Patent Publication Number: US-9884456-B2

Title: Implantable layers and methods for altering one or more properties of implantable layers for use with fastening instruments

Description:
BACKGROUND 
     The present invention relates to surgical instruments and, in various arrangements, to surgical stapling and cutting instruments and staple cartridges therefor that are designed to staple and cut tissue. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a left front perspective view of a surgical stapling and severing instrument with a handle portion; 
         FIG. 2  is a perspective view of a two-piece knife and firing bar (“E-beam”) of the surgical stapling and severing instrument of  FIG. 1 ; 
         FIG. 3  is a perspective view of a wedge sled of a staple cartridge of a staple applying assembly; 
         FIG. 4  is a longitudinal cross-sectional view of an anvil in a closed position and a staple cartridge comprising a rigid support portion and a compressible tissue thickness compensator illustrated with staples being moved from an unfired position to a fired position during a first sequence; 
         FIG. 5  is another cross-sectional view of the anvil and the staple cartridge of  FIG. 4  illustrating the anvil in an open position after the firing sequence has been completed; 
         FIG. 6  is an exploded perspective view of a tissue thickness compensator and a staple cartridge assembly; 
         FIG. 7  is a partial cross-sectional view of the staple cartridge assembly of  FIG. 6 , illustrating unfired staples positioned in staple cavities of a staple cartridge body and partially embedded in a tissue thickness compensator; 
         FIG. 8  is a partial cross-sectional view of the staple cartridge assembly of  FIG. 6 , illustrating fired staples ejected from the staple cavities of the staple cartridge body and formed against an anvil, and further illustrating the tissue thickness compensator and tissue captured within the staple entrapment area of the formed staples; 
         FIG. 9  is a partial perspective view of an end effector of a surgical fastening instrument illustrated with some portions removed and other portions illustrated in cross-section; moreover, a cutting member of the end effector is illustrated in a partially advanced position; 
         FIG. 10  is a partial cross-sectional end view of the end effector of  FIG. 9  illustrated with patient tissue captured between an anvil and a tissue thickness compensator of the end effector; moreover, staples removably stored within a cartridge body of the end effector are illustrated in an unfired position and the cutting member of the end effector is illustrated in an unadvanced position which is proximal to the tissue thickness compensator; 
         FIG. 11  is a partial cross-sectional end view of the end effector of  FIG. 9  illustrated with the staples in a fired position and the cutting member in a partially advanced position in which the patient tissue has been at least partially transected; 
         FIG. 12  is a partial cross-sectional end view of the end effector of  FIG. 9  illustrated with the staples in a fired position and the cutting member in an advanced position in which at least a portion of the tissue thickness compensator has been transected by the cutting member; 
         FIG. 13  is a perspective view of a fastener cartridge including a tissue thickness compensator; 
         FIG. 14  is a cross-sectional view of the tissue thickness compensator of  FIG. 13  illustrating a cutting member positioned relative to a proximal end of the tissue thickness compensator. 
         FIG. 15  is an exploded view of a tissue thickness compensator assembly; 
         FIG. 16  is a perspective view of layer of a tissue thickness compensator assembly; 
         FIG. 17  is a cross-sectional view of the tissue thickness compensator assembly of  FIG. 15 ; 
         FIG. 18  is a cross-sectional perspective view of an assembled tissue thickness compensator assembly and a mold for assembling the same; 
         FIG. 19  is a perspective view of the assembled tissue thickness compensator assembly of  FIG. 18 ; 
         FIG. 20  is a perspective view of a tissue thickness compensator assembly and a mold for assembling the same; 
         FIG. 21  is a perspective view of a tissue thickness compensator assembly and a mold for assembling the same; 
         FIG. 22  is a cross-sectional perspective view of the tissue thickness compensator assembly of  FIG. 21  and the mold of  FIG. 21  for assembling the same; 
         FIG. 23  is a perspective view of an end effector comprising a tissue thickness compensator; 
         FIG. 24  is a perspective view of the end effector and the tissue thickness compensator of  FIG. 23  and a modifying member modifying the tissue thickness compensator; 
         FIG. 25  is a perspective view of the end effector of  FIG. 23  comprising the modified tissue thickness compensator of  FIG. 24 ; 
         FIG. 26  is a cross-sectional perspective view of a tissue thickness compensator; 
         FIG. 27  is a cross-sectional perspective view of a mold for modifying the tissue thickness compensator of  FIG. 26 ; 
         FIG. 28  is a cross-sectional perspective view of the tissue thickness compensator of  FIG. 26  after modification by the mold of  FIG. 27 ; 
         FIG. 29  is a cross-sectional perspective view of a tissue thickness compensator; 
         FIG. 30  is a cross-sectional perspective view of a mold for modifying the tissue thickness compensator of  FIG. 29 ; 
         FIG. 31  is a cross-sectional perspective view of the tissue thickness compensator of  FIG. 29  after modification by the mold of  FIG. 30 ; 
         FIG. 32  is a cross-sectional perspective view of a tissue thickness compensator; 
         FIG. 33  is a cross-sectional perspective view of a mold for modifying the tissue thickness compensator of  FIG. 32 ; 
         FIG. 34  is a cross-sectional perspective view of the tissue thickness compensator of  FIG. 32  after modification by the mold of  FIG. 33 ; 
         FIG. 35  is a cross-sectional perspective view of a tissue thickness compensator including a first height; 
         FIG. 36  is a cross-sectional perspective view of the tissue thickness compensator of  FIG. 35  after modification to change the first height to a second height; 
         FIG. 37  is a cross-sectional view of a mold for modifying the tissue thickness compensator of  FIG. 35 ; 
         FIG. 38  is a cross-sectional perspective view of a tissue thickness compensator; 
         FIG. 39  is a cross-sectional perspective view the tissue thickness compensator of  FIG. 38  after modification; 
         FIG. 40  is a graph illustrating the effect of compression forces on a spring rate of a tissue thickness compensator; 
         FIG. 41  is a cross-sectional perspective view of a tissue thickness compensator; 
         FIG. 42  is a cross-sectional perspective view of a space creator for modifying the tissue thickness compensator of  FIG. 41 ; 
         FIG. 43  is a cross-sectional perspective view of the tissue thickness compensator of  FIG. 41  after modification by the space creator of  FIG. 42 ; 
         FIG. 44  is a partial cross-sectional elevational view of a fastener cartridge for use with a surgical instrument including a firing member in accordance with at least one embodiment illustrated with portions removed; 
         FIG. 45  is a partial cross-sectional elevational view depicting a tissue thickness compensator of the fastener cartridge of  FIG. 44  being removed from the fastener cartridge and the firing member of  FIG. 44  illustrated in a locked-out condition; 
         FIG. 46  is a partial perspective view of the tissue thickness compensator of  FIG. 45 ; 
         FIG. 47  is a partial perspective view a tissue thickness compensator in accordance with at least one embodiment; 
         FIG. 48  is a partial cross-sectional elevational view of an end effector of a surgical instrument comprising a fastener cartridge including the tissue thickness compensator of  FIG. 47 , a sled, and a firing member supported by the sled illustrated with portions removed; 
         FIG. 49  is a partial cross-sectional elevational view of the end effector of  FIG. 48  illustrating the firing member in a partially-fired position; 
         FIG. 50  is a partial cross-sectional elevational view of the end effector of  FIG. 48  illustrating the tissue thickness compensator removed from the fastener cartridge and the firing member in a locked-out condition; 
         FIG. 51  is a partial perspective view of a fastener cartridge in accordance with at least one embodiment illustrated with portions removed; 
         FIG. 52  is a perspective view of a sled of the fastener cartridge of  FIG. 51 ; 
         FIG. 53  is a partial perspective view of the fastener cartridge of  FIG. 51 ; 
         FIG. 54  is an elevational view of a sled in accordance with at least one embodiment; 
         FIG. 55  is a perspective view of a sled in accordance with at least one embodiment illustrated in an unlocked configuration; 
         FIG. 56  is a perspective view of the sled of  FIG. 55  illustrated in a locked-out configuration; 
         FIG. 57  is a partial cross-sectional elevational view of the sled of  FIG. 55  positioned within a fastener cartridge illustrating the sled in its unlocked configuration, a firing member supported by the sled, and a tissue thickness compensator of the fastener cartridge engaged with the sled; 
         FIG. 58  is a partial cross-sectional elevational view of the tissue thickness compensator of  FIG. 57  being removed from the fastener cartridge of  FIG. 57  which has placed the sled of  FIG. 55  in its locked-out configuration and the firing member of  FIG. 57  in a locked-out condition; 
         FIG. 59  is a partial cross-sectional elevational view of a sled positioned at the proximal end of a fastener cartridge in accordance with at least one embodiment illustrated with portions removed; 
         FIG. 60  is a partial cross-sectional elevational view of the sled of  FIG. 59  illustrated at the distal end of the fastener cartridge; 
         FIG. 61  is a perspective view of a sled in accordance with at least one embodiment; 
         FIG. 62  is a diagram depicting a staple comprising a plurality of barbs in accordance with at least one embodiment, wherein the staple is illustrated in an unformed configuration and a deformed configuration; 
         FIG. 63  is an elevational view of a staple comprising a plurality of barbs in accordance with at least one embodiment, wherein the staple is positioned within a staple cavity in an unfired position; 
         FIG. 64  is an elevational view of a staple including a plurality of barbs in accordance with at least one embodiment; 
         FIG. 65  is an elevational view of a staple including a plurality of barbs in accordance with at least one embodiment; 
         FIG. 66  is an elevational view of a staple including a plurality of barbs in accordance with at least one embodiment; 
         FIG. 67  is an elevational view of a staple including a plurality of barbs in accordance with at least one embodiment; 
         FIG. 68  is an elevational view of the staple including a plurality of barbs in accordance with at least one embodiment, wherein the staple is positioned within a staple cavity in an unfired position; 
         FIG. 69  is a plan view of the staple and the staple cavity of  FIG. 68 ; 
         FIG. 70  is a partial perspective view of a barbed staple leg in accordance with at least one embodiment; 
         FIG. 71  is a partial perspective view of a barbed staple leg of the staple of  FIG. 68 ; 
         FIG. 71A  is a cross-sectional plan view of the barbed staple leg of  FIG. 71 ; 
         FIG. 72  is a partial perspective view of a barbed staple leg in accordance with at least one embodiment; and 
         FIG. 73  is a partial perspective view of a barbed staple leg in accordance with at least one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The Applicant of the present application also owns the U.S. Patent Applications identified below which are each herein incorporated by reference in their respective entirety:
     U.S. patent application Ser. No. 12/894,311, entitled SURGICAL INSTRUMENTS WITH RECONFIGURABLE SHAFT SEGMENTS; now U.S. Pat. No. 8,763,877;   U.S. patent application Ser. No. 12/894,340, entitled SURGICAL STAPLE CARTRIDGES SUPPORTING NON-LINEARLY ARRANGED STAPLES AND SURGICAL STAPLING INSTRUMENTS WITH COMMON STAPLE-FORMING POCKETS; now U.S. Pat. No. 8,899,463;   U.S. patent application Ser. No. 12/894,327, entitled JAW CLOSURE ARRANGEMENTS FOR SURGICAL INSTRUMENTS; now U.S. Pat. No. 8,978,956;   U.S. patent application Ser. No. 12/894,351, entitled SURGICAL CUTTING AND FASTENING INSTRUMENTS WITH SEPARATE AND DISTINCT FASTENER DEPLOYMENT AND TISSUE CUTTING SYSTEMS; now U.S. Pat. No. 9,113,864;   U.S. patent application Ser. No. 12/894,338, entitled IMPLANTABLE FASTENER CARTRIDGE HAVING A NON-UNIFORM ARRANGEMENT; now U.S. Pat. No. 8,864,007;   U.S. patent application Ser. No. 12/894,369, entitled IMPLANTABLE FASTENER CARTRIDGE COMPRISING A SUPPORT RETAINER; now U.S. Patent Publication No. 2012/0080344;   U.S. patent application Ser. No. 12/894,312, entitled IMPLANTABLE FASTENER CARTRIDGE COMPRISING MULTIPLE LAYERS; now U.S. Pat. No. 8,925,782;   U.S. patent application Ser. No. 12/894,377, entitled SELECTIVELY ORIENTABLE IMPLANTABLE FASTENER CARTRIDGE; now U.S. Pat. No. 8,393,514;   U.S. patent application Ser. No. 12/894,339, entitled SURGICAL STAPLING INSTRUMENT WITH COMPACT ARTICULATION CONTROL ARRANGEMENT; now U.S. Pat. No. 8,840,003;   U.S. patent application Ser. No. 12/894,360, entitled SURGICAL STAPLING INSTRUMENT WITH A VARIABLE STAPLE FORMING SYSTEM; now U.S. Pat. No. 9,113,862;   U.S. patent application Ser. No. 12/894,322, entitled SURGICAL STAPLING INSTRUMENT WITH INTERCHANGEABLE STAPLE CARTRIDGE ARRANGEMENTS; now U.S. Pat. No. 8,740,034;   U.S. patent application Ser. No. 12/894,350, entitled SURGICAL STAPLE CARTRIDGES WITH DETACHABLE SUPPORT STRUCTURES; now U.S. Patent Publication No. 2012/0080478;   U.S. patent application Ser. No. 12/894,383, entitled IMPLANTABLE FASTENER CARTRIDGE COMPRISING BIOABSORBABLE LAYERS; now U.S. Pat. No. 8,752,699;   U.S. patent application Ser. No. 12/894,389, entitled COMPRESSIBLE FASTENER CARTRIDGE; now U.S. Pat. No. 8,740,037;   U.S. patent application Ser. No. 12/894,345, entitled FASTENERS SUPPORTED BY A FASTENER CARTRIDGE SUPPORT; now U.S. Pat. No. 8,783,542;   U.S. patent application Ser. No. 12/894,306, entitled COLLAPSIBLE FASTENER CARTRIDGE; now U.S. Pat. No. 9,044,227;   U.S. patent application Ser. No. 12/894,318, entitled FASTENER SYSTEM COMPRISING A PLURALITY OF CONNECTED RETENTION MATRIX ELEMENTS; now U.S. Pat. No. 8,814,024;   U.S. patent application Ser. No. 12/894,330, entitled FASTENER SYSTEM COMPRISING A RETENTION MATRIX AND AN ALIGNMENT MATRIX; now U.S. Pat. No. 8,757,465;   U.S. patent application Ser. No. 12/894,361, entitled FASTENER SYSTEM COMPRISING A RETENTION MATRIX; now U.S. Pat. No. 8,529,600;   U.S. patent application Ser. No. 12/894,367, entitled FASTENING INSTRUMENT FOR DEPLOYING A FASTENER SYSTEM COMPRISING A RETENTION MATRIX; now U.S. Pat. No. 9,033,203;   U.S. patent application Ser. No. 12/894,388, entitled FASTENER SYSTEM COMPRISING A RETENTION MATRIX AND A COVER; now U.S. Pat. No. 8,474,677;   U.S. patent application Ser. No. 12/894,376, entitled FASTENER SYSTEM COMPRISING A PLURALITY OF FASTENER CARTRIDGES; now U.S. Pat. No. 9,044,228;   U.S. patent application Ser. No. 13/097,865, entitled SURGICAL STAPLER ANVIL COMPRISING A PLURALITY OF FORMING POCKETS; now U.S. Pat. No. 9,295,464;   U.S. patent application Ser. No. 13/097,936, entitled TISSUE THICKNESS COMPENSATOR FOR A SURGICAL STAPLER; now U.S. Pat. No. 8,657,176;   U.S. patent application Ser. No. 13/097,954, entitled STAPLE CARTRIDGE COMPRISING A VARIABLE THICKNESS COMPRESSIBLE PORTION; now U.S. Patent Publication No. 2012/0080340;   U.S. patent application Ser. No. 13/097,856, entitled STAPLE CARTRIDGE COMPRISING STAPLES POSITIONED WITHIN A COMPRESSIBLE PORTION THEREOF; now U.S. Patent Publication No. 2012/0080336;   U.S. patent application Ser. No. 13/097,928, entitled TISSUE THICKNESS COMPENSATOR COMPRISING DETACHABLE PORTIONS; now U.S. Pat. No. 8,746,535;   U.S. patent application Ser. No. 13/097,891, entitled TISSUE THICKNESS COMPENSATOR FOR A SURGICAL STAPLER COMPRISING AN ADJUSTABLE ANVIL; now U.S. Pat. No. 8,864,009;   U.S. patent application Ser. No. 13/097,948, entitled STAPLE CARTRIDGE COMPRISING AN ADJUSTABLE DISTAL PORTION; now U.S. Pat. No. 8,978,954;   U.S. patent application Ser. No. 13/097,907, entitled COMPRESSIBLE STAPLE CARTRIDGE ASSEMBLY; now U.S. Pat. No. 9,301,755;   U.S. patent application Ser. No. 13/097,861, entitled TISSUE THICKNESS COMPENSATOR COMPRISING PORTIONS HAVING DIFFERENT PROPERTIES; now U.S. Pat. No. 9,113,865;   U.S. patent application Ser. No. 13/097,869, entitled STAPLE CARTRIDGE LOADING ASSEMBLY; now U.S. Pat. No. 8,857,694;   U.S. patent application Ser. No. 13/097,917, entitled COMPRESSIBLE STAPLE CARTRIDGE COMPRISING ALIGNMENT MEMBERS; now U.S. Pat. No. 8,777,004;   U.S. patent application Ser. No. 13/097,873, entitled STAPLE CARTRIDGE COMPRISING A RELEASABLE PORTION; now U.S. Pat. No. 8,740,038;   U.S. patent application Ser. No. 13/097,938, entitled STAPLE CARTRIDGE COMPRISING COMPRESSIBLE DISTORTION RESISTANT COMPONENTS; now U.S. Pat. No. 9,016,542;   U.S. patent application Ser. No. 13/097,924, entitled STAPLE CARTRIDGE COMPRISING A TISSUE THICKNESS COMPENSATOR; now U.S. Pat. No. 9,168,038;   U.S. patent application Ser. No. 13/242,029, entitled SURGICAL STAPLER WITH FLOATING ANVIL; now U.S. Pat. No. 8,893,949;   U.S. patent application Ser. No. 13/242,066, entitled CURVED END EFFECTOR FOR A STAPLING INSTRUMENT; now U.S. Patent Publication No. 2012/0080498;   U.S. patent application Ser. No. 13/242,086, entitled STAPLE CARTRIDGE INCLUDING COLLAPSIBLE DECK; now U.S. Pat. No. 9,055,941;   U.S. patent application Ser. No. 13/241,912, entitled STAPLE CARTRIDGE INCLUDING COLLAPSIBLE DECK ARRANGEMENT; now U.S. Pat. No. 9,050,084;   U.S. patent application Ser. No. 13/241,922, entitled SURGICAL STAPLER WITH STATIONARY STAPLE DRIVERS; now U.S. Pat. No. 9,216,019;   U.S. patent application Ser. No. 13/241,637, entitled SURGICAL INSTRUMENT WITH TRIGGER ASSEMBLY FOR GENERATING MULTIPLE ACTUATION MOTIONS; now U.S. Pat. No. 8,789,741;   U.S. patent application Ser. No. 13/241,629, entitled SURGICAL INSTRUMENT WITH SELECTIVELY ARTICULATABLE END EFFECTOR; now U.S. Patent Publication No. 2012/0074200;   U.S. application Ser. No. 13/433,096, entitled TISSUE THICKNESS COMPENSATOR COMPRISING A PLURALITY OF CAPSULES; now U.S. Pat. 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No. 13/763,042, entitled RELEASABLE TISSUE THICKNESS COMPENSATOR AND FASTENER CARTRIDGE HAVING THE SAME; now U.S. Patent Publication No. 2013/0221063;   U.S. application Ser. No. 13/763,048, entitled FASTENER CARTRIDGE COMPRISING A RELEASABLE TISSUE THICKNESS COMPENSATOR; now U.S. Patent Publication No. 2013/0221064;   U.S. application Ser. No. 13/763,054, entitled FASTENER CARTRIDGE COMPRISING A CUTTING MEMBER FOR RELEASING A TISSUE THICKNESS COMPENSATOR, now U.S. Pat. No. 9,272,406;   U.S. application Ser. No. 13/763,065, entitled FASTENER CARTRIDGE COMPRISING A RELEASABLY ATTACHED TISSUE THICKNESS COMPENSATOR; now U.S. Pat. No. 9,566,061;   U.S. application Ser. No. 13/763,021, entitled STAPLE CARTRIDGE COMPRISING A RELEASABLE COVER, now U.S. Pat. No. 9,386,984;   U.S. application Ser. No. 13/763,078, entitled ANVIL LAYER ATTACHED TO A PROXIMAL END OF AN END EFFECTOR; now U.S. Patent Publication No. 2013/0256383;   U.S. application Ser. No. 13/763,095, entitled LAYER ARRANGEMENTS FOR SURGICAL STAPLE CARTRIDGES; now U.S. Patent Publication No. 2013/0161374;   U.S. application Ser. No. 13/463,147, entitled IMPLANTABLE ARRANGEMENTS FOR SURGICAL STAPLE CARTRIDGES; now U.S. Patent Publication No. 2013/0292398;   U.S. application Ser. No. 13/763,192, entitled MULTIPLE THICKNESS IMPLANTABLE LAYERS FOR SURGICAL STAPLING DEVICES; now U.S. Patent Publication No. 2013/0146642;   U.S. application Ser. No. 13/763,161, entitled RELEASABLE LAYER OF MATERIAL AND SURGICAL END EFFECTOR HAVING THE SAME; now U.S. Patent Publication No. 2013/0153641;   U.S. application Ser. No. 13/763,177, entitled ACTUATOR FOR RELEASING A LAYER OF MATERIAL FROM A SURGICAL END EFFECTOR; now U.S. Patent Publication No. 2013/0146641;   U.S. application Ser. No. 13/763,037, entitled STAPLE CARTRIDGE COMPRISING A COMPRESSIBLE PORTION, now U.S. Patent Publication No. 2014/0224857;   U.S. application Ser. No. 13/433,126, entitled TISSUE THICKNESS COMPENSATOR COMPRISING TISSUE INGROWTH FEATURES; now U.S. Pat. No. 9,320,523;   U.S. application Ser. No. 13/433,132, entitled DEVICES AND METHODS FOR ATTACHING TISSUE THICKNESS COMPENSATING MATERIALS TO SURGICAL STAPLING INSTRUMENTS; now U.S. Patent Publication No. 2013/0256373.   U.S. application Ser. No. 13/851,703, entitled FASTENER CARTRIDGE COMPRISING A TISSUE THICKNESS COMPENSATOR INCLUDING OPENINGS THEREIN, now U.S. Pat. No. 9,572,577;   U.S. application Ser. No. 13/851,676, entitled TISSUE THICKNESS COMPENSATOR COMPRISING A CUTTING MEMBER PATH, now U.S. Patent Publication No. 2014/0291379;   U.S. application Ser. No. 13/851,693, entitled FASTENER CARTRIDGE ASSEMBLIES, now U.S. Pat. No. 9,332,984; and   U.S. application Ser. No. 13/851,684, entitled FASTENER CARTRIDGE COMPRISING A TISSUE THICKNESS COMPENSATOR AND A GAP SETTING ELEMENT, now U.S. Patent Publication No. 2014/0291380.   

     Applicant of the present application also owns the following patent applications that were filed on Feb. 24, 2014 and which are each herein incorporated by reference in their respective entireties:
     U.S. patent application Ser. No. 14/187,387, entitled STAPLE CARTRIDGE INCLUDING A BARBED STAPLE, now U.S. Patent Publication No. 2014/0166724;   U.S. patent application Ser. No. 14/187,395, entitled STAPLE CARTRIDGE INCLUDING A BARBED STAPLE, now U.S. Patent Publication No. 2014/0166725;   U.S. patent application Ser. No. 14/187,400, entitled STAPLE CARTRIDGE INCLUDING A BARBED STAPLE, now U.S. Patent Publication No. 2014/0166726;   U.S. patent application Ser. No. 14/187,383, entitled IMPLANTABLE LAYERS AND METHODS FOR ALTERING IMPLANTABLE LAYERS FOR USE WITH SURGICAL FASTENING INSTRUMENTS, now U.S. Pat. No. 9,839,422;   U.S. patent application Ser. No. 14/187,390, entitled IMPLANTABLE LAYERS AND METHODS FOR MODIFYING THE SHAPE OF THE IMPLANTABLE LAYERS FOR USE WITH A SURGICAL FASTENING INSTRUMENT, now U.S. Pat. No. 9,839,423;   U.S. patent application Ser. No. 14/187,389, entitled IMPLANTABLE LAYER ASSEMBLIES, now U.S. Pat. No.  9 , 757 , 124 ;   U.S. patent application Ser. No. 14/187,385, entitled IMPLANTABLE LAYERS COMPRISING A PRESSED REGION, now U.S. Pat. No. 9,693,777; and   U.S. patent application Ser. No. 14/187,384, entitled FASTENING SYSTEM COMPRISING A FIRING MEMBER LOCKOUT, now U.S. Pat. No. 9,775,608.   

     Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those of ordinary skill in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the various embodiments 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. 
     The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”) and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, a surgical system, device, or apparatus that “comprises,” “has,” “includes” or “contains” one or more elements possesses those one or more elements, but is not limited to possessing only those one or more elements. Likewise, an element of a system, device, or apparatus that “comprises,” “has,” “includes” or “contains” one or more features possesses those one or more features, but is not limited to possessing only those one or more features. 
