Patent Publication Number: US-9427231-B2

Title: Surgical stapling device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/741,459 filed Jan. 15, 2013, now U.S. Pat. No. 8,777,083, which is a continuation of U.S. patent application Ser. No. 13/221,331, filed Aug. 30, 2011, now U.S. Pat. No. 8,371,494, which is a continuation of U.S. patent application Ser. No. 11/904,566, filed Sep. 27, 2007, now U.S. Pat. No. 8,033,439, which is a continuation of U.S. patent application Ser. No. 11/436,282, filed May 18, 2006, now U.S. Pat. No. 7,275,674, which is a continuation of U.S. patent application Ser. No. 11/125,790, filed on May 10, 2005, now abandoned, which is a continuation of U.S. patent application Ser. No. 10/783,126, filed on Feb. 20, 2004, now abandoned, which is a continuation of U.S. patent application Ser. No. 09/687,815, filed on Oct. 13, 2000, now U.S. Pat. No. 6,817,508. Each of which is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates generally to a surgical stapling apparatus and, more specifically, to a surgical stapling apparatus having a single trigger for approximating anvil and cartridge assemblies and for ejecting an array of staples from the cartridge assembly. 
     2. Background of Related Art 
     Surgical stapling instruments used for applying parallel rows of staples through compressed living tissue are well known in the art, and are commonly used, for example, for closure of tissue or organs prior to transection, prior to resection, or in anastomoses, and for occlusion of organs in thoracic and abdominal procedures. 
     Typically, such surgical stapling instruments include an anvil assembly, a cartridge assembly for supporting an array of surgical staples, an approximation mechanism for approximating the anvil and cartridge assemblies, an alignment pin assembly for capturing tissue between the cartridge and anvil assemblies and for maintaining alignment between the cartridge and anvil assemblies during approximation and firing, and a firing mechanism for ejecting the surgical staples from the cartridge assembly. The approximation mechanism and the firing mechanism generally include distinct actuators for effecting approximation and firing of the staples. The alignment pin assembly can be manually operated to advance an alignment pin from the cartridge assembly into engagement with the anvil or, alternatively, the alignment pin assembly can be automatically actuated upon operation of the approximation mechanism. In instruments having a manually operated alignment pin assembly, the actuator for the alignment pin assembly is disposed at a location spaced from the handle of the instrument. 
     U.S. Pat. No. 4,930,503 to Pruitt discloses such a surgical stapling instrument. Pruitt&#39;s instrument includes a manually operated alignment pin assembly, an approximation mechanism including a rotatable knob actuator and a firing mechanism including a pivotable trigger. In use, a surgeon must first approximate the anvil and cartridge members by rotating the knob actuator. Next, the surgeon can advance the alignment pin assembly by advancing a knob supported on the central body portion of the instrument. Thereafter, the instrument can be fired by pivoting the trigger towards a stationary handle of the instrument. 
     U.S. Pat. No. 5,697,543 to Burdorff also discloses a surgical stapling instrument having an approximation mechanism, a firing mechanism and an alignment pin mechanism. The approximation and firing mechanisms each include a distinct pivotable trigger actuator. The alignment pin mechanism is operatively associated with the approximation mechanism such that upon actuation of the approximation mechanism, the alignment pin assembly is automatically advanced. 
     Known prior art surgical staplers are lacking in several respects. Firstly, the use of multiple actuators to effect approximation and firing of the instruments complicate the manufacture and operation of the instrument and, in most cases, require the surgeon to use two hands to hold and operate the instrument. Secondly, the instruments in which the alignment pin assembly is operatively associated with the approximation mechanism require that the instrument be approximated to advance the alignment pin assembly, despite the fact that a surgeon may prefer to advance the alignment pin assembly prior to approximation. In contrast, the instruments in which the alignment pin assembly is manually advanced typically require the surgeon to use a second hand to actuate the alignment pin assembly. 
     Accordingly, a continuing need exists for a surgical stapling instrument which can be operated by a surgeon with a single hand and which includes an alignment pin assembly which can be automatically or manually advanced. 
