Patent Publication Number: US-11033264-B2

Title: Surgical fastener applying apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage Application of PCT/US13/68247 under 35USC § 371 (a), the disclosure of the above-identified application is hereby incorporated by reference its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a surgical fastener applying apparatus and, more particularly, to a surgical fastener applying apparatus having reusable and disposable components. 
     2. Discussion of Related Art 
     Surgical fastener applying apparatus wherein tissue is first grasped or clamped between opposing jaw structures and then joined with surgical fasteners, are well known in the art. In some such apparatus, a knife is provided to cut the tissue which has been joined by the fasteners. The fasteners are typically in the form of surgical staples, although, other surgical fasteners may also be utilized, such as, for example, clips or two part polymeric surgical fasteners. 
     Surgical fastener applying apparatus typically include two elongated beam members which are used to capture or clamp tissue therebetween. Typically, one of the beam members carries a disposable cartridge assembly which houses a plurality of staples arranged in at least two lateral rows, while the other beam member includes an anvil which defines a surface for forming the staple legs as the staples are driven from the cartridge assembly. Where two part fasteners are used, the beam member which includes the anvil carries a mating part of the two part fastener, e.g. the receiver. 
     Generally, the staple formation process is affected by the interaction between one or more longitudinally moving camming members and a series of individual staple pushers. As the camming members travel longitudinally through the cartridge carrying beam member, the individual pusher members are biased upwardly into a backspan of the staples supported within the cartridge assembly to sequentially eject the staples from the cartridge. A knife may be provided to travel with the camming members between the staple rows to cut the tissue between the rows of formed staples. An example of such an instrument is disclosed in U.S. Pat. No. 7,631,794, which is incorporated herein in its entirety by reference. 
     SUMMARY 
     The present invention relates to a surgical fastener applying apparatus for applying surgical fasteners to tissue. In embodiments, the surgical fastener applying apparatus includes an anvil half-section including a distal anvil portion and a proximal handle portion, and a cartridge receiving half-section defining an elongated channel member. The elongated channel member has a distal portion dimensioned to releasably receive a single use loading unit and a proximal portion configured to support a firing assembly. The firing assembly includes a stationary housing and a firing lever having at least one lever guide projection extending from the firing lever. The firing lever is slidable from a proximal end of the stationary housing to a distal end of the stationary housing to define a firing stroke. A clamping lever is secured to the cartridge receiving half-section and includes a proximal handle portion. The clamping lever is operably associated with the anvil half-section and the cartridge receiving half-section and is movable from an unclamped position to a clamped position to releasably secure the distal anvil portion of the anvil half-section in close approximation with the single use loading unit. The proximal handle portion of the clamping lever defines at least one lever guide slot. The at least one lever guide projection is positioned to enter the at least one lever guide slot upon initiation of the firing stroke to inhibit movement of the clamping lever to the unclamped position during the firing stroke. 
     In embodiments, the clamping lever is releasably secured to the cartridge receiving half-section. 
     In embodiments, at least one of the proximal handle portion of the anvil half-section and the proximal handle portion of the clamping lever defines a plurality of apertures to facilitate cleaning and sterilization of the anvil half-section and/or the clamping lever. 
     In embodiments, the distal anvil portion of the anvil half-section defines a longitudinal slot extending therethrough. The longitudinal slot defines a relatively narrow bottom portion and a top portion that increasingly widens in a direction extending away from the bottom portion. 
     In embodiments, the firing assembly includes a stationary housing having a bottom surface and a protrusion extending downwardly from the bottom surface. The proximal portion of the elongated channel member of the cartridge receiving half-section defines an aperture configured to receive the protrusion of the stationary housing to releasably secure and align the firing assembly within the elongated channel member. 
     In embodiments, the firing assembly is configured to be releasably secured within the cartridge receiving half-section prior to releasably securing the single use loading unit within the elongated channel member. 
     In embodiments, a biasing member is supported in a distal end of the firing assembly. The biasing member is configured to inhibit full seating of the single use loading within the elongated channel member prior to movement of the clamping lever to the clamped position. 
