Surgical stapling device with tissue gap control

Abstract

A surgical stapling device includes an anvil assembly having an anvil head, an anvil plate, and a biasing member. The anvil plate is supported on the anvil head and is movable between a distal-most position and a proximal-most position to vary the size of a tissue gap between the anvil assembly and a reloading assembly to accommodate tissue of different thicknesses.

Description

[0001] This application claims priority to U.S. Provisional Patent Application 63 / 433,814, filed on December 20, 2022, the entire content of which is incorporated herein by reference. TECHNICAL FIELD

[0002] The present disclosure relates to surgical stapling devices, and more particularly to surgical stapling devices having a tool assembly for accommodating an extended range of tissue thicknesses. BACKGROUND OF THE DISCLOSURE

[0003] Surgical stapling devices for ejecting staples in a quick and efficient manner to join tissues or tissue segments in a variety of surgical procedures, such as anastomosis procedures, are well known. Generally, a surgical stapling device includes a tool assembly having a cartridge assembly and an anvil. The cartridge assembly includes a staple cartridge that supports a plurality of staples. The anvil and the staple cartridge are supported on the stapling device to allow the tool assembly to move between an open position and a clamping position. In the clamping position, the anvil and the staple cartridge of the cartridge assembly are supported in side-by-side alignment and include tissue contact surfaces that define a predetermined tissue gap. The size of the tissue gap and the size of the staples within the staple cartridge are sized for tissue having a thickness within a pre-determined thickness range to appropriately effect hemostasis. If the tissue positioned between the jaws is outside the pre-determined range, i.e., too thick or too thin, the staples ejected from the staple cartridge of the cartridge assembly may be deformed and not provide effective hemostasis. Additionally, if the clinician misidentifies the tissue thickness, or if the tissue thickness approaches the outer edge of the range for a given staple size, the effectiveness of hemostasis may be affected.

[0004] There is a continuing need in the art of suturing for a surgical stapling device that can provide effective hemostasis for a greater range of tissue thicknesses. SUMMARY OF THE DISCLOSURE

[0005] The present disclosure relates to a surgical stapling device that includes a handle assembly, an adapter assembly, a reload assembly, and an anvil assembly, the anvil assembly being supported on a distal portion of the adapter assembly and being movable relative to the reload assembly between an unclamped position and a clamped position. In the clamped position, the anvil assembly and the reload assembly define a tissue gap that is sized to receive tissue. The anvil assembly includes an anvil head, an anvil plate, and a biasing member. The anvil plate is supported on the anvil head and is movable between a most distal position and a most proximal position to vary the size of the tissue gap between the anvil assembly and the reload assembly to accommodate tissue of different thicknesses.

[0006] Aspects of the present disclosure relate to an anvil assembly that includes an anvil shaft, an anvil head, an anvil plate, and a biasing member. The anvil shaft has a proximal portion and a distal portion. The anvil head includes a body portion and an anvil post fixed to the body portion. The anvil post is fixed to the distal portion of the anvil shaft. The anvil head has a stepped inner surface that includes an outer annular support surface and an inner recessed surface located distally of the outer annular support surface. The inner recessed surface defines a cavity. The anvil plate has a stepped circular configuration and includes a proximal nail forming portion and an inner body portion. The inner body portion is received within the cavity defined by the inner recessed surface of the anvil head. The proximal nail forming portion of the anvil plate has a distal surface and an annular proximal surface that defines a nail forming pit. The anvil plate is movable relative to the anvil head between a most proximal position and a most distal position. The biasing member is supported on the outer annular support surface of the anvil head and engages the distal surface of the proximal nail forming portion of the anvil plate to urge the anvil plate toward the most proximal position.

[0007] In aspects of the present disclosure, the anvil assembly includes a retaining ring that is fixed to the anvil post and is positioned to engage the anvil plate to prevent the anvil plate from moving distally beyond the most distal position.

