US20190261982A1 - Powered stapler having varying staple heights and sizes - Google Patents

Abstract

A loading unit of a powered surgical stapling instrument includes anvil and cartridge assemblies. The anvil assembly includes a first tissue contacting surface, and the cartridge assembly includes a second tissue contacting surface, a first plurality of staples, a second plurality of staples, and a plurality of pushers. The second tissue contacting surface defines a knife channel partitioning the second tissue contacting surface into first and second portions. Each of the first and second portions includes an inner tissue contacting surface and an outer tissue contacting surface. The inner tissue contacting surface defines a first row of retention slots. The inner tissue contacting surface and the first tissue contacting surface define a first tissue gap. The outer tissue contacting surface defines a second row of retention slots. The outer tissue contacting surface and the first tissue contacting surface define a second tissue gap larger than the first tissue gap.

Description

BACKGROUNDTechnical Field
• The present disclosure relates to surgical stapling instruments and, more particularly, to powered surgical stapling instruments including a loading unit configured to provide a variable pressure gradient to layers of tissue clamped between anvil and cartridge assemblies of the loading unit.
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. These surgical stapling instruments typically include a cartridge assembly and an anvil assembly. The cartridge assembly 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 assembly includes staple forming depressions which are aligned with and/or in registration with the staple slots in the cartridge assembly. In use, each of the surgical stapling instruments involves gripping of tissue to be fastened, ejecting individual staples from the cartridge assembly through the gripped tissue, and forming the staples against the staple forming depressions of the anvil assembly.
• A common issue in transecting tissue and/or in anastomosis procedures is achieving optimal balance between anastomotic strength and hemostasis. Therefore, a need exists for simple and effective powered surgical stapling instruments capable of improving the anastomotic strength and the degree of hemostasis when the layers of tissue are clamped and fastened between the anvil assembly and the cartridge assembly.
SUMMARY
• The present disclosure is directed towards powered surgical stapling instruments configured to effectuate an improved balance between the anastomotic strength and the degree of hemostasis at the tissue interface. There is provided a powered surgical stapling instrument in accordance with an embodiment of the present disclosure. The powered surgical stapling instrument includes a powered handle assembly, a powered adapter assembly releasably secured to the powered handle assembly, and a loading unit releasably secured to the powered adapter assembly. The loading unit includes an anvil assembly and a cartridge assembly movable relative to the anvil assembly between open and approximated positions. The anvil assembly includes a first tissue contacting surface. The cartridge assembly includes a second tissue contacting surface, a first plurality of staples, a second plurality of staples, and a plurality of pushers.
• The second tissue contacting surface defines a knife channel partitioning the second tissue contacting surface into first and second portions. The second tissue contacting surface is stepped. Each of the first and second portions includes an inner tissue contacting surface and an outer tissue contacting surface. The inner tissue contacting surface is disposed adjacent the knife channel. The inner tissue contacting surface defines a first row of retention slots. The inner tissue contacting surface and the first tissue contacting surface of the anvil assembly define a first tissue gap. The outer tissue contacting surface is disposed laterally outward of the respective inner tissue contacting surface and defines a second row of retention slots. The outer tissue contacting surface and the first tissue contacting surface of the anvil assembly define a second tissue gap larger than the first tissue gap.
• The first plurality of staples has a first unformed leg length. The first plurality of staples is disposed in the first row of retention slots. The second plurality of staples has a second unformed leg length longer than the first unformed leg length. The second plurality of staples is disposed in the second row of retention slots. Each pusher of the plurality of pushers includes first and second panels configured to eject respective one of the first plurality of staples and one of the second plurality of staples through the second tissue contacting surface of the cartridge assembly.
• In an embodiment, the first row of retention slots of the inner tissue contacting surface may be axially offset from the second row of retention slots of the outer tissue contacting surface.
• In another embodiment, the first panel may have a height longer than the second panel.
