Methods and devices for performing a surgical anastomosis

[0001] The present application is a Divisional Application which claims that benefit of and priority to U.S. patent application Ser. No. 13/939,684, filed on Jul. 11, 2013, the entire content of which is incorporated herein by reference.

[0002] The present disclosure relates generally to a surgical stapling device for applying surgical staples to body tissue. More particularly, the present disclosure relates to a surgical stapling device suitable for performing circular anastomosis and/or treatment to internal walls of hollow tissue organs.

[0003] Anastomosis is the surgical joining of separate hollow organ sections. Typically, an anastomosis procedure follows surgery in which a diseased or defective section of hollow tissue is removed and the remaining end sections are to be joined. Depending on the desired anastomosis procedure, the end sections may be joined by either circular, end-to-end, or side-to-side organ reconstruction methods.

[0004] In a circular anastomosis procedure, the two ends of the organ sections are joined by means of a stapling instrument which drives a circular array of staples through the end section of each organ section and simultaneously cores any tissue interior of the driven circular array of staples to free the tubular passage. Examples of instruments for performing circular anastomosis of hollow organs are described in U.S. Pat. Nos. 6,053,390, 5,588,579, 5,119,983, 5,005,749, 4,646,745, 4,576,167, and 4,473,077, each of which is incorporated herein in its entirety by reference. Typically, these instruments include an elongated shaft having a handle portion at a proximal end to actuate the instrument and a staple holding component disposed at a distal end. An anvil assembly including an anvil rod with attached anvil head is mounted to the distal end of the instrument adjacent the staple holding component. Opposed end portions of tissue of the hollow organ(s) to be stapled are clamped between the anvil head and the staple holding component. The clamped tissue is stapled by driving one or more staples from the staple holding component so that the ends of the staples pass through the tissue and are deformed by the anvil head. An annular knife is advanced to core tissue within the hollow organ to free a tubular passage within the organ. Generally, both the actuation of the staple forming mechanism and the advancement of the knife occur at the same time, i.e., simultaneously.

[0005] Besides anastomosis of hollow organs, surgical stapling devices for performing circular anastomosis have been used to treat internal hemorrhoids in the rectum. Typically, during use of a circular stapling device for hemorrhoid treatment, the anvil head and the staple holding component of the surgical stapling device are inserted through the anus and into the rectum with the anvil head and the staple holding component in an open or unapproximated position. Thereafter, a pursestring suture is used to pull the internal hemorrhoidal tissue towards the anvil rod. Next, the anvil head and the staple holding component are approximated to clamp the hemorrhoid tissue between the anvil head and the staple holding component. The stapling device is fired to remove the hemorrhoidal tissue and staple the cut tissue.

[0006] The present disclosure relates to a circular stapler comprising a handle assembly, an elongate body, and a cartridge assembly. The elongate body extends from the handle assembly and defines a longitudinal axis. The cartridge assembly is disposed adjacent a distal end of the elongate body. The cartridge assembly includes a pusher assembly and a knife assembly. The pusher assembly is movable to cause staples to be ejected from the cartridge assembly. The knife assembly is selectively movable relative to the pusher assembly to distally translate a knife. A knife carrier of the knife assembly includes at least one latch thereon. The at least one latch is configured to contact an engagement surface of the pusher assembly in response to movement between the knife carrier and the pusher assembly. The at least one latch is prevented from distally translating beyond the engagement surface.

[0007] In disclosed embodiments, the at least one latch of the knife carrier is included on a proximal end of a flexible arm, and the flexible arm is configured to flex toward the longitudinal axis. The knife carrier is configured to be assembled with the pusher assembly by moving the knife carrier in a distal-to-proximal direction through a passage extending through the pusher assembly.

[0008] In disclosed embodiments, a proximal portion of knife carrier includes an annular groove. The annular groove is configured to engage a drive member. The annular groove is positioned farther proximally than an entirety of the at least one arm and the at least one latch. A proximal portion of the at least one latch includes a ramped surface, and a distal portion of the at least one latch includes a surface that is substantially perpendicular to the longitudinal axis.

[0009] The present disclosure also relates to a circular stapler comprising a handle assembly, an elongate body extending from the handle assembly and defining a longitudinal axis, a drive member, and a cartridge assembly. The drive member is configured for longitudinal translation in response to actuation of handle assembly, and includes a recess disposed adjacent a distal portion thereof. The cartridge assembly is disposed adjacent a distal end of the elongate body, and includes a pusher assembly. The pusher assembly is configured to mechanically engage a portion of the drive member and is longitudinally translatable to cause staples to be ejected from the cartridge assembly. The pusher assembly includes at least one finger with the at least one finger including a tab. The at least one tab is configured to engage the recess of the drive member in response to relative approximation between the drive member and the pusher assembly.

[0010] In disclosed embodiments, a distal wall of the at least one tab forms an angle α1 with respect to the longitudinal axis, and wherein α1 is between about 70° and about 80°. Here, it is disclosed that a distal wall of the recess forms an angle α2 with respect to the longitudinal axis, and wherein α2 is between about 70° and about 80°. It is further envisioned that α1 is between about 75° and about 78°.

[0011] In disclosed embodiments, the at least one finger is configured to flex toward the longitudinal axis to facilitate engagement between the drive member and the pusher assembly.

[0012] In disclosed embodiments, a height of the at least one tab in a direction substantially perpendicular to the longitudinal axis is between about 0.010 inches and about 0.020 inches. It is envisioned that the height of the at least one tab is approximately equal to 0.015 inches. It is further disclosed that a depth of the recess portion in a direction substantially perpendicular to the longitudinal axis is between about 0.010 inches and about 0.020 inches.

[0013] In disclosed embodiments, at least a portion of the pusher assembly comprises glass-filled polycarbonate. The percentage of glass in the glass-filled polycarbonate of the pusher assembly is between about 20% and about 40%.

[0014] In disclosed embodiments, the circular stapler further comprises a knife assembly which is selectively movable relative to the pusher assembly to distally translate a knife.

[0015] In disclosed embodiments, the handle assembly is configured to receive power from a power source. The circular stapler comprises a communication chip disposed in mechanical cooperation with the cartridge assembly. The communication chip is configured to communicate information to and from other portions of the circular stapler.

