document: CROSS-REFERENCE TO RELATED APPLICATIONS 
         [0001]    This application claims the benefit of and priority to U.S. Provisional Patent Application No. 62/352,683 filed Jun. 21, 2016, the entire disclosure of which is incorporated by reference herein. 
       
      
       BACKGROUND 
       1. Technical Description 
         [0002]    The present disclosure is directed to an anvil assembly for use with a surgical stapling device. More particularly, the present disclosure is directed to an anvil assembly for a circular surgical stapling device including a stabilizing collet positioned to prevent damage to the anvil assembly. 
         2. Background of Related Art 
         [0003]    Circular staplers are commonly used to perform a variety of surgical procedures including anastomosis procedures for joining ends of tubular tissue sections and hemorrhoidectomy procedures for treating hemorrhoids. Typically, circular staplers include a stapling device and an anvil assembly. The stapling device includes a handle assembly, a body portion extending from the handle assembly, a shell assembly including a staple cartridge, and a trocar extending from the shell assembly. The anvil assembly is releasably secured to the trocar of the stapling device and includes an anvil assembly having an anvil shaft and an anvil head assembly. The shell assembly includes a circular knife. When the circular stapler is fired, the circular knife is advanced from the shell assembly and cuts tissue as staples are ejected from the staple cartridge and formed against the anvil head assembly. In use, the stapling device and the anvil assembly are delivered to a surgical site within a patient separately and coupled to each other prior to use. 
           [0004]    Typically, the stapling device and the anvil assembly are coupled together at the surgical site by a clinician using a grasper. More particularly, the clinician grasps the anvil shaft of the anvil assembly with the grasper and positions the anvil shaft about the trocar of the stapling device to couple the trocar to the anvil shaft. This coupling procedure takes place within a body lumen or orifice where visibility is limited. 
           [0005]    When a clinician applies too much pressure on the anvil shaft, the anvil shaft can be damaged, e.g., crushed or deformed, such that the anvil shaft cannot be properly coupled to the stapling device. This problem is exacerbated because due to the poor visibility at the surgical site, the clinician may be unaware that the anvil shaft has been damaged and is not properly coupled to the stapling device. As such, when circular stapler is fired, the anvil assembly may become disengaged from the stapling device such that the staples are not formed in cut tissue. 
           [0006]    Accordingly, a need exists in the surgical arts for an anvil assembly that is less susceptible to damage during attachment of the anvil assembly to the stapling device to facilitate reliable attachment of the anvil assembly to a stapling device. 
         SUMMARY 
         [0007]    In one aspect of the disclosure, an anvil assembly includes an anvil shaft defining a first longitudinal bore and an anvil head assembly. The anvil shaft has a proximal portion and a distal portion. The proximal portion includes a plurality of flexible legs that define the first longitudinal bore. The anvil head assembly is secured to the distal portion of the anvil shaft and supports an anvil plate that defines a plurality of staple deforming pockets. A stabilizing collet defines a second longitudinal bore. The collet is supported within the first longitudinal bore and is positioned to prevent damage to the plurality of flexible legs. 
           [0008]    In another aspect of the disclosure, a surgical stapler includes a stapling device and an anvil assembly. The stapling device includes a handle assembly, a body portion that extends distally from the handle assembly, a shell assembly including a staple cartridge having a plurality of staples, and a trocar extending from the shell assembly. The anvil assembly includes an anvil shaft and an anvil head assembly. The anvil shaft has a proximal portion and a distal portion and defines a first longitudinal bore configured to receive the trocar of the stapling device. The proximal portion includes a plurality of flexible legs that defines the first longitudinal bore. The anvil head assembly is secured to the distal portion of the anvil shaft and supports an anvil plate that defines a plurality of staple deforming pockets. A stabilizing collet defines a second longitudinal bore configured to receive the trocar. The collet is supported within the first longitudinal bore and is positioned to prevent damage to the plurality of flexible legs. 
           [0009]    In embodiments, the collet is cylindrical. 
           [0010]    In certain embodiments, the collet is substantially rigid. 
           [0011]    In some embodiments, the collet has a distal end including a plurality of cantilevered fingers, wherein each of the plurality of cantilevered fingers has a protrusion configured to secure the collet within the first longitudinal bore of the anvil shaft. 