     SUMMARY 
     In accordance with the present disclosure, a surgical stapling device is provided which includes a frame having a proximal end and a distal end. A body defining a stationary handle is secured to the proximal end of the frame. A head portion including an anvil assembly and a cartridge assembly are supported on the distal end of the frame. The anvil and cartridge assemblies are movable in relation to each other between spaced and approximated positions. An approximation mechanism includes a clamp slide assembly having a distal end configured to support the cartridge assembly and a proximal end. A firing mechanism includes a thrust bar having a distal end positioned to be slidably received within the cartridge assembly. A pivotable trigger is supported on the body and is operably associated with the approximation mechanism and the firing mechanism such that the trigger is pivotable through an approximation stroke to approximate the anvil and cartridge assemblies and, subsequently, pivotable through a firing stroke to eject an array of staples from the cartridge assembly. 
     The presently disclosed surgical stapling device also has an alignment pin assembly which includes an alignment pin, a pin pusher and a bell crank. The alignment pin pusher is slidably supported on the frame between advanced and retracted positions. The alignment pin pusher includes a distal abutment member for engaging and advancing the alignment pin from a retracted position located within the cartridge assembly to an advanced position engaging the anvil assembly. The bell crank is operably connected to the clamp slide assembly and is releasably coupled to the pin pusher. Upon advancement of the clamp slide assembly, the bell crank is pivoted to concurrently advance the alignment pin pusher. The alignment pin pusher includes a pair of posts which extend through slots in the body. A manual engagement member or thumb button is supported on each post. The thumb button(s) can be pushed prior to approximation of the device to manually advance the alignment pin assembly into engagement with the anvil assembly. The thumb buttons are positioned on the body such that a surgeon is able to manually advance the alignment pin assembly using the same hand that actuates the pivotable trigger. 
     A pawl mechanism is supported in the body and includes a clamping pawl and a firing pawl. The clamping pawl functions to prevent return of the approximation mechanism after the trigger has moved through approximately three quarters of the approximation stroke. The clamping pawl also provides an audible and tactile indication that the device has been moved to the approximately three quarter approximated position. The firing pawl functions to provide an audible indication that the device is in a fire-ready position. The firing pawl also functions to lock the trigger in a compressed position after firing of the device has occurred to provide a visual indication that firing has occurred. A release button is provided to return the approximation mechanism to the retracted position at any point of operation of the device. The pivotable trigger, the release button and the thumb button are all disposed adjacent the handle portion of the device and are operable by the surgeon using a single hand. 
     The anvil assembly of the surgical stapling device is provided with a stiffener plate to provide increased strength to the assembly. By using the stiffener plate, the head portion profile can be reduced in size. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Preferred embodiments of the presently disclosed surgical stapling apparatus are described herein with reference to the drawings, wherein: 
         FIG. 1  is a perspective view of one embodiment of the presently disclosed surgical stapling device; 
         FIG. 2  is a side view of the surgical stapling device shown in  FIG. 1 ; 
         FIG. 3  is a top view of the surgical stapling device shown in  FIG. 1 ; 
         FIG. 4  is a perspective view with parts separated of the surgical stapling device shown in  FIG. 1 ; 
         FIG. 5  is a perspective view of the surgical stapling device shown in  FIG. 1  with the left body half-section removed from the handle portion of the device; 
         FIG. 6  is a perspective view of the handle portion of the surgical stapling device shown in  FIG. 7  with a body half-section removed and a portion of the frame cutaway; 
         FIG. 7  is an enlarged view of the indicated area of detail shown in  FIG. 4 ; 
         FIG. 8  is a rear perspective view of the staple pusher assembly of the surgical stapling device shown in  FIG. 1 ; 
         FIG. 8A  is a rear perspective view of the staple pusher assembly shown in  FIG. 8  with parts separated; 
         FIG. 8B  is a perspective view of an alternate embodiment of the staple pusher assembly shown in  FIG. 8  with parts separated; 
         FIG. 8C  is a perspective view of the staple pusher assembly shown in  FIG. 8B  in an assembled state; 