[0016] The present disclosure also relates to an anvil assembly for use with a circular stapler. The anvil assembly comprises an anvil head and a cutting ring. The anvil head includes a plurality of staple-deforming pockets and an annular cavity. The anvil head includes a groove disposed along an inner annular surface thereof. The cutting ring is configured for reception at least partially within the annular cavity, and includes at least one tab extending radially outwardly from an outer wall thereof. The at least one tab is configured to engage the groove of the anvil head to help maintain at least a portion of the cutting ring at least partially within the cavity.

[0017] In disclosed embodiments, the cutting ring includes an outer ring, an inner ring, an annular knife channel disposed between the outer ring and the inner ring, and a severable portion disposed proximally-adjacent the knife channel. The severable portion is configured to be cut by a knife during typical use of the circular stapler.

[0018] The at least one tab includes a proximal surface and a distal surface. The proximal surface of the at least one tab is substantially perpendicular to an annular wall of the cutting ring, and the distal surface of the at least one tab is disposed at an angle with respect to the annular wall of the cutting ring and with respect to the proximal surface of the at least one tab. Here, it is disclosed that the cutting ring is configured to be inserted into the annular cavity of the anvil head in a proximal-to-distal direction such that the distal surface of the at least one tab contacts a portion of the anvil head and causes the cutting ring to deflect radially inward to allow the at least one tab to extend distally beyond a lip formed by a proximal surface of the groove. It is further disclosed that the proximal surface of the at least one tab is configured to engage the lip of the groove.

[0019] The cutting ring may comprise polyethylene.

[0020] In disclosed embodiments, the at least one tab is configured to engage the groove of the anvil head to help maintain at least a portion of the cutting ring at least partially within the cavity after a knife of the circular stapler has been advanced, and after a portion of the cutting ring as been severed by the knife.

[0021] The present disclosure contemplates a shell assembly for use with a circular stapler. The shell assembly comprises a housing and a staple cartridge. The housing includes an aperture defining a proximal wall and a distal wall, the defines a longitudinal axis extending therethrough. The staple cartridge is configured to house a plurality of staples at least partially therein, and includes at least one tab configured to mechanically engage the distal wall of the aperture. The at least one tab is configured to flex toward the longitudinal axis to facilitate assembly between the housing and the staple cartridge.

[0022] In disclosed embodiments, a proximal surface of the at least one tab is disposed at an angle with respect to the longitudinal axis.

[0023] In disclosed embodiments, a distal surface of the at least one tab includes a first surface that is substantially perpendicular to the longitudinal axis. Here, it is disclosed that the distal surface of the at least one tab includes a second surface that is disposed at an angle with respect to the first surface and with respect to the longitudinal axis. It is further disclosed that the first surface is disposed radially outward of the second surface. It is further disclosed that a radially inward-most point of the distal surface is the proximal-most point of the distal surface. Additionally, it is disclosed that the distal wall of the aperture includes a first surface that is substantially perpendicular to the longitudinal axis, and a second surface that is disposed at an angle with respect to the first surface and with respect to the longitudinal axis.

[0024] In disclosed embodiments, the shell assembly further comprises a cylindrical sleeve positionable adjacent a distal portion of the housing. The sleeve is configured to cover the aperture of the housing and the at least one tab of the staple cartridge. Here, it is disclosed that at least a portion of the sleeve comprises plastic.

[0025] The present disclosure also relates to a shell assembly kit for use with a circular stapler. The shell assembly kit comprises a first staple cartridge, a second staple cartridge, a first anvil assembly and a second anvil assembly. The first staple cartridge is configured to house two rows of staples, and includes a first trocar disposed in mechanical cooperation therewith. The second staple cartridge is configured to house three rows of staples, and includes a second trocar disposed in mechanical cooperation therewith. The first anvil assembly includes two rows of staple deforming pockets, and a first retention rod configured to mechanically engage the first trocar. The second anvil assembly includes three rows of staple deforming pockets, and includes a second retention rod configured to mechanically engage the second trocar. The first trocar is physically prevented from properly engaging the second retention rod, and the second trocar is physically prevented from properly engaging the first retention rod.

[0026] In disclosed embodiments, the first trocar includes at least one indicator that is perceptible by a user when the first trocar is improperly engaged with the second retention rod. The at least one indicator is not perceptible by a user when the first trocar is properly engaged with the first retention rod.

[0027] In disclosed embodiments, the first retention rod includes a recess that is configured to engage a lip of the first trocar, and the second retention rod includes a recess that is configured to engage a lip of the second trocar. Here, it is disclosed that the first retention rod includes a larger diameter than a corresponding diameter of the second retention rod. It is further disclosed that a distance between the recess and a proximal lip of the first retention rod is less than a distance between the recess and a proximal lip of the second retention rod.

[0028] In disclosed embodiments, a tissue-contacting portion of the first retention rod is tapered along its entire length. Here, it is disclosed that an anvil head of the first anvil assembly is tiltable with respect to the first retention rod.

[0070] Embodiments of the presently disclosed surgical stapling instrument will now be described in detail with reference to the drawings wherein like numerals designate identical or corresponding elements in each of the several views. As is common in the art, the term “proximal” refers to that part or component closer to the user or operator, i.e. surgeon or physician, while the term “distal” refers to that part or component farther away from the user.

[0071] FIG. 1 illustrates an embodiment of a surgical stapling instrument according to the present disclosure, referenced generally as circular stapler 10. Circular stapler 10 includes a handle assembly 20, an elongated body portion 30 extending distally from handle assembly 20, and a shell assembly 100 mounted adjacent a distal end of elongated body portion 30. Handle assembly 20 includes a fixed handle 22 and a moveable handle or trigger 24. Handle assembly 20 also includes an approximation knob 26 for moving an anvil assembly 105 relative to a cartridge assembly 110 of shell assembly 100. The structure and function of handle assembly 20 will only be described herein to the extent necessary to fully disclose the operation of shell assembly 100. It is envisioned that shell assembly 100 may be used with any actuation assembly, powered or manual, and capable of two independent actuation strokes, for example. Commonly owned U.S. patent application Ser. No. 12/946,082, filed Nov. 15, 2010, the content of which is incorporated by reference herein in its entirety, discloses a surgical device having a powered actuator assembly including first and second drive members. In addition, it is envisioned that the independent actuation strokes may be completed by the same drive member completing two strokes or by two separate drive members.