           [0012]    In certain embodiments, each of the plurality of flexible legs defines a longitudinal channel with an adjacent one of the plurality of flexible legs. 
           [0013]    In embodiments, the anvil shaft defines a hole positioned adjacent the distal end of each of the longitudinal channels. Each of the holes is configured to receive a respective one of the protrusions. 
           [0014]    In some embodiments, each of the holes is circular. 
           [0015]    In certain embodiments, the anvil head assembly is pivotally secured to the anvil shaft. 
           [0016]    In embodiments, the anvil plate is annular. 
       
      
       
         BRIEF DESCRIPTION OF THE DRAWINGS 
           [0017]    Various embodiments of the presently disclosed crush resistant anvil assembly are described herein below with reference to the drawings, wherein: 
             [0018]      FIG. 1  is a side perspective view of a surgical stapler including an exemplary embodiment of the presently disclosed crush resistant anvil assembly; 
             [0019]      FIG. 2  is an enlarged view of the indicted area of detail shown in  FIG. 1 ; 
             [0020]      FIG. 3  is a cross-sectional view taken along section line  3 - 3  of  FIG. 2 ; 
             [0021]      FIG. 4  is a side perspective view of the anvil assembly shown in  FIG. 2 ; 
             [0022]      FIG. 5  is an enlarged view of the indicated area of detail shown in  FIG. 4 ; 
             [0023]      FIG. 6  is a side perspective view of a collet of the anvil assembly shown in  FIG. 4 ; 
             [0024]      FIG. 7  is a side cross-sectional view of the collet shown in  FIG. 6  and the anvil shaft of the anvil assembly shown in  FIG. 4  with parts separated; 
             [0025]      FIG. 8  is a side cross-sectional view of the collet and anvil shaft shown in  FIG. 7  as the collet is slid into the anvil shaft; 
             [0026]      FIG. 9  is a side cross-sectional view of the collet and anvil shaft shown in  FIG. 8  with the collet secured within the anvil shaft; and 
             [0027]      FIG. 10  is a side cross-sectional view of the collet and anvil shaft shown in  FIG. 9  as a trocar of the stapling device is positioned within the anvil shaft. 
         
      
      
       DETAILED DESCRIPTION OF EMBODIMENTS 
         [0028]    Exemplary embodiments of the presently disclosed damage resistant anvil assembly 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. In this description, the term “proximal” is used generally to refer to that portion of the stapler that is closer to a clinician, while the term “distal” is used generally to refer to that portion of the stapler that is farther from the clinician. In addition, the term “endoscopic” is used generally to refer to procedures performed through a small incision or a cannula inserted into a patient&#39;s body including endoscopic, laparoscopic, and arthroscopic procedures. Finally, the term clinician is used generally to refer to medical personnel including doctors, nurses, and support personnel. 
           [0029]    The presently disclosed anvil assembly includes an anvil head assembly, an anvil shaft, and a stabilizing collet. In embodiments, the stabilizing collet may be formed of a substantially rigid material. Alternately, other materials of construction that provide support to the anvil shaft are envisioned. The anvil shaft includes a plurality of flexible legs that flex outwardly in response to insertion of a trocar of a surgical stapling device into the anvil shaft to releasably couple the anvil shaft to the trocar. The collet is received within a longitudinal bore defined by the flexible legs of the anvil shaft at a location to support the flexible legs and minimize the likelihood of damage to the anvil shaft caused by engagement of the anvil shaft with a grasper. The collet is also positioned in a location not to interfere with flexing of the legs during coupling of the anvil shaft to the trocar of the stapling device. 
           [0030]      FIG. 1  illustrates a manually powered surgical stapler  10  including a stapling device  12  supporting an exemplary embodiment of anvil assembly  100 . The stapling device  12  includes a handle assembly  14 , a body portion  16  that extends distally from the handle portion  14 , and a shell assembly  18  that supports a staple cartridge  20 . The staple cartridge  20  supports a plurality of staples (not shown) that are arranged in an annular configuration within the shell assembly  18 . The stapling device  12  also includes a trocar  22  that extends from the distal end of the body portion  16  through the shell assembly  18 . The trocar  22  is configured to releasably engage the anvil assembly  100  as described in further detail below. For a more detailed description of a suitable stapling device, see U.S. Pat. Nos. 7,234,624, 7,364,060 and 7,857,187 (“the incorporated patents”) which are incorporated herein by reference in their entirety. 