     In embodiments, the anvil half-section includes a proximally located bar and the cartridge receiving half-section includes a pair of proximally located support members that each define a vertical slot. The bar is configured to be received within the vertical slots to pivotably support the anvil half-section in relation to the cartridge receiving half-section. 
     In embodiments, the clamping lever includes a pair of inwardly-extending projections and the cartridge receiving half-section defines a pair of dimples. The projections of the clamping lever are configured to be received within the dimples of the cartridge receiving half-section to releasably retain the clamping lever in an intermediate position between the clamped position and the unclamped position. 
     In embodiments, the at least one lever guide slot has a mouth. The at least one lever guide projection is positioned to enter the mouth of the at least one lever guide slot upon movement of the clamping lever to the clamped position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the presently disclosed surgical fastener applying apparatus will now be described herein with reference to the accompanying figures wherein: 
         FIG. 1  is a side perspective view of an embodiment of the presently disclosed surgical fastener applying apparatus in the clamped position; 
         FIG. 2  is a side perspective view of the surgical fastener applying apparatus of  FIG. 1  during assembly of the clamping lever and the cartridge receiving half-section; 
         FIG. 3  is a side perspective view of the surgical fastener applying apparatus of  FIG. 1  shown with parts separated; 
         FIG. 4A  is a side perspective view of the anvil half-section of the surgical fastener applying apparatus of  FIG. 1 ; 
         FIG. 4B  is a bottom perspective view of the anvil half-section of  FIG. 4A ; 
         FIG. 5  is a bottom, perspective view of the proximal end portion of the anvil half-section of  FIG. 4A ; 
         FIG. 6A  is a side view of the proximal end of the anvil half-section and cartridge-receiving half-section of the surgical fastener applying apparatus of  FIG. 1  shown disengaged from one another; 
         FIG. 6B  is a side view of the proximal end of the anvil half-section and cartridge-receiving half-section of  FIG. 6A  shown engaged to one another; 
         FIG. 7A  is a bottom perspective view of the cartridge-receiving half-section of the surgical fastener applying apparatus of  FIG. 1 ; 
         FIG. 7B  is a side view of the cartridge-receiving half-section of  FIG. 7A ; 
         FIG. 8  is an enlarged side perspective view of the area of detail indicated in  FIG. 7A ; 
         FIG. 9  is a side perspective view of the firing assembly of the surgical fastener applying apparatus of  FIG. 1 ; 
         FIG. 10  is bottom perspective view of the proximal end of the stationary housing of the firing assembly of  FIG. 9 ; 
         FIG. 11A  is a longitudinal cross-sectional view of the cartridge receiving half-section of the surgical fastener applying apparatus of  FIG. 1  with the single use loading unit (“SULU”) partially engaged therein; 
         FIG. 11B  is a longitudinal cross-sectional view of the cartridge receiving half-section of  FIG. 11A  with the SULU fully engaged therein; 
         FIG. 12A  is a bottom perspective view of the distal portion of the anvil half-section of the surgical fastener applying apparatus of  FIG. 1 ; 
         FIG. 12B  is a top perspective view of the distal portion of the anvil half-section of  FIG. 12A ; 
         FIG. 13  is a transverse cross-sectional view taken across section line  13 - 13  of  FIG. 12B ; 
         FIG. 14A  is a top perspective view of the clamping lever of the surgical fastener applying apparatus of  FIG. 1 ; and 
         FIG. 14B  is a side view of the clamping lever of  FIG. 14A . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Embodiments of the presently disclosed surgical fastener applying apparatus will now be described in detail with reference to the drawings wherein like reference numerals identify similar or identical structural elements in each of the several views. As used herein, as is traditional, the term “proximal” refers to the end of the apparatus which is closer to the user, while the term distal refers to the end of the apparatus which is further away from the user. 