         FIG. 9  is an enlarged perspective view of the distal end of the surgical stapling device shown in  FIG. 1 ; 
         FIG. 9A  is an enlarged view of the indicated area of detail shown in  FIG. 9 ; 
         FIG. 9B  is a cross-sectional view taken along section lines  9 B- 9 B of  FIG. 9A ; 
         FIG. 10  is a perspective view from one side of the firing pawl of the surgical stapling device shown in  FIG. 1 ; 
         FIG. 10A  is a perspective view from the other side of the firing pawl shown in  FIG. 10 ; 
         FIG. 11  is a perspective view from one side of the clamping pawl of the surgical stapling device shown in  FIG. 1 ; 
         FIG. 11A  is a perspective view from the other side of the clamping pawl shown in  FIG. 11 ; 
         FIG. 12  is a perspective view with parts separated of the trigger and firing link of the surgical stapling device shown in FIG. 1 ; 
         FIG. 13  is a perspective view with parts separated of the release button assembly and bi-linkage assembly of the surgical stapling device shown in  FIG. 1 ; 
         FIG. 14  is a perspective view with parts separated of the pin pusher and bell crank of the surgical stapling device shown in  FIG. 1 ; 
         FIG. 15  is a side cross-sectional view of the surgical stapling device taken along section lines  15 - 15  of  FIG. 3 ; 
         FIG. 15A  is a side partial cutaway view of the handle portion of the surgical stapling device shown in  FIG. 1  with a body half-section removed; 
         FIG. 15B  is an enlarged view of the indicated area of detail shown in  FIG. 15 ; 
         FIG. 15C  is an enlarged view of the indicated area of detail shown in  FIG. 15A ; 
         FIG. 16  is a side cross-sectional view of the surgical stapling device shown in  FIG. 1  during approximation of the anvil and cartridge assemblies; 
         FIG. 16A  is a side partial cutaway view of the handle portion of the surgical stapling device shown in  FIG. 1  during approximation of the anvil and cartridge assemblies with the left body half-section removed from the handle portion of the device; 
         FIG. 16B  is an enlarged view of the indicated areas of detail shown in  FIG. 16 ; 
         FIG. 16C  is an enlarged view of the indicated area of detail shown in  FIG. 16A ; 
         FIG. 17  is a side cross-sectional view of the surgical stapling device shown in  FIG. 1  in the approximated position with the trigger in the compressed position; 
         FIG. 17A  is a side partial cutaway view of the handle portion of the surgical stapling device shown in  FIG. 1  in the approximated position with the left body half-section and frame removed from the handle portion of the device and the trigger in the compressed position; 
         FIG. 17B  is an enlarged view of the indicated area of detail shown in  FIG. 17 ; 
         FIG. 17C  is an enlarged view of the indicated area of detail shown in  FIG. 17A . 
         FIG. 18  is a side cross-sectional view of the surgical stapling device shown in  FIG. 1  in the approximated position with the trigger in a fire-ready position; 
         FIG. 18A  is a side partial cutaway view of the handle portion of the surgical stapling device shown in  FIG. 1  in the fully approximated position with the left body half-section and frame removed from the handle portion of the device and the trigger in a fire-ready position; 
         FIG. 18B  is an enlarged view of the indicated area of detail shown in  FIG. 18 ; 
         FIG. 18C  is an enlarged view of the indicated area of detail shown in  FIG. 18A ; 
         FIG. 19  is a side cross-sectional view of the surgical stapling device shown in  FIG. 1  after the device has been fired with the trigger in a compressed and locked position; 
         FIG. 19A  is a side partial cutaway view of the handle portion of the surgical stapling device shown in  FIG. 1  in the fired position with the left body half-section and frame removed from the handle portion of the device and the trigger in the compressed position; 
         FIG. 19B  is an enlarged view of the indicated area of detail shown in  FIG. 19 ; 
         FIG. 19C  is an enlarged view of the indicated area of detail shown in  FIG. 19A ; 
         FIG. 20  is a side cross-sectional view of the surgical stapling device shown in  FIG. 1  after the staples have been fired from the staple cartridge and the cartridge assembly has been moved to the retracted position; 
         FIG. 20A  is an enlarged view of the indicated area of detail shown in  FIG. 20 ; 
         FIG. 21  is a top view of tissue illustrating the staple configuration applied to tissue by the surgical stapling device shown in  FIG. 1 ; and 
         FIG. 22  is a top view of the tissue shown in  FIG. 16  illustrating the staple configuration after the tissue has been cut. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Preferred embodiments of the presently disclosed surgical stapling device will now be described in detail with reference to the drawings, wherein like reference numerals designate corresponding elements in each of the several views. 
