, and/or the staple legs can have different unformed heights. Further, prior to the staples  300  being deployed, the crowns  302  can be supported by staple drivers that are positioned within the staple cartridge  200  and, concurrently, the staple legs  304  can be at least partially contained within the staple cavities  212 ,  214 . Further, the staple legs  304  can extend beyond a top surface, like top surface  206 , of the staple cartridge  200  when the staples  300  are in their unfired positions. In certain instances, as shown in  FIG.  3   , the tips  306  of the staple legs  304  can be pointed and sharp which can incise and penetrate tissue. 
     In use, staples  300  can be deformed from an unfired position into a fired position such that the staple legs  304  move through the staple cavities  212 ,  214 , penetrate tissue positioned between the anvil  102  and the staple cartridge  200 , and contact the anvil  102 . As the staple legs  304  are deformed against the anvil  102 , the staple legs  304  of each staple  300  can capture a portion of the tissue within each staple  300  and apply a compressive force to the tissue. Further, the staple legs  304  of each staple  300  can be deformed downwardly toward the crown  302  of the staple  300  to form a staple entrapment area in which the tissue can be captured therein. In various instances, the staple entrapment area can be defined between the inner surfaces of the deformed legs and the inner surface of the crown of the staple. The size of the entrapment area for a staple can depend on several factors such as the length of the legs, the diameter of the legs, the width of the crown, and/or the extent in which the legs are deformed, for example. 
     In some embodiments, all of the staples disposed within the staple cartridge  200  can have the same unfired (pre-deployed, unformed) configuration. In other embodiments, the staples can include at least two groups of staples each having a different unfired (pre-deployed, unformed) configuration, e.g., varying in height and/or shape, relative to one another, etc. For example, the staple cartridge  200  can include a first group of staples having a first height disposed within the first row of staple cavities  212   a ,  214   a , a second group of staples having a second height disposed within the second row of staple cavities  212   b ,  214   b , and a third group of staples having a third height disposed within the third row of staple cavities  212   c ,  214   c . In some embodiments, the first, second, and third heights can be different, in which the third height is greater than the first height and the second height. In other embodiments, the first and second heights are the same, but the third height is different and greater than the first height and the second height. A person skilled in the art will appreciate that other combinations of staples are contemplated herein. 
     Further, the staples can include one or more external coatings, e.g., a sodium stearate lubricant and/or an antimicrobial agent(s). The antimicrobial agent(s) can be applied to the staples as its own coating or incorporated into another coating, such as a lubricant. Non-limiting examples of suitable antimicrobial agents include 5-Chloro-2-(2,4-dichlorophenoxy)phenol, chlorhexidine, silver formulations (e.g., nano-crystalline silver), lauric arginate ethyl ester (LAE), octenidine, polyhexamethylene biguanide (PHMB), taurolidine, lactic acid, citric acid, acetic acid, and their salts. 
     Referring back to  FIGS.  2 A- 2 B , the staple cartridge  200  extends from a top surface or deck surface  206  to a bottom surface  208 . The top surface  206  is configured as a tissue-facing surface and the bottom surface  208  is configured as a channel-facing surface. As a result, when the staple cartridge  200  is inserted into the elongate staple channel  104 , as shown in  FIG.  1   , the top surface  206  faces the anvil  102  and the bottom surface  208  (obstructed) faces the elongate staple channel  104 . Further, the top surface  206  has two outer-most terminal longitudinal edges  207   a ,  207   b  that are positioned distal to the longitudinal slot  210  of the staple cartridge  200 . 
     In some embodiments, the top surface  206  can include surface features defined therein. For example, the surface features can be recessed channels defined within the top surface  206 . As shown in more detail in  FIG.  2 C , a first recessed channel  216  surrounds each first staple cavity  212   a ,  214   a . Each first recessed channel  216  is defined by a substantially triangular wall  216   a  having a vertex pointing proximally, a vertex pointing distally, and a vertex pointing laterally outwardly. Further, each first recessed channel  216  includes a first floor  206   a  which is at a first height from the top surface  206 . A second recessed channel  218  surrounds each second staple cavity  212   b ,  214   b . Each second recessed channel  218  is defined by a wall  218   a  which is substantially diamond-shaped comprising a vertex pointing proximally, a vertex pointing distally, a vertex pointing laterally inwardly, and a vertex pointing laterally outwardly relative to the longitudinal axis. Further, each second recessed channel  218  includes a second floor  206   b  which is a second height from the top surface  206 . A third recessed channel  220  surrounds each third staple cavity  212   c ,  214   c . Each third recessed channel  220  is defined by a substantially triangular wall  220   a  comprising a vertex pointing proximally, a vertex pointing distally, and a vertex pointing laterally inwardly relative to the longitudinal axis. Further, each third recessed channel  220  includes a third floor  206   c  which is a third height from the top surface  206 . In some embodiments, the first height of the first recessed channels  216 , the second height of the second recessed channels  218 , and the third height of the third recessed channels  220  can have the same height. In other instances, the first height, the second height, and/or the third height can be different. Additional details on the surface features and other exemplary surface features can be found in U.S. Publication No. 2016/0106427, which is incorporated by reference herein in its entirety. 
     With reference to  FIGS.  4  and  5   , a firing assembly such as, for example, firing assembly  400 , can be utilized with a surgical stapling and severing device, like device  100  in  FIG.  1   . The firing assembly  400  can be configured to advance a wedge sled  500  having wedges  502  configured to deploy staples from the staple cartridge  200  into tissue captured between an anvil, like anvil  102  in  FIG.  1   , and a staple cartridge, like staple cartridge  200  in  FIG.  1   . Furthermore, an E-beam  402  at a distal portion of the firing assembly  400  may fire the staples from the staple cartridge. During firing, the E-beam  402  can also cause the anvil to pivot towards the staple cartridge, and thus move the staple applying assembly from the open position towards a closed position. The illustrated E-beam  402  includes a pair of top pins  404 , a pair of middle pins  406 , which may follow a portion  504  of the wedge sled  500 , and a bottom pin or foot  408 . The E-beam  402  can also include a sharp cutting edge  410  configured to sever the captured tissue as the firing assembly  400  is advanced distally, and thus towards the distal end of the staple cartridge. In addition, integrally formed and proximally projecting top guide  412  and middle guide  414  bracketing each vertical end of the sharp cutting edge  410  may further define a tissue staging area  416  assisting in guiding tissue to the sharp cutting edge  410  prior to being severed. The middle guide  414  may also serve to engage and fire the staples within the staple cartridge by abutting a stepped central member  506  of the wedge sled  500  that effects staple formation by the staple applying assembly  106 . 
     In use, the anvil  102  in  FIG.  1    can be moved into a closed position by depressing the closure trigger in  FIG.  1    to advance the E-beam  402  in  FIG.  4   . The anvil can position tissue against at least the top surface  206  of the staple cartridge  200  in  FIGS.  2 A- 2 C . Once the anvil has been suitably positioned, the staples  300  in  FIG.  3    disposed within the staple cartridge can be deployed. 
     To deploy staples from the staple cartridge, as discussed above, the wedge sled  500  in  FIG.  5    can be moved from the proximal end toward a distal end of the cartridge body, and thus, of the staple cartridge. As the firing assembly  400  in  FIG.  4    is advanced, the sled can contact and lift staple drivers within the staple cartridge upwardly within the staple cavities  212 ,  214 . In at least one example, the sled and the staple drivers can each include one or more ramps, or inclined surfaces, which can co-operate to move the staple drivers upwardly from their unfired positions. As the staple drivers are lifted upwardly within their respective staple cavities, the staples are advanced upwardly such that the staples emerge from their staple cavities and penetrate into tissue. In various instances, the sled can move several staples upwardly at the same time as part of a firing sequence. 
     As indicated above, the stapling device can be used in combination with a compressible adjunct. A person skilled in the art will appreciate that, while adjuncts are shown and described below, the adjuncts disclosed herein can be used with other surgical devices, and need not be coupled to a staple cartridge as described. Further, a person skilled in the art will also appreciate that the staple cartridges need not be replaceable. 
     As discussed above, with some surgical staplers, a surgeon is often required to select the appropriate staples having the appropriate staple height for tissue to be stapled. For example, a surgeon will utilize tall staples for use with thick tissue and short staples for use with thin tissue. In some instances, however, the tissue being stapled does not have a consistent thickness and thus, the staples cannot achieve the desired fired configuration for every section of the stapled tissue (e.g., thick and thin tissue sections). The inconsistent thickness of tissue can lead to undesirable leakage and/or tearing of tissue at the staple site when staples with the same or substantially greater height are used, particularly when the staple site is exposed to intra-pressures at the staple site and/or along the staple line. 
     Accordingly, various embodiments of knitted adjuncts are provided that can be configured to compensate for varying thickness of tissue that is captured within fired (deployed) staples to avoid the need to take into account staple height when stapling tissue during surgery. That is, the adjuncts described herein can allow a set of staples with the same or similar heights to be used in stapling tissue of varying thickness (e.g., from thin to thick tissue) while also, in combination with the adjunct, providing adequate tissue compression within and between fired staples. Thus, the adjuncts described herein can maintain suitable compression against thin or thick tissue stapled thereto to thereby minimize leakage and/or tearing of tissue at the staple sites. 
     Alternatively or in addition, the knitted adjuncts can be configured to promote tissue ingrowth. In various instances, it is desirable to promote the ingrowth of tissue into an implantable adjunct, to promote the healing of the treated tissue (e.g., stapled and/or incised tissue), and/or to accelerate the patient&#39;s recovery. More specifically, the ingrowth of tissue into an implantable adjunct may reduce the incidence, extent, and/or duration of inflammation at the surgical site. Tissue ingrowth into and/or around the implantable adjunct may, for example, manage the spread of infections at the surgical site. The ingrowth of blood vessels, especially white blood cells, for example, into and/or around the implantable adjunct may fight infections in and/or around the implantable adjunct and the adjacent tissue. Tissue ingrowth may also encourage the acceptance of foreign matter (e.g., the implantable adjunct and the staples) by the patient&#39;s body and may reduce the likelihood of the patient&#39;s body rejecting the foreign matter. Rejection of foreign matter may cause infection and/or inflammation at the surgical site. 
     In general, the knitted adjuncts provided herein are designed and positioned atop a staple cartridge, like staple cartridge  200 . When the staples are fired (deployed) from the cartridge, the staples penetrate through the adjunct and into tissue. As the legs of the staple are deformed against the anvil that is positioned opposite the staple cartridge, the deformed legs capture a portion of the adjunct and a portion of the tissue within each staple. That is, when the staples are fired into tissue, at least a portion of the adjunct becomes positioned between the tissue and the fired staple. While the adjuncts described herein can be configured to be attached to a staple cartridge, it is also contemplated herein that the adjuncts can be configured to mate with other device components, such as an anvil of a surgical stapler. A person of ordinary skill will appreciate that the adjuncts provided herein can be used with replaceable cartridges or staple reloads that are not cartridge based. 
       FIG.  6    illustrates an exemplary embodiment of a stapling assembly  600  that includes a staple cartridge  602  and an adjunct  604 . For sake of simplicity, the adjunct  604  is generally illustrated in  FIGS.  6 A- 6 B , and various structural configurations of the adjunct are described in more detail below. Aside from the differences described in detail below, the staple cartridge  602  can be similar to staple cartridge  200  ( FIGS.  1 - 3   ) and therefore common features are not described in detail herein. As shown, the adjunct  604  is positioned against the staple cartridge  602 . While partially obstructed in  FIG.  6   , the staple cartridge  602  includes staples  606 , which can be similar to staple  300  in  FIG.  3   , that are configured to be deployed into tissue. The staples  606  can have any suitable unformed (pre-deployed) height. For example, the staples  606  can have an unformed height between about 2 mm and 4.8 mm. Prior to deployment, the crowns of the staples can be supported by staple drivers (not shown). 
     In the illustrated embodiment, the adjunct  604  can be mated to at least a portion of the top surface or deck surface  608  of the staple cartridge  602 . In some embodiments, the top surface  608  of the staple cartridge  602  can include one or more surface features, like recessed channels  216 ,  218 ,  220  as shown in  FIGS.  2 A and  2 C . The one or more surface features can be configured to engage the adjunct  604  to avoid undesirable movements of the adjunct  604  relative to the staple cartridge  602  and/or to prevent premature release of the adjunct  604  from the staple cartridge  602 . Exemplary surface features are described in U.S. Patent Publication No. 2016/0106427, which is incorporated by reference herein in its entirety. 
     The adjunct  604  is compressible to permit the adjunct to compress to varying heights to thereby compensate for different tissue thickness that are captured within a deployed staple. The adjunct  604  has an uncompressed (undeformed), or pre-deployed, height and is configured to deform to one of a plurality of compressed (deformed), or deployed, heights. For example, the adjunct  604  can have an uncompressed height which is greater than the fired height of the staples  606  disposed within the staple cartridge  602  (e.g., the height (H) of the fired staple  606   a  in  FIG.  7   ). That is, the adjunct  604  can have an undeformed state in which a maximum height of the adjunct  604  is greater than a maximum height of a fired staple (e.g., a staple that is in a formed configuration). In one embodiment, the uncompressed height of the adjunct  604  can be about 10% taller, about 20% taller, about 30% taller, about 40% taller, about 50% taller, about 60% taller, about 70% taller, about 80% taller, about 90% taller, or about 100% taller than the fired height of the staples  606 . In certain embodiments, the uncompressed height of the adjunct  604  can be over 100% taller than the fired height of the staples  606 , for example. 
     In use, once the surgical stapling and severing device, like device  100  in  FIG.  1   , is directed to the surgical site, tissue is positioned between the anvil  612  and the stapling assembly  600  such that the anvil  612  is positioned adjacent to a first side of the tissue and the stapling assembly  600  is positioned adjacent to a second side of the tissue (e.g., the tissue can be positioned against the tissue-contacting surface  604   a  of the adjunct  604 ). Once tissue is positioned between the anvil  612  and the stapling assembly  600 , the surgical stapler can be actuated, e.g., as discussed above, to thereby clamp the tissue between the anvil  612  and the stapling assembly  600  (e.g., between the tissue-compression surface  612   a  of the anvil  612  and the tissue-contacting surface  604   a  of the adjunct  604 ) and to deploy staples from the cartridge through the adjunct and into the tissue to staple and attach the adjunct to the tissue. 