       FIGS. 1-2  illustrate an embodiment of the presently disclosed surgical fastener applying apparatus shown generally as surgical stapler  10 . Surgical stapler  10  includes an anvil half-section  100 , a cartridge receiving half-section  200 , a clamping lever  300 , a single use loading unit  400  (hereinafter “SULU”), and a firing assembly  500 . Anvil half-section  100 , cartridge receiving half-section  200 , and clamping lever  300  may be configured as reusable components and, as such, may be constructed from biocompatible materials suitable for sterilization and repeated use, e.g., stainless steel. As will be described below, anvil half-section  100 , cartridge receiving half-section  200  and clamping lever  300  each include features to facilitate effective sterilization thereof. SULU  400  and firing assembly  500 , on the other hand, are disposable components and are separable from the reusable components of surgical stapler  10 . SULU  400  and firing assembly  500  may be constructed from any suitable biocompatible material including plastics, metals, or combinations thereof. Further, surgical stapler  10  may be configured to receive or accommodate SULUs and/or firing assemblies for firing staples of different staple line lengths, e.g., 60 mm, 80 mm, and 100 mm. 
     Referring to  FIGS. 4A-4B and 12A-13 , anvil half-section  100  includes a proximal handle portion  102  and a distal anvil portion  104 . Distal anvil portion  104  includes a staple deforming portion  106  ( FIG. 4B ) which includes a plurality of staple deforming recesses  108  ( FIG. 12B ) defined within bottom surface  110  thereof. Staple deforming portion  106  can be formed integrally with anvil half-section  100 , or in the alternative, secured to anvil half-section  100  by a fastening process such as welding, tacking, or crimping, or other adhesive. Bottom surface  110  of distal anvil portion  104 , which defines staple deforming portion  106 , is configured to face a top surface of SULU  400  ( FIG. 3 ) when SULU  400  ( FIG. 3 ) is positioned in channel member  202  of cartridge receiving half-section  200  (see  FIG. 2 ). Distal anvil portion  104  defines a central longitudinal slot  112  ( FIGS. 12A-13 ) which extends along a substantial portion of the length of anvil portion  104 . As best shown in  FIGS. 12A-13 , central longitudinal slot  112  has a relatively-narrow bottom portion  114  that extends through bottom surface  110  of staple deforming portion  106  for slidably receiving knife  406  of SULU  400  (see  FIG. 3 ) as knife  406  is moved through SULU  400  (see  FIG. 3 ) to cut tissue between the lateral rows  115  of staples ( FIG. 12B ). As shown in  FIG. 13 , top portion  116  of central longitudinal slot  112  gradually widens from bottom portion  114  to top surface  118  of distal anvil portion  104 , wherein central longitudinal slot  112  defines a relatively wide opening. By providing a central longitudinal slot  112  that widens as shown, less material is required to form the distal anvil portion  104 , thereby reducing the weight of the distal anvil portion  104 . In addition, the widened slot  112  allows for more effective cleaning and sterilization of the distal anvil portion  104 . 
     With reference to  FIGS. 1-5 , and to  FIGS. 4A-4B  in particular, a central portion  120  of anvil half-section  100  is defined between the proximal end of staple deforming portion  106  of distal anvil portion  104  and the distal end of proximal handle portion  102  of anvil half-section  100 . Central portion  120  of anvil half-section  100  includes two pairs of cylindrical lateral support members  124 ,  126 . Central portion  120  of anvil half-section further includes at least one protrusion such as a pair of support fingers  125  extending downwardly towards cartridge receiving half-section  200 . During assembly of anvil half-section  100  and cartridge receiving half-section  200 , lateral support members  124  function to set the minimum gap between SULU  400  ( FIG. 3 ) and staple deforming portion  106  of anvil half-section  100  when surgical stapler  10  ( FIG. 1 ) is in the clamped position. Lateral support members  126 , on the other hand, are supported in U-shaped recesses  212  defined in central portion  210  of cartridge receiving half-section  200  (see  FIGS. 7A-7B ) to properly align SULU  400  ( FIG. 3 ) relative to staple deforming portion  106  of anvil half-section  100  when surgical stapler  10  ( FIG. 1 ) is in the clamped position. Further, in the clamped position, lateral support members  126  are received in cutouts  310  formed on spaced flange portions  308  of clamping lever  300 . As stapler  10  is moved to the clamped position, support fingers  125  urge SULU  400  ( FIG. 3 ) fully into position within channel member  202  of cartridge receiving half-section  200 . 