[0072] With reference to FIG. 2, cartridge assembly 110 is shown, and is operably mounted to a distal end of elongated body portion 30 of circular stapler 10 (FIG. 1). In disclosed embodiments, cartridge assembly 110 is removably secured to elongated body portion 30 such that cartridge assembly 110, or a portion thereof, may be replaced and circular stapler 10 may be reused. In other embodiments, only a portion of cartridge assembly 110 is configured to be removed, and subsequently replaced or reloaded. Alternatively, circular stapler 10 may be configured for a single use, i.e., disposable.

[0073] With reference to FIGS. 2 and 3, cartridge assembly 110 includes a housing 120, a pusher assembly 530, a staple cartridge 150, and a knife assembly 400. Housing 120 of cartridge assembly 110 includes an outer cylindrical portion 122, an inner cylindrical body 124 and a plurality of radially extending supports or ribs (not shown) extending between and interconnecting inner cylindrical portion 124 and outer cylindrical portion 122. Inner cylindrical portion 124 and outer cylindrical portion 122 are coaxial and define a recess 123 therebetween configured to receive a distal portion of pusher assembly 530 and knife assembly 400.

[0074] Knife assembly 400 includes a knife carrier 420 and a circular knife 440. Knife 440 is a substantially cylindrical member having a proximal end 442, a distal end 444, and defines a longitudinal opening 443 therethrough. Knife 440 is sized and configured to be received through recess 123 of staple cartridge 150. Distal end 444 of knife 440 is configured for cutting tissue. Proximal end 442 of knife 440 is configured to be received about a distal portion 424 of knife carrier 420 and includes a pair of opposed tabs 446 configured to be received within respective recesses 421 formed in distal portion 424 of knife carrier 420.

[0075] A proximal portion 422 of knife carrier 420 defines an annular groove 463 configured to accommodate snap ring 180 when snap ring 180 is in either a first or compressed condition or in a second or expanded condition. When circular stapler 10 is in the first or initial position, and prior to retraction of pusher adapter 532 following the first stroke of circular stapler 10, snap ring 180 is received completely within annular groove 463 formed in knife carrier 420. Proximal portion 422 of knife carrier 420 further defines a step 462a formed in or adjacent annular groove 463. Step 462a is configured to engage an inner annular portion of snap ring 180 when snap ring 180 is in the second or expanded condition. Further, engagement of snap ring 180 with step 462a prevents radial compression of snap ring 180 during the second or tissue cutting stroke. Further details of snap ring 180 and its engagement with knife carrier 420 are described in U.S. patent application Ser. No. 13/739,246 filed on Jan. 11, 2013, the entire contents of which being incorporated by reference herein.

[0076] With continued reference to FIGS. 2 and 3, a proximal end 122a of outer cylindrical portion 122 of housing 120 includes a plurality of tabs 125 formed thereon configured to operably engage cartridge assembly 110 with a distal end of elongated body portion 30 (FIG. 1). Outer cylindrical portion 122 of housing 120 further defines a plurality of openings 129. As will be discussed in further detail below, each of the plurality of openings 129 is configured to engage a pair of a plurality of detents 538a, 538b formed on a distal portion 534 of a pusher adapter 532.

[0077] With reference now to FIG. 3, pusher assembly 530 includes pusher adapter 532 and a pusher member 540. Pusher adapter 532 is a substantially cylindrical member having a proximal portion 532a and a distal portion 534. Proximal portion 532a of pusher adapter 532 is configured for operable engagement with a drive member 800 (e.g., see the embodiment disclosed in FIGS. 35-39). Distal portion 534 of pusher adapter 532 is configured to operably engage pusher member 540. As will be discussed in further detail below, pusher member 540 is not securely affixed to pusher adapter 532, such that pusher member 540 remains in an advanced position during the retraction of pusher adapter 532 following the first or stapling stroke of circular stapler 10. In this manner, the force required to move pusher adapter 532 during the second or tissue cutting stroke of circular stapler 10 does not include the force necessary to move pusher member 540.

[0078] With continued reference to FIG. 3, pusher adapter 532 defines a longitudinal passage 531 extending therethrough. A distal end of longitudinal passage 531 is sized and configured to receive knife assembly 400 in a sliding manner. Pusher adapter 532 further defines a plurality of longitudinal slots 533 extending along a length thereof. Slots 533 correspond in size and location to the supports (not shown) formed between and interconnecting outer and inner cylindrical portions 122, 124 in housing 120. Pusher adapter 532 is configured to be received within outer cylindrical portion 122 of housing 120 and about inner cylindrical portion 124 of housing 120. In this manner, slots 533 receive the respective supports of housing 120 such that inner cylindrical portion 124 of housing 120 may be received within longitudinal passage 531 of pusher adapter 532. A plurality of recesses 535a are formed in a distal surface 534a of pusher adapter 532 and are configured to engage tabs (not shown) formed on a proximal-facing surface of pusher member 540 (e.g., to ensure radial alignment during the firing stroke). As discussed above, pusher adapter 532 includes a plurality of paired detents 538a, 538b configured to be selectively received within openings 129 formed in outer cylindrical portion 122 of housing 120.

[0079] With continued reference to FIG. 3, pusher member 540 includes a proximal portion 542 and a distal portion 544. Proximal portion 542 of pusher member 540 defines a plurality of tabs (not shown) configured to be selectively received within the plurality of recesses 535a formed on distal surface 534a of pusher adapter 532. Distal portion 544 of pusher member 540 includes a plurality of pusher elements 546 extending distally therefrom and arranged in three concentric rows. Pusher elements 546 align with staples “S” received within staple cartridge 150 such that advancement of pusher member 540 relative to staple cartridge 150 causes ejection of staples “S” from staple cartridge 150. A notch 535 formed in distal portion 534 of pusher adapter 532 is configured to receive an outer annular portion of snap ring 180 of knife assembly 400, and a ledge 536 of pusher adapter 532 is configured to engage the outer annular portion of snap ring 180 during the second or cutting stroke of circular stapler 10. Additionally, tabs 536a are configured to retain snap ring 180 in engagement within distal portion 534 of pusher adapter 532.

[0080] With reference to FIGS. 2 and 3, staple cartridge 150 is a substantially cylindrical member configured to operably engage distal end 122b of outer cylindrical portion 122 of housing 120 and defines a longitudinal opening 151. Staple cartridge 150 includes a plurality of staple receiving pockets 152 disposed about opening 151 arranged in three concentric rows. Staple receiving pockets 152 align with pusher elements 546 formed on distal portion 544 of pusher member 540.