     As shown in  FIG.  7   , when the staples  606  are fired, tissue (T) and a portion of the adjunct  604  are captured by the fired (formed) staples  606   a . The fired staples  606   a  each define the entrapment area therein, as discussed above, for accommodating the captured adjunct  604  and tissue (T). The entrapment area defined by a fired staple  606   a  is limited, at least in part, by a height (H) of the fired staple  606   a . For example, the height of a fired staple  606   a  can be about 0.160 inches or less. In some embodiments, the height of a fired staple  606   a  can be about 0.130 inches or less. In one embodiment, the height of a fired staple  606   a  can be from about 0.020 inches to 0.130 inches. In another embodiment, the height of a fired staple  606   a  can be from about 0.060 inches to 0.160 inches. 
     As described above, the adjunct  604  can be compressed within a plurality of fired staples whether the thickness of the tissue captured within the staples is the same or different within each fired staple. In at least one exemplary embodiment, the staples within a staple line, or row can be deformed such that the fired height is about 2.75 mm, for example, where the tissue (T) and the adjunct  604  can be compressed within this height. In certain instances, the tissue (T) can have a compressed height of about 1.0 mm and the adjunct  604  can have a compressed height of about 1.75 mm. In certain instances, the tissue (T) can have a compressed height of about 1.50 mm and the adjunct  604  can have a compressed height of about 1.25 mm. In certain instances, the tissue (T) can have a compressed height of about 1.75 mm and the adjunct  604  can have a compressed height of about 1.00 mm. In certain instances, the tissue (T) can have a compressed height of about 2.00 mm and the adjunct  604  can have a compressed height of about 0.75 mm. In certain instances, the tissue (T) can have a compressed height of about 2.25 mm and the adjunct  604  can have a compressed height of about 0.50 mm. Accordingly, the sum of the compressed heights of the captured tissue (T) and adjunct  604  can be equal, or at least substantially equal, to the height (H) of the fired staple  606   a.    
     The knitted adjuncts can have a variety of configurations. In general, and as described in more detail below, the knitted adjuncts are formed of fibers that are knitted or woven (e.g., intertwined) together. 
     The knitted adjuncts can be formed of the same fibers, whereas in other embodiments, the knitted adjuncts can be formed of different fibers. The fibers can differ by material, dimensions (e.g., height and/or diameter), and/or structural configuration (e.g., monofilament or multifilament). In certain embodiments, the knitted adjuncts can include monofilament and/or multifilament fibers. As used herein, the term “monofilament fibers” has its own ordinary and customary meaning and can include fibers formed of a single filament. As used herein, the term “multifilament fibers” has its own ordinary and customary meaning and can include fibers formed of two or more filaments that are associated with one another (e.g., twisted or braided) to form a unitary structure. 
     The multifilament fibers can have a variety of configurations. For example, in some embodiments, each multifilament fiber includes from about 6 to 40 filaments. In one embodiment, each multifilament fiber includes from about 14 to 28 filaments. The increased surface area and voids that exist between the filaments of the multifilament fibers can facilitate improved tissue ingrowth within the adjunct. 
     The multifilament fibers can be formed of filaments formed of the same material or filaments of different materials. For example, in some embodiments, the multifilament fibers can include first filaments of a first material and second filaments of a second material. In one embodiment, the second material degrades at a faster rate than a degradation rate of the first material. In this way, the degradation of the second material can activate, and thus encourage accelerated attraction of, macrophages and accelerate the inflammation phase of healing while not substantially affecting the variable stiffness profile of the adjunct over time following implantation. The activation of macrophages can in turn cause increases in myofibroblast population and neovascularization. Further, the degradation of the second material can encourage tissue ingrowth within the adjunct. The first material, for example, can be at least one of poly-L-lactic acid, a copolymer of glycolide and L-lactide, a copolymer of glycolic acid and lactic acid, poly(lactic-co-glycolic acid), poly(lactic acid), polyglycolide, and a copolymer of glycolide, caprolactone, trimethylene carbonate, and lactide. Non-limiting examples of suitable first materials can be formed of polyglactin 910, Lactomer™ 9-1, 75:25 or 50:50 lactic acid/glycolic acid, Polygytone™ 6211, or Caprosyn™. The second material, for example, can be a copolymer of glycolide and L-lactide, such as Vicryl Rapide™. 
     While the multifilament fibers can include the second filaments at various percentage ranges, in some embodiments, the multifilament fibers can each include second filaments at a range of about 15% to 85% or at a range of about 25% to 45%. The second filaments can have various fiber diameters. For example, in some embodiments, the second filaments can have a fiber diameter from about 0.0005 mm to 0.02 mm. In one embodiment, the second filaments have a fiber diameter of about 0.015 mm. 
     The monofilament fibers can have a variety of sizes. For example, the monofilaments can have a diameter of about 0.2 mm to 0.35 mm. In some embodiments, the monofilament fibers can each have a diameter that is less than an average fiber diameter of the multifilament fibers. The average fiber diameter (D) of a multifilament fiber can be calculated using the following formula: 
     
       
         
           
             D 
             = 
             
               
                 
                   4 
                   ⁢ 
                   W 
                 
                 
                   N 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   ρπ 
                 
               
             
           
         
       
     
     wherein:
         W=weight of multifilament fiber (fiber bundle) per unit length   N=number of filaments   ρ=density of fiber.       

     The multifilament fibers can have a variety of sizes. For example, each multifilament fiber can have an average fiber diameter of about 0.02 mm to 0.2 mm, of about 0.05 mm to 0.2 mm, or of about 0.15 mm to 0.2 mm. In some embodiments, each filament of the multifilament fibers has a diameter that is less than a fiber diameter of the monofilament fibers. For example, where the adjunct includes first fibers that are multifilament fibers and second fibers that are monofilament fibers, each filament of the multifilament fibers can have a diameter that is about ⅕ to 1/20 the diameter of the monofilament fibers. In certain embodiments, each filament of the multifilament fibers can have a diameter that is about 1/10 the diameter of the monofilament fibers. 
     As discussed above, a portion of the adjunct is captured with tissue within the fired staple and therefore it is desirable that the adjunct be formed of suitable bioabsorbable materials. As such, the fibers can each be formed of bioabsorbable material(s). Non-limiting examples of suitable bioabsorbable materials include poly-L-lactic acid, a copolymer of glycolide and L-lactide, a copolymer of glycolic acid and lactic acid, poly(lactic-co-glycolic acid), poly(lactic acid), polyglycolide, and a copolymer of glycolide, caprolactone, trimethylene carbonate, and lactide, polydioxanone, a copolymer of polydioxanone and polyglycolide, a copolymer of lactide and polycaprolactone), a copolymer of glycolide, dioxanone, and trimethylene carbonate, poly(trimethylene carbonate), polyhydroxyalkanoate, and polyglyconate. 
     In some embodiments, a knitted adjunct can include at least two different types of fibers. Non-limiting examples of suitable materials for the first type of fibers include at least one of poly-L-lactic acid, a copolymer of glycolide and L-lactide, a copolymer of glycolic acid and lactic acid, poly(lactic-co-glycolic acid), poly(lactic acid), polyglycolide, and a copolymer of glycolide, caprolactone, trimethylene carbonate, and lactide. For example, the first type of fibers can be formed of polyglactin 910, Lactomer™ 9-1, 75:25 or 50:50 lactic acid/glycolic acid, Polygytone™ 6211, or Caprosyn™. Non-limiting examples of suitable materials for the second type of fibers include at least one of polydioxanone, a copolymer of polydioxanone and polyglycolide, a copolymer of lactide and polycaprolactone), a copolymer of glycolide, dioxanone, and trimethylene carbonate, poly(trimethylene carbonate), polyhydroxyalkanoate, and polyglyconate. For example, the second type of fibers can be formed of 92:8 polydioxanone/Polyglycolide, 25:75 lactide/polycaprolactone, Glycomer™ 631, or Maxon™. In one embodiment, the first type of fibers is formed of polyglactin 910 and the second type of fibers is formed of polydioxanone. 
     The knitted adjuncts can have various sizes, shapes, and configurations. In general, an adjunct includes at least core or intermediate layer and at least one outer layer. For example, the adjunct can include a first outer layer (e.g. a top or tissue-contacting layer) formed of at least first fibers that are knitted or woven together (e.g., a knitted layer) and a second outer layer (e.g., a bottom or cartridge-contacting layer) formed of at least second fibers that are knitted or woven together (e.g., a knitted layer). The first and second fibers can be the same or different. The adjunct can also include spacer fibers that can be the same or different than the first and second fibers. The spacer fibers intertwine with and extend between the first and second outer layers to thereby connect these layers together such that the portions of the spacer fibers extending between the two outer layers form at least one of the at least one core or intermediate layer of the adjunct. 
     Each layer of the adjunct extends from a first surface (e.g., a top surface) to a second surface (e.g., a bottom surface). Depending on the overall structural configuration of the adjunct, at least a portion of the first surface of one layer can serve as a tissue-contacting surface, and at least a portion of the second surface of another layer can serve as a cartridge-contacting surface. A person skilled in the art will appreciate that the adjunct can have additional tissue-contacting surfaces (e.g., one or more lateral side surfaces relative to the top surface). 
     In some embodiments, the spacer fibers interconnect with the first and second fibers of the outer layers in a manner in which the spacers fibers are non-fixedly attached and slidably interconnected. As such, the fibers can move relative to each other, thereby allowing for movement and for expansion of the knitted adjunct in the x-direction (e.g., stretch) and the y-direction (e.g., compression). Additionally, the interconnection between the spacer fibers and the first and second fibers of the outer layers can affect, at least in part, the stiffness of the adjunct. For example, the tighter the interconnections, the stiffer the adjunct. 
     The first and second outer layers can each include a plurality of openings formed therein. The perimeter of the openings of the first outer layer can be defined by portions of the first fibers and of the spacer fibers, whereas the perimeter of the openings of the second outer layer can be defined by portions of the second fibers and of the spacer fibers. In certain embodiments, the openings of the second outer layer can have a size that is less than about ¼ of a width of a crown of a staple, like staple  300  in  FIG.  3   . In such embodiments, the crown of the fired staple can therefore span over at least four openings in the second outer layer. In one embodiment, the openings can have a size that is about ⅛ of the width of the crown. While the crown of a staple can have a variety of widths, in some embodiments, the width of the crown can be about 0.080 inches to 0.140 inches. In one embodiment, the width of the crown is about 0.12 inches. 
     In certain embodiments, the portions of the spacer fibers that extend between the first and second outer layers can be arranged to form standing fibers and a plurality of voids therebetween. The standing fibers are non-fixedly attached to each other. Further, the standing fibers are non-fixedly and slidably interconnected to the first type of fibers of the first and second outer layers. In some implementations, the plurality of voids can be larger than the plurality of openings in the first and second outer layers. 
     The standing fibers can be configured to bend under force being applied to the adjunct (e.g., when stapled to tissue). The resilience of the standing fibers permits the adjunct, at least in part, to compress at various heights to thereby accommodate tissue (T) with tissue portions of different thicknesses. That is, independent of the particular tissue thickness, the sum of the compressed heights of the captured tissue and adjunct within the fired staple can be maintained, and thus can remain equal, or at least substantially equal, to the height of the fired staple. In this way, at least in part, the knitted adjunct can be configured to apply a stress of at least about 3 gf/mm 2  to the captured tissue for at least a predetermined period (e.g., at least about 3 days). 
     Generally, the material composition, the height, and/or the transverse cross-sectional area of each standing fiber controls, at least in part, its stiffness or ability to bend under compression which, in turn, controls, at least in part, the overall compressibility of the adjunct. Accordingly, the standing fibers can be configured to tune the compressibility of the adjunct to one or more desired values. For example, in some embodiments, the standing fibers can be formed of the same material, whereas in other embodiments, at least a portion of the standing fibers can be formed of different materials with different stiffnesses. Alternatively or in addition, the standing fibers, or at least a portion thereof, can have different heights and/or transverse cross-sectional areas. 
     The amount of the standing fibers within a certain region or section of the adjunct can also affect, among other things, the compressibility of such section, and thus the overall compressibility of the adjunct. In certain instances, the standing fibers can be strategically concentrated in certain regions of adjunct to provide greater compression strength in such regions, for example. In at least one instance, the standing fibers can be concentrated in regions of the core or intermediate layer that are configured to receive staples when the staples are fired. Alternatively, the standing fibers can be concentrated in regions of the adjunct that do not receive staples when the staples are fired (e.g., regions that overlap with the intended cut-line of the adjunct). 
     The ratio of the voids to the standing fibers can vary. In some embodiments, this ratio can be in the range of at least about 3:1. In other embodiments, the ratio of voids to the standing fibers can in the range of at least about 5:1 or of at least about 12:1. Further, at least a portion of the voids can each have a different size. In this way, the variable void sizes throughout the cross-section of the adjunct  804  can promote extracellular remodeling. That is, the variable void sizes can facilitate revascularization as well as mobility of cells within the adjunct when the adjunct is implanted, thereby encouraging both tissue and cellular ingrowth. Further the variable void sizes can also facilitate extraction of byproducts and cellular waste from the implanted adjunct, and thus the implantation site. 
     Edges Conditions 
     As discussed above, the knitted adjuncts are formed of fibers that are knitted or woven together. In certain embodiments, the knitted adjuncts can be designed such that the free ends of at least a portion of the fibers are connected together so as to form one or more finished edges of the adjunct. The one or more finished edges are configured to substantially, or completely, prevent fraying or fiber separation therealong. As a result, the structural integrity of the adjunct can be maintained when exposed to forces that would otherwise cause the fibers to fray or separate from each other. The one or more finished edges can also provide an aesthetic effect and/or decrease the variability in both the structure and attendant properties of the present adjuncts, as compared to conventional adjuncts (e.g., adjuncts that do not have finished edges). 