     With continued reference to  FIGS. 4A-4B  in particular, proximal handle portion  102  of anvil half-section  100  is ergonomically formed and includes a body portion  128  and a thumb-engaging abutment  130 . Body portion  128  may define a plurality of apertures  132  that facilitate the cleaning and sterilization of proximal handle portion  102 . The provision of apertures  132  in body portion  128  also reduces the overall weight of surgical stapler  10 . 
     With additional reference to  FIG. 5 , a proximal end of proximal handle portion  102  includes a downwardly extending protrusion, finger  134  which defines a rear locator bar  136  which will be discussed in further detail below ( FIGS. 6A-6B ). Rear locator bar  136  may assume a variety of configurations, e.g., cylindrical, tear-drop shaped, etc. Rear locator bar  136  may include at least one projection extending laterally therefrom. As best shown in  FIG. 5 , bar  136  may be integrated with, e.g., monolithically formed with, proximal handle portion  102  of anvil half-section  100  towards the proximal end thereof. 
     Referring to  FIGS. 7A-8 , cartridge receiving half-section  200  defines an elongated channel member  202  which defines a substantially U-shaped channel  204  having a distal portion  206  dimensioned to releasably receive SULU  400  ( FIG. 3 ) and a proximal portion  208  dimensioned to releasably receive firing assembly  500  ( FIG. 9 ). Cartridge receiving half-section  200  further includes a central portion  210  defining spaced U-shaped recesses  212  which are positioned to support lateral support members  126  of anvil half-section  100  (see  FIGS. 1-3 ), as mentioned above. Central portion  210  of cartridge receiving half-section  200  further includes a pair of downwardly extending fingers  214  positioned beneath recesses  212 . Fingers  214  each support a cylindrical pivot member  216  which is configured to be received within a respective C-shaped recesses  314  of a spaced flange portion  308  of clamping lever  300  to facilitate clamping of surgical stapler  10  (see  FIGS. 1-3 ), as will be described below. Each one of a pair of dimples  218  defined within central portion  210  of cartridge receiving half-section  200  is configured to receive a projection  312  of clamping lever  300  to releasably secure clamping lever  300  (see  FIGS. 1-3 ) in an intermediate position, between the clamped and unclamped positions, as will be described below. 
     With additional reference to  FIGS. 1-3 , base surface  220  of proximal portion  208  of elongated channel member  202  defines an elongate longitudinal slot  222  that is configured to permit passage of biasing member  506  ( FIG. 3 ), e.g., a flat spring, of firing assembly  500 , as will be described below, to bias clamping lever  300  towards the unclamped position. Positioning biasing member  506  ( FIG. 3 ) on the disposable firing assembly  500 , rather than on the reusable cartridge receiving half-section  200  or clamping lever  300  obviates the need to sterilize in and around the biasing member  506  ( FIG. 3 ) after use. In other words, neither cartridge receiving half-section  200  nor clamping lever  300  need include complex features configured to retain biasing member  506  ( FIG. 3 ) therein and, thus, are easily sterilized. Base surface  220  of elongated channel member  202  further defines a proximally located aperture  224  that is configured to receive a protrusion  504  ( FIG. 10 ) which extends outwardly from a bottom surface of stationary housing  502  of firing assembly  500  to secure and align firing assembly  500  within elongated channel member  202 , as will be described below. 
