Patent Publication Number: US-8113407-B2

Title: Surgical stapling instruments including a cartridge having multiple staples sizes

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 12/176,784 filed Jul. 21, 2008, now U.S. Pat. No. 7,828,189, which is a divisional of U.S. application Ser. No. 11/436,222 filed May 18, 2006, now U.S. Pat. No. 7,401,721, which is a continuation in part of U.S. application of Ser. No. 11/204,060 filed Aug. 15, 2005, now U.S. Pat. No. 7,407,075, and the disclosures of each of the above-identified applications are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to surgical stapling instruments and, more particularly, to surgical stapling instruments including a cartridge having multiple staple sizes. 
     2. Background of Related Art 
     There are several known types of surgical stapling instruments specifically adapted for use in various procedures such as end-to-end anastomosis, gastrointestinal anastomosis, endoscopic gastrointestinal anastomosis, and transverse anastomosis. Examples of stapling instruments for these various procedures can be found in U.S. Pat. Nos. 5,915,616; 6,202,914; 5,865,361; and 5,964,394. 
     Each surgical stapling instrument includes an anvil which is approximated relative to a staple cartridge. The staple cartridge typically has one or more laterally spaced rows of staples which, depending on the particular stapling instrument, may be arranged in a linear or non-linear configuration. The anvil includes staple forming depressions which are aligned with and/or in registration with the staple slots of the staples in the cartridge. In use, each of the surgical stapling instruments involves the gripping of tissue to be fastened, the ejecting of individual staples, the forcing of staples through the gripped tissue and the closing and/or forming of the staples against the staple forming depressions of the anvil. 
     A common issue in transecting tissue and/or in anastomosis procedures, employing any one of the surgical stapling instruments disclosed above, is the balance between anastomotic strength and the degree of hemostasis achievable. It is known to include different size staples in a surgical stapling apparatus having a constant gap (i.e. a uniform distance) between an anvil and a staple cartridge. 
     SUMMARY 
     The present disclosure is directed towards surgical stapling instruments configured to effectuate an improved balance between the anastomotic strength and the degree of hemostasis at the tissue interface. In particular, embodiments of the present disclosure include surgical fasteners of different sizes. Further still, the distance between an anvil member and a staple cartridge (i.e. the gap) varies from a centerline of the staple cartridge to an outer edge of the staple cartridge. Preferably, the gap is greater at the outer edge of the cartridge in comparison to the gap at the centerline. This can be achieved by either varying the contour (i.e. profile) of the staple cartridge and/or the anvil member. Combining the different sizes of surgical fasteners with the varying gap between the anvil member and the staple cartridge improves the anastomotic strength and the degree of hemostasis at the tissue interface. 
     According to one aspect of the disclosure, the surgical stapling instrument includes a first structure defining having an anvil member operatively associated therewith, and a second structure defining a staple cartridge operatively associated therewith. The staple cartridge has a tissue contacting surface with a stepped cross-sectional profile. The tissue contacting surface of the staple cartridge also includes a plurality of retention slots formed therein for retaining a surgical fastener. During operation of the surgical stapling instrument, the anvil member and the staple cartridge can be approximated relative to one another. 
     The stepped tissue contact surface of the staple cartridge defines a plurality of tissue contacting surfaces each having a different height. In one embodiment, the stepped tissue contacting surface of the cartridge includes an inner tissue contacting surface having a height, an intermediate tissue contacting surface having a height less than the height of the inner tissue contacting surface, and an outer tissue contacting surface having a height less than the height of the intermediate tissue contacting surface. 
     The inner, intermediate, and outer tissue contacting surfaces each include at least one row of retention slots formed therein. A plurality of surgical fasteners is disposed, one each, in each retention slot. Each surgical fastener includes a backspan and a pair of descending legs. 
     The surgical fasteners retained in the retention slots formed in the inner tissue contacting surface have a first leg length, the surgical fasteners retained in the retention slots formed in the intermediate tissue contacting surface have a second leg length, and the surgical fasteners retained in the retention slots formed in the outer tissue contacting surface have a third leg length. In one embodiment, the surgical fasteners retained in the retention slots formed in the inner tissue contacting surface have a leg length of about 2.3 mm, while the surgical fasteners retained in the retention slots formed in the intermediate tissue contacting surface have a leg length of about 3.5 mm, and the surgical fasteners retained in the retention slots formed in the outer tissue contacting surface have a leg length of about 4.1 mm. 
     It is envisioned that the surgical stapling instrument can be a circular-type surgical stapling instrument wherein the anvil member and the staple cartridge can be annular. In one embodiment, the plurality of tissue contacting surfaces decreases in height in a radially outward direction. Accordingly, the inner tissue contacting surface is closest to the center and the outer tissue contacting surface is furthest from the center of the annular staple cartridge. Moreover, surgical fasteners having relatively short leg lengths are retained in the retention slots closest to the center of the annular staple cartridge while surgical fasteners having relatively longer leg lengths are retained in the retention slots furthest from the center of the annular staple cartridge. 
     It is further envisioned that the surgical stapling instrument can be a linear-type surgical stapling instrument wherein the anvil member and the staple cartridge are linear. In these instruments, the staple cartridge and/or the anvil member may define a knife cut line. Accordingly, the plurality of tissue contacting surfaces decreases in height in a direction orthogonally outward from the knife cut line. In particular, the inner tissue contacting surface is closest to the knife cut line while the outer tissue contacting surface is furthest from the knife cut line. In addition, surgical fasteners having relatively short leg lengths are retained in the retention slots closest to the knife cut line while surgical fasteners having relatively longer leg lengths are retained in the retention slots furthest from the knife cut line. 
     It is envisioned that the anvil member can have a tissue contacting surface with a stepped cross-sectional profile including a plurality of tissue contacting surfaces, wherein each tissue contacting surface has a different height. In addition, each one of the plurality of tissue contacting surfaces can include at least one annular and/or linear row of surgical fastener forming depressions formed therein. 
     In one embodiment, the anvil member can have a tissue contacting surface which is shaped (i.e. stepped) to complement the stepped tissue contacting surface of the staple cartridge. In another embodiment, the anvil member can have a tissue contacting surface which is stepped while the tissue contacting surface of the staple cartridge is substantially planar. In yet another embodiment, the anvil member can have a tissue contacting surface which is shaped to substantially complement the stepped tissue contacting surface of the staple cartridge (i.e. the depths of the tissue contacting surfaces of the stepped anvil member are not equal to the heights of the individual tissue contacting surfaces of the tissue contacting surface of the staple cartridge). In still another embodiment, the anvil member can have a tissue contacting surface which is stepped to mirror the tissue contacting surface of the staple cartridge (i.e. the depths of individual tissue contacting surfaces of the tissue contacting surface of the anvil member are substantially equal to the depths of the individual tissue contacting surfaces of the staple cartridge). 
     In other embodiments of the present disclosure, a surgical stapling instrument includes an operative tool disposed at one end thereof. The operative tool includes an anvil member and a staple cartridge. The staple cartridge may be included in a disposable surgical stapling apparatus or in a reusable surgical stapling apparatus. Further still, a replaceable loading unit may be located in either the disposable or the reusable surgical stapling apparatus. In one embodiment, the replaceable loading unit includes a staple cartridge, while an alternate embodiment of the replaceable loading unit includes a staple cartridge and an anvil member. In particular, the staple cartridge includes a plurality of surgical fasteners disposed in rows of retention slots. The surgical fasteners may have different leg lengths wherein a plurality of surgical fasteners having substantially the same leg length is disposed in a row. A number of fastener ejection members are disposed in the staple cartridge wherein each fastener ejection member includes a plurality of staple pushers for ejecting the surgical fasteners in cooperation with an actuation mechanism. The staple pushers of the fastener ejection member each have a shape that generally corresponds to the shape of the staple pockets of the anvil member and the retention slots of the staple cartridge. 
     The staple cartridge may include an angled tissue contacting surface that peaks at a centerline of the staple cartridge and tapers towards outer walls of the staple cartridge. Alternatively, the tissue contacting surface of the staple cartridge may have a surface that is parallel with the bottom surface of the staple cartridge or parallel to a plane defined by the backspans of surgical fasteners disposed in a selected row. The parallel surface of the tissue contacting surface has a width dimension that is sufficient to accommodate at least one row of surgical fasteners. The staple cartridge may include a knife channel. 
     In cooperation with the presently disclosed staple cartridge, the anvil member may include a planar tissue contacting surface that is substantially parallel to the bottom surface of the staple cartridge or parallel to a plane defined by the backspans of surgical fasteners disposed in a selected row. In the alternative, the tissue contacting surface of the anvil member may be angled in an opposed manner to the angle of the tissue contacting surface of the staple cartridge. Further still, the tissue contacting surface of the anvil member may have a planar surface that is substantially parallel to the bottom surface of the staple cartridge or parallel to a plane defined by the backspans of surgical fasteners disposed in a selected row and tapered surfaces that define angles opposite to the angles defined by the tissue contacting surface of the staple cartridge. The parallel surfaces of the anvil member have a width dimension that corresponds to a width dimension of the parallel surface of the staple cartridge. 
     It is further contemplated that one embodiment of the surgical stapling apparatus includes structures for supplemental sealing of the fastened layers of tissue. In one embodiment, the surgical stapling apparatus includes a wound closure assembly having a reservoir and a supply line. The reservoir is adapted for storing a quantity of a wound closure material and is fluidly coupled to the staple cartridge via the supply line for delivering amounts of the wound closure material to the plurality of retention slots. 
     In yet another embodiment of the presently disclosed surgical stapling apparatus, the staple cartridge may include a planar surface proximate a centerline of the staple cartridge and an arcuate surface adjacent to the planar surface. The arcuate surface extends outwards from the centerline and downwards towards the base of the staple cartridge defining a concave configuration with respect to the base of the staple cartridge. Each of the surfaces includes at least one row of retention slots and defines a tissue contacting surface. In addition, this embodiment of the staple cartridge includes a plurality fastener ejection members and a plurality of surgical fasteners. Tips of the unfired surgical fasteners may be positioned beneath the arcuate and planar surfaces or may extend into the retention slots wherein the tips are substantially flush with the tissue contacting surface. This embodiment of the staple cartridge may be combined with an anvil member having a planar tissue contacting surface that cooperates with the tissue contacting surface of the staple cartridge to position layers of tissue therebetween and form completed surgical fasteners. Alternatively, an anvil member may have a planar surface corresponding in width to the planar surface of the staple cartridge and curvate surfaces that have the same curvature as the arcuate surfaces of the staple cartridge in an opposed direction. The staple cartridge may include a knife channel that is located along the centerline of the staple cartridge. 
     In a further embodiment of the presently disclosed surgical stapling apparatus, the staple cartridge may include first and second planar surfaces, wherein each planar surface includes at least one row of retention slots. The first and second planar surfaces are substantially parallel with a bottom surface of the staple cartridge and with each other, but are vertically spaced apart such that there are not coplanar with each other. As in the previous embodiments, the staple cartridge includes a plurality of fastener ejection members and a plurality of surgical fasteners. A first gap is defined between a planar tissue contacting surface of an anvil member and the first planar surface of the staple cartridge and a second gap is defined between the planar tissue contacting surface of the anvil member and the second planar surface. The staple cartridge may include a knife channel that is located along the centerline of the staple cartridge. Alternatively, an anvil member having a complementary surface configuration may be used in combination with the staple cartridge, wherein the spacing between the second planar surface of the staple cartridge and a corresponding surface of the anvil member defines a gap that is greater than the second gap. 