[0008] In some aspects of the present disclosure, the biasing member includes a wave spring.

[0009] In certain aspects of the present disclosure, the biasing member includes a compressible washer.

[0010] In aspects of the present disclosure, the biasing member includes a helical spring.

[0011] In some aspects of the present disclosure, the body of the anvil head includes an annular edge positioned around the outer annular support surface of the anvil head.

[0012] In certain aspects of the present disclosure, the annular edge of the body of the anvil head is positioned to engage the distal surface of the anvil plate to prevent the anvil plate from moving proximally beyond the most proximal position.

[0013] In aspects of the present disclosure, the anvil shaft is pivotally coupled to the anvil post by a pivot pin.

[0014] In some aspects of the present disclosure, the anvil post defines an annular slot that receives the retaining ring.

[0015] In certain aspects of the present disclosure, the retaining ring defines a slit to facilitate placement of the retaining ring around the anvil shaft.

[0016] Other aspects of the present disclosure relate to an anvil assembly that includes an anvil shaft, an anvil head, an anvil plate, a biasing member, and a retaining ring. The anvil head includes a body portion and an anvil post that is fixed to the anvil shaft. The anvil head has a stepped inner surface that includes an outer annular support surface and an inner recessed surface that is positioned distal to the outer annular support surface. The inner recessed surface defines a cavity. The anvil plate includes a proximal staple forming portion and an inner body portion. The inner body portion is received within the cavity defined by the inner recessed surface of the anvil head. The proximal staple forming portion of the anvil plate has a distal surface. The anvil plate is movable relative to the anvil head between a most proximal position and a most distal position. The biasing member is supported on the outer annular support surface of the anvil head and engages the distal surface of the proximal staple forming portion of the anvil plate to bias the anvil plate toward the proximal position. The retaining ring is fixed to the anvil post and is positioned to engage the anvil plate to prevent the anvil plate from moving distally beyond the most distal position.

[0017] Other aspects of the present disclosure relate to a suturing device that includes an adapter assembly, a reload assembly, and an anvil assembly. The adapter assembly has a proximal portion and a distal portion and includes an anvil retainer. The reload assembly is supported on the distal portion of the adapter assembly and includes a housing and a staple cartridge. The staple cartridge supports staples. The anvil assembly includes an anvil shaft, an anvil head, an anvil plate, and a biasing member. The anvil shaft has a proximal portion and a distal portion. The proximal portion of the anvil shaft is coupled to the anvil retainer. The anvil head includes a body portion and an anvil post. The anvil post is fixed to the distal portion of the anvil shaft. The anvil head has a stepped inner surface that includes an outer annular support surface and an inner recessed surface that is positioned distal to the outer annular support surface. The inner recessed surface defines a cavity. The anvil plate has a stepped circular configuration and includes a proximal staple forming portion and an inner body portion. The inner body portion is received within the cavity defined by the inner recessed surface of the anvil head. The proximal staple forming portion of the anvil plate has a distal surface and an annular proximal surface that defines a staple forming pit. The anvil plate is movable relative to the anvil head between a most proximal position and a most distal position. The biasing member is supported on the outer annular support surface of the anvil head and engages the distal surface of the proximal staple forming portion of the anvil plate to bias the anvil plate toward the proximal position.

[0018] Other aspects of the present disclosure will be understood from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Aspects of the disclosed surgical suturing device are described hereinbelow with reference to the accompanying drawings, in which:

[0020] Figure 1Is a side perspective view of a surgical stapling device incorporating aspects of the present disclosure, wherein the stapling device is in an open position;

[0021] Figure 2 Is Figure 1 A side perspective view of the anvil assembly of the surgical stapling device shown;

[0022] Figure 3 Is Figure 2 An exploded side perspective view of the anvil assembly shown;

[0023] Figure 3A Is Figure 3 A side perspective view of the biasing member of the anvil assembly shown;

[0024] Figure 4 Is a cross-sectional view taken along Figure 2 Section line 4-4;