     The presently disclosed surgical stapling device shown generally as  10  in  FIGS. 1-3  includes a body  12  defining a stationary handle  14 , a pivotable trigger  16 , an elongated central body portion  18 , a cartridge assembly  20  and an anvil assembly  22 . A manual engagement member or thumb button  24  is slidably positioned on each side of body  12 . Thumb buttons  24  are movable to manually advance an alignment pin assembly in a manner to be described in detail below. A release button  150  of release mechanism  26  is positioned on the proximal end of body  12  and is depressible to allow cartridge assembly  20  to return from an approximated position disposed adjacent to anvil assembly  22  to a position spaced from anvil assembly  22  (as shown). Operation of release mechanism  26  will also be described in detail below. 
     Referring to  FIG. 4 , body  12  is formed from a pair of molded half-sections  12   a  and  12   b . Preferably, half-sections  12   a  and  12   b  are formed of plastic, although other materials including metals may be used to form the half-sections. A cushioned gripping member  14   a  is secured to stationary handle  14  of each half-section  12   a  and  12   b . Gripping member  14   a  may be formed by injection molding a thermoplastic elastomer, such as VersaflexTM or Santaprene, to stationary handle  14 . Alternately, cushioned gripping member  14  can be formed on or secured to stationary handle  14  using any known fastening technique including adhesives, screws, welding, overmolding, etc. A pair of spaced frame members  28   a  and  28   b  extend between housing half-sections  12   a  and  12   b  and anvil assembly  22 . A central portion of frame members  28   a  and  28   b  form elongated central body portion  18 . Preferably, frame members  28   a  and  28   b  are formed of a surgical grade metal such as stainless steel. Alternately, other suitable materials meeting the requisite strength requirements may also be used. 
     Referring also to  FIGS. 9-9B , anvil assembly  22  includes a stiffener plate  30 , a spacer plate  32 , a T-track  34 , and an anvil  36 . An opening  67  is formed in anvil  36  to allow passage of alignment pin  38 . Stiffener plate  30  has a vertical portion  30   a  and a horizontal portion  30   b . A notch  30   c  is formed in the distal end of vertical portion  30   a . Notch  30   c  is configured to receive the tip  38   a  of a cartridge alignment pin  38 . Horizontal portion  30   b  of plate  30  includes a cutout  40  dimensioned to receive an interlock member  42  which will be discussed in further detail below. In the assembled state, a distal vertical portion of frame members  28   a  and  28   b  are positioned on opposite sides of vertical portion  30   a  of stiffener plate  30 . Spacer plate  32  includes a pair of legs which are positioned on opposite sides of stiffener plate  30  between stiffener plate  30  and anvil  36 . Anvil  36  defines a channel  36   a  and is positioned about spacer plate  32 . A cap  39  is positioned over the assembly to provide a smoother surface which is less likely to snag tissue during use. Cap  39  includes a groove  39   a  which defines one end of a cutting guide slot  41  formed between anvil  36  and frame member  28   b . Groove  39   a  and cutting guide slot  41  facilitate cutting of tissue with a scalpel after device  10  has been fired. T-track  34  defines a through slot  45 . Slot  45  is positioned over horizontal portion  30   b  of stiffener plate  30  between frame members  28   a  and  28   b . T-track  34  is positioned about cutout  40  to define a cavity in which interlock  42  is positioned. Preferably, the anvil assembly components and frame members  28   a  and  28   b  are secured together using rivets  44  ( FIG. 5 ). Alternately, other fastening members may be used to secure the anvil assembly components and the frame members together including screws, pins, welding, etc. Preferably, the components of anvil assembly  22  are formed of stainless steel. Alternately, other materials, including metals, having requisite strength requirements can be used to form some or all of the anvil components. 