• In still another embodiment, each pusher of the plurality of pushers may further include a base panel interconnecting the first and second panels.
• In still another embodiment, each of the first and second portions of the second tissue contacting surface of the cartridge assembly may include a transitioning portion interconnecting the respective inner and outer tissue contacting surfaces.
• In yet another embodiment, the transitioning portion may define a slope configured to provide gradual compression on tissue when tissue is clamped between the anvil assembly and the cartridge assembly.
• In still yet another embodiment, the first tissue contacting surface of the anvil assembly may be planar.
• In still yet another embodiment, the first tissue contacting surface of the anvil assembly may define a longitudinal channel in registration with the knife channel of the cartridge assembly.
• In still yet another embodiment, the inner and outer tissue contacting surfaces of the first and second portions of the second tissue contacting surface of the cartridge assembly may be symmetric with respect to the knife channel of the cartridge assembly.
• In still yet another embodiment, the inner tissue contacting surfaces of the first and second portions of the second tissue contacting surface of the cartridge assembly may be coplanar. In addition, the outer tissue contacting surfaces of the first and second portions of the second tissue contacting surface of the cartridge assembly may be coplanar.
• In still yet another embodiment, the outer tissue contacting surfaces may be parallel to the inner tissue contacting surfaces.
• In still yet another embodiment, the second tissue contacting surface of the cartridge assembly and the first tissue contacting surfaces of the anvil assembly may define a varying tissue gap and may be configured to apply pressure to tissue disposed therebetween, wherein an amount of pressure applied to a portion of tissue disposed on the inner tissue contacting surface of the cartridge assembly is greater than an amount of pressure applied to a second portion of tissue disposed on the outer tissue contacting surface of the cartridge assembly.
• In accordance with another embodiment of the present disclosure, there is provided a powered surgical stapling instrument including a powered handle assembly, a powered adapter assembly releasably secured to the powered handle assembly, and a loading unit releasably secured to the powered adapter assembly. The loading unit including an anvil assembly and a cartridge assembly. The anvil assembly includes a planar anvil surface defining a plurality of staple-forming depressions. At least one of the anvil assembly or the cartridge assembly is movable relative to the other between an open position and a pre-fire position. The cartridge assembly includes a tissue contacting surface, a first plurality of unformed staples, and a second plurality of unformed staples. The tissue contacting surface defines a knife channel partitioning the tissue contacting surface into first and second portions. The tissue contacting surface is stepped. Each of the first and second portions includes a first tissue contacting surface and a second tissue contacting surface. The first tissue contacting surface includes a first plurality of staple retention slots. The first tissue contacting surface and the planar anvil surface are configured to apply a first pressure to tissue disposed therebetween in the pre-fire position. The second tissue contacting surface defines a second plurality of staple retention slots. The second tissue contacting surface and the planar anvil surface are configured to apply a second pressure to tissue disposed therebetween in the pre-fire position. The second pressure is less than the first pressure. The first plurality of unformed staples has a first leg length. The first plurality of unformed staples is configured to be ejected through the first plurality of staple retention slots and into engagement with the plurality of staple-forming depressions of the anvil assembly to form a first plurality of formed staples. The second plurality of unformed staples has a second leg length. The second plurality of unformed staples is configured to be ejected through the second plurality of staple retention slots and into engagement with the plurality of staple-forming depressions of the anvil assembly to form a second plurality of formed staples. The second leg length is longer than the first leg length.
BRIEF DESCRIPTION OF THE DRAWINGS
• The accompanying drawings illustrate embodiments of the disclosure and, together with a general description of the disclosure given above, and the detailed description of the embodiment(s) given below, serve to explain the principles of the disclosure, wherein:
• FIG. 1 is a perspective view of a powered surgical stapling instrument constructed in accordance with an exemplary embodiment of the present disclosure with a tool assembly in an open position;
• FIG. 2 is a perspective view of a loading unit of the powered surgical stapling instrument ofFIG. 1 with the tool assembly in an approximated position;