     The one or more finished edges can be formed in a variety of ways. For example, in some embodiments, additional fiber(s) (e.g., fibers different than those used to form the main body of the adjunct) can be used to interconnect the terminal edges of opposing layers of the adjunct together (see  FIGS.  8 A- 10 D ). In such embodiments, the additional fiber(s) can be knitted or woven into the terminal edges in a variety of configurations (e.g., as an overcast stitch, an overedge stitch, a zizzag stitch, and the like). 
       FIGS.  8 A- 8 B  illustrate one exemplary embodiment of a stapling assembly  800  that includes a staple cartridge  802  and a knitted adjunct  804  disposed on a top or deck surface  803  of the staple cartridge  802 . The staple cartridge  802  is similar to staple cartridge  200  in  FIGS.  1 - 2 C , and therefore common features are not described in detail herein. 
     In this illustrated embodiment, as shown in more detail in  FIG.  8 B , the adjunct  804  includes a top layer  806  (e.g., a tissue-contacting layer) formed of at least first fibers  808 , a bottom layer  810  (e.g., a cartridge-contacting layer) formed of at least second fibers  812 , and spacer fibers  814  that are intertwined with and extending between the top and bottom layers  806 ,  810  to thereby connect the top and bottom layers  806 ,  810  together. In this illustrated embodiment, the spacer fibers  814  are multi-looped about the first fibers  808  and about second fibers  812 . The portions of the spacer fibers  814  that extend between the top and bottom layers  806 ,  810  form an intermediate or core layer  816  of the adjunct  804 . For sake of simplicity, only one first fiber  808 , second fiber  812 , and spacer fiber  814  is illustrated in  FIG.  8 B . A person skilled in the art will appreciate that the following discussion is also applicable to the remaining first, second, and spacer fibers of the adjunct. 
     The top and bottom layers  806 ,  810  can have a variety of structural configurations. As shown, the top layer  806  has two outer-most longitudinal terminal edges  806   a ,  806   b , and the bottom layer has two outer-most longitudinal terminal edges  810   a ,  810   b . In some embodiments, the first fibers  808  of the top layer  806  can be knitted or woven into a first predetermined pattern and/or the second fibers  812  of the bottom layer  810  can be knitted or woven into a second predetermined pattern. In certain embodiments, the first and second predetermined patterns can be generally identical (e.g., nominally identical within manufacturing tolerances), whereas in other embodiments, the first and second predetermined patterns can be different. While the first fibers  808  and the second fibers  812  can be knitted or woven in various patterns, in certain embodiments, the first fibers  808  can be knitted into a first Raschel knit pattern and the second fibers  812  can be knitted into a second Raschel knit pattern that is the same or different than the first Raschel knit pattern. Further, in some embodiments, the fiber density of the top layer  806  can be different than the fiber density of the bottom layer  810 . A person skilled in the art will appreciate that the first fibers  808  and the second fibers  812  can be randomly or repeatedly knitted or woven within the top and bottom layers  806 ,  810 , respectively. As such, and for sake of simplicity, the top and bottom layers  806 ,  810  are generally illustrated, and thus the specific structural configurations of the top and bottom layers  806 ,  810  are not limited to what is depicted in the figures. 
     The first fibers  808 , the second fibers  812 , and the spacer fibers  814  can have a variety of configurations. For example, in some embodiments, the first fibers  808 , the second fibers  812 , and the spacer fibers  814  can be generally identical (e.g., nominally identical within manufacturing tolerances) in material and/or structural configuration. In other embodiments, the first and second fibers  808 ,  812  can be generally identical (e.g., nominally identical within manufacturing tolerances) in material and/or structural configuration relative to each other and the spacer fibers  814  can be different relative thereto. For example, in certain embodiments, the first and second fibers  808 ,  812  can be multifilament fibers, and the spacer fibers  814  can be monofilament fibers. As such, aside from the general overall shape, the specific structural configuration of each of the first fibers  808 , the second fibers  812 , and the spacer fibers  814  is not shown. 
     While the adjunct  804  can have a variety of configurations, in the embodiment shown in  FIG.  8 B , the adjunct  804  includes an inner-most segment  820  that includes the first fibers  808 , the second fibers  812 , and the spacer fibers  814 , and first and second outer-most segments  822 ,  824  that are positioned on opposite sides (e.g., longitudinal sides) of the inner-most segment  820  and along the longitudinal axis L A  of the adjunct (e.g., in the z-direction). As a result, when the adjunct  804  is releasably coupled to the top or deck surface  803  of the staple cartridge  802 , the first outer-most segment  822  is adjacent to and extends along the first outer-most longitudinal edge  805   a  of the top surface  803  and the second outer-most segment  824  is adjacent to and extends along the second outer-most longitudinal edge  805   b  of the top surface  803  of the cartridge  802 . 
     While the first and second outer-most segments  822 ,  824  can have different structural configurations, in this illustrated embodiment, the first and second outer-most segments  822 ,  824  are generally identical (e.g., nominally identical within manufacturing tolerances). The first and second outer-most segments  822 ,  824  each include only the first fibers  808  and the second fibers  812 , and thus only portions of the top and bottom layers  806 ,  810 . That is, in this illustrated embodiment, the spacer fibers  814  are not present within the first and second outer-most segments  822 ,  824 , and as a result, the mechanical behavior of the adjunct  804  can be predominately controlled by the inner-most segment  820 , and consequently, by the mechanical behavior of the spacer fibers  814 . In other embodiments, the first outer-most segment  822  and/or the second outer-most segment  824  can include the spacer fibers  814 . Further, as shown, the first outer-most segment  822  includes the first outer-most longitudinal terminal edges  806   a ,  810   a  of the top and bottom layers  806 ,  810 , each of which includes a portion of the free ends of the first fibers  808  and of the second fibers  812 . Similarly, the second outer-most segment  824  includes the second outer-most longitudinal terminal edges  806   b ,  810   b  of the top and bottom layers  806 ,  810 , each of which includes a portion of the free ends of the first fibers  808  and of the second fibers  812 . 
     As shown in more detail in  FIG.  8 B , the portions of the top and bottom layers  806 ,  810  within the inner-most segment  820  extend parallel to one another along the longitudinal axis L A  (e.g., extending in the z-direction) of the adjunct  804  and are spaced apart at a distance D. Similarly, the respective portions of the top layer  806  and bottom layer  810  within the first and second outer-most segments  822 ,  824  extend parallel to one another along the longitudinal axis L A  of the adjunct  804  (e.g., extending in the z-direction) and are spaced apart at a respective distance D 1 , D 2 . As such, the portions of the top and bottom layers  806 ,  810  within the first outer-most segment  822  at least partially overlap with each other and the portions of the top and bottom layers  806 ,  810  within the second outer-most segment  824  at least partially overlap with each other. While in certain embodiments the distances D, D 1 , D 2  can be all the same or all different, in this illustrated embodiment, distance D is different than distance D 1  and distance D 2 , with distance D 1  and distance D 2  being generally identical (nominally identical within manufacturing tolerances). 
     The difference between distance D and distances D 1 , D 2  is due to the tapering transition between the inner-most segment  820  and the first and second outer-most segments  822 ,  824  of the adjunct  804  via first and second intermediate segments  826 ,  828 . The first intermediate segment  826  extends from the inner-most segment  820  to the first outer-most segment  822  and the second intermediate segment  828  extends from the inner-most segment  820  to the second outer-most segment  824 . The first and second intermediate segments  826 ,  828  are tapered in which respective portions of the top layer  806  extend at an angle relative to respective portions of the bottom layer  810 . As shown, the respective portions of the top layer  806  extend towards respective portions of the bottom layer  810  within the first and second intermediate segments  826 ,  828 . As a result, the distance D between the portion of the top and bottom layers  806 ,  810  of the inner-most segment  820  is greater than the distances D 1 , D 2  between the portion of the top and bottom layers  806 ,  810  of the first outer-most segment and of the second outer-most segment, respectively. This relationship between distance D and distances D 1 , D 2  can allow additional fiber(s), like first and second additional fibers  830 ,  832 , to be used to interconnect the one or more terminal edges of the top and bottom layers  806 ,  810  without adversely affecting the overall mechanical behavior of the adjunct  804 . 
     As further shown, the adjunct  804  includes first additional fiber  830  ( FIG.  8 B ) and second additional fiber  832  ( FIGS.  8 A- 8 B ). The first and second additional fibers  830 ,  832  form respective first and second finished edges  834 ,  836 , in which each finished edge is configured to prevent fraying of the top and bottom layers  806 ,  810  therealong, and thus fraying and/or fiber separation of the first fibers  808  and the second fibers  812 . 
     The first and second additional fibers  830 ,  832  can have a variety of configurations. In some embodiments, the first additional fiber  830  and the second additional fiber  832  can be generally identical (nominally identical within manufacturing tolerances) in compositional makeup (e.g., formed of the same material(s)), dimension(s) (e.g., height and/or diameter) and/or in structural configuration (e.g., monofilament or multifilament). In certain embodiments, the first additional fiber  830  and/or the second additional fiber  832  can be a monofilament fiber. In other embodiments, the first additional fiber  830  and/or the second additional fiber  832  can be a multifilament fiber. As such, aside from the general overall shape, the specific structural configuration of the first and second additional fibers  830 ,  832  is not shown. Further, while only one first additional fiber and one second additional fiber are illustrated in  FIGS.  8 A- 8 B , a person skilled in the art will appreciate that more than one first additional fiber and/or more than one second additional fiber and/or other additional fiber(s) can be used to form the finished edges of the adjunct. 
     The first and second additional fibers  830 ,  832  can be incorporated into the adjunct  804  in a variety of ways to form the first and second finished edges  834 ,  836 . In this illustrated embodiment, the first additional fiber  830  interconnects the top and bottom layers  806 ,  810  along their first outer-most longitudinal terminal edges  806   a ,  810   a  to form the first finished edge  834 . As a result, the first finished edge  834  is formed of the first fibers  808 , the second fibers  812 , and the first additional fiber  830  and is positioned along, and thus defines, at least a portion of a first outer-most longitudinal edge  838  of the adjunct  804 . The second additional fiber  832  interconnects the top and bottom layers  806 ,  810  along their respective second outer-most longitudinal terminal edges  806   b ,  810   b  to form the second finished edge  836 . As a result, the second finished edge  836  is formed of the first fibers  808 , the second fibers  812 , and the second additional fiber  832  and is positioned along, and thus defines, at least a portion of a second outer-most longitudinal edge  840  of the adjunct  804 . Thus, at least a portion of the outer-most perimeter of the adjunct is defined by the first and second finished edges  834 ,  836 . 
     Further, the first additional fiber  830  and/or the second additional fiber  832  can be configured as an overcast stitch. For example, as shown in greater detail in  FIG.  8 B , the first additional fiber  830  and the second additional fiber  832  are wrapped around the first outer-most longitudinal terminal edges  806   a ,  810   a  and the second outer-most longitudinal terminal edges  806   b ,  810   b , respectively, in the form of loops (e.g., in a spiral-type or zig-zag configuration). As a result, the portion of free ends of the first and second fibers  808 ,  812  at the first outer-most longitudinal terminal edges  806   a ,  810   a  are secured together by the first additional fiber  830  and the portion of free ends of the first and second fibers  808 ,  812  at the second outer-most longitudinal terminal edges  806   b ,  810   b  are secured together by the second additional fiber  832 . In other embodiments, the first and second additional fibers  830 ,  832  can be configured as other suitable stitch forms. Further, in certain embodiments, the first and second additional fibers  830 ,  832  can configured as different stitch forms. 
       FIGS.  9 A- 9 B  illustrate another exemplary embodiment of a knitted adjunct  900  having one or more finished edges formed by respective additional fibers. Aside from the differences discussed below, the adjunct  900  is similar to adjunct  804  in  FIGS.  8 A- 8 B , and therefore common features are not described in detail herein. 
     The adjunct  900  includes a top layer  906  (e.g., a tissue-contacting layer) formed of first fibers  908 , a bottom layer  910  (e.g., a cartridge-contacting layer) formed of second fibers  912 , and spacer fibers  914  that are intertwined with and that extend between the top and bottom layers  906 ,  910  to thereby connect the top and bottom layers  906 ,  910  together. As shown in  FIG.  9 A , the top layer  906  has at least two outer-most longitudinal terminal edges  906   a ,  906   b  and at least two outer-most lateral terminal edges  906   c ,  906   d . The bottom layer  910  has at least two outer-most longitudinal terminal edges (only one outer-most longitudinal terminal edge  910   b  being illustrated in  FIG.  9 A ) and at least two outer-most lateral terminal edges  910   c ,  910   d.    
     In addition to the first and second outer-most segments  915 ,  916  (see  FIG.  9 A ), which are similar to the first and second outer-most segments  822 ,  824  in  FIGS.  8 A- 8 B , the adjunct  900  includes third and fourth outer-most segments  918 ,  920  (see  FIG.  9 B ). The third and fourth outer-most segment  918 ,  920  are positioned on opposite sides (e.g., lateral sides) of the inner-most segment  922  and extend orthogonal (e.g., in the y-direction) to the longitudinal axis L A  of the adjunct (e.g., extending the z-direction). Aside from their position within the adjunct  900 , the third and fourth outer-most segments  918 ,  920  are structurally similar to the first and second outer-most segments  915 ,  916 . 
     Further, in addition to the first and second intermediate segments  924 ,  926  (see  FIG.  9 A ), which are similar to the first and second intermediate segments  826 ,  828  in  FIGS.  8 A- 8 B , the adjunct  900  includes third and fourth intermediate segments  928 ,  930  (see  FIG.  9 B ). As shown, the third intermediate segment  928  extends from the inner-most segment  922  to the third outer-most segment  918  and the fourth intermediate segment  930  extends from the inner-most segment  922  to the fourth outer-most segment  920 . Aside from their position within the adjunct  900 , the third and fourth intermediate segments  928 ,  930  are structurally similar to first and second intermediate segments  924 ,  926 . 