     The terms “proximal” and “distal” are used herein with reference to a clinician manipulating the handle portion of the surgical instrument. The term “proximal” referring to the portion closest to the clinician and the term “distal” referring to the portion located away from the clinician. It will be further appreciated that, for convenience and clarity, spatial terms such as “vertical”, “horizontal”, “up”, and “down” may be used herein with respect to the drawings. However, surgical instruments are used in many orientations and positions, and these terms are not intended to be limiting and/or absolute. 
     Various exemplary devices and methods are provided for performing laparoscopic and minimally invasive surgical procedures. However, the person of ordinary skill in the art will readily appreciate that the various methods and devices disclosed herein can be used in numerous surgical procedures and applications including, for example, in connection with open surgical procedures. As the present Detailed Description proceeds, those of ordinary skill in the art will further appreciate that the various instruments disclosed herein can be inserted into a body in any way, such as through a natural orifice, through an incision or puncture hole formed in tissue, etc. The working portions or end effector portions of the instruments can be inserted directly into a patient&#39;s body or can be inserted through an access device that has a working channel through which the end effector and elongated shaft of a surgical instrument can be advanced. 
     Turning to the Drawings wherein like numerals denote like components throughout the several views,  FIG. 1  illustrates an exemplary surgical stapling and severing instrument  8010  suitable for use with a tissue thickness compensator assembly as described in greater detail below. The surgical stapling and severing instrument  8010  can comprise an anvil  8014  which may be repeatedly opened and closed about its pivotal attachment to an elongate staple channel  8016 . A staple applying assembly  8012  may comprise the anvil  8014  and the channel  8016 , wherein the assembly  8012  can be proximally attached to an elongate shaft  8018  forming an implement portion  8022 . When the staple applying assembly  8012  is closed, or at least substantially closed, the implement portion  8022  can present a sufficiently small cross-section suitable for inserting the staple applying assembly  8012  through a trocar. In various circumstances, the assembly  8012  can be manipulated by a handle  8020  connected to the shaft  8018 . The handle  8020  can comprise user controls such as a rotation knob  8030  that rotates the elongate shaft  8018  and the staple applying assembly  8012  about a longitudinal axis of the shaft  8018 . A closure trigger  8026 , which can pivot in front of a pistol grip  8036  to close the staple applying assembly  8012 . A closure release button  8038  can be outwardly presented on the handle  8020  when the closure trigger  8026  is clamped such that the release button  8038  can be depressed to unclamp the closure trigger  8026  and open the staple applying assembly  8012 , for example. A firing trigger  8034 , which can pivot in front of the closure trigger  8026 , can cause the staple applying assembly  8012  to simultaneously sever and staple tissue clamped therein. In various circumstances, multiple firing strokes can be employed using the firing trigger  8034  to reduce the amount of force required to be applied by the surgeon&#39;s hand per stroke. In certain embodiments, the handle  8020  can comprise one or more rotatable indicator wheels such as, for example, rotatable indicator wheel  8041  which can indicate the firing progress. A manual firing release lever  8042  can allow the firing system to be retracted before full firing travel has been completed, if desired, and, in addition, the firing release lever  8042  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 instrument  8010  and other surgical stapling and severing instruments suitable for use with the present disclosure are described, for example, in U.S. patent application Ser. No. 13/851,693, entitled FASTENER CARTRIDGE ASSEMBLY, and filed on Mar. 27, 2013, the entire disclosure of which is incorporated herein by reference. Furthermore, powered surgical stapling and severing instruments can also be utilized with the present disclosure. See, for example, U.S. Patent Application Publication No. 2009/0090763 A1, entitled POWERED SURGICAL STAPLING DEVICE, and filed on Aug. 8, 2008, the entire disclosure of which is incorporated herein by reference. 
     With reference to  FIGS. 2 and 3 , a firing assembly such as, for example, firing assembly  9090  can be utilized with the surgical stapling and severing instrument  8010  to advance a wedge sled  9126  which comprises a plurality of wedges  9204  configured to deploy staples from the staple applying assembly  8012  into tissue captured between the anvil  8014  and the elongate staple channel  8016 . Furthermore, an E-beam  9102  at a distal portion of the firing assembly  9090  may facilitate separate closure and firing as well as spacing of the anvil  8014  from the elongate staple channel  8016  during firing. The E-beam  9102  may include a pair of top pins  9110 , a pair of middle pins  9112  which may follow portion  9218  of the wedge sled  9126 , and a bottom pin or foot  9114 , as well as a sharp cutting edge  9116  which can be configured to sever the captured tissue as the firing assembly  9090  is advanced distally. In addition, integrally formed and proximally projecting top guide  9118  and middle guide  9120  bracketing each vertical end of the cutting edge  9116  may further define a tissue staging area  9122  assisting in guiding tissue to the sharp cutting edge  9116  prior to being severed. The middle guide  9120  may also serve to engage and fire the staple applying assembly  8012  by abutting a stepped central member  9124  of the wedge sled  9126  ( FIG. 2 ) that effects staple formation by the staple applying assembly  8012 . 
     In various circumstances, a staple cartridge can comprise means for compensating for thickness of tissue captured within staples deployed from a staple cartridge. Referring to  FIG. 4 , a staple cartridge, such as staple cartridge  10000 , for example, can be utilized with the surgical stapling and severing instrument  8010  and can include a rigid first portion, such as support portion  10010 , for example, and a compressible second portion, such as tissue thickness compensator  10020 , for example. The support portion  10010  can comprise a cartridge body and a plurality of staple cavities  10012 . A staple  10030 , for example, can be removably positioned in each staple cavity  10012 . Referring primarily to  FIGS. 4 and 5 , each staple  10030  can comprise a base  10031  and one or more legs  10032  extending from the base  10031 . Prior to the staples  10030  being deployed, the bases  10031  of the staples  10030  can be supported by staple drivers positioned within the support portion  10010  and, concurrently, the legs  10032  of the staples  10030  can be at least partially contained within the staple cavities  10012 . In various circumstances, the staples  10030  can be deployed between an unfired position and a fired position such that the legs  10032  move through the tissue thickness compensator  10020 , penetrate through a top surface of the tissue thickness compensator  10020 , penetrate the tissue T, and contact an anvil positioned opposite the staple cartridge  10000 . As the legs  10032  are deformed against the anvil, the legs  10032  of each staple  10030  can capture a portion of the tissue thickness compensator  10020  and a portion of the tissue T within each staple  10030  and apply a compressive force to the tissue. Further to the above, the legs  10032  of each staple  10030  can be deformed downwardly toward the base  10031  of the staple to form a staple entrapment area in which the tissue T and the tissue thickness compensator  10020  can be captured. In various circumstances, the staple entrapment area can be defined between the inner surfaces of the deformed legs  10032  and the inner surface of the base  10031 . 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 base, and/or the extent in which the legs are deformed, for example. 
     In use, further to the above and referring primarily to  FIG. 4 , an anvil, such as anvil  8014  of the surgical stapling and severing instrument  8010 , can be moved into a closed position opposite the staple cartridge  10000  by depressing the closure trigger  8026  to advance the E-beam  9102 . The anvil  8014  can position tissue against the tissue thickness compensator  10020  and, in various circumstances, compress the tissue thickness compensator  10020  against the support portion  10010 , for example. Once the anvil  8014  has been suitably positioned, the staples  10030  can be deployed, as also illustrated in  FIG. 4 . In various circumstances, as mentioned above, a staple-firing sled  10050 , which is similar in many respects to the sled  9126  (See  FIG. 3 ), can be moved from a proximal end of the staple cartridge  10000  toward a distal end  10002 , as illustrated in  FIG. 5 . As the firing assembly  9090  is advanced, the sled  10050  can contact the staple drivers  10040  and lift the staple drivers  10040  upwardly within the staple cavities  10012 . In at least one example, the sled  10050  and the staple drivers  10040  can each comprise one or more ramps, or inclined surfaces, which can co-operate to move the staple drivers  10040  upwardly from their unfired positions. As the staple drivers  10040  are lifted upwardly within their respective staple cavities  10012 , the staple drivers  10040  can lift the staples  10030  upwardly such that the staples  10030  can emerge from their staple cavities  10012 . In various circumstances, the sled  10050  can move several staples upwardly at the same time as part of a firing sequence. 
     As discussed above, and referring to  FIG. 5 , the staple legs  10032  of the staples  10030  can extend into the compensator  10020  beyond the support portion  10010  when the staples  10030  are in their unfired positions. In various circumstances, the tips of the staple legs  10032 , or any other portion of the staple legs  10032 , may not protrude through a top tissue-contacting surface  10021  of the tissue thickness compensator  10020  when the staples  10030  are in their unfired positions. In certain circumstances, the tips of the staple legs  10032  can comprise sharp tips which can incise and penetrate the tissue thickness compensator  10020 . 
     In various circumstances, it may be preferable to prevent and/or limit frictional forces between a tissue thickness compensator and a staple. Referring now to  FIGS. 6-8 , a tissue thickness compensator  20220  for use with a staple cartridge assembly  20200  can include a plurality of clearance apertures  20224  extending at least partially through the tissue thickness compensator  20220 . In various circumstances, the staple cartridge assembly  20200  can include a staple cartridge body  20210  and a tissue thickness compensator  20220  releasably secured relative to the staple cartridge body  20210 . The cartridge body  20210  can include a cartridge deck  20211  and a plurality of staple cavities  20212  defined through the cartridge deck  20211  and into the body of the staple cartridge body  20210 , for example. Staples  20230  can be removably positioned in the staple cavities  20212 , for example. The tissue thickness compensator  20220  can include a tissue-contacting surface  20221  ( FIG. 7 ) and a deck-contacting surface  20222  ( FIG. 6 ). The deck-contacting surface  20222  can be releasably positioned against the deck  20211  of the cartridge body  20210 , for example, and the tissue-contacting surface  20221  can be positioned against tissue T to be stapled, for example. Clearance apertures  20224  can extend through the deck-contacting surface  20222  and into the tissue thickness compensator  20220  and may comprise holes, slits, gaps, bores, openings, and/or cleared pathways, for example, within the tissue thickness compensator  20220 . 
     Referring primarily to  FIGS. 7 and 8 , staples  20230  can be positioned in the staple cavities  20212  of the cartridge body  20210 . Each staple  20230  can include a base  20231  and a pair of staple legs  20232 , for example, which can extend from the base  20231 . Each staple leg  20232  can extend from opposite ends of the base  20231 . Referring primarily to  FIG. 7 , one or more of the clearance apertures  20224  in the tissue thickness compensator  20220  can include an opening in the deck-contacting surface  20222 . The opening of a clearance aperture  20224  can be aligned with a corresponding staple leg  20232  that is positioned in a staple cavity  20212 . For example, a single staple leg  20232  can be aligned with the opening of a single clearance aperture  20224  when the tissue thickness compensator  20220  is secured relative to the cartridge body  20210 . In certain circumstances, a staple leg  20232  can extend into each clearance aperture  20224 , such that at least a portion of the staple  20230  is embedded in the tissue thickness compensator  20220 , for example. For example, referring primarily to  FIG. 7 , a staple  20230  can include a first staple leg  20232   a  and a second staple leg  20232   b . Furthermore, the tissue thickness compensator  20220  can include a first clearance aperture  20224   a  aligned with the first staple leg  20232   a , and a second clearance aperture  20224   b  aligned with the second staple leg  20232   b , for example. Prior to deployment of the staple  20230 , the first staple leg  20232   a  can extend partially through the first clearance aperture  20224   a , and the second staple leg  20232   b  can extend partially through the second clearance aperture  20224   b , for example. The tissue thickness compensator  20220  can include additional clearance apertures  20224  that are not aligned with staple legs  20232 , for example. In certain circumstances, the staple cartridge assembly  20200  can include additional staples  20230  and/or staple legs  20232  that are not aligned with clearance apertures  20224 , for example. 
     The staples  20230  can be moveable from an unfired configuration ( FIG. 7 ) to a fired configuration ( FIG. 8 ). Each staple  20230  can be moved along a staple axis when moving between the unfired configuration and the fired configuration. When in the unfired configuration, the staple legs  20232  can extend from the staple cavities  20212  and into the tissue thickness compensator  20220 , for example. The staple legs  20232  can be partially embedded in the tissue thickness compensator  20220  when the staples  20230  are in the unfired configuration, for example. Furthermore, at least a portion of the staple legs  20232  can be aligned with and/or positioned within the clearance apertures  20224  of the tissue thickness compensator  20220  when the staples are in the unfired configuration, for example. In other circumstances, the staple legs  20232  can be positioned entirely within the staple cavity  20212  when in the unfired configuration, and can be aligned with the clearance apertures  20224  positioned above the cartridge deck  20211  ( FIG. 6 ), for example. 
     The staples  20230  can move from the unfired configuration ( FIG. 7 ) to the fired configuration ( FIG. 8 ) during a firing stroke, as described herein. A staple driver  20240  can be positioned within each staple cavity  20212 . The staple driver  20240  within each staple cavity  20212  can be pushed toward the cartridge deck  20211  ( FIG. 6 ), for example, to drive the staple  20230  into tissue T and toward an anvil  20260  ( FIG. 8 ) which can be similar in many respects to other anvils described herein such as, for example, the anvil  8014  ( FIG. 1 ). As each staple  20230  moves from the unfired configuration to the fired configuration, the staple legs  20232  can move through the clearance apertures  20224  in the tissue thickness compensator  20220 . The clearance apertures  20224  can have a predefined trajectory within the tissue thickness compensator  20220 . For example, the clearance apertures  20224  can extend along an axis that is perpendicular to and/or substantially perpendicular to the tissue-contacting surface  20221  ( FIG. 7 ) and/or the deck-contacting surface  20222  ( FIG. 6 ) of the tissue thickness compensator  20220 . In other circumstances, the clearance apertures  20224  can extend along an axis that is oriented at an oblique angle relative to the tissue-contacting surface  20221  and/or the deck-contacting surface  20222  of the tissue thickness compensator  20220 , for example. In certain circumstances, a group of the clearance apertures  20224  can be parallel. In some circumstances, all of the clearance apertures  20224  within the tissue thickness compensator  20220  can be parallel, for example. The clearance apertures  20224  can comprise a partially curved trajectory and/or a partially linear trajectory. Other characteristics and features of the clearance apertures  20224  are described in greater detail in U.S. patent application Ser. No. 13/851,693, entitled FASTENER CARTRIDGE ASSEMBLY, and filed on Mar. 27, 2013, the entire disclosure of which is incorporated herein by reference. Methods and techniques for modifying a tissue thickness compensator to include clearance apertures such as, for example, the clearance apertures  20224  are described below in greater detail. 
     Referring now to  FIGS. 9-12 , an end effector  22090  of a surgical instrument similar in many respects to the surgical instrument  8010 , for example, can comprise a first jaw including a fastener cartridge assembly  22000  and a second jaw including an anvil  10060 . The first jaw can include a staple cartridge channel  10070  which can be configured to removably receive the cartridge assembly  22000 . Alternatively, the staple cartridge channel  10070  and the cartridge assembly  22000  can comprise an integral unit. In various circumstances, the anvil  10060  can be moved between an open position and a closed position ( FIGS. 9-12 ). In the open position of the anvil  10060 , the anvil  10060  can be positioned on a first side of a patient&#39;s tissue T ( FIGS. 10-12 ) and the cartridge assembly  22000  can be positioned on a second, or opposite, side of the tissue T, for example. When the anvil  10060  is moved into its closed position, the anvil  10060  can compress the tissue T against the cartridge assembly  22000 . Alternatively, the first jaw including the cartridge assembly  22000  can be moved relative to the anvil  10060 . A firing member  10052 , which is similar in many respects to the firing assembly  9090  ( FIG. 3 ), can be advanced distally from a proximal end  22001  of the cartridge assembly  22000  toward a distal end  22002  of the cartridge assembly  22000  to eject fasteners, such as staples  22030 , for example, removably stored in a cartridge body  22010  of the cartridge assembly  22000  as the firing member  10052  is advanced from the proximal end  22001  toward the distal end  22002  of the cartridge assembly  22000 . 
     Further to the above, the staples  22030  can be supported by staple drivers  10040  which are movably positioned within staple cavities  22012  defined in the cartridge body  22010 . Moreover, the firing member  10052  can be configured to advance a staple-firing sled  10050  distally within the cartridge body  22010  as the firing member  10052  is moved from the proximal end  22001  toward the distal end  22002 . In such circumstances, the staple-firing sled  10050  can be configured to lift the staple drivers  10040 , and the staples  22030  supported thereon, toward the anvil  10060 . In essence, further to the above, the staple drivers  10040  can move the staples  22030  from an unfired position ( FIG. 10 ) to a fired position ( FIGS. 11 and 12 ) wherein the staples  22030  can contact the anvil  10060  and be deformed between an undeformed configuration ( FIG. 10 ) and a deformed configuration ( FIGS. 11 and 12 ). The anvil  10060  can comprise forming pockets  10062  which can be configured to receive and deform the staples  22030 . Staples  22030  can be the same as or similar to staples  10030 , for example and/or any other staples disclosed herein, and, as such, staples  22030  are not described in greater detail herein. The reader will note, however, that the staples  22030  can comprise any suitable shape and/or suitable dimensions, such as width and/or height, for example, in their undeformed configuration and/or their deformed configuration. For instance, the staples  22030  can, in certain circumstances, comprise a height which does not extend above a deck surface  22011  of the cartridge body  22010  when the staples  22030  are in their unfired positions while, in other circumstances, the staples  22030  can comprise a height in which the legs of the staples  22030  extend upwardly from the deck surface  22011  when the staples  22030  are in their unfired positions such that the legs of the staples  22030  are at least partially embedded in a tissue thickness compensator  22010  of the cartridge assembly  22000 . 
     With continued reference to the embodiment depicted in  FIGS. 9-12 , further to the above, the cartridge assembly  22000  can comprise a cartridge body  22010  and a tissue thickness compensator  22020 . In various circumstances, the cartridge body  22010  can be similar to the support portion  10010 , for example, in many respects and, as a result, many of such respects are not repeated herein for the sake of brevity. Furthermore, the tissue thickness compensator  22020  can be similar to the tissue thickness compensator  10020 , for example, in many respects. Further to the above, the firing member  10052  can include a cutting portion  10053  which can be configured to transect the tissue positioned between the anvil  10060  and the tissue thickness compensator  22020  as the firing member  10052  is advanced distally. In various circumstances, as a result, the firing member  10052  can be configured to concurrently fire the staples  22030  to staple the tissue T and cut the tissue T. In certain circumstances, the firing process can at least partially lead the cutting process. Stated another way, the cutting process can lag the firing process. In such circumstances, a portion of the tissue T can be stapled and then incised. 
     As illustrated in  FIGS. 9-12 , the cartridge body  22010  can include a cartridge knife slot  22015  which can be configured to receive a portion of the firing member  10052  as the firing member  10052  is advanced distally. Further to the above, the anvil  10060  can include an anvil knife slot  10065  which can be configured to receive a portion of the firing member  10052  as the firing member  10052  is advanced distally. In various circumstances, the tissue thickness compensator  22020  can comprise a tissue thickness compensator knife slot  22025  which can be aligned with the anvil knife slot  10065  and the cartridge knife slot  22015  such that the firing member  10052  can pass through the cartridge knife slot  22015 , the anvil knife slot  10065 , and the tissue thickness compensator knife slot  22025  simultaneously. In various circumstances, the anvil knife slot  10065  can extend over the tissue thickness compensator knife slot  22025  such that the cutting portion  10053  of the firing member  10052  can pass through the cartridge knife slot  22015 , the anvil knife slot  10065 , and the tissue thickness compensator knife slot  22025  simultaneously. The tissue thickness compensator knife slot  22025  can define a tissue thickness compensator knife path for the cutting portion  10053  wherein the tissue thickness compensator knife path can be parallel to the anvil knife path and the cartridge knife path. In various circumstances, the tissue thickness compensator knife path can be longitudinal while, in certain circumstances, the tissue thickness compensator knife path can be curved. Further to the above, curved end effectors and curved fastener cartridges are disclosed in U.S. Patent Application Publication No. 2008/0169329. The entire disclosure of U.S. patent application Ser. No. 11/652,164, entitled CURVED END EFFECTOR FOR A SURGICAL STAPLING DEVICE, filed on Jan. 11, 2007, now U.S. Patent Application Publication No. 2008/0169329, is hereby incorporated by reference herein. In such circumstances, a tissue thickness compensator can be curved. In at least one such embodiment, the tissue thickness compensator can be curved to match the curvature of the cartridge body of the fastener cartridge. Methods and techniques for modifying a tissue thickness compensator to include a knife slot such as, for example, the knife slot  22025  are described below. 
     Further to the above, referring primarily to  FIG. 9 , the tissue thickness compensator knife slot  22025  can extend between a first stapling portion  22021   a  which can be stapled by a first group of staples  22030  and a second stapling portion  22021   b  which can be stapled by a second group of staples  22030 . The knife slot  22025  can releasably connect the first stapling portion  22021   a  to the second stapling portion  22021   b . In use, as illustrated in  FIG. 9 , the cutting portion  10053  can be advanced distally through the knife slot  22025  to transect the knife slot  22025  and separate the first stapling portion  22021   a  and the second stapling portion  22021   b . In certain circumstances, the knife slot  22025  can comprise a plurality of connectors, or bridges,  22026  which can connect the first stapling portion  22021   a  and the second stapling portion  22021   b  prior to being transected by the cutting portion  10053 . In various circumstances, the connectors  22026  can have the same thickness as the first stapling portion  22021   a  and/or the second stapling portion  22021   b , at least when the tissue thickness compensator  22020  is in an uncompressed state. In at least one such circumstance, the connectors  22026 , the first stapling portion  22021   a , and/or the second stapling portion  22021   b  can be unitarily and integrally formed from a flat, or at least substantially flat, piece of material, for example. In various other circumstances, the first stapling portion  22021   a  can comprise a first thickness, the second stapling portion  22021   b  can comprise a second thickness, and the connectors  22026  can comprise a third thickness, wherein one or more of the first thickness, the second thickness, and the third thickness can be different than the other thicknesses. 
     The knife slot  22025  can further comprise apertures, such as apertures  22024 , for example, defined therein. For instance, the apertures  22024  can be elongate and can extend longitudinally along the knife slot  22025 . In various other circumstances, the apertures in the knife slot  22025  can comprise any suitable arrangement. In certain circumstances, the apertures  22024  can comprise perforations positioned intermediate the connectors  22026  which can be formed utilizing a laser cutting operation, for example. In some circumstances, the apertures  22024  can be cut from a sheet of material to form the tissue thickness compensator  22020  such that the apertures  22024  and the connectors  22026  are arranged in an alternating arrangement, for example. In other instances, the tissue thickness compensator  22020  can be molded with apertures  22024  already formed therein. In various circumstances, one or more of the apertures  22024  can comprise through holes, for example. In various circumstances, one or more of the apertures  22024  can comprise clearance apertures, for example. In certain instances, one or more of the apertures  22024  may not comprise through holes and may instead comprise reductions in the thickness of the knife slot  22025 , for example. Methods and techniques for modifying a tissue thickness compensator to include apertures such as, for example, the apertures  22024  are described below. 
     Further to the above, referring again to  FIGS. 9-11 , patient tissue can be positioned intermediate the anvil  10060  of the end effector  22090  and the tissue thickness compensator  22020  of the cartridge assembly  22000  when the anvil  10060  is in an open position. When the anvil  10060  is moved into a closed position, a bottom surface, or tissue-contacting surface,  10063  of the anvil  10060  can contact the tissue T and push the tissue T toward a deck surface  22011  of the cartridge body  22010 . The tissue T can contact a top surface, or tissue contacting surface,  22021  of the tissue thickness compensator  22020  wherein, when the anvil  10060  is moved into its closed position, the anvil  10060  can press the tissue T against the tissue thickness compensator  22020  and, further to the above, compress the tissue thickness compensator  22020  against the deck surface  22011  of the cartridge body  22010 . In various circumstances, the tissue thickness compensator  22020  can comprise a bottom surface  22029  which can abut the deck surface  22011 . In some circumstances, a gap may be present between the bottom surface  22029  and the deck surface  22011  before the tissue thickness compensator  22020  is compressed against the cartridge body  22010 . In such circumstances, the tissue thickness compensator  22020  may first translate toward the cartridge body  22010  before being compressed thereagainst. When the tissue thickness compensator  22020  is compressed against the cartridge body  22010 , in various circumstances, the first stapling portion  22021   a  and/or the second stapling portion  22021   b  of the tissue thickness compensator  22020  may move laterally. For instance, the first stapling portion  22021   a  and/or the second stapling portion  22021   b  may move laterally away from the cartridge knife slot  22015 . In various circumstances, the connectors  22026  can be configured to inhibit such lateral movement between the first stapling portion  22021   a  and the second stapling portion  22021   b . In various circumstances, referring primarily to  FIG. 11 , the connectors  22026  can be configured to stretch to permit some relative lateral movement between the first stapling portion  22021   a  and the second stapling portion  22021   b  when the anvil  10060  is closed. In the event that the anvil  10060  is reopened, the connectors  22026  can be configured to elastically return, or at least substantially return, to their unstretched configuration and, as a result, pull the first stapling portion  22021   a  and the second stapling portion  22021   b  laterally back toward their original positions, illustrated in  FIG. 10 . Moreover, the anvil  10060  can compress the tissue T when the anvil  10060  is moved into its closed position. In such circumstances, the tissue T may at least partially flow into the apertures  22024 . 
     Upon reviewing  FIGS. 10-12 , the reader will appreciate that the knife slot  22025  of the tissue thickness compensator  22020  comprises less material along the longitudinal length thereof than the first stapling portion  22021   a  and/or the second stapling portion  22021   b . Stated another way, a longitudinal cross-section through the first stapling portion  22021   a  and/or the second stapling portion  22021   b  would transect a first amount of material while a longitudinal cross-section through the knife slot  22025  would transect a second amount of material which is less than the first amount of material. 