• FIG. 3 is a perspective view of the loading unit of the powered surgical stapling instrument ofFIG. 1;
• FIG. 4 is a partial, plan view of an anvil assembly of the loading unit ofFIG. 2;
• FIG. 5 is a partial, plan view of a cartridge assembly of the loading unit ofFIG. 2;
• FIG. 6 is an enlarged view of the indicated area detail ofFIG. 3;
• FIG. 7 is a cross-sectional view taken along section line7-7 ofFIG. 2;
• FIG. 8 is a perspective view of staples for use with the loading unit ofFIG. 2;
• FIG. 9 is a side view of a tissue/staple interface following a firing of a conventional surgical stapling instrument; and
• FIG. 10 is a side view of a tissue/staple interface following the firing of the powered surgical stapling instrument ofFIG. 1.
DETAILED DESCRIPTION OF EMBODIMENTS
• Embodiments of the present powered surgical stapling instruments will now be described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views. As used herein, the term “distal,” as is conventional, will refer to that portion of the instrument, apparatus, device or component thereof which is farther from the user while, the term “proximal,” will refer to that portion of the instrument, apparatus, device or component thereof which is closer to the user. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.
• With reference toFIG. 1, a powered surgical stapler in accordance with embodiments of the present disclosure is generally shown as asurgical stapler10.Surgical stapler10 includes apowered handle assembly12, apowered adapter assembly14 releasably secured topowered handle assembly12, and aloading unit100 releasably secured topowered adapter assembly14. Reference may be made to U.S. Pat. No. 9,055,943 (“the '943 Patent”) and U.S. Patent Application Publication No. 2016/0106406, the entire contents of each of which is incorporated herein by reference, for a detailed discussion of the construction and operation of exemplary powered handle and adapter assemblies. Alternatively, the device may be manually operated. Reference may be made to U.S. Patent Application Publication No. 2013/0098965, the entire contents of which is incorporated herein by reference, for a detailed discussion of the construction and operation of exemplary manually operated handle assemblies.
• With reference now toFIGS. 2 and 3,loading unit100 ofsurgical stapler10 includes abody portion102 and atool assembly104.Body portion102 is configured to be releasably coupled to powered adapter assembly14 (FIG. 1).Tool assembly104 includes ananvil assembly140 and acartridge assembly150 that is movable in relation toanvil assembly140 between open and approximated positions. A mountingassembly106 is provided to coupletool assembly104 tobody portion102 ofloading unit100. In embodiments, mounting assembly106couples tool assembly104 tobody portion102 to facilitate pivotal movement oftool assembly104 about an axis “T-T” transverse to a longitudinal axis “X-X” ofbody portion102.
• With reference toFIGS. 3 and 4,anvil assembly140 includes ananvil body142 and ananvil plate144 secured to the underside ofanvil body142. In embodiments,anvil plate144 includes a planartissue contacting surface144athat defines linear rows ofstaple forming depressions144b. Alternatively,tissue contacting surface144aofanvil plate144 may be stepped or curved.Anvil assembly140 may define alongitudinal slot145 configured to receive a knife blade157 (FIG. 7) therethrough.
• With reference now toFIGS. 5-7,cartridge assembly150 includes acartridge body154 and astaple cartridge152 that may be removably received incartridge body154.Staple cartridge152 includes atissue contacting surface161 configured to receive tissue thereon and defines aknife channel155 configured to slidably receive a knife blade157 (FIG. 7) and a drive beam (not shown).Knife channel155 extends throughtissue contacting surface161 ofstaple cartridge152 such thattissue contacting surface161 is partitioned into first andsecond portions161a,161b. First andsecond portions161a,161boftissue contacting surface161 include respective innertissue contacting surfaces163a,163bdisposedadjacent knife channel155, and outertissue contacting surfaces165a,165bdisposed laterally outward from the respective innertissue contacting surfaces163a,163b. In embodiments, innertissue contacting surfaces163a,163bare coplanar, and outertissue contacting surfaces165a,165bare coplanar.Knife channel155 may be centered ontissue contacting surface161 such that inner and outertissue contacting surfaces163a,163b,165a,165bon respective first andsecond portions161a,161bare symmetric with respect toknife channel155. In embodiments, in the approximated position oftool assembly104,tissue contacting surface144aofanvil assembly140 and innertissue contacting surfaces163a,163bofcartridge assembly150 define a first tissue gap G₁(FIG. 7), andtissue contacting surface144aofanvil assembly140 and outertissue contacting surfaces165a,165bofcartridge assembly150 define a second tissue gap G₂(FIG. 7) larger than first tissue gap G₁.