[0025] Figure 5 Is Figure 1 A side perspective view of the distal portion of the surgical stapling device shown, wherein the distal portion of the surgical stapling device is shown in dashed lines and is positioned within a body cavity in a clamped position around thin tissue;

[0026] Figure 6 Is a cross-sectional view taken along Figure 5 Section line 6-6;

[0027] Figure 7 Is Figure 1 A side perspective view of the distal portion of the surgical stapling device shown, wherein the distal portion of the surgical stapling device is shown in dashed lines and is positioned within a body cavity in a clamped position around thick tissue;

[0028] Figure 8 Is Figure 1 A side perspective view of the distal portion of the surgical stapling device shown, wherein the distal portion of the surgical stapling device is shown in dashed lines and is positioned within a body cavity in a clamped position around uneven tissue;

[0029] Figure 9 Is Figure 3 A side perspective view of an alternative version of the biasing member of the anvil assembly shown;

[0030] Figure 10 Is Figure 1 A side cross-sectional view of the anvil assembly of the surgical stapling device shown, the anvil assembly including Figure 9 An alternative version of the biasing member shown;

[0031] Figure 11 Is Figure 3A side perspective view of another alternative version of the biasing member of the anvil assembly shown; and

[0032] Figure 12 is Figure 1 A side cross-sectional view of the anvil assembly of the surgical stapling device shown, the anvil assembly including Figure 11 An alternative version of the biasing member shown. DETAILED DESCRIPTION

[0033] The disclosed surgical stapling device will now be described in detail with reference to the accompanying drawings, where like reference numerals in each of several views represent the same or corresponding elements. However, it should be understood that the disclosed aspects of the surgical stapling device are merely examples of the present disclosure and may be embodied in various forms. Well-known functions or constructions of the surgical stapling device are not described in detail so as not to obscure the present disclosure with unnecessary details. Accordingly, the specific structural and functional details disclosed herein should not be construed as limiting, but merely as a basis for the claims and as a representative basis for teaching one of ordinary skill in the art to employ the present disclosure differently in virtually any suitable specific structure.

[0034] In this specification, the term "proximal" is generally used to refer to the part of the device that is closer to the clinician during use of the device in its conventional manner, while the term "distal" is generally used to refer to the part of the device that is farther from the clinician during use of the device in its conventional manner. Additionally, the term "clinician" is generally used to refer to medical personnel including doctors, nurses, and support staff. Further, directional terms such as front, back, up, down, top, bottom and similar terms are used to assist in understanding this specification and are not used to limit the present disclosure.

[0035] The disclosed surgical stapling device includes a handle assembly, an adapter assembly, a reload assembly, and an anvil assembly, the anvil assembly being supported on a distal portion of the adapter assembly and being movable relative to the reload assembly between an unclamped position and a clamped position. In the clamped position, the anvil assembly and the reload assembly define a tissue gap sized to accommodate tissue. The anvil assembly includes an anvil head, an anvil plate, and a biasing member. The anvil plate is supported on the anvil head and is movable between a most distal position and a most proximal position to vary the size of the tissue gap between the anvil assembly and the reload assembly to accommodate different thicknesses of tissue. In aspects of the present disclosure, the cartridge assembly and the anvil assembly have an annular configuration.

[0036] Figure 1Illustrated is a circular stapling device generally designated as stapling device 10 in accordance with aspects of the present disclosure. The stapling device 10 includes a handle assembly 12, an elongate body or adapter assembly 14, a reload assembly 16, and an anvil assembly 18. The anvil assembly 18 is supported in a releasable manner on the distal end of the adapter assembly 14 and is movable relative to the reload assembly 16 between a spaced-apart position and a clamping position, as is known in the art. More specifically, the anvil assembly 18 is releasably coupled to an anvil holder 19 ( Figure 6 ) of the adapter assembly 14 and is movable with the anvil holder 19 relative to the reload assembly 16 between an unclamped position and a clamped position.