     Once the anvil  10060  has been suitably positioned, further to the above, the firing member  10052  can be advanced distally to fire the staples, as illustrated in  FIG. 11 , and incise the tissue T and the connectors  22026 , as illustrated in  FIG. 12 . Furthermore, the tissue thickness compensator incision force, the tissue incision force, the tissue thickness compensator drag force, and/or the tissue drag force can dull the cutting portion  10053  of the firing member  10052 . A dull knife may not be able to transect the tissue T and/or the tissue thickness compensator  22020 , for example, according to a preferred manner. With primary reference to  FIG. 12 , the cutting portion  10053  can comprise a first knife edge zone  10053   a , a second knife edge zone  10053   b , and/or a third knife edge zone  10053   c , for example, wherein the first knife edge zone  10053   a  is positioned vertically above the second knife edge zone  10053   b , and wherein the second knife edge zone  10053   b  is positioned vertically above the third knife edge zone  10053   c , for example. The cutting portion  10053  can comprise any suitable number and/or location of knife edge zones wherein the knife edge zones depicted in  FIG. 12  have been selected for the purposes of discussion. Further to the above, the first knife edge zone  10053   a  can be configured to transect the tissue T while the second knife edge zone  10053   b  can be configured to transect the tissue thickness compensator  22020 . As a result, the first knife edge zone  10053   a  may experience the tissue incision force and/or the tissue drag force discussed above. Such forces may wear or dull the first knife edge zone  10053   a  at a first rate. The second knife edge zone  10053   b  may experience the tissue thickness compensator incision force and/or the tissue thickness compensator drag force discussed above. Such forces may wear or dull the second knife edge zone  10053   b  at a second rate. In various circumstances, the second rate can be different than the first rate. 
     Turning now to  FIGS. 13 and 14 , a fastener cartridge  22400  can comprise a tissue thickness compensator  22420  which can include a first stapling portion  22421   a  and a second stapling portion  22421   b  which are connected by a knife slot  22425 . The knife slot  22425  can comprise an angled longitudinal connector  22426 . The angled longitudinal connector  22426  can extend between a proximal end  22401  of the knife slot  22425  and a distal end  22402  of the knife slot  22425 . In some circumstances, the angled longitudinal connector  22426  can extend the entire length of the knife slot  22425  while, in other circumstances, the angled longitudinal connector  22426  can extend less than the length of the knife slot  22425 . The angled longitudinal connector  22426  can extend between a top surface  22428  of the tissue thickness compensator  22420  and a bottom surface  22429  of the tissue thickness compensator  22420 . In some circumstances, the angled longitudinal connector  22426  can extend the entire distance between the top surface  22428  and the bottom surface  22429  while, in other circumstances, the angled longitudinal connector  22426  can extend less than the distance between the top surface  22428  and the bottom surface  22429 . In various circumstances, the proximal end of the longitudinal connector  22426  can extend from the top surface  22428  of the tissue thickness compensator while the distal end of the longitudinal connector  22426  can extend from the bottom surface  22429 . Alternatively, the distal end of the longitudinal connector  22426  can extend from the top surface  22428  of the tissue thickness compensator while the proximal end of the longitudinal connector  22426  can extend from the bottom surface  22429 . In various circumstances, the longitudinal connector  22426  can comprise a thin bridge (i.e. less than the full thickness of the tissue thickness compensator  22420 ) or a series of thin bridges that join the first stapling portion  22421   a  which can be stapled by a first group of staples  22030  to the second stapling portion  22421   b  which can be stapled by a second group of staples  22030 , for example. These thin, angled bridges, and/or the longitudinal connector  22426 , could distribute the wear across the second knife edge zone  10053   b , rather than concentrating it on one spot. In various circumstances, as a result, the wear occurring on the second knife edge zone  10053   b  may be equal to, or closer to being equal to, the wear occurring at the first knife edge zone  10053   a , for example. 
     Referring now to  FIGS. 15-17 , an exemplary tissue thickness compensator assembly  1000  may include a first layer  1002  and a second layer  1004  attachable to the first layer  1002 . The tissue thickness compensator assembly  1000  can be utilized with a surgical instrument such as, for example, the surgical instrument  8010  ( FIG. 1 ). In addition, the tissue thickness compensator assembly  1000  can be utilized in a similar manner as and can replace the tissue thickness compensator  22020  of the cartridge assembly  22000  of the end effector  22090  ( FIG. 9 ). For example, the second layer  1004  of the tissue thickness compensator assembly  1000  may include a first portion  1006  which can be positioned on the deck surface  22011  on a first side of the cartridge knife slot  22015  in a similar fashion to the first stapling portion  22021   a  and a second portion  1008  which can be positioned on the deck surface  22011  on a second side, opposite the first side, of the cartridge knife slot  22015  in a similar fashion to the second stapling portion  22021   b  ( FIGS. 9-11 ). In various instances, the first portion  1006  and the second portion  1008  of the second layer  1004  can be spaced apart and may comprise a gap  1010  therebetween which can comprise a knife path for the cutting portion  10053  of the firing member  10052  and may extend at least partially over the cartridge knife slot  22015  when the tissue thickness compensator assembly  1000  is assembled with the cartridge end effector  22090 . In certain instances, the first layer  1002  can be configured to couple the first portion  1006  and the second portion  1008  and extend at least partially over the gap  1010 , as illustrated in  FIG. 17 , for example. 
     In use, tissue T can be captured between the anvil  10060  and a tissue contacting surface  1012  of the first layer  1002 . As the firing member  10052  is advanced, a first group of staples  20030  can be deployed to staple the first portion  1006  and a second group of staples can be deployed to staple the second portion  1008 . The first and second groups of staples can be configured to penetrate through a first deck contacting surface  1007  and a second deck contacting surface  1009 , respectively, of the second layer  1004 , then through the tissue contacting surface  1012  of the first layer, and then through the captured tissue T to contact the pockets  10062  of the anvil  10060 . Furthermore, the advancement of the firing member  10052  can cause the cutting portion  10053  to be advanced distally through the gap  1010  of the tissue thickness compensator assembly  1000 . The cutting portion  10053  may transect the first layer  1002  while advancing through the gap  1010  thereby separating the first portion  1006  and the second portion  1008  of the second layer  1004 . 
     Referring again to  FIG. 17 , the first layer  1002  of the tissue thickness compensator assembly  1000  may comprise a first height H 1 , the first portion  1006  of the second layer  1004  may comprise a second height H 2 , and the second portion  1008  of the second layer  1004  may comprise a third height H 3 . In certain circumstances, as illustrated in  FIG. 17 , the second height H 2  and the third height H 3  can be the same or substantially the same. In other circumstances, the second height H 2  can be different from the third height H 3 . In certain circumstances, the first height H 1  can be less than the second height H 2  and/or the third height H 3 , as illustrated in  FIG. 17 . The first layer  1002  of the tissue thickness compensator assembly  1000  may comprise a first density, the first portion  1006  of the second layer  1004  may comprise a second density, and the second portion  1008  of the second layer  1004  may comprise a third density. In certain circumstances, as illustrated in  FIG. 17 , the second density and the third density can be the same or substantially the same. In other circumstances, the second density can be different from the third density and/or different from the first density of the first layer  1002 . The material compositions of the first portion  1006  and the second portion  1008  can be the same, or at least substantially the same. In other circumstances, the material compositions of the first portion  1006  and the second portion  1008  can be different from each other and/or can be different from the material composition of the first layer  1002 . 
     As described above, repeated use of the cutting portion  10053  to cut tissue T and tissue thickness compensator material may dull the cutting portion  10053 . To slow the dulling process, it may be desirable to reduce the tissue thickness compensator material that is cut by the cutting portion  10053 . An additional benefit can be a reduction in the forces needed to advance the firing member  10052  distally during a firing stroke. In order to reduce the dulling of the cutting portion  10053 , the first layer  1002  can be comprised, at least partially, of a thin film, for example. In such circumstances, the first height H 1  can be significantly less than the second height H 2  and the third height H 3 , as illustrated in  FIG. 17 . In certain circumstances, the first layer  1002  may comprise a uniform, or substantially uniform, height therethrough, as illustrated in  FIG. 17 . In other circumstances, a gap bridging portion  1014  of the first layer  1002  may extend at least partially over the gap  1010  and may be thinner than the remainder of the first layer  1002 . The cutting portion  10053  may transect the gap bridging portion  1014  of the first layer  1002  while advancing through the gap  1010  between the first portion  1006  and the second portion  1008  of the second layer  1004  which may reduce the resistance experienced by the cutting portion  10053  and/or slow the dulling of the cutting portion  10053 . In any event, the first layer  1002  can be configured to maintain a coupling engagement with the first portion  1006  and the second portion  1008  of the second layer  1004  prior to being transected, and to present the cutting portion  10053  with a reduced resistance as the cutting portion  10053  is advanced to transect the first layer  1002 . 
     To further reduce the dulling of the cutting portion  10053  and/or reduce the resistance experienced by the cutting portion  10053 , the gap bridging portion  1014  may comprise a perforated segment  1016  along the knife path defined by the gap  1010 , as illustrated in  FIG. 16 . The perforated segment  1016  can include a plurality of perforations  1018  which can be cut into the first layer  1002  prior to the assembly of the first layer  1002  to the second layer  1004 , for example. The perforations  1018  can reduce the interaction between the cutting portion  10053  and the first layer  1002  as the cutting portion  10053  is advanced through the knife path defined by the gap  1010 , which may slow the dulling of the cutting portion  10053  and/or reduce the resistance experienced by the cutting portion  10053 . 
     In various circumstances, as described in greater detail below, the tissue thickness compensator assembly  1000  can be comprised of one or more biocompatible materials. In certain circumstance, the first layer  1002  can be comprised of a biocompatible buttress material and/or plastic material, such as polydioxanone (PDS) and/or polyglycolic acid (PGA), for example, and the second layer  1004  can be comprised of a bioabsorbable foam material and/or a compressible haemostatic material, such as oxidized regenerated cellulose (ORC), for example. In certain circumstances, the first layer  1002  can be a thin film comprising a bioabsorbable material such as polyglycolic acid (PGA) which is marketed under the trade name Vicryl, polylactic acid (PLA or PLLA), polydioxanone (PDS), polyhydroxyalkanoate (PHA), poliglecaprone 25 (PGCL) which is marketed under the trade name Monocryl, polycaprolactone (PCL), and/or a composite of PGA, PLA, PDS, PHA, PGCL and/or PCL, for example. In certain circumstances, the first portion  1006  and/or the second portion  1008  of the second layer  1004  can be comprised of a lyophilized foam comprising polylactic acid (PLA) and/or polyglycolic acid (PGA), for example. In certain circumstances, the first portion  1006  and/or the second portion  1008  of the second layer  1004  can be comprised of biocompatible foam which may comprise a porous, open cell foam and/or a porous, closed cell foam. 
     Referring again to  FIGS. 15 and 17 , the first layer  1002  can be at least partially disposed over the second layer  1004  such that the second layer  1004  may be positioned between the first layer  1002  and the deck surface  22011  ( FIG. 9 ) when the tissue thickness compensator assembly  1000  is assembled with the end effector  22090  ( FIG. 9 ). In other circumstances, the first layer  1002  can be positioned beneath the first portion  1006  and the second portion  1008  (not shown) such that the first layer  1002  may be positioned between the second layer  1004  and the deck surface  22011  ( FIG. 9 ) when the tissue thickness compensator assembly  1000  is assembled with the end effector  22090  ( FIG. 9 ). In any event, the first layer  1002  can be attached to a first contacting surface  1020  of the first portion  1006  and a second contacting surface  1022  of the second portion  1008  of the second layer  1004 . The first layer  1002  can be attached to the second layer  1004  via a thermal pressing process involving the application of heat and/or pressure, as described in greater detail below. In other circumstances, the first layer  1002  can be attached to the second layer  1004  by a biocompatible adhesive material such as a fibrin and/or protein hydrogel, for example. Other means for attaching the first layer  1002  to the second layer  1004  are contemplated by the present disclosure. 
     Referring now to  FIGS. 21 and 22 , the first layer  1002  can be at least partially embedded into the first portion  1006  and/or the second portion  1008  of the second layer  1004 . In such circumstances, the tissue thickness compensator assembly  1000  can be prepared using a mold  1024 , for example, as illustrated in  FIG. 21 . In various instances, an organic solution comprising a polymer such as, for example, polylactic acid (PLA) and/or polyglycolic acid (PGA) can be poured into the mold  1024 . The first layer  1002  can be immersed into the organic solution. As illustrated in  FIG. 22 , a central shelf  1026  and a central beam  1027  of a mold cover  1028  can trap the first layer  1002  therebetween to ensure that the first layer  1002  remains immersed in the organic solution which can then be lyophilized using conventional lyophilization techniques and/or any other suitable techniques, for example. Upon completion of the lyophilization process, and/or any other suitable process, the mold cover  1028  can be removed and the tissue thickness compensator assembly  1000  can be recovered from the mold  1028 . 
     As illustrated in  FIG. 21 , the first layer  1002  of the tissue thickness compensator  1000  can be partially positioned within the first portion  1006  and the second portion  1008  of the second layer  1004 . In certain circumstances, the first layer  1002  can be partially positioned within one of the first portion  1006  and the second portion  1008  and attached to a top surface or a bottom surface of the other one of the first portion  1006  and the second portion  1008 . 
     In certain circumstances, the central beam  1027  and the shelf  1026  can at least partially extend along an axis that is parallel or substantially parallel to the first deck contacting surface  1007  and/or the second deck contacting surface  1009  when the cover  1028  is in a closed configuration with mold  1024 , as illustrated in  FIG. 22 . In such circumstances, the first layer  1002  can be embedded into the first portion  1006  and/or the second portion  1008  such that first layer  1002  is positioned or substantially positioned in a parallel or substantially parallel relationship with the first deck contacting surface  1007  and/or the second deck contacting surface  1009 . In other circumstances, although not illustrated, the central beam  1027  and the shelf  1026  can at least partially extend along an axis that is at an oblique angle with the first deck contacting surface  1007  and/or the second deck contacting surface  1008  when the cover  1028  is in a closed configuration with mold  1024 . In such circumstances, the first layer  1002  can be embedded into the first portion  1006  and/or the second portion  1008  such that first layer  1002  is positioned or substantially positioned at an oblique angle with respect to the first deck contacting surface  1007  and/or the second deck contacting surface  1009 . Other techniques for partially embedding the first layer  1002  into the first portion  1006  and/or the second portion  1008  are contemplated by the present disclosure. 
     Referring now to  FIGS. 18 and 19 , a tissue thickness compensator assembly  1033 , which is similar in many respects to the tissue thickness compensator assembly  1000  and the tissue thickness compensator  20020 , is illustrated. The tissue thickness compensator assembly  1033  can comprise the first portion  1006  and the second portion  1008  which can be spaced apart and separably coupled together by a plurality of bridging members or connectors  1030  which may extend across the gap  1010  between the first portion  1006  and the second portion  1008 . In addition, some or all of the connectors  1030  of the tissue thickness compensator assembly  1033  can be partially embedded into the first portion  1006  and the second portion  1008 , as illustrated in  FIG. 19 . Furthermore, some or all of the connectors  1030  can comprise a first end positioned within the first portion  1006 , a second end positioned within the second portion  1008 , and a gap bridging portion  1032  therebetween. The gap bridging portion  1032  may extend across the gap  1010  between the first portion  1006  and the second portion  1008 , as illustrated in  FIG. 19 . The connectors  1030  can be spaced apart along the length of the gap  1010  to separably couple the first portion  1006  to the second portion  1008 . 
     In certain circumstances, the connectors  1030  can be evenly distributed along an axis extending along the gap  1010 , as illustrated in  FIG. 19 . In other circumstances, although not illustrated, the connectors  1030  can be unevenly distributed along the axis extending along the gap  1010 . The cutting portion  10053  can be configured to transect the gap bridging portions  1032  of the connectors  1030  as the cutting portion  10053  is advanced between the first portion  1006  and the second portion  1008  through the knife path defined by the gap  1010 . Where the connectors  1030  are unevenly distributed along the axis extending along the first portion  1006  and the second portion, in at least one instance, the connectors  1030  can be disposed in greater frequency and/or in closer proximity to each other at a distal segment of the gap  1010  than at a proximal segment of the gap  1010  such that the cutting portion  10053  may experience an increasing resistance as it is advanced along the knife path defined by the gap  1010 . In other circumstances, the connectors  1030  can be disposed in greater frequency and/or in closer proximity to each other at a proximal segment of the gap  1010  than at a distal segment of the gap  1010  such that the cutting portion  10053  may experience a decreasing resistance as it is advanced along the knife path defined by the gap  1010 , for example. 
     In certain circumstances, the connectors  1030  can extend or substantially extend in a single plane which can be parallel or substantially parallel to the first deck contacting portion  1007  and/or the second deck contacting portion  1009 , as illustrated in  FIG. 19 . In other circumstances, although not illustrated, the connectors  1030  can extend or substantially extend along a plurality of planes which can be parallel or substantially parallel to each other and/or to the first deck contacting portion  1007  and/or the second deck contacting portion  1009 . 
     Further to the above, some or all of the gap bridging portions  1032  of the connectors  1030  can be thinner than the remainder of their respective connectors  1030  to present the cutting portion  10053  with a reduced resistance as the cutting portion  10053  is advanced to transect the connectors  1030  while maintaining a coupling engagement with the first portion  1006  and the second portion  1008  of the second layer  1004 . For example, some or all the connectors  1030  can comprise a dog-bone shape with thicker ends terminating within the first portion  1006  and the second portion  1008  of the second layer  1004  and thinner central portions extending therebetween. In certain circumstances, the connectors  1030  can each be comprised of a piece of suture which may be comprised of bioabsorbable material such as polyglycolic acid (PGA) which is marketed under the trade name Vicryl, polylactic acid (PLA or PLLA), polydioxanone (PDS), polyhydroxyalkanoate (PHA), poliglecaprone 25 (PGCL) which is marketed under the trade name Monocryl, polycaprolactone (PCL), and/or a composite of PGA, PLA, PDS, PHA, PGCL and/or PCL, for example. 
     Referring again to  FIG. 18 , the tissue thickness compensator assembly  1033  can be prepared using a mold  1034 . An organic solution comprising a polymer such as, for example, polylactic acid (PLA) and/or polyglycolic acid (PGA) can be poured into the mold  1034 . The connectors  1030  can be immersed into the organic solution. As illustrated in  FIG. 18 , one or more of the connectors  1030  can each be trapped in one or more dedicated slots  1040  on a central shelf  1036  by one or more beams  1039  extending from a mold cover  1038  and configured for mating engagement with the slots  1040  when the mold cover  1038  is in a closed configuration with the mold  1034  to ensure that the connectors  1030  remain immersed in the organic solution. The slots  1040  can be sized to receive or at least partially receive the bridging portions  1032  which can be secured by the beams  1039  when the mold cover  1038  is in the closed configuration with the mold  1034 . The ends of the connectors  1030  extending from the gap bridging portions  1032  may freely float in the organic solution. Alternatively, the ends of the connectors  1030  can be secured to sides of the mold  1034 , for example. In certain circumstances, the connectors  1030  can be stretched in the organic solution between the sides of the mold  1034 . In other circumstances, the connectors  1030  can be loosely held between the sides of the mold  1034  to extend through the organic solution in a non-linear fashion, for example. 
     Further to the above, in various instances, the organic solution can then be lyophilized using conventional lyophilization techniques and/or any other suitable techniques. Upon completion of the lyophilization process, the mold cover  1036  can be removed and the tissue thickness compensator assembly  1033  can be recovered from the mold  1034 . As illustrated in  FIG. 19 , the resulting tissue thickness compensator assembly  1033  includes connectors  1030  partially positioned within the first portion  1006  and the second portion  1008 . Other techniques for partially embedding the connectors  1030  into the first portion  1006  and/or the second portion  1008  are contemplated by the present disclosure. The reader will appreciate that the connectors  1030  can be positioned closer to or further away from the deck contacting surfaces  1007  and  1009  by changing the height of the central shelf  1038  and/or depth of the slots  1040 . 
     Referring now to  FIG. 20 , a tissue thickness compensator assembly  1042 , which may be similar in many respects to the tissue thickness compensator assembly  1033 , the tissue thickness compensator assembly  1000 , and/or the tissue thickness compensator  20020 , is illustrated. The tissue thickness compensator assembly  1042  may comprise the first portion  1006  and the second portion  1008  which can be spaced apart and separably coupled together by a continuous flexible member  1044  which may form a plurality of bridging members or connectors  1046  which may extend across the gap  1010  between the first portion  1006  and the second portion  1008 . The continuous flexible member  1044  may include a first end  1048 , a second end  1050 , and a flexible portion  1052  extending between the first end  1048  and the second end  1050 . The flexible portion  1052  can be configured to extend through the first portion  1006  and the second portion  1008  several times, for example in a zigzag pattern, to form the connectors  1046 , as illustrated in  FIG. 20 . The flexible portion  1052  can be passed in a first direction through a distal segment  1054  of the first portion  1006  and a distal segment  1056  of the second portion  1008  to form a first gap bridging portion  1046   a  across the gap  1010 . The flexible portion  1052  can then be looped and passed in a second direction, opposite the first direction, through the second portion  1008  proximal to the distal segment  1056  and through the first portion  1006  proximal to the distal segment  1054  thereby forming a second gap bridging portion  1046   b  proximal the first gap bridging portion  1046   a . Additional gap bridging portions  1046   c  and  1046   d , for example, can be formed in the same manner across the gap  1010 , as illustrated in  FIG. 20 . 
     In certain circumstances, the continuous flexible member  1044  can comprise a suture and can be comprised of a suture material such as polyglycolic acid (PGA) which is marketed under the trade name Vicryl, polylactic acid (PLA or PLLA), polydioxanone (PDS), polyhydroxyalkanoate (PHA), poliglecaprone 25 (PGCL) which is marketed under the trade name Monocryl, polycaprolactone (PCL), and/or a composite of PGA, PLA, PDS, PHA, PGCL and/or PCL, for example. In certain circumstances, the tissue thickness compensator assembly  1042  can be assembled after the first portion  1006  and the second portion  1008  are manufactured, for example, via lyophilization. In some circumstances, a needle (not shown) can be attached to the first end  1048  of the continuous flexible member  1044  and can be passed through the first portion  1006  and the second portion  1008 , for example in a zigzag pattern, to couple the first portion  1006  to the second portion  1008 , as described above. The first end  1048  and/or the second end  1050  of the continuous flexible member  1044  can be secured to the side walls of the first portion  1006  and/or the second portion  1008  by tying in one or more knots at the first end  1048  and/or the second end  1050 , for example. The knots may abut against the side walls of the first portion  1006  and/or the second portion  1008  to prevent the flexible portion  1052  from unraveling relative to the first portion  1006  and/or the second portion  1008 . In other circumstances, the first portion  1006  and the second portion  1008  of the tissue thickness compensator assembly  1042  can be formed around the continuous flexible member  1044 . In such circumstances, as illustrated in  FIG. 20 , the continuous flexible member  1044  can be disposed in a mold  1062 , for example in a zigzag pattern, with slots  1064  defined side walls  1066  and slots  1068  defined in central shelf  1070 . An organic solution comprising a polymer such as, for example, polylactic acid (PLA) and/or polyglycolic acid (PGA) can be poured into the mold  1062  until the continuous flexible member  1044  is immersed in the organic solution. A mold cover  1072  can be used to ensure that the continuous flexible member  1044  remains immersed in the organic solution which can then be lyophilized using conventional lyophilization techniques and/or any other suitable techniques. The first end  1048  and the second end  1050  of the continuous flexible member  1044  can be secured at openings  1053  and  1055  of the mold  1062 , respectively, by tying in one or more knots at the first end  1048  and the second end  1050  after passing the first end  1048  through the opening  1053  and the second end  1050  through the opening  1055 , for example. The knots may abut against the side walls of the mold  1062  to prevent the continuous flexible member  1044  from unraveling relative to the mold  1066 . After the tissue thickness compensator has been removed from the mold, in various instances, portions of the continuous flexible member  1044 , such as portions  1048 ,  1050 , and/or  1052 , for example, can then be cut and removed from the tissue thickness compensator. Other techniques for assembling the tissue thickness compensator assembly  1042  are contemplated by the present disclosure. 
     In certain circumstances, a tissue thickness compensator assembly such as, for example, the tissue thickness compensator assembly  1042  can be compromised when excessive force or pressure is applied thereto. For instance, pressure can be applied to a tissue thickness compensator assembly such as, for example, the tissue thickness compensator assembly  1042  when the tissue thickness compensator assembly  1042  is loaded onto a staple cartridge such as, for example, the staple cartridge  10000 . The tissue thickness compensator assembly  1042  can be equipped with a pressure or force sensitive member that can provide a user with a warning feedback if the pressure experienced by the tissue thickness compensator assembly exceeds a threshold. For example, a pressure or force sensitive film can be attached to the tissue thickness compensator assembly  1042  and can be configured to change color upon experiencing pressure that exceeds the threshold. In certain circumstances, the pressure or force sensitive film can be disposed over the first portion  1006  and/or the second portion  1008  and can be attached thereto via an adhesive, for example. The pressure or force sensitive film can be biocompatible to permit implantation of the pressure or force sensitive film with the tissue thickness compensator assembly  1042  inside a patient. 
