EP4637579A1

EP4637579A1 - Surgical stapling device with tissue gap control

Info

Publication number: EP4637579A1
Application number: EP23825638.2A
Authority: EP
Inventors: David A. Nicholas; Stanislaw Z. Marczyk; John W. Beardsley
Original assignee: Covidien LP
Current assignee: Covidien LP
Priority date: 2022-12-20
Filing date: 2023-12-15
Publication date: 2025-10-29
Also published as: CN120379601A; WO2024134423A1

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 and a proximal-most position to vary the size of the tissue gap between the anvil assembly and the reload assembly to accommodate tissues of varying thicknesses.

Description

SURGICAL STAPLING DEVICE WITH TISSUE GAP CONTROL

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

FIELD

[0002] This disclosure is directed to surgical stapling devices and, more particularly, to surgical stapling devices that have a tool assembly for accommodating an expanded range of tissue thickness.

BACKGROUND

[0003] Surgical stapling devices for ejecting staples to join tissue or tissue segments in a fast and efficient manner in a variety of surgical procedures, e.g., anastomoses procedures, are well known. Typically, 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 movement of the tool assembly between open and clamped positions. In the clamped position, the staple cartridge of the cartridge assembly and the anvil are supported in juxtaposed alignment and include tissue contact surfaces that define a predetermined tissue gap. The tissue gap and the size of the staples within the staple cartridge are dimensioned for use on tissue having thickness within a predetermined range of thicknesses to properly effect hemostasis. If the tissue positioned between the jaws is outside the predetermined range, i.e., either too thick or too thin, the staples ejected from the staple cartridge of the cartridge assembly may be malformed and not provide effective hemostasis. In addition, if the tissue thickness is misidentified by the clinician or if the tissue thickness falls near the outer edges of the range for a given staple size, the effectiveness of hemostasis could be affected.

[0004] A continuing need exists in the suturing arts for a surgical stapling device that can provide effective hemostasis for a greater range of tissue thicknesses.

SUMMARY [0005] This disclosure is directed to surgical stapling device that includes a handle assembly, an adaptor assembly, a reload assembly, and an anvil assembly that is supported on a distal portion of the adaptor assembly and is movable in relation to the reload assembly between unclamped and clamped positions. In the clamped position, the anvil assembly and the reload assembly define a tissue gap that is dimensioned 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 distal-most position and a proximal-most position to vary the size of the tissue gap between the anvil assembly and the reload assembly to accommodate tissues of varying thicknesses.

[0006] Aspects of the disclosure are directed to an anvil assembly including 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 that is secured to the body portion. The anvil post is secured 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 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 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 staple forming pockets. The anvil plate is movable in relation to the anvil head between a proximal- most position and a distal-most 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 urge the anvil plate towards the proximal-most position.

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

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

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

[0010] In aspects of the disclosure, the biasing member includes a coil spring. [0011] In some aspects of the disclosure, the body of the anvil head includes an annular rim that is positioned about the outer annular support surface of the anvil head.

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

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

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

[0015] In certain aspects of the disclosure, the retaining ring defines a slit that facilitates placement of the retaining ring about the anvil shaft.

[0016] Other aspects of the disclosure are directed to an anvil assembly including 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 secured 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 distally of 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 in relation to the anvil head between a proximal-most position and a distal-most 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 urge the anvil plate towards the proximal position. The retaining ring is secured to the anvil post and is positioned to engage the anvil plate to prevent movement of the anvil plate distally beyond the distal-most position.

[0017] Other aspects of the disclosure are directed to a stapling device that includes an adaptor assembly, a reload assembly, and an anvil assembly. The adaptor 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 adaptor 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 secured 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 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 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 staple forming pockets. The anvil plate is movable in relation to the anvil head between a proximal-most position and a distal-most 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 urge the anvil plate towards the proximal position.

[0018] Other aspects of the disclosure will be appreciated from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Various aspects of the disclosed surgical stapling device are described herein below with reference to the drawings, wherein:

[0020] FIG. 1 is a side perspective view of a surgical stapling device including aspects of the disclosure with the stapling device in an open position;

[0021] FIG. 2 is a side perspective view of an anvil assembly of the surgical stapling device shown in FIG. 1 ;

[0022] FIG. 3 is an exploded, side perspective view of the anvil assembly shown in FIG. 2;

[0023] FIG. 3A is a side perspective view of a biasing member of the anvil assembly shown in FIG. 3;

[0024] FIG. 4 is a cross-sectional view taken along section line 4-4 of FIG. 2;

[0025] FIG. 5 is a side perspective view of a distal portion of the surgical stapling device shown in FIG. 1 with the distal portion of the surgical stapling device shown in phantom and positioned within a body lumen in a clamped position clamped about thin tissue;

