Abstract:
A loading unit assembly includes a tool assembly having first and second jaw members and a pivot pin configured to pivotably couple the first and second jaw members. The first jaw member is movable with respect to the second jaw member between spaced and approximated positions, wherein the pivot pin includes a base portion and first and second stepped portions extending radially outward from the base portion. The first and second stepped portions are configured to pivotably engage the first and second jaw members, respectively.

Description:
BACKGROUND 
       [0001]    1. Technical field 
         [0002]    The present disclosure relates generally to instruments for surgically joining tissue and, more specifically, to a pivot pin pivotably joining a pair of jaw members of a surgical instrument. 
         [0003]    2. Background of Related Art 
         [0004]    Various types of surgical instruments used to surgically join tissue are known in the art, and are commonly used, for example, for closure of tissue or organs in transection, resection, and anastomoses; and for occlusion of organs in thoracic and abdominal procedures. 
         [0005]    One example of such a surgical instrument is a surgical stapling instrument, which typically includes an anvil assembly, a cartridge assembly for supporting an array of surgical staples, an approximation mechanism for approximating the cartridge and anvil assemblies, and a firing mechanism for ejecting the surgical staples from the cartridge assembly. 
         [0006]    To achieve proper results, e.g., consistent staple formation, proper anvil to cartridge alignment is needed. Accordingly, a need exists for an approximation mechanism that properly aligns the cartridge and anvil assemblies for proper staple formation. 
       SUMMARY 
       [0007]    In accordance with an embodiment of the present disclosure, there is provided a loading unit assembly adapted to releasably engage a surgical instrument. The loading unit assembly includes a tool assembly including first and second jaw members and a pivot pin configured to pivotably couple the first and second jaw members. The first jaw member is movable with respect to the second jaw member between spaced and approximated positions, wherein the pivot pin includes a base portion and first and second stepped portions extending radially outward from the base portion. The first and second stepped portions are configured to pivotably engage the first and second jaw members, respectively. 
         [0008]    In an embodiment, the pair of stepped portions may be concentrically arranged. In addition, the pair of stepped portions may have different diameters. A diameter of the first stepped portion may be smaller than a diameter of the second stepped portion. 
         [0009]    In another embodiment, at least a portion of the base portion may include threads. In still another embodiment, the first jaw member may include a cartridge assembly having a plurality of staples, and the second jaw member may include an anvil assembly. The loading unit assembly may further include an elongate member including a mounting portion defining a bore configured and dimensioned to receive the pivot pin therein. The first jaw member may include a pair of walls each defining a hole. At least a portion of the mounting portion may be disposed between the pair of walls of the first jaw member such that the bore and the holes are aligned to receive the pivot pin. Moreover, the second jaw member may include a pair of walls each defining a hole. In particular, at least a portion of the pair of walls of the first jaw member may be received between the pair of walls of the second jaw member such that the holes of the first and second jaw members and the bore are aligned to receive the pivot pin. 
         [0010]    In still yet another embodiment, the body portion of the pivot pin may be threadably received into the bore of the mounting portion. The second stepped portion may include a recess configured to receive a tool for tightening of the pivot pin. The first and second jaw members may be curved with respect to a longitudinal axis defined by the elongate member. 
     
    
     
       BRIEF DESCRIPTION OF FIGURES 
         [0011]    Various embodiments of the presently disclosed surgical instrument are disclosed herein with reference to the drawings, wherein: 
           [0012]      FIG. 1  is a perspective view of a surgical stapling instrument including a loading unit in accordance with an embodiment of the present disclosure; 
           [0013]      FIG. 2  is a perspective view of the surgical stapling instrument of  FIG. 1  with the loading unit removed therefrom; 
           [0014]      FIG. 3  is a perspective view of the loading unit of  FIG. 1 ; 
           [0015]      FIG. 4  is a perspective view of the area of detail indicated in  FIG. 1 ; 
           [0016]      FIG. 5  is a transverse cross-sectional view of the loading unit of  FIG. 3 ; 
           [0017]      FIG. 6  is a longitudinal cross-sectional view of a portion of the loading unit of  FIG. 3 ; 
           [0018]      FIG. 7  is an exploded perspective view of the loading unit of  FIG. 3  with parts separated; 
           [0019]      FIG. 8  is a side view of a pivot screw for use with the loading unit of  FIG. 1 ; 
           [0020]      FIG. 9  is a end view of a the pivot screw of  FIG. 8 ; 
           [0021]      FIG. 10  is a partial, cross-sectional view of the loading unit of  FIG. 3  illustrating alignment of bores configured to receive the pivot screw of  FIG. 8 ; and 
           [0022]      FIGS. 11-13  are perspective views of the loading unit of  FIG. 3  interacting with a layer of tissue at various stages of operation of the loading unit. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Embodiments of the presently disclosed surgical instrument, and loading unit for use therewith, are described in detail with reference to the drawings, wherein like reference numerals designate corresponding elements in each of the several views. As is common in the art, the term “proximal” refers to that part or component closer to the user or operator, e.g., surgeon or physician, while the term “distal” refers to that part or component farther away from the user. 