     As further shown in  FIGS.  9 A- 9 B , the adjunct  900  includes first, second, third, and fourth additional fibers  932 ,  934 ,  936 ,  938  that form respective first, second, third, and fourth finished edges  940 ,  942 ,  944 ,  946  that are configured to prevent fraying of the top and bottom layers  906 ,  910  therealong, and thus fraying and/or fiber separation of the first fibers  908  and the second fibers  912 . Each additional fiber  932 ,  934 ,  936 ,  938  can be incorporated into the adjunct in a variety of ways to form respective finished edges  940 ,  942 ,  944 ,  946 . The first and second finished edges  940 ,  942  are similar to first and second finished edges  834 ,  836  in  FIGS.  8 A- 8 B  and therefore not described in detailed herein. 
     The third and fourth additional fibers  936 ,  938  can be incorporated into the adjunct  900  in a variety of ways to form the third and fourth finished edges  944 ,  946 . In this illustrated embodiment, the third additional fiber  936  interconnects the top and bottom layers  906 ,  910  along their first outer-most lateral terminal edges  906   c ,  910   c  to form the third finished edge  944 . As a result, the third finished edge  944  is formed of the first fibers  908 , the second fibers  912 , and the third additional fiber  936  and is positioned along, and thus defines, at least a portion of a first outer-most lateral edge  948  of the adjunct  900 . The fourth additional fiber  938  interconnects the top and bottom layers  906 ,  910  along their respective second outer-most lateral terminal edges  906   d ,  910   d  to form the fourth finished edge  946 . As a result, the fourth finished edge  946  is formed of the first fibers  908 , the second fibers  912 , and the fourth additional fiber  938  and is positioned along, and thus defines, at least a portion of a second outer-most lateral edge  950  of the adjunct  900 . Thus, at least a portion of the outer-most perimeter of the adjunct  900  is defined by the first, second, third, and fourth finished edges  940 ,  942 ,  944 ,  946 . In certain embodiments, for example, as shown in  FIG.  9 A , the outer-most perimeter of the adjunct  900  can be entirely defined by finished edges. 
     Further, the third additional fiber  936  and/or the fourth additional fiber  938  can be configured as an overcast stitch. For example, as shown, the third additional fiber  936  and the fourth additional fiber  938  are wrapped around the first outer-most lateral terminal edges  906   c ,  910   c  and the second outer-most lateral terminal edges  906   d ,  910   d , respectively, in the form of loops (e.g., in a spiral-type configuration). As a result, the portion of free ends of the first and second fibers  908 ,  912  at the first outer-most lateral terminal edges  906   c ,  910   c  are secured together by the third additional fiber  936  and the portion of free ends of the first and second fibers  908 ,  912  at the second outer-most lateral terminal edges  906   d ,  910   d  are secured together by the fourth additional fiber  938 . In other embodiments, the third and fourth additional fibers  936 ,  938  can be configured as other suitable stitch forms. Further, in certain embodiments, the third and fourth additional fibers  936 ,  938  can be configured as different stitch forms. 
     Alternatively, or in addition, the adjunct can include inner-most longitudinal terminal edge(s) relative to its outer-most longitudinal terminal edges (e.g., first and second outer-most longitudinal terminal edges  806   a ,  806   b ,  810   a ,  810   b  in  FIGS.  8 A- 8 B ). In such embodiments, the adjunct can include additional fibers that are incorporated into the adjunct such that finished edge(s) can also be formed along, and thus define, at least a portion of the inner-most longitudinal terminal edge(s). For example. an adjunct can include inner-most longitudinal terminal edges that are configured to border a longitudinal slot, like longitudinal slot  210  in  FIGS.  2 A- 2 C , of a staple cartridge. In such embodiments, the adjunct can include at least one bridging element that extends between and tethers spaced apart portions of the adjunct together (e.g., portions that are configured to be positioned on opposite sides of the longitudinal slot when the adjunct is coupled to the cartridge). In certain embodiments, the at least one bridging element can be designed to overlap with at least a portion of a cut-line of the adjunct, and thus at least a portion of the longitudinal slot. As a result, the at one least bridging element is severed by the advancement of the cutting element through the longitudinal slot. 
     In some embodiments, the at least one bridging element can include two or more bridging elements that are spaced apart relative to each other to provide discrete attachments between portions of the adjunct. In embodiments where such portions are configured to be positioned on opposite sides of the longitudinal slot of the cartridge, the discrete attachments can reduce the amount of adjunct material positioned within the advancement path of the cutting element. This material reduction can help to minimize the resistance of the adjunct to the advancement of the cutting element which, among other things, can improve the life of the cutting element and/or reduce the force required to advance the cutting element through the adjunct. In certain embodiments, the at least one bridging element can be formed of a portion of at least one of the top and bottom layers of the adjunct, whereas in other embodiments, the at least bridging element can be formed of separate material. Alternatively, one or more of the at least one bridging element can be positioned outside the advancement path of the cutting element, and thus, can continue to tether the portions of the adjunct after the cutting element is advanced through the longitudinal slot. 
       FIGS.  10 A- 10 D  show another exemplary embodiment of a stapling assembly  1000  having a staple cartridge  1002  and a knitted adjunct  1004  that is disposed on a top or deck surface  1003  of the staple cartridge  1002  and that has one or more finished edges. The staple cartridge  1002  is similar to staple cartridge  200  in  FIGS.  1 - 2 C , and therefore common features are not described in detail herein. Further, aside from the differences described below, the adjunct  1004  is similar to adjunct  804  in  FIGS.  8 A- 8 B , and therefore common features are not described in detail herein. 
     The adjunct  1004  can have a variety of configurations. For example, in this illustrated embodiment, the adjunct  1004  includes first and second longitudinal portions  1006 ,  1008 , each having a respective top layer  1010 ,  1012  (e.g., a tissue-contacting layer) formed of first fibers  1014 , a bottom layer  1016 ,  1018  (e.g., a cartridge-contacting layer) formed of second fibers  1020 , and spacer fibers  1022  that are intertwined with and that extend between the respective top and bottom layers  1010 ,  1012 ,  1016 ,  1018  to thereby connect the top and bottom layers. The top and bottom layers  1010 ,  1012  are similar in structure to the top and bottom layers  806 ,  810  in  FIGS.  8 A- 8 B  and the spacer fibers  1022  are similar to the spacer fibers  814  in  FIGS.  8 A- 8 B , and therefore comment features are not described in detail herein. Further, at least of a portion of the fibers in the first longitudinal portion  1006  can be the same or different than at least a portion of the fibers of the second longitudinal portion  1008 . In this illustrated embodiment, the first fibers  1014  in the first and second longitudinal portions  1006 ,  1008  are the same type of fibers, the second fibers  1020  in the first and second longitudinal portions  1006 ,  1008  are the same type of fibers, and the spacer fibers  1022  in the first and second longitudinal portions  1006 ,  1008  are the same type of fibers. 
     The first and second longitudinal portions  1006 ,  1008  can each include additional fibers that form a respective finished edge configured to prevent fraying of the respective top and bottom layers  1010 ,  1012  therealong, and thus fraying and/or fiber separation of the first fibers  1014  and the second fibers  1020 . As shown in greater detail in  FIG.  10 B , the first longitudinal portion  1006  includes eight additional third fibers  1024   a ,  1024   b ,  1024   c ,  1024   d ,  1024   e ,  1024   f ,  1024   g ,  1024   h , and the second longitudinal portion  1008  includes eight additional fourth fibers  1026   a ,  1026   b ,  1026   c ,  1026   d ,  1026   e ,  1026   f ,  1026   g ,  1026   h . Consequently, the first longitudinal portion  1006  includes finished edges  1028   a ,  1028   b ,  1028   c ,  1028   d ,  1028   e ,  1028   f ,  1028   g ,  1028   h , and the second longitudinal portion  1008  includes finished edges  1030   a ,  1030   b ,  1030   c ,  1030   d ,  1030   e ,  1030   f ,  1030   g ,  1030   h . While the first and second longitudinal portions  1006 ,  1008  are each illustrated as having eight additional third and fourth fibers  1024   a ,  1024   b ,  1024   c ,  1024   d ,  1024   e ,  1024   f ,  1024   g ,  1024   h ,  1026   a ,  1026   b ,  1026   c ,  1026   d ,  1026   e ,  1026   f ,  1026   g ,  1026   h , respectively, and consequently eight respective finished edges  1028   a ,  1028   b ,  1028   c ,  1028   d ,  1028   e ,  1028   f ,  1028   g ,  1028   h ,  1030   a ,  1030   b ,  1030   c ,  1030   d ,  1030   e ,  1030   f ,  1030   g ,  1030   h , a person skilled the art will appreciate that the amount of additional fibers can depend at least upon the size and shape of the staple cartridge and/or anvil to which the adjunct will be applied, and therefore, the first and second longitudinal portions  1006 ,  1008  are not limited to the number of additional fibers illustrated in the figures. 
     The additional third and fourth fibers  1024   a ,  1024   b ,  1024   c ,  1024   d ,  1024   e ,  1024   f ,  1024   g ,  1024   h ,  1026   a ,  1026   b ,  1026   c ,  1026   d ,  1026   e ,  1026   f ,  1026   g ,  1026   h  can have a variety of configurations. In some embodiments, two or more of the additional fibers can be generally identical (nominally identical within manufacturing tolerances) in compositional makeup (e.g., formed of the same material(s)), dimension(s) (e.g., height and/or diameter), and/or in structural configuration (e.g., monofilament or multifilament). In certain embodiments, at least one of the additional fibers can be a monofilament fiber. Alternatively, or in addition, at least one of the additional fibers can be a multifilament fiber. In one embodiment, one portion of the additional fibers are monofilament fibers and the other portion is multifilament fibers. As such, aside from the general overall shape, the specific structural configuration of each of the additional third and fourth fibers  1024   a ,  1024   b ,  1024   c ,  1024   d ,  1024   e ,  1024   f ,  1024   g ,  1024   h ,  1026   a ,  1026   b ,  1026   c ,  1026   d ,  1026   e ,  1026   f ,  1026   g ,  1026   h  is not shown. 
     Further, as shown, the additional third fibers  1024   a ,  1024   b ,  1024   c ,  1024   d ,  1024   e ,  1024   f ,  1024   g ,  1024   h  are similar in structure and stitch form to the additional fourth fibers  1026   a ,  1026   b ,  1026   c ,  1026   d ,  1026   e ,  1026   f ,  1026   g ,  1026   h , and therefore for sake of simplicity, the following description is with respect to the additional third fibers  1024   a ,  1024   b ,  1024   c ,  1024   d ,  1024   e ,  1024   f ,  1024   g ,  1024   h . A person skilled in the art will understand, however, that the following discussion is also applicable to the additional fourth fibers  1026   a ,  1026   b ,  1026   c ,  1026   d ,  1026   e ,  1026   f ,  1026   g ,  1026   h.    
     The additional third fibers  1024   a ,  1024   b ,  1024   c ,  1024   d ,  1024   e ,  1024   f ,  1024   g ,  1024   h  can be incorporated into the first longitudinal portion  1006  in a variety of ways to form respective finished edges  1028   a ,  1028   b ,  1028   c ,  1028   d ,  1028   e ,  1028   f ,  1028   g ,  1028   h . In this illustrated embodiment, as shown in more detail in  FIG.  10 C , the first additional third fiber  1024   a  is configured as an overcast stitch and interconnects the top and bottom layers  1010 ,  1016  along their first outer-most longitudinal terminal edges  1010   a ,  1016   a  to form the first finished edge  1028   a . As a result, the first finished edge  1028   a  of the first longitudinal portion  1006  is formed of the first fibers  1014 , the second fibers  1020 , and the first additional third fiber  1024   a  and is positioned along, and thus defines, at least a portion of an outer-most longitudinal edge  1032  of the first longitudinal portion  1006 . Each remaining additional third fiber  1024   b ,  1024   c ,  1024   d ,  1024   e ,  1024   f ,  1024   g ,  1024   h  is also configured as an overcast stitch and interconnects the top and bottoms layers  1010 ,  1016  along a respective portion of a second outer-most longitudinal terminal edge  1010   b ,  1014   b  of the top and bottom layers  1010 ,  1016  to form respective and discrete finished edges  1028   b ,  1028   c ,  1028   d ,  1028   e ,  1028   f ,  1028   g ,  1028   h . As a result, each remaining finished edge  1028   b ,  1028   c ,  1028   d ,  1028   e ,  1028   f ,  1028   g ,  1028   h  is formed of the first fibers  1014 , the second fibers  1020 , and respective additional third fiber  1024   b ,  1024   c ,  1024   d ,  1024   e ,  1024   f ,  1024   g ,  1024   h , and is positioned along, and thus defines, a respective portion of an inner-most longitudinal edge  1034  of the first longitudinal portion  1006 . 
     As further shown, the adjunct  1004  includes bridging elements  1036   a ,  1036   b ,  1036   c ,  1036   d ,  1036   e ,  1036   f  that extend between and connect the first and second longitudinal portions  1006 ,  1008  of the adjunct  1004  together. While the adjunct  1004  is illustrated as having six bridging elements  1036   a ,  1036   b ,  1036   c ,  1036   d ,  1036   e ,  1036   f , a person skilled the art will appreciate that the number and structural configuration of the bridging element(s) of the adjunct can depend at least upon the size and shape of the staple cartridge and/or anvil to which the adjunct will be applied and/or the size and shape of a longitudinal slot (e.g., a knife slot) within the cartridge, and therefore, the adjunct  1004  is not limited to the number and/or structural configuration of the bridging elements illustrated in the figures. 
     The bridging elements  1036   a ,  1036   b ,  1036   c ,  1036   d ,  1036   e ,  1036   f  can have a variety of configurations. For example, in illustrated embodiment, discrete portions of the first and second fibers  1014 ,  1020  extend between the first and second longitudinal portions  1006 ,  1008 , and as a result, these portions serve as the bridging elements  1036   a ,  1036   b ,  1036   c ,  1036   d ,  1036   e ,  1036   f . This creates a centralized zone  1040  within the adjunct that is formed of only the first and second fibers  1014 ,  1020 . This results in a lesser amount of material along the cut-line of the adjunct compared to the other portions of the adjunct. In some embodiments, a portion of the spacer fibers can be present within the centralized zone (e.g., the spacer fiber density within the centralized zone is less than the spacer fiber densities within other portions of the adjunct). 