     With reference to  FIGS. 6A-6B , the proximal end of cartridge receiving half-section  200  includes a pair of vertical support members  226 . Each vertical support member  226  defines an elongated vertical slot  228  which may have a rounded bottom surface, although other configurations are contemplated. Vertical slots  228  are each dimensioned to receive rear locator bar  136  of finger  134 , which is integral with and extends from the proximal end of anvil half-section  100 , as mentioned above. During assembly, rear locator bar  136  is inserted into each of the vertical slots  228  to pivotably support anvil half-section  100  on cartridge receiving half-section  200  and axially locate cartridge receiving half-section  200  in relation to anvil half-section  100 . With positioning bar  136  supported within vertical slots  228  of support member  226 , anvil half-section  100  can be pivoted in a scissor-like manner with respect to the cartridge receiving half-section  200  between open and closed positions. 
     Referring to  FIGS. 1-3 and 7A-10 , firing assembly  500  includes stationary housing  502  having a proximal end including a protrusion  504  ( FIG. 10 ). As discussed above, the protrusion  504  extends from the bottom surface of the stationary housing  502  and is configured for receipt within aperture  224  defined within base surface  220  of elongated channel member  202  to releasably secure and align the proximal end of firing assembly  500  within proximal portion  208  of elongated channel member  202 . Likewise, SULU  400  ( FIG. 3 ) includes a pair of distal protrusions  414  ( FIG. 3 ) which are positionable within cutouts  230  formed at the distal end of channel member  202  to releasably secure the distal end of SULU  400  within the distal portion  206  of channel member  202 . As will be described in further detail below with reference to  FIGS. 11A-11B , stationary housing  502  of firing assembly  500  includes a biasing member  526  which is positioned to inhibit the proximal end of SULU  400  from fully seating within channel member  202  during assembly, thereby serving as a lockout to inhibit accidental firing of firing assembly  500 . The proximal end of SULU  400  is only moved into proper operational position within channel member  202  upon clamping of stapler  10 , wherein sufficient force is provided on SULU  400  to fully seat SULU  400  within channel member  202  against the bias of biasing member  526 , as will be discussed in further detail below. 
     Referring to  FIG. 9 , stationary housing  502  of firing assembly  500  is configured to house the working components of firing assembly  500 . For purposes herein, it suffices to say that stationary housing  502  generally supports a knife actuating bar  508 , a cam bar  510 , a guide block  512 , a slide block  514 , a firing lever  516 , as well as other inter-cooperating components (not explicitly shown) that function to sequentially fire a plurality of surgical fasteners from SULU  400  ( FIG. 3 ) and to advance knife  406  ( FIG. 3 ) through SULU  400  ( FIG. 3 ) to subsequently divide tissue between the lateral rows  115  ( FIG. 12B ) of staples upon actuation of firing lever  516 . A more detailed description of a firing assembly similar to firing assembly  500  can be found in U.S. Pat. No. 7,631,794 (“the &#39;794 Patent”), which is incorporated herein by reference in its entirety. 
     Firing lever  516  of firing assembly  500  includes first and second finger engagement members  518  and  520 , either one of which can be selectively engaged to move the firing lever  516  through a firing stroke from either side of stapler  10 . Firing assembly  500  is configured such that firing lever  516  must first be pivoted to one side or the other of firing assembly  500  before firing lever  516  can be moved through a firing stroke. A lever guide projection  522  extends from a bottom surface of each engagement member  518 ,  520 . With additional reference to  FIGS. 1-3 and 14A-14B , each lever guide projection  522  is configured and dimensioned for receipt within a respective lever guide slot  316  defined on each side of clamping lever  300  upon actuation of firing lever  516 , i.e., upon initiation of the firing stroke. As will be described below, the appropriate lever guide slot  316  of clamping lever  300  receives the corresponding lever guide projection  522  of firing lever  516  (depending on which side firing lever  516  is pivoted to prior to firing) to both guide translation of firing lever  516  and to inhibit unclamping of clamping lever  300  once the firing stroke has been initiated, i.e., once firing lever  516  has been moved distally from a fully retracted position. As used herein, a firing stroke is defined as movement of firing lever  516  from the fully retracted position to a fully advanced position, while initiation of the firing stroke is defined as the movement of firing lever  516  sufficiently so as to position one of the lever guide projections  522  within the respective lever guide slot  316 . 