[0081] With reference to FIG. 4-8, the engagement between housing 120 and staple cartridge 150 is illustrated. Housing 120 and staple cartridge 150 are configured to mechanically engage each other prior to use of circular stapler 10 (e.g., during assembly). In this embodiment, housing 120 is engagable with staple cartridge 150 via a mechanical interface. More particularly, housing 120 includes at least one aperture 200 that is engagable with at least one tab 300 on staple cartridge 150.

[0082] Tabs 300 on staple cartridge 150 are inwardly flexible (with respect to a longitudinal axis A-A defined by elongated body portion 30) to facilitate assembly. Tabs 300 include a ramped proximal surface 302, and a distal surface 304 (FIG. 8). It is envisioned that distal surface 304 includes a substantially perpendicular surface 306 (with respect to longitudinal axis A-A), a ramped surface 308, or a combination thereof. In the illustrated embodiment (see FIG. 8, for example), distal surface 304 of tab 300 includes a perpendicular surface 306 and a ramped surface 308. Ramped surface 308 is angled such that the portion closer to the longitudinal axis A-A is disposed proximally of the portion of ramped surface 308 that is farther from the longitudinal axis A-A. It is envisioned that staple cartridge 150 includes any number of tabs 300.

[0083] Apertures 200 on housing 120 are dimensioned and positioned for mechanical engagement with tabs 300. It is envisioned that housing 120 includes any number of apertures 200. It is further envisioned that the number of apertures 200 is equal to or unequal to the number of tabs 300. Additionally, it is disclosed that the dimensions and/or orientation of tabs 300 and apertures 200 only allow engagement therebetween in a single radial orientation (e.g., for mistake-proof assembly). It is envisioned that a distal wall 202 of aperture 200 includes a substantially perpendicular surface 204 (with respect to longitudinal axis A-A), a ramped surface 206, or a combination thereof. In the illustrated embodiment (see FIG. 8, for example), distal wall 202 of aperture 200 includes a perpendicular surface 204 and a ramped surface 206. Ramped surface 206 is angled such that the portion closer to the longitudinal axis A-A is disposed proximally of the portion of ramped surface 206 that is farther from the longitudinal axis A-A. As shown, the orientation of distal wall 202 of aperture 200 is complementary to the orientation of distal surface 304 of tab 300.

[0084] It is envisioned that the complementary surfaces of distal wall 202 and distal surface 304, including ramped surfaces 206 and 308, respectively, help provide improved retention between housing 120 and staple cartridge 150. In this embodiment, a greater force (e.g., in the substantial direction of arrow “F” in FIG. 8) would be required to disengage staple cartridge 150 from outer housing 120 with respect to an embodiment where distal surface 304 of tab 300 and distal wall 202 of aperture 200 do not include ramped surfaces 308 and 206, respectively.

[0085] In the illustrated embodiment, housing 120 also includes a plurality of longitudinal slots 220, with one slot 220 being disposed on each side of each aperture 200. Slots 220 extend proximally from a distal edge 222 of housing 120. It is envisioned that slots 220 enable radially outward flexing of the portion of housing 120 surrounding apertures 200 to facilitate the mechanical engagement between housing 120 and staple cartridge 150. As can be appreciated, to mechanically engage housing 120 and staple cartridge 150, the two components are approximated such that the portion of housing 120 surrounding apertures 200 flexes radially outward to allow tabs 300 of staple cartridge 150 to enter apertures 200. After tabs 300 are within respective apertures 200, the portion of housing 120 surrounding apertures 200 flexes radially inward to effectively lock housing 120 and staple cartridge 150 together.

[0086] It is envisioned that the mechanical engagement between housing 120 and staple cartridge 150 is the only type of engagement therebetween. For example, the mechanical engagement eliminates the need for adhesives between the two components or welding the components together.

[0087] With reference to FIGS. 9 and 10, the present disclosure includes a label (e.g., an adhesive label) or sleeve (e.g., a shrink sleeve) 350. Sleeve 350 is positionable adjacent a distal portion of housing 120 and is configured to cover apertures 200, slots 220 and tabs 300 (see FIG. 5). The use of sleeve 350 helps ensure tissue does not because trapped or pinched within apertures 200, slots 220 or tabs 300, and also helps limit radially outward movement of tabs 300 with regard to apertures 200 during insertion of housing 120 into tissue, for example.

[0088] Additionally, it is envisioned that sleeve 350 can include information (e.g., indicia or a color) relating to lumen and/or staple size of the stapling instrument, for example. It is envisioned that the circumference of sleeve 350 is equal to or larger than the circumference of the distal portion of housing 120. In the embodiments where sleeve 350 has a larger circumference, an overlapping portion of sleeve 350 will cover the longitudinal seam between sleeve 350 and housing 120. It is envisioned that sleeve 350 is made from plastic (e.g., polyvinyl chloride (PVC), polyethylene terephthalate (PET), polypropylene, etc.) or another suitable material.

[0089] With reference to FIGS. 11-21, the engagement between pusher adapter 532 and knife carrier 420 is shown. With particular reference to FIGS. 12 and 13, proximal portion 422 of knife carrier 420 includes a plurality of latches 426, which are each configured to mechanically engage an engagement surface 550 (e.g., an undercut surface) of pusher adapter 532 upon a predetermined amount of longitudinal translation of knife carrier 420 with respect to pusher adapter 532. As can be appreciated, the engagement between latches 426 and engagement surfaces 550 prevent or substantially prevent portions of knife carrier 420 from translating distally beyond portions of pusher adapter 532.

[0090] More particularly, latches 426 of knife carrier 420 are disposed at a proximal end of flexible arms 428. Arms 428 are configured to deflect toward a radial center of knife carrier 420 to facilitate engagement/assembly between knife carrier 420 and pusher adapter 532. Further, to assemble knife carrier 420 and pusher adapter 532, knife carrier 420 is inserted in a proximal direction through a distal opening 560 of pusher adapter 532 until a ramped surface 430 of latches 426 contacts an angled surface 562 of an interior wall of pusher adapter 532. The contact between ramped surfaces 430 and angled surface 562, in combination with the proximal movement of knife carrier 420 with respect to pusher adapter 532, causes arms 428 to deflect radially inwardly, which allows a distal wall 426a of latches 426 to move proximally beyond engagement surfaces 550 of pusher adapter 532. Once in this position, arms 428 deflect radially outwardly (e.g., towards their biased position) such that distal walls 426a of latches 426 are physically prevented by engagement surfaces 550 of pusher adapter 532 from longitudinally translating distally therepast (see FIGS. 16 and 17). It is further envisioned that distal walls 426a of latches 426 include a ramped surface (e.g., the proximal portion of the ramped surface being closest to the radial center of knife carrier 420), and that engagement surfaces 550 of pusher adapter 532 include a complementary surface.