         [0024]    With reference to  FIGS. 1-4 , a surgical stapling instrument of the present disclosure is indicated as reference numeral  10 . Surgical stapling instrument  10  includes a handle assembly  12  including an actuation trigger  22 , an endoscopic portion  18  extending distally from handle assembly  12 , and a loading unit (or “DLU”)  500  removably attached to endoscopic portion  18 . Further details of an endoscopic surgical stapling instrument are described in a commonly-owned U.S. Pat. No. 6,953,139 to Milliman et al., the entire contents of which are hereby incorporated by reference herein. 
         [0025]    With particular reference to  FIGS. 3 and 4 , DLU  500  includes a proximal body portion  502  and a tool assembly  504 . Proximal body portion  502  defines a longitudinal axis “A-A,” and is releasably attachable to a distal end of endoscopic portion  18  of surgical instrument  10 . Tool assembly  504  includes a pair of jaw members including an anvil assembly  506  and a cartridge assembly  508 . At least one jaw member is pivotable in relation to the other about a pivot  555 . In particular, cartridge assembly  508  is pivotable in relation to anvil assembly  506  and is movable between an open or unclamped position and a closed or approximated position. Cartridge assembly  508  is urged in the open position via a biasing member  533 , e.g., a pair of compression springs, disposed between anvil cover  510  and cartridge  518  ( FIG. 7 ). 
         [0026]    With reference now to  FIG. 4 , anvil assembly  506  and cartridge assembly  508  are curved with respect to the longitudinal axis “A-A” defined by proximal body portion  502 . The curved jaw members, as compared to straight jaw members, may help facilitate access to lower pelvis regions, e.g., during lower anterior resection (“LAR”). Additionally, the inclusion of curved jaw members may allow increased visualization to a surgical site and may also allow more room for a surgeon to manipulate target tissue or the jaw members themselves with his or her hand. 
         [0027]    The term “distal” typically refers to that part or component of the instrument that is farther away from the user. As used herein, the terms “distal” and “proximal” will take into account the curvature of curved parts of the surgical instrument  10  of the present disclosure. For example, “distal” will refer to the portion of the curved part that is farthest from the user, along a trajectory defined by the curved part, such as trajectory C-C shown in  FIG. 4 . That is, while an intermediate portion of a curved part may be farther from the user during use, the portion of the curved part that is farthest along its longitudinal axis is considered “distal.” Anvil assembly  506  has a proximal end  506   a  and a distal end  506   b  and cartridge assembly  508  has a proximal end  508   a  and a distal end  508   b.    
         [0028]    With reference to  FIGS. 5-7 , anvil assembly  506  includes an anvil cover  510  and an anvil plate  512  which includes a plurality of staple forming depressions  514  ( FIG. 6 ). Anvil plate  512  is secured to an underside of anvil cover  510  to define a channel  511  ( FIG. 5 ) between plate  512  and cover  510 . When tool assembly  504  is in the approximated position, staple forming depressions  514  are positioned in juxtaposed alignment with cartridge assembly  508 . 
         [0029]    Cartridge assembly  508  includes a curved carrier  516 , which receives a curved cartridge  518  via a snap-fit connection. Cartridge  518  includes a pair of support struts  524  which rest on sidewalls  517  of carrier  516  to stabilize cartridge  518  on carrier  516 . Support struts  524  also set the height or location of cartridge  518  with respect to anvil plate  512 . An external surface of carrier  516  includes an angled cam surface  516   a.    
         [0030]    With continued reference to  FIGS. 5-7 , staple cartridge  518  includes a central slot  526  that is curved with respect to the longitudinal axis A-A and three curved rows of staple retention slots  528  positioned on each side of curved longitudinal slot  526 . Each slot  528  is configured to receive a staple  530  therein. Cartridge  518  also defines a plurality of cam wedge slots  529  ( FIG. 6 ) which accommodate staple pushers  532  and which are open on the bottom (i.e., away from tissue contacting surface  540 ) to allow a longitudinally curved actuation sled  536  to pass therethrough. Actuation sled  536  passes through cam wedge slots  529  and forces staple pushers  532  towards respective staples  530 . Staples  530  are then urged from their respective staple retention slots  528 . 
         [0031]    With reference to  FIG. 7 , proximal body portion  502  of DLU  500  includes an inner body  503  formed from molded half-sections  503   a  and  503   b  and a drive assembly  560 . Proximal body portion  502  is coupled to tool assembly  504  by a mounting assembly  570 . Mounting assembly  570  has a pair of extensions  576 . Each extension  576  has a transverse bore  578 . The pair of extensions  576  at least partially extends into a proximal end of carrier  516 . In particular, a portion of the pair of extensions  576  is disposed between a pair of proximal side walls  591  of carrier  516 . The pair of proximal side walls  591  is disposed within a pair of proximal side walls  515  of anvil cover  510 , whereby holes  580  defined in proximal side walls  591  of carrier  516  and holes  577  defined in proximal sidewalls  515  of anvil cover  510  are aligned with bores  578  of mounting assembly  570  ( FIG. 10 ). Holes  577 ,  580  and bores  578  are configured and dimensioned to receive screw  900  to pivotally secure cartridge assembly  508  with mounting assembly  570 , which, in turn, enables pivoting of cartridge assembly  508  with respect to anvil assembly  506 . 