     As shown in  FIGS.  10 A- 10 D , when the adjunct  1004  is releasably secured to the cartridge  1002 , the first longitudinal portion  1006  is positioned on a first side of the longitudinal slot  1007  of the cartridge  1002  and the second longitudinal portion  1008  is positioned on a second, opposite side of the longitudinal slot  1007 . With respect the first longitudinal portion  1006 , the first finished edge  1028   a  is positioned proximate to and along a portion of a first outer-most longitudinal edge  1005   a  of the top surface  1003  of the cartridge  1002 , and each of the remaining finished edges  1028   b ,  1028   c ,  1028   d ,  1028   e ,  1028   f ,  1028   g ,  1028   h  are positioned proximate to and along a respective portion of a first slot edge  1007   a  of the longitudinal slot  1007 . Similarly, with respect to the second longitudinal portion  1008 , the first finished edge  1030   a  is positioned proximate to and along a portion of a second outer-most longitudinal edge  1005   b  of the top surface  1003  of the cartridge  1002 , and each of the remaining finished edges  1030   b ,  1030   c ,  1030   d ,  1030   e ,  1030   f ,  1030   g ,  1030   h  are positioned proximate to and along a respective portion of a second slot edge  1007   b  of the longitudinal slot  1007 . Further, as shown in more detail in  FIGS.  10 B and  10 D , the bridging elements at least partially overlap with the longitudinal slot  1007  of the cartridge  1002 . 
     While not shown in  FIGS.  10 A- 10 D , in certain embodiments, the adjunct can also include one or more attachment features that extend at least partially along the length of adjunct (e.g., extending in the z-direction) and that are configured to engage the staple cartridge to thereby retain the adjunct on the cartridge prior to staple deployment. The one or more attachment features can have a variety of configurations. For example, the one or more attachment features can be channel attachments that are configured to engage (e.g., press-fit or snap into) the longitudinal slot (e.g., knife slot) formed between opposing longitudinal slot edges in the staple cartridge. 
     In other embodiments, instead of incorporating additional fiber(s) into the adjunct (e.g., additional fibers  830 ,  832  in  FIGS.  8 A- 8 B ) for creating one or more finished edges of the adjunct, the existing fibers of the adjunct (e.g., first fibers  1102 , second fibers  1104 , and spacer fibers  1106  in  FIGS.  11 A- 11 B ) can be intertwined together. Alternatively, or in addition, heat can be applied to at least a portion of the existing fibers. For example, a hot blade could be used to melt, and thus fuse, at least a portion of the existing fibers, e.g., along at least a portion of the perimeter of the adjunct. This can avoid the need for additional material (e.g., additional fiber(s) other than the fibers needed to form the top, bottom, and core layers of the adjunct), and thus, among other things, can decrease the overall material cost and/or manufacturing cost of the adjunct. 
       FIGS.  11 A- 11 B  is one exemplary embodiment of a knitted adjunct  1100  having at least one finished edge formed of fibers that also form other portions of the adjunct. In this illustrated embodiment, the adjunct  1100  includes first fibers  1102 , second fibers  1104 , and spacer fibers  1106  that are intertwined to form a top layer  1110  (e.g., a tissue-contacting layer), a bottom layer  1112  (e.g., a cartridge-contacting layer), and at least one finished edge (only three finished edges  1114   a ,  1114   b ,  1114   c  are illustrated) extending between the top and bottom layers  1110 ,  1112 . For sake of simplicity, only one first fiber  1102 , second fiber  1104 , and spacer fiber  1106  is illustrated in  FIG.  11 B . A person skilled in the art will appreciate that the following discussion is also applicable to the remaining first, second, and spacer fibers of the adjunct. 
     The first fibers  1102 , the second fibers  1104 , and the spacer fibers  1106  can have a variety of configurations. For example, in some embodiments, the first fibers  1102 , the second fibers  1104 , and the spacer fibers  1106  can be generally identical (e.g., nominally identical within manufacturing tolerances) in compositional makeup (e.g., formed of the same material(s)), dimension(s) (e.g., height and/or diameter), and/or in structural configuration (e.g., monofilament or multifilament), whereas in other embodiments, they can be different. In certain embodiments, the first and second fibers  1102 ,  1104  can be generally identical (e.g., nominally identical within manufacturing tolerances) and the spacer fibers  1106  can be different. For example, in certain embodiments, the first and second fibers  1102 ,  1104  are multifilament fibers, and the spacer fibers  1106  are monofilament fibers. As such, aside from the general overall shape, the specific structural configuration of each of the first fibers  1102 , the second fibers  1104 , and the spacer fibers  1106  is not shown. 
     The top and bottom layers  1110 ,  1112  can have a variety of structural configurations. As shown in more detail in  FIG.  11 B , the first fibers  1102  and the spacer fibers  1106  are intertwined to form the top layer  1110  and the second fibers  1104  and the spacer fibers  1106  are intertwined to form the bottom layer  1112 . Thus, in this illustrated embodiment, the first fibers  1102  are not present in the bottom layer  1112  and the second fibers  1104  are not present in the top layer  1110 . In other embodiments, at least a portion of the first fibers  1102  can be present within the bottom layer  1112  and/or at least a portion of the second fibers  1104  can be present within the top layer  1110 . 
     In some embodiments, the first fibers  1102  of the top layer  1110  and/or second fibers  1104  of the bottom layer  1112  can be knitted in a respective predetermined pattern. In certain embodiments, the predetermined pattern of the first fibers  1102  within the top layer  1110  and the predetermined pattern of the second fibers  1104  of the bottom layer  1112  can be generally identical (e.g., nominally identical within manufacturing tolerances), whereas in other embodiments, the predetermined patterns can be different. While the first fibers  1102  of the top layer  1110  and the second fibers  1104  of the bottom layer  1112  can each be knitted in various patterns, in certain embodiments, the first fibers  1102  can be knitted into a first Raschel knit pattern and the second fibers  1104  can be knitted into a second Raschel knit pattern that is the same or different than the first Rachel knit pattern. Further, in some embodiments, the fiber density of the top layer  1110  can be different than the fiber density of the bottom layer  1112 . A person skilled in the art will appreciate that the first fibers  1102  and the second fibers  1104  can be randomly or repeatedly knitted or woven within the top and bottom layers  1110 ,  1112 , respectively. As such, and for sake of simplicity, the top and bottom layers  1110 ,  1112  are generally illustrated, and thus the specific structural configurations of the top and bottom layers  1110 ,  1112  are not limited to what is depicted in the figures. 
     The portions of the spacer fibers  1106  that extend between the top and bottom layers  1110 ,  1112  can form an intermediate layer  1116 , and thus, are positioned between the top and bottom layers  1110 ,  1112 . While these portions can have a variety of configurations, in this illustrated embodiment, as shown in  FIG.  11 B , they are arranged in such a manner that form standing fibers  1118 . The standing fibers  1118  can be configured to bend or compress in response to force being applied to the adjunct  1100 . 
     The standing fibers  1118  can have a variety of orientations within the intermediate layer. For example, in some embodiments, as shown in  FIG.  11 B , the standing fibers  1118  have a general columnar configuration, meaning they are generally oriented in adjacent columns. In other embodiments, the standing fibers  1118  can be angled or slanted to favor an organized collapse or bend in a first direction in response to force(s) applied to the adjunct (e.g., compressive forces through tissue (T) positioned against the top layer  1110 ). Alternatively, the standing fibers  1118  can be angled or slanted to favor an organized collapse in a second direction opposite the first direction in response to the applied force(s). Alternatively, the standing fibers  1118  can include a first group that are angled or slanted to favor bending in the first direction and a second group of the standing fibers that are angled or slanted to favor bending in the second direction. 
     As further shown in  FIGS.  11 A- 11 B , the adjunct  1100  includes four finished edges (only three finished edges  1114   a ,  1114   b ,  1114   c  are illustrated) in which each finished edge extends between the top and bottom layers  1110 ,  1112 . Further, one or more of the finished edges  1114   a ,  1114   b ,  1114   c  can be positioned at least partially along, and thus at least partially define, an outer-edge of the adjunct  1100 . For example, in this illustrated embodiment, the adjunct  1100  has four outer-most edges (only three outer-most edges  1120   a ,  1120   b ,  1120   c ) in which the first finished edge  1114   a  is positioned entirely along the first outer-most edge  1120   a , the second finished edge  1114   b  is positioned entirely along the second outer-most edge  1120   b , the third finished edge  1114   c  is positioned entirely along the third outer-most edge  1120   c , and the fourth finished edge (obstructed) is positioned entirely along the fourth outer-most edge (obstructed). As a result, the four finished edges define the entire outer-most perimeter of the adjunct  1100 . 
     Each finished edge is formed of respective portions of the first fibers  1102 , the second fibers  1104 , and the spacer fibers  1106 . The first fibers  1102 , the second fibers  1104 , and the spacer fibers  1106  can interact in a variety of ways to effect the finished edges. In this illustrated embodiment, each finished edge is structurally similar and includes respective portions of the first fibers, the second fibers, and the spacer fibers intertwined together. While only the first and second finished edges are illustrated in detail, a person skilled in the art will appreciate the following discussion is also applicable to the third finished edge  1114   c  and the fourth finished edge. 
     As shown in greater detail in  FIG.  11 B , the first finished edge  1114   a  includes a first portion  1122   a  of the first fibers  1102 , a first portion  1124   a  of the second fibers  1104 , and a first portion  1126   a  of the spacer fibers  1106  that are intertwined together. In addition, the free ends  1128   a  of the first portion  1122   a  of the first fibers  1102 , the free ends  1130   a  of the first portion  1124   a  of the second fibers  1104 , and the free ends  1132   a  of the first portion  1126   a  of the spacer fibers  1106  can be knotted together, as shown in  FIG.  11 B . Similarly, as shown in  FIG.  11 B , the second finished edge  1114   b  includes a second portion  1122   b  of the first fibers  1102 , a second portion  1124   b  of the second fibers  1104 , and a second portion  1126   b  of the spacer fibers  1106  that are intertwined together. In addition, the free ends  1128   b  of the second portion  1122   b  of the first fibers  1102 , the free ends  1130   b  of the second portion  1124   b  of the second fibers  1104 , and the free ends  1132   b  of the second portion  1126   b  of the spacer fibers  1106  can be knotted together, as shown in  FIG.  11 B . 
     While not shown, in certain embodiments, the adjunct  1100  can also include additional finished edge(s) that are configured to be positioned adjacent to and along a respective slot edge of a longitudinal slot formed within a cartridge to which the adjunct is intended to be releasably attached thereto. In such embodiments, for example, at least one additional finished edge can be formed of respective portions of the first fibers  1102 , the second fibers  1104 , and the spacer fibers  1106 . 
     While the adjuncts  804 ,  900 ,  1004  in  FIGS.  8 A- 10 D  each include finished edges that are formed by additional fibers, and the adjunct  1100  in  FIGS.  11 A- 11 B  includes finished edges that are formed by existing fibers, in other embodiments, an adjunct can have a combination of different types of finished edges. For example, in certain embodiments, an adjunct can have at least one finished edge that is formed by an additional fiber(s) (e.g., first finished edge  34  in  FIG.  8 B ) and at least one finished edge that is formed by a portion of existing fibers otherwise present in the adjunct (e.g., first finished edge  1114   a  in  FIGS.  11 A- 11 B ). 
     Alternatively, or in addition, the adjunct can include an absorbable film that is disposed over at least a portion of a tissue-facing surface of an outer layer and/or inner layer. The absorbable film can substantially protect the fibers of the underlying layer(s) from being exposed to forces that would otherwise lead to fraying, pulling, and/or separating. For example, in certain embodiments, an absorbable film can be used to form at least a portion of one or more finished edges of the adjunct. Further, the absorbable film can substantially prevent tissue from causing the adjunct to prematurely detach from the cartridge while the tissue slides across the adjunct. That is, the absorbable film can minimize edge conditions, and thus decrease the friction that would otherwise be present on the tissue-contacting surface(s) of the adjunct. 
     The absorbable film can have a variety of configurations. In some embodiments, the absorbable film can have a thickness that is less than or equal to about 15 microns, e.g., from about 5 microns to 15 microns, or from about 8 microns to 11 microns. In one embodiment, the absorbable film can be formed of polydioxanone. The absorbable film can be attached to a knitted structure in a variety of ways. For example, in one embodiment, the absorbable film can be attached by heating the film (e.g., equal to or above a glass transition temperature of the film material) and then pressing the film onto the knitted structure to thereby create a bond therebetween. Alternatively, at least a portion of the knitted structure (e.g., a portion of the fibers of the bottom layer) can be heated (e.g., above 85° C.) and then pressed against the film. 
       FIG.  12    illustrates one exemplary embodiment of a stapling assembly  1200  that includes a staple cartridge  1202  and a knitted adjunct  1204  disposed on a top or deck surface  1203  of the cartridge  1202 . The staple cartridge  1202  is similar to staple cartridge  200  in  FIGS.  1 - 2 C , and therefore common features are not described in detail herein. 
     The adjunct  1204  includes a knitted structure  1206  with an absorbable film  1208  disposed on at least a portion thereof. The knitted structure includes a top layer  1210 , a bottom layer  1212 , and a core layer  1214  extending therebetween. The top layer  1210 , the bottom layer  1212 , and the core layer  1214  are similar to the top layer  1110 , the bottom layer  1112 , and the intermediate layer  1116  in  FIGS.  11 A- 11 B , and therefore common features are not described herein. As shown, the absorbable film  1208  is disposed on all tissue-facing surfaces of the knitted structure  1206 , which, in this illustrated embodiment, includes a top-tissue facing surface  1216  (e.g., extending in the YZ plane), a first longitudinal side surface  1218   a  (e.g., extending in the XZ plane), a second opposing longitudinal side surface  1218   b , a first lateral side surface  1220   a  (e.g., extending in the XY plane), and a second opposing lateral side surface (obstructed). In other embodiments, the absorbable film is not disposed on all tissue-facing surfaces of the knitted structure, e.g., the first lateral side surface and/or the second lateral side surface. 
