Tilt anvil assembly

[0001] 1. Technical Field

[0002] The present disclosure relates generally to an anvil assembly which is suitable for use with a circular anastomosis stapler. More specifically, the present disclosure relates to an anvil assembly having a tiltable head which is suitable for use with a circular anastomosis stapler.

[0003] 2. Background of Related Art

[0004] Circular anastomosis staplers which include an anvil assembly having a tiltable anvil head are known in the art. One such circular anastomosis stapler is disclosed in U.S. patent application Ser. No. 10/968,722 (“'722 application”) which is incorporated herein by reference in its entirety. In some known circular anastomosis staplers, a backup plate located within the anvil assembly is positioned to prevent tilting of the anvil head of the anvil assembly prior to firing of the stapler. Upon firing of the stapler, a knife blade of the stapler engages and moves the backup plate to a position which allows the anvil head to tilt upon retraction of the knife blade. If the backup plate sticks to the knife blade upon retraction of the knife blade, the backup plate may return to its position preventing tilting of the anvil head. Thus, the anvil head will not tilt.

[0005] In order to prevent the backup member from sticking to the knife blade, the '722 application discloses a retainer clip which engages the backup plate upon retraction of the knife blade. Although, the retainer clip is effective, other devices for preventing retraction of the backup plate are desired.

[0006] A tilt anvil assembly is disclosed which includes a center rod and an anvil head assembly including a housing, a post, an anvil plate having staple deforming pockets, and a backup member. The head assembly is pivotally secured to the center rod and pivotal in relation to the center rod between a non-tilted position and a tilted position. The backup member is movable about the post from a first position in which a portion of the backup member is positioned to prevent movement of the head assembly from the non-tilted position to the tilted position to a second position in which the backup member is positioned to accommodate movement of the head assembly in relation to the center rod from the non-tilted position to the tilted position. The anvil assembly further includes a pivotal latch member positioned in the head assembly to prevent movement of the backup member from the second position to the first position.

[0007] In one embodiment, the head assembly is pivotally secured to the center rod about a pivot member and the pivotal latch member is pivotally mounted about the pivot member. The pivotal latch member is spring loaded and positioned to engage an inner periphery of the backup member when the backup member is in the non-tilted position. When the backup member is moved to its second position, the latch member is urged by the spring to a position engaging and in front of the backup member to urge the head assembly to the tilted position and prevent movement of the backup member from the second position to the first position.

[0008] In one embodiment, the anvil assembly further includes a retainer member positioned in the head assembly to prevent movement of the backup member from the first position to the second position until a predetermined force has been applied to the backup member. The predetermined force is between about ten pounds and about ninety pounds. The retainer member can include a deformable member which is positioned in the head assembly between the housing and the backup member. In one embodiment, the housing and the post define an annular recess and the retainer member is positioned in the annular recess. The retainer member can include an annular body which is positioned about the post and a plurality of deformable tabs extending therefrom. The backup member is positioned to abut the retainer member such that upon movement of the backup member from its first position to its second position, the deformable tabs are deformed.

[0009] In one embodiment, the backup member includes a cutting ring and a backup plate. The cutting ring can be secured to a proximal face of the backup plate. The backup plate can include at least one finger positioned to engage a distal surface of the center rod when the backup member is in its first position to prevent pivotal movement of the head assembly in relation to the center rod. The cutting ring can be formed from a softer material than the backup plate. In one embodiment, the cutting ring is formed from polyethylene and the backup plate is formed from a metal.

[0024] Embodiments of the presently disclosed tilt anvil assembly 10 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.

[0025] FIGS. 1-10 illustrate a tilt anvil assembly 10 which is suitable for use with a surgical stapling device for performing, for example, circular anastomoses of hollow tissue organs and hemorrhoid surgeries. Referring to FIGS. 1-3, anvil assembly 10 includes a head assembly 12 and a center rod assembly 14. Head assembly 12 includes a post 16, a housing 18, a backup member or plate 20, a cutting ring 22, a cutting ring cover 23, an anvil plate 24, a cam latch member 26, and a retainer member 27. Post 16 is monolithically formed with and centrally positioned within head 18. Alternately, head 18 and post 16 may be formed separately and fastened together using a known fastening technique, e.g., welding. Anvil plate 24 is supported in an outer annular recess 28 (FIG. 3) of housing 18 and includes a plurality of staple deforming pockets 30 for receiving and deforming staples. At least one tab 24a extends radially outwardly from anvil plate 24 and is received within a cutout 32 formed in an outer rim of housing 18. Tab 24a and cutout 32 function to align or properly position anvil plate 24 within annular recess 28 of housing 18.