     Referring now to  FIGS. 23-25 , a surgical end effector  1100  is illustrated. The end effector  1100  is similar in many respects to various end effectors disclosed elsewhere herein such as, for example, the end effector  22090  ( FIG. 9 ). As illustrated in  FIG. 23 , the end effector  1100  can include a staple cartridge assembly  1102  which is similar in many respects to the staple cartridge assembly  20200  ( FIG. 6 ), for example. In addition, the end effector  1100  may include a tissue thickness compensator  1104  which is similar in many respects to other tissue thickness compensators disclose elsewhere in this document such as the tissue thickness compensator  22020  ( FIG. 9 ), the tissue thickness compensator  20220  ( FIG. 6 ), and/or the tissue thickness compensator  10020  ( FIG. 4 ), for example. 
     Further to the above, end effector  1100  can include a tissue thickness compensator  1104  wherein the tissue thickness compensator  1104  can be prepared using conventional lyophilization techniques and/or any other suitable techniques. In at least one example, the tissue thickness compensator  1104  can be prepared by dissolving a polymer such as, for example, polylactic acid (PLA) and/or polyglycolic acid (PGA) in an organic solvent and lyophilizing the solution. The tissue thickness compensator  1104  can be comprised of a biocompatible foam which may comprise a porous, open cell foam and/or a porous, closed cell foam, for example. 
     Further to the above, the tissue thickness compensator  1104  can be altered or modified for use in a surgical procedure. For example, upon completion of the lyophilization process, the tissue thickness compensator  1104  can be contacted with a modifying member  1106  to modify the tissue thickness compensator  1104  for use in a particular surgical procedure. In certain circumstances, the modification can occur after assembling the tissue thickness compensator  1104  with the end effector  1100 , as illustrated in  FIGS. 23-35 . For example, as illustrated in  FIG. 23 , the tissue thickness compensator  1104  can be releasably assembled to the cartridge assembly  1102  and modified while assembled with the cartridge assembly  1102 . In other circumstances, the modification can occur before assembling the tissue thickness compensator  1104  with the end effector  1100 . In at least one example, the modification can be performed as a separate step during manufacturing. In yet another example, the modification may be performed during a surgical procedure. 
     As described in greater detail below, the modification process can involve modifying a surface or a plurality of surfaces of the tissue thickness compensator  1104 . In certain circumstances, the modification process can involve modifying one or more portions of the tissue thickness compensator  1104 . One or more portions can be modified in a single modification process. Alternatively, a plurality of portions can each be modified separately in consecutive modification processes. In certain circumstances, the modification process can comprise a thermal pressing process which can be used to change the shape, size, dimensions, and/or porosity of at least a portion of the tissue thickness compensator  1104 . Furthermore, the modification process can include means for creating space within one or more portions of the tissue thickness compensator  1104 . 
     Referring again to  FIGS. 23-25 , in certain circumstances, a portion  1107  ( FIG. 23 ) of the tissue thickness compensator  1104  can be modified by a thermal pressing process which may include transitioning the portion  1107  to a glassy state, engaging the portion  1107  with the modifying member  1106 , applying pressure onto the portion  1107  while it is in the glassy state, and allowing the portion  1107  to cool below the glassy state while the modifying member  1106  is still engaged with the portion  1107 . The modifying member  1106  may be used to maintain the pressure on the portion  1107  for a time period sufficient to create the resulting modified portion  1108  ( FIG. 25 ). It is note worthy that a material&#39;s transition into a glassy state can be a reversible transition from a relatively hard state to a relatively molten or flexible state in response to an increase in the temperature of the material to a glass transition temperature. A glass transition temperature of the material can be a particular temperature or, in some instances, a range of temperatures. The tissue thickness compensator modification process described herein takes advantage of this phenomenon by modifying a tissue thickness compensator while the tissue thickness compensator is in the glassy flexible state and then allowing the tissue thickness compensator to cool below the glass transition temperature while maintaining the modification. 
     Further to the above, referring again to  FIGS. 23-25 , the portion  1107  of the tissue thickness compensator  1004  can be transitioned into the glassy state by heating at least the portion  1107  to a temperature greater than or equal to a glass transition temperature of the material from which the portion  1107  is composed but lower than the melting temperature of the same. For example, the tissue thickness compensator  1104  can be comprised of polyglycolic acid (PGA) and in such circumstances, the portion  1107  can be transitioned into the glassy state by heating the portion  1107  to a temperature that is greater than or equal to the glass transition temperature of polyglycolic acid (PGA) but lower than the melting temperature of the same. In various instances, the glass transition temperature of polyglycolic acid (PGA) can be in the range of 35-40° C., for example, and its melting temperature can be in the range of 225-230° C., for example. In at least one example, the portion  1107  of the tissue thickness compensator  1104  can be heated to a temperature that is greater than or equal to 35° C. but lower than 225° C. in order to transition the portion  1107  to the glassy state. In another example, the portion  1107  can be transitioned to the glassy state by heating the portion  1107  to a temperature that is greater than or equal to 40° C. but lower than 200° C., for example. 
     Further to the above, the modifying member  1106  can then be used to apply pressure onto the portion  1107  while the portion  1107  is in the glassy state. The portion  1107  can be allowed to exit the glassy state by cooling the portion  1107  to a temperature below 35° C., for example. The pressure may be maintained for a time period sufficient to permit the tissue thickness compensator  1104  to retain, or at least partially retain, the modification imposed by the modifying member  1106 . 
     In certain examples, the pressure can be maintained for a period of time from about 30 seconds to about 8 hours, for example, during the time in the glassy state and/or for a period of time from about 30 seconds to about 8 hours, for example, after exiting the glassy state. In at least one example, the pressure can be maintained for approximately 10 minutes during the time in the glassy state and for approximately 10 minutes after exiting the glassy state. Other time periods for maintaining the pressure are contemplated by the present disclosure. 
     In certain circumstances, the modifying member  1106  can be used to apply pressure onto the portion  1107  before the portion  1107  is transitioned to the glassy state. In certain circumstances, the modifying member  1106  may apply pressure to the portion  1107  while the portion  1107  is heated to reach the glassy state, while the portion  1107  is in the glassy state, and/or while the portion  1107  is transitioned or cooled to a temperature below the glassy state. In certain circumstances, the pressure applied to the portion  1107  can be gradually increased toward a threshold as the temperature of the portion  1107  is gradually increased to transition the portion  1107  toward the glassy state, for example. In certain circumstances, the pressure applied to the portion  1107  can be removed, gradually removed, or at least partially reduced as the portion  1107  exits the glassy state, before the portion  1107  exits the glassy state, and/or after the portion  1107  exits the glassy state. 
     In certain circumstances, the modifying member  1106  can also be a heat source for transitioning the portion  1107  of the tissue thickness compensator  1104  to the glassy state. For example, the modifying member  1106  can comprise a cylindrical distal portion  1110 , as illustrated in  FIG. 24 , which may include a heating coil (not shown). A user can may energize the heating coil and engage the portion  1107  of the tissue thickness compensator  1104  with the modifying member  1106  to heat the portion  1107  to a temperature that is greater than or equal the glass transition temperature of the material composition of the portion  1107 . Upon reaching a desired temperature, the modifying member may be pressed against the portion  1107 , as illustrated in  FIG. 24 . Alternatively, the modifying member may be pressed against the portion  1107  before the modifying member  1106  reaches the desired temperature. As described above, the pressure may be maintained for a time period sufficient to permit the tissue thickness compensator  1104  to retain, or at least partially retain, the modification imposed by the modifying member  1106 . In addition, the heating coil of the modifying member  1106  can be turned off to allow the temperature of the portion  1107  to cool below the glass transition temperature. The modifying member can then be removed. In certain circumstances, the pressure applied by the modifying member  1106  can be initiated prior to the portion  1107  entering the glassy state and maintained throughout the glassy state. In some circumstances, the pressure applied by the modifying member  1106  can be removed while the portion  1107  is in the glassy state. 
     As illustrated in  FIGS. 23-25 , the modifying member  1106  can be configured to change the shape, size, dimensions, density, spring rate, and/or porosity of the portion  1107  of the tissue thickness compensator  1104 . For example, the modified portion  1108  may comprise a substantially concave top surface  1114  with a reduced height H 1 , while the remainder of the tissue thickness compensator  1104  may retain a substantially flat top surface including an original height H which is greater than the reduced height H 1 , as illustrated in  FIG. 25 . As described above, the modifying member  1106  may comprise a cylindrical distal portion  1110 . In such circumstances, the curvature of the resulting concave surface  1114  can, in part, depend on the curvature of the cylindrical distal portion  1110  of the modifying member  1106  in contact with the portion  1107  of the tissue thickness compensator  1104  during the modification process. Furthermore, the modified portion  1108  may possess a new lower porosity compared to the unmodified portion  1107  which can result, at least in part, from the compressive forces applied to the portion  1107  by the modifying member  1106  during the modification process, as described above. Said another way, the pressure applied to the portion  1107  during the modification process may yield a material redistribution wherein a cross-section through the modified portion  1108  may comprise a greater material density than a similar cross section through the portion  1107  prior to the modification process. Furthermore, the modified portion  1108  may comprise a different spring rate from the remainder of the tissue thickness compensator  1104  which can result, in part, from the changes in density and porosity realized by the modified portion  1108  during the modification process, as described in greater detail below. In at least one instance, the spring rate of the modified portion  1108  may be less than or greater than the spring rate of the unmodified portion  1107 . 
     Referring now to  FIGS. 26-34 , a tissue thickness compensator can be modified prior to assembly with an end effector such as, for example, the end effector  22090  ( FIG. 9 ). In certain circumstances, as illustrated in  FIGS. 27, 30 , and  33 , a mold can be utilized to modify a tissue thickness compensator using a thermal pressing process, as described above. For example, as illustrated in  FIGS. 26-28 , a tissue thickness compensator  1120  can be modified to include a longitudinal slot  1122 . The tissue thickness compensator  1120  may be similar in many respects to other tissue thickness compensators described elsewhere such as, for example, the tissue thickness compensator  22020  ( FIG. 9 ). For example, like the compensator  22020 , the compensator  1120  can be utilized with the end effector  22090 . Furthermore, the longitudinal slot  1122  may be similar in many respects to the knife slot  22025 . For example, like the knife slot  22025 , the slot  1122  may define a tissue thickness compensator knife path for the cutting portion  10053  between a first stapling portion  1124   a  and a second stapling portion  1124   b . Furthermore, the first stapling portion  1124   a  and the second stapling portion  1124   b  can be similar in many respects to the first stapling portion  22021   a  ( FIG. 9 ) and the second stapling portion  22021   b  ( FIG. 9 ), respectively, of the tissue thickness compensator  22020 . In addition, the slot  1122  can be configured to releasably connect the first stapling portion  1124   a  and the second stapling portion  1124   b  such that, in use with the end effector  22090 , the cutting portion  10053  can be advanced distally through the slot  1122  to transect the slot  1122  and separate the first stapling portion  1124   a  and the second stapling portion  1124   b.    
     Referring again to  FIGS. 26-28 , the tissue thickness compensator  1120  can be prepared using traditional lyophilization techniques and/or any other suitable techniques. In addition, the tissue thickness compensator  1120  can be modified or altered to create the slot  1122  therethrough Similar to the tissue thickness compensator  1104 , the tissue thickness compensator  1120  can be comprised at least in part of a material comprising a glass transition temperature and can modified by transitioning the material into a glassy state. In one example, the tissue thickness compensator  1120  can be heated in an oven (not shown) to a temperature greater than or equal to the glass transition temperature of the material composition of the tissue thickness compensator  1120  but less than the melting temperature of the same. A mold  1126  comprising a central beam  1128 , as illustrated in  FIG. 27 , can be utilized to create the slot  1122  by inserting the central beam  1128  into the tissue thickness compensator  1120  while the tissue thickness compensator  1120  is in the glassy state. The tissue thickness compensator  1120  can then be allowed to cool to a temperature below the glass transition temperature while the central beam  1128  remains inserted into the tissue thickness compensator  1120 . In some instances, the central beam  1128  can be removed from the tissue thickness compensator  1120  while the tissue thickness compensator  1120  is in its glassy state. 
     In certain circumstances, a cooling medium can be utilized to actively cool the tissue thickness compensator  1120 . In some instances, a fan can be used to generate a flow of air over the tissue thickness compensator  1120  while the tissue thickness compensator  1120  is in the mold  1126  and/or after the tissue thickness compensator  1120  has been removed from the mold. In some instances, a refrigeration process can be utilized to cool the tissue thickness compensator  1120  while the tissue thickness compensator  1120  is in the mold  1126  and/or after the tissue thickness compensator  1120  has been removed from the mold. The central beam  1128  can be removed after transitioning the tissue thickness compensator  1120  out of the glassy state. The central beam  1128  can remain inserted into the tissue thickness compensator  1120  for a time period sufficient to permit the tissue thickness compensator  1120  to retain, or at least substantially retain, the space occupied by the central beam  1128 . In certain examples, the central beam  1128  can remain inserted for a period of time from about 30 seconds to about 8 hours, for example, during the time in the glassy state and/or for a period of time from about 30 seconds to about 8 hours, for example, after exiting the glassy state. In at least one example, the central beam  1128  can remain inserted for approximately 10 minutes during the time in the glassy state and for approximately 10 minutes after exiting the glassy state. Other time periods for maintaining the central beam  1128  within the tissue thickness compensator  1120  are contemplated by the present disclosure. 
     Further to the above, as illustrated in  FIG. 28 , pressure applied by the central beam  1128  during the modification process may yield an increased material density at a portion  1130  of the tissue thickness compensator  1120 . The portion  1130  may connect the first stapling portion  1124   a  and a second stapling portion  1124   b  thereby providing additional stability for the slot  1122 . In certain circumstances, the mold  1126  may comprise edge modifiers such as, for example, edge modifiers  1132   a  and  1132   b  which can modify the tissue thickness compensator  1120  during the modification process to produce modified edges  1134   a  and  1134   b , respectively, as illustrated in  FIG. 28 . 
     Referring again to  FIGS. 26-28 , it may be desirable to remove a significant amount of material from the tissue thickness compensator  1120  to create the slot  1122 . In such circumstances, the central beam  1128  can be heated to a temperature greater than the melting temperature of the material composition of the tissue thickness compensator  1120 . Upon inserting the heated central beam  1128  into the tissue thickness compensator  1120 , the central beam  1128  may melt through the tissue thickness compensator  1120  thereby creating a space for the slot  1122  within the tissue thickness compensator  1120 , as illustrated in  FIG. 28 . In certain circumstances, it may be desirable to gradually increase the pressure applied by the central beam  1128  against the tissue thickness compensator  1120  to gradually insert the central beam  1128  into the tissue thickness compensator  1120 . 
     In certain circumstances, it can be desirable to increase material density of one or more surfaces of a tissue thickness compensator. As illustrated in  FIGS. 29-31 , a tissue thickness compensator  1140  can be modified or altered such that a surface  1142  of the tissue thickness compensator  1140  may comprise a higher material density than the remainder of the tissue thickness compensator  1140 , which can be achieved, in certain circumstances, post lyophilization. The tissue thickness compensator  1140  may be similar in many respects to other tissue thickness compensators described elsewhere such as, for example, the tissue thickness compensator  22020  ( FIG. 9 ) and/or the tissue thickness compensator  1120  ( FIG. 26 ). A surface modifier  1144  can be utilized to modify the surface  1142  of the tissue thickness compensator  1140  using a thermal pressing process which is similar in many respects to the thermal pressing processes used to modify the tissue thickness compensator  1104  and/or the tissue thickness compensator  1120 , as described above. For example, the tissue thickness compensator  1140  can be comprised at least in part of a material comprising a glass transition temperature and can be modified after being transitioned into a glassy state. 
     As described above, a tissue thickness compensator such as, for example, the tissue thickness compensator  1140  can be transitioned to the glassy state where it is heated to a temperature greater than or equal to the glass transition temperature of the material composition of the tissue thickness compensator  1140  but less than the melting temperature of the same. The surface modifier  1144  can be pressed against the surface  1142  while the tissue thickness compensator  1140  is in the glassy state. The pressure applied by the surface modifier  1144  may compress the surface  1142  thereby increasing the material density of the surface  1142 . The increase in material density can be retained by the surface  1142  by allowing the surface  1142  to cool to a temperature below the glass transition temperature. 
     In certain instances, the pressure applied by the surface modifier  1144  against the surface  1142  can be maintained for a period of time from about 30 seconds to about 8 hours, for example, during the time in the glassy state and/or for a period of time from about 30 seconds to about 8 hours, for example, after exiting the glassy state. In at least one example, the pressure can be maintained for approximately 10 minutes during the time in the glassy state and for approximately 10 minutes after exiting the glassy state. Other time periods for maintaining the pressure applied by the surface modifier  1144  against the surface  1142  are contemplated by the present disclosure. 
     In some instances, a fan can be used to generate a flow of air over the tissue thickness compensator  1140  while the tissue thickness compensator  1140  is in contact with the modifier  1144  and/or after the tissue thickness compensator  1140  has been removed from the modifier  1144 . In some instances, a refrigeration process can be utilized to cool the tissue thickness compensator  1140  while the tissue thickness compensator  1140  is in contact with the modifier  1144  and/or after the tissue thickness compensator  1140  has been removed from the modifier  1144 . Upon transitioning the tissue thickness compensator  1140  out of the glassy state, in various instances, the surface modifier  1144  can be disengaged from the tissue thickness compensator  1140 . In certain circumstances, the surface modifier  1144  can include a heating element which can be utilized to increase the temperature of the surface  1142  to a temperature greater than or equal to the glass transition temperature of the material composition of the tissue thickness compensator  1140 , as described above. 
     Referring again to  FIG. 30 , the surface modifier  1144  may comprise a flat, or at least substantially flat, contacting surface  1146  for contacting the surface  1142 , for example. In other circumstances, the contacting surface  1146  may comprise various textures such as, for example, protrusions which can extend into the surface  1142  of the tissue thickness compensator  1140  during the modification process. In certain circumstances, the surface modifier  1144  can be used to apply pressure onto the surface  1142  of the tissue thickness compensator  1140  before the tissue thickness compensator  1140  is transitioned to the glassy state. In certain circumstances, the surface modifier  1144  may apply pressure to the surface  1142  while the tissue thickness compensator  1140  is heated to reach the glassy state, while the tissue thickness compensator  1140  is in the glassy state, and/or while the tissue thickness compensator  1140  is transitioned or cooled to a temperature below the glassy state. In certain circumstances, the pressure applied by the surface modifier  1144  to the surface  1142  can be gradually increased toward a threshold as the temperature of the tissue thickness compensator  1140  is gradually increased to transition the tissue thickness compensator  1140  toward the glassy state, for example. In certain circumstances, the pressure applied to the surface  1142  can be removed, gradually removed, or at least partially reduced as the tissue thickness compensator  1140  exits the glassy state, before the tissue thickness compensator  1140  exits the glassy state, and/or after the tissue thickness compensator  1140  exits the glassy state. 
     In certain circumstances, the tissue thickness compensator  1140  can be modified or altered to include a skin or a dense outer layer. In certain circumstances, the resulting skin or dense outer layer may comprise textures such as, for example, protrusions which can extend into the surface  1142  of the tissue thickness compensator  1140 . In certain instances, the contacting surface  1146  of the surface modifier  1144  can be heated to a temperature greater than or equal to the melting temperature of the material composition of the tissue thickness compensator  1140 . The surface modifier  1144  and/or the tissue thickness compensator  1140  can be moved to bring the surface  1142  of the tissue thickness compensator  1140  into contact with the heated contacting surface  1146  of the surface modifier  1144  thereby melting, or at least substantially melting, the surface  1142 . The surface modifier  1144  and the tissue thickness compensator  1140  can then be separated to permit the modified surface  1142  to cool below its melting temperature which may create a skin or a dense outer layer onto the tissue thickness compensator  1140 . 
     In certain instances, the contacting surface  1146  of the surface modifier  1144  can be heated prior to coming in contact with the surface  1142 . In other instances, the contacting surface  1146  of the surface modifier  1144  can be heated after coming in contact with the surface  1142 . 
     In certain instances, the contacting surface  1146  of the surface modifier  1144  can remain in contact with the surface  1142  of the tissue thickness compensator  1140  for a time period sufficient to allow the surface  1142  to flow into a desired geometry. Such a time period can range from about 30 seconds to about 8 hours, for example; other time periods are contemplated by the present disclosure. Such a time period can be sufficient to locally affect and/or melt the material of the tissue thickness compensator  1140  and have it flow into a new geometry. As described herein, such a new geometry can be prescribed by the tooling used to make the tissue thickness compensator  1140 . 
     In certain instances, the surface  1142  of the tissue thickness compensator  1140  can be allowed to cool, or can be actively cooled, to a temperature below the melting temperature of the tissue thickness compensator  1140  before separating the surface modifier  1144  from the tissue thickness compensator  1140 . In other instances, the surface  1142  of the tissue thickness compensator  1140  can be allowed to cool, or can be actively cooled, to a temperature below the melting temperature of the tissue thickness compensator  1140  after separating the surface modifier  1144  from the tissue thickness compensator  1140 . 
     Further to the above, the modified surface  1142  can comprise a density which is approximately 10% greater than the density of the remainder of the tissue thickness compensator  1140 , approximately 20% greater than the density of the remainder of the tissue thickness compensator  1140 , approximately 30% greater than the density of the remainder of the tissue thickness compensator  1140 , approximately 40% greater than the density of the remainder of the tissue thickness compensator  1140 , approximately 50% greater than the density of the remainder of the tissue thickness compensator  1140 , approximately 60% greater than the density of the remainder of the tissue thickness compensator  1140 , approximately 70% greater than the density of the remainder of the tissue thickness compensator  1140 , approximately 80% greater than the density of the remainder of the tissue thickness compensator  1140 , approximately 90% greater than the density of the remainder of the tissue thickness compensator  1140 , and/or approximately 100% greater than the density of the remainder of the tissue thickness compensator  1140 , for example. In various circumstances, the modified surface  1142  can comprise a density which is more than the density of the remainder of the tissue thickness compensator  1140  and less than twice the density of the remainder of the tissue thickness compensator  1140 , for example. In various circumstances, the modified surface  1142  can comprise a density which is over twice the density of the remainder of the tissue thickness compensator  1140 , for example. 
     Referring now to  FIGS. 32-34 , a tissue thickness compensator  1150  can be modified to include a plurality of apertures  1152  which may extend at least partially through the tissue thickness compensator  1150 . The tissue thickness compensator  1150  may be similar in many respects to other tissue thickness compensators described herein such as, for example, the tissue thickness compensator  20220  ( FIG. 6 ). Like the compensator  20220 , the compensator  1150  can be utilized with the cartridge assembly  20200  ( FIG. 6 ) and the apertures  1152  may be similar in many respects to the clearance apertures  20224  extending at least partially through the tissue thickness compensator  20220 . For example, like the apertures  20224 , the apertures  1152  can be aligned with corresponding staple legs  20232  ( FIG. 7 ) when the tissue thickness compensator  1150  is assembled with the cartridge assembly  20200  such that the staple legs  20232  may move through the clearance apertures  1152  in the tissue thickness compensator  1150  when the staple legs  20232  move from the unfired configuration to the fired configuration, as described above in greater detail. 
     Further to the above, referring again to  FIGS. 32-34 , the tissue thickness compensator  1150  can be prepared using traditional lyophilization techniques and/or any other suitable techniques. In certain circumstances, a polymer having a glass transition temperature such as, for example, polylactic acid (PLA) and/or polyglycolic acid (PGA) can be dissolved in an organic solvent to form a solution which can be lyophilized to produce the tissue thickness compensator  1150 . Furthermore, the tissue thickness compensator  1150  can be modified post lyophilization using a thermal pressing process which is similar in many respects to the thermal pressing processes used to modify the tissue thickness compensator  1104 , the tissue thickness compensator  1120 , and/or the tissue thickness compensator  1140 , for example, as described above. For example, the tissue thickness compensator  1150  can be modified to include the apertures  1152  once the tissue thickness compensator  1150  is transitioned to a glassy state. 
     As described above, a tissue thickness compensator such as, for example, the tissue thickness compensator  1150  can be transitioned to a glassy state by being heated in an oven (not shown) to a temperature greater than or equal to the glass transition temperature of the material composition of the tissue thickness compensator  1150  but less than the melting temperature of the same. A mold  1154  comprising a plurality of posts, dowels, pins, and/or protrusions, for example, such as, for example, needles  1156  can be utilized to create the apertures  1152  by inserting the needles  1156  into the tissue thickness compensator  1150  while the tissue thickness compensator  1150  is in the glassy state. The tissue thickness compensator  1150  can then be allowed to cool to a temperature below the glass transition temperature while the needles  1156  remain inserted into the tissue thickness compensator  1150 . In some instances, the needles  1156  can be removed from the tissue thickness compensator  1150  while the tissue thickness compensator  1150  is in the glassy state. In some instances, a fan can be used to generate a flow of air over the tissue thickness compensator  1150  while the tissue thickness compensator  1150  is engaged with the needles  1156  and/or after the tissue thickness compensator  1150  has been disengaged from the needles  1156 . In some instances, a refrigeration process can be utilized to cool the tissue thickness compensator  1150  while the tissue thickness compensator  1150  is engaged with the needles  1156  and/or after the tissue thickness compensator  1150  has been disengaged from the needles  1156 . In various instances, the needles  1156  can be removed after transitioning the tissue thickness compensator  1150  out of the glassy state. The needles  1156  can remain inserted into the tissue thickness compensator  1150  for a time period sufficient to permit the tissue thickness compensator  1150  to retain, or at least substantially retain, the spaces defining the apertures  1152  which are occupied by the needles  1156 . 