[0037] The reload assembly 16 includes a proximal portion 16a releasably coupled to a distal portion 14a of the adapter assembly 14. Alternatively, the reload assembly 16 can be fixedly secured to the distal portion 14a of the adapter assembly 14. In certain aspects of the present disclosure, the handle assembly 12 includes a fixed grip 22 that supports actuation buttons 24 for controlling the operation of various functions of the stapling device 10, the operation including bringing the reload assembly 16 into proximity with the anvil assembly 18, firing staples from the reload assembly 16, and performing tissue cutting or circumcision.

[0038] The reload assembly 16 includes a housing 26 that supports an annular staple cartridge 27 that includes staples 28 ( Figure 6 ). The reload assembly 16 further includes an annular knife 29 ( Figure 6 ) that is movable through the annular staple cartridge 27 to engage a cutting ring 38 of the anvil assembly 18.

[0039] The stapling device 10 is illustrated as an electric stapling device and includes a handle assembly 12 that can support one or more batteries (not shown). The adapter assembly 14 transfers electrical power from the handle assembly 12 to the reload assembly 16 and the anvil assembly 18. Examples of electric stapling devices can be found in U.S. Patent Nos. 9,055,943, 9,023,014, and U.S. Application Publication Nos. 2018 / 0125495 and 2017 / 0340351. Alternatively, it is contemplated that the stapling device 10 can also be a manual stapling device such as that disclosed in U.S. Patent No. 7,303,106 ('106 patent), or a stapling device that is configured for use with a robotic system and does not include a handle assembly such as that disclosed in U.S. Patent No. 9,962,159.

[0040] Figures 2 to 4An anvil assembly 18 is illustrated, which includes an anvil shaft 30, an anvil head 32, an anvil plate 34, a biasing member 36, a cutting ring 38, and a retaining ring 40. The anvil head 32 includes a body portion 42 and a post 44 located at the center and extending proximally from the body portion 42. In aspects of the present disclosure, the post 44 defines a transverse through-hole 46. The anvil head 32 is coupled to the anvil head 30 by a pivot pin 48 that extends through an opening 50 in the distal portion of the anvil shaft 30 and through the through-hole 46 in the post 44 to secure the anvil head 32 to the anvil shaft 30 for pivotable movement from an operating position to a reduced profile position. For a detailed description of an exemplary anvil assembly having a pivotable anvil head, see the '106 patent. It is also contemplated that the anvil head 32 can be securely fixed to the anvil shaft 30.

[0041] The anvil head 32 has a circular configuration and includes a stepped inner surface 52 and a curved outer surface 54. The stepped inner surface 52 includes an outer annular support surface 56 and an inner recessed surface 58 located distally of the annular support surface 56. The anvil head 32 defines a cavity 59 that is aligned with the inner recessed surface of the anvil head 32 and is located medial to the support surface 56. In aspects of the present disclosure, the anvil head 32 defines one or more openings 60 that extend between the inner recessed surface 58 and the outer surface 54 of the anvil head 32 to connect the cavity 59 and the atmosphere. The anvil head 32 includes an annular edge 62 that extends proximally from and around the support surface 56.

[0042] The anvil plate 34 includes a body 64 having a stepped circular configuration and includes a staple forming portion 66 and an inner body portion 68 located distally of the staple forming portion 66. The inner body portion 68 of the anvil plate 34 defines a central opening 70 that receives the post 44 of the anvil head 32 such that the inner body portion 68 is slidably received within the cavity 59 of the anvil head 32. The staple forming portion 66 of the anvil plate 34 is annular and is located proximal to the support surface 56 of the anvil head 32. The staple forming portion 66 has a diameter corresponding to the diameter of the anvil head 32 and includes a distal surface 66a ( Figure 4 ), which is positioned to engage the annular edge 62 of the anvil head 32 when the inner body portion 68 is moved distally into the cavity 59 of the anvil head 32, as described in further detail below.