     In a further embodiment of the presently disclosed surgical stapling apparatus, a staple cartridge is provided having a plurality of fastener ejection members and a plurality of surgical fasteners. The staple cartridge includes a planar surface opposed to a bottom surface. A filler layer is positioned atop the planar surface. The filler layer may be formed from a buttress material. The filler layer is generally triangular in shape and extends downwards and outwards from a centerline of the staple cartridge such that its maximum height is proximate to the centerline. An anvil member having a planar surface may be used in cooperation with the staple cartridge for forming completed surgical fasteners. Alternatively, an anvil member having a tapered (i.e. angled) surface that complements the filler layer may be used. The staple cartridge may include a knife channel. 
     An alternate embodiment of the presently disclosed surgical stapling apparatus includes a staple cartridge and an anvil member. The staple cartridge includes a plurality of surgical fasteners and a plurality of fastener ejection members. A top plate extends between inner and outer walls of the staple cartridge and is a planar structure that is substantially parallel to a bottom surface of the staple cartridge. A vertical member abuts the inner wall. Vertically spaced from the top plate is a cross member that is flexibly attached to the vertical member. A top surface of the cross member defines a tissue contacting surface in opposition to a tissue contacting surface of the anvil member. During approximation and/or formation of surgical fasteners, the cross member flexes such that the gap between the tissue contacting surfaces is at a minimum near the centerline of the staple cartridge and a maximum near the outer wall of the staple cartridge. The staple cartridge may include a knife channel. Alternatively, the anvil member may include tapered surfaces that define the tissue contacting surface, wherein the tapered surfaces extend outwards and upwards from the centerline of the staple cartridge such that the anvil member has its maximum thickness near the centerline and its minimum thickness near outer edges of the anvil member. 
     All of the presently disclosed embodiments of the surgical stapling instrument provide a variable pressure gradient (i.e. load profile) to the layers of tissue that are joined together with the surgical fasteners. Therefore, the layers of tissue that are proximate to the center of the surgical stapling instrument (i.e. center of the staple cartridge) are subjected to higher compressive forces (i.e. loads), thereby forming thinner layers of tissue as compared to layers of tissue that are further away from the center of the surgical stapling instrument. Since the layers of tissue nearest the center of the surgical stapling instrument can be compressed more, a smaller sized surgical staple or fastener can be used to mechanically suture (i.e. fasten) the transected layers of tissue. Further still, providing a gradual compression gradient to the layers of tissue to be joined, may result in a higher degree of hemostasis. Due to the contoured shape of the staple cartridge, the layers of tissue can be compressed more at the center of the surgical stapling instrument, because the layers of tissue can translate (i.e. move) from a region of relatively high pressure (i.e. at the center) to a region of relatively low pressure (i.e. at the edges) as the anvil member is moved relative to the staple cartridge, thereby defining the pressure gradient. 
     The presently disclosed surgical stapling instruments, together with attendant advantages, will be more clearly illustrated below by the description of the drawings and the detailed description of the embodiments. 
     Other objects and features of the present disclosure will become apparent from consideration of the following description taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the presently disclosed surgical stapling apparatus are described herein with reference to the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a surgical stapling instrument constructed in accordance with the present disclosure; 
         FIG. 2  is a schematic cross-sectional side elevational view of the distal end portion of the surgical stapling instrument of  FIG. 1 , as taken through  2 - 2  of  FIG. 1 ; 
         FIG. 2A  is a perspective view of a surgical fastener in accordance with an embodiment of the present disclosure; 
         FIG. 3A  is an enlarged schematic representation of the indicated area of  FIG. 2 , illustrating tissue contacting surfaces in accordance with an alternate embodiment of the present disclosure; 
         FIG. 3B  is an enlarged schematic representation of the indicated area of  FIG. 2 , illustrating tissue contacting surfaces in accordance with another embodiment of the present disclosure; 
         FIG. 3C  is an enlarged schematic representation of the indicated area of  FIG. 2 , illustrating tissue contacting surfaces in accordance with still another embodiment of the present disclosure; 
         FIG. 3D  is an enlarged schematic representation of the indicated area of  FIG. 2 , illustrating tissue contacting surfaces in accordance with a further embodiment of the present disclosure; 
         FIG. 4  is a perspective view of an alternative surgical stapling instrument constructed in accordance with the present disclosure; 
         FIG. 5  is a perspective view of yet another surgical stapling instrument constructed in accordance with the present disclosure; 
         FIG. 6  is a perspective view of still another surgical stapling instrument constructed in accordance with the present disclosure; 
         FIG. 6A  is a perspective view of a portion of an anvil member of  FIG. 6 ; 
         FIG. 7  is a schematic cross-sectional side elevational view of the distal end portion of the surgical stapling instruments of  FIGS. 4-6 , as taken through  7 - 7  of each of  FIGS. 4-6 ; 
         FIG. 7A  is a schematic cross-sectional side elevational view of an alternate embodiment of the distal portion of the surgical stapling instrument of  FIG. 6   
         FIG. 8  is a perspective view of a staple cartridge according to another embodiment of the present disclosure; 
         FIG. 9A  is a cross-sectional end view of the staple cartridge of  FIG. 8  showing a first arrangement of surgical fasteners; 
         FIG. 9B  is a cross-sectional end view of the staple cartridge of  FIG. 8  showing a second arrangement of surgical fasteners; 
         FIG. 9C  is an alternate embodiment of the staple cartridge of  FIG. 8  showing a second arrangement of surgical fasteners and an alternate embodiment of an anvil member; 
         FIG. 10  is an alternate embodiment of the staple cartridge of  FIG. 9A  illustrating a second embodiment of the surgical fasteners; 
         FIG. 11  is an alternate embodiment of an anvil member and the staple cartridge of  FIG. 10 ; 
         FIG. 12  is a further embodiment of the staple cartridge of  FIG. 8 ; 
         FIG. 13  is another embodiment of the anvil member and the staple cartridge of  FIG. 12 ; 
         FIG. 14  is another embodiment of the staple cartridge and anvil member of  FIG. 8 ; 
         FIG. 15  is alternate embodiment of an anvil member with the staple cartridge of  FIG. 14 ; 
         FIG. 16A  is a cross-sectional side elevation view of a tissue interface following the firing of a conventional surgical stapling instrument; 
         FIG. 16B  is a cross-sectional side elevational view of the resulting tissue interface following the firing of surgical stapling instrument of FIGS.  7  and  10 - 15 ; 
         FIG. 17A  is a cross-sectional end view of another embodiment of the staple cartridge of  FIG. 8  showing a first arrangement of surgical fasteners; 
         FIG. 17B  is an alternate embodiment of the staple cartridge of  FIG. 17A  showing a second arrangement of surgical fasteners; 
         FIG. 17C  is an alternate embodiment of an anvil member and the staple cartridge of  FIG. 17A ; 
         FIG. 17D  is an alternate embodiment of an anvil member and the staple cartridge of  FIG. 17B ; 
         FIG. 17E  is a further embodiment of the staple cartridge of  FIG. 17A ; 
         FIG. 17F  is an alternate embodiment of an anvil member and the staple cartridge of  FIG. 17E ; 
         FIG. 18A  is a cross-sectional end view of a further embodiment of the staple cartridge of  FIG. 8 ; 
         FIG. 18B  is an alternate embodiment of an anvil member and the staple cartridge of  FIG. 18A ; 
         FIG. 19A  is a cross-sectional end view of a further embodiment of the staple cartridge of  FIG. 8  illustrating a shaped support member disposed on a tissue contacting surface of the staple cartridge and a shaped support member, in phantom, disposed on a tissue contacting surface of the anvil member; 
         FIG. 19B  is an alternate embodiment of an anvil member and the staple cartridge of  FIG. 19A ; 
         FIG. 20A  is a cross-sectional end view of another embodiment of the staple cartridge of  FIG. 7A ; 
         FIG. 20B  is a cross-sectional end view of an alternate embodiment of an anvil member and the staple cartridge of  FIG. 20A ; 
         FIG. 20C  is a further embodiment of an anvil member and the staple cartridge of  FIG. 20B ; 
         FIG. 21A  is a cross-sectional end view of another embodiment of the staple cartridge of  FIG. 8 ; 
         FIG. 21B  is another embodiment of an anvil member and the staple cartridge of  FIG. 21B ; 
         FIG. 22A  is a cross-sectional end view of a further embodiment of the staple cartridge of  FIG. 8  and a further embodiment of an anvil member; 
         FIG. 22B  is an alternate embodiment of the staple cartridge and the anvil member of  FIG. 22A ; and 
         FIG. 22C  is a further embodiment of an anvil member with the staple cartridge of  FIG. 22B . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the presently disclosed surgical stapling instruments will now be described in detail with reference to the drawing figures wherein like reference numerals identify similar or identical elements. In the drawings and in the description which follows, the term “proximal”, as is traditional, will refer to the end of the surgical stapling instrument which is closest to the operator while the term “distal” will refer to the end of the device which is furthest from the operator. 
     The present disclosure relates to a staple cartridge and an anvil member for use in a disposable or re-usable surgical stapling apparatus. The presently disclosed staple cartridge and anvil member, as will be discussed in detail hereinbelow, may be used with any of the surgical stapling apparatus shown in  FIG. 1 ,  4 ,  5 , or  6 . In addition, a replaceable loading unit may be located in either the disposable or the reusable surgical stapling apparatus. In one embodiment, the replaceable loading unit includes a staple cartridge, including any of the staple cartridges disclosed herein. Alternatively, the replaceable loading unit includes the staple cartridge and an anvil member, including any of the anvil members disclosed herein. In combination with the disposable or the reusable surgical stapling apparatus, the replaceable loading unit provides improved flexibility of the respective surgical stapling apparatus in that the respective surgical stapling apparatus is readily adaptable for different stapling procedures. In each of the embodiments that are hereinafter disclosed, staples or surgical fasteners disposed the staple cartridge are arranged such that tips of the surgical fasteners may be substantially flush with a tissue contacting surface of the staple cartridge. Alternately, the tips of the surgical fasteners may be located above or below the tissue contacting surface. 
     Referring now in detail to  FIGS. 1-2 , in which like reference numerals identify similar or identical elements, a surgical stapling instrument, in accordance with a first embodiment of the disclosure, is generally designated as  100 . 
     As seen in  FIG. 1 , surgical stapling instrument  100  includes a handle assembly  102  having at least one pivotable actuating handle member  103 , and further includes advancing means  105 . Extending from handle assembly  102 , there is provided a tubular body portion  104  which may be constructed so as to have a curved shape along its length. Tubular body portion  104  terminates in a fastener ejection member assembly  106  having a circular staple cartridge  118  including a tissue contacting surface  121  disposed at a distal end thereof. An anvil shaft  110  operatively couples an anvil assembly  108  to handle assembly  102 . Anvil assembly  108  is repositionable from a location where it is in close cooperative alignment with staple cartridge  118  to a location where it is spaced apart from staple cartridge  118 . Anvil assembly  108  includes an anvil head  109 . Further still, surgical stapling instrument  100  may include a wound closure assembly  50 . Wound closure assembly  50  includes at least one storage device or reservoir  52  and at least one supply line  54 . Supply line  54  fluidly couples reservoir  52  to anvil shaft  110 , wherein anvil shaft includes at least one opening  56  for dispensing wound closure material “W”. By providing wound closure material “W” in combination with surgical fasteners, the bond formed between the layers of tissue has improved strength. 