     Referring again to  FIGS. 1-3 , SULU  400  includes a body  402  housing a plurality of staple pushers (not shown), a bottom cover  404 , a knife  406  having an angled sharpened leading edge or blade (not shown), a plurality of staples (not shown) operably disposed within body  402 , and a pivotally mounted safety lockout  408  ( FIGS. 11A-11B ), which is described in greater detail in the &#39;794 Patent, previously incorporated herein by reference. Body  402  has a plurality of rows of staple retaining slots  410 , e.g., four, six, etc. and a linear slotted knife track  412  centrally disposed in body  402 . Surgical stapler  10  can be dimensioned to receive or accommodate SULU&#39;s of different staple line lengths including, e.g., 60 mm, 80 mm and 100 mm. Knife  406  may include a downturned hook portion (not shown) which is configured to engage upturned hook portion  524  ( FIG. 11A ) of knife actuating bar  508  of firing assembly  500 , as also described in the &#39;794 Patent. With reference in particular to  FIGS. 11A-11B , as mentioned above, a biasing member  526  is supported in a distal end of stationary housing  502  of firing assembly  500  ( FIG. 9 ). Biasing member  526  is positioned and configured to inhibit the proximal end of SULU  400  from fully seating within channel member  202  during assembly to inhibit accidental firing of firing assembly  500 . More specifically, biasing member  526  prevents SULU  400  from fully seating in channel member  202  until stapler  10  is moved to a clamped position to prevent the firing assembly  500  ( FIG. 9 ) from operably engaging SULU  400 . The proximal end of SULU  400  is only moved into the fully seated position within channel member  202  upon clamping of stapler  10 , at which time the downturned hook portion (not shown) of knife  406  is operably positioned for engagement with upturned hook portion  524  ( FIG. 11A ) of knife actuating bar  508  ( FIG. 9 ). During a firing stroke, cam bar  510  ( FIG. 9 ) is slidably movable through body  402  to eject staples from SULU  400 . Concurrently, but after a preset delay, knife  406  is advanced through SULU  400  via advancement of knife actuating bar  508  ( FIG. 9 ) to divide tissue between the lateral rows  115  of staples. A more detailed description of a SULU similar to SULU  400  can be found in the &#39;794 Patent. 
     Referring now to  FIGS. 14A-14B , in conjunction with  FIGS. 1-3 , clamping lever  300  includes a handle portion  302  including a grip  304  and a thumb engaging abutment  306 . As mentioned above, a pair of spaced flange portions  308  are supported on the distal end of clamping lever  300 . Each flange portion  308  defines a cutout  310  dimensioned to receive a respective lateral support member  126  of anvil half-section  100  to facilitate movement of surgical stapler  10  from an unclamped position to the clamped position ( FIG. 1 ). Flange portions  308  each further include an inwardly-extending projection  312  configured to be received within dimples  218  defined within central portion  210  of cartridge receiving half-section  200  in snap-fit fashion upon pivoting of clamping lever  300  towards the clamped position to releasably secure clamping lever  300  in an intermediate position between the clamped and unclamped positions. 
     As discussed above, each flange portion  308  also defines a C-shaped recess  314  that is configured to receive cylindrical pivot member  216  of cartridge receiving half-section  200  to permit pivoting of clamping lever  300  relative to cartridge receiving half-section  200  between the unclamped and clamped positions. Clamping lever  300  is fully removable or separable from cartridge receiving half-section  200  by removing flange portions  308  of clamping lever  300  from about cylindrical pivot members  216  of cartridge receiving half-section  200 . This configuration allows for greater access to both clamping lever  300  and cartridge receiving half-section  200  and eliminates difficult-to-reach areas of both components, thereby facilitating the cleaning and sterilization of both components. 