           [0031]    Referring also to  FIGS. 2-4 , the anvil assembly  100  includes an anvil head assembly  102  and an anvil shaft  104 . Although not specifically described in this application, the anvil head assembly  102  can be pivotally or fixedly attached to the anvil shaft  104 . Examples of pivotally attached anvil head assemblies are described in the incorporated patents. 
           [0032]    The anvil head assembly  102  includes a housing  106  that supports an anvil plate  108  ( FIG. 2 ) and a cut ring assembly  110 . The housing  106  has a smoothly curved distal surface  112  that facilitates atraumatic entry of the anvil assembly  100  into and through a body orifice or lumen. A proximal side of the housing  106  defines a cavity (not shown) that is configured to receive the anvil plate  108  and the cut ring assembly  110 . For a more detailed description of the components of the anvil head assembly  102 , see the incorporated patents. 
           [0033]    The anvil shaft  104  includes a longitudinal body portion  116  that includes a tubular portion  118  and a plurality of flexible legs  120  that extend proximally from the tubular portion  118 . Each of the flexible legs  120  has a semi-cylindrical configuration such that the legs  120  cooperate to define a longitudinal bore  122  ( FIG. 3 ) that is dimensioned to receive the trocar  22  of the stapling device  12  ( FIG. 1 ) when the anvil assembly  100  is secured to the stapling device  12 . The bore  122  extends from the proximal end of the flexible legs  120  at least partially into the tubular portion  118  of the anvil shaft  104 . 
           [0034]    In embodiments, the anvil shaft  104  may include a plurality of splines  126  positioned about the anvil shaft  104 . As is known in the art, the splines  126  mate with recesses (not shown) defined within the shell assembly  16   FIG. 2 ) of the surgical stapling device  12  to properly orient the staple cartridge  20  in relation to the anvil plate  108  of the anvil assembly  100  when the anvil assembly  100  and the shell assembly  18  are approximated. The anvil shaft  104  may also include one or more stabilization rings  130  (only one is shown) positioned about the anvil shaft  104  at a position to engage the shell assembly  16  when the anvil assembly  100  and the shell assembly  18  are approximated to provide added stability to the anvil assembly  100 . For a more detailed description of an anvil assembly including a stabilization ring, see U.S. Pat. No. 8,424,535 which is incorporated herein by reference in its entirety. Although the splines  126  and the stabilization ring  130  are shown to be formed integrally with the anvil shaft  104 , it is contemplated the either or both could be formed separately from the anvil shaft  104  and secured to the anvil shaft  104  using any known fastening technique including welding, crimping gluing or the like. 
           [0035]    Referring to  FIGS. 4 and 5 , each of the flexible legs  120  of the anvil shaft  104  defines a longitudinal channel  134  with an adjacent leg  120 . Each longitudinal channel  134  includes an enlarged cutout or hole  136  formed at the distal end of the longitudinal channel  134 . The holes  136  are configured to secure a collet  150  within the longitudinal bore  122  of the anvil shaft  104 . In embodiments, the hole  136  is substantially circular although other configurations are envisioned. One or more of the flexible legs  120  may also include a bore  140  which is configured to receive a suture or the like (not shown). The suture can be used to allow a clinician to retrieve or position the anvil assembly  100  from or within a surgical site. The proximal end of each of the flexible legs  120  has an inner surface that defines a recess  160  ( FIG. 7 ) such that the recesses  160  collectively define an annular recess  160   a  ( FIG. 9 ). The annular recess  160   a  facilitates releasable engagement of the anvil assembly  100  to the stapling device  12 . 
           [0036]    Referring also to  FIG. 6 , the collet  150  may be substantially rigid and is positioned within the longitudinal bore  122  defined by the anvil shaft  104 . The collet  150  is substantially cylindrical and defines a longitudinal bore  152  ( FIG. 7 ) that is dimensioned to receive the trocar  22  ( FIG. 10 ). A distal portion  154  of the collet  150  includes a plurality of cantilevered fingers  156 . Each of the fingers  156  includes a protrusion  158  that is dimensioned and configured to be received in a respective one of the holes  136  ( FIG. 5 ) formed in the anvil shaft  104  as described in further detail below. 