     As seen in  FIG. 2 , tissue contacting surface  121  is stepped including an outer tissue contacting surface  121   a , an intermediate tissue contacting surface  121   b , and an inner tissue contacting surface  121   c . Each tissue contacting surface  121   a - 121   c  has a different height from one another as measured from a point  131  on a bottom surface of a staple pusher or fastener ejection member  130 . Point  131  is proximal to a shaft  111  in a region where the bottom surface of fastener ejection member  130  is substantially planar. Specifically, tissue contacting surfaces  121   a - 121   c  are planar structures that are substantially parallel to one another, but are not co-planar (i.e. stepped) with one another. In addition, each tissue contacting surface  121   a - c  defines a planar axis that extends through the respective tissue contacting surface  121   a - c . A first wall surface interconnects tissue contacting surfaces  121   a  and  121   b , while a second wall surface interconnects tissue contacting surfaces  121   b  and  121   c . The first and second wall surfaces are planar structures wherein each wall surface defines a planar axis. In one embodiment, the planar axes of the wall surfaces are orthogonal to the planar axes of tissue contacting surfaces  121   a - c.    
     Inner tissue contacting surface  121   c  has the greatest height, outer tissue contacting surface  121   a  has the least height, and intermediate tissue contacting surface  121   b  has a height between the heights of outer and inner tissue contacting surfaces  121   a ,  121   c . While tissue contacting surfaces  121   a - 121   c  are shown as increasing in height from outer tissue contacting surface  121   a  to inner tissue contacting surface  121   c  (i.e. radially inward), it is within the scope of the present disclosure that the heights of each tissue contacting surface can vary depending on the particular surgical procedure. For example, tissue contacting surfaces  121   a - 121   c  can increase in height in a radially outward direction, the intermediate tissue contacting surface  121   b  can be the highest or the lowest tissue contacting surface, or at least two of tissue contacting surfaces  121   a - 121   c  can have the same height. 
     In one embodiment, each tissue contacting surface  121   a - 121   c  includes a respective annular row  119   a - 119   c  of retention slots  123  formed therein. Each retention slot  123  of annular rows  119   a - 119   c  is configured and dimensioned to retain a staple or surgical fastener  125  therein. As shown in  FIG. 2A , each surgical fastener  125  includes a backspan  27  and a pair of depending legs  25 . Each leg  25  forms a right angle in relation to backspan  27 . In one embodiment, each annular row  119   a - 119   c  of slots  123  includes a respective surgical fastener  125   a - 125   c  having its own characteristic features. 
     As seen in  FIG. 2 , legs  25   a  of surgical fasteners  125   a  have a first leg length, legs  25   b  of surgical fasteners  125   b  have a second leg length, and legs  25   c  of surgical fasteners  125   c  have a third leg length. In particular, surgical fasteners  125   a - 125   c  increase in height in a radially outward direction. In one embodiment, legs  25   c  of surgical fasteners  125   c  have a leg length of about 2.3 mm, legs  25   b  of surgical fasteners  125   b  have a leg length of about 3.5 mm, and legs  25   a  of surgical fasteners  125   a  have a leg length of about 4.1 mm. As such, inner tissue contacting surface  121   c  has the greatest height and retains surgical fasteners  125   c  having the shortest leg lengths, and outer tissue contacting surface  121   a  has the least height and retains surgical fasteners  125   a  having the longest leg lengths. Having tissue contacting surface  121  step progressively downward at intermediate tissue contacting surface  121   b  and then again at outer tissue contacting surface  121   a  results in the formation of surgical fasteners  125   b  and  125   c , respectively. It is envisioned and within the scope of the present disclosure that any number of arrangements are possible. 
     While a single annular row  119   a - 119   c  of retention slots  123  is shown for each tissue contacting surface  121   a - 121   c , it is envisioned and within the scope of the present disclosure that each tissue contacting surface  121   a - 121   c  can include multiple annular rows of retention slots. 
     As seen in  FIG. 2 , a fastener ejection assembly  106  of surgical stapling instrument  100  includes fastener ejection member  130  disposed within staple cartridge  118 . Fastener ejection member  130  includes a proximal portion  132  having a generally frusto-conical shape and a distal portion defining concentric rings of peripherally spaced staple pushers  134   a - c , each one of which is received within a respective staple retention slot  123  and is cooperative with its respective surgical fastener  125   a - c  disposed in annular rows  119   a - c . In one embodiment, it is envisioned that proximal portion  132  of fastener ejection member  130  is configured and dimensioned to be contacted by a distal end of a driver tube  138 . Hence, upon advancing fastener ejection member  130  by advancing driver tube  138 , staple pushers  134   a - c  will pass further into retention slots  123  thereby pushing surgical fasteners  125  contained therein axially outward. 
     In an alternate embodiment, staple pushers  134   a - c  of fastener ejection member  130  have different heights for cooperating with different sized surgical fasteners. In particular, staple pushers  134   a - c  are sized such that when surgical fasteners  125   a - c  are disposed in their respective annular rows  119   a - c , tips of surgical fasteners  125   a - c  are located substantially in the same plane despite the difference in leg lengths between each row of surgical fasteners. 
     Surgical stapling instrument  100  ( FIG. 1 ) includes circular anvil assembly  108  having anvil head  109  and anvil shaft  110  extending from a proximal end thereof and adapted to engage shaft  111  extending distally from staple cartridge  118 . Anvil head  109  includes an annular anvil member  112  disposed at a proximal end thereof, wherein anvil member  112  includes at least one, row of fastener forming depressions  114  formed circumferentially thereabout. In one embodiment, surgical stapling instrument  100  includes three laterally spaced rows of fastener forming depressions  114  formed circumferentially thereabout. Each fastener forming depression  114  is in registration with a corresponding retention slot  123 . 
     While anvil member  112  is shown in  FIG. 2  as having a substantially planar tissue contacting surface, it is envisioned and within the scope of the present disclosure for surgical stapling instrument  100  to have a number of alternate configurations. For example, as seen in  FIG. 3A , anvil member  112   a  can have a tissue contacting surface, including surfaces  116   a - 116   c , which is shaped (i.e. stepped) to complement stepped tissue contacting surface  121  of staple cartridge  118  or, as seen in  FIG. 3B , anvil member  112   b  can have a tissue contacting surface, including surfaces  116   a - c , which is stepped while tissue contacting surface  121  of staple cartridge  118  is substantially planar. In addition, for example, as seen in  FIG. 3C , anvil member  112   c  can have one row of staple pockets  114   b  that extends a greater distance than staple pockets  114   a  or  114   c  into anvil member  112   c  for accommodating surgical fasteners having a longer leg length or, as seen in  FIG. 3D , anvil member  112   d  can have a tissue contacting surface, including surfaces  116   a - c , which is stepped to mirror tissue contacting surface  121  of staple cartridge  118  (i.e. the depths of individual tissue contacting surfaces of the tissue contacting surface of anvil member  112   d  are substantially equal to the depths of the individual tissue contacting surfaces  121   a - 121   c  of staple cartridge  118 ). 
     The sizes of surgical fasteners  125   a - 125   c  are selected and intended for use in gastric firings typically required in bariatric procedures. However, it is envisioned and within the scope of the present disclosure that the sizes of surgical fasteners  125   a - 125   c  selected can be chosen for performance in different types of tissue, such as, for example, the colon, bowels, lungs, the bronchus, pulmonary vessels, the liver, and the like. 
     In operation, surgical stapling instrument  100  is positioned within a tubular organ in the body of the patient and the ends of the organ to be joined are positioned in a gap between staple cartridge  118  and anvil assembly  108 . As is conventional, the ends of the organ may be secured around anvil shaft  110  by a purse string suture prior to approximation of anvil assembly  108  to staple cartridge  118 . Surgical stapling instrument  100  is then approximated and fired. An example of a surgical stapling apparatus and methods for its use are disclosed in U.S. Pat. No. 5,915,616, currently assigned to Tyco Healthcare Group LP, the entire contents of which is incorporated herein by reference. 
     Turning now to  FIGS. 4 and 7 , a surgical stapling instrument, of the gastro-intestinal anastomosis type for performing surgical anastomotic stapling, in accordance with another embodiment of the disclosure, is generally designated as  200 . Surgical stapling instrument  200  includes a first handle  202  having a jaw  203  defining a staple cartridge receiving section extending from a distal end thereof, a staple cartridge  204  receivable in jaw  203 , a second handle  206  having a jaw  205  defining an anvil member receiving section extending from a distal end thereof, and an anvil member  208  operatively associated with jaw  205 . First and second handles  202 ,  206  are configured such that staple cartridge  204  is substantially aligned with anvil member  208 . 
     As seen in  FIG. 7 , staple cartridge  204  includes a stepped tissue contacting surface  121  including an outer tissue contacting surface  121   a , an intermediate tissue contacting surface  121   b , and an inner tissue contacting surface  121   c , each of which has a different height from one another as measured from a point  231  that is located on a bottom surface of staple cartridge  204 , wherein point  231  exists along a centerline of staple cartridge  204 . Tissue contacting surfaces  121   a - 121   c  are planar structures that are substantially parallel to one another, but are not co-planar with one another. For example, tissue contacting surfaces  121   a - 121   c , as shown in  FIG. 7 , can decrease in height in a direction orthogonally outward from knife track  222 . In embodiments that do not include knife track  222 , tissue contacting surfaces  121   a - c  decrease in height in a direction orthogonally outward from a centerline of staple cartridge  204 . 
     Each tissue contacting surface  121   a - 121   c  includes a respective linear row  119   a - 119   c  of retention slots  123  formed therein. Each retention slot  123  of linear rows  119   a - 119   c  is configured and dimensioned to retain a surgical fastener  125  therein. Each linear row  119   a - 119   c  of slots  123  includes a respective surgical fastener  125   a - 125   c  having its own characteristic features. 
     As seen in  FIG. 7 , legs  25   a  of surgical fasteners  125   a  have a first leg length of about 4.1 mm, legs  25   b  of surgical fasteners  125   b  have a second leg length of about 3.5 mm, and legs  25   c  of surgical fasteners  125   c  have a third leg length of about 2.3 mm. In particular, surgical fasteners  125   a - 125   c  increase in height in an orthogonally outward direction relative towards optional knife track  222 . Knife track  222  is disposed along a centerline of staple cartridge  204 ,  310 , or  412  and is adapted for slidably receiving an optional knife (not shown). Having tissue contacting surface  121  step progressively downward at intermediate tissue contacting surface  121   b  and then again at outer tissue contacting surface  121   a  results in the formation of surgical fasteners  125   b  and  125   c , respectively. It is envisioned and within the scope of the present disclosure that any number of arrangements are possible. 
     In operation, surgical stapling instrument  200  is fired similarly to and in accordance with other known surgical stapling instruments. An example of a surgical stapling apparatus and methods for its use are is disclosed in U.S. Pat. No. 6,202,914, currently assigned to Tyco Healthcare Group LP, the entire contents of which is incorporated herein by reference. 
     Referring additionally to  FIG. 16B , following the firing of surgical stapling instrument  200 , the resulting tissue interface is seen in cross-section. Accordingly, some or all of surgical fasteners  125   a - 125   c  serve to hold tissues “A” and “B” to one another while surgical fasteners  125   c  also provide the hemostasis. 
     While surgical stapling instrument  200  is a linear-type surgical stapler, it is envisioned and within the scope of the present disclosure, that surgical stapling instrument  200  can include a tissue contacting surface having a cross-sectional profile for at least one of the anvil member and the staple cartridge which is substantially similar to the tissue contacting surfaces of the anvil member and the staple cartridge of surgical stapling instrument  100 , as shown in  FIGS. 3A-3D . 