     Attachment Features 
     In general, the knitted adjuncts described herein are designed and positioned atop a staple cartridge for use in a stapling procedure. When the staples are fired (deployed) from the cartridge, the staples penetrate through the adjunct and into tissue. Prior to the adjunct being penetrated by the staples, the adjunct may become dislodged or misaligned from the staple cartridge. That is, when the staple cartridge is being placed into position, the adjunct may be dislodged by coming into contact with a portion of a surgical site. In order to keep the adjunct aligned and secured on the staple cartage prior to firing the staples, one or more surfaces features may be arranged within the adjunct. The one or more surface features (e.g., one or more recesses) may be woven, thermoformed, or mechanically positioned within the adjunct. 
     As discussed above, the knitted adjuncts are formed of fibers that are knitted or woven together. In certain embodiments, the adjuncts can be designed such that one or more surface features can be formed within the adjunct. The one or more surface features are configured to substantially, or completely, align and secure the adjunct to the cartridge deck prior to staple deployment. As a result, the adjunct can remain secured to the cartridge deck when exposed to forces that would otherwise cause the adjunct to separate from the cartridge deck prior to stapling of the adjunct to tissue. The one or more surface features can also decrease the likelihood of misalignment of the adjunct prior to stapling, as compared to conventional adjuncts (e.g., adjuncts without one or more surface features). 
     The one or more surface features can be formed in a variety of ways. For example, in some embodiments, the surface features can be created in the adjunct after fabrication. For example, using a solvent, a knitting operation, a heat operation, a die cutting operation, a laser cutting operation, an ultrasonic cutting operation, a stamping or punching operation (e.g., a mechanical pressing), or a combination of these techniques. In some embodiments, the surface features can be knitted into the bottom-most layer (e.g., cartridge-contacting layer) of the adjunct. In other embodiments, the surface features can be thermoformed in the adjunct using a heated mold. Alternatively, or in addition to, the surface features can be thermoformed in the adjunct by heating the stapling cartridge and positioning the adjunct onto the heated cartridge deck so that the adjunct conforms to the shape of the cartridge deck, including any one or more attachment features (e.g., projections) of the cartridge deck. 
     In some embodiments, the one or more surface features can have a minimum diameter that is smaller than the diameter of the staple legs. Alternatively, or in addition, the one or more surface features a can have maximum diameter that is greater than the circumference (e.g., outer diameter) of the one or more attachment features of the cartridge to form a friction or press-fit. In certain embodiments, the one or more surface features can be sized so as to receive two or more attachment features of the cartridge. 
       FIG.  13 A  illustrates a portion of another exemplary embodiment of a stapling assembly  1300  that includes a knitted adjunct  1302  disposed on a top or deck surface  1306  of a staple cartridge  1304 , with  FIG.  13 B  illustrating the adjunct and the cartridge prior to being releasably coupled together. The adjunct  1302  includes a first knitted layer  1308  (e.g., a top or tissue-contacting layer) formed of at least first fibers  1310 , a second knitted layer  1312  (e.g., a bottom or cartridge-contacting layer) formed of at least second fibers  1314 , and spacer fibers  1316  intertwined with and extending between the first and second knitted layers  1308 ,  1312  to thereby connect the first and second knitted layers  1308 ,  1312  together. The portions of the spacer fibers  1316  that extend between the first and second knitted layers  1308 ,  1312  form a core layer  1318  of the adjunct  1302 . For sake of simplicity, only one first fiber  1310 , second fiber  1314 , and spacer fiber  1316  is being illustrated. A person skilled in the art will appreciate that the following discussion is also applicable to the remaining first, second, and spacer fibers of the adjunct. 
     In some embodiments, the first fibers  1310  of the first knitted layer  1308  can be knitted or woven into a first predetermined pattern and/or the second fibers  1314  of the second knitted layer  1312  can be knitted or woven into a second predetermined pattern. In certain embodiments, the first and second predetermined patterns can be generally identical (e.g., nominally identical within manufacturing tolerances), whereas in other embodiments, the first and second predetermined patterns can be different. Further, in some embodiments, the fiber density of the first knitted layer  1308  can be different than the fiber density of the second knitted layer  1312 . While the first fibers  1310  and the second fibers  1314  can be knitted or woven in various patterns, in certain embodiments, the first fibers  1310  can be knitted into a first Raschel knit pattern and the second fibers  1314  can be knitted into a second Raschel knit pattern that is the same or different than the first Raschel knit pattern. A person skilled in the art will appreciate that the first fibers  1310  and the second fibers  1314  can be randomly or repeatedly knitted or woven within the first and second knitted layers  1308 ,  1312 , respectively. As such, and for sake of simplicity, the first and second knitted layers  1308 ,  1312  are generally illustrated, and thus the specific structural configurations of the first and second knitted layers  1308 ,  1312  are not limited to what is depicted in the figures. 
     The first fibers  1310 , the second fibers  1314 , and the spacer fibers  1316  can have a variety of configurations. For example, in some embodiments, the first fibers  1310 , the second fibers  1314 , and the spacer fibers  1316  can be generally identical (e.g., nominally identical within manufacturing tolerances) in compositional makeup (e.g., formed of the same material(s)), dimension(s) (e.g., height and/or diameter), and/or in structural configuration (e.g., monofilament or multifilament), whereas in other embodiments they are different. In other embodiments, the first and second fibers  1310 ,  1314  can be generally identical (e.g., nominally identical within manufacturing tolerances) and the spacer fibers  1316  can be different. For example, in certain embodiments, the first and second fibers  1310 ,  1314  can be multifilament fibers, and the spacer fibers  1316  can be monofilament fibers. As such, aside from the general overall shape, the specific structural configuration of each of the first fibers  1310 , the second fibers  1314 , and the spacer fibers  1316  is not shown. 
     As further shown in  FIG.  13 B , which the adjunct includes one or more surface features formed within the second knitted layer  1312 , which in this illustrated embodiment are in the form of recesses (only two recesses  1322   a ,  1322   b  are being illustrated). The one or more recesses are configured to receive and engage respective attachment features of the cartridge  1304 , as shown in  FIG.  13 A , which in this illustrated embodiment are in the form of projections  1324   a ,  1324   b  that each extend outward from the top or deck surface  1306  of the cartridge  1304 . The recesses  1322   a ,  1322   b  can be formed by manipulating portions of the second fibers  1314  within the second knitted layer  1312  (e.g., melting or further knitting). In this illustrated embodiment, the perimeter of the recesses  1322   a ,  1322   b  are defined by melted portions of the second fibers  1314 . 
     The recesses  1322   a ,  1322   b  and projections  1324   a ,  1324   b  can have variety of configurations. For example, in this illustrated embodiment, the recesses  1322   a ,  1322   b  have an inverted conical-shape, and therefore a varying diameter that decreases as the recesses  1322   a ,  1322   b  extends into the second knitted layer  1312 . As such, each recess  1322   a ,  1322   b  extends from a maximum diameter X 1a , X 2a  to a minimum diameter X 1b , X 2b . Further, the projections  1324   a ,  1324   b  have a conical-shaped with a varying diameter that decreases as the projections  1324   a ,  1324   b  extend outward from the top or deck surface  1306 . As such, each projection extends  1324   a ,  1324   b  from a maximum diameter X 1c , X 1c  to a minimum diameter X 2c , X 2d . While the recesses  1322   a ,  1322   b  and projections  1324   a ,  1324   b  are illustrated as having complementary conical-shapes, a person skilled in the art will appreciate that the recesses can have other complementary shapes, such as squares, half-circles, triangles, etc. Further, while the recesses  1322   a ,  1322   b  are illustrated as being generally uniform (e.g., uniform within manufacturing tolerances), in other embodiments, at least a portion of the recesses can differ. 
     The difference between the maximum diameters X 1a , X 1b  and the maximum diameters X 2a , X 2b  can allow for a friction fit to be formed between the recesses  1322   a ,  1322   b  and the projections  1324   a ,  1324   b . In this illustrated embodiment, the maximum diameters of the recesses  1322   a ,  1322   b  are smaller than the maximum diameters of the projections  1324   a ,  1324   b  prior to the engagement. As a result, an interference fit can be created between the portions of the second fibers  1314  that contact the projections  1324   a ,  1324   b . This friction force can aid in securing the adjunct  1302  to the staple cartridge  1304 . In other embodiments, the maximum diameters of the recesses  1322   a ,  1322   b  can be larger than the maximum diameters of the projections  1324   a ,  1324   b  prior to the engagement. 
     Further, while not shown, the minimum diameters X 1a , X 1b  of the recesses  1322   a ,  1322   b  within the adjunct  1302  can be smaller than the diameter of staple legs (e.g. maximum diameter of the wire that forms the staple legs) that at least partially disposed within the staple cartridge  1304 . As a result, when the adjunct  1302  is releasably coupled to the cartridge  1304 , and the recesses  1322   a ,  1322   b  are also configured to overlap with the staple cavities of the cartridge  1304 , like staple cavities  212 ,  214  in  FIGS.  2 A- 2 C , the portions of the staple legs extending beyond the top or deck surface  1306  of the cartridge  1304  can also engage the recesses of the adjunct  1302 . This can also create a friction fit therebetween and further secure the adjunct to the staple cartridge prior to staple deployment. 
     As further shown in  FIG.  13 B , due to the spaced apart arrangement of the recesses  1322   a ,  1322   b  in the second knitted layer  1312 , a projection  1326  is formed between the recesses  1322   a ,  1322   b  with a maximum diameter of D 1 . Additionally, due to the spaced arrangement of the projections  1324   a ,  1324   b  on the top surface  1306  of the cartridge  1304 , a complementary recess  1328  is formed between the projections  1326   a ,  1326   b  with a maximum diameter of D 2 . As shown in  FIG.  13 A , the projection  1326  is received within and engages the recess  1328  when the adjunct  1302  is coupled to the cartridge  1304 . In this illustrated embodiment, the maximum diameter D 1  of the projection  1326  is larger than the maximum diameter D 2  of the recess  1328  prior to engagement. As a result, this can create an additional interference fit between the adjunct  1302  and the cartridge  1304 . This can also increase the friction between the recesses  1322   a ,  1322   b  and the projections  1324   a ,  1324   b  as the different in diameter will push the second fibers  1314  at the perimeter of the recesses  1322   a ,  1322   b  further towards and against the projections  1324   a ,  1324   b  (e.g., in a y-direction). 
     In certain embodiments, the recesses are formed in the second knitted layer of the adjunct by thermoforming the second knitted layer on a heated mold having mold features, which are the inverse shape of the desired shape for the recesses. The mold features are similar in shape to the attachment features, but can be either larger or smaller than the dimensions of the attachment features. If the mold features have smaller dimensions than the attachment features, this will ensure a snug, friction fit between the adjunct and the staple cartridge. 
     In order to form the recesses in the adjunct, the heated mold is heated to a specific temperature (e.g., at or above the glass transition temperature of the second fibers of the second knitted layer) and then the adjunct is pressed onto, into, and/or against the heated mold. In some embodiments, the mold features can be the same or different compared to one another. 
     Upon engagement with the heated mold, the adjunct forms, or molds, into the mold features of the heated mold, creating the recesses within the second knitted layer. The portion of the second knitted layer which comes into contact with the mold features of the heated mold are thermoformed into the shape of the mold features. Once the heated mold is released from the second knitted layer, the second knitted layer retains the shape of the mold features. The recesses are configured to permit the progressive release of the adjunct from the staple cartridge. One advantage of the thermoformed recesses may include having an adjunct with a more complex shape which custom fits with a corresponding staple cartridge while sustaining a simpler manufacturing process, for example. In certain embodiments, the cartridge deck and the mold features correspond to the shape of the attachment features of the staple cartridge. 
     In other embodiments, thermoforming of the adjunct can occur by heating the staple cartridge deck. The cartridge can be heated to a temperature above, at, or close to the glass transition temperature of the material, or materials, of the bottom layer (e.g., cartridge-contacting layer) of the adjunct. The adjunct can then be placed over and pushed down onto the staple cartridge and staples disposed therein. Since the adjunct is heated to a temperature above, at, or slightly below the glass transition temperature of material the adjunct is formed from, the adjunct can take a new permanent shape around the attachment features of the staple cartridge and/or around any of the staple legs extending from the top surface of the cartridge. 
     For example, the staple cartridge can include projections extending from the cartridge deck and, when the adjunct is pushed onto the heated cartridge deck and attachment features, the adjunct can be permanently deformed around the attachment features. In such instances, the adjunct tightly grips the attachment features until the adjunct is pushed off the attachment features by the staples. Similarly, the adjunct can permanently deform around and tightly grip the heated staple legs. In one embodiment, the minimum diameter of the newly-formed recesses within the adjunct can be smaller than the diameter of the staple legs. During the forming process of the recesses, the pressure is applied to the adjunct until the temperature of the staple cartridge, the staples, and/or the adjunct is well below, or at least below, the glass transition temperature of the materials comprising the adjunct. Alternatively, the pressure can be removed when the temperature of the stapling assembly is at or above the glass transition temperature of the materials comprising the adjunct. 
     In other embodiments, an adjunct can include knitted recesses that are configured to receive and engaged with one or more attachment features of a staple cartridge. For example, the as the adjunct is knitted, portions of the second fibers of the second knitted layer can be knitted in such a way to define a perimeter of the recesses within the second knitted layer. Alternatively, or in addition, additional fibers can be incorporated into the bottom layer so as to at least partially define the perimeter of the recesses 
     Fiber Interconnectivity and Adjunct Compressibility 
     An adjunct is stapled to tissue under various stapling conditions (e.g., tissue thickness, height of formed staple, intra-tissue pressure). Depending on the stapling condition, one can determine an effective amount of stress that the adjunct needs to be able to apply to the tissue to prevent tissue tearing and leakage. For example, in one embodiment, an effective amount of stress is at least about 3 gf/mm 2 . In order for the adjunct to provide an effective amount of stress to the tissue, the adjunct can be designed to effectively compensate for the various stapling conditions. As such, the adjunct can be tailored to assume different compressed heights when stapled to tissue. 