[0026] FIG. 6 is a cross-sectional view taken along section line 6-6 of FIG. 5; [0027] FIG. 7 is a side perspective view of a distal portion of the surgical stapling device shown in FIG. 1 with the distal portion of the surgical stapling device shown in phantom and positioned within a body lumen in a clamped position clamped about thick tissue;

[0028] FIG. 8 is a side perspective view of a distal portion of the surgical stapling device shown in FIG. 1 with the distal portion of the surgical stapling device shown in phantom and positioned within a body lumen in a clamped position clamped uneven tissue;

[0029] FIG. 9 is a side perspective view of an alternate version of the biasing member of the anvil assembly shown in FIG. 3;

[0030] FIG. 10 is a side cross-sectional view of the anvil assembly of the surgical stapling device shown in FIG. 1 including the alternate version of the biasing member shown in FIG. 9;

[0031] FIG. 11 is a side perspective view of another alternate version of the biasing member of the anvil assembly shown in FIG. 3; and

[0032] FIG. 12 is a side cross-sectional view of the anvil assembly of the surgical stapling device shown in FIG. 1 including the alternate version of the biasing member shown in FIG. 11.

DETAILED DESCRIPTION

[0033] The disclosed surgical stapling device will now be described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. However, it is to be understood that the disclosed aspects of the surgical stapling device are merely exemplary of the disclosure and may be embodied in various forms. Well-known functions or constructions of the surgical stapling device are not described in detail to avoid obscuring the disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the disclosure in virtually any appropriately detailed structure.

[0034] In this description, the term “proximal” is used generally to refer to that portion of the device that is closer to a clinician when the device is used in its customary fashion, while the term “distal” is used generally to refer to that portion of the device that is farther from the clinician when the device is used in its customary fashion. In addition, the term “clinician” is used generally to refer to medical personnel including doctors, nurses, and support personnel. Further, directional terms such as front, rear, upper, lower, top, bottom, and similar terms are used to assist in understanding the description and are not intended to limit the disclosure.

[0035] The disclosed surgical stapling device includes a handle assembly, an adaptor assembly, a reload assembly, and an anvil assembly that is supported on a distal portion of the adaptor assembly and is movable in relation to the reload assembly between unclamped and clamped positions. In the clamped position, the anvil assembly and the reload assembly define a tissue gap that is dimensioned 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 distal-most position and a proximal-most position to vary the size of the tissue gap between the anvil assembly and the reload assembly to accommodate tissues of varying thicknesses. In aspects of the disclosure, the cartridge assembly and anvil assembly have annular configurations.

[0036] FIG. 1 illustrates a circular stapling device according to aspects of the disclosure shown generally as stapling device 10. The stapling device 10 includes a handle assembly 12, an elongate body or adaptor assembly 14, a reload assembly 16, and an anvil assembly 18. The anvil assembly 18 is releasably supported on a distal end of the adaptor assembly 14 and is movable in relation to the reload assembly 16 between spaced and clamped positions as is known in the art. More specifically, the anvil assembly 18 is releasably coupled to an anvil retainer 19 (FIG. 6) of the adaptor assembly 14 and is movable with the anvil retainer 19 in relation to the reload assembly 16 between unclamped and clamped positions.

[0037] The reload assembly 16 includes a proximal portion 16a that is releasably coupled to a distal portion 14a of the adaptor assembly 14. Alternately, the reload assembly 16 can be fixedly secured to the distal portion 14a of the adaptor assembly 14. In certain aspects of the disclosure, the handle assembly 12 includes a stationary grip 22 that supports actuation buttons 24 for controlling operation of various functions of the stapling device 10 including approximation of the reload assembly 16 and the anvil assembly 18, firing of staples from the reload assembly 16, and cutting or coring of tissue.

[0038] The reload assembly 16 includes a housing 26 that supports an annular staple cartridge 27 that includes staples 28 (FIG. 6). The reload assembly 16 also includes an annular knife 29 (FIG. 6) that is movable through annular staple cartridge 27 into engagement with the cut ring 38 of the anvil assembly 18. [0039] The stapling device 10 is illustrated as an electrically powered stapling device and includes the handle assembly 12 which may support one or more batteries (not shown). The adaptor assembly 14 translates power from the handle assembly 12 to the reload and anvil assemblies 16 and 18. Examples of electrically powered 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. Alternately, it is envisioned that the stapling device 10 can also be a manually powered stapling device such as disclosed in U.S. Patent No. 7,303,106 (the ’106 Patent) or a stapling device that is configured for use with a robotic system such as disclosed in U.S. Patent No. 9,962,159 that does not include a handle assembly.