[0026] Referring to FIG. 3, backup plate 20 includes a central opening 34 which is positioned about post 16 within an inner annular recess 36 of housing 18 between post 16 and outer annular recess 28. Backup plate 20 includes a raised platform 20a. Cutting ring 22 includes an opening 22a having a configuration substantially the same as platform 20a. Although platform 20a is illustrated as having a circular shape, other configurations are envisioned, e.g., square, rectangular, triangular, etc. In one embodiment, cutting ring 22 is formed from polyethylene and is fixedly secured to backup plate 20 using, for example, an adhesive, to form a backup plate/cutting ring assembly. Backup plate 20 is formed from a hard material, e.g., a metal. Alternately other materials of construction may be used to construct backup plate 20 and cutting ring 22. Further, backup plate 20 and cutting ring 22, in the alternative, can be formed as a single or unitary structure.

[0027] A cutting ring cover 23 is secured to a outwardly facing or proximal surface 40 of cutting ring 22 using, for example, an adhesive. In one embodiment, cutting ring cover 23 is formed from a material or materials, which have a hardness greater than that of the cutting ring, e.g., mylar. In one embodiment, cutting ring cover 23 includes two layers of mylar (not shown) which are joined together using an adhesive and a polypropylene coating. Alternately, cutting ring 22 need not have a cover. Cutting ring 22 and backup plate 20 are slidably mounted about post 16. Backup plate 20 includes a pair of inwardly extending fingers 38 which will be described in further detail below.

[0028] Retainer member 27 is positioned in inner annular recess 36 between backup plate 20 and a back wall 18a (FIG. 3) of housing 18. In one embodiment, retainer member 27 is annular and includes a plurality of deformable tabs 27a which engage a rear surface of backup plate 20. Retainer member 27 prevents backup plate 20 and cutting ring 22 from moving or being pushed into inner annular recess 36 of housing 18 until a predetermined force sufficient to deform tabs 27a has been applied to the backup plate/cutting ring assembly. The predetermined force can be close to but is less than the force applied by an annular cutting blade of a surgical stapling device when it engages, for example, the cutting ring of anvil assembly 10. The predetermined force is preferably between about ten pounds and about ninety pounds and is most preferably about thirty (30) pounds. When the predetermined force is reached, e.g., during cutting of tissue, backup plate 20 is urged into inner annular recess 36 and compresses retainer member 27. It is envisioned that other crushable, deformable, collapsible or movement restricting members may be used to retain the backup plate/cutting ring assembly in a fixed position until a predetermined force has been applied to the backup plate/cutting ring assembly.

[0029] Anvil center rod assembly 14 includes a center rod 52, a plunger 54 and plunger spring 56. A first end of center rod 52 has a pair of arms 59 which define a cavity 59a (FIG. 3). Each arm 59 has a transverse throughbore 58 which is aligned with a central longitudinal axis of center rod 52. Alternately, throughbores 58 can be offset from the longitudinal axis of center rod 52. Post 16 of anvil head assembly 12 is dimensioned to be positioned within cavity 59a and also includes a transverse throughbore 60. A pivot member 62 pivotably secures post 16 to center rod 52 via throughbores 58 and 60 such that anvil head assembly 12 is pivotably mounted to anvil center rod assembly 14.

[0030] Referring to FIGS. 3 and 6-9, cam latch member 26 includes a body 26a having a throughbore 26b. Throughbore 26b is dimensioned to receive pivot member 62 such that cam latch member 26 is pivotally mounted within transverse slot 72 (FIG. 3) of post 16 about pivot member 62. As shown in FIGS. 4, 6 and 7 (see also FIG. 2), cam latch member 26 includes a first body portion 26c which extends partially from slot 72 of post 16 and is positioned to be engaged by finger 66 of plunger 54. Cam latch member 26 also includes an edge 26f which is urged into engagement with an inner periphery of backup plate 20 by finger 66 of plunger 54 when anvil head 12 is in its non-tilted or operative position.