[0091] Referring now to FIGS. 16-21, the relative movement between pusher adapter 532, knife carrier 420 and housing 120 is depicted. FIG. 16 illustrates pusher adapter 532 and knife carrier 420 in a retracted position. As shown in FIG. 17 (which is an enlarged view of a portion of FIG. 16), the orientation of latches 426 and engagement surfaces 550 limit the amount of distal travel of knife carrier 420 with respect to pusher adapter 532. As can be appreciated, this orientation prevents a user from cutting tissue prior to the tissue being stapled. FIG. 18 illustrates pusher adapter 532 in an advanced position, and knife carrier 420 in its retracted position (e.g., in response to a first actuation stroke to staple tissue). FIG. 19 illustrates pusher adapter 532 in its advanced position, and knife carrier 420 in an advanced position (e.g., in response to a second actuation stroke to cut tissue). As shown in FIG. 20 (which is an enlarged view of a portion of FIG. 19), the engagement between latches 426 and engagement surfaces 550 prevent additional distal travel of knife carrier 420 with respect to pusher adapter 532. FIG. 21 illustrates pusher adapter 532 in its advanced position, and knife carrier 420 in its retracted position (e.g., after tissue has been cut). As can be appreciated, that fact that pusher adapter 532 remains in its advanced position in this embodiment helps prevent inadvertent contact between knife 440 and a user of circular stapler 10, and between knife 440 and a patient.

[0092] In addition to the embodiment disclosed herein where a proximal portion 422 of knife carrier 420 is configured to engage snap ring 180, another embodiment is disclosed where proximal portion 422 of knife carrier 420 is configured to mechanically engage a drive member or sleeve 450 when knife carrier 420 mechanically engages pusher adapter 532. More particularly, in this embodiment, annular groove 463 of proximal portion 422 of knife carrier 420 is included on plurality of legs 460 (FIG. 13), with each leg 460 including a portion of annular groove 463 which is configured to engage a lip 452 of drive sleeve 450 (FIGS. 16, 18, 19 and 21). Further, legs 460 are configured to deflect radially inwardly, which allows proximal portion 422 of knife carrier 420 to be longitudinally translated proximally beyond lip 452 of drive sleeve 450, thus effectively coupling knife carrier 420 with drive sleeve 450 (see FIGS. 16, 18, 19 and 21, for example). As can be appreciated, in this embodiment, longitudinal translation of drive sleeve 450 (e.g., via a second actuation stroke of handle 24) causes a corresponding longitudinal translation of knife carrier 420.

[0093] With reference to FIGS. 22-27, further details of anvil assembly 105 are illustrated in accordance with embodiments of the present disclosure. Anvil assembly 105 is longitudinally movable with respect to cartridge assembly 110, and includes a retention rod 108, which selectively connects anvil assembly 105 with the remainder of surgical stapler 10. Anvil assembly 105 includes an anvil head 600 and a cutting ring 620. Anvil head 600 includes a plurality of staple-deforming pockets 602 formed directly therein (i.e., without the inclusion of a traditional anvil plate). Pockets 602 are configured to receive legs of the staples ejected from staple cartridge 110 and to deform the legs into an appropriate shape. In the illustrated embodiment, pockets 602 are disposed in three rows and annularly extend along a tissue-contacting surface 604 of anvil head 600. Anvil assembly 105 also includes an attachment member 606 extending proximally from anvil head 600. Attachment member 606 is configured to pivotably engage retention rod 108. An annular cavity 608 is defined by anvil head 606 and is disposed around (e.g., surrounding) attachment member 606 (FIGS. 24 and 25). It is envisioned that the entirety of anvil head 606 is monolithically formed and/or is made of the same material.

[0094] Cutting ring 620 is configured for positioning within annular cavity 608 of anvil head 600. More particularly, cutting ring 620 includes an outer ring 622, an inner ring 624, an annular knife channel 626 disposed between outer ring 622 and inner ring 624, and a severable portion 628 disposed proximally-adjacent knife channel 626. Severable portion 628 is configured to be cut by knife 440 (see FIGS. 26 and 27) during the cutting stroke of circular instrument 10.

[0095] Cutting ring 620 also includes a plurality of tabs 630 disposed around its outer annular edge 622. Tabs 630 are configured to mechanically engage a groove 610 disposed around an inner annular surface 612 of anvil head 600. Any number of tabs 630 (including a single tab 630 that extends along the entire surface 612) may be included on cutting ring 620. More particularly, each tab 630 includes a proximal surface 632 that is substantially perpendicular to annular edge 629, and a distal surface 634 that is angled with respect to annular edge 629 and with respect to proximal surface 632.

[0096] Distal surface 634 of tab 630 is configured to facilitate assembly between cutting ring 620 and anvil head 600. That is, during assembly, cutting ring 620 is inserted into annular cavity 608 in a proximal-to-distal direction such that distal surface 634 contacts a portion of anvil head 600 and causes cutting ring 620 to deflect radially inwardly to allow tabs 630 to extend distally beyond a lip 611 formed by a proximal surface of groove 610. It is further envisioned that cutting ring 620 is made of a flexible material (e.g., polyethylene) to further facilitate assembly.

[0097] With reference to FIGS. 26 and 27, proximal surface 632 of tabs 630 is configured to engage lip 611 of groove 610 to help ensure engagement therebetween. More particularly, in use, when knife 440 is advanced to cut tissue, knife 440 also penetrates severable portion 628, which separates outer ring 622 and inner ring 624 (see FIG. 27). As shown in FIG. 27 when compared to FIG. 26, distal advancement of knife 440 also pushes cutting ring 620 distally within cavity 608. The engagement between outer ring 622 of cutting ring 620 and anvil head 600 helps ensure outer ring 622 is removed from the surgical site when anvil head 600 is removed.

[0098] With reference to FIGS. 28-30, further details of anvil assembly 105 and its retention rod 108 are illustrated in accordance with embodiments of the present disclosure. As discussed above, anvil head 600 is pivotably engaged with retention rod 108, e.g., to facilitate removal of anvil assembly 105 from within tissue. In use, tissue “T” is tied or purse-string sutured to a distal portion 108a of retention rod 108. Distal portion 108a is defined as being disposed distally of a lip 109, which is configured to limit proximal travel of tissue “T,” and as being the portion of retention rod 108 that is configured to contact tissue “T.”