[0043] The biasing member 36 is received on the support surface 56 of the anvil head 32 between the support surface 56 of the anvil head 32 and the distal surface 66a of the anvil plate 34. The biasing member 36 is positioned to urge the anvil plate 34 proximally away from the anvil head 32 to a position where the distal surface 66a of the nail forming portion 66 of the anvil plate 34 is spaced from the annular edge 62 of the anvil head 32. In aspects of the present disclosure, the biasing member 36 is in the form of a wave spring 36a having a sinusoidal or wavy configuration. In some aspects of the present disclosure, the wave spring 36a is formed of spring steel, although other construction materials are also contemplated. In some aspects of the present disclosure, the wave spring 36a is fixed to the support surface 56 by spot welding. It is contemplated that the wave spring 36a can be fixed to the support surface 56 using other fastening techniques or devices, or not fixed to the support surface of the anvil head at all. It is also contemplated that different types of one or more springs can be used to form the biasing member 36. For example, as Figure 9 and Figure 10 shown, the biasing member can be in the form of a compressible washer 136 that is positioned between the distal surface 66a of the anvil plate 34 and the annular support surface 56 of the anvil head 32, or as Figure 11 and Figure 12 shown, the biasing member can be in the form of a helical spring 236 that is positioned between the distal surface 66a of the anvil plate 34 and the annular support surface 56 of the anvil head 32.

[0044] The retaining ring 40 is fixed to the post 44 of the anvil head 32 and restricts outward movement of the anvil plate 34 relative to the anvil head 32. In aspects of the present disclosure, the anvil shaft 30 of the anvil assembly 18 defines an annular slot 72 that receives the retaining ring 40 and fixes the retaining ring 40 to the post 44. The retaining ring 40 extends outwardly from the post 44 and engages the distal surface of the anvil plate 34 to restrict distal movement of the anvil plate 34. In aspects of the present disclosure, the retaining ring 40 is in the form of a split ring that defines a slit 40a that allows the retaining ring 40 to flex outwardly about the anvil shaft 30. When the distal surface of the anvil plate 34 engages the retaining ring 40, the anvil plate 34 is in its most proximal position. In aspects of the present disclosure, the anvil plate 34 can move from its most proximal position where it engages the anvil head 32 and the retaining ring 40 to its most distal position where the distal surface 66a of the anvil plate 34 engages the annular edge 62 of the anvil head 32. In some aspects of the present disclosure, the gap "G" ( Figure 4 ) defined between the annular edge 62 and the proximal surface of the anvil plate 34 is from about zero to about 1 mm. Alternatively, the size and characteristics of the biasing member 36 (e.g., the wave spring 36a) can be selected to provide a greater or lesser degree of movement of the anvil plate 34 relative to the anvil head 32.

[0045] The nail forming portion 66 of the anvil plate 34 defines a plurality of nail forming pits 76 that are positioned to receive nails 28( Figure 6 ), which are ejected from the nail cartridge of the reload assembly 16( Figure 1 ) when the suturing device 10( Figure 6 ) is fired. In aspects of the present disclosure, the nail forming pits 76 are arranged to form one or more annular rows in the distal surface of the nail forming portion 66 of the anvil plate 34. The inner body portion 68 of the anvil plate 34 defines an annular cavity 82 that is positioned around an opening 70 and houses the cutting ring 38.

[0046] The cutting ring 38 has an annular configuration and defines an opening 38a that receives the post 44 of the anvil head 32 and is supported on the distally facing surface of the anvil plate 34. The cutting ring 38 is positioned to receive the blade 29( Figure 6 ) of the reload assembly 16 when the suturing device 10 is fired. In aspects of the present disclosure, the anvil plate 34 includes an annular protrusion 86( Figure 6 ) that extends around the cavity 82, and the cutting ring 38 includes an outwardly extending rib 88 that engages the annular protrusion 86 to retain the cutting ring 38 within the cavity 82 of the anvil plate 34.