[0031] Plunger 54 is slidably positioned in a bore 64 (FIG. 6) formed in the first end of center rod 52. Plunger 54 includes an engagement finger 66 which is offset from the pivot axis of anvil head assembly 12 and biased into engagement with an edge 26c of cam latch 26. As will be discussed in further detail below, engagement of finger 66 with edge 26c of cam latch 26 presses edge 26f against an inner periphery of back plate 20 to urge anvil head assembly 12 to a pivoted or tilted position on center rod 52. In a preferred position, fingers 38 formed on backup plate 20 engage protrusions 52b adjacent top surface 52a of center rod 52 to prevent anvil head assembly 12 from pivoting about pivot member 62. When anvil assembly 10 is attached to a surgical stapling device and the device is fired such as disclosed in the manner described in the '722 application, backup plate 20 and cutting ring 22 are pushed into inner annular recess 36 of housing 18 about post 16 by a knife blade (not shown) to move fingers 38 away from and out of engagement with protrusions 52b of center rod 52 (FIG. 10) and permit plunger 54 to pivot anvil head assembly 12 about pivot member 62. Retainer member 27 prevents inadvertent or premature movement of backup plate 20 into inner-annular recess 36 to prevent premature or inadvertent tilting of anvil head assembly 12.

[0032] Referring to FIGS. 7A and 7B, a second end of center rod 52 includes a bore 80 defined by a plurality of flexible arms 82. Flexible arms 82 each include an opening 82a dimensioned to receive a projection formed on or connected to a removable trocar (not shown) or the like. The distal ends of each of flexible arms 82 include an internal shoulder 84 (FIG. 6) dimensioned to releasably engage the anvil retainer of a surgical stapling device (not shown) to secure anvil assembly 10 to the surgical stapling device. A plurality of splines 86 are formed about center rod 52. Splines 86 function to align anvil assembly 10 with the staple holding portion of a surgical stapling device. Center rod 52 also includes an annular recessed portion 90 to facilitate grasping of anvil assembly 10 by a surgeon with a grasper. Recessed portion 90 may include a roughened or knurled surface or an overmold to facilitate grasping of anvil assembly 10.

[0033] Referring to FIGS. 6-7B, when anvil assembly 10 is in its preferred non-tilted position, backup plate 20 is spaced from back wall 18a of housing 18 by retainer 27 and protrusions 52b of center rod 52 engage fingers 38 of backup plate 20 to prevent tilting of anvil head assembly 12 about pivot member 62. As shown in FIG. 7, finger 66 of plunger 54 is urged by spring 56 into engagement with body portion 26c of cam latch member 26 to urge cam latch member 26 in a clockwise direction about pivot member 62 such that edge 26f of cam latch member 26 engages an inner periphery 20b of backup member 20.

[0034] Referring to FIGS. 8-9A, when anvil assembly 10 is attached to a stapling device and the device is fired, a knife blade (not shown) of the stapling device engages cutting ring 22 to move cutting ring 22 and backup plate 20 in the direction indicated by arrow “W” in FIG. 9 into annular recess 36 of housing 18 of anvil head assembly 12. When this occurs, deformable tabs 27a are deformed against back wall 18a of housing 18 and fingers 38 of backup member 20 move away from protrusions 52b of center rod 52. Further, inner periphery 20b of backup plate 20 moves past edge 26f of cam latch member 26 such that cam latch member 26 is pivoted in the direction indicated by arrow “X” in FIG. 9 by plunger 54 to a position in which body portion 26d is positioned in front of and engages backup plate 20. Engagement of plunger 54 with cam latch member 26 and subsequently with post 16 urges anvil head assembly 12 to the tilted position. It is noted that anvil head assembly 12 will not immediately tilt upon firing of a stapling device (not shown) because, upon firing, anvil head assembly 12 is in an approximated position, i.e., the anvil head assembly 12 is in close alignment with the shell assembly of the stapling device (not shown). As such, the anvil head assembly 12 will only begin to tilt when the anvil head assembly and the shell assembly of the stapling device (not shown) are being unapproximated.

[0035] Referring to FIG. 10, as anvil head assembly 12 pivots towards its tilted position, finger 66 of plunger 54 maintains surface 26e of cam latch member 26 in contact with backup plate 20 to prevent backup plate 20 from sticking to the knife blade as the knife blade is retracted. It is noted that curved surface 26e of cam latch member is configured to eliminate any gap and ensure contact between surface 26e of cam latch member 26 and backup plate 20 to hold backup plate 20 in place during and after the knife blade is retracted such that the cutting ring and backup plate assembly stay in their correct position during tilting of anvil assembly 12.

[0036] It will be understood that various modifications may be made to the embodiments disclosed herein. For example, the cutting ring and backup plate can be unitarily or integrally formed. Further, the anvil assembly need not have cutting ring cover. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.