[0099] In the illustrated embodiment, distal portion 108a of retention rod 108 is tapered along its entire length. Further, distal portion 108a includes a continuous taper, which includes a concave portion 108b and a convex portion 108c. As shown, distal portion 108a lacks a stepped configuration and lacks abrupt angle changes. It is envisioned that this tapered configuration of distal portion 108a of retention rod 108 helps purse-string sutured tissue “T” easily slide proximally when anvil head 600 tilts and thus urges tissue “T” proximally (see FIG. 30).

[0100] With reference to FIGS. 31-34, retention rod 108 of anvil assembly 105 is configured to selectively engage a trocar 700 extending distally beyond cartridge assembly 110. More particularly, this embodiment illustrates a first retention rod 108′ that is configured to engage a first trocar 700′ (FIG. 32), and a second retention rod 108″ that is configured to engage a second trocar 700″ (FIG. 32A). Here, however, first retention rod 108′ cannot properly engage second trocar 700″ (FIG. 33), and second retention rod 108″ cannot properly engage first trocar 700′ (FIG. 34). That is, engagement between first retention rod 108′ and first trocar 700′, and between second retention rod 108″ and second trocar 700″ would result in the two components securely engaging each other such that longitudinal translation of the first component (e.g., first retention rod 108′) in the opposite direction of the second component (e.g., first trocar 700′) would result in a corresponding amount of longitudinal translation of the second component. Conversely, an attempted engagement between first retention rod 108′ and second trocar 700″, or between second retention rod 108″ and first trocar 700′ would result in the two components being free from secure engagement with each other such that longitudinal translation of the first component (e.g., first retention rod 108′) in the opposite direction of the second component (e.g., second trocar 700″) would cause the first component to move away from the second component.

[0101] It is envisioned that each of first retention rod 108′ and first trocar 700′ are configured for use with a particular configuration of staples. For instance, it is envisioned that first retention rod 108′ is part of an anvil assembly 105 that includes two rows of staple-deforming pockets 602, and that first trocar 700′ is part of/usable with a shell assembly 100 including two rows of pusher elements 546 and a staple cartridge 150 having two rows of staples “S.” Likewise, it is envisioned that second retention rod 108″ is part of an anvil assembly 105 that includes three rows of staple-deforming pockets 602, and that second trocar 700″ is part of/usable with a shell assembly 100 including three rows of pusher elements 546 and a staple cartridge 150 having three rows of staples “S.”

[0102] More particularly, first retention rod 108′ includes a recess 108′R that is configured to engage a lip 700′L extending from first trocar 700′ (FIG. 32). Similarly, second retention rod 108″ includes a recess 108″R that is configured to engage a lip 700″L extending from second trocar 700″ (FIG. 32A). The geometry of retention rods 108′, 108″ and trocars 700′, 700″ enable this mistake-proof engagement therebetween. More particularly, and with reference to FIGS. 32 and 32A, it is envisioned and illustrated that first retention rod 108′ includes a larger diameter dr′ than a corresponding diameter dr″ of second retention rod 108″. Here, first trocar 700′ includes a larger diameter dt′ than a corresponding diameter dt″ of second trocar 700″. Additionally, it is envisioned and illustrated that the distance between recess 108′R and a proximal lip 108′P of first retention rod 108′ is shorter than the distance between recess 108″R and a proximal lip 108″P of second retention rod 108″. Likewise, the illustrated embodiments show that the distance between lip 700′L and a tip 700′T of first trocar 700′ is shorter than a corresponding distance between lip 700″L and a tip 700″T of second trocar 700″.

[0103] With reference to FIGS. 33 and 34, recess 108′R of first retention rod 108′ is not able to properly engage lip 700″L of second trocar 700″ (FIG. 33), and recess 108″R of second retention rod 108″ is not able to properly engage lip 700′L of first trocar 700′ (FIG. 34), e.g., due to the various geometries discussed above. As discussed above, proper engagement between a retention rod 108 and a trocar 700 is the secure engagement therebetween.

[0104] Additionally, it is envisioned that each of first trocar 700′ and second trocar 700″ includes an indicator 702 that is perceptible to a user if there is not proper engagement between a retention rod 108 and a trocar 700 (e.g., if a user attempts to engage first retention rod 108′ with second trocar 700″, or vice versa). The present disclosure includes indicators 702 that provide visual (e.g., a colored band, letters, symbols, etc.), audio (e.g., beeps, clicks, etc.) and/or tactile (e.g., vibration, etc.) information As illustrated, indicator 702 is not perceptible (e.g., visible) when there is proper engagement between a retention rod 108 and a trocar 700. Alternatively, it is envisioned that indicator 702 is perceptible to a user if there is proper engagement between a retention rod 108 and a trocar 700, and indicator 702 is non perceptible to a user if there is not proper engagement between a retention rod 108 and a trocar 700.

[0105] Referring now to FIGS. 35-39, details regarding the engagement between drive member 800 and pusher adapter 532 are shown in accordance with an embodiment of the present disclosure. During use of this embodiment of circular stapler 10, an initial actuation stroke is performed to fire staples “S” into tissue. Here, drive member 800 (or a portion thereof) is distally advanced into engagement with pusher adapter 532, and continued advancement of drive member 800 causes pusher adapter 532 to urge pusher member 540 distally to eject the staples “S” (as discussed above). Next, drive member 800 and pusher adapter 532 are retracted proximally (while pusher member 540 remains in its advanced position). Then, in response to a second actuation stroke, for example, drive member 800 and pusher adapter 532 are again advanced distally so that pusher adapter 532 urges and/or engages knife carrier 420 distally to sever tissue. As can be appreciated, this embodiment differs from embodiments described above, as here, independent actuation strokes are completed by the same drive member 800 completing two strokes (as opposed to the use of two separate drive members being used).