     Turning now to  FIGS. 5 and 7 , a surgical stapling instrument, of the laparoscopic type for performing surgical anastomotic stapling, in accordance with another embodiment of the disclosure, is generally designated as  300 . Surgical stapling instrument  300  includes a handle  302 , an operative tool  306 , and an elongated shaft  304  for interconnecting operative tool  306  to handle  302 . In general, operative tool  306  is designed to clamp over and then to staple and divide tissue held therein. Accordingly, as seen in  FIG. 5 , operative tool  306  is a pair of opposed jaws including an anvil member  308  and a staple cartridge  310  pivotally coupled to one another. 
     Staple cartridge  310  of surgical stapling instrument  300  includes a stepped tissue contacting surface  121  similar to tissue contacting surface  121  of staple cartridge  204  of surgical stapling instrument  200 . Accordingly, reference is made to  FIG. 7  and the above detailed discussion of tissue contacting surface  121  of staple cartridge  204  for an illustration and a discussion of tissue contacting surface  121  of staple cartridge  310  of surgical stapling instrument  300 . 
     In operation, surgical stapling instrument  300  is fired similarly to and in accordance with other known surgical stapling instruments. For a detailed discussion of the approximation and firing of surgical stapling instrument  300 , reference is made to commonly assigned U.S. Pat. No. 5,865,361, currently assigned to Tyco Healthcare Group LP, the entire contents of which is incorporated herein by reference. 
     Following the firing of surgical stapling instrument  300  the resulting tissue interface, as seen in cross-section, is substantially similar to the resulting tissue interface, as seen in cross-section, following the firing of surgical stapling instruments  100  and  200 . Accordingly, as seen in  FIG. 16B , some or all of surgical fasteners  125   a - 125   c  serve to hold tissues “A” and “B” to one another while surgical fasteners  125   c  also provide the hemostasis. 
     While surgical stapling instrument  300  is a linear-type surgical stapler as compared to surgical stapling instrument  100 , it is envisioned and within the scope of the present disclosure, that surgical stapling instrument  300  can include a tissue contacting surface having a cross-sectional profile for at least one of the anvil and the staple cartridge which is substantially similar to the tissue contacting surfaces of the anvil and the staple cartridge of surgical stapling instrument  100 , as shown in  FIGS. 3A-3D . 
     Turning now to  FIGS. 6 ,  6 A,  7 , and  7 A, a surgical stapling instrument, of the transverse anastomosis type for performing surgical anastomotic stapling, in accordance with yet another embodiment of the disclosure, is generally designated as  400 . Surgical stapling instrument  400  includes a handle  402 , a barrel  404  extending from handle  402 , and an arm  406  extending from the distal end of barrel  404 . Surgical stapling instrument  400  further includes an anvil member  408  orthogonally affixed to a distal end of arm  406  and a staple cartridge receiver  410  operatively coupled to the distal end of barrel  404  for holding a disposable staple cartridge  412  thereon. Anvil member  408  is illustrated in further detail in  FIG. 6A  and includes a tissue contacting surface  420  wherein tissue contacting surface  420  has a plurality of pockets  425  that substantially align with retention slots  123  ( FIG. 7 ). Cooperative alignment between pockets  425  and retention slots  123  form completed surgical fasteners  125  upon actuation of the actuation mechanism in surgical stapling instrument  400 . 
     Staple cartridge  412  of surgical stapling instrument  400  includes a stepped tissue contacting surface  121  similar to tissue contacting surface  121  of staple cartridge  204  of surgical stapling instrument  200 . Accordingly, reference is made to  FIG. 7  and the above detailed discussion of tissue contacting surface  121  of staple cartridge  204  for an illustration and a discussion of tissue contacting surface  121  of staple cartridge  412  of surgical stapling instrument  400 . Further still, staple cartridge  412  may include knife track  222  for slidably receiving a knife (not shown) therein. 
     In a further embodiment of the present disclosure, staple cartridge  412 ′ is illustrated in  FIG. 7A  and discussed in detail hereinafter. Staple cartridge  412 ′ is similar to staple cartridge  412 , but only includes three rows  119   a - c  of retention slots  123  disposed between outer walls of staple cartridge  412 ′. As in the previously discussed embodiment, each row  119   a - c  includes a plurality of surgical fasteners wherein surgical fasteners in row  119   a  have a different leg length from surgical fasteners disposed in row  119   b , while surgical fasteners disposed in row  119   c  have a leg length that is different from at least one of rows  119   a  or  119   b . This embodiment of the staple cartridge does not include a knife track. The arrangement and interrelationship of tissue contacting surfaces  121   a - c  is similar to that previously disclosed with reference to  FIG. 7 . 
     In operation, surgical stapling instrument  400  is fired similarly to and in accordance with other known surgical stapling instruments. For a detailed discussion of the approximation and firing of surgical stapling instrument  400 , reference is made to commonly assigned U.S. Pat. No. 5,964,394, currently assigned to Tyco Healthcare Group LP, the entire contents of which is incorporated herein by reference. 
     Following the firing of surgical stapling instrument  400  the resulting tissue interface, as seen in cross-section, is substantially similar to the resulting tissue interface, as seen in cross-section, following the firing of surgical stapling instruments  100 - 300 . Accordingly, as seen in  FIG. 16B , some or all of surgical fasteners  125   a - 125   c  serve to hold tissues “A” and “B” to one another while surgical fasteners  125   c  also provide the hemostasis. 
     While surgical stapling instrument  400  is a linear-type surgical stapler as compared to surgical stapling instrument  100 , it is envisioned and within the scope of the present disclosure, that surgical stapling instrument  400  can include a tissue contacting surface having a cross-sectional profile for at least one of the anvil and the staple cartridge which is substantially similar to the tissue contacting surfaces of the anvil and the staple cartridge of surgical stapling instrument  100 , as shown in  FIGS. 3A-3D . 
     While each of the surgical stapling instruments described above and shown herein are configured and adapted to fire surgical fasteners  125 , it is envisioned and within the scope of the present disclosure, that tissue contacting surfaces of surgical instruments used in connection with applying two-part fasteners can also have stepped configurations as shown and described herein. A typical two-part surgical fastener applying instrument is shown and described in commonly assigned U.S. Pat. No. 5,573,169, currently assigned to Tyco Healthcare Group LP, the entire contents of which is incorporated herein by reference. 
     In one further embodiment of the present disclosure, as illustrated in  FIGS. 8-10 , surgical stapling apparatus  300  includes an operative tool  506  disposed at one end of elongated shaft  304 . Operative tool  506  includes anvil member  308  and a staple cartridge  510 . Staple cartridge  510  may be included in a disposable surgical stapling apparatus or in a reusable surgical stapling apparatus. In particular, staple cartridge  510  includes a tissue contacting surface  520  having a plurality of retention slots  523  disposed therein and arranged in rows that are substantially aligned with a longitudinal axis of staple cartridge  510 . As seen in  FIG. 8 , each row of retention slots  523  is longitudinally offset from an adjacent row of retention slots. In particular, an optional knife channel  530  is disposed along the longitudinal axis of staple cartridge  510  that is adapted for slidably receiving a knife (not shown). 
     Referring now to  FIG. 9A , operative tool  506  is shown in cross-section and illustrates the several components included in staple cartridge  510 . Anvil member  308  includes a substantially planar tissue contacting surface  320  that is substantially parallel to a bottom surface  512  or parallel to a plane defined by the backspans of surgical fasteners  125   a ,  125   b , or  125   c . Staple cartridge  510  includes outer walls  514  having a first height and inner walls  516  having a second height wherein the second height is greater than the first height. Tissue contacting surface  520  is attached to inner walls  516  and to outer walls  514  and defines an angle with respect to a plane that is orthogonal to inner walls  516 . Tissue contacting surface  520  defines a generally curved path between outer walls  514  (i.e. generally convex or elliptical as viewed in cross-section). Additionally, a plurality of surgical fasteners  125   a - c  are disposed in staple cartridge  510  wherein each row of retention pockets  523  includes a number of substantially identical surgical fasteners (i.e.  125   a ,  125   b , or  125   c ). Similar to previous embodiments, legs  25   a - c  of surgical fasteners  125   a - c  have different lengths. In this embodiment, surgical fasteners  25   a  have a leg length of about 3.8 mm, surgical fasteners  25   b  have a leg length of about 3.5 mm, and surgical fasteners  25   c  have a leg length of about 2.5 mm. 
     As seen in  FIG. 9A , surgical fasteners  125   a - c  are disposed in staple cartridge  510  such that surgical fasteners  125   c  are proximate to outer walls  514 , surgical fasteners  125   a  are disposed proximate to inner walls  516 , and surgical fasteners  125   b  are disposed therebetween. In cooperation with the surgical fasteners of varying height, staple cartridge  510  includes fastener ejection members  540  that include staple pushers  542 ,  544 , and  546  of differing heights. Staple pusher  542  has the greatest height dimension, staple pusher  546  has the least height dimension, and staple pusher  544  has a height dimension therebetween. In this embodiment, surgical fasteners  125   a - c  are arranged to cooperate with staple pushers  546 ,  544 , and  542  respectively. Fastener ejection member  540  is adapted for substantially vertical movement when it cooperatively engages with an actuation mechanism (not shown). An example of a suitable actuation mechanism is disclosed in U.S. Pat. No. 5,865,361 as discussed with reference to previously disclosed surgical stapling instrument  300 . 
     As illustrated in  FIG. 9A , fastener ejection member  540  includes staple pushers  542 ,  544 , and  546  that are connected to each other by a connecting member  548 , such that all of the pusher plates translate substantially simultaneously through staple cartridge  510 . In an alternate embodiment, fastener ejection member  540 ′ includes pusher plates  542 ,  544 , and  546  that are individually set within staple cartridge  510 . In this embodiment, each row of staple pushers is individually actuatable and independent of the other rows of staple pushers. Either embodiment of the fastener ejection member  540 ,  540 ′ may be used in any of the disclosed staple cartridges. Fastener ejection member  540 ′ is illustrated in  FIG. 9A  and, for the sake of clarity, will not be illustrated in other embodiments of the disclosed surgical stapling apparatus. 
     In addition, staple cartridge  510  may include a plurality of staple guides or channels  525 , shown in phantom, that extend from an inside surface of tissue contacting surface  520  towards fastener ejection member  540  or  540 ′. In particular, staple channels  525  extend towards staple pushers  542 ,  544 , and  546 , and may also vary in height according to their placement within staple cartridge  510 . Each staple channel  525  is substantially equal in width to a width of its corresponding staple pusher  542 ,  544 , or  546 . Staple channels  525 , in cooperation with retention slots  523  form staple pockets and improve the stability of surgical fasteners  125   a - c , thereby minimizing lateral or rotational movement of surgical fasteners  125   a - c  and consequently improving the formation of completed fasteners. Further still, staple channels  525  typically have a shape that corresponds to the shape of staple pushers  542 ,  544 , and  546 . For the sake of clarity, staple channels  525  are only illustrated in  FIG. 9A , although staple channels  525  may be included in any of the disclosed embodiments of the staple cartridge. 