• With particular reference toFIG. 7,tissue contacting surface161 ofstaple cartridge152 further includestransition portions167a,167bthat interconnect the respective innertissue contacting surfaces163a,163band outertissue contacting surfaces165a,165b.Transition portions167a,167bare sloped to provide gradual transition of compression force on tissue when tissue is clamped betweenanvil assembly140 andcartridge assembly150. Moreover,transition portions167a,167adirect fluid within tissue to flow laterally outward away fromknife channel150 when tissue is clamped betweenanvil assembly140 andcartridge assembly150.
• In this arrangement, varying the size of tissue gaps betweentissue contacting surface161 ofcartridge assembly150 andtissue contacting surface144aofanvil assembly140 varies the amount of pressure applied to tissue disposed betweentissue contacting surface144aandtissue contacting surface161 along a plane that is transverse to a longitudinal axis “Y-Y” (FIG. 5) ofstaple cartridge152.
• With continued reference toFIGS. 6 and 7,staple cartridge152 defines a plurality ofstaple retention slots193a,193b,195a,195b(FIG. 6) extending throughtissue contacting surface161.Staple retention slots193a,193bare arranged in a linear fashion in respective innertissue contacting surfaces163a,163b, andstaple retention slots195a,195bare arranged in a linear fashion in respective outertissue contacting surfaces165a,165b. In this manner, two linear rows ofstaple retention slots193a,193b,195a,195bare provided on each side ofknife channel155 in first andsecond portions161a,161boftissue contacting surface161. While it is envisioned that one or more additional rows of staple retention slots may be provided ontissue contacting surface161, by providing two linear rows ofstaple retention slots193a,193b,195a,195bon each side ofknife channel155, the dimensions ofcartridge assembly150 andanvil assembly140 are minimized to facilitate insertion ofloading unit100 through a small diameter incision or cannula and reduce patient trauma.
• Staple retention slots193a,193bare axially offset from respectivestaple retention slots195a,195b.Staple retention slots193a,193b,195a,195bare in alignment withstaple receiving depressions144b(FIG. 4) defined inanvil plate144. Eachstaple retention slot193a,193b,195a,195bis dimensioned to receive a respective surgical staple S₁, S₂(FIG. 8) and a portion of apusher164. Surgical staples S₁, S₂are supported on respectivestaple pushers164 which are positioned to be engaged by a sled (not shown) such that longitudinal translation of the sled throughcartridge body154 urgespushers164 towards thetissue contacting surface161 ofstaple cartridge152 to eject surgical staples S₁, S₂out of respectivestaple retention slots193a,193b,195a,195b. See, e.g., U.S. Patent Application Publication No. 2013/0098965. If the closed or formed staple height is too high, then it may inadequately appose the tissues and result in leakage, bleeding, and/or dehiscence. Conversely, if the formed staple height is too low, then, e.g, ischemia or serosal shearing, may result, potentially leading to leakage or necrosis of tissue.
• With particular reference toFIGS. 6-8,staple retention slots193a,193bdefined in innertissue contacting surfaces163a,163breceive staple S₂having a leg length of H₂andstaple retention slots195a,195bdefined in outertissue contacting surfaces165a,165breceive staple S₁having a leg length of H₁longer than H₂. For example, H₁may be about 4.1 mm and H₂may be about 3.5 mm. Alternatively, H₁may be about 3.5 mm and H₂may be about 2.3 mm. It is contemplated that surgical staples S₁, S₂may be formed of a permanent or re-absorbable polymer. In addition, surgical staples S₁, S₂may be formed of different materials. It is also contemplated that a diameter of the staple wire may vary in order to improve securement of surgical staples S₁, S₂in tissue.
• With particular reference back toFIG. 7, eachpusher164 includes afirst panel164a, asecond panel164b, and abase panel164cinterconnecting first andsecond panels164a,164b.First panel164ais dimensioned to be received in a respectivestaple retention slot193a,193b, andsecond panel164bis dimensioned to be received in a respectivestaple retention slot195a,195b.First panel164ahas a height larger than a height ofsecond panel164bto accommodate shorter surgical staples S₂.
• The configuration oftissue contacting surface161 ofstaple cartridge152 causes a greater degree of compression to occur along innertissue contacting surface163a,163bofcartridge assembly150adjacent knife channel155. This greater degree of compression urges fluid stored in the layers of tissueadjacent knife channel155 to flow laterally outward fromknife channel155. By reducing the amount of fluid retained in the layers of tissue on innertissue contacting surface163a,163b, the overall thickness of the tissue layers decreases. The decrease in overall tissue thickness is such that surgical staple S₂having a shorter leg length H₂tightly fastens the layers of tissueadjacent knife channel155 to inhibit leakage from the fastened tissue. The tissue gap G₂increases towardsouter walls159 ofcartridge body154 as the amount of compression decreases, whereby surgical staples S₁having a longer leg length H₁less tightly fasten the layers of tissue on outertissue contacting surfaces165a,165b. The reduced compression and reduced tightness of the staples S₁outwardly of innertissue contacting surfaces163a,163ballows a minimal amount of blood to flow past staples S₁towards staples S₂to reduce the likelihood of necrosis of tissue adjacent staples S₁. By inhibiting necrosis of tissue adjacent staples S₁, the strength of the tissue and thus, the staple line is improved.