[0040] FIGS. 2-4 illustrate the anvil assembly 18 which includes an anvil shaft 30, an anvil head 32, an anvil plate 34, a biasing member 36, a cut ring 38, and a retaining ring 40. The anvil head 32 includes a body portion 42 and a post 44 that is centrally located and extends proximally from the body portion 42. In aspects of the disclosure, the post 44 defines a transverse through bore 46. The anvil head 32 is coupled to the anvil head 30 by a pivot pin 48 that extends through an opening 50 in a distal portion of the anvil shaft 30 and through the through bore 46 in the post 44 to secure the anvil head 32 to the anvil shaft 30 for pivotable movement from an operative 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 envisioned that the anvil head 32 can be fixedly secured 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 that is positioned 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 positioned inwardly of the support surface 56. In aspects of the 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 to atmosphere. The anvil head 32 includes an annular rim 62 that extends proximally from and about the support surface 56.

[0042] The anvil plate 34 includes a body 64 that has a stepped, circular configuration and includes a staple forming portion 66 and an inner body portion 68 that is positioned 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 positioned proximally of the support surface 56 of the anvil head 32. The staple forming portion 66 has a diameter that corresponds to the diameter of the anvil head 32 and includes a distal surface 66a (FIG. 4) that is positioned to engage the annular rim 62 of the anvil head 32 when the inner body portion 68 moves 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 in which the distal surface 66a of the staple forming portion 66 of the anvil plate 34 is spaced from the annular rim 62 of the anvil head 32. In aspects of the disclosure, the biasing member 36 is in the form of a wave spring 36a that has a sinusoidal or wave-like configuration. In some aspects of the disclosure, the wave spring 36a is formed from spring steel although other materials of construction are envisioned. In some aspects of the disclosure, the wave spring 36a is secured to the support surface 56 by spot welding. It is envisioned that the wave spring 36a can be secured to the support surface 56 using other fastening techniques or devices or not be secured to the support surface of the anvil head 32 at all. It is also envisioned that the biasing member 36 can be formed using one or more springs of a different type. For example, as shown in FIGS. 9 and 10, 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 shown in FIGS. 11 and 12, the biasing member can be in the form of a coil 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 secured to the post 44 of the anvil head 32 and limits outward movement of the anvil plate 34 in relation to the anvil head 32. In aspects of the disclosure, the of the anvil shaft 30 of the anvil assembly 18 defines an annular slot 72 that receives the retaining ring 40 and secures the retaining ring 40 to the post 44. The retaining ring 40 extends outwardly of the post 44 and engages a distal surface of the anvil plate 34 to limit distal movement of the anvil plate 34. In aspects of the 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 When the distal surface of the anvil plate 34 is engaged with the retaining ring 40, the anvil plate 34 is in the proximal-most position. In aspects of the disclosure, the anvil plate 34 is movable from the proximal-most position in which the anvil head 32 is engaged with the retaining ring 40 to a distal-most position in which the distal surface 66a of the anvil plate 34 is engaged with the annular rim 62 of the anvil head 32. In some aspects of the disclosure, a gap “G” (FIG. 4) defined between the annular rim 62 and the proximal surface of the anvil plate 34 is from about zero to about 1 mm. Alternately, the dimensions and characteristics of the biasing member 36, e.g., wave spring 36a, can be selected to provide a greater or lesser degree of movement of the anvil plate 34 in relation to the anvil head 32.

[0045] The staple forming portion 66 of the anvil plate 34 defines a plurality of staple forming pockets 76 that are positioned to the receive staples 28 (FIG. 6) that are ejected from a staple cartridge (FIG. 6) of the reload assembly 16 when the stapling device 10 (FIG. 1) is fired. In aspects of the disclosure, the staple forming pockets 76 are arranged in one or more annular rows that formed in a distal surface of the staple 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 about the opening 70 and receives the cut ring 38.

[0046] The cut 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 a distally facing surface of the anvil plate 34. The cut ring 38 is positioned to receive the knife blade 29 (FIG. 6) of the reload assembly 16 when the stapling device 10 is fired. In aspects of the disclosure, the anvil plate 34 includes an annular protrusion 86 (FIG. 6) that extends about the cavity 82, and the cut ring 38 includes an outwardly extending rib 88 that is engaged with the annular protrusion 86 to retain the cut ring 38 within the cavity 82 of the anvil plate 34.

[0047] FIGS. 5 and 6 illustrate the distal portion of the stapling device 10 with tissue having a medium thickness clamped between the anvil assembly 18 and the reload assembly 16. When the stapling device 10 is clamped about tissue Tl, the tissue T1 is compressed between the staple forming portion 66 of the anvil plate 34 and the staple cartridge 27 of the reload assembly 16. As the tissue Tl 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 compresses, the anvil plate 34 moves away from the reload assembly 16 to increase the gap defined between the anvil plate 34 and the staple cartridge 27 of the reload assembly 16 and decrease the gap “Gl” between the annular rim 62 of the anvil head 32 and the distal surface 66a of the anvil plate 34. When the tissue is thinner than the tissue Tl, the wave spring 36a will compress to a lesser degree such that the gap between the staple 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 rim 62 of the anvil head 32 and the distal surface 66a of the anvil plate 34 will be larger.