     In certain examples, the needles  1156  can remain inserted for a period of time from about 30 seconds to about 8 hours, for example, during the time in the glassy state and/or for a period of time from about 30 seconds to about 8 hours, for example, after exiting the glassy state. In at least one example, the needles  1156  can remain inserted for approximately 10 minutes during the time in the glassy state and for approximately 10 minutes after exiting the glassy state. Other time periods for maintaining the needles  1156  inserted into the tissue thickness compensator  1150  are contemplated by the present disclosure. 
     In certain circumstances, the needles  1156  can be removed from the tissue thickness compensator  1150  prior to transitioning the tissue thickness compensator  1150  out of the glassy state. In other circumstances, the needles  1156  can be gradually removed over time. For example, the needles  1156  can be partially removed from the tissue thickness compensator  1150  prior to transitioning the tissue thickness compensator  1150  out of the glassy state. The needles  1156  can then be fully removed from the tissue thickness compensator  1150  after transitioning the tissue thickness compensator  1150  out of the glassy state. The reader will appreciate that the greater the depth of insertion of the needles  1156  into the tissue thickness compensator  1150 , the greater the depth of the corresponding apertures  1152  that can be created in the tissue thickness compensator  1150 . 
     Referring again to  FIGS. 32-34 , in certain instances, the needles  1156  can be heated to a temperature greater than or equal to the melting temperature of the material composition of the tissue thickness compensator  1150 . In addition, the needles  1156  can be inserted into the tissue thickness compensator  1150  to create the apertures  1152  by melting, or at least partially melting, through the regions of the tissue thickness compensator  1150  that receive the needles  1156 . In various instances, the needles  1156  can be heated prior to their insertion into the tissue thickness compensator  1150 . In various instances, the needles  1156  can be heated after their insertion into the tissue thickness compensator  1150 . In various instances, the needles  1156  can be gradually heated as the needles  1156  are inserted into the tissue thickness compensator  1150 . 
     In certain instances, the needles  1156  may remain positioned within the tissue thickness compensator  1150  for a period of time sufficient to permit the melted material of the tissue thickness compensator  1150  to flow into a desired geometry. Such a time period can range from about 30 seconds to about 8 hours, for example; other time periods are contemplated by the present disclosure. Such a time period can be sufficient to locally affect and/or melt the material of the tissue thickness compensator  1150  and have it flow into a new geometry. As described herein, such a new geometry can be prescribed by the tooling used to make the tissue thickness compensator  1150 . 
     In certain instances, the tissue thickness compensator  1150  can be allowed to cool, or can be actively cooled, to a temperature below the melting temperature of the tissue thickness compensator  1150  before separating the needles  1156  from the tissue thickness compensator  1150 . In other instances, the tissue thickness compensator  1150  can be allowed to cool, or can be actively cooled, to a temperature below the melting temperature of the tissue thickness compensator  1150  after separating the needles  1156  from the tissue thickness compensator  1150 . 
     Referring again to  FIGS. 32-34 , the needles  1156  can be arranged in rows extending longitudinally along a length of the mold  1154  which may correspond to staple rows in a staple cartridge such as, for example, the staple cartridge assembly  20200  ( FIG. 6 ). For example, as illustrated in  FIG. 33 , the needles  1156  can are arranged in six rows which can be configured to create six rows of the apertures  1152  that can be configured to receive six rows of the staples  20230  ( FIG. 7 ). In certain circumstances, as illustrated in  FIG. 33 , the rows of the needles  1156  can be arranged in two groups which are spaced apart and configured to be received in two portions  1158  and  1160  of the tissue thickness compensator  1150  thereby creating two groups of the apertures  1152  separated by an intermediate portion  1162 . The intermediate portion  1162  can be positioned, at least partially, over the cartridge knife slot  22015  ( FIG. 6 ), when the tissue thickness compensator  1150  is assembled with staple cartridge assembly  20200 . In use, the firing member  10052  ( FIG. 10 ) can be advanced distally to push the staple legs  20232  ( FIG. 8 ) through the apertures  1152  within the portions  1158  and  1160  and advance the cutting portion  10053  ( FIG. 10 ) to transect the intermediate portion  1162  and separate the portions  1158  and  1160 . 
     Referring again to  FIGS. 32-34 , the apertures  1152  can be configured to extend within the tissue thickness compensator  1150  and terminate at a certain depth within the tissue thickness compensator  1150 . The apertures  1152  may comprise uniform depths, as illustrated in  FIG. 34 . In other circumstances, the apertures  1152  may comprise different depths (not shown). For example, a first row of the apertures  1152  may comprise a first depth and a second row of the apertures  1152  may comprise a second depth different from the first depth and yet a third row of the apertures  1152  may comprise a third depth different from the first depth and the second depth. The depths of the apertures  1152  can be determined, at least in part, by the heights of the corresponding needles  1156 . For example, a first row of the needles  1156  comprising a first height and a second row of the needles  1156  comprising second height greater than first height may create a first row of the apertures  1152  comprising a first depth and a second row of the apertures  1152  comprising a second depth which is greater than the first depth. 
     Referring again to  FIGS. 32-34 , the needles  1156  can be configured to define a trajectory for the apertures  1152  within the tissue thickness compensator  1150 . In certain circumstances, the needles  1156  can extend along an axis that is perpendicular and/or substantially perpendicular to a mold surface  1164  of the mold  1154 , as illustrated in  FIG. 33 . Inserting the needles  1156  into the tissue thickness compensator  1150  while maintaining a parallel relationship between the mold surface  1164  and a surface  1166  of the tissue thickness compensator  1150  may result in defining a perpendicular and/or substantially perpendicular trajectory for the apertures  1152  relative to the surface  1166  of the tissue thickness compensator  1150 , as illustrated in  FIG. 34 . In other circumstances, the needles  1156  can extend from the mold surface  1164  at an oblique angle (not shown) and/or the insertion trajectory of the needles  1156  into the tissue thickness compensator  1150  can be at an angle such that the needles  1156  may define a non-perpendicular trajectory for the apertures  1152  relative to the surface  1166  of the tissue thickness compensator  1150 . In certain circumstances, a group of the needles  1156  can be parallel and/or substantially parallel to each other, as illustrated in  FIG. 33 , resulting in a group of the apertures  1152  that may be parallel and/or substantially parallel to each other, as illustrated in  FIG. 24 . In other circumstances, although not illustrated, a group of non-parallel needles can extend from the mold surface  1164  and may result in non-parallel apertures when inserted into the tissue thickness compensator  1150 . In some circumstances, the needles  1156  can be configured to create apertures within the tissue thickness compensator  1150  that can comprise a partially curved trajectory and/or a partially linear trajectory. For example, the needles  1156  can extend from the mold surface  1164  in a partially curved trajectory and can be inserted into the tissue thickness compensator  1150  to create apertures within the tissue thickness compensator  1150  with a corresponding partially curved trajectory. 
     Referring again to  FIGS. 32-34 , some or all of the needles  1156  can comprise blunt distal ends  1168 , as illustrated in  FIG. 33 . In other circumstances, some or all of the needles  1156  can comprise sharp distal ends (not shown). Some or all of the needles  1156  can comprise cylindrical, or at least substantially cylindrical, shapes, for example, as illustrated in  FIG. 33 . Other shapes are also contemplated by the present disclosure. 
     In various instances, one or more of the needles  1156  extending from the mold surface  1164  may not be insertable through the full thickness of the tissue thickness compensator  1150 . In certain instances, one or more of the needles  1156  extending from the mold surface  1164  can be insertable through the full thickness of the tissue thickness compensator  1150  to create openings an/or holes that extend through the full thickness of the tissue thickness compensator  1150 . In certain instances, one or more of the needles  1156  extending from the mold surface  1164  can be inserted through a first side of the tissue thickness compensator  1150  and exited through a second side of the tissue thickness compensator  1150  which may be opposite the first side, for example. In certain instances, one or more of the needles  1156  may comprise a length greater than the full thickness of the tissue thickness compensator  1150  to facilitate the insertion of the one or more needles  1156  through the full thickness of the tissue thickness compensator  1150 . 
     Referring now to  FIGS. 35-37 , it may be desirable to resize a tissue thickness compensator. For example, one or more dimensions of a tissue thickness compensator may be adjusted to correspond to dimensions of a staple cartridge in order to provide a better fit to the staple cartridge when the tissue thickness compensator is assembled with the staple cartridge. In certain circumstances, a tissue thickness compensator  1170  can be resized by changing its height from a first height H 1 , as illustrated in  FIG. 35 , to a second height H 2 , as illustrated in  FIG. 36 . The tissue thickness compensator  1170  may be similar in many respects to other tissue thickness compensators described herein such as, for example, the tissue thickness compensator  22020  ( FIG. 9 ), the tissue thickness compensator  1140  ( FIG. 29 ), and/or the tissue thickness compensator  1150  ( FIG. 32 ). For example, like the compensator  22020 , the compensator  1170  can be utilized with the end effector  22090  ( FIG. 9 ). 
     In various instances, referring again to  FIGS. 35-37 , the tissue thickness compensator  1170  can be prepared using traditional lyophilization techniques and/or any other suitable techniques. In certain instances, the tissue thickness compensator  1170  can be resized, as illustrated in  FIG. 37 , using a thermal pressing process and a mold  1172 , for example. The mold  1172  may comprise a receiver  1174  configured to receive the tissue thickness compensator  1170  and an adjustment member  1176  which can be partially insertable into the receiver  1174 . The tissue thickness compensator  1170  can be resized when the tissue thickness compensator  1170  is transitioned into a glassy state. In one embodiment, the tissue thickness compensator  1170  can be heated in an oven (not shown) to a temperature greater than or equal to a glass transition temperature of the material composition of the tissue thickness compensator  1170  but less than the melting temperature of the same. In another embodiment, the receiver  1174  and/or the adjustment member  1176  may comprise a heating element for transitioning the tissue thickness compensator  1170  to the glassy state. The adjustment member  1176  can then be inserted into the receiver  1174   a  distance H 3 , for example, as illustrated in  FIG. 37 , thereby compressing the tissue thickness compensator  1170  and reducing its height from the first height H 1  to the second height H 2 . In some instances, the adjustment member  1176  can be inserted into the receiver  1174  before the tissue thickness compensator  1170  enters into the glassy state or just as the tissue thickness compensator  1170  enters into the glassy state. The adjustment member  1176  can be held against the tissue thickness compensator  1170  to compress the tissue thickness compensator  1170  for a time period sufficient to permit the tissue thickness compensator  1170  to retain, or at least substantially retain, the second height H 2 , as illustrated in  FIG. 36 . The tissue thickness compensator  1170  can then be allowed to cool to a temperature below the glass transition temperature while under compression from the adjustment member  1176 . After transitioning the tissue thickness compensator  1170  out of the glassy state, the adjustment member  1176  can be retracted. In some instances, the adjustment member  1176  can be retracted before the tissue thickness compensator  1170  exits the glassy state. In certain circumstances, the above described resizing process can be utilized to change another dimension of the tissue thickness compensator  1170  such as a length or a width of the tissue thickness compensator  1170 , for example. In some circumstances, these dimensions can be modified simultaneously or modified sequentially. 
     In certain examples, the compression from the adjustment member  1176  can be maintained for a period of time from about 30 seconds to about 8 hours, for example, during the time in the glassy state and/or for a period of time from about 30 seconds to about 8 hours, for example, after exiting the glassy state. In at least one example, the compression from the adjustment member  1176  can be maintained for approximately 10 minutes during the time in the glassy state and for approximately 10 minutes after exiting the glassy state. Other time periods for maintaining the compression imposed by the adjustment member  1176  against the tissue thickness compensator  1170  are contemplated by the present disclosure. 
     In certain circumstances, the adjustment member  1176  can be used to apply pressure onto the tissue thickness compensator  1170  before the tissue thickness compensator  1170  is transitioned to the glassy state. In certain circumstances, the adjustment member  1176  may apply pressure to the tissue thickness compensator  1170  while the tissue thickness compensator  1170  is heated to reach the glassy state, while the tissue thickness compensator  1170  is in the glassy state, and/or while the tissue thickness compensator  1170  is transitioned or cooled to a temperature below the glassy state. In certain circumstances, the pressure applied to the tissue thickness compensator  1170  can be gradually increased toward a threshold as the temperature of the tissue thickness compensator  1170  is gradually transitioned toward the glassy state, for example. In certain circumstances, the pressure applied to the tissue thickness compensator  1170  can be removed, gradually removed, or at least partially reduced as the tissue thickness compensator  1170  exits the glassy state, before the tissue thickness compensator  1170  exits the glassy state, and/or after the tissue thickness compensator  1170  exits the glassy state. 
     The reader will appreciate that the different molds utilized in the modification processes described above such as, for example, the molds  1144 ,  1154 , and/or  1172  are illustrative examples. Other mold designs and configurations can also be employed to manipulate tissue thickness compensators in a variety of ways. Furthermore, the forces involved in manipulating a tissue thickness compensator need not only be compressive forces. For example, tensile forces can also be utilized to modify, reshape, and/or resize a tissue thickness compensator in similar manners to those described above. For example, the tissue thickness compensator  1170  can be stretched using tensile forces to reduce its height from the first height H 1  ( FIG. 35 ) to the second height H 2  ( FIG. 36 ), for example, using a modification process that is similar in many respects to the modification processes described above. In certain circumstances, combinations of tensile and compressive forces can be used to manipulate a tissue thickness compensator during a modification process. 
     Referring again to  FIGS. 35-37 , it may be desirable to modify the porosity of a tissue thickness compensator for use in a surgical procedure. A tissue thickness compensator may comprise a porous, open cell foam and/or a porous, closed cell foam, for example. Traditional lyophilization techniques may provide some control over a tissue thickness compensator&#39;s porosity but such control may not be easily reproducible and may need additional fine adjustments that may not be obtainable by traditional lyophilization techniques. As illustrated in  FIGS. 35-37 , the height of the tissue thickness compensator  1170  can be changed from the first height H 1  ( FIG. 35 ) to the second height H 2  ( FIG. 36 ), for example, using the modification process described above. In addition, porosity of the tissue thickness compensator  1170  can also be modified using the same and/or a similar modification process. For example, the tissue thickness compensator  1170  may comprise a first porosity ( FIG. 35 ) prior to the modification process and a second porosity ( FIG. 36 ) after completion of the modification process, as described above. The change in porosity can be attributed, at least in part, to the compressive forces and/or the energy applied to the tissue thickness compensator  1170  by the adjustment member  1176  during the modification process described above. 
     Further to the above, the tissue thickness compensator  1170  may comprise a plurality of pores  1180 . Some or all of the pores  1180  may be altered in position, size, and/or shape, for example, as a result of the modification process described above. For example, one or more of the pores  1180  may comprise a spherical, or substantially spherical, shape prior to the modification process which may be altered to an oval, or substantially oval, shape as a result of the modification process. In at least one example, one or more of the pores  1180  may comprise a first size prior to the modification process and a second size different from the first size as a result of the modification process. In certain circumstances, as described below in greater detail, the porosity changes can be localized to one or more regions or zones of the tissue thickness compensator  1170 . 
     Furthermore, in certain circumstances, the change in porosity of the tissue thickness compensator  1170  may be accompanied by a change in density of the tissue thickness compensator  1170 . In other words, as the adjustment member  1176  is advanced against the tissue thickness compensator  1170 , compressive forces may reduce space occupied by the tissue thickness compensator  1170  thereby causing material and/or pore redistribution which may yield an increase in the density of the tissue thickness compensator  1170  and/or a reduction in its porosity. In certain circumstances, as described below in greater detail, the density changes can be localized to one or more regions or zones of the tissue thickness compensator  1170 . 
     Further to the above, the change in porosity and/or density of the tissue thickness compensator  1170  may yield a change in the spring rate of the tissue thickness compensator  1170 . A tissue thickness compensator&#39;s spring rate can influence its ability to compensate for tissue thickness when the tissue thickness compensator is deployed against tissue captured by staples such as, for example, the staples  20230  ( FIG. 8 ), as described above in greater detail. Furthermore, a tissue thickness compensator&#39;s spring rate can also influence its ability to apply pressure against tissue captured with the tissue thickness compensator by a staple. In other words, a change in a tissue thickness compensator&#39;s spring rate may change the pressure exerted by the tissue thickness compensator against tissue captured by a staple. Since different tissue types may respond more positively to certain pressures, fine control over a tissue thickness compensator&#39;s spring rate can be advantageous. 
     As illustrated in  FIGS. 35-37 , the tissue thickness compensator  1170  may comprise a first spring rate ( FIG. 35 ) which may be altered or modified to a second spring rate ( FIG. 36 ) different from the first spring rate using the modification process described above. For example, as described above, the adjustment member  1176  can be advanced against the tissue thickness compensator  1170  while the tissue thickness compensator  1170  is in the glassy state. In response, the tissue thickness compensator  1170  may be compressed which may cause a change in the spring rate of the tissue thickness compensator  1170 . The adjustment member  1176  can be retained in the advanced position for a period of time sufficient to permit the tissue thickness compensator  1170  to retain, or at least substantially retain, the change in spring rate. In addition, the tissue thickness compensator  1170  can be allowed to cool below the glass transition temperature of its material composition while maintaining the pressure applied by the adjustment member  1176  against the tissue thickness compensator  1170 . 
     In certain instances, the adjustment member  1176  can be maintained in the advanced position against the tissue thickness compensator  1170  for a period of time from about 30 seconds to about 8 hours, for example, during the time in the glassy state and/or for a period of time from about 30 seconds to about 8 hours, for example, after exiting the glassy state. In at least one example, the adjustment member  1176  can be maintained in the advanced position against the tissue thickness compensator  1170  for approximately 10 minutes during the time in the glassy state and for approximately 10 minutes after exiting the glassy state. Other time periods for maintaining the adjustment member  1176  in the advanced position against the tissue thickness compensator  1170  are contemplated by the present disclosure. 
     In certain circumstances, the adjustment member  1176  can be used to apply pressure onto the tissue thickness compensator  1170  to change the spring rate of the tissue thickness compensator  1170  before the tissue thickness compensator  1170  is transitioned to the glassy state. In certain circumstances, the adjustment member  1176  may apply pressure to the tissue thickness compensator  1170  while the tissue thickness compensator  1170  is heated to reach the glassy state, while the tissue thickness compensator  1170  is in the glassy state, and/or while the tissue thickness compensator  1170  is transitioned or cooled to a temperature below the glassy state. In certain circumstances, the pressure applied to the tissue thickness compensator  1170  can be gradually increased toward a threshold as the temperature of the tissue thickness compensator  1170  is gradually increased to transition the tissue thickness compensator  1170  toward the glassy state, for example. In certain circumstances, the pressure applied to the tissue thickness compensator  1170  can be removed, gradually removed, or at least partially reduced as the tissue thickness compensator  1170  exits the glassy state, before the tissue thickness compensator  1170  exits the glassy state, and/or after the tissue thickness compensator  1170  exits the glassy state. 
     Referring again to  FIGS. 35-40 , the tissue thickness compensator  1170  may be manufactured with a native spring rate using traditional lyophilization techniques and/or any other suitable techniques. As described above, the spring rate of the tissue thickness compensator  1170  can influence its ability to apply pressure against tissue captured with the tissue thickness compensator  1170  by a staple. The modification process described above may be utilized to adjust the native spring rate of the tissue thickness compensator  1170  to adjust its ability to apply pressure against tissue captured with the tissue thickness compensator  1170  by the staple. In certain circumstances, the native spring rate of the tissue thickness compensator  1170  can be increased from a first spring rate at point A ( FIG. 40 ) to a second spring rate including and up to a maximum spring rate at point B ( FIG. 40 ). In certain circumstances, such increase of the spring rate of the tissue thickness compensator  1170  can be achieved by applying compression forces to the tissue thickness compensator  1170  using the adjustment member  1176  while the tissue thickness compensator  1170  is in the glassy state, as explain in the modification process described above. As illustrated in  FIG. 40 , the point B represents a maximum elastic yield of the tissue thickness compensator  1170 . As such, any additional compression applied by the adjustment member  1176  to the tissue thickness compensator  1170  beyond a threshold compression at the point B may produce a decrease in the spring rate of the modified tissue thickness compensator  1170 . For example, as illustrated in  FIG. 40 , the spring rate at the point C is lower than the spring rate at the point B even though the compression force applied by the adjustment member  1176  to the tissue thickness compensator  1170  at point C is greater than the compression force applied at the point B. 
     As discussed above, one or more processes can be used to affect the spring rate, and/or any other property, of a material used in conjunction with a fastener cartridge and/or a surgical fastening instrument, for example. The spring rate, and/or any other property, of the material may change throughout the modification process or processes. Such a change may be gradual in some circumstances, while in other circumstances, the change may be sudden. In various instances, one or more of the steps of the modification process may cause an increase in the spring rate of the material while one or more steps may cause a decrease in the spring rate of the material. Ultimately, the net change in the spring rate can be measured as a comparison between an original spring rate before the modification process begins and a subsequent spring rate after the modification process has been completed. In various instances, a material may comprise an altered spring rate after the material has been heated and then cooled. 
     In certain circumstances, it may be desirable to apply one or more of the above described modification processes to a tissue thickness compensator. For example, a first modification process can be utilized to modify porosity of the tissue thickness compensator, as described above with respect to the tissue thickness compensator  1170 . A second modification process, following the first modification process, can be utilized to alter a surface of the tissue thickness compensator, as described above with respect to the tissue thickness compensator  1140 . Furthermore, a third modification process can be utilized to modify the tissue thickness compensator to include a longitudinal slot similar to the longitudinal slot  1122  of the tissue thickness compensator  1120 . In yet a fourth modification process, the tissue thickness compensator can be modified to include apertures similar to the apertures  1152  of the tissue thickness compensator  1150 . The reader will appreciate that some of above mentioned modifications can be combined or grouped in a single modification process. For example, a mold can be designed to include the needles  1156  of the mold  1154  and the central beam  1128  of the mold  1126 . Other modification arrangements are contemplated by the present disclosure. 
     Referring now to  FIGS. 38 and 39 , a tissue thickness compensator such as, for example, tissue thickness compensator  1190  can be altered or modified using one or more of the modification processes described above to include portions with different spring rates, porosities, and/or densities. In certain circumstances, the tissue thickness compensator  1190  can be modified using one or more of the modification processes described above to include a gradient pore morphology (i.e. small pores gradually increasing in size to large pores across the thickness of the tissue thickness compensator  1190  in one direction). Such morphology could be more optimal for tissue in-growth or hemostatic behavior. Further, the gradient could also be compositional with a varying bio-absorption profile. A short term absorption profile may be preferred to address hemostasis while a long term absorption profile may address better tissue healing without leakages. 
     Referring again to  FIGS. 38 and 39 , the tissue thickness compensator  1190  may include one or more zone geometries that are different from the remainder of the tissue thickness compensator  1196 . For example, as illustrated in  FIG. 38 , the tissue thickness compensator  1190  may include one or more protruding portions such as, for example, protruding portion  1196 . In addition, the tissue thickness compensator  1190  may comprise a uniform, or at least a substantially uniform, first spring rate, first porosity, and/or first density through the tissue thickness compensator  1190  including the one or more zone geometries, as illustrated in  FIG. 38 . In certain circumstances, the tissue thickness compensator  1190  can be altered or modified using one or more of the modification processes described above to alter or modify the one or more zone geometries and/or to induce localized changes in the first spring rate, the first porosity, and/or the first density, for example. The modified tissue thickness compensator  1190  may comprise one or more modified zones with different spring rates, porosities, and/or densities from other modified zones and/or the first spring rate, the first porosity, and/or the first density, respectively, of the remainder of the tissue thickness compensator  1190 . In certain circumstances, the resulting one or more modified zones may correspond to the one or more zone geometries. For example, as illustrated in  FIG. 39 , the tissue thickness compensator  1190  may be altered or modified to level, or at least substantially level, the protruding portion  1196  and to form a flat, or at least a substantially flat, surface  1198 , for example. The modified tissue thickness compensator  1190  may include a first portion  1192  comprising the first spring rate, the first porosity, and/or the first density and a second portion  1194  comprising a second spring rate, a second porosity, and/or a second density, which can be different from the first spring rate, the first porosity, and/or the first density, respectively. The second portion  1194  may correspond to the protruding portion  1196  and can result from the leveling, or at least substantially leveling, of the protruding portion  1196  to form the flat, or at least substantially flat, surface  1198 , for example. In certain respects, the geometry of the protruding portion  1196  prior to the modification of the tissue thickness compensator  1190  mirrors, matches, or resembles the geometry of the second portion  1194  after the tissue thickness compensator  1190  has been modified. 
     Referring again to  FIGS. 37-39 , the tissue thickness compensator  1190  can be altered or modified using the mold  1172 , in a similar manner to the tissue thickness compensator  1170 . For example, the tissue thickness compensator  1190  can be heated in the receiver  1174  to a temperature greater than or equal to a glass transition temperature of the material composition of the tissue thickness compensator  1190  but less than the melting temperature of the same. In certain circumstances, the adjustment member  1176  can be advanced against the protruding portion  1196 , while the tissue thickness compensator  1190  is in the glassy state, thereby compressing the protruding portion  1196  and rearranging its geometry to form the second portion  1194 , as illustrated in  FIG. 39 . Further to the above, the adjustment member  1176  can be configured to maintain compression against the protruding portion  1196  for a time period sufficient to permit the tissue thickness compensator  1190  to retain, or at least substantially retain, the modification imposed by the adjustment member  1176 . The tissue thickness compensator  1190  can be allowed to cool or can be actively cooled to a temperature below its glass transition temperature while under compression from the adjustment member  1176 . After transitioning the tissue thickness compensator  1190  out of the glassy state, the adjustment member  1190  can be retracted. The tissue thickness compensator  1190  may retain, or at least substantially retain, the second portion  1194 , as illustrated in  FIG. 39 . In certain circumstances, the adjustment member  1176  may apply pressure onto the protruding portion  1196  while the tissue thickness compensator  1190  is heated to reach the glassy state, while the tissue thickness compensator  1190  is in the glassy state, and/or while the tissue thickness compensator  1190  is transitioned or cooled to a temperature below the glassy state. In certain circumstances, the pressure applied to the protruding portion  1196  of the tissue thickness compensator  1190  can be gradually increased toward a threshold as the temperature of the tissue thickness compensator  1190  is gradually increased to transition the tissue thickness compensator  1190  toward the glassy state, for example. In certain circumstances, the pressure applied to the protruding portion  1196  of the tissue thickness compensator  1190  can be removed, gradually removed, or at least partially reduced as the tissue thickness compensator  1190  exits the glassy state, before the tissue thickness compensator  1190  exits the glassy state, and/or after the tissue thickness compensator  1190  exits the glassy state. 