     Alternate embodiments of operative tool  506  are illustrated in  FIGS. 9B and 9C . These alternate embodiments are identified as operative tool  506   a  and  506   b  respectively. Referring initially to  FIG. 9B , operative tool  506   a  includes substantially the same or similar components discussed hereinabove for operative tool  506  with the differences discussed hereinbelow. In contrast to operative tool  506  ( FIG. 9A ), surgical fasteners  125   a - c  of operative tool  506   a  are arranged in staple cartridge  510   a  such that surgical fasteners  125   a  are proximate to outer walls  514 , surgical fasteners  125   c  are proximate to inner walls  516 , and surgical fasteners  125   b  are disposed therebetween. In addition, operative tool  506   a  includes tissue contacting surface  520   a  that includes first and second surfaces  522   a  and  524   a . Each of first and second surfaces  522   a ,  524   a  has a width dimension sufficient to include at least one row of surgical fasteners. First surface  522   a  is substantially parallel to bottom surface  512 , while second surface  524   a  defines a substantially uniform angle. In particular, second surface  524   a  extends outwards and downwards from an outer edge of first surface  522   a  and defines the substantially uniform angle with respect to bottom surface  512 . 
     Turning now to  FIG. 9C , operative tool  506   b  includes staple cartridge  510   a  that was discussed in reference to  FIG. 9B  and anvil member  308   c . Anvil member  308   c  includes tissue contacting surface  320   c . In particular, tissue contacting surface  320   c  includes surfaces  322   c  and  324   c . Surface  324   c  is substantially parallel to bottom surface  512  has a width dimension that is substantially equal to the width dimensions of the first surfaces  522   a  and knife channel  530 , while each surface  322   c  substantial complements corresponding second surface  524   a . This arrangement between the surfaces of anvil member  308   c  and tissue contacting surface  520   a  maintains a substantially uniform gap between the surfaces from the centerline of operative tool  506   b  to its outer walls  514 . 
     Alternatively, as shown in  FIG. 10 , surgical fasteners  125   a - c  are disposed in staple cartridge  510 ′ such that surgical fasteners  125   a  are proximate to outer walls  514 , surgical fasteners  125   c  are disposed proximate to inner walls  516 , and surgical fasteners  125   b  are disposed therebetween. Contrary to the previous embodiment, surgical fasteners  125   a - c  are arranged to cooperate with staple pushers  542 ,  544 , and  546  respectively. After a number of layers of body tissue are positioned between tissue contacting surfaces  320  and  520 , the actuation mechanism is actuated for sequentially ejecting surgical fasteners  125   a - c  through retention slots  523  whereby interaction between surgical fasteners  125   a - c  and anvil member  308  forms completed surgical fasteners for joining the layers of body tissue. 
     When tissue contacting surface  320  of anvil member  308  is repositioned proximate to tissue contacting surface  520  of staple cartridge  510 ′, the amount of pressure applied to the layers of tissue disposed therebetween varies along a plane that is transverse to the longitudinal axis of staple cartridge  510 ′. Since the distance between tissue contacting surfaces  320  and  520  is at a minimum in the region nearest inner walls  516  (i.e. the centerline of staple cartridge  510 ′), a maximum pressure is applied to the layers of tissue disposed in this region. Conversely, the distance between tissue contacting surfaces  320  and  520  is at a maximum in the region near outer walls  514 , a minimum pressure is applied to the layers disposed in this region. In addition, the proximal relationship between anvil member  308  and staple cartridge  510 ′ defines a plurality of gaps therebetween. A first gap is defined between tissue contacting surfaces  320  and  520  (i.e. along the centerline of staple cartridge  510 ′), while a second gap is defined between tissue contacting surfaces  320  and  520  along outer walls  514 . As seen in  FIG. 10 , the first gap is not equal to the second gap. Further still, a number of other gaps may be defined between tissue contacting surfaces  320  and  520  at other points of reference existing between the centerline and outer walls  514  in staple cartridge  510 ′. Since tissue contacting surface  520  slopes toward outer walls  514  to define a substantially uniform angle, the pressure applied to the layers of tissue disposed between tissue contacting surfaces  320  and  520  uniformly decreases from inner wall  516  to outer wall  514 . 
     By angling tissue contacting surface  520  downwards from the centerline of staple cartridge  510 ′, reduced compressive forces are applied to the layers of tissue disposed between tissue contacting surfaces  320  and  520  thereby minimizing trauma to the layers of tissue disposed therebetween. Therefore, layers of tissue disposed between tissue contacting surfaces  320  and  520  will have a minimum thickness nearest knife channel  530  (i.e. nearest the centerline of staple cartridge  510 ′) and a maximum thickness nearest outer walls  514 . In addition, anvil member  308  and staple cartridge  510 ′ are dimensioned and arranged such that compressive forces applied to the layers of tissue are minimal thereby further reducing trauma to the layers of tissue. This configuration defines a gap between tissue contacting surfaces  320  and  520  that is a maximum along knife channel  530  (i.e. the centerline of staple cartridge  510  or  510 ′) and a minimum along outer walls of staple cartridge  510  ( FIG. 9A ) or  510 ′ ( FIG. 10 ). 
     Further still, this configuration is applicable to similar staple cartridges and anvil members as will be discussed in detail hereinafter with respect to  FIGS. 11-15 . When anvil member  308 ′ is repositioned into proximity with staple cartridge  510 ′ (i.e. in a pre-fire position) to retain layers of body tissue therebetween, the layers of tissue are compressed. The maximum compression occurs along the centerline (i.e. first or minimum gap) and urges fluid stored in the layers of tissue towards the outer edges of the tissue (i.e. away from the centerline of staple cartridge  510 ′). By reducing the amount of fluid retained in the layers of tissue proximal to the centerline, the overall thickness of the tissue layers decreases. The decrease in overall tissue thickness is such that a staple having a shorter leg length (i.e. surgical fastener  125   c ) is capable of fastening both layers of tissue while minimizing trauma to the fastened layers of tissue. The gap increases towards the outer walls of staple cartridge  510 ′ (i.e. the amount of compression decreases) and surgical fasteners having a longer leg length (i.e. surgical fasteners  125   a  and  125   b ) are capable of fastening both layers of tissue. 
     Leg lengths of surgical fasteners  125   c ,  125   b , and  125   a  increase in a direction moving from inner walls  516  towards outer walls  514 . By providing surgical fasteners having increasing leg lengths along a plane that is orthogonal to inner walls  516 , the completed (i.e. formed) surgical fasteners join increasing thicknesses of tissue without unduly traumatizing the joined layers of tissue. 
     In a further embodiment, as illustrated in  FIG. 11 , operative tool  506 ″ includes staple cartridge  510 ′ and anvil member  308 ′. Staple cartridge  510 ′ was previously discussed in detail hereinabove with reference to  FIG. 10 . Tissue contacting surface  520  may define a more uniform angle ( FIG. 11 ) than in the embodiments of  FIGS. 9A and 10  wherein the angle or pitch of tissue contacting surface is substantially constant between inner walls  516  and outer walls  514 . Anvil member  308 ′ includes tissue contacting surface  320 ′ having tapered surfaces  322 ′ and  324 ′. Surfaces  322 ′ and  324 ′ are connected to outer walls of anvil member  308 ′ while extending inwards (i.e. towards the centerline of staple cartridge  510 ′) and downwards (i.e. towards tissue contacting surface  520 ) thereby defining an angle. It is envisioned that the angle defined by tapered surfaces  322 ′ and  324 ′ will be substantially similar to the angle defined by tissue contacting surface  520 , but in an opposed direction forming a generally V-shaped configuration. Thus, compressive forces applied to the layers of tissue will be further reduced thereby further reducing the trauma to layers of tissue disposed between tissue contacting surfaces  520  and  320 ′. As in the embodiment of  FIG. 10 , the maximum pressure applied to the layers of tissue will exist in the region near knife channel  530  while pressures applied to the layers of tissue will decrease uniformly towards outer walls  514 . Formation and location of surgical fasteners  125   a - c  is substantially similar to that of the embodiment of  FIG. 10  along with the attendant advantages. 
     Referring now to  FIG. 12 , a further embodiment of the present disclosure is shown as part of operative tool  606 . Operative tool  606  includes a staple cartridge  610  and anvil member  308 . In this embodiment, tissue contacting surface  620  includes surfaces  622  and  624 . Surface  622  is bisected along its longitudinal axis by knife channel  630  and substantially parallel to a bottom surface  612  or parallel to a plane defined by the backspans of surgical fasteners  125   a ,  125   b , or  125   c . In addition, surface  622  has a width dimension sufficient to accommodate at least one row of retention slots  623  on each side of knife channel  630 . Surface  624  connects outer edges of surface  622  to outer walls  614  defining an angle on either side of knife channel  630  with respect to a plane that is substantially orthogonal to inner walls  616  (i.e. substantially parallel to surface  622 ) and has a width dimension sufficient to accommodate at least one row of retention slots on each side of knife channel  630 . Staple cartridge  610  includes a plurality of surgical fasteners  125   a - c  and fastener ejection members  540  that were previously discussed in detail with respect to  FIGS. 9A and 10 . In particular, staple cartridge  610  includes the arrangement of surgical fasteners  125   a - c  and fastener ejection members  540  as described with respect to staple cartridge  510 ′ ( FIGS. 10 and 11 ). 
     Similar to operative tool  506 , tissue contacting surface  320  is repositioned proximate to tissue contacting surface  620  of staple cartridge  610 . In this arrangement, the amount of pressure applied to the layers of tissue disposed therebetween varies along a plane that is transverse to the longitudinal axis of staple cartridge  610 . Specifically, the distance between tissue contacting surface  320  and surface  622  is a minimum, a maximum pressure is applied to the layers of tissue disposed in this region. Conversely, the distance between tissue contacting surface  320  and surfaces  624  is at a maximum in the region near outer walls  614 , a minimum pressure is applied to the layers disposed in this region. Since surface  624  slopes toward outer walls  614  to define a substantially uniform angle, the pressure applied to the layers of tissue disposed between tissue contacting surface  320  and surfaces  624  uniformly decreases from an outer edge of surface  622  towards outer wall  614 . 
     By angling surface  624  downwards from the edge of surface  622 , reduced compressive forces are applied to the layers of tissue disposed between tissue contacting surface  320  and surfaces  624  thereby minimizing trauma to the layers of tissue disposed therebetween. Layers of tissue disposed between tissue contacting surfaces  320  and  620  will have a minimum thickness nearest knife channel  630  and a maximum thickness nearest outer walls  614 . In addition, anvil member  308  and staple cartridge  610  are dimensioned and arranged such that compressive forces applied to the layers of tissue are minimal thereby further reducing trauma to the layers of tissue. 
     Leg lengths of surgical fasteners  125   c ,  125   b , and  125   a  increase in a direction moving from inner walls  616  towards outer walls  614 . By providing surgical fasteners having increasing leg lengths along a plane that is orthogonal to inner walls  616 , the completed (i.e. formed) surgical fasteners join increasing thicknesses of tissue without unduly traumatizing the joined layers of tissue. 
     In a further embodiment, operative tool  606 ′ is illustrated in  FIG. 13 . Operative tool  606 ′ includes staple cartridge  610 , that was described in detail hereinabove with respect to  FIG. 12 , and anvil member  308 ″. Anvil member  308 ″ includes a tissue contacting surface  320 ″ formed from surfaces  332 ″ and  336 ″. Surface  336 ″ is substantially parallel to surface  622  and has a width dimension that is substantially similar to the width dimension of surface  622 . Surfaces  332 ″ are tapered and connected to outer walls of anvil member  308 ″ and extend inwards (i.e. towards the centerline of staple cartridge  610 ) and downwards (i.e. towards tissue contacting surface  620 ) thereby defining an angle. It is envisioned that the angle defined by tapered surfaces  332 ″ will be substantially similar to the angle defined by surfaces  624 , but in an opposed direction. Thus, compressive forces applied to the layers of tissue will be further reduced thereby further reducing the trauma to layers of tissue disposed between surfaces  624  and  332 ″. As in the embodiment of  FIG. 10 , the maximum pressure applied to the layers of tissue will exist in the region along surface  622  while pressures applied to the layers of tissue will decrease uniformly along surfaces  624  towards outer walls  614 . Formation and location of surgical fasteners  125   a - c  is substantially similar to that of the embodiment of  FIG. 12  along with the attendant advantages. 