• In operation, after the layers of tissue are positioned betweentissue contacting surface161 ofcartridge assembly150 andtissue contacting surface144aofanvil assembly140, the actuation mechanism is actuated for sequentially ejecting surgical staples S₁, S₂through respectivestaple retention slots193a,193b,195a,195b, whereby interaction between surgical staples S₁, S₂andanvil assembly140 forms completed surgical staples for joining the layers of tissue. In particular, an actuation sled (not shown) is positioned within thecartridge body154 to pass longitudinally throughcartridge body154 into sequential engagement withpushers164 to sequentially eject staples S₁, S₂fromcartridge body154. Reference may be made to the '943 Patent and also to U.S. Pat. No. 6,202,914, the entire contents of which is also incorporated herein by reference, for a detailed discussion of the construction and operation of the actuation mechanism including the sled (not shown) andpushers164.
• Tissue contacting surface161 provides a variable pressure gradient (i.e. load profile) to tissue clamped betweenanvil assembly140 andcartridge assembly150. By providing a gradual compression gradient to the layers of tissue, a higher degree of hemostasis may be effected. The layers of tissue disposed on innertissue contacting surfaces163a,163bare subject to higher compressive forces, which, in turn, forms thinner layers of tissue as compared to layers of tissue disposed on outertissue contacting surfaces165a,165b. Since the layers of tissue on innertissue contacting surfaces163a,163bcan be compressed more, smaller sized surgical staple S₂are used to staple the transected layers of tissue. When the surgical staples S₁, S₂are deployed and formed in tissue, the smaller surgical staples S₂are disposed adjacent the cut line in the tissue. Surgical staples S₁, which are the larger staples, are disposed laterally outward of surgical staples S₂. This arrangement provides improved hemostasis in the portion of tissue having surgical staples S₂and further supports improved blood flow through tissue towards surgical staples S₂to inhibit necrosis of tissue supporting the formed staples S₂.
• With reference toFIGS. 9 and 10, when layers of tissue “A” and “B” are fastened using a conventional surgical stapler and conventional staples “S”, there exists a sharp transition from the un-fastened layers of tissue to the fastened layers of tissue (FIG. 9). 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, when layers of tissue “A” and “B” are fastened utilizingsurgical stapler10, the tissue interface has a substantially tapered profile (FIG. 10). The tissue interface has a gradual transition from the un-fastened layers of tissue to the fastened layers of tissue. This arrangement provides gradual tissue loading or compression due to the varying sizes of the formed surgical staples S₁, S₂, thereby minimizing tissue trauma while maintaining a relatively high degree of hemostasis and anastomotic strength.
• It is contemplated that to reduce and/or eliminate bleeding and leaks following a surgical stapling procedure,surgical stapler10 may further include a dispensing tissue reinforcement material, e.g., surgical glue or bio-cement, onto tissue simultaneously with and/or immediately following stapling and cutting of tissue. Incorporating a dispensing mechanism into the stapling assembly promotes uniform application of the glue over the staple line; eliminates the need for instrument exchange, thereby reducing surgical time; and/or enables an efficient use of sealant.
• Persons skilled in the art will understand that the structures and methods specifically described herein and shown in the accompanying figures are non-limiting exemplary embodiments, and that the description, disclosure, and figures should be construed merely as exemplary of particular embodiments. For example, the staple cartridge may have a single planar tissue contacting surface and the anvil member may be provided with tissue contacting surface varying in height so as to define more than one tissue gap with respect to the tissue contacting surface of the staple cartridge.
• It is to be understood, therefore, that the present disclosure is not limited to the precise embodiments described, and that various other changes and modifications may be effected by one skilled in the art without departing from the scope or spirit of the disclosure. Additionally, the elements and features shown or described in connection with certain embodiments may be combined with the elements and features of certain other embodiments without departing from the scope of the present disclosure, and that such modifications and variations are also included within the scope of the present disclosure. Accordingly, the subject matter of the present disclosure is not limited by what has been particularly shown and described.