           [0037]    Referring to  FIGS. 7-9 , in order to assemble the collet  150  within the anvil shaft  104 , the distal end of the collet  150  is inserted into the proximal end of the longitudinal bore  122  of the anvil shaft  104  and slid distally in the direction indicated by arrow “A” in  FIGS. 7 and 8 . The collet  150  is positioned to align the protrusions  158  with the longitudinal channels  134  positioned between the flexible legs  120 . When the protrusions  158  engage an inner wall of the flexible legs  120 , the fingers  156  are deflected inwardly in the direction indicated by arrow “B” in  FIG. 8  to facilitate passage of the collet  150  through the longitudinal bore  122 . When the protrusions  158  are moved into alignment with the holes  136 , the fingers  156  spring outwardly in the direction indicated by arrow “C” in  FIG. 9  to move the protrusions  158  into the holes  136  to secure the collet  150  within the longitudinal bore  122 . 
           [0038]    Referring to  FIG. 10 , the trocar  22  includes a pointed distal end  30  and an enlarged proximal portion  32  that defines a shoulder  32   a . As known in the art, the proximal end of the trocar  22  is secured to an approximation mechanism (not shown) of the stapling device  12  ( FIG. 1 ) to facilitate movement of the trocar  22  between retracted and advanced positions. When the trocar  22  is inserted into the longitudinal bore  122  of the anvil shaft  104  and the longitudinal bore  152  of the collet  150  in the direction indicated by arrow “D” in  FIG. 10 , the enlarged proximal portion  32  of the trocar  22  engages a proximal end of the flexible legs  120  of the anvil shaft  104  to urge the flexible legs  120  outwardly in the direction indicated by arrows “E”. When the enlarged proximal portion  32  of the trocar  22  is moved distally in the direction indicated by arrow “D” into alignment with the recess  160  defined at the proximal end of the flexible legs  120 , the flexible legs  120  return to their undeformed configuration to receive the enlarged proximal portion  32  of the trocar  22 . When the enlarged proximal portion  32  is received within the recess  160 , the shoulder  32   a  on the enlarged proximal portion  32  of the trocar  32  engages a proximal wall  161  defining the recess  160  to secure the anvil shaft  104  to the trocar  22 . 
           [0039]    During an endoscopic surgical procedure, the anvil assembly  100  is grasped with a grasper (not shown) that is inserted through a small incision in the skin to position the trocar  22  within the longitudinal bore  122  of the anvil shaft  104  and secure the anvil assembly  100  to the trocar  22  of the surgical stapling device  12 . The collet  150  is positioned within the longitudinal bore  122  of the anvil shaft  104  and extends from a distal end of the flexible legs  120  towards the proximal end of the flexible legs  120  to support the flexible legs  120  and inhibit radial compression or other deformation of the flexible legs  120  that may result from pressure applied to the flexible legs  120  by a manipulating instrument (not shown). Collet  150  may be formed from any suitable, medical grade material having a stiffness to perform the functions described herein. Suitable materials include, for example, stainless steel or nylon. The collet  150  is secured within the longitudinal bore  122  of the anvil shaft  104  in a position that does not interfere with outward flexing of the flexible legs  120  and, thus, allows the anvil assembly  100  to be readily connected to the trocar  22 . 
           [0040]    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 embodiments. It is envisioned that the elements and features illustrated or described in connection with one exemplary embodiment may be combined with the elements and features of another without departing from the scope of the present disclosure. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the above-described embodiments. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims.
summary: An anvil assembly is disclosed that includes an anvil shaft including a proximal portion and a distal portion and defining a first longitudinal bore. The proximal portion includes a plurality of flexible legs that define the first longitudinal bore dimensioned to receive a trocar of a stapling device. An anvil head assembly is secured to the distal portion of the anvil shaft and supports an annular anvil plate that a plurality of staple deforming pockets. The anvil assembly also includes a rigid collet defining a second longitudinal bore that is configured to receive the trocar of the stapling device. The rigid collet is supported within the first longitudinal bore and is positioned to prevent crushing of the plurality of flexible legs when the anvil assembly is manipulated with a grasper.