     With continued reference to  FIGS. 14A-14B , handle portion  302  of clamping lever  300 , as also discussed above, includes a longitudinal lever guide slot  316  which extends along each side thereof. Lever guide slots  316  each define an opening, or mouth  318  configured to receive the lever guide projection  312  of a corresponding finger engagement member  518 ,  520 . More specifically, upon initiation of the firing stroke, the lever guide projection  522  moves from within mouth  518  into the corresponding lever guide slot  316 . When the lever guide projection  522  is disposed within the lever guide slot  316 , unclamping of clamping lever  300  is inhibited. 
     Handle portion  302  of clamping lever  300  further defines a plurality of apertures  320  that facilitate cleaning and sterilization of clamping lever  300  and reduce the overall weight of surgical stapler  10 . Biasing member  506  ( FIG. 3 ), which extends downwardly from firing assembly  500  through slot  222  ( FIG. 7A ) defined within cartridge receiving half-section  200 , is configured to engage the inner surface of clamping lever  300  to bias clamping lever  300  towards the unclamped position. 
     Turning now to  FIGS. 1-3 , in conjunction with  FIGS. 4A-14B , the assembly and operation of stapler  10  is described. Initially, firing assembly  500 , followed by SULU  400 , are loaded into cartridge receiving half-section  200 . In order to load firing assembly  500  into proximal portion  208  of channel member  202  of cartridge receiving half-section  200 , stationary housing  502  of firing assembly  500  is inserted into channel member  202  such that protrusion  504  ( FIG. 10 ), which extends downwardly from stationary housing  502  of firing assembly  500  (see  FIG. 10 ), is positioned within aperture  224  defined within base surface  220  of channel member  202 . Once firing assembly  500  is loaded into channel member  202 , SULU  400  can be loaded into distal portion  206  of channel member  202  via the engagement of distal protrusions  414  within cutouts  230 . However, as noted above, at this point, the proximal end of SULU  400  will only partially seat within channel member  202  of cartridge receiving half-section  200  due to the bias of biasing member  526  ( FIGS. 11A-11B ), which urges the proximal end of SULU  400  from channel member  202 . 
     Once SULU  400  and firing assembly  500  are loaded into channel member  202 , anvil half-section  100  can be assembled to cartridge receiving half-section  200  by inserting bar  136  into vertical slots  228  of vertical support members  226  of cartridge receiving half-section  200  (see  FIGS. 6A-6B ). Thereafter, anvil half-section  100  may be rotated downwardly towards cartridge receiving half-section  200  to position lateral supports members  126  ( FIGS. 4A-4B ) in substantially U-shaped recesses  212  ( FIG. 7B ). 
     With anvil half-section  100  and cartridge receiving half-section  200  pivotably engaged to one another, clamping lever  300  may be engaged to cartridge receiving half-section  200 . Referring to  FIGS. 2-3 and 14A-14B , to engage clamping lever  300  to cartridge receiving half-section  200 , flange portions  308  of clamping lever  300  are approximated about central portion  210  of cartridge receiving half-section  200  such that cylindrical pivot members  216  ( FIG. 3 ) of cartridge receiving half-section  200  are inserted into substantially C-shaped recesses  314  of clamping lever  300 . Thereafter, clamping lever  300  may be rotated in a counter-clockwise direction (according to the orientation shown in  FIG. 2 ) about pivot member  216  ( FIG. 3 ) and relative to cartridge receiving half-section  200  to the intermediate position. In the intermediate position, projections  312  ( FIG. 14B ) are received within apertures or dimples  218  ( FIG. 3 ) to retain clamping lever  300  in the intermediate position relative to cartridge receiving half-section  200 . 
     In use, in order grasp tissue between anvil half-section  100  and SULU  400 , surgical stapler  10  is positioned such that tissue to be grasped is disposed between anvil half-section  100  and SULU  400 . Thereafter, clamping lever  300  is rotated in the counter-clockwise direction from the intermediate position to the clamped position shown in  FIG. 1  to approximate staple deforming portion  106  of anvil half-section  100  and top surface of SULU  400  to grasp tissue therebetween. As clamping lever  300  is rotated towards the clamped position, lateral support members  126  are received in cutouts  310  ( FIG. 2 ) of flange portions  308  of clamping lever  300  and support fingers  125  engage SULU  400  to urge SULU  400  downwardly to be fully seated within channel member  202  of cartridge receiving half-section  200  against the bias of biasing member  526  ( FIGS. 11A-11B ). When SULU  400  is fully seated in channel member  202 , SULU  400  is moved into operative engagement with firing assembly  500  such that knife actuating bar  508  and knife  406  are operably engaged to one another to permit actuation of firing assembly  500 . 