     Referring to  FIG. 9 , anvil  36  includes a plurality of staple pockets  37  formed in the surface of the anvil. Each staple pocket  37  includes first and second staple forming cups  37   a  and  37   b  and a channeling surface  37   c  disposed around each of the staple forming cups. An anvil including such a staple forming pocket has been disclosed in U.S. Pat. No. 5,480,089 filed Aug. 19, 1994, the entirety of which is incorporated herein by reference. 
     Referring to  FIGS. 4 and 7-8A , cartridge assembly  20  includes a cartridge  50  having an array of staple receiving slots  52 . A staple pusher assembly  54  includes a plurality of pusher members  58 . Each pusher member  58  includes a plurality of fingers  58   a  configured to be slidably received within a respective staple receiving slot  52 . Fingers  58   a  are positioned behind staples  56  in slots  52  such that advancement of fingers  58   a  effects ejection of staples  56  from slots  52 . A guide channel  60  ( FIG. 15 ) formed in cartridge  50  is configured to slidably receive alignment pin  38 . A spring  64  is positioned about pin  38  to urge alignment pin  38  to a retracted position within guide channel  60 . An opening  65  formed in cartridge  50  allows alignment pin  38  to extend from guide channel  60  through anvil opening  67  (FIG. 9 A) into notch  30   c  formed in anvil assembly  22 . Operation of the alignment pin mechanism for advancing alignment pin  38  will be described in detail below. 
     Referring also to  FIGS. 8B and 8C , staple pusher assembly  54  includes multiple pusher members  58  which interengage to form pusher assembly  54 . Pusher assembly  54  may be modified by adding or subtracting pusher members  58  to accommodate different size cartridges. For example, a pusher member  58  can be removed from the assembly such as shown in  FIGS. 8B and 8C  to accommodate a smaller cartridge assembly. 
     Referring to  FIGS. 4 and 5 , surgical stapling device  10  includes a pair of clamp slide members  66   a  and  66   b , an alignment pin pusher  68  and a thrust bar  70 . Clamp slide members  66   a  and  66   b , alignment pin pusher  68  and thrust bar  70  are slidably supported between frame members  28   a  and  28   b  for movement between retracted and advanced positions in response to movement of trigger  16  through an approximation stroke and/or a firing stroke. Operation of each of the above members will be described in detail below. 
     Clamp slide members  66   a  and  66   b  form part of the approximation mechanism of the surgical stapling device. Each clamp slide member has a distal end  72 , a proximal end  74  and an elongated body  76 . Elongated body  76  includes a pair of elongated guide slots  78   a  and  78   b . Guide slots  78   a  and  78   b  are dimensioned to slidably receive pins  80   a  and  80   b  ( FIG. 15 ), respectively, which extend between frame members  28   a  and  28   b . The positioning of pins  80   a  and  80   b  in guide slots  78   a  and  78   b  functions to maintain alignment between clamp slide members  66   a  and  66   b  and frame members  28   a  and  28   b  during movement between the advanced and retracted positions and to limit the extent of longitudinal movement of clamp slide members  66   a  and  66   b , i.e., the fully advanced position of the clamp slide members is reached when the proximal end of slot  78   a  engages pin  80   a  and the fully retracted position of the clamp slide members is reached when the distal end of slot  78   a  engages pin  80   a . Distal end  72  of each clamp slide member  66   a  and  66   b  includes a head portion  82 . Each head portion  82  has a plurality of openings  84  configured to receive a fastening member  86  ( FIG. 5 ) for securing clamp slide members  66   a  and  66   b  together in spaced relation. In the assembled state, clamp slide members  66   a  and  66   b  are spaced from each other to define an elongated channel in which pin pusher  68  and thrust bar  70  are slidably disposed. Distal end  72  of clamp slide members  66   a  and  66   b  define a cartridge support receptacle for receiving cartridge assembly  20 . A series of dimples  85  on each of the clamp slide members function to frictionally retain cartridge assembly  20  within the cartridge support. Proximal end  74  of clamp slide members  66   a  and  66   b  each include a hole  87  for receiving a pin  88  of the actuation assembly which will be described in detail below. 