     The compressibility profile of the adjunct can therefore be controlled by at least the structural configuration of the fibers and the interconnectivity between them. As a result, the structural configuration of the fibers can be tailored to effect an adjunct with desirable mechanical properties for stapling tissue. As there is a finite range of intra-tissue pressures, tissue thicknesses, and formed staple heights, one can determine appropriate material and/or geometric structures for the adjunct that can be effective in applying a substantially continuous desired stress to the tissue (e.g., 3 gf/mm 2 ) when stapled thereto for a given amount of time (e.g., at least 3 days) over a range of stapling conditions. That is, as described in more detail below, the present adjuncts are formed of compressible materials and geometrically configured so as to allow the adjunct to compress to various heights in predetermined planes when stapled to tissue. Further, this varied response by the adjunct can also allow the adjunct to maintain its application of a continuous desired stress to the tissue when exposed to fluctuations in intra-tissue pressure that can occur when the adjunct is stapled to tissue (e.g., a spike in blood pressure). 
     As discussed above, the spacer fibers are intertwined with the first and second fibers of the top and bottom layers, respectfully, to thereby connect the top and bottom layers in a spaced apart relation. As such, the spacer fibers are interconnected with the first fibers at first interconnections and with the second fibers at second interconnections. The portions of the spacers fibers that extend between the top and bottom layers thereby form an intermediate layer of the adjunct. While these portions can have a variety of configurations, these portions can be arranged in such a manner that form standing fibers. The standing fibers can be configured to bend or compress in response to force being applied to the adjunct. As a result, the manner in which the spacer fibers interact with the first and second fibers (e.g., the first and second interconnections) can control, at least in part, the standing fibers stiffness or ability to bend under compression which, in turn, controls, at least in part, the overall compressibility of the adjunct. Thus, in some embodiments, the number, location, and tightness of the interconnections can be varied laterally, longitudinally, or thru the thickness of the adjunct to effect different stiffnesses within the adjunct. 
     In some embodiments, the first and second interconnections have a generally uniform structure (e.g., nominally identical within manufacturing tolerances), whereas in other embodiments, the first and second interconnections are different. The first and second interconnections can have a variety of configurations. For example, in some embodiments, the first interconnections and/or the second interconnection can be single-looped knots. In other embodiments, the first interconnections and/or the second interconnections can be multi-looped knots, for example, as shown in  FIGS.  14 A- 17 B . In certain embodiments, the first interconnections can be single-looped knots and the second interconnections can be multi-looped knots (see  FIG.  20   ). 
     The first and/or second interconnections can be in the form of any suitable knot type. The type of knots that are used can affect the stiffness of the intermediate layer, and consequently, the compression behavior of the adjunct. For example, if loose knots are used, the intermediate layer can be less stiff or can have a lower modulus of elasticity. Alternatively, if tight knots are used, the intermediate layer can be stiffer or have a higher modulus of elasticity. The intermediate layer can utilize any suitable type, or types, of knots. 
       FIGS.  14 A- 14 B  is another exemplary embodiment of a knitted adjunct  1400  that includes first fibers  1402 , second fibers  1404 , and spacer fibers  1406 . For sake of simplicity, only one first fiber  1402 , second fiber  1404 , and spacer fiber  1406  is being illustrated. A person skilled in the art will appreciate that the following discussion is also applicable to the remaining first, second, and spacer fibers of the adjunct. 
     The spacer fibers  1406  and the first fibers  1402  are interconnected at first interconnections  1408  to form a top layer  1410 . The spacer fibers  1406  and the second fibers  1404  are interconnected at second interconnections  1412  to form a bottom layer  1414 . The first and second interconnections  1408 ,  1412  can have a variety of configurations. For example, as shown, the first interconnections  1408  are in the form of first knots having the spacer fibers  1406  multi-looped about the first fibers  1402  and the second interconnections  1412  are each in the form of second knots having the spacer fibers  1406  multi-looped about the second fibers  1404 . While the first and second knots  1408 ,  1412  are illustrated as being structurally similar, in other embodiments, the first and second knots can be different. Further, as described in more detail below, the first knots  1408  and the second knots  1412  are schematically illustrated as having a loose knot configuration. 
     Further, the portions of the spacer fibers  1406  that extend between the top and bottom layers  1410 ,  1414  form an intermediate layer  1418  that is positioned between the top and bottom layers  1410 ,  1414 . While these portions can have a variety of configurations, in this illustrated embodiment, they are arranged in such a manner that form standing fibers  1416 . The standing fibers  1416  can be have a variety of orientations within the intermediate layer  1418 , such as a generally columnar configuration, as shown, meaning they are generally oriented in adjacent columns. The standing fibers  1416  can be configured to bend or compress in response to force being applied to the adjunct  1400 , as schematically illustrated in  FIG.  14 B . 
     As depicted in  FIG.  14 B , when a given force F is applied to the adjunct  1400  (e.g., in an x-direction), the spacer fibers  1406  slide along the first and second fibers  1402 ,  1404  (e.g., in a ±y-direction). This sliding action is due to the loose knot configuration of the first and second knots  1408 ,  1412 . Consequently, the standing fibers  1416  slide and causes the top layer  1410  to move towards the bottom layer  1414 . As a result, the adjunct  1400  compresses from an uncompressed state ( FIG.  14 A ) with an uncompressed height H 1  to a first compressed state ( FIG.  14 B ) with a first compressed height H 2 . Thus, under a given force, the sliding of the spacer fibers  1406 , and consequently, the standing fibers  1416 , primarily effects the compression of the adjunct  1400  from the uncompressed height H to the first compressed height H 2 . 
     In some embodiments, tighter knots can be used to interconnect the spacer fibers with the first fibers and the seconds second fibers, for example, as shown in  FIGS.  15 A- 15 B , to thereby increase the stiffness of the standing fibers, and thus the stiffness of the adjunct. Adjunct  1500  is similar to adjunct  1400  in  FIGS.  14 A- 14 B  except that the first and second knots  1508 ,  1512  have a tighter knot configuration, and therefore common features are not described in detail herein. 
     As depicted in  FIG.  15 B , when a given force F is applied to the adjunct  1500  (e.g., in an x-direction), the tighter configuration of the knots  1508 ,  1512  inhibit the spacer fibers  1506  from sliding along the first and second fibers  1502 ,  1504 , and thus prevent the standing fibers  1516  from respectively sliding. This imparts more rigidity to the standing fibers  1516 , thereby increasing their stiffness. As a result, the standing fibers  1516  are stiffer compared to the standing fibers  1416  of  FIGS.  14 A- 14 B , and therefore this leads to a stiffer adjunct  1500  when compared to the adjunct  1400  of  FIGS.  14 A- 14 B . For example, when the same amount of force is applied to the adjunct  1500 , the adjunct  1500  compresses from an uncompressed state ( FIG.  14 A ) with an uncompressed height H 3  that is similar to uncompressed H 1  of adjunct  1400  to a second compressed state ( FIG.  14 B ) with a second compressed H 4  that is larger than the first compressed height H 2  of adjunct  1400 . This illustrates the impact that knot tightness can have on the compression of an adjunct. 
     Similarly, knot tightness can impart can impart partial rigidity to thinner spacer fibers, and thus, increase the overall stiffness of an adjunct, like adjunct  1600  in  FIGS.  16 A- 16 C . Adjunct  1600  is similar to adjunct  1500  in  FIGS.  15 A- 15 B  except that the spacer fibers  1606  are thinner compared to spacer fibers  1506 . 
     In some embodiments, the intermediate layer of an adjunct can include reinforcing fibers that are interconnected with the standing fibers, which can further increase the stiffness of the adjunct, for example, as shown in  FIGS.  17 A- 17 B . Adjunct  1700  is similar to adjunct  1500  in  FIGS.  15 A- 15 B  except that the standing fibers  1716  are multi-looped about reinforcing fibers  1720  at third interconnections  1722 , in which the reinforcing fibers  1720  each extend mid-way through the intermediate layer  1718  (e.g., extending in the y-direction). As a result, for a given amount of force F, as shown in  FIG.  17 B , the adjunct  1700  will compress from an uncompressed state ( FIG.  17 A ) with an uncompressed height H 5  that is similar to uncompressed H 3  of adjunct  1500  to a second compressed state ( FIG.  17 B ) with a third compressed height H 6 , which is larger than the second compressed height H 4  of adjunct  1500 . 
       FIGS.  18 A- 18 B  illustrate another exemplary embodiment of a knitted adjunct  1800 . The adjunct  1800  includes a layer  1802  formed of at least first fibers  1808 , and a core layer formed of spacer fibers  1804  intertwined with and extending from the layer  1802 . The layer  1802  can be a top layer (e.g., a tissue-contacting layer) or a bottom layer (e.g., a cartridge-contacting layer) of the adjunct  1800 , with portions of the spacer fibers  1804  forming the core layer arranged between the top and bottom layers. In this illustrate embodiment, the portions of the spacer fibers  1804  that form the core layer extend between the top and bottom layers in a generally columnar configuration, meaning they are generally oriented in adjacent columns. For sake of simplicity, only a portion of the first fibers  1808  and of the spacer fibers  1804  is being illustrated. A person skilled in the art will appreciate that the following discussion is also applicable to the remaining first fibers and spacer fibers of the adjunct. 
     As shown in  FIGS.  18 A- 18 B , the spacer fibers  1804  extend along a central axis CA, outward from the layer  1802 . The layer  1802  includes reinforcing fibers  1806 , which are knotted to the spacer fibers  1804  and the first fibers  1808 . The knotting of the reinforcing fibers  1806  can limit the lateral movement LM of the spacer fibers  1804  from the central axis CA of each spacer fiber  1804 . This interaction between the spacer fibers  1804  and the reinforcing fibers  1806  affects the stiffness of the adjunct  1800 . Since the spacer fibers  1804  have limited lateral movement LM, the spacer fibers  1804  have limited deformation abilities when the adjunct  1800  is compressed. 
       FIGS.  19 A- 19 B  illustrate another exemplary embodiment of a knitted adjunct  1900 . The adjunct  1900  can be disposed on a top or deck surface of a staple cartridge. The adjunct  1900  includes a layer  1902  formed of at least first fibers  1908 , and a core layer formed of spacer fibers  1904  intertwined with and extending from the layer  1902 . The layer  1902  can be a top layer (e.g., a tissue-contacting layer) or a bottom layer (e.g., a cartridge-contacting layer) of the adjunct  1900 , with the spacer fibers  1904  forming the core layer arranged between the top and bottom layers. In this illustrated embodiment, the portions of the spacer fibers  1904  that form the core layer extend between the top and bottom layers in a generally columnar configuration, meaning they are generally oriented in adjacent columns. For sake of simplicity, only a portion of the first fibers  1908  and of the spacer fibers  1904  is being illustrated. A person skilled in the art will appreciate that the following discussion is also applicable to the remaining first fibers and spacer fibers of the adjunct. 
     As shown in  FIGS.  19 A- 19 B , the spacer fibers  1904  extend along a central axis CA, outward from the layer  1902 . The layer  1902  does not include any reinforcing fibers in contact with the spacer fibers  1904 . Due to the lack of reinforcing fibers, the spacer fibers are less limited in their lateral movement LM from the central axis CA of each spacer fiber  1904  when compared to the adjunct  1800  of  FIG.  18 A . This interaction between the spacer fibers  1904  and the first fibers  1908 , with any reinforcing fibers, affects the stiffness of the adjunct  1900 . Since the spacer fibers  1904  have extended lateral movement LM, the spacer fibers  1904  have greater deformation abilities when compared to the adjunct  1800  of  FIG.  18 A  when the adjunct  1900  is compressed. 
       FIG.  20    illustrates another exemplary embodiment of a knitted adjunct  2000 . The adjunct  2000  includes a top layer  2002  (e.g., a tissue-contacting layer) formed of at least first fibers  2008 , a bottom layer  2004  (e.g., a cartridge-contacting layer) formed of at least second and third fibers  2012 ,  2014  and spacer fibers  2016  intertwined with and extending between the top and bottom layers  2002 ,  2004  to thereby connect the top and bottom layers  2002 ,  2004 . The portions of the spacer fibers  2016  that extend between the top and bottom layers  2002 ,  2004  form a core layer  2006 . For sake of simplicity, only one first fiber  2008 , second fiber  2012 , third fiber  2014 , and spacer fiber  2016  is being illustrated. A person skilled in the art will appreciate that the following discussion is also applicable to the remaining first, second, third, and spacer fibers of the adjunct. 
     The top and bottom layers  2002 ,  2004  can have a variety of configurations. For example, as shown in  FIG.  20   , the bottom layer  2004  has a fiber density that is greater than the fiber density of the top layer  2002 . In other embodiments, the top layer  2002  can have a greater fiber density than the bottom layer  2004 . In some embodiments, the first fibers  2008  of the top layer  2002  can be knitted or woven into a first predetermined pattern and/or the second and third fibers  2012 ,  2014  of the bottom layer  2004  can be knitted or woven into a second predetermined pattern. In certain embodiments, the first and second predetermined patterns can be generally identical (e.g., nominally identical within manufacturing tolerances), whereas in other embodiments, the first and second predetermined patterns can be different. A person skilled in the art will appreciate that the first fibers  2008  and the second and third fibers  2012 ,  2014  can be randomly or repeatedly knitted or woven within the top and bottom layers  2002 ,  2004 , respectively. As such, and for sake of simplicity, the top and bottom layers  2002 ,  2004  are generally illustrated, and thus the specific structural configurations of the top and bottom layers  2002 ,  2004  are not limited to what is depicted in the figures. 