     With surgical stapler  10  in the clamped, unfired position, firing lever  516  is pivoted to either side of stapler  10  to facilitate actuation of surgical stapler  10  from either side of the stapler  10 . With firing lever  516  pivoted to the desired side of stapler  10 , the corresponding lever guide projection  522  of the finger engagement member  518 ,  520  of firing lever  516  is positioned within the corresponding mouth  318  of a guide slot  316  of clamping lever  300  ( FIG. 1 ). In this position, stapler  10  may still be unclamped, but is ready for firing. 
     In order to fire stapler  10 , the finger engagement member  518 ,  520  of firing lever  516  is advanced distally along channel member  202 , in the direction indicated by arrow “A” in  FIG. 1 . Upon initial distal advancement of the finger engagement member  518 ,  520 , the lever guide projection  522  is moved from mouth  318  of a respective slot  316  of clamping lever  300  into the lever guide slot  316  to inhibit unclamping of clamping lever  300  during the firing stroke and to guide translation of firing lever  516  through the firing stroke. As firing lever  516  is advanced distally, slide block  514  is moved distally within stationary housing  502  of firing assembly  500  to effect corresponding movement of cam bar  510  and delayed movement of knife actuating bar  508 . As cam bar  510  is moved distally through stationary housing  502  of firing assembly  500  and into SULU  400 , the cam surfaces of cam bar  510  sequentially engage the pushers (not explicitly shown) disposed within SULU  400  to eject the staples (not explicitly shown) from body  402 , through tissue, and into staple deforming portion  106  of anvil half-section  100  for forming the staples about tissue. Concurrently, since the distal end of knife actuating bar  508  is engaged with knife  406 , knife  406 , after the preset delay, is advanced through SULU  400  to incise tissue between the lateral rows  115  ( FIG. 12B ) of staples (not shown). 
     When firing lever  516  is returned to its proximal-most position to retract cam bar  510  and knife  406  after completion of the firing stroke, lever guide projection  522  is moved from lever guide slot  316  back to mouth  318  of the respective slot  316 , thus permitting clamping lever  300  to move back to the intermediate position. Thereafter, clamping lever  300  may be disengaged and removed from cartridge receiving half-section  200  and stapler  10  may be moved to the open position to release the stapled and divided tissue. In the open position, anvil half-section  100  is spaced from cartridge receiving half-section  200  such that biasing member  526  ( FIGS. 11A-11B ) urges the proximal end of SULU  400  from a fully-seated position within channel member  202 , thereby facilitating the removal of SULU  400  from channel member  202 . 
     During a surgical procedure, SULU  400  can be replaced multiple times to facilitate multiple uses of stapler  10  on a single patient. For example, during a surgical procedure to remove a diseased portion of a vessel from the vessel, the surgical stapler  10  can be used to staple and cut tissue on opposite sides of the diseased vessel portion. The SULU  400  can be replaced after each staple and cut operation of the surgical stapler  10 . Since each SULU  400  is provided with a fresh knife  406 , tearing of tissue is minimized. After the surgical procedure, the used SULU(S)  400  and firing assembly  500  can be removed from channel member  202  and disposed of in an appropriate manner. The anvil half-section  100 , cartridge receiving half-section  200  and clamping lever  300 , as mentioned above, can then be sterilized, such as by autoclaving, and reused with a new SULU  400  and firing assembly  500  in the manner discussed above. 
     It will be understood that various modifications may be made to the embodiments of the surgical fastener applying apparatus disclosed herein. Therefore, the above description should not be construed as limiting, but merely as exemplifications of embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the present disclosure.