     Referring also to  FIG. 14 , alignment pin pusher  68  defines a channel  69  along its length which is dimensioned to slidably receive thrust bar  70 . Alignment pin pusher  68  includes a vertical portion  90  having an abutment member  91  configured to engage the proximal end  38   b  ( FIG. 4 ) of alignment pin  38  such that when alignment pin pusher  68  is moved to an advanced position (in the manner described below), alignment pin  38  is advanced from within cartridge  50  through opening  65  in cartridge  50  and opening  67  in anvil  36  into notch  30   c  of anvil assembly  22 . Alignment pin pusher  68  includes a pair of elongated slots  92   a  and  92   b . Pins  80   a  and  80   b  ( FIG. 15 ) extend through slots  92   a  and  92   b , respectively, to guide alignment pin pusher  68  during movement between the advanced and refracted positions. The proximal end of alignment pin pusher  68  includes a pair of spaced legs  68   a  and  68   b . Each leg  68   a  and  68   b  includes a radially extending post  120  which is dimensioned to extend through elongated slots  122  ( FIG. 4 ) formed in body half-sections  12   a  and  12   b . Thumb buttons  24  are fastened to posts  120  to facilitate manual actuation of alignment pin pusher  68 . A C-clip receptacle  126  is formed on alignment pin pusher  68  and is dimensioned to releasably receive link  94  of bell crank  96 . Operation of bell crank  96  and the handle actuation assembly will be described in detail below. 
     Referring again to  FIG. 4 , thrust bar  70  is slidably positioned within channel  69  defined within alignment pin pusher  68 . The distal end of thrust bar  70  includes an engagement head  100  configured to engage staple pusher assembly  54 . Thrust bar  70  also includes a pair of elongated slots  102   a  and  102   b  which are dimensioned to slidably receive pins  80   a  and  80   b  (FIG.  15 ). As discussed above with respect to clamp slide members  66   a  and  66   b , pins  80   a  and  80   b  function not only to guide the movement of thrust bar  70  between the retracted and advanced positions, but also to define the fully advanced and fully retracted positions of thrust bar  70 . As illustrated in  FIG. 15 , slots  102   a  and  102   b  in thrust bar  70  are longer than slots  78   a  and  78   b  formed in clamp slides  66   a  and  66   b , respectively. The increased length of slots  102   a  and  102   b  permit thrust bar  70  to be advanced distally from the approximated position independently of clamp slides  66   a  and  66   b  through cartridge assembly  20  to eject staples from cartridge assembly  20 . The proximal end of thrust bar  70  is adapted to engage a biasing member  71  which is supported in tension between frame  28   a  and thrust bar  70  to urge thrust bar  70  to the retracted position. The proximal end of thrust bar  70  also includes a notch  104  which is configured to receive the distal end of a firing link  106  and will be discussed in further detail below. 
     Referring to  FIGS. 4-6, and 10-13 , a handle actuation assembly includes pivotable trigger  16 , a bi-linkage assembly  111  including a front link  112  and a rear link  114 , bell crank  96 , firing link  106  a clamping pawl  108  and a firing pawl  110 . A release mechanism  26  includes a release button  150  and a release lever  152  provided within body  12 . 
     Pivotable trigger  16  is pivotably secured between body half-sections  12   a  and  12   b  about pivot members  116  which are integrally formed on opposite sides of trigger  16 . Alternately, a pivot pin can be used to pivotably support trigger  16  between the body half-sections. Trigger  16  includes a cushioned grip  16   a , which may be secured to trigger  16  in the manner discussed above with respect to stationary handle  14 , and a rearward extension  115  positioned beneath bi-linkage assembly  111 . Rear link  114  of bi-linkage assembly  111  has a rear end pivotably secured about pivot pin  113  which extends between body members  12   a  and  12   b  and a forward end pivotably fastened to the rear end of front link  112  by pivot pin  118 . It is noted that release button  150  is also pivotably secured to pivot pin  113 . The forward end of front link  112  is pivotably fastened to clamp slide members  66   a  and  66   b  by pin  88 . When trigger  16  is pivoted about pivot members  116 , rearward extension  115  urges bi-linkage assembly  111  from a position in which the longitudinal axes of front and rear links  112  and  114  are misaligned to a position in which the axes of front and rear links  112  and  114  are substantially aligned. In the substantially aligned position, links  112  and  114  are moved to an overcenter position slightly past actual alignment. By moving the bi-linkage assembly slightly overcenter or past the aligned position, bi-linkage assembly  111  will not return to the misaligned position until engaged by the release mechanism  26 . Since the rear end of rear link  114  is fastened within body  12 , as bi-linkage assembly  111  is moved from the misaligned to the aligned position, front link  112  is advanced distally to advance clamp slide members  66   a  and  66   b  distally. Advancement of clamp slide members  66   a  and  66   b  effects corresponding advancement of cartridge assembly  20  to effect approximation of anvil and cartridge assemblies  22  and  20 , respectively. 
     Referring to  FIGS. 4 and 15 , thrust bar  70  includes a forward elongated slot  103 . Rivets  117 , which extend between clamp slide members  66   a  and  66   b , also extend through slot  103 . When clamp slide members  66   a  and  66   b  are advanced from a retracted position to an advanced position, rivets  117  engage the forward end of slot  103  to advance thrust bar  70  concurrently with clamp slide members  66   a  and  66   b . As illustrated in  FIG. 15 , slot  103  is of a length to allow thrust bar  70  to advance distally beyond the approximated position independently of clamp slide members  66   a  and  66   b.    
     Referring to  FIGS. 4 and 14 , bell crank  96  is pivotably secured between frame members  28   a  and  28   b  by pivot member  134 . As discussed above, link  94  of bell crank  96  is releasably positioned within C-clip  126  of alignment pin pusher  68 . Bell crank  96  includes a pair of spaced sidewalls  96   a  and  96   b . Each sidewall includes an inwardly extending cam member  138  which is configured to be received within a cam slot  140  formed in the proximal end of clamp slides  66   a  and  66   b . As clamp slides  66   a  and  66   b  are advanced distally, the walls defining cam slots  140  engage cam members  138  to pivot bell crank  96  about pivot member  134 . When bell crank  96  is pivoted, post  94  urges pin pusher  68  distally to advance abutment member  91  through guide channel  60  to advance alignment pin  38  into engagement with anvil assembly  22 . Cam slots  140  are configured to quickly pivot bell crank  96  during the initial advancement of clamp slides  66   a  and  66   b  such as to quickly advance alignment pin pusher  68  and alignment pin  38  during the initial stage of approximation. 
     Referring again to  FIGS. 4 and 13 , release mechanism  26  includes release button  150  and release lever  152 . As discussed above, release button  150  includes a rear end which is pivotably secured to pivot pin  113 . Pivot pin  113  is secured between body members  12   a  and  12   b . The forward end of release button  150  includes a slot  154  dimensioned to slidably receive a rod  156  formed on a rear end of release lever  152 . The forward end of release lever  152  is pivotably secured between body half-sections  12   a  and  12   b . An engagement member  158  projects downwardly from the bottom of release lever  152  and is positioned to abut bi-linkage assembly  111  when release button  150  is depressed to urge bi-linkage assembly  111  from the substantially aligned overcenter position to the misaligned position. 
     Referring to  FIGS. 4 and 10-12 , surgical stapling apparatus  10  includes a pawl assembly including clamping pawl  108  and firing pawl  110 . Clamping pawl  108  is pivotably secured about pivot member  170  in semi-circular slot  172  ( FIG. 4 ) in frame  28   a . A spring  174  is secured between clamping pawl  108  and frame  28   a  to urge clamping pawl  108  to rotate in a clockwise direction as viewed in  FIG. 4 . Clamping pawl  108  includes a cam surface  176  having a recess  178  positioned to engage cam member  180  ( FIG. 16B ) formed on extension  115  of trigger  16 . When cam member  180  on trigger  16  is positioned in recess  178  of cam surface  176  (this occurs after the clamp slides  66   a  and  66   b  have been moved through approximately three quarters of the approximation stroke), trigger  16  is prevented from being returned by spring  182  to a non-compressed position. Thus, the cartridge assembly  20  and the anvil assembly  22  are maintained in a three quarter approximated position even when trigger  16  is released by the surgeon. Firing pawl  110  is pivotably secured about pivot member  184  in semi-circular slot  186  ( FIG. 4 ) formed in frame  28   b . Spring  188  is secured between firing pawl  110  and frame  28   b  to urge the firing pawl in a clockwise direction as viewed in  FIG. 4 . Firing pawl  110  includes a cam surface  190  having a recess  192  for engaging a cam member  180 ′ formed on a side of extension  115  of trigger  16  opposite cam member  180 . During movement of trigger  16  through the firing stroke, cam member  180 ′ is moved into recess  192  to lock trigger  16  in a compressed position after firing has been completed. This provides an audible and visual indication to the surgeon that firing has been completed. Additional operational details of the pawl assembly will be described in the following description of the operation of surgical stapling device  10 . 
     Operation of the surgical stapling device will now be described in detail with reference to  FIGS. 15-20A . It is noted that the movements of the various components will be described from the vantage point of one viewing the instrument as positioned in the referenced FIG. 
       FIGS. 15-15C  illustrate surgical stapling device  10  prior to use. As illustrated, cartridge assembly  20  and anvil assembly  22  are in spaced relation, trigger  16  is in the non-compressed position, and clamp slides  66   a  and  66   b  and thrust bar  70  are in the retracted position (note pins  80   a  and  80   b  are positioned in the forward end of slots  78   a  and  78   b  of clamp slides  66   a  and  66   b  and slots  102   a  and  102   b  of thrust bar  70 ). When thrust bar  70  is in the retracted position, the forward end of firing link  106  is positioned forwardly of notch  104  in thrust bar  70 . Since link  106  cannot engage notch  104 , device  10  cannot be fired in this position. Alignment pin pusher  68  and alignment pin  38  are also in the refracted position with post  94  of bell crank  96  engaged in C-clip  126  of alignment pin pusher  68 . At this point, a surgeon could manually advance alignment pin pusher  68  and alignment pin  38  by pushing thumb button(s)  24  ( FIG. 1 ) towards the forward end of slots  122  formed in body halves  12   a  and  12   b . This operation would disengage post  94  from C-clipl 26 . 
       FIGS. 16-16C  illustrate surgical stapling device  10  during the approximation stroke of trigger  16 . As illustrated, trigger  16  is moved in the direction indicated by arrow “A” to move extension  115  of trigger  16  in a direction to urge bi-linkage assembly  111  from the misaligned position towards the substantially aligned position. Because rear link  114  is secured to body  12  about pin  113 , front link  112  extends forwardly. Front link  112  is secured to clamp slides  66   a  and  66   b  by pin  88 . As front link  112  is extended forwardly, clamp slides  66   a  and  66   b  are advanced in the direction indicated by arrow “B” from the retracted position towards the advanced or approximated position. Note the position of pins  80   a  and  80   b  in slots  78   a  and  78   b  and  102   a  and  102   b . As discussed above, rivets  117  extend between clamp slides  66   a  and  66   b  through  103  formed in thrust bar  70 . As clamp slides  66   a  and  66   b  are advanced, rivet  88  engages the forward end of slot  103  formed in thrust bar  70  to simultaneously advance thrust bar  70 . As clamp slides  66   a  and  66   b  are advanced, engagement between cam slots  140  and cam member  138  pivots bell crank  96  about pivot member  134  to urge pin pusher  68  distally to advance alignment pin  38  into notch  30   c  of anvil assembly  22 . 
     Referring to  FIG. 16B , as trigger  16  is pivoted in the direction indicated by arrow “A”, cam member  180  on extension  115  of trigger  16  rides up cam surface  176  against the bias of spring  174  ( FIG. 4 ). When trigger  16  is pivoted to advance clamp slide members  66   c  and  66   b  through approximately three quarters of the approximation stroke, cam member  180  snaps into cam recess  178  to provide an audible and a tactile indication that approximately three quarter approximation has been reached. At this point, the positioning of cam member  180  in cam recess  178  prevents spring  182  from returning trigger  16  to the non-compressed position without activating release mechanism  26 . Operation of the release mechanism will be discussed below. 
       FIGS. 17-17C  illustrate the surgical stapling device  10  in the fully approximated position with trigger  16  in the compressed position. As illustrated, extension  115  on trigger