         [0032]    With reference now to  FIGS. 7-10 , each screw  900  includes first and second stepped portions  902 ,  904  and a base portion  906  having threads  906   a.  In particular, first stepped portion  902  is configured and dimensioned to be received in hole  580  defined in carrier  516 . First stepped portion  902  provides an alignment and a bearing surface for carrier  516  to pivotally engage therewith. First stepped portion  902  includes first diameter D1 and a first length L1. First length L1 of first stepped portion  902  is tailored to define a controlled gap L4 ( FIG. 10 ) between proximal side wall  591  of anvil cover  510  and mounting assembly  570 . Moreover, first stepped portion  902  includes a transition portion  902   a  having a concave profile to reduce stress concentration therealong. 
         [0033]    Second stepped portion  904  is configured and dimensioned to be received in hole  577  defined in anvil cover  510 . Second stepped portion  904  includes a second diameter D2 and a second length L2. First stepped portion  902  is concentrically arranged with second stepped portion  904  and base portion  906 . Second diameter D2 is configured and dimensioned to align depressions  514  in anvil plate  512  with retention slots  528  of cartridge  518 . Moreover, second length L2 of second stepped portion  904  is toleranced to allow the static anvil assembly  506  to float while being securely coupled with cartridge assembly  508 . At least a portion of base portion  906  of screw  900  includes threads  906   a  configured to threadably engage bores  578  defined in mounting assembly  570 . Screw  900  includes a lateral surface  915  defining a recess  905  configured to receive a tool (not shown) to tighten screw  900  into bore  578  of mounting assembly  570 . 
         [0034]    In contrast to conventional pivot assemblies, screw  900  allows for a higher torque setting and better screw security with a controlled channel width. As a result, more consistent staple formation, as well as improved anvil to cartridge alignment is achieved. 
         [0035]    With reference back to  FIG. 7 , mounting assembly  570  is fixedly secured to half-section  503   a  by a pair of vertical protrusions  584 . Vertical protrusions  584  extend upwardly from mounting assembly  570  and frictionally fit into corresponding recesses (not shown) in half-section  503   a.    
         [0036]    With reference to  FIG. 7 , when drive assembly  560  is advanced distally within tool assembly  504 , an upper beam portion  606   b  of clamping member  606  moves within channel  511  ( FIG. 5 ) defined between anvil plate  512  and anvil cover  510 , and lower beam portion  606   c  moves over an exterior surface of carrier  516 . When lower beam  606   c  engages and moves over cam surface  516   a,  cartridge assembly  508  pivots from the open position to the closed position. 
         [0037]    In use, tissue is placed between the jaw members ( FIGS. 11 and 12 ) and the jaws are approximated ( FIG. 13 ) with respect to each other. Actuation of trigger  22  through successive strokes causes distal advancement of drive bar  30  ( FIG. 2 ), such that drive bar  30  pushes a drive assembly  560  ( FIG. 7 ) through cartridge  518 . Further details of distal advancement of drive bar  30  through actuation of trigger  22  are explained in U.S. Pat. No. 6,953,139 to Milliman et al., which has been incorporated by reference hereinabove. 
         [0038]    The movement of drive assembly  560 , and in particular, a clamping member  606  affixed thereto, moves a longitudinally curved actuation sled  536  through cartridge  518 . As sled  536  moves through cartridge  518 , longitudinally curved cam wedges  534  ( FIG. 7 ) of actuation sled  536  sequentially engage pushers  532  to move pushers  532  vertically within staple retention slots  528  and eject staples  530  into staple forming depressions  514  of anvil plate  512 . Subsequent to the ejection of staples  530  from retention slots  528  (and into tissue), a cutting edge  606   d  of clamping member  606  severs the stapled tissue as cutting edge  606   d  travels through curved slot  526  of cartridge  518 . 
         [0039]    While the above description contains many specifics, these specifics should not be construed as limitations on the scope of the present disclosure, but merely as illustrations of various embodiments thereof. For example, while tissue stop  700  ( FIGS. 7 and 11 ) is shown to be disposed at a distal portion of DLU  500 , it is also envisioned that screw  900  may be used with a DLU having a tissue stop at a proximal portion thereof. Under such a configuration, stepped portions extend past the tissue stop, such that the stepped portions serve as a bearing surface for the tissue stop. Therefore, the above description should not be construed as limiting, but merely as exemplifications of various embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.