     Referring now to  FIGS. 41-43 , a tissue thickness compensator such as, for example, tissue thickness compensator  1200  can be prepared using traditional lyophilization techniques and/or any other suitable techniques. In addition, the tissue thickness compensator  1200  can be modified or altered for use in a surgical procedure, for example. The tissue thickness compensator  1200  can be similar in many respects to other tissue thickness compensators such as, for example, the tissue thickness compensator  22020  ( FIG. 9 ) and/or the tissue thickness compensator  1120  ( FIG. 26 ). For example, like the tissue thickness compensator  22020 , the tissue thickness compensator  1200  can be utilized with the end effector  22090 . Furthermore, as illustrated in  FIGS. 41-43 , the tissue thickness compensator  1200  can be modified to include a longitudinal slot  1202  which, like the knife slot  22025 , may define a tissue thickness compensator knife path for the cutting portion  10053  between a first stapling portion  1204   a  and a second stapling portion  1204   b . Furthermore, the first stapling portion  1204   a  and the second stapling portion  1204   b  can be similar in many respects to the first stapling portion  22021   a  ( FIG. 9 ) and the second stapling portion  22021   b  ( FIG. 9 ) of the tissue thickness compensator  22020 . In addition, the slot  1202  can be configured to releasably connect the first stapling portion  1204   a  and the second stapling portion  1204   b  such that, in use with the end effector  22090 , the cutting portion  10053  can be advanced distally through the slot  1202  to transect the slot  1202  and separate the first stapling portion  1204   a  and the second stapling portion  1204   b.    
     Referring again to  FIGS. 41-43 , the tissue thickness compensator  1200  can be modified prior to assembly with an end effector such as, for example, the end effector  22090  ( FIG. 9 ). Alternatively, the tissue thickness compensator  1200  can be modified after it has been assembled with an end effector. As described above, the tissue thickness compensator  1200  can be prepared using traditional lyophilization techniques and/or any other suitable techniques. A space creator  1206  can be utilized to modify the tissue thickness compensator  1200  in a thermal pressing process, as illustrated in  FIGS. 41-43 . For example, the space creator  1206  can be heated to a temperature greater than or equal to a melting temperature of the material composition of the tissue thickness compensator  1200 . The space creator  1206  can then be aligned with and inserted into the tissue thickness compensator  1200  to form the longitudinal slot  1202 . The space creator  1206  may melt through the tissue thickness compensator  1200  to create space for the longitudinal slot  1202 . The space creator  1206  can be retracted upon reaching a desired depth within the tissue thickness compensator  1200 . In certain circumstances, the thermal pressing process can be repeated by reinserting the heated space creator  1206  through the tissue thickness compensator  1200  to widen the space created for the longitudinal slot  1202 . 
     Referring again to  FIGS. 41-43 , the space creator  1206  may comprise a hot wire. For example, the space creator  1206  may comprise a thin, taut metal wire, which can be made of nichrome or stainless steel, for example, or a thicker wire preformed into a desired shape. The hot wire can be heated via electrical resistance to a desired temperature. As the hot wire of the space creator  1206  is passed through the material of the tissue thickness compensator  1200 , the heat from the hot wire may vaporize the material just in advance of contact. In certain circumstances, the hot wire may comprise a cylindrical, or substantially cylindrical, shape, as illustrated in  FIG. 42 . The depth of the longitudinal slot  1202  can depend, in part, on the insertion depth of the space creator  1206  through the tissue thickness compensator  1200  and the width of the longitudinal slot  1202  can depend, in part, on the diameter of the hot wire of the space creator  1206 . 
     In certain instances, the space creator  1206  can be partially inserted through the full thickness of the tissue thickness compensator. In certain instances, the space creator  1206  can be completely inserted through the full thickness of the tissue thickness compensator  1200  to create openings, holes, and/or slots extending through the full thickness of the tissue thickness compensator  1200 . In certain instances, the space creator  1206  may be inserted through a first side of the tissue thickness compensator  1200  and exited through a second side of the tissue thickness compensator  1200  which may be opposite the first side, for example. 
     Many processes are disclosed herein which utilize thermal energy to modify a tissue thickness compensator. Such processes can be referred to as felting processes. In certain instances, a felting process may also utilize the application of compressive and/or tensile forces to a tissue thickness compensator. In other instances, a felting process may not utilize the application of compressive and/or tensile forces to a tissue thickness compensator. In either event, the felting processes disclosed herein can also be utilized to modify and suitable implantable layer and/or buttress material, for example. 
     In various circumstances, the tissue thickness compensator assembly may comprise a polymeric composition. The polymeric composition may comprise one or more synthetic polymer and/or one or more non-synthetic polymer. The synthetic polymer may comprise a synthetic absorbable polymer and/or a synthetic non-absorbable polymer. In various circumstances, the polymeric composition may comprise a biocompatible foam, for example. The biocompatible foam may comprise a porous, open cell foam and/or a porous, closed cell foam, for example. The biocompatible foam can have a uniform pore morphology or may have a gradient pore morphology (i.e. small pores gradually increasing in size to large pores across the thickness of the foam in one direction). In various circumstances, the polymeric composition may comprise one or more of a porous scaffold, a porous matrix, a gel matrix, a hydrogel matrix, a solution matrix, a filamentous matrix, a tubular matrix, a composite matrix, a membranous matrix, a biostable polymer, and a biodegradable polymer, and combinations thereof. For example, the tissue thickness compensator assembly may comprise a foam reinforced by a filamentous matrix or may comprise a foam having an additional hydrogel layer that expands in the presence of bodily fluids to further provide the compression on the tissue. In various circumstances, a tissue thickness compensator assembly could also be comprised of a coating on a material and/or a second or third layer that expands in the presence of bodily fluids to further provide the compression on the tissue. Such a layer could be a hydrogel that could be a synthetic and/or naturally derived material and could be either biodurable and/or biodegradable, for example. In certain circumstances, a tissue thickness compensator assembly could be reinforced with fibrous non-woven materials or fibrous mesh type elements, for example, that can provide additional flexibility, stiffness, and/or strength. In various circumstances, a tissue thickness compensator assembly that has a porous morphology which exhibits a gradient structure such as, for example, small pores on one surface and larger pores on the other surface. Such morphology could be more optimal for tissue in-growth or hemostatic behavior. Further, the gradient could be also compositional with a varying bio-absorption profile. A short term absorption profile may be preferred to address hemostasis while a long term absorption profile may address better tissue healing without leakages. 
     Examples of non-synthetic polymers include, but are not limited to, lyophilized polysaccharide, glycoprotein, elastin, proteoglycan, gelatin, collagen, and oxidized regenerated cellulose (ORC). Examples of synthetic absorbable polymers include, but are not limited to, poly(lactic acid) (PLA), poly(L-lactic acid) (PLLA), polycaprolactone (PCL), polyglycolic acid (PGA), poly(trimethylene carbonate) (TMC), polyethylene terephthalate (PET), polyhydroxyalkanoate (PHA), a copolymer of glycolide and ε-caprolactone (PGCL), a copolymer of glycolide and -trimethylene carbonate, poly(glycerol sebacate) (PGS), polydioxanone, poly(orthoesters), polyanhydrides, polysaccharides, poly(ester-amides), tyrosine-based polyarylates, tyrosine-based polyiminocarbonates, tyrosine-based polycarbonates, poly(D,L-lactide-urethane), poly(B-hydroxybutyrate), poly(E-caprolactone), polyethyleneglycol (PEG), poly[bis(carboxylatophenoxy) phosphazene], poly(amino acids), pseudo-poly(amino acids), absorbable polyurethanes, and combinations thereof. In various circumstances, the polymeric composition may comprise from approximately 50% to approximately 90% by weight of the polymeric composition of PLLA and approximately 50% to approximately 10% by weight of the polymeric composition of PCL, for example. In at least one embodiment, the polymeric composition may comprise approximately 70% by weight of PLLA and approximately 30% by weight of PCL, for example. In various circumstances, the polymeric composition may comprise from approximately 55% to approximately 85% by weight of the polymeric composition of PGA and 15% to 45% by weight of the polymeric composition of PCL, for example. In at least one embodiment, the polymeric composition may comprise approximately 65% by weight of PGA and approximately 35% by weight of PCL, for example. In various circumstances, the polymeric composition may comprise from approximately 90% to approximately 95% by weight of the polymeric composition of PGA and approximately 5% to approximately 10% by weight of the polymeric composition of PLA, for example. 
     In various circumstances, the synthetic absorbable polymer may comprise a bioabsorbable, biocompatible elastomeric copolymer. Suitable bioabsorbable, biocompatible elastomeric copolymers include but are not limited to copolymers of epsilon-caprolactone and glycolide (preferably having a mole ratio of epsilon-caprolactone to glycolide of from about 30:70 to about 70:30, preferably 35:65 to about 65:35, and more preferably 45:55 to 35:65); elastomeric copolymers of epsilon-caprolactone and lactide, including L-lactide, D-lactide blends thereof or lactic acid copolymers (preferably having a mole ratio of epsilon-caprolactone to lactide of from about 35:65 to about 65:35 and more preferably 45:55 to 30:70) elastomeric copolymers of p-dioxanone (1,4-dioxan-2-one) and lactide including L-lactide, D-lactide and lactic acid (preferably having a mole ratio of p-dioxanone to lactide of from about 40:60 to about 60:40); elastomeric copolymers of epsilon-caprolactone and p-dioxanone (preferably having a mole ratio of epsilon-caprolactone to p-dioxanone of from about 30:70 to about 70:30); elastomeric copolymers of p-dioxanone and trimethylene carbonate (preferably having a mole ratio of p-dioxanone to trimethylene carbonate of from about 30:70 to about 70:30); elastomeric copolymers of trimethylene carbonate and glycolide (preferably having a mole ratio of trimethylene carbonate to glycolide of from about 30:70 to about 70:30); elastomeric copolymer of trimethylene carbonate and lactide including L-lactide, D-lactide, blends thereof or lactic acid copolymers (preferably having a mole ratio of trimethylene carbonate to lactide of from about 30:70 to about 70:30) and blends thereof. In one embodiment, the elastomeric copolymer is a copolymer of glycolide and epsilon-caprolactone. In another embodiment, the elastomeric copolymer is a copolymer of lactide and epsilon-caprolactone. 
     The disclosures of U.S. Pat. No. 5,468,253, entitled ELASTOMERIC MEDICAL DEVICE, which issued on Nov. 21, 1995, and U.S. Pat. No. 6,325,810, entitled FOAM BUTTRESS FOR STAPLING APPARATUS, which issued on Dec. 4, 2001, are hereby incorporated by reference in their respective entireties. 
     In various circumstances, the synthetic absorbable polymer may comprise one or more of 90/10 poly(glycolide-L-lactide) copolymer, commercially available from Ethicon, Inc. under the trade designation VICRYL (polyglactic 910), polyglycolide, commercially available from American Cyanamid Co. under the trade designation DEXON, polydioxanone, commercially available from Ethicon, Inc. under the trade designation PDS, poly(glycolide-trimethylene carbonate) random block copolymer, commercially available from American Cyanamid Co. under the trade designation MAXON, 75/25 poly(glycolide-E-caprolactone-poliglecaprolactone 25) copolymer, commercially available from Ethicon under the trade designation MONOCRYL, for example. 
     Examples of synthetic non-absorbable polymers include, but are not limited to, foamed polyurethane, polypropylene (PP), polyethylene (PE), polycarbonate, polyamides, such as nylon, polyvinylchloride (PVC), polymethylmetacrylate (PMMA), polystyrene (PS), polyester, polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE), polytrifluorochloroethylene (PTFCE), polyvinylfluoride (PVF), fluorinated ethylene propylene (FEP), polyacetal, polysulfone, and combinations thereof. The synthetic non-absorbable polymers may include, but are not limited to, foamed elastomers and porous elastomers, such as, for example, silicone, polyisoprene, and rubber. In various circumstances, the synthetic polymers may comprise expanded polytetrafluoroethylene (ePTFE), commercially available from W. L. Gore &amp; Associates, Inc. under the trade designation GORE-TEX Soft Tissue Patch and co-polyetherester urethane foam commercially available from Polyganics under the trade designation NASOPORE. 
     The polymeric composition of a tissue thickness compensator assembly may be characterized by percent porosity, pore size, and/or hardness, for example. In various circumstances, the polymeric composition may have a percent porosity from approximately 30% by volume to approximately 99% by volume, for example. In certain circumstances, the polymeric composition may have a percent porosity from approximately 60% by volume to approximately 98% by volume, for example. In various circumstances, the polymeric composition may have a percent porosity from approximately 85% by volume to approximately 97% by volume, for example. In at least one embodiment, the polymeric composition may comprise approximately 70% by weight of PLLA and approximately 30% by weight of PCL, for example, and can comprise approximately 90% porosity by volume, for example. In at least one such embodiment, as a result, the polymeric composition would comprise approximately 10% copolymer by volume. In at least one embodiment, the polymeric composition may comprise approximately 65% by weight of PGA and approximately 35% by weight of PCL, for example, and can have a percent porosity from approximately 93% by volume to approximately 95% by volume, for example. In various circumstances, the polymeric composition may comprise a greater than 85% porosity by volume. The polymeric composition may have a pore size from approximately 5 micrometers to approximately 2000 micrometers, for example. In various circumstances, the polymeric composition may have a pore size between approximately 10 micrometers to approximately 100 micrometers, for example. In at least one such embodiment, the polymeric composition can comprise a copolymer of PGA and PCL, for example. In certain circumstances, the polymeric composition may have a pore size between approximately 100 micrometers to approximately 1000 micrometers, for example. In at least one such embodiment, the polymeric composition can comprise a copolymer of PLLA and PCL, for example. According to certain aspects, the hardness of a polymeric composition may be expressed in terms of the Shore Hardness, which can defined as the resistance to permanent indentation of a material as determined with a durometer, such as a Shore Durometer. In order to assess the durometer value for a given material, a pressure is applied to the material with a durometer indenter foot in accordance with ASTM procedure D2240-00, entitled, “Standard Test Method for Rubber Property-Durometer Hardness”, the entirety of which is incorporated herein by reference. The durometer indenter foot may be applied to the material for a sufficient period of time, such as 15 seconds, for example, wherein a reading is then taken from the appropriate scale. Depending on the type of scale being used, a reading of 0 can be obtained when the indenter foot completely penetrates the material, and a reading of 100 can be obtained when no penetration into the material occurs. This reading is dimensionless. In various circumstances, the durometer may be determined in accordance with any suitable scale, such as Type A and/or Type OO scales, for example, in accordance with ASTM D2240-00. In various circumstances, the polymeric composition of a tissue thickness compensator assembly may have a Shore A hardness value from approximately 4 A to approximately 16 A, for example, which is approximately 45 OO to approximately 65 OO on the Shore OO range. In at least one such embodiment, the polymeric composition can comprise a PLLA/PCL copolymer or a PGA/PCL copolymer, for example. In various circumstances, the polymeric composition of a tissue thickness compensator assembly may have a Shore A Hardness value of less than 15 A. In various circumstances, the polymeric composition of a tissue thickness compensator assembly may have a Shore A Hardness value of less than 10 A. In various circumstances, the polymeric composition of a tissue thickness compensator assembly may have a Shore A Hardness value of less than 5 A. In certain circumstances, the polymeric material may have a Shore OO composition value from approximately 35 OO to approximately 75 OO, for example. 
     In various circumstances, the polymeric composition may have at least two of the above-identified properties. In various circumstances, the polymeric composition may have at least three of the above-identified properties. The polymeric composition may have a porosity from 85% to 97% by volume, a pore size from 5 micrometers to 2000 micrometers, and a Shore A hardness value from 4 A to 16 A and Shore OO hardness value from 45 OO to 65 OO, for example. In at least one embodiment, the polymeric composition may comprise 70% by weight of the polymeric composition of PLLA and 30% by weight of the polymeric composition of PCL having a porosity of 90% by volume, a pore size from 100 micrometers to 1000 micrometers, and a Shore A hardness value from 4 A to 16 A and Shore OO hardness value from 45 OO to 65 OO, for example. In at least one embodiment, the polymeric composition may comprise 65% by weight of the polymeric composition of PGA and 35% by weight of the polymeric composition of PCL having a porosity from 93% to 95% by volume, a pore size from 10 micrometers to 100 micrometers, and a Shore A hardness value from 4 A to 16 A and Shore OO hardness value from 45 OO to 65 OO, for example. 
     In various circumstances, the polymeric composition may comprise a pharmaceutically active agent. The polymeric composition may release a therapeutically effective amount of the pharmaceutically active agent. In various circumstances, the pharmaceutically active agent may be released as the polymeric composition is desorbed/absorbed. In various circumstances, the pharmaceutically active agent may be released into fluid, such as, for example, blood, passing over or through the polymeric composition. Examples of pharmaceutically active agents may include, but are not limited to, hemostatic agents and drugs, such as, for example, fibrin, thrombin, and oxidized regenerated cellulose (ORC); anti-inflammatory drugs, such as, for example, diclofenac, aspirin, naproxen, sulindac, and hydrocortisone; antibiotic and antimicrobial drug or agents, such as, for example, triclosan, ionic silver, ampicillin, gentamicin, polymyxin B, chloramphenicol; and anticancer agents, such as, for example, cisplatin, mitomycin, adriamycin. 
     Various methods are disclosed herein for altering a tissue thickness compensator. Such methods could be used to alter any suitable layer for use with a fastener cartridge and/or a surgical fastening instrument, for example. Such a layer can comprise a less than one hundred percent dense composition which can be created utilizing any suitable process. For instance, such processes can include, for example, extruding, injection molding, weaving, lyophilization, gas-foaming, and/or melt-blowing processes. Some processes may produce a foam while other processes may not produce a foam; however, in any event, all such embodiments are contemplated for use with all of the embodiments disclosed herein. 
     In various embodiments, referring to  FIGS. 44-46 , an end effector of a surgical fastening instrument, such as end effector  100 , for example, can be configured to capture, fasten, and/or incise tissue. The end effector  100  can include a fastener cartridge  110  and, in addition, a firing member  140  which can be advanced through the fastener cartridge  110  to deploy staples removably stored within the staple cartridge  110  into tissue captured within the end effector  100 . In various instances, the firing member  140  can be advanced from a proximal position ( FIG. 44 ) toward a distal end of the end effector  100  to simultaneously deploy the staples and transect the tissue. There are some circumstances, however, where it may not be desirable to advance the firing member  140  toward the distal end of the end effector  100 . For instance, the fastener cartridge  110  of the end effector  100  can be removable and/or replaceable and, in the event that a fastener cartridge  110  is not positioned within the end effector  100 , it may not be desirable for the firing member  140  to be advanced within the end effector  100 . In the event that the firing member  140  were to be advanced through the end effector  100  without a fastener cartridge positioned within the end effector  100 , a knife edge  142  of the firing member  140  may incise tissue captured within the end effector  100  without simultaneously fastening the tissue. Similarly, in the event that the fastener cartridge positioned within the end effector  100  has been previously used, or expended, and at least some of the fasteners have been deployed from the fastener cartridge, it may not be desirable for the firing member  140  to be advanced within the end effector  100 . In the event that the firing member  140  were to be advanced through the end effector  100  with a previously expended fastener cartridge positioned within the end effector  100 , the knife edge  142  of the firing member  140  may incise tissue captured within the end effector without simultaneously fastening the tissue. In various embodiments, the end effector  100  can include one or more lockout systems which can prevent the firing member  140  from being advanced distally when a fastener cartridge is not present within the end effector  100  and/or when the fastener cartridge positioned within the end effector  100  has been at least partially expended. Various lockout systems are disclosed in U.S. Pat. No. 6,988,649, entitled SURGICAL STAPLING INSTRUMENT HAVING A SPENT CARTRIDGE LOCKOUT, and issued on Jan. 24, 2006. The entire disclosure of U.S. Pat. No. 6,988,649, entitled SURGICAL STAPLING INSTRUMENT HAVING A SPENT CARTRIDGE LOCKOUT, is incorporated by reference herein. 
     Referring again to  FIGS. 44-46 , the fastener cartridge  110  can include a cartridge body and a tissue thickness compensator  120  wherein, further to the above, the tissue thickness compensator  120  can be implanted against tissue captured by the end effector  100  by fasteners removably stored within the cartridge body. The tissue thickness compensator  120  can be positioned above a top surface, or deck, of the cartridge body wherein staples  180  removably stored within staple cavities defined in the cartridge body can be ejected from the staple cavities by a firing member, such as sled  130  and/or firing member  140 , for example. In certain embodiments, the fastener cartridge  110  can further include drivers configured to support the staples  180  and transmit the movement of the sled  130  to the staples  180  in order to move the staples  180  between an unfired position and a fired position. In various instances, the staples  180  can be at least partially embedded in the tissue thickness compensator  120  when the staples  180  are in their unfired positions and, in certain instances, the staples  180  can hold the tissue thickness compensator  120  in position over the cartridge deck when the staples  180  are in their unfired position. In the event that the tissue thickness compensator  120  were to be moved relative to the cartridge body and/or the staples  180  prior to deploying the staples  180  into tissue, in some instances, the tissue thickness compensator  120  may move the staples  180  relative to or away from their preferred positions. Moreover, in the event that the tissue thickness compensator  120  were to be removed from the cartridge  110  prior to the staples  180  being deployed, the cartridge  110  may no longer be suitable for its originally intended use. In view of the foregoing, as discussed in greater detail below, the end effector  100  may include a lockout configured to prevent the firing member  140  and/or the sled  130  from being advanced distally to deploy the staples  180  in the event that the tissue thickness compensator  120  is removed from, or becomes at least partially dislodged from, the cartridge body prior to the staples  180  being deployed. 
     Referring again to  FIGS. 44-46 , the tissue thickness compensator  120  can comprise, one, a body  121  configured to be captured by the staples  180  and, two, a lockout pin  122  extending from the body  121 . In various instances, the lockout pin  122  can include a first end  123  embedded in the body  121  and a second end  124  positioned intermediate the firing member  140  and the sled  130  when the tissue thickness compensator  120  has not been removed from or substantially moved from a suitable position over the cartridge body deck. In such a position, the second end  124  of the lockout pin  122  can be positioned intermediate a shoulder, or shelf,  134  defined on the sled  130  and a protrusion  144  extending distally from the firing bar  140 . Stated another way, when the lockout pin  122  is positioned intermediate the sled  130  and the firing bar  140 , the lockout pin  122  and the sled  130  can co-operate to support the firing bar  140  in an unlocked position above a lockout shoulder  112  defined in the fastener cartridge  110  such that, when a distal firing force is applied to the firing bar  140 , the firing bar  140  can advance the sled  130  distally to fire the staples  180 . When the tissue thickness compensator  120  is removed from the cartridge  110  and/or sufficiently dislodged from a desirable position relative to the cartridge body, referring primarily to  FIG. 45 , the lockout pin  122  may no longer be positioned intermediate the sled  130  and the firing member  140  and/or may otherwise be unable to support the firing member  140  in its unlocked position ( FIG. 44 ). In such circumstances, the firing member  140  may become positioned in a locked position such that the distal advancement of the firing member  140  is prevented by the lockout shoulder  112 . In at least one such circumstance, the end effector  100  can further include a biasing member, such as a spring, for example, configured to bias the firing member  140  into its locked condition. In certain circumstances, the biasing member can bias the firing member  140  into contact with the sled  130 , for instance, without the lockout pin  122  positioned therebetween which can comprise the locked position of the firing member  140 . 
     As a result of the above, the cartridge  110  may become inoperable if the tissue thickness compensator  120  is prematurely removed from the cartridge  110 . In such circumstances, the lockout pin  122  may comprise a fuse which deactivates the cartridge  110  in the event that the tissue thickness compensator  120  is removed before the firing member  140  is advanced distally. In various circumstances, the lockout pin  122  may comprise a key which maintains the cartridge  110  in an unlocked condition when the key is positioned between the sled  130  and the firing member  140  and permits the cartridge  110  to enter into a locked condition in the event that the tissue thickness compensator  120  is removed from the cartridge  110  before the firing member  140  is advanced distally, i.e., before the firing member  140  begins its firing stroke. When the firing member  140  is in its locked-out condition and cannot be advanced distally, the knife edge  142  of the firing member  140  is unable to incise the tissue captured within the end effector  100 . Moreover, in such circumstances, the firing member  140  cannot advance the sled  130  distally to fire the staples  180 . Thus, the tissue thickness compensator lockout can prevent the tissue captured within the end effector  100  from being incised and stapled when the tissue thickness compensator  120  is not positioned on, or properly positioned on, the cartridge  110 . In the event that the firing member  140  is advanced distally before the tissue thickness compensator  120  is removed, or dislodged, the firing member  140  can complete the firing stroke, or at least a portion of the firing stroke, of the end effector  100 . In such instances, the sled  130  is advanced distally so that one or more ramps  132  defined on the sled  130  can lift the staples  180  and that a knife edge  142  of the firing member  140  can incise the tissue thickness compensator  120  and/or the tissue captured within the end effector  100 . In some circumstances, the firing member  140  can contact the lockout pin  122  and displace it out of the way as the firing member  140  is advanced distally. In such circumstances, the lockout pin  122  can be flexible. In various instances, the lockout pin  122  can be comprised of a bioabsorbable material and/or a biocompatible material, for example. In certain circumstances, the firing member  140  can incise the lockout pin  122  as the firing member  140  is advanced distally. In any event, the purpose of the lockout pin  122  may become obsolete once the firing member  140  has been at least partially advanced. Stated another way, the tissue thickness compensator lockout can serve as an initial check to verify that a tissue thickness compensator is present within the end effector and, once that initial check has been made, the firing stroke of the end effector can proceed. 