     In yet another embodiment, operative tool  706  is illustrated in  FIG. 14 . Staple cartridge  710  is similar to staple cartridge  610 . The differences between staple cartridges  610  and  710  will be discussed hereinafter. As in staple cartridge  610  ( FIG. 12 ), staple cartridge  710  includes tissue contacting surface  720  formed from surfaces  722  and  724 . Surface  722  differs from surface  622  in that it has a width dimension sufficient to accommodate at least two rows of surgical fasteners. As in staple cartridge  610 , surfaces  724  are attached to outer edges of surface  722  and outer walls  714  to define angles. The interaction between staple cartridge  710  and anvil member  308  for capturing tissue and forming surgical fasteners is substantially similar to the interaction between staple cartridge  610  and anvil member  308  and, for the sake of brevity, will not be repeated herein. 
     In  FIG. 15 , an alternate embodiment of operative tool  706 ′ is illustrated. Operative tool  706 ′ includes staple cartridge  710 , as discussed in detail hereinabove, and anvil member  308 ″. Anvil member  308 ″ includes a tissue contacting surface  320 ″ formed from surfaces  332 ″ and  336 ″. Surface  336 ″ is substantially parallel to surface  722  and has a width dimension that is substantially similar to a width dimension of surface  722 . Surfaces  332 ″ are tapered and connected to outer walls of anvil member  308 ″ and extend inwards (i.e. towards centerline of staple cartridge  710 ) and downwards (i.e. towards tissue contacting surface  720 ) thereby defining an angle. It is envisioned that the angle defined by tapered surfaces  332 ″ will be substantially similar to the angle defined by surfaces  724 , but in an opposed direction. Thus, compressive forces applied to the layers of tissue will be further reduced, thereby further reducing the trauma to the layers of tissue disposed between surfaces  724  and  332 ″. As in the embodiment of FIG.  14 , the maximum pressure applied to the layers of tissue will exist in the region along surface  722  while pressures applied to the layers of tissue will decrease uniformly along surfaces  724  towards outer walls  714 . Formation and location of surgical fasteners  125   a - c  is substantially similar to that of the embodiment of  FIG. 14  along with the attendant advantages. 
     Turning now to  FIG. 16B , a cross-section of the resulting tissue interface, following the firing of staple cartridge  510 ′, is shown. As seen in  FIG. 16B , the tissue interface has a substantially tapered profile. In particular, some or all of surgical fasteners  125   a - 125   c  serve to hold tissues “A” and “B” to one another while surgical fasteners  125   c  also provide the hemostasis. This resulting cross-section is also applicable to the firing of staple cartridges  610  and  710 . When staple cartridge  510  is fired, some or all of surgical fasteners  125   a - 5   c  serve to hold tissues “A” and “B” to one another while surgical fasteners  125   a  also provide the hemostasis. When layers of tissue “A” and “B” are fastened using a conventional surgical stapling device and conventional staples “S”, there exists a sharp transition from the un-fastened layers of tissue to the fastened layers of tissue that is illustrated in  FIG. 16A . This may result in a greater load being placed on the layers of tissue and may produce an undesirable effect on the layers of tissue. In comparison, as shown in  FIG. 16B , the tissue interface has a gradual transition from the un-fastened layers of tissue to the fastened layers of tissue and also within the fastened layers of tissue. This arrangement provides gradual tissue loading or compression due to the varying sizes of the formed surgical fasteners  125   a - c , thereby minimizing tissue trauma while maintaining a relatively high degree of hemostasis and anastomotic strength. 
     In a further embodiment of the present disclosure, as shown in  FIGS. 8 and 10 , operative tool  506 ′ includes a wound closure assembly  50 . Wound closure assembly  50  includes at least one storage device or reservoir  52  and at least one supply line  54 . Supply line  54  fluidly couples reservoir  52  to staple cartridge  510 ′ for delivering an amount of a wound closure material “W”. In particular, supply line  54  delivers wound closure material “W” into knife channel  530  such that when surgical fasteners  125   a - c  are formed, wound closure material “W” migrates along the layers of tissue adjacent to tissue contacting surface  520  (i.e. the target site). By providing wound closure material “W” in combination with surgical fasteners  125   a - c , the bond formed between the layers of tissue has improved strength. 
     Compression of reservoir  52  causes wound closure material “W” contained therein to be urged through supply line  54  and dispensed via knife channel  530 . Preferably, wound closure material “W” is dispensed during the staple firing procedure so that wound closure material “W” is dispensed along the length of the staple line and/or a knife cut line. Although wound closure assembly is discussed and illustrated with respect to  FIG. 10 , it is contemplated that wound closure assembly  50  is adaptable for use with other disclosed embodiments of staple cartridge  510 ′ (i.e.  510 ,  610 , or  710 ). It is further contemplated that an additional reservoir may be included for wound closure materials formed by combining two substances or that reservoir  52  may include a plurality of internal chambers (shown in phantom) for storing quantities of substances to be combined to form wound closure material “W”. 
     It is envisioned that wound closure material “W” can include one or a combination of adhesives, hemostats, sealants. Surgical biocompatible wound closure materials which can be employed in or applied the surgical instruments, especially surgical staplers, include adhesives whose function is to attach or hold organs, tissues or structures, sealants to prevent fluid leakage, and hemostats to halt or prevent bleeding. Examples of adhesives which can be employed include protein derived, aldehyde-based adhesive materials, for example, the commercially available albumin/glutaraldehyde materials sold under the trade designation BIOGLUE™ by Cryolife, Inc., and cyanoacrylate-based materials sold under the trade designations INDERMIL™ and DERMA BOND™ by Tyco Healthcare Group, LP and Ethicon Endosurgery, Inc., respectively. Examples of sealants, which can be employed, include fibrin sealants and collagen-based and synthetic polymer-based tissue sealants. Examples of commercially available sealants are synthetic polyethylene glycol-based, hydrogel materials sold under the trade designation COSEAL™ by Cohesion Technologies and Baxter International, Inc. Examples of hemostat materials, which can be employed, include fibrin-based, collagen-based, oxidized regenerated cellulose-based and gelatin-based topical hemostats. Examples of commercially available hemostat materials are fibrinogen-thrombin combination materials under sold the trade designations COSTASIS™ by Tyco Healthcare Group, LP, and TISSEEL™ sold by Baxter International, Inc. Hemostats herein include astringents, e.g., aluminum sulfate, and coagulants. 
     It is to be understood that the dispensing of wound closure material “W” can be as a fluid spray of any suitable volume, including a mist, applied temporarily, continuously, or continually. Particulate material, e.g. a fine powder is contemplated to be a fluid within the scope of this disclosure. 
     It is provided that a number of different wound closure materials “W” can be dispensed by wound closure assembly  50  or a combination of the number of different wound closure materials “W”. The wound closure material dispensed by wound closure assembly  50  can, for example, be an astringent, such as a sulfate of aluminum, which causes small blood vessels to close and helps the blood to coagulate. It is provided that wound closure material “W” can be an astringent provided in the material commercially available under the trade designation NO NIX® Styptic Pencils from Requa, Inc. 
     Referring now to  FIGS. 17A-F , further embodiments of the presently disclosed operative tool are illustrated. As shown in  FIG. 17A , operative tool  806   a  includes anvil member  308  and staple cartridge  810   a . Anvil member  308  was previously described hereinabove with reference to  FIG. 9A  and, for the sake of brevity, will not be discussed again. In addition, staple cartridge  810   a  is similar to staple cartridge  710  ( FIG. 14 ) with the differences being discussed in detail hereinbelow. Similar to staple cartridge  710 , staple cartridge  810   a  includes a tissue contacting surface  820 , outer and inner walls  814 ,  816 , a knife channel  830 , and a bottom surface  812 . Located within staple cartridge  810   a  is a plurality of surgical fasteners  125   a ,  125   b , and  125   c  that were previously discussed with respect to staple cartridge  710 . In addition, staple cartridge  810   a  includes a plurality of fastener ejection members  540  that were previously described with respect to  FIG. 9 . 
     In this embodiment, surfaces  822  and  824  define tissue contacting surface  820 . As with previous embodiments of the presently disclosed staple cartridge, tissue contacting surface  820  includes a plurality of retention slots  823 . Surface  822  is a planar surface that is substantially parallel to bottom surface  812 , while surface  824  is a generally arcuate surface. Each surface  822 ,  824  includes at least one row of retention slots  823 . Additionally, inner wall  816  has a first height and outer wall  814  has a second height, wherein the first height is greater than the second height. One edge of surface  824  is attached to outer wall  814  while the opposing edge is attached to an edge of surface  822 , thereby defining a generally concave surface with respect to surface  822 . 
     Similar to previous embodiments of the presently disclosed operative tool, tissue contacting surface  320  of anvil member  308  is repositioned proximate to tissue contacting surface  820  of staple cartridge  810   a . In this arrangement, the amount of pressure applied to the layers of tissue disposed therebetween varies along a plane that is transverse to the longitudinal axis of staple cartridge  810   a . Specifically, the distance between tissue contacting surface  320  and surface  822  is a minimum, such that a maximum pressure is applied to the layers of tissue disposed in this region. Conversely, the distance between tissue contacting surface  320  and surfaces  824  is at a maximum in the region near outer walls  814 , such that a minimum pressure is applied to the layers disposed in this region. Since surface  824  curves downward as it approaches outer walls  814 , the pressure applied to the layers of tissue disposed between tissue contacting surface  320  and surfaces  824  decreases from an outer edge of surface  822  towards outer wall  814 . The amount of pressure decrease is a function of curvature of surface  824 . 
     By curving surface  824  downwards from the edge of surface  822 , reduced compressive forces are applied to the layers of tissue disposed between tissue contacting surface  320  and surfaces  824  thereby minimizing trauma to the layers of tissue disposed therebetween. Layers of tissue disposed between tissue contacting surfaces  320  and  820  will have a minimum thickness nearest knife channel  830  and a maximum thickness nearest outer walls  814 . In addition, anvil member  308  and staple cartridge  810   a  are dimensioned and arranged such that compressive forces applied to the layers of tissue are minimal thereby further reducing trauma to the layers of tissue. 
     Leg lengths of surgical fasteners  125   c ,  125   b , and  125   a  increase in a direction moving from inner walls  816  towards outer walls  814 . By providing surgical fasteners having increasing leg lengths along a plane that is orthogonal to inner walls  816 , the completed (i.e. formed) surgical fasteners join increasing thicknesses of tissue without unduly traumatizing the joined layers of tissue. A more detailed description of surgical fasteners  125   a - c  and fastener ejection members  540  is discussed hereinabove with reference to  FIG. 9 . 
     In the embodiment illustrated in  FIG. 17B , operative tool  806   b  includes staple cartridge  810   b  that is substantially similar to staple cartridge  810   a  with the differences between them being discussed below. In staple cartridge  810   b , outer walls  814 ′ and inner walls  816 ′ have a lower height than outer walls  814  and inner walls  816  of staple cartridge  810   a . In this configuration, tissue contacting surface  820  is closer to bottom surface  812  such that tips of surgical fasteners  125   a ,  125   b , and  125   c  extend into retention slots  823  and are substantially flush with tissue contacting surface  820 . 