[0047] Figure 5 and Figure 6 illustrate the distal portion of the suturing device 10 with medium - thickness tissue clamped between the anvil assembly 18 and the reload assembly 16. When the suturing device 10 is clamped around the tissue T1, the tissue T1 is compressed between the nail forming portion 66 of the anvil plate 34 and the nail cartridge 27 of the reload assembly 16. When the tissue T1 is clamped between the reload assembly 16 and the anvil plate 34, a force is applied to the anvil plate 34 to compress the wave spring 36a. When the wave spring 36a is compressed, the anvil plate 34 moves away from the reload assembly 16 to increase the gap defined between the anvil plate 34 and the nail cartridge 27 of the reload assembly 16 and to decrease the gap "G1" between the annular edge 62 of the anvil head 32 and the distal surface 66a of the anvil plate 34. When the tissue is thinner than the tissue T1, the wave spring 36a will be compressed to a lesser extent, such that the gap between the nail cartridge 27 of the reload assembly 16 and the anvil plate 34 of the anvil assembly 18 will be smaller and the gap between the annular edge 62 of the anvil head 32 and the distal surface 66a of the anvil plate 34 will be larger.

[0048] Figure 7 and Figure 8Illustrates the distal portion of the suturing device 10, where the thicker tissue T2 is clamped between the anvil assembly 18 and the reload assembly 16. When the suturing device 10 is clamped around the tissue T2, the tissue T2 is compressed between the staple-forming portion 66 of the anvil plate 34 and the staple cartridge 27 of the reload assembly 16. When the tissue T2 is clamped between the reload assembly 16 and the anvil plate 34, a force is applied to the anvil plate 34 to compress the wave spring 36a. When the wave spring 36a is compressed, the anvil plate 34 moves away from the reload assembly 16 to further increase the gap defined between the anvil plate 34 and the staple cartridge 27 of the reload assembly 16 and to decrease the gap between the annular edge 62 of the anvil head 32 and the distal surface 66a of the anvil plate 34.

[0049] Those skilled in the art will understand that the devices and methods specifically described herein and shown in the drawings are non-limiting exemplary aspects of the present disclosure. It is contemplated that, without departing from the scope of the present disclosure, the elements and features described or illustrated in connection with one exemplary aspect of the present disclosure may be combined with the elements and features of another aspect. Similarly, those skilled in the art will understand additional features and advantages of the present disclosure based on the foregoing aspects of the present disclosure. Accordingly, the present disclosure is not limited by what has been specifically shown and described, unless indicated by the appended claims.

Claims

1. An anvil assembly, the anvil assembly comprising: An anvil shaft having a proximal portion and a distal portion; An anvil head including a body portion and an anvil post fixed to the body portion, the anvil post being fixed to the distal portion of the anvil shaft, the anvil head having a stepped inner surface that includes an outer annular support surface and an inner recessed surface located distal to the outer annular support surface, the inner recessed surface defining a cavity; An anvil plate having a stepped circular configuration and including a proximal nail forming portion and an inner body portion, the inner body portion being received within the cavity defined by the inner recessed surface of the anvil head, the proximal nail forming portion of the anvil plate having a distal surface and an annular proximal surface defining a nail forming pit, the anvil plate being movable relative to the anvil head between a most proximal position and a most distal position; And A biasing member supported on the outer annular support surface of the anvil head, the biasing member engaging the distal surface of the proximal nail forming portion of the anvil plate to urge the anvil plate toward the most proximal position.

2. The anvil assembly according to claim 1, wherein the anvil assembly further comprises: A retaining ring fixed to the anvil post, the retaining ring being positioned to engage the anvil plate to prevent the anvil plate from moving distally beyond the most distal position.