Claims (22)

What is claimed is:

1. A powered surgical stapling instrument comprising:

a powered handle assembly;

a powered adapter assembly releasably secured to the powered handle assembly; and

a loading unit releasably secured to the powered adapter assembly, the loading unit including:

an anvil assembly including a first tissue contacting surface; and

a cartridge assembly movable relative to the anvil assembly between open and approximated positions, the cartridge assembly including:

a second tissue contacting surface defining a knife channel, the second tissue contacting surface being stepped, the knife channel partitioning the second tissue contacting surface into first and second portions, each of the first and second portions including:

an inner tissue contacting surface disposed adjacent the knife channel and defining a first row of retention slots, the inner tissue contacting surface and the first tissue contacting surface of the anvil assembly defining a first tissue gap; and

an outer tissue contacting surface disposed laterally outward of the respective inner tissue contacting surface and defining a second row of retention slots, the outer tissue contacting surface and the first tissue contacting surface of the anvil assembly defining a second tissue gap larger than the first tissue gap;

a first plurality of staples having a first unformed leg length, the first plurality of staples disposed in the first row of retention slots;

a second plurality of staples having a second unformed leg length longer than the first unformed leg length, the second plurality of staples disposed in the second row of retention slots; and

a plurality of pushers, each pusher of the plurality of pushers including first and second panels, the first and second panels configured to eject respective one of the first plurality of staples and one of the second plurality of staples through the second tissue contacting surface of the cartridge assembly.

2. The powered surgical stapling instrument according toclaim 1, wherein the first row of retention slots of the inner tissue contacting surface is axially offset from the second row of retention slots of the outer tissue contacting surface.

3. The powered surgical stapling instrument according toclaim 1, wherein the first panel has a height longer than the second panel.

4. The powered surgical stapling instrument according toclaim 1, wherein each pusher of the plurality of pushers further includes a base panel interconnecting the first and second panels.

5. The powered surgical stapling instrument according toclaim 1, wherein each of the first and second portions of the second tissue contacting surface of the cartridge assembly includes a transitioning portion interconnecting the respective inner and outer tissue contacting surfaces.

6. The powered surgical stapling instrument according toclaim 5, wherein the transitioning portion defines a slope configured to provide gradual compression on tissue when tissue is clamped between the anvil assembly and the cartridge assembly.

7. The powered surgical stapling instrument according toclaim 1, wherein the first tissue contacting surface of the anvil assembly is planar.