     Referring now to  FIGS. 17C and 17D , operative tools  806   c  and  806   d  are illustrated. Operative tools  806   c  and  806   d  include staple cartridges  810   a  and  810   b  (as discussed hereinabove) respectively. In these embodiments, anvil member  308   a  replaces anvil member  308 . In this embodiment, anvil member  308   a  includes a tissue contacting surface  320   a  formed from surfaces  332   a  and  336   a . Surface  336   a  is substantially parallel to surface  822  and has a width dimension that is substantially similar to the width dimension of surface  822 . Surfaces  332   a  are generally arcuate such that a thickness of anvil member  308   a  is at a minimum in the region near its outer edge and a maximum along surface  336   a . It is envisioned that the curve defined by surfaces  332   a  will be substantially similar to the curve defined by surfaces  824 , but in an opposed direction (i.e. defining a convex relationship with respect to surface  822 ). Thus, compressive forces applied to the layers of tissue will be further reduced, thereby further reducing trauma to the layers of tissue positioned between surfaces  824  and  332   a.    
     As in the embodiment of  FIGS. 17A and 17B , the maximum pressure applied to the layers of tissue will exist in the region along surface  822  while pressures applied to the layers of tissue will decrease along surfaces  824  towards outer walls  814 ,  814 ′. The decrease in pressure along the gradient defined by surfaces  824  and  332   a  is proportional to the curvature of each surface. Formation and location of surgical fasteners  125   a - c  is substantially similar to that of the embodiment of  FIGS. 17A and 17B  along with the attendant advantages. 
     In a further embodiment, operative tool  906  is illustrated in  FIG. 18A . Operative tool  906  includes anvil member  308  and staple cartridge  910 . Staple cartridge  910  is substantially similar to staple cartridge  810  wherein the same or similar components are renumbered accordingly and the differences discussed in detail hereinafter. Tissue contacting surface  920  includes surfaces  922  and  924  wherein each surface includes a plurality of retention slots  923 . Similar to the embodiment shown in  FIGS. 17A-D , surface  922  is a generally planar surface that is substantially parallel to a bottom surface  912  and defines a right angle at its junction with inner wall  916 . Surface  924  is also a generally planar surface that substantially parallel with bottom surface  912  and surface  922 , wherein surfaces  922  and  924  are vertically spaced apart such that they are not coplanar with one another. Additionally, inner wall  916  has a first height and outer wall  914  has a second height, wherein the first height is greater than the second height. 
     As in the previous embodiments of the presently disclosed operative tool, tissue contacting surface  320  of anvil member  308  is repositioned proximate to tissue contacting surface  920  of staple cartridge  910 . In this arrangement, the amount of pressure applied to the layers of tissue disposed therebetween varies along a plane that is transverse to the longitudinal axis of staple cartridge  910 . Specifically, the distance between tissue contacting surface  320  and surface  922  is a minimum, such that a maximum pressure is applied to the layers of tissue disposed in this region. Conversely, the distance between tissue contacting surface  320  and surfaces  824  is at a maximum, such that a minimum pressure is applied to the layers disposed in this region. Since surface  924  is generally planar, the pressure applied to the layers of tissue disposed between tissue contacting surface  320  and surfaces  924  is substantially uniform and less than the pressure applied to the layers of tissue positioned between tissue contacting surface  320  and surface  922 . 
     Leg lengths of surgical fasteners  125   c ,  125   b , and  125   a  increase in a direction moving from inner walls  916  towards outer walls  914 . By providing surgical fasteners having increasing leg lengths along a plane that is orthogonal to inner walls  916 , the completed (i.e. formed) surgical fasteners join increasing thicknesses of tissue without unduly traumatizing the joined layers of tissue. A more detailed description of surgical fasteners  125   a - c  and fastener ejection members  540  is discussed hereinabove with reference to  FIG. 9 . 
     Referring now to  FIG. 17E , a further embodiment of operative tool  806  is illustrated and referenced as operative tool  806   e . Operative tool  806   e  includes substantially the same or similar components as operative tool  806   a  ( FIG. 17A ) with the differences being discussed hereinafter. In particular, operative tool  806   e  includes anvil member  308  and staple cartridge  810   b . Staple cartridge differs from staple cartridge  810   a  in that tissue contacting surface  824   a  is an arcuate structure extending from the centerline to outer walls  514  of staple cartridge  810   b . The arrangement between tissue contacting surface  824   a  and tissue contacting surface  320  provides the same advantages and benefits as does the arrangements provided in the embodiments illustrated in  FIGS. 17A-D . 
     Alternatively, staple cartridge  810   b  may be used with anvil member  308   d  to form operative tool  806   f  that is illustrated in  FIG. 17F . Anvil member  308   d  includes tissue contacting surface  320   d  that is substantially complementary to tissue contacting surface  824   a . In this configuration, a substantially uniform gap is maintained between the surfaces from the centerline of operative tool  806   f  to its outer walls  814 . 
     A further embodiment of the presently disclosed operative tool is illustrated in  FIG. 18B  wherein anvil member  308  is replaced by anvil member  308   b . Operative tool  906   a  includes staple cartridge  910  and anvil member  308   b . In particular, anvil member  308   b  includes a tissue contacting surface  320   b  that is defined by surfaces  332   b  and  336   b . Similar to the embodiment shown in  FIG. 17D , tissue contacting surface  320   b  of anvil member  308   b  is complementary to tissue contacting surface  920  of staple cartridge  910  such that a greater gap is defined between surfaces  924  and  332   b  than between surfaces  924  and tissue contacting surface  320  ( FIG. 18A ). In this configuration, a reduced amount of pressure is applied to the layers of tissue captured therebetween. 
     Referring now to  FIGS. 19A and 19B , operative tools  1006   a  and  1006   b  are illustrated. Operative tool  1006   a  includes anvil member  308  and a staple cartridge  1010 . Staple cartridge  1010  is substantially similar to staple cartridge  510  wherein the same or similar components are renumbered accordingly and the differences discussed in detail hereinafter. Surface  1020  is substantially planar and substantially parallel to bottom surface  1012 . In this embodiment, a filler layer  1070  is positioned on surface  1020 . Filler layer  1070  is formed from a material that has sufficient resiliency to support layers of tissue while permitting surgical fasteners  125   a - c  to pass through during the formation of completed surgical fasteners. Filler layer  1070  may be a buttress material that is an organic or synthetic tissue used to reinforce tissue at a staple line. An example of a suitable material includes SEAMGUARD® from W.L. Gore &amp; Associates, Inc. 
     Filler layer  1070  is a generally triangular structure that tapers from a maximum height near knife channel  1030  towards a minimum height near outer walls  1014 . Thus, the gap defined between tissue contacting surface  320  and filler layer  1070  is at a minimum near knife channel  1030  and at a maximum near outer walls  1014 . As such, the amount of pressure applied to layers of tissue captured between tissue contacting surface  320  and filler layer  1070  is at a minimum near knife channel  1030  and at a maximum near outer walls  1014 , thereby providing the attendant advantages as in previous embodiments with respect to forming the surgical fasteners and minimizing trauma to the layers of tissue. In addition, filler layer  1070  may be formed from a resilient or semi-resilient material, thereby further minimizing trauma to the layers of tissue that are captured between tissue contacting surface  320  and surface  1020 . 
     Alternatively, a second filler layer  1070 , shown in phantom, may be positioned on tissue contacting surface  320 . Staple cartridge  1010  may include filler layer  1070  disposed on tissue contacting surface  1020 , on tissue contacting surface  320 , or on both tissue contacting surfaces  320 ,  1020  according to the surgical procedure to be performed. 
     In  FIG. 19B , operative tool  1006   b  includes previously described staple cartridge  1010  in cooperation with anvil member  308 ′. Anvil member  308 ′ includes tissue contacting surface  320 ′ having tapered surfaces  322 ′ and  324 ′. Surfaces  322 ′ and  324 ′ are connected to outer walls of anvil member  308 ′ while extending inwards (i.e. towards the centerline of staple cartridge  1010 ) and downwards (i.e. towards tissue contacting surface  1020 ) thereby defining an angle. It is envisioned that the angle defined by tapered surfaces  322 ′ and  324 ′ will be substantially similar to the angle defined by filler layer  1070 , but in an opposed direction forming a generally V-shaped configuration. Thus, compressive forces applied to the layers of tissue will be further reduced thereby further reducing the trauma to layers of tissue disposed between tissue contacting surface  320 ′ and filler layer  1070 . The maximum pressure applied to the layers of tissue will exist in the region near knife channel  1030  while pressures applied to the layers of tissue will decrease uniformly towards outer walls  1014 . Formation and location of surgical fasteners  125   a - c  is substantially similar to that of the embodiment of  FIG. 19A  along with the attendant advantages. 
     Turning now to  FIG. 20A , an alternate embodiment of staple cartridge  412 ′ ( FIG. 7A ) is illustrated and described hereinafter. Staple cartridge  412 ″ is similar to staple cartridge  412 ′ wherein the same or similar components are renumbered accordingly and the differences discussed in detail hereinafter. Staple cartridge  412 ″ includes a plurality of tissue contacting surfaces  421   a - c , wherein each tissue contacting surface is a generally planar structure. Of the three surfaces, tissue contacting surface  421   b  has the greatest height and is vertically spaced apart from tissue contacting surfaces  421   a  and  421   c . Tissue contacting surfaces  421   a - c  are substantially parallel with one another, wherein tissue contacting surface  421   b  does not lie in the same plane as either of tissue contacting surfaces  421   a  or  421   c.    
     Anvil member  408  includes pockets  450  and tissue contacting surface  430 . Pockets  450  substantially align with retention slots  123  for forming completed surgical fasteners. In this configuration, a minimum gap is defined between tissue contacting surface  430  and tissue contacting surface  421   b  while a maximum gap is defined between tissue contacting surface  430  and tissue contacting surfaces  421   a  and  421   c . Surgical fasteners  425   a - c  are associated with tissue contacting surfaces  421   a - c  respectively. Surgical fasteners  425   a - c  are substantially similar to surgical fasteners  125   a - c  and the differences between them are discussed in detail hereinafter. In one embodiment, surgical fasteners  425   a  and  425   c  are substantially identical and have a greater leg length than surgical fastener  425   b . By providing this arrangement of tissue contacting surfaces and surgical fasteners, reduced compressive forces are applied to the layers of tissue disposed between tissue contacting surface  430  and tissue contacting surfaces  421   a ,  421   c  as was discussed previously with respect to other embodiments of the presently disclosed staple cartridge. 
     In the alternative, staple cartridge  412 ″ may be used in cooperation with anvil member  408   a  as illustrated in  FIG. 20B . Anvil member  408   a  includes pockets  450  and tissue contacting surface  430 ′. Further still, tissue contacting surface  430 ′ includes surfaces  432  and  434 . Each of surfaces  432 ,  434  are generally planar surfaces that are substantially parallel to tissue contacting surfaces  421   a - c  of staple cartridge  412 ″. Surfaces  432  are vertically spaced apart from surface  434  such that the gap defined between surface  434  and tissue contacting surface  421   b  is a minimum while the gap defined between surfaces  432  and tissue contacting surfaces  421   a ,  421   c  is a maximum. Thus, reduced compressive forces are applied to the layers of tissue disposed between tissue contacting surfaces  421   a ,  421   c  and surfaces  432  of anvil member  408   a.    