[0106] FIGS. 35-39 illustrate various features of the engagement between drive member 800 and pusher adapter 532, which are configured to help facilitate engagement therebetween, and to help ensure engagement therebetween during advancement and retraction of drive member 800. More particularly, drive member 800 (e.g., an adapter nut) includes a recess 802 (e.g., an annular recess) configured to engage tabs 810 on fingers 820 on proximal portion 533 of pusher adapter 532. As drive member 800 is distally translated and contacts pusher adapter 532, a distal surface 804 of drive member 800 contacts tabs 810 and forces tabs 810 and fingers 820 radially inward (FIG. 37). Continued advancement of drive member 800 with respect to pusher adapter 532 causes tabs 810 and fingers 820 to move radially outward, such that tabs 810 are within recess 802 (FIGS. 38 and 39).

[0107] In disclosed embodiments and with particular reference to FIGS. 36 and 37, a distal wall 803 of recess 802 forms an angle α1 of between about 70° and about 90° with respect to the longitudinal axis A-A. In embodiments, angle α1 is between about 70° and about 80°, or between about 75° and about 78°. Similarly, a distal wall 812 of tabs 810 forms an angle α2 of between about 70° and about 90° with respect to the longitudinal axis A-A. In embodiments, angle α2 is between about 70° and about 80°, or between about 75° and about 78°. It is envisioned that the angles formed by distal wall 803 of recess 802 and by distal wall 812 of tables 810 are equal, substantially equal, or differently from each other.

[0108] Additionally, in disclosed embodiments, the height “h” of tabs 810 (and the corresponding depth of the corresponding portion of recess 802) is between about 0.010 inches and about 0.020 inches (see FIG. 36). In embodiments, height “h” is approximately equal to 0.015 inches.

[0109] It is further disclosed that pusher adapter 532 (or at least fingers 820 thereof) is made from glass-filled polycarbonate. Here, it is envisioned that the percentage of glass is between about 20% and about 40% (e.g., about equal to 30%).

[0110] It is envisioned that the combination of the angles of distal walls 803 and 812, the height “h” of tabs 810, and the material that pusher adapter 532 is made from all contribute to a secure engagement between pusher adapter 532 and drive member 800, and result in an optimum amount of force necessary to disengage pusher adapter 532 from drive member 800.

[0111] With reference to FIGS. 40 and 41, the present disclosure also includes a communication chip assembly 900, which is configured to communicate various information to and from other portions of circular stapler 10. With particular reference to FIG. 40, communication chip assembly 900 includes a case 910 housing a communication chip 902. Case 910 includes a tube portion 912 and a ring portion 914. With reference to FIG. 41, tube portion 912 of case 910 is configured to be press-fit into housing 120 of shell assembly 100. Ring portion 914 is configured for surrounding (or at least partially surrounding) inner cylindrical body 124 of housing 120 (e.g., via a compression-fit arrangement). Additionally, case 910 includes a plurality of tabs 916 that are configured to engage respective slots/detents (not explicitly shown) in housing 120 to help prevent rotation of communication chip assembly 900 with respect to housing 120.

[0112] A proximal portion of communication chip 902 includes a plurality of contacts 904 for engaging contact pins of a portion (e.g., adaptor—not shown) of circular stapler 10. As can be appreciated, this engagement between contacts 904 and contact pins allows information to be communicated from one portion of circular stapler 10 (e.g. handle assembly 20) to shell assembly 100. Further, communication chip 902 is spring-loaded via a biasing member 918 in a proximal direction (e.g., to allow for positional length tolerance of the contact pins in the adapter).

[0113] It is envisioned that communication chip 902 includes both read and write capability, and is particularly useful with a powered surgical stapler. The read capability of communication chip 902 enables communication of various features of shell assembly 100 to handle assembly 20. For example, communication chip 902 can store and relay information relating to cartridge size, staple length, and clamp-up distance. Once this information is received by handle assembly 20, for example, firing forces and firing stroke can be adjusted accordingly. The write capability of communication chip 902 enables handle assembly 20, for example, to encode a used (i.e., fired) cartridge assembly 110 to prevent reuse or attempted firing of a staple-less cartridge assembly 110. Further details of communication components (e.g., chips, transmitters, control modules, etc.) are disclosed in U.S. patent application Ser. No. 13/545,362, which was filed on Jul. 10, 2012, the entire contents of which being incorporated by reference herein.

[0114] The use of circular stapler 10 will now be described as it pertains to various embodiments of the present disclosure. In use, circular stapler 10 is operated in a manner substantially similar to a traditional circular stapler. Once oriented such that the tissue to be stapled is received between cartridge assembly 110 and anvil assembly 105, and anvil assembly 105 is approximated towards cartridge assembly 110 via rotation of approximation knob 26, trigger 24 may be squeezed to cause the actuation of handle assembly 20. Actuation of handle assembly 20 causes a first advancement of a drive assembly (e.g., 800) which engages and causes the advancement of pusher assembly 530. During the first or staple forming stroke, pusher assembly 530 is moved relative to housing 120 and knife assembly 400, while knife assembly 400 remains stationary relative to housing 120. In this manner, during the first or staple forming stroke of circular stapler 10 only the staple forming function is performed. Accordingly, the force required for completion of the first stroke of circular stapler 10 does not include the force necessary to also cut the tissue simultaneously therewith.

[0115] Upon completion of the first or staple forming stroke, trigger 24 is released to permit the retraction of the drive member and pusher adapter 532 of pusher assembly 530. In various embodiments, pusher adapter 532 is retracted to a position proximal of its initial position. For example, it is envisioned that pusher adapter 532 is retracted about 0.25 inches farther proximally from its initial starting position. In this retracted position, notch 535 formed in the distal end of pusher adapter 532 is aligned with snap ring 180 thereby allowing snap ring 180 to expand from the first or compressed condition to the second or uncompressed condition.

[0116] A subsequent squeezing or actuation of trigger 24 causes a second advancement of the drive member and pusher adapter 532. Advancement of pusher adapter 532 causes engagement of ledge 536 of pusher adapter 532 with snap ring 180. Since snap ring 180 remains engaged with knife carrier 420 in this position, advancement of pusher adapter 532 also causes the advancement of knife assembly 420. Advancement of circular knife 440 of knife assembly 400 causes the cutting of tissue positioned between cartridge assembly 110 and anvil assembly 105. Because staples “S” were ejected and formed during the first stroke of circular stapler 10, and pusher member 540 remained in the advanced position upon retraction of pusher adapter 532 following the first or staple forming stroke, the force required to complete the second or cutting stroke of circular stapler 10 is less then the force that would be necessary to complete both the staple ejecting/forming and tissue cutting procedure. It is envisioned that the force provided by the drive member during the second stroke would be sufficient to disengage any securing mechanism maintaining knife assembly 400 relative to inner cylindrical housing 124 of housing 120. Such securing mechanism may include protrusions (not shown) formed on the inner surface of knife carrier 420 and/or on the outer surface of inner cylindrical portion 124 of housing 120 configured to be received within detents (not shown) formed on the other of the outer surface of inner cylindrical portion 124 and/or on the inner surface of knife carrier 420 such that knife assembly 400 is permitted to advance distally relative to housing 120.