     Referring again to  FIGS. 47-50 , an end effector  200  can comprise an anvil  260  and, in addition, a fastener cartridge  210  including a cartridge body  214  and a tissue thickness compensator  220  wherein, further to the above, the tissue thickness compensator  220  can be implanted against tissue captured by the end effector  200  by fasteners removably stored within the cartridge body  214 . The tissue thickness compensator  220  can be positioned above a top surface, or deck,  211  of the cartridge body  214  wherein staples removably stored within staple cavities defined in the cartridge body  214  can be ejected from the staple cavities by a firing member, such as a sled  230  and/or a firing member  240 , for example. In certain embodiments, the fastener cartridge  210  can further include drivers configured to support the staples and transmit the movement of the sled  230  to the staples in order to move the staples between an unfired position and a fired position. In various instances, the staples can be at least partially embedded in the tissue thickness compensator  220  when the staples are in their unfired positions and, in certain instances, the staples can hold the tissue thickness compensator  220  in position when the staples are in their unfired position. In the event that the tissue thickness compensator  220  were to be moved relative to the cartridge body  214  and/or the staples prior to deploying the staples into the tissue, in some instances, the tissue thickness compensator  220  may move the staples relative to or away from their preferred positions. Moreover, in the event that the tissue thickness compensator  220  were to be removed from the cartridge  210  prior to the staples being deployed, the cartridge  210  may no longer be suitable for its originally intended use. In view of the foregoing, as discussed in greater detail below, the end effector  200  may include a lockout configured to prevent the firing member  240  and/or the sled  230  from being advanced distally to deploy the staples in the event that the tissue thickness compensator  220  is removed from, or becomes at least partially dislodged from, the cartridge body  214  prior to the staples being deployed. 
     Referring again to  FIGS. 44-46 , the tissue thickness compensator  220  can comprise, one, a body  221  configured to be captured by the staples and, two, a loop, or tether,  222  extending from the body  221 . In various instances, referring primarily to  FIG. 47 , the loop  222  can comprise ends which are at least partially embedded in the body  221  and an intermediate portion extending between the ends which can be releasably engaged with the sled  230 . In certain instances, the loop  222  can comprise a suture or flexible thread, for example. In some instances, the loop  222  can be comprised of a bioabsorbable material and/or a biocompatible material, for example. Referring primarily to  FIG. 48 , the sled  230  can include a longitudinal body portion  236 , a hook  238  extending from the body portion  236 , and a slot  237  defined between the body portion  236  and the hook  238 . As illustrated in  FIG. 48 , the loop  222  is positioned within the slot  237  when the tissue thickness compensator  220  is positioned over the cartridge deck  211  and the sled  230  and the firing member  240  are in an unfired position. As also illustrated in  FIG. 48 , a distal projection  244  extending from the firing member  240  is positioned against and/or above a support shoulder  234  defined on the sled  230  which holds the firing member  240  in an unlocked position, i.e., in a position in which the distal movement of the firing member  240  will not be impeded, or at least substantially impeded, by a lockout shoulder  212  defined in the end effector  200  when a firing motion is applied to the firing member  240 . Thus, when the sled  230  holds the firing member  240  in its unlocked position, referring to  FIG. 49 , the firing member  240  will slide past the lockout shoulder  212  to advance the sled  230  distally, fire the staples removably stored within the cartridge body  214 , and incise the tissue thickness compensator and the tissue positioned within the end effector  200  with a knife edge  242 . As illustrated in  FIG. 49 , the loop  222  can slide out of the slot  237  defined in the sled  230  when the sled  230  is advanced distally. 
     In the event that the tissue thickness compensator  220  is removed from the cartridge  210  or substantially moved from a suitable position over the deck  211  of the cartridge  210 , referring now to  FIG. 50 , the tissue thickness compensator  220  can pull the sled  230  distally such that the firing member  240  is no longer supported by the sled  230 . More particularly, the loop  222  of the tissue thickness compensator  220  positioned within the slot  237  can pull the sled  230  distally from its unfired position such that the support shoulder  234  is no longer positioned under the distal projection  244  of the firing member  240 . In such circumstances, the firing member  240  may shift downwardly into a locked position wherein the distal movement of the firing member  240  can be impeded by the lockout shoulder  212 . In certain circumstances, the end effector  200  can further include a biasing member, such as a spring, for example, which can bias the firing member  240  into its locked condition. When the firing member  240  is in its locked condition, the firing member  240  cannot be moved distally to advance the sled  230 , fire the staples from the cartridge body  210 , and/or incise the tissue captured within the end effector  200 . Although the sled  230  may be advanced distally when the tissue thickness compensator  220  is removed from the cartridge  210 , the sled  230 , in various circumstances, may not be advanced sufficiently to deploy the staples from the cartridge  210 . When the user of the surgical instrument recognizes that the firing member  240  is in a locked-out condition, the user can remove the staple cartridge  210  from the end effector  200  and replace it with a staple cartridge  210 , for example, in which the tissue thickness compensator  220  is correctly positioned over the deck  211  and the sled  230  has not been advanced distally from its unfired position. Other embodiments are contemplated in which a staple cartridge is not removable from the end effector; in such embodiments, the end effector may be entirely replaced in the event that the tissue thickness compensator is removed from the staple cartridge and/or the firing member enters into a locked-out condition. 
     Turning now to  FIGS. 51-53 , a staple cartridge  310  can include a cartridge body  314  and a sled  330  movably positioned within the cartridge body  314 . Similar to the above, the cartridge body  314  can include a plurality of fastener cavities, such as fastener cavities  316 , for example, and a longitudinal slot, such as knife slot  318 , for example, defined therein. The sled  330  can include a central body portion  336  slidably positioned within the knife slot  318  and a hook  338  extending from the central body portion  336 . Referring primarily to  FIG. 51 , a tissue thickness compensator  320  of the cartridge  310  can include a body portion  321  and a catch  322  extending from the body portion  321  wherein the catch  322  can be releasably retained in a slot  337  defined between the hook  338  and the central body portion  336  when the sled  330  is in its unfired, or unadvanced, position. Similar to the above, the catch  322  can include ends  323  mounted within the body  321  and can extend proximally from the body  321  of the tissue thickness compensator  320  wherein, in the event that the tissue thickness compensator  320  is removed from the cartridge body  314 , for instance, the catch  322  can pull the sled  330  distally such that a support shoulder  334  defined in the central body portion  336  is no longer able to support a firing member, such as firing member  240 , for example, thereon and such that the firing member may enter a locked out state. In various instances, a user of the surgical instrument may attempt to reassemble or reposition the tissue thickness compensator  320  over the deck  311  of the cartridge body  314 ; however, the firing member  340  will still remain in a locked out condition as the repositioning of the tissue thickness compensator  320  will not reset the sled  330 . Thus, such an arrangement can prevent the cartridge  310  from being used if it has been previously tampered with. 
     In various instances, referring again to  FIGS. 51-53 , at least a portion of the hook  338  extending from the central portion  336  of the sled  330  and/or the slot  337  defined therebetween can extend above the deck  311 . In certain instances, at least a portion of the hook  338  extending from the central portion  336  of the sled  330  and/or the slot  337  defined therebetween can extend above the knife slot  318 . In such embodiments, the catch  322  can be easily slid into the slot  337  when the tissue thickness compensator  320  is assembled to the cartridge body  314 . In certain instances, the catch  322  can be positioned above or against the deck surface  311  of the cartridge body  314 . In various instances, referring primarily to  FIG. 53 , the cartridge body  314  can include a recess or pocket  319  defined therein within which the hook  338  can be positioned when the sled  330  is in its unfired, or unadvanced, position. In such an embodiment, the top of the hook  338  may be positioned below the deck surface  311 . In various instances, the pocket  319  can further include one or more ramped surfaces  313  which are defined in the distal end of the pocket  319  and extend downwardly from the deck surface  311 . In some instances, the catch  322  can abut the ramped surfaces  313  when the sled  330  is advanced distally and, in such circumstances, the hook  338  can then separate from the catch  322 . In various instances, the recess  319  can be configured to facilitate the assembly of the catch  322  to the sled  330  when the tissue thickness compensator  320  is assembled to the cartridge body  314 . In various embodiments, the slot  337  can extend longitudinally and can include a closed distal end an open proximal end wherein the catch  322  can be slid into the slot  337  from the open proximal end. In the event that the tissue thickness compensator  320  is not prematurely removed or dislodged from the cartridge  314 , the sled  330  can be advanced distally such that the catch  322  exits the slot  337  through the distal end thereof and such that ramps  332  defined on the sled  330  can eject the staples from the staple cartridge  310 . 
     In various instances, a tissue thickness compensator can be adhered to a sled utilizing at least one adhesive. In such instances, the adhesive attachment between the tissue thickness compensator and the sled can be strong enough to permit the tissue thickness compensator to pull the sled distally in the event that the tissue thickness compensator is removed from the cartridge. When the sled is advanced distally by the firing member as part of the firing stroke, the adhesive attachment between the tissue thickness compensator and the sled may fail thereby permitting the sled to slide distally relative to the tissue thickness compensator. In various instances, a tissue thickness compensator can be bonded to a sled utilizing a heat steak process and/or a thermoform process. In such instances, the bond between the tissue thickness compensator and the sled can be strong enough to permit the tissue thickness compensator to pull the sled distally in the event that the tissue thickness compensator is removed from the cartridge. When the sled is advanced distally by the firing member as part of the firing stroke, the bond between the tissue thickness compensator and the sled may fail thereby permitting the sled to slide distally relative to the tissue thickness compensator. 
     In some instances, a loop, a catch, and/or tag, for example, can be integrally formed with a tissue thickness compensator. In various instances, the loop, catch, and/or tag, for example, can comprise a unitary piece of material with the tissue thickness compensator. In some instances, an additional layer can be attached to the tissue thickness compensator. This layer, in various instances, can comprise a mounting portion engaged with the sled. 
     Turning now to  FIG. 54 , a sled  430  can include, similar to the above, a central body portion  436  and, in addition, a plurality of ramps  432  which are configured to eject staples removably stored within a cartridge body, for example. Also similar to the above, the body portion  436  can include a hook  438  extending therefrom wherein a slot  437  can be defined between the body portion  436  and the hook  438 . In certain instances, the slot  437  can include a closed distal end  437   a  and an open proximal end  437   d . In various instances, the slot  437  can further include a first portion  437   b  extending in a first direction and a second portion  437   c  extending in a second direction. In certain instances, the first portion  437   b  can extend along a longitudinal axis and the second portion  437   c  can extend along a second axis which is transverse to the longitudinal axis. In at least one such instance, the second portion  437   c  can extend at an angle relative to the first portion  437   b.    
     Turning now to  FIGS. 55-58 , a sled assembly  530  can include a first portion  535  and, in addition, a second portion  536  which is movable relative to the first portion  535  between an unlocked position ( FIGS. 55 and 57 ) and a locked position ( FIGS. 56 and 58 ). The first portion  535  can include, one, a central portion configured to slide within a longitudinal slot, such as a knife slot  518  defined in a staple cartridge  510 , for instance, and, two, a plurality of ramps  532  configured to eject staples removably stored within the cartridge  510 . The central portion of the first portion  535  can include a first slot  533   a  and a second slot  533   b  defined therein. The first slot  533   a  and the second slot  533   b  can be configured to receive pins  531   a  and  531   b , respectively, extending from the second portion  536 . The first pin  531   a  can be configured to slide within the first slot  533   a  and the second pin  531   b  can be configured to slide within the second slot  533   b  in order to permit the second portion  536  to rotate relative to the first portion  535 . In various instances, the first pin  531   a  can be closely received within the first slot  533   a  such that the first slot  533   a  can constrain the motion of the first pin  531   a  along a first path and, similarly, the second pin  531   b  can be closely received within the second slot  533   b  such that the second slot  533   b  can constrain the motion of the second pin  531   b  along a second path. Referring primarily to  FIG. 57 , the second portion  536  of the sled assembly  530  can comprise an arm configured to slide within the knife slot  518  wherein the arm can include a support shoulder  534  defined on the proximal end thereof and a hook  538  defined on the distal end thereof. Similar to the above, the support shoulder  534  can be configured to support a firing member  240 , for example, in an unlocked position when the sled assembly  530  is in a proximal, unfired position and the tissue thickness compensator  220 , for instance, is positioned over and/or against the deck surface  511  of the cartridge  510 . Also similar to the above, the hook  538  can be configured to releasably hold the loop  222  of the tissue thickness compensator  220  such that, in the event that the tissue thickness compensator  220  were to be removed from and/or substantially displaced relative to the cartridge body, the loop  222  could pull on the second portion  536  to pivot the second portion  536  into its locked position as illustrated in  FIG. 58 . In such a locked position of the second portion  536 , the support shoulder  534  may no longer support the distal projection  244  of the firing member  240  and the firing member  240  can drop downwardly into its locked position. As depicted in  FIG. 58 , the rotation of the second portion  536  into its locked position can move the support shoulder  534  distally and/or downwardly away from the firing member  240 . As also depicted in  FIG. 58 , the firing member  240  can include a lock  541  extending from opposite sides thereof which can be configured to abut the lockout shoulder  212  when the firing member  240  is in its locked position. When the firing member  240  is held in its unlocked position by the sled assembly  530 , the locks  541  may not contact the lockout shoulder  212  and the firing member  240  can be advanced through the cartridge  510 . 
     In various instances, as discussed above, a portion of a staple-driving sled may extend above the deck surface of a cartridge body. For instance, referring again to  FIGS. 52 and 54 , the hook  338  of the sled  330  ( FIG. 52 ) and/or the hook  438  of the sled  430 , for example, can extend above the deck surface. In such instances, the hook  338  and/or the hook  438  can translate distally above the deck surface and, in some instances, contact the tissue thickness compensator positioned against or above the deck surface. In certain instances, the hook  338  and/or the hook  438  can lift the tissue thickness compensator upwardly away from the cartridge body and facilitate the progressive release of the tissue thickness compensator from the cartridge. For instance, the hook  338  and/or the hook  438  can begin at the proximal end of the tissue thickness compensator and move toward the distal end of the tissue thickness compensator in order to initially lift the proximal end of the tissue thickness compensator and then progressively lift it away from the cartridge deck until the distal end of the tissue thickness compensator is eventually lifted away from the cartridge body. In other instances, as discussed in greater detail further below. it may be preferable for the portion of the sled contacting the tissue thickness compensator to deflect downwardly and/or otherwise not disturb the tissue thickness compensator as the sled is advanced distally. 
     Turning now to  FIGS. 59 and 60 , a staple cartridge  610  can include a cartridge body  614 , a tissue thickness compensator  620  releasably retained to the cartridge body  614 , and a sled  630  configured to longitudinally traverse the cartridge body  614  and eject staples removably stored therein. The sled  630  can include a main body portion  635  having a plurality of ramp surfaces defined thereon, a support shoulder  634 , and an arm  636  extending from the body portion  635 . In various instances, the arm  636  can be assembled to the main body portion  635 . For instance, the arm  636  can include a first end embedded in the main body portion  635  and a second end including a hook  638 , for example. In various instances, the arm  636  can comprise a cantilever beam extending from the main body portion  635 . In certain instances, the arm  636  can be comprised of a resilient and/or flexible material, for example. Similar to the above, a slot  637  can be defined between the hook  638  and the arm  636  which can be configured to releasably hold a portion of the tissue thickness compensator  620  when the sled  630  is in its proximal, unfired position. In the event that the tissue thickness compensator  620  is pulled off of the cartridge body  614 , for example, the tissue thickness compensator  620  can pull the sled  630  distally away from a firing member so that the firing member enters into a locked out condition. 
     In various instances, further to the above, at least a portion of the arm  636 , such as the hook  638 , for example, can extend above the deck surface  611  of the cartridge body  614 . In certain instances, the arm  636  can be engaged with a loop, for example, extending from the tissue thickness compensator  620  when the sled  630  is in its proximal position ( FIG. 59 ) and, as the sled  630  is advanced distally, the arm  636  can disengage from the loop. As the sled  630  is advanced distally, in certain instances, the arm  636  can contact the body portion  621  of the tissue thickness compensator  620  and flex downwardly. In various instances, the deflected arm  636  can slide within a longitudinal knife slot  618  defined in the cartridge body  614  as the sled  630  is advanced distally. In some instances, referring to  FIG. 60 , the distal end of the longitudinal slot  618  can be defined by a nose wall, or roof,  619  wherein, when the sled  630  reaches a distal end  617  of the cartridge  610 , the arm  636  can slide under the nose wall  619  such that the firing stroke of the end effector can be completed. In some instances, the arm  636  may not be deflected, or substantially deflected, downwardly by the tissue thickness compensator  620  wherein, when the arm  636  reaches the end of the longitudinal slot  618 , the arm  636  can contact the nose wall  618  and flex downwardly in order to slide thereunder as illustrated in  FIG. 60 . In various circumstances, as a result, the flexible arm  636  can permit the firing stroke to be completed and for the sled  630  to be parked at the distal end of the cartridge. 
     Turning now to  FIG. 61 , a sled, such as sled assembly  730 , for example, can include a main body portion  735  and a movable arm  736 . Similar to the above, the main body portion  735  can include one or more staple-driving ramps  732  and a support shoulder  734  configured to support a firing member in an unlocked position, as described above. The arm  736  can include a first end pivotably and/or rotatably mounted to the main body portion  735  and a second end including a hook  738  configured to be releasably engaged with a tissue thickness compensator, as described above. When the sled assembly  730  is advanced distally, the hook  738  can detach from the tissue thickness compensator; however, the upper surface of the hook  738  can remain in contact with the bottom surface of the tissue thickness compensator. In such circumstances, the arm  736  can pivot downwardly into the knife slot  318 , for example, in order to slide under the tissue thickness compensator. More particularly, the arm  736  can pivot from a raised, or uppermost, position ( FIG. 61 ) to a lowered, or depressed, position. In various instances, the sled assembly  730  can further include a resilient biasing member, such as a spring  731 , for example, configured to bias the arm  736  into its raised position. When the arm  736  has been rotated downwardly into its lowered position, the spring  731  can apply a biasing force to the arm  736  which is transmitted into the tissue thickness compensator. In certain instances, the spring  731  can be positioned intermediate the arm  736  and a frame portion  733  defined on the main body portion  735 . In various instances, the spring  731  can comprise a cantilever spring or leaf spring, for example, extending from the arm  736 . When the arm  736  is pushed downwardly, the cantilever spring can be configured to flex and/or slide along the frame portion  731 , for instance. In various embodiments, the main body portion  735  can further include a stop shoulder  739 , for example, which can limit the upward rotation, or travel, of the arm  736 . In any event, similar to the above, the arm  736  can be configured to rotate downwardly when it contacts the roof  619  and permit the firing stroke to be completed. 
     In various instances, a staple can comprise a base and one or more legs extending from the base. In certain instances, a staple can comprise a base including a first end and a second end, a first leg extending from the first end, and a second leg extending from the second end. In some instances, the staple can be formed from a continuous wire which comprises the first leg, the base, and the second leg. A first end of the continuous wire can comprise a tip of the first staple leg and a second end of the continuous wire can comprise a tip of the second staple leg. One such staple, i.e., staple  800 , is depicted in  FIG. 62 , for example. The staple  800  can include a base  802 , a first staple leg  804  extending from a first end of the base  802 , and a second staple leg  804  extending from a second end of the base  802 . The first staple leg  804  can include a first tip  806  and, similarly, the second staple leg  804  can include a second tip  806 . In various instances, the tips  806  can be configured to penetrate tissue, such as tissue T depicted in  FIG. 62 , for example. In some instances, the tips  806  can be sharp and can be formed by a coining process, for example. In various embodiments, the wire can be comprised of titanium and/or stainless steel, for example. 
     In various embodiments, the staple  800  can be U-shaped, or at least substantially U-shaped, for example, when it is in its unformed configuration. In such embodiments, the legs  804  of the staple  800  can be parallel, or at least substantially parallel, to one another. Moreover, in such embodiments, the legs  804  can be perpendicular, or at least substantially perpendicular, to the base  802 . In certain embodiments, the staple  800  can be V-shaped, or at least substantially V-shaped, for example, when it is in its unformed configuration. In such embodiments, the legs  804  of the staple  800  are not parallel to one another; rather, the legs  804  can extend in non-parallel directions. Moreover, in such embodiments, one or both of the legs  804  are not perpendicular to the base  802  wherein one or both of the legs  804  can extend in directions which are oblique to the base  802 . In various instances, the legs  804  may extend, or splay, outwardly with respect to a center or midline of the staple. In any event, the staple  800  can be removably stored within a staple cartridge, ejected from the staple cartridge to penetrate tissue, as illustrated in  FIG. 62 , and then contact an anvil positioned on the opposite side of the tissue. The anvil can be configured to deform the staple  800  into any suitable shape, such as a B-form configuration, for example, as also illustrated in  FIG. 62 . Various formed staple configurations, such as the B-form configuration, for example, can define a tissue entrapment area, such as tissue entrapment area  807 , for example, configured to entrap tissue within the staple. 
     As discussed above, a staple can be removably stored within a cavity defined in a cartridge body. A cartridge body  810  is depicted in  FIG. 63  which can include one or more staple cavities  812  defined therein. Referring to  FIGS. 63, 68, and 69 , each staple cavity  812  can include a first end  814  and a second end  814 . In certain embodiments, such as embodiments including a longitudinal end effector, for example, the first end  814  can comprise a proximal end of the staple cavity  812  and the second end  814  can comprise a distal end of the staple cavity  812 . In various instances, a staple can be positioned within a staple cavity  812  such that a first leg  804  of the staple  800  is positioned in the first end  814  of the staple cavity  812  and a second leg  804  is positioned in the second end  814 . In various instances, a staple cavity width can be defined between the ends  814  of a staple cavity  812 . The base  802  of a staple can be defined by a base width which can be equal to or shorter than the staple cavity width, for example. In certain instances, a staple can comprise a staple width which can be defined between the tips  806  of the staple legs  804 . In some embodiments, the staple width can be equal to the staple cavity width. In various embodiments, the staple width can be wider than the staple cavity width. In such embodiments, the legs  804  can be in contact with the ends  814  of a staple cavity  812  and can be resiliently biased inwardly by the ends  814  when the staple is positioned within the staple cavity  812 . When the staple is lifted upwardly out of the staple cavity  812 , the legs  804  can resiliently splay outwardly as they emerge from the staple cavity  812 . For example, the staple can be positioned within the staple cavity  812  such that the tips  806  of the staple legs  804  do not extend above a top surface, or deck, of the cartridge body  810  when the staple is in its unfired, or uplifted, position. In such a position, the tips  806  can be positioned flush with or recessed below the deck  811  of the cartridge body  810 . Alternatively, the tips  806  of the legs  804  can at least partially extend above the deck  811  of the cartridge body  810 . In any event, as the staple is lifted upwardly, the staple tips  806  can emerge above the deck  811  and splay outwardly as the legs  804  emerge from the cavity  812 . At some point during the lifting of the staple, the legs  804  may no longer be in contact with the ends  814  of the staple cavity  812  and the legs  804  may no longer be biased inwardly by the sidewalls of the staple cavity  812 . 
     In various instances, an anvil can include one or more pockets configured to receive the tips  806  of the staple legs  804  as the staple  800  is ejected from the staple cartridge. The anvil pockets can be configured to turn, or bend, the staple legs  804  inwardly toward one another, for example. In other instances, the anvil pockets can be configured to turn, or bend, the staple legs  804  outwardly away from one another, for example. In some instances, however, one or more of the staple legs of a staple may miss a staple pocket and may not be properly deformed. In certain instances, one or more of the staple legs may not contact the anvil and may not be deformed at all. In either event, the staple may not properly capture and/or retain the tissue within its tissue entrapment area. Moreover, the misformed or unformed staple may not be able to apply a desired compressive pressure to the tissue. In some instances, the misformed or unformed staple may not be retained in the tissue and can become dislodged from the tissue. 
     Referring again to  FIG. 62 , the staple  800 , and/or various other staples disclosed herein, can include one or more barbs extending therefrom. In various instances, the barbs can be configured to engage tissue captured within and/or surrounding the staple. In certain instances, the barbs can assist in retaining the staple within the tissue, especially when the staple has been misformed or unformed. The staple  800  can include barbs extending from one or both of the legs  804 . For instance, each leg  804  can include one or more barbs  808  which face outwardly from the center of the staple  800  and/or one or more barbs  809  which face inwardly toward the center of the staple  800 , for example. In certain instances, the barbs  808  can extend away from the tissue entrapment area  807  and/or the barbs  809  can extend toward or into the tissue entrapment area  807 . As depicted in  FIG. 62 , both of the staple legs  804  of staple  800  can include barbs  808  and barbs  809 . In some instances, the staple legs  804  can include barbs  808 , but not barbs  809 . A staple  820  is depicted in  FIG. 63  which includes barbs  808 , but not barbs  809 . In some instances, the staple legs  804  can include barbs  809 , but not barbs  808 . Staples  830 ,  840 ,  850 ,  860 , and  870  are depicted in  FIGS. 64, 65, 66, 67, and 68 , respectively, which include barbs  809 , but not barbs  808 . In some embodiments, a first leg  804  of a staple can include barbs  808  while a second leg  804  of the staple can include barbs  809 , for example. 