[0048] FIGS. 7 and 8 illustrate the distal portion of the stapling device 10 with thicker tissue T2 is clamped between the anvil assembly 18 and the reload assembly 16. When the stapling device 10 is clamped about 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. As 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 compresses, 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 eliminate the gap between the annular rim 62 of the anvil head 32 and the distal surface 66a of the anvil plate 34.

[0049] Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary aspects of the disclosure. It is envisioned that the elements and features illustrated or described in connection with one exemplary aspects of the disclosure may be combined with the elements and features of another without departing from the scope of the disclosure. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the abovedescribed aspects of the disclosure. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims.

Claims

WHAT IS CLAIMED IS:

1. An 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 secured to the body portion, the anvil post secured 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 positioned distally of the outer annular support surface, the inner recessed surface defining a cavity; an anvil plate having a stepped circular configuration and including a proximal staple forming portion and an inner body portion, the inner body portion received within the cavity defined by the inner recessed surface of the anvil head, the proximal staple forming portion of the anvil plate having a distal surface and an annular proximal surface defining staple forming pockets, the anvil plate movable in relation to the anvil head between a proximal-most position and a distal-most 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 staple forming portion of the anvil plate to urge the anvil plate towards the proximal-most position.

2. The anvil assembly of claim 1, further including a retaining ring secured to the anvil post, the retaining ring positioned to engage the anvil plate to prevent movement of the anvil plate distally beyond the distal-most position.

3. The anvil assembly of claim 2, wherein the biasing member includes a wave spring.

4. The anvil assembly of claim 2, wherein the biasing member includes a compressible washer.

5. The anvil assembly of claim 2, wherein the biasing member includes a coil spring.

6. The anvil assembly of claim 1 , wherein the body of the anvil head includes an annular rim that is positioned about the outer annular support surface of the anvil head.

7. The anvil assembly of claim 6, wherein the annular rim of the body of the anvil head is positioned to engage the distal surface of the anvil plate to prevent movement of the anvil plate proximally beyond the proximal-most position.

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

9. The anvil assembly of claim 2, wherein the anvil post defines an annular slot, the annular slot receiving the retaining ring.

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

11. An anvil assembly comprising: an anvil shaft; an anvil head including a body portion and an anvil post, the anvil post secured to the anvil shaft, the anvil head having a stepped inner surface that includes an outer annular support surface and an inner recessed surface positioned distally of the outer annular support surface, the inner recessed surface defining a cavity; an anvil plate including a proximal staple forming portion and an inner body portion, the inner body portion received within the cavity defined by the inner recessed surface of the anvil head, the proximal staple forming portion of the anvil plate having a distal surface, the anvil plate movable in relation to the anvil head between a proximal-most position and a distal-most position; a biasing member supported on the outer annular support surface of the anvil head, the biasing member engaging the distal surface of the proximal staple forming portion of the anvil plate to urge the anvil plate towards the proximal-most position; and a retaining ring secured to the anvil post, the retaining ring positioned to engage the anvil plate to prevent movement of the anvil plate distally beyond the distal-most position.

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

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

14. The anvil assembly of claim 11, wherein the biasing member includes a coil spring.

15. The anvil assembly of claim 11, wherein the body of the anvil head includes an annular rim that is positioned about the outer annular support surface of the anvil head.

16. The anvil assembly of claim 15, wherein the annular rim of the body of the anvil head is positioned to engage the distal surface of the anvil plate to prevent movement of the anvil plate proximally beyond the proximal-most position.

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

18. The anvil assembly of claim 11, wherein the anvil post defines an annular slot, the annular slot receiving the retaining ring.

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

20. A stapling device comprising: an adaptor assembly having a proximal portion and a distal portion and including an anvil retainer; a reload assembly supported on the distal portion of the adaptor assembly, the reload assembly including a housing and a staple cartridge, the staple cartridge supporting staples; and an anvil assembly including: an anvil shaft having a proximal portion and a distal portion, the proximal portion of the anvil shaft coupled to the anvil retainer; an anvil head including a body portion and an anvil post, the anvil post secured 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 positioned distally of the outer annular support surface, the inner recessed surface defining a cavity; an anvil plate having a stepped circular configuration and including a proximal staple forming portion and an inner body portion, the inner body portion received within the cavity defined by the inner recessed surface of the anvil head, the proximal staple forming portion of the anvil plate having a distal surface and an annular proximal surface defining staple forming pockets, the anvil plate movable in relation to the anvil head between a proximal-most position and a distal-most 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 staple forming portion of the anvil plate to urge the anvil plate towards the proximal position.