8. The powered surgical stapling instrument according toclaim 7, wherein the first tissue contacting surface of the anvil assembly defines a longitudinal channel in registration with the knife channel of the cartridge assembly.

9. The powered surgical stapling instrument according toclaim 1, wherein the inner and outer tissue contacting surfaces of the first and second portions of the second tissue contacting surface of the cartridge assembly are symmetric with respect to the knife channel of the cartridge assembly.

10. The powered surgical stapling instrument according toclaim 1, wherein the inner tissue contacting surfaces of the first and second portions of the second tissue contacting surface of the cartridge assembly are coplanar.

11. The powered surgical stapling instrument according toclaim 1, wherein the outer tissue contacting surfaces of the first and second portions of the second tissue contacting surface of the cartridge assembly are coplanar.

12. The powered surgical stapling instrument according toclaim 1, wherein the outer tissue contacting surfaces are parallel to the inner tissue contacting surfaces.

13. The powered surgical stapling instrument according toclaim 1, wherein the second tissue contacting surface of the cartridge assembly and the first tissue contacting surface of the anvil assembly define a varying tissue gap and are configured to apply pressure to tissue disposed therebetween, wherein an amount of pressure applied to a portion of tissue disposed on the inner tissue contacting surface of the cartridge assembly is greater than an amount of pressure applied to a second portion of tissue disposed on the outer tissue contacting surface of the cartridge assembly.

14. A powered surgical stapling instrument comprising:

a powered handle assembly;

a powered adapter assembly releasably secured to the powered handle assembly; and

a loading unit releasably secured to the powered adapter assembly, the loading unit including:

an anvil assembly including a planar anvil surface defining a plurality of staple-forming depressions; and

a cartridge assembly, at least one of the anvil assembly or the cartridge assembly movable relative to the other between an open position and a pre-fire position, the cartridge assembly including:

a tissue contacting surface defining a knife channel, the tissue contacting surface being stepped, the knife channel partitioning the tissue contacting surface into first and second portions, each of the first and second portions including a first tissue contacting surface and a second tissue contacting surface, the first tissue contacting surface including a first plurality of staple retention slots, the first tissue contacting surface and the planar anvil surface configured to apply a first pressure to tissue disposed therebetween in the pre-fire position, the second tissue contacting surface defining a second plurality of staple retention slots, the second tissue contacting surface and the planar anvil surface configured to apply a second pressure to tissue disposed therebetween in the pre-fire position, the second pressure being less than the first pressure;

a first plurality of unformed staples having a first leg length, the first plurality of unformed staples configured to be ejected through the first plurality of staple retention slots and into engagement with the plurality of staple-forming depressions of the anvil assembly to form a first plurality of formed staples; and

a second plurality of unformed staples having a second leg length, the second plurality of unformed staples configured to be ejected through the second plurality of staple retention slots and into engagement with the plurality of staple-forming depressions of the anvil assembly to form a second plurality of formed staples, the second leg length being longer than the first leg length.

15. The powered surgical stapling instrument according toclaim 14, wherein the first plurality of staple retention slots are arranged in a linear row.

16. The powered surgical stapling instrument according toclaim 15, wherein the second plurality of staple retention slots are arranged in a linear row.

17. The powered surgical stapling instrument according toclaim 14, wherein the first tissue contacting surfaces are disposed adjacent the knife channel.

18. The powered surgical stapling instrument according toclaim 14, wherein the second tissue contacting surfaces are disposed laterally outward of the respective first tissue contacting surfaces.

19. The powered surgical stapling instrument according toclaim 14, wherein each of the first and second portions of the tissue contacting surface of the cartridge assembly includes a transition panel interconnecting the respective first and second tissue contacting surfaces.

20. The powered surgical stapling instrument according toclaim 14, further comprising a plurality of pushers, each pusher including first and second panels configured to engage respective one of the first plurality of unformed staples and one of the second plurality of unformed staples.

21. The powered surgical stapling instrument according toclaim 20, wherein each pusher includes a base panel interconnecting the first and second panels.

22. The powered surgical stapling instrument according toclaim 20, wherein the first panel has a length longer than the second panel.

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