     In various instances, the legs  804  and the base  802  of a staple can define a staple plane when the staple is in an unformed configuration. The barbs  808  can extend outwardly from the legs  804  within such a staple plane. Similarly, the barbs  809  can extend inwardly from the legs  804  within such a plane. In some instances, a staple can include barbs which extend laterally with respect to such a staple plane. Other embodiments are envisioned in which the legs  804  and the base  802  do not lie within, or entirely lie within, a single plane. In such embodiments, the barbs can extend in any suitable direction. In various embodiments, referring now to  FIG. 67 , a staple, such as staple  860 , for example, can include barbs  803  extending from the base  802 . In various instances, the barbs  803  can extend inwardly toward the tissue entrapment area  807  of the staple  860 . In certain instances, the barbs  803  can extend outwardly away from the tissue entrapment area  807 . As illustrated in  FIG. 67 , the barbs  803  can extend within a staple plane defined by the legs  804  and the base  802 . In certain instances, the barbs  803  can extend laterally with respect to such a staple plane. Various exemplary barb configurations are discussed in greater detail further below. 
     In various instances, a staple leg  804  can comprise an array of barbs  808  which extends along the entire length thereof. In some instances, a staple leg  804  can comprise an array of barbs  808  which extends along less than the entire length thereof. By way of example, referring to  FIG. 62 , the legs  804  of the staple  800  each comprise an array of barbs  808  which extends along less than the entire length of the legs  804 . Similarly, referring to  FIG. 63 , the legs  804  of the staple  820  each comprise an array of barbs  808  which extends along less than the entire length of the legs  804 . With regard to the staple  800 , for example, an array of barbs  808  can extend along each of the legs  804  from the base  802  of the staple  800  toward the tips  806  of the legs  804 . As illustrated in  FIG. 62 , the arrays of barbs  808  may not extend to the tips  806  of the legs  804 . In various instances, the arrays of barbs  808  can extend along half, or approximately half, the lengths of the legs  804 , for example; however, any suitable length of the barb arrays could be utilized. For instance, the arrays of barbs  808  can extend along less than half or more than half of the lengths of the legs  804 . In some embodiments, an array of barbs  808  can extend along each of the legs  804  from the tips  806  of the legs  804  toward the base  802 . In such embodiments, the array of barbs  808  may not extend to the base  802 . In some embodiments, a leg  804  can comprise an array of barbs  808  which does not extend to the tip  806  of the leg  804  or the base  802 . In certain embodiments, a leg  804  can comprise more than one array of barbs  808 . 
     In various instances, further to the above, a staple leg  804  can comprise an array of barbs  809  which extends along the entire length thereof. By way of example, referring to  FIG. 64 , the legs  804  of the staple  830  each comprise an array of barbs  809  which extends along the entire length of the legs  804 . In some instances, a staple leg  804  can comprise an array of barbs  809  which extends along less than the entire length thereof. By way of example, referring to  FIG. 65 , the legs  804  of the staple  840  each comprise an array of barbs  809  which extends along less than the entire length of the legs  804 . Similarly, referring to  FIG. 68 , the legs  804  of the staple  870  each comprise an array of barbs  809  which extends along less than the entire length of the legs  804 . With regard to the staple  840 , for example, an array of barbs  809  can extend along each of the legs  804  from the base  802  of the staple  840  toward the tips  806  of the legs  804 . As illustrated in  FIG. 65 , the arrays of barbs  809  may not extend to the tips  806  of the legs  804 . In various instances, the arrays of barbs  809  can extend along half, or approximately half, the lengths of the legs  804 , for example; however, any suitable length of the barb arrays could be utilized. For instance, the arrays of barbs  809  can extend along less than half or more than half of the lengths of the legs  804 . In some embodiments, an array of barbs  809  can extend along each of the legs  804  from the tips  806  of the legs  804  toward the base  802 . In such embodiments, the array of barbs  809  may not extend to the base  802 . In some embodiments, as illustrated in  FIG. 66 , a leg  804  can comprise an array of barbs  809  which does not extend to the tip  806  of the leg  804  or the base  802 . In certain embodiments, a leg  804  can comprise more than one array of barbs  809 . 
     Various barb configurations are depicted in  FIGS. 70-73 , although any suitable barb configuration could be utilized. Referring to  FIG. 70 , a staple leg  804  can include at least one barb  809 , for example. In various instances, the barb  809  can comprise a prong. The prong can include a first surface  809   a  and a second surface  809   b  which can extend from the perimeter  805  of the staple leg  804 . The first surface  809   a  can comprise an inclined surface, a convex surface, and/or a concave surface, for example. The second surface  809   b  can comprise a flat, or an at least substantially flat, surface, for example. In various instances, the first surface  809   a  and the second surface  809   b  can converge at an edge  809   c , for example. The barb  809  can be formed utilizing any suitable process. For instance, the barb  809  can be formed utilizing a stamping process. In at least one embodiment, a forming die, for example, can be utilized to strike the perimeter  805  of the wire comprising the leg  804  in order to upset, or disturb, enough material to create the barb  809 . In various instances, a barb can comprise any suitable nib or spur, for example. In various embodiments, the barb  809  can be tapered. In various instances, the barb  809  can include a base adjacent to the perimeter  805  which is thicker than a tip of the barb  809 . 
     Referring now to  FIGS. 68, 69, 71, and 71A , a staple leg  804  can include at least one barb  879 , for example. In at least one embodiment, the barb  879  can extend around a portion of the perimeter  805  of the staple leg  804 . In various instances, the barb  879  can include a first surface  879   a  and a second surface  879   b  which can extend from the perimeter  805  of the staple leg  804 . The first surface  879   a  can comprise an inclined surface, a convex surface, and/or a concave surface, for example. The second surface  879   b  can comprise a flat, or an at least substantially flat, surface, for example. In various instances, the first surface  879   a  and the second surface  879   b  can converge at an edge  879   c , for example. In various instances, the edge  879   c  can be arcuate, for example. The barb  879  can be formed utilizing any suitable process. For instance, the barb  879  can be formed utilizing a stamping process. In at least one embodiment, a forming die, for example, can be utilized to strike the perimeter  805  of the wire comprising the leg  804  in order to upset, or disturb, enough material to create the barb  879 . Referring primarily to  FIG. 71A , the wire comprising the leg  804  can be defined by a diameter  801  and the barb  879  can be defined by a diameter which is larger than the diameter  801 . Correspondingly, the wire comprising the leg  804  can be defined by a radius and the barb  879  can be defined by a radius which is larger than the wire radius. In various embodiments, the barb  879  can be tapered. In various instances, the barb  879  can include a base adjacent to the perimeter  805  which is thicker than a tip of the barb  879 . 
     Referring now to  FIG. 72 , a staple leg  804  can include at least one barb  889 , for example. In at least one embodiment, the barb  889  can extend around the entirety of the perimeter  805  of the staple leg  804 . In various instances, the barb  889  can include a first surface  889   a  and a second surface  889   b  which can extend from the perimeter  805  of the staple leg  804 . The first surface  889   a  can comprise an inclined surface, a convex surface, and/or a concave surface, for example. The second surface  889   b  can comprise a flat, or an at least substantially flat, surface, for example. In various instances, the first surface  889   a  and the second surface  889   b  can converge at an edge  889   c , for example. In various instances, the edge  889   c  can be arcuate, for example. The barb  889  can be formed utilizing any suitable process. For instance, the barb  889  can be formed utilizing a stamping process. In at least one embodiment, a forming die, for example, can be utilized to strike the perimeter  805  of the wire comprising the leg  804  in order to upset, or disturb, enough material to create the barb  889 . The wire comprising the leg  804  can be defined by a wire diameter and the barb  889  can be defined by a diameter which is larger than the wire diameter. Correspondingly, the wire comprising the leg  804  can be defined by a radius and the barb  889  can be defined by a radius which is larger than the wire radius. In various embodiments, the barb  889  can be tapered. In various instances, the barb  889  can include a base adjacent to the perimeter  805  which is thicker than a tip of the barb  889 . 
     Referring now to  FIG. 73 , a staple leg  804  can include at least one barb  899 , for example. In various instances, the barb  899  can comprise a prong. The prong can include a first surface  899   a  and a second surface  899   b  which can extend from the perimeter of the staple leg  804 . The first surface  899   a  can comprise an inclined surface, a convex surface, and/or a concave surface, for example. The second surface  899   b  can comprise a flat, or an at least substantially flat, surface, for example. In various instances, the first surface  899   a  and the second surface  899   b  can converge at an edge  899   c , for example. The barb  899  can be formed utilizing any suitable process. For instance, the barb  899  can be formed utilizing a stamping process. In at least one embodiment, a forming die, for example, can be utilized to strike the perimeter of the wire comprising the leg  804  in order to upset, or disturb, enough material to create the barb  899 . In various embodiments, the wire comprising the staple can include one or more flat sides. In at least one embodiment, the wire can include opposing flat sides  895 , for example. In at least one such embodiment, the flat sides  895  can be formed into a cylindrical wire. In some instances, the wire can retain one or more cylindrical surfaces in addition to the flat sides  895 . In various instances, a barb can comprise any suitable nib or spur, for example. In various embodiments, the barb  899  can be tapered. In various instances, the barb  899  can include a base adjacent to the perimeter of the leg  804  which is thicker than a tip of the barb  899 . 
     In various instances, the legs of a staple can define a staple plane. The base of the staple may or may not be positioned within the staple plane. In either event, one or more barbs extending from the legs and/or the base may extend within and/or extend parallel with respect to the staple plane. In some instances, one or more barbs extending from the legs and/or the base can extend outwardly from the staple plane. One or more barbs extending from the legs and/or the base can extend transversely with respect to the staple plane. In various instances, a barb can extend circumferentially around a staple leg. Such a barb can extend within and outwardly from the staple plane. In some instances, a barb can extend around the entire circumference of a staple leg. In certain instances, the barb can extend less than 360 degrees around a staple leg. A barb extending within a staple plane can readily control tissue within the staple plane. A barb extending outwardly from a staple plane can readily control tissue outside of the staple plane. A staple, and/or a staple leg, can include one or more barbs extending within the staple plane and one or more barbs extending outwardly from the staple plane. 
     Referring again to  FIG. 62 , the barbs extending from a staple leg  804  can be configured to retain the staple leg  804  within tissue. As outline above, the staple legs  804  may be malformed and/or unformed by an anvil in certain instances and, owing to the barb, or barbs, extending therefrom, the staple leg  804  may still be retained in the tissue. In various instances, the barbs can be configured to trap tissue within the tissue entrapment area of the staple. In certain instances, the barbs can be configured to hold the tissue against the base  802 . In such instances, the barbs can apply a compressive force or pressure to the tissue. As discussed above in connection with the embodiments depicted in  FIGS. 70-73 , a barb can comprise an inclined, convex, and/or concave top surface, such as surfaces  809   a ,  879   a ,  889   a , and/or  899   a , for example. The top surfaces of the barbs can be configured to facilitate the insertion of the barbs and the staple legs  804  into and/or through the tissue. As also discussed above in connection with the embodiments depicted in  FIGS. 70-73 , a barb can comprise a flat, or at least substantially flat, bottom surface, such as surfaces  809   b ,  879   b ,  889   b , and/or  899   b , for example. The bottom surfaces of the barbs can be configured to inhibit the removal of the barbs and the staple legs  804  from the tissue. As a result of the above, in certain circumstances, the top surfaces of the barbs can be configured to pierce the tissue while the bottom surfaces of the barbs can be configured to abut the tissue. In various circumstances, the tips  806  of the staple legs  804  can be configured to puncture a hole in the tissue while the staple legs  804  and the barbs extending therefrom can be configured to resiliently expand the hole such that such that the tissue can flow around the barbs as the staple legs  804  are being pushed through the tissue and flow back underneath the bottom surfaces of the barbs. 
     In certain embodiments, a first barb can extend from a first leg  804  of the staple and a second barb can extend from a second leg  804  of the staple. In various instances, the first barb and the second barb can be located the same, or at least substantially the same, distance between from the base  802 . In certain instances, the first barb and the second barb can be located the same, or at least substantially the same, vertical distance from the base  802 . As discussed above, a staple leg  804  can include an array of barbs extending along the length of the staple leg  804 . In various embodiments, referring primarily to  FIG. 62 , a staple can include a first leg  804  including a first array of barbs and a second leg  804  including a second array of barbs wherein the first array of barbs and the second array of barbs can be configured to co-operatively hold the staple within the tissue. In various embodiments, a barb from the first array and a barb from the second array can comprise a pair of barbs configured to engage tissue at the same vertical distance from the base  802 , for example. In various instances, a staple can comprise more than one pair of barbs. In certain instances, each of the barb pairs can be configured to engage the tissue at a different vertical distance from the base  802 . In such circumstances, a staple can be suitable for use with different tissue thicknesses. For instance, when a staple is used to staple thin tissue, one pair of barbs, or less than all of the barb pairs, may engage the thin tissue. If that staple were used to staple thick tissue, however, additional barb pairs, or all of the barb pairs, may engage the tissue. In certain embodiments, the barbs extending from the legs  804  can be arranged in a manner in accordance with the tissue thickness, or range of tissue thicknesses, that can be stapled by the staple. For instance, referring again to  FIG. 62 , the barbs  808  and  809  can be selectively positioned along the legs  804  such that they are positioned within and/or adjacent to the tissue captured within the staple. In certain instances, the portions of the staple legs  804  that are deformed by, or come into contact with, an anvil may not include barbs extending therefrom. In at least some instances, an array of barbs extending from the inwardly-facing side of the staple legs  804  may be longer than an array of barbs extending from the outwardly-facing side of the staple legs  804 . In other instances, an array of barbs extending from the inwardly-facing side of the staple legs  804  may be shorter than an array of barbs extending from the outwardly-facing side of the staple legs  804 . In yet other instances, an array of barbs extending from the inwardly-facing side of the staple legs  804  may be the same length as an array of barbs extending from the outwardly-facing side of the staple legs  804 . 
     As discussed above, the barbs extending from the staple legs  804  can assist in retaining the staple within the tissue if the staple legs  804  are malformed and/or unintentionally unformed. Certain circumstances are contemplated, however, where a staple including one or more of the barbs disclosed herein is inserted into tissue and remains intentionally unformed. In any event, staples including one or more of the barbs disclosed herein can be useful in stapling thick tissue. More particularly, in some instances, the presence of thick and/or dense tissue between a staple cartridge and an anvil and/or the presence of thick and/or dense tissue within a staple may prevent the staple from becoming fully formed or closed. For instance, the staple may not be fully closed into a B-form configuration or the staple may not be closed at all. In such instances, the barbs of the unclosed staples may inhibit or prevent the tissue from being pulled out of the staple, for example. An array of barbs extending along the length of a staple leg may permit the leg to remain retained in the tissue regardless of the thickness of the tissue. 
     Various embodiments are contemplated in which at least one barbed staple, such as barbed staple  800 , for example, are removably stored within a staple cartridge, such as the staple cartridge  22000  illustrated in  FIGS. 10-12 , for example. Certain embodiments are envisioned in which a staple cartridge includes only barbed staples while other embodiments are envisioned which utilize barbed staples and non-barbed staples. For instance, a first row of staples can comprise barbed staples while a second row of staples can comprise non-barbed staples. In some instances, the staples stored within a staple cartridge can have the same, or essentially the same, unformed height. At least with regard to U-shaped and/or V-shaped staples, for example, the unformed height of a staple can be defined as the vertical distance between the bottom of the base of the staple and the tips of the staple legs. Such a measurement can be taken before the staples are inserted into the staple cartridge, when the staples are removably stored within the staple cartridge, and/or before the staples are deformed against the anvil. In some instances, barbed staples arranged in a first row in a staple cartridge can comprise a first unformed height and barbed staples arranged in a second row in the staple cartridge can comprise a second unformed height. Barbed staples in a third row in the staple cartridge can comprise the first unformed height, the second unformed height, or a third unformed height. The first row, the second row, and/or the third row of barbed staples can be positioned on the same side of a knife slot defined in the staple cartridge or on opposite sides of the knife slot. In use, the barbed staples removably stored in a staple cartridge can be formed to the same formed height or different formed heights. The formed height of a staple can be defined as the overall vertical distance of the staple after it has been deformed against an anvil. At least with regard to a staple that has been deformed into a B-form, for example, the formed height of the staple can be measured between the bottom of the base of the staple and the top-most portion of the staple legs. In some instances, barbed staples arranged in a first row in a staple cartridge can be deformed to a first formed height and barbed staples arranged in a second row in the staple cartridge can be deformed to a second formed height. Barbed staples in a third row in the staple cartridge can comprise the first formed height, the second formed height, or a third formed height. The first row, the second row, and/or the third row of barbed staples can be positioned on the same side of a knife slot defined in the staple cartridge or on opposite sides of the staple cartridge. As the reader will appreciate, the staples depicted in  FIGS. 10-12  have been deformed to different formed heights. Barbed staples  800 , for example, could be utilized in staple cartridges and/or stapling instruments which create staple rows having different formed heights. A first row of barbed staples  800  could be deformed to a first formed height and a second row of barbed staples  800  could be deformed to a second formed height. In various instances, a third row of barbed staples  800  could be deformed to a third formed height. In some instances, the barbed staples  800  deformed to different heights can begin with the same, or essentially the same, unformed height. In certain instances, the barbed staples  800  deformed to different formed heights can begin with different unformed heights. Various structures can be utilized to form staples to different formed heights. For instance, movable drivers supporting the staples can support the staples at different distances relative to the anvil. In some instances, the anvil can include staple forming pockets having different depths. In various instances, a staple driver can include a cradle configured to support the base of a staple and push the staple upwardly toward a forming pocket defined in the anvil. The formed height of a staple can be determined by the distance between the bottom surface of the cradle and the top surface of the forming pocket. U.S. Pat. No. 8,317,070, entitled SURGICAL STAPLING DEVICES THAT PRODUCE FORMED STAPLES HAVING DIFFERENT LENGTHS, issued on Nov. 27, 2012, is incorporated by reference in its entirety. In certain instances, the deck of a staple cartridge can include stepped surfaces, as illustrated in  FIG. 1 . A first row of staple cavities can be defined in a first step and a second row of staple cavities can be defined in a second step wherein the first step and the second step can be vertically offset from one another. For instance, the first step can be positioned vertically above, or closer to, the anvil than the second step. In certain instances, a wall can be defined between the first step and the second step. In some instances, the deck of a staple cartridge can comprise a first step, a second step positioned vertically above the first step, and a third step positioned vertically above the second step. Various embodiments are envisioned in which the deck of a staple cartridge includes any suitable number of steps and any suitable number of walls between the steps. A first row of staple cavities can be defined in the first step, a second row of staple cavities can be defined in the second step, and/or a third row of staple cavities can be defined in the third step, for example. The first row of staple cavities can include staples having a first unformed height, the second row of staple cavities can include staples having a second unformed height, and/or the third row of staple cavities can include staples having a third unformed height, for example. Various embodiments are envisioned in which a staple cartridge includes any suitable number of staple rows having different unformed heights. The staples in the first row of staple cavities can be deformed to a first formed height, the staples in the second row of staple cavities can be deformed to a second formed height, and/or the third row of staple cavities can be deformed to a third formed height, for example. Various embodiments are envisioned in which a staple cartridge includes any suitable number of staple rows which are deformed to different formed heights. In addition to or in lieu of having different formed staple heights, an end effector of a stapling instrument can have different tissue gaps. For instance, referring generally to  FIGS. 10 and 11 , a gap can be defined between the cartridge deck surface  22011  of a staple cartridge and the anvil tissue compression surface  10063  of an anvil. This gap can be configured to receive tissue T. This gap can also be configured to receive a tissue thickness compensator; however, a barbed staple may or may not be used with a tissue thickness compensator and the discussion provided with respect to barbed staples can be applicable in either circumstance. In any event, the reader will appreciate that the anvil tissue compression surface  10063  is stepped. The anvil tissue compression surface  10063  comprises a first portion positioned vertically above a second portion. When the anvil and the staple cartridge of an end effector are in a closed condition, as illustrated in  FIG. 11 , a first gap distance is defined between an outer portion of the anvil tissue compression surface  10063  and the cartridge deck surface  22011  and a second, different, gap distance is defined between an inner portion of the anvil tissue compression surface  10063  and the cartridge deck surface  22011 . The first gap distance is illustrated as being larger than the second gap distance, but it is possible for the first gap distance to be shorter than the second gap distance. Tissue compressed between the anvil and the staple cartridge in the shorter gap distance can be compressed more than tissue in the larger gap distance. The barbs of a barbed staple  800 , for example, may engage the tissue differently depending on whether the tissue is positioned within a shorter tissue gap or a larger tissue gap. More particularly, tissue compressed within a shorter tissue gap may seek to re-expand more after it is released from an end effector than tissue compressed within a larger tissue gap and the barbs of a barbed staple may inhibit or resist this re-expansion, depending on their configuration and/or position on the barbs. In other instances, the barbs may be configured and/or positioned so as to not inhibit or resist the re-expansion of the tissue. As the reader will appreciate, anvil tissue compression surface  10063  is stepped and the cartridge deck surface is flat, or at least substantially flat, and, thus, the difference in tissue gaps defined within the end effector is a function of the height of the stepped anvil surfaces. Other embodiments are envisioned. For instance, the anvil tissue compression surface can be flat, or at least substantially flat, and the cartridge deck surface can be stepped. In other instances, the anvil tissue compression surface and the cartridge deck surface can both be stepped. In any event, different gap distances can be defined between the anvil tissue compression surface and the cartridge deck surface. While two gap distances have been illustrated in  FIGS. 10 and 11 , more than two gap distances may be possible, such as three gap distances, for example. With further reference to  FIGS. 10 and 11 , a first longitudinal row of forming pockets can be arranged within a first portion of an end effector having first tissue gap distance and a second longitudinal row of forming pockets can be arranged within a second portion of the end effector having a second tissue gap distance which is different than the first tissue gap distance. In some instances, the end effector can include a third longitudinal row of forming pockets arranged within a third portion of the end effector having a third tissue gap distance which is different than the first tissue gap distance and the second tissue gap distance. In certain instances, the end effector can include a third longitudinal row of forming pockets arranged within a third portion of the end effector having a tissue gap distance which is the same as the first tissue gap distance or the second tissue gap distance. The reader will appreciate that an end effector can have different tissue gap distances and/or different formed staple heights. An end effector can have one, the other, or both. In certain instances, shorter formed staple heights can be associated within shorter tissue gap distances while larger formed staple heights can be associated with larger tissue gap distances. In other instances, shorter formed staple heights can be associated with larger tissue gap distances while larger formed staple heights can be associated with shorter tissue gap distances. Further to the above, a staple can include a U-shape configuration in its unformed state. A U-shape staple can comprise a base and two staple legs extending from the base wherein the staple legs extend in parallel directions to each other. Also further to the above, a staple can include a V-shape configuration in its unformed state. A V-shape configuration can comprise a base and two staple legs extending from the base wherein the staple legs extend in directions which are not parallel. 
     Various embodiments described herein are described in the context of linear end effectors and/or linear fastener cartridges. Such embodiments, and the teachings thereof, can be applied to non-linear end effectors and/or non-linear fastener cartridges, such as, for example, circular and/or contoured end effectors. For example, various end effectors, including non-linear end effectors, are disclosed in U.S. patent application Ser. No. 13/036,647, filed Feb. 28, 2011, entitled SURGICAL STAPLING INSTRUMENT, now U.S. Patent Application Publication No. 2011/0226837, which is hereby incorporated by reference in its entirety. Additionally, U.S. patent application Ser. No. 12/893,461, filed Sep. 29, 2012, entitled STAPLE CARTRIDGE, now U.S. Patent Application Publication No. 2012/0074198, is hereby incorporated by reference in its entirety. U.S. patent application Ser. No. 12/031,873, filed Feb. 15, 2008, entitled END EFFECTORS FOR A SURGICAL CUTTING AND STAPLING INSTRUMENT, now U.S. Pat. No. 7,980,443, is also hereby incorporated by reference in its entirety. The entire disclosure of U.S. Pat. No. 7,845,537, entitled SURGICAL INSTRUMENT HAVING RECORDING CAPABILITIES, which issued on Dec. 7, 2010, is incorporated by reference herein. The entire disclosure of U.S. application Ser. No. 13/118,241, entitled SURGICAL STAPLING INSTRUMENTS WITH ROTATABLE STAPLE DEPLOYMENT ARRANGEMENTS, now U.S. Patent Application Publication No. 2012/0298719, which was filed on May 27, 2011, is incorporated by reference herein. 
     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. 
     Preferably, the invention described herein will be processed before surgery. First, a new or used instrument is obtained and if necessary cleaned. The instrument can then be sterilized. In one sterilization technique, the instrument is placed in a closed and sealed container, such as a plastic or TYVEK bag. The container and instrument are then placed in a field of radiation that can penetrate the container, such as gamma radiation, x-rays, or high-energy electrons. The radiation kills bacteria on the instrument and in the container. The sterilized instrument can then be stored in the sterile container. The sealed container keeps the instrument sterile until it is opened in the medical facility. 
     Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated materials does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material. 
     While this invention has been described as having exemplary designs, the present invention may be further modified within the spirit and scope of the disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.