     Alternatively, staple cartridge  412 ″ may be used in cooperation with anvil member  408   b  as illustrated in  FIG. 20C . Anvil member  408   b  includes surfaces  432   a  and  434   a . In contrast to surfaces  432  and  434  of anvil member  408   a  ( FIG. 20B ), surfaces  432   a  and  434   a  are generally arcuate. In this configuration, any potential trauma to tissue positioned between anvil member  408   b  and staple cartridge  412 ″ is reduced while maintaining the advantages and benefits of an increased gap between tissue contacting surfaces of anvil member  408   b  and staple cartridge  412 ″. 
     A further embodiment of the presently disclosed operative tool is illustrated in  FIG. 21A  and generally designated as  1106 . Operative tool  1106  includes staple cartridge  1110  and anvil member  308 . Anvil member  308  was previously described in detail with reference to  FIG. 9 . Staple cartridge  1110  includes the same or substantially similar components to staple cartridge  510  ( FIG. 9 ), wherein the same or similar components are renumbered accordingly and the differences discussed in detail hereinafter. 
     In particular, staple cartridge  1110  includes surgical fasteners  125   a - c  and corresponding pushers  1140 . In addition, staple cartridge  1110  includes outer walls  1114 , inner walls  1116 , and vertical members  1118 . Inner walls  1116  may be spaced apart for defining a knife channel  1130  therebetween. In addition, vertical members  1118  are generally planar structures that abut inner walls  1116  and generally have a height at least equal to that of inner walls  1116 . A top plate  1154  is a generally planar structure that connects inner wall  1116  and outer wall  1114 . In one embodiment, top plate  1154  is substantially parallel to bottom surface  1112 . In addition, top plate  1154  includes a plurality of retention slots  1123 . Vertically spaced above top plate  1154  is cross member  1150 . 
     Cross member  1150  includes a plurality of openings  1125  that are aligned with retention slots  1123  of top plate  1154 . In addition, cross member  1150  defines a tissue contacting surface  1120  that is substantially parallel to bottom surface  1112  in a first position. Specifically, an inner edge of cross member  1150  is flexibly attached to an edge of vertical member  1118  while an outer edge  1156  is spaced apart from a top edge  1114   a  of outer wall  1114  defining a gap  1152  therebetween. Cross member  1150  has sufficient rigidity such that when layers of tissue are positioned between tissue contacting surfaces  320  and  1120 , cross member  1150  maintains its substantially parallel relationship to bottom surface  1112 . Gap  1152  may include an elastomeric compression member that controls the amount of deflection by tissue contacting surface  1120 . 
     As anvil member  308  and staple cartridge  1110  are brought into a closer cooperative arrangement (i.e. during approximation and/or formation of the surgical fasteners), compressive forces generated by the relative movement between anvil member  308  and staple cartridge  1110  urge outer edge  1156  towards top edge  1114   a , thereby reducing gap  1152 . In addition, cross member  1154  (shown in phantom) flexes towards bottom wall  1112 , thereby providing an increased distance between tissue contacting surfaces  320  and  1120  at outer wall  1114  while maintaining a fixed (i.e. unflexed) distance between tissue contacting surfaces  320  and  1120  at vertical member  1118 . As cross member  1154  flexes, the distance between tissue contacting surfaces  320  and  1120  increases along an axis that is transverse to a longitudinal axis of staple cartridge  1110 . The distance between tissue contacting surfaces  320  and  1120  at any selected position along the transverse axis is related to the amount of flexion provided by cross member  1154 . Cross member  1150  is positionable throughout a plurality of positions including at least a first position that is substantially parallel to bottom surface  1112  and a second position wherein outer edge  1156  is in contact with top edge  1114   a.    
     When tissue contacting surface  320  of anvil member  308  is repositioned proximate to tissue contacting surface  1120  of staple cartridge  1110 , the amount of pressure applied to the layers of tissue disposed therebetween varies along a plane that is transverse to the longitudinal axis of staple cartridge  1110 . Since tissue contacting surface  1120  slopes toward outer walls  1114 , the pressure applied to the layers of tissue disposed between tissue contacting surfaces  320  and  1120  decreases from inner wall  1116  to outer wall  1114 . Further still, when cross member  1150  flexes towards top plate  1154 , it defines a curvate surface similar to tissue contacting surface  520  ( FIG. 9 ). Openings  1125  have a greater width dimension such that when cross member  1150  is urged towards top plate  1154 , the alignment of openings  1125  and retention slots  1123  is such that an unobstructed path is defined for surgical fasteners  125   a - c , thereby allowing surgical fasteners  125   a - c  to engage layers of tissue and contact anvil member  308 . 
     By flexing tissue contacting surface  1120  downwards from the centerline of staple cartridge  1110 , reduced compressive forces are applied to the layers of tissue disposed between tissue contacting surfaces  320  and  1120  thereby minimizing trauma to the layers of tissue disposed therebetween. Therefore, layers of tissue disposed between tissue contacting surfaces  320  and  1120  will have a minimum thickness nearest knife channel  1130  (i.e. nearest the centerline of staple cartridge  1110 ) and gradually increasing to a maximum thickness nearest outer walls  1114 . 
     Leg lengths of surgical fasteners  125   c ,  125   b , and  125   a  increase in a direction moving from inner walls  1116  towards outer walls  1114 . By providing surgical fasteners having increasing leg lengths along a plane that is orthogonal to inner walls  1116 , the completed (i.e. formed) surgical fasteners join increasing thicknesses of tissue without unduly traumatizing the joined layers of tissue. 
     Referring now to  FIG. 21B , an alternate embodiment of the presently disclosed operative tool is illustrated and referenced as  1106   a . Operative tool  1106   a  includes staple cartridge  1110 , as discussed above, in cooperation with anvil member  308 ′ that was discussed in detail with reference to  FIG. 11 . Anvil member  308 ′ includes tissue contacting surface  320 ′ having tapered surfaces  322 ′ and  324 ′. It is envisioned that the angle defined by tapered surfaces  322 ′ and  324 ′ will be substantially similar to the angle defined by tissue contacting surface  1120 , but in an opposed direction forming a generally V-shaped configuration. Thus, compressive forces applied to the layers of tissue will be further reduced thereby further reducing the trauma to layers of tissue disposed between tissue contacting surfaces  1120  and  320 ′. As in the previous embodiments, the maximum pressure applied to the layers of tissue will exist in the region near knife channel  1130  while pressures applied to the layers of tissue will decrease uniformly towards outer walls  1114 . Formation and location of surgical fasteners  125   a - c  is substantially similar to that of the embodiment of  FIG. 21A  along with the attendant advantages. 
     Further embodiments are illustrated in  FIGS. 22A-C  and discussed hereinbelow. Referring initially to  FIG. 22A , operative tool  1206   a  is illustrated and includes anvil member  308   d  and staple cartridge  1210 . In particular, staple cartridge  1210  includes surgical fasteners  125   a - c  and fastener ejection members  540  that were previously discussed in detail with respect to  FIG. 9A . Similar to previous embodiments, staple cartridge  1210  includes a bottom surface  1212 , outer walls  1214 , inner walls  1216 , and a knife channel  1230 . In addition, staple cartridge  1210  includes a tissue contacting surface  1220  formed from surfaces  1222  and  1224 . Each of surfaces  1222  and  1224  has a width dimension that is sufficient to accommodate at least one row of surgical fasteners. As shown in  FIG. 22A , surface  1222  is substantially parallel to bottom surface  1212 , while surface  1224  is a generally arcuate structure. Further still, the topmost portions of surfaces  1224  have substantially the same height dimension as measured from bottom surface  1212 . A complementary anvil member  308   d  is provided in operative tool  1206   a  wherein anvil member  308   d  includes a substantially planar surface  322   d  that corresponds to surfaces  1222  and knife channel  1230 . Additionally, anvil member  308   d  includes surfaces  324   d  that are generally arcuate so as to correspond to surfaces  1224  of staple cartridge  1210 . By providing this arrangement between staple cartridge  1210  and anvil member  308   d , a substantially uniform tissue gap is defined between the surfaces of anvil member  308   d  and staple cartridge  1210 . 
     Alternatively, operative tool  1206   b , as shown in  FIG. 22B , includes anvil member  308   e  in cooperation with staple cartridge  1210   a . Staple cartridge  1210   a  is substantially similar to staple cartridge  1210  ( FIG. 22A ) with the differences therebetween discussed below. Most notably, tissue contacting surface  1220   a  includes surfaces  1222   a ,  1224   a , and  1226   a . Surfaces  1222   a  and  1224   a  are substantially similar to surfaces  1222  and  1224  of  FIG. 22A , while surface  1226  is a generally arcuate structure having a lower height dimension that surface  1224  (i.e. with respect to bottom surface  1212 ). Thus, surfaces  1222 ,  1224 , and  1226  “step down” from the centerline towards outer walls  1214  of staple cartridge  1210   a . Anvil member  308   e  has a tissue contacting surface  320   e  that substantially complements tissue contacting surface  1220   a . As such, tissue contacting surface  320   e  includes a substantially planar surface  322   e  that corresponds to surfaces  1222   a  and knife channel  1230 . Additionally, anvil member  308   d  includes surfaces  324   e  and  326   e  that are generally arcuate so as to correspond to surfaces  1224   a  and  1226   a  of staple cartridge  1210   a . By providing this arrangement between staple cartridge  1210   a  and anvil member  308   e , a substantially uniform tissue gap is defined between the surfaces of anvil member  308   e  and staple cartridge  1210   a.    
     Alternatively, staple cartridge  1210   a  may be used in cooperation with anvil member  308  as shown in  FIG. 22C . In this configuration, the gap defined between tissue contacting surfaces  320  and  1220   b  increases from a first gap at knife channel  1230  to a second gap at outer walls  1214 , wherein the second gap is greater than the first gap. 
     All of the presently disclosed embodiments of the surgical stapling instrument provide a variable pressure gradient (i.e. load profile) to the layers of tissue that are joined together with the surgical fasteners. Therefore, the layers of tissue that are proximate to the center of the surgical stapling instrument (i.e. center of the staple cartridge) are subjected to higher compressive forces (i.e. loads), thereby forming thinner layers of tissue as compared to layers of tissue that are further away from the center of the surgical stapling instrument. Since the layers of tissue nearest the center of the surgical stapling instrument can be compressed more, a smaller sized surgical staple or fastener can be used to mechanically suture (i.e. fasten) the transected layers of tissue. Further still, providing a gradual compression gradient to the layers of tissue to be joined (see  FIG. 16B ), may result in a higher degree of hemostasis. Due to the contoured shape of the staple cartridge, the layers of tissue can be compressed more at the center of the surgical stapling instrument, because the layers of tissue can translate (i.e. move) from a region of relatively high pressure (i.e. at the center) to a region of relatively low pressure (i.e. at the edges) as the anvil member is moved relative to the staple cartridge, thereby defining the pressure gradient. 
     In addition, while each of the surgical stapling instruments described above and shown herein include tissue contacting surfaces having a stepped profile, it is envisioned that any of the surgical stapling instruments disclosed herein can have tissue contacting surfaces having any one of a number of profiles including and not limited to angles, conical, tapered, arcuate and the like, as disclosed in commonly assigned U.S. patent application Ser. No. 10/411,686, filed on May 11, 2003, entitled “Surgical Stapling Apparatus Including an Anvil and Cartridge Each Having Cooperating Mating Surfaces,” currently assigned to Tyco Healthcare Group LP, the entire contents of which is incorporated herein by reference. 
     It will be understood that various modifications may be made to the embodiments of the presently disclosed surgical stapling instruments. Therefore, the above description should not be construed as limiting, but merely as exemplifications of embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the present disclosure.