3. The anvil assembly according to claim 2, wherein the biasing member comprises a wave spring.

4. The anvil assembly according to claim 2, wherein the biasing member comprises a compressible washer.

5. The anvil assembly according to claim 2, wherein the biasing member comprises a helical spring.

6. The anvil assembly according to claim 1, wherein the body of the anvil head includes an annular edge positioned around the outer annular support surface of the anvil head.

7. The anvil assembly according to claim 6, wherein the annular edge of the body of the anvil head is positioned to engage the distal surface of the anvil plate to prevent the anvil plate from moving proximally beyond the most proximal position.

8. The anvil assembly according to claim 1, wherein the anvil shaft is pivotally coupled to the anvil post by a pivot pin.

9. The anvil assembly according to claim 2, wherein the anvil post defines an annular slot that receives the retaining ring.

10. The anvil assembly according to claim 9, wherein the retaining ring defines a slit to facilitate placement of the retaining ring around the anvil shaft.

11. An anvil assembly, the anvil assembly comprising: An anvil shaft; An anvil head including a body portion and an anvil post, the anvil post being fixed to the anvil shaft, the anvil head having a stepped inner surface that includes an outer annular support surface and an inner recessed surface located distal to the outer annular support surface, the inner recessed surface defining a cavity; An anvil plate, the anvil plate including a proximal nail forming portion and an internal body portion, the internal body portion being received within the cavity defined by the internal recessed surface of the anvil head, the proximal nail forming portion of the anvil plate having a distal surface, the anvil plate being movable relative to the anvil head between a most proximal position and a most distal position; A biasing member, the biasing member being supported on the external annular support surface of the anvil head, the biasing member engaging the distal surface of the proximal nail forming portion of the anvil plate to urge the anvil plate toward the most proximal position; and A retaining ring, the retaining ring being fixed to the anvil post, the retaining ring being positioned to engage the anvil plate to prevent the anvil plate from moving distally beyond the most distal position.

12. The anvil assembly according to claim 11, wherein the biasing member includes a wave spring.

13. The anvil assembly according to claim 11, wherein the biasing member includes a compressible washer.

14. The anvil assembly according to claim 11, wherein the biasing member includes a helical spring.

15. The anvil assembly according to claim 11, wherein the body of the anvil head includes an annular edge positioned around the external annular support surface of the anvil head.

16. The anvil assembly according to claim 15, wherein the annular edge of the body of the anvil head is positioned to engage the distal surface of the anvil plate to prevent the anvil plate from moving proximally beyond the most proximal position.

17. The anvil assembly according to claim 11, wherein the anvil shaft is pivotally coupled to the anvil post by a pivot pin.

18. The anvil assembly according to claim 11, wherein the anvil post defines an annular slot that receives the retaining ring.

19. The anvil assembly according to claim 18, wherein the retaining ring defines a slit to facilitate placement of the retaining ring around the anvil shaft.

20. A suturing device, the suturing device including: An adapter assembly having a proximal portion and a distal portion and including an anvil retainer; A reload assembly supported on the distal portion of the adapter assembly, the reload assembly including a housing and a staple cartridge that supports staples; and An anvil assembly including: An anvil shaft having a proximal portion and a distal portion, the proximal portion of the anvil shaft being coupled to the anvil retainer; An anvil head including a body portion and an anvil post, the anvil post being fixed to the distal portion of the anvil shaft, the anvil head having a stepped inner surface that includes an external annular support surface and an internal recessed surface positioned distal to the external annular support surface, the internal recessed surface defining a cavity; An anvil plate, the anvil plate having a stepped circular configuration and including a proximal nail forming portion and an internal body portion, the internal body portion being received within the cavity defined by the internal recessed surface of the anvil head, the proximal nail forming portion of the anvil plate having a distal surface and an annular proximal surface defining a nail forming pit, the anvil plate being movable relative to the anvil head between a most proximal position and a most distal position; and A biasing member, the biasing member being supported on the external annular support surface of the anvil head, the biasing member engaging the distal surface of the proximal nail forming portion of the anvil plate to urge the anvil plate toward the proximal position.

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