[0117] Upon completion of the tissue cutting stroke, pusher adapter 532 is retracted proximally to one of the initial position or the retracted position. As discussed above, pusher assembly 530 and knife assembly 400 may be configured such that either or both of pusher assembly 530 and knife assembly 400 are retracted following the second or cutting stroke of circular stapler 10. Retraction of pusher adapter 532 to one of the initial or retracted positions causes disengagement of pusher member 540 from pusher adapter 532. In this manner, pusher member 540 and empty staple cartridge 150 may be separated or unloaded from housing 120 and replaced with a new pusher member 540 and/or staple cartridge 150.

[0118] Further details regarding the operation of circular stapler 10, including the operation of cartridge assembly 110, will now be described as it pertains to various embodiments of the present disclosure. In the initial condition, pusher assembly 530 is received between outer and inner cylindrical portions 122, 124 of housing 120. Knife assembly 400 is received within longitudinal passage 531 of pusher adapter 532 and about inner cylindrical portion 124 of housing 120. Staple cartridge 150 is in operative engagement with a distal portion of housing 120 to operably retain pusher assembly 530 and knife assembly 400 within housing 120. Snap ring 180 is in the first or radially compressed condition and received within annular groove 463 formed on knife carrier 420. Snap ring 180 is maintained in the radially compressed condition by an inner wall of pusher adapter 532. Notch 535 formed in the distal end of pusher adapter 532 is disposed distal of annular groove 463 and snap ring 180. In this manner, pusher assembly 530 may be advanced distally without causing the advancement of knife assembly 400.

[0119] In the initial position, pusher assembly 530 is prevented from inadvertent distal advancement relative to housing 120 through engagement of the plurality of paired detents 538a, 538b (FIG. 3) formed on distal portion 534 of pusher adapter 532 with openings 129 formed in outer cylindrical portion 122 of housing 120.

[0120] During a first or staple forming stroke of circular stapler 10, following approximation of anvil assembly 105 with respect to cartridge assembly 110 (e.g., via rotation of approximation knob 26), actuation of trigger 24 relative to handle 22 causes advancement of a drive assembly (e.g., 800) which operably engages pusher adapter 532 to cause the distal translation of pusher assembly 530. Distal translation of pusher adapter 532 advances pusher member 540 thereby causing pusher elements 546 to be advanced into and/or through staple receiving pockets 152 of staple cartridge 150 and to eject staples “S” from staple cartridge 150. Although not explicitly shown, the ejection of staples “S” from staple cartridge 150 causes advancement of staples “S” into staple-deforming pockets 602 of anvil head 600. Forming of staples “S” secures the tissue retained between staple cartridge 150 and anvil assembly 105.

[0121] Upon completion of the stapling stroke, pusher adapter 532 is retracted proximally relative to housing 120. Pusher adapter 532 is sufficiently retracted relative to knife carrier 420 and snap ring 180 such that snap ring 180 is aligned with notch 535 formed in the distal end of pusher adapter 532. Alignment of notch 535 with snap ring 180 allows snap ring 180 to move from the first or compressed condition to the uncompressed condition, i.e., snap ring 180 is able to decompress or radially expand.

[0122] During the second or cutting stroke of circular stapler 10, a second actuation of trigger 24 relative to handle 26 causes advancement of the drive member (e.g., 800) which operably engages pusher adapter 532 to cause the distal translation of pusher adapter 532. Distal translation of pusher adapter 532 causes ledge 536, defined by notch 535 formed in the distal end of pusher adapter 532, to engage an outer portion of snap ring 180 while an inner portion of snap ring 180 remains engaged with knife carrier 420. In particular, step 142a, formed within/adjacent groove 463 of knife carrier 420, engages snap ring 180 and prevents snap ring 180 from being radially compressed back into annular groove 463 during the second advancement of pusher adapter 532 during the second or tissue cutting stroke of circular stapler 10. Accordingly, step 462a of knife carrier 420 maintains snap ring 180 in the second or expanded condition such that snap ring 180 remains in contact with both pusher adapter 532 and knife carrier 420 to assure the simultaneous advancement of knife assembly 400 with the advancement of pusher adapter 532.

[0123] Continued advancement of pusher adapter 532 causes knife 440 to be received through longitudinal opening 151 of staple cartridge 150, thereby severing the tissue retained between staple cartridge 150 and anvil assembly 105, and thereby penetrating severable portion 628 of cutting ring 620. It is envisioned that pusher assembly 530 and knife assembly 400 may be configured such that retraction of the drive assembly causes the retraction of pusher adapter 532 and knife carrier 420 (see FIGS. 11-21, for example).

[0124] In addition to the reduced force requirements provided by the two stroke operation of circular stapler 10, the independent or decoupled staple forming and tissue cutting function of circular stapler 10 also permits the varying of the staple crimp height relative to the knife travel distance, the varying of the staple travel speed relative to the knife travel speed, and/or the addition of a dwell time between staple formation and tissue cutting. This configuration allows a clinician to optimize staple crimp heights to given conditions, such as, tissue thickness, tissue compliance and clamping force. This configuration may also allow for the monitoring of staple forming and knife cutting forces, to alert the clinician in case an abnormal force is detected. This configuration further allows force and other data to be monitored and used for data collection and research, which when analyzed, may lead to further optimization of operational parameters, such as staple crimp height, and dwell and travel speed. By independently controlling and optimizing these various parameters, improved hemostasis and anastomonic joint strength may result across a much broader range of tissue thicknesses, thereby allowing a clinician to have improved and customized control over the results. Further still, when the stapling and cutting functions are performed at the same time, the tissue being stapled may be displaced by the knife, thereby causing the staple legs to deflect and misalign with their intended anvil pockets, resulting in poor staple formation and possible leakage.

[0125] It will be understood that various modifications may be made to the embodiments disclosed herein. For example, circular stapler 10 may include a mechanism for changing cartridge assembly 110 from two stroke operation to a single stroke operation. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.