     The first fibers  2008 , the second fibers  2012 , the third fibers,  2014  and the spacer fibers  2016  can have a variety of configurations. For example, in some embodiments, the first fibers  2008 , the second fibers  2012 , the third fibers  2014 , and the spacer fibers  2016  can be generally identical (e.g., nominally identical within manufacturing tolerances) in material and/or structural configuration. In other embodiments, the first, second, and third fibers  2008 ,  2012 ,  2014  can be generally identical (e.g., nominally identical within manufacturing tolerances) in material and/or structural configuration relative to each other and the spacer fibers  2016  can be different relative thereto. For example, in certain embodiments, the first, second, third fibers  2008 ,  2012 ,  2014 , can be multifilament fibers, and the spacer fibers  2016  can be monofilament fibers. As such, aside from the general overall shape, the specific structural configuration of each of the first fibers  2008 , the second fibers  2012 , the third fibers  2014 , and the spacer fibers  2016  is not shown. 
     In certain embodiments, the first fibers  2008  can be formed of low friction fibers (e.g., monofilament fibers) that are knitted or woven to effect a substantiality smooth pattern to help retain the adjunct  2000  on a top or deck surface on a cartridge when tissue slides across the adjunct  2000 , for example, when the adjunct  2000  is being placed at the stapling site. As such, employing low friction fibers within a top layer (e.g., tissue-contacting layer) of an adjunct can minimize the friction that would otherwise be created between the tissue and adjunct as the tissue slides across the adjunct prior to staple deployment. 
     As further shown, the bottom layer  2004  includes fourth fibers  2019  that can be configured to increase the friction between the adjunct  2000  and a top or deck surface of a cartridge. This can help retain the adjunct  2000  to the cartridge prior to staple deployment. The fourth fibers  2019  can have a variety of configurations. For example, in some embodiments, the fourth fibers can be multifilament fibers. As such, aside from the general overall shape, the specific structural configuration of the fourth fibers  2019  is not shown. Further, for sake of simplicity, only one fourth fiber  2019  is being illustrated. 
     The spacer fibers  2016  are interconnected within the first fibers  2008  at first and second interconnections  2018 ,  2022  within the top layer  2002 , and the spacer fibers  2016  are interconnected with at least the second and third fibers  2012 ,  2014  at third and fourth interconnections  2020 ,  2024  within the bottom layer  2004 . As such, this interaction between the top and bottom layers  2002 ,  2004  with that of the core layer  2006  secures the top layer  2002  to the bottom layer  2004 . Further, the portions of spacer fibers that form the core layer  2006  are arranged in such a manner to form standing fibers  2026 . The standing fibers  2026  can be have a variety of orientations within the core layer  2006 , such as a generally columnar configuration, as shown, meaning they are generally oriented in adjacent columns. The standing fibers  2026  can be configured to bend or compress in response to force being applied to the adjunct  2000 . 
     As shown in  FIG.  20   , the interconnections  2018 ,  2020 , and  2022 ,  2024  can be identical between the top layer  2002  and the bottom layer  2004 . The interconnections  2018 ,  2020  are represented as tight knots, with the spacer fibers  2016  wrapping around the first fibers  2008  of the top layer  2002  multiple times, while also wrapping around the second and third fibers  2012 ,  2014  of the bottom layer  2004 . In some embodiments, even though the interconnections  2018 ,  2020  are depicted as tight knots formed by wrapping the spacer fibers  2016  around the first, second, and third fibers  2008 ,  2012 ,  2014 , other types of tight knots for the interconnections  2018 ,  2020  can be used, such as any knot that prevents sliding of the spacer fibers  2016  to slide along the first, second, and third fibers  2008 ,  2012 ,  2014 . 
     Additionally, the interconnections  2022 ,  2024  are represented as loose knots, with the spacer fibers  2016  passing through the first fibers  2008  of the top layer  2002  for a single pass, while also passing through the second and third fibers  2012 ,  2014  of the bottom layer  2004  for a single pass. In some embodiments, even though the interconnections  2022 ,  2024  are depicted as loose knots formed by wrapping the spacer fibers  2016  around the first, second, and third fibers  2008 ,  2012 ,  2014 , other types of loose knots for the interconnections  2022 ,  2024  can be used, such as any knot that prevents sliding of the spacer fibers  2016  to slide along the first, second, and third fibers  2008 ,  2012 ,  2014 . 
     Due to the presence of two different types of interconnections, the adjunct  2000  can have a first compression zone  2028  and a second compression zone  2030 . Each compression zone can have a different stiffness when compressed, even though both compression zones are manufactured from the same fibers. This is because when the adjunct  2000  is compressed, the interconnections  2018 ,  2020  inhibit the spacer fibers  2016  from sliding along the first, second, and third fibers  2008 ,  2012 ,  2014 , whereas, in contrast, the interconnections  2022 ,  2024  allow the spacer fibers  2016  to slide along the first, second, and third fibers  2008 ,  2012 ,  2014 . As such, each different compression zone  2028 ,  2030  has a respective stiffness such that the adjunct  2000  can have a variable compression strength, for example, along its width (e.g., in a y-direction). 
     In certain embodiments, the spacer fibers can interact with at least a portion of the remaining fibers of the bottom layer (e.g., cartridge-contacting layer) of an adjunct in such a way that allows the spacer fibers to extend beyond the remaining fibers (e.g., in the form of loops) when the adjunct is compressed. Alternatively, or in addition, the spacer fibers can interact with at least a portion of the remaining fibers of the top layer (e.g., tissue-contacting layer) of an adjunct in such a way that allows the spacer fibers to extend beyond the remaining fibers (e.g., in the form of loops) when the adjunct is compressed. 
     In addition to fiber connectivity, the overall compression behavior of an adjunct can at least partially depend on the type of spacer fibers incorporated therein. As such, a desired compression behavior of the adjunct can be effected by at least incorporating spacer fibers having a particular structural configuration (e.g., monofilament or multifilament) and/or dimensions (e.g., diameter), and/or a particular compositional make-up (e.g., a first polymeric material having a low modulus of elasticity, a second polymeric material having a high modulus of elasticity, or a blend of two or more polymeric materials). Further, the compression behavior can be a function of the orientation of the portions of the spacer fibers within a core or intermediate layer of an adjunct (e.g., the direction the standing fibers extend relative to the longitudinal axis of the adjunct). 
     In some embodiments, different spacer fibers can be incorporated into different portions within the adjunct to effect different compression zones within the adjunct. For example, a first type of spacer fiber (e.g., first spacer fibers) can be selected to create a first compression zone and a second type of spacer fiber (e.g., second spacer fibers) that differs from the first type of spacer fiber can be selected to create a second compression zone. The first type of fiber can differ from the second type of fiber in structure (e.g., structure type, e.g., monofilament or multifilament, and/or in dimension, e.g., height and/or diameter) and/or composition. As such, the first compression zone has a first compression strength and the second compression zone has a second compression strength that is different than the second compression strength. As a result, the adjunct has a varied compression strength. 
     For example, the first compression zone can have a greater compression strength than the second compression zone, and therefore the first compression zone can be more stiff. In use, the first compression zone can at least partially overlap with a longitudinal slot formed in the cartridge which is configured to receive a cutting member and the second compression zone can at least partially overlap with staple cavities defined in the cartridge. Such an arrangement can facilitate the transection of the adjunct while providing desirable tissue thickness compensation properties within the staples that capture the adjunct against the tissue. In certain instances, the second compression can also partially overlap with one or more portions of the longitudinal slot. In one embodiment, the second compression zone can be the proximate-most zone to the beginning and/or end of the longitudinal slot. 
       FIGS.  21 A- 21 B  is an exemplary embodiment of a knitted adjunct  2100  having two different types of spacer fibers. The adjunct  2100  includes first fibers  2102 , second fibers  2104 , first spacer fibers  2106 , and second, different spacer fibers  2108  that are intertwined to form a top layer  2110  (e.g., a tissue-contacting layer), a bottom layer  2112  (e.g., a cartridge-contacting layer) and an intermediate layer  2114  that is positioned between the top and bottom layers  2110 ,  2112 . As shown in  FIG.  21 A , the first spacer fibers  2106  are concentrated within a center portion of the intermediate layer  2114  (represented as a dotted box  2114   a ) and define a first compression zone of the adjunct  2100 . The second spacer fibers  2108  are concentrated in the remaining portion of the intermediate layer  2114  and define a second compression zone within the adjunct  2100 . 
     The first fibers  2102 , the second fibers  2104 , the first spacer fibers  2106 , and the second spacer fibers  2108  can have a variety of configurations. For example, in some embodiments, the first fibers  2102  and the second fibers  2104  can be generally identical (e.g., nominally identical within manufacturing tolerances) in compositional makeup (e.g., formed of the same material(s)), dimension(s) (e.g., height and/or diameter), and/or in structural configuration (e.g., monofilament or multifilament). In other embodiments, the first and second fibers  2102 ,  2104  can be different. Further, the first fibers and/or second fibers can be the same as the first spacer fibers or the second spacer fibers. In some embodiments, the first fibers  2102 , the second fibers  2104 , the first spacer fibers  2106 , and/or the second spacer fibers  2108  can be monofilament fibers. In other embodiments, the first fibers  2102 , the second fibers  2104 , the first spacer fibers  2106 , and/or the second spacer fibers  2108  can be monofilament fibers. In certain embodiments, the first fibers  2102 , the second fibers  2104 , and the first spacer fibers  2106  can be monofilament fibers and the second spacer fibers  2108  are multifilament fibers. As such, aside from the general overall shape, the specific structural configuration of the first fibers  2102 , the second fibers  2104 , the first spacer fibers  2106 , and the second spacer fibers  2108  are not shown. 
     In some embodiments, the first fibers  2102  of the top layer  2110  and/or second fibers  2104  of the bottom layer  2112  can be knitted in a respective predetermined pattern. In certain embodiments, the predetermined pattern of the first fibers  2102  within the top layer  2110  and the predetermined pattern of the second fibers  2104  of the bottom layer  2112  can be generally identical (e.g., nominally identical within manufacturing tolerances), whereas in other embodiments, the predetermined patterns can be different. Further, in some embodiments, the fiber density of the top layer  2110  can be different than the fiber density of the bottom layer  2112 . While the first fibers  2102  of the top layer  2110  and the second fibers  2104  of the bottom layer  2112  can each be knitted in various patterns, in certain embodiments, the first fibers  2102  can be knitted into a first Raschel knit pattern and the second fibers  2104  can be knitted into a second Raschel knit pattern that is the same or different than the first Rachel knit pattern. A person skilled in the art will appreciate that the first fibers  2102  and the second fibers  2104  can be randomly or repeatedly knitted or woven within the top and bottom layers  2110 ,  2112 , respectively. As such, and for sake of simplicity, the top and bottom layers  2110 ,  2112  are generally illustrated, and thus the specific structural configurations of the top and bottom layers  2110 ,  2112  are not limited to what is depicted in the figures. 
     As shown in  FIGS.  21 A- 21 B , the portions of the first spacer fibers  2106  and the portions of the second spacer fibers  2108  that extend between the top and bottom layers  2110 ,  2112  form the intermediate layer  2114 . While these portions can have a variety of configurations, in this illustrated embodiment, they are arranged in a generally columnar configuration, meaning they are generally oriented in adjacent columns. The compression behavior of the adjunct  2100  can therefore be predominately driven by the buckling properties of the first and second spacer fibers  2106 ,  2108 . 
     As further shown, the first compression zone  2114   a  is completely bordered by the second compression zone, and therefore the intended cut-line C L  of the adjunct  2100  is defined across the first and second compression zones and along the longitudinal axis L A  of the adjunct  2100 . In this illustrated embodiment, the majority of the intended cut-line C L  is defined by the first compression zone  2114   a , and therefore can be configured to be stiffer, and thus exhibit a higher resistance to compression, compared to the second compression zone. For example, the first spacer fibers  2106  can be monofilament fibers and the second spacer fibers  2108  can be multifilament fibers. Thus, the resulting adjunct  2100  can have a variable compression strength in a lateral direction (e.g., the y-direction) relative to the cut-line C L  of the adjunct  2100 . Further, the beginning and end of the cut-line CL is defined by the second compression zone, which can therefore make cutting of the adjunct  2100  easier. 
     In some embodiments, the bottom layer  2112  can also be formed of one or more additional fibers  2116 , as shown in more detail  FIG.  21 B . While the one or more additional fibers  2116  can have a variety of configurations, in this illustrated embodiment, the one or more additional fibers are interconnected within the bottom layer  2112  in such a way to form loops (e.g., traction loops) that provide traction against a top or deck surface of a cartridge to thereby help retain the adjunct to the cartridge prior to staple deployment. Alternatively, or in addition, the one or more additional fibers  2116  can be incorporated into the adjunct for purposes of thermoforming or bonding the adjunct to a cartridge. The one or more additional fibers  2116  can be multifilament or monofilament fibers. In one embodiment, the one or more additional fibers  2116  are multifilament fibers. In certain embodiments, the one or more additional fibers  2116  can include at least two first and second additional fibers, in which the first additional fiber differs from the second additional fiber in compositional makeup (e.g., formed of the same material(s)), dimension(s) (e.g., height and/or diameter) and/or in structural configuration (e.g., monofilament or multifilament). 
     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. 
     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 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 a device. Other spatial terms such as “front” and “rear” 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 devices are used in many orientations and positions, and these spatial terms are not intended to be limiting and absolute. 
     Values or ranges may be expressed herein as “about” and/or from/of “about” one particular value to another particular value. When such values or ranges are expressed, other embodiments disclosed include the specific value recited and/or from/of the one particular value to another particular value. Similarly, when values are expressed as approximations, by the use of antecedent “about,” it will be understood that here are a number of values disclosed therein, and that the particular value forms another embodiment. It will be further understood that there are a number of values disclosed therein, and that each value is also herein disclosed as “about” that particular value in addition to the value itself. In embodiments, “about” can be used to mean, for example, within 10% of the recited value, within 5% of the recited value or within 2% of the recited value. 
     For purposes of describing and defining the present teachings, it is noted that unless indicated otherwise, the term “substantially” is utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The term “substantially” is also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. 
     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. Any patent, publication, or information, in whole or in part, that is said to be incorporated by reference herein is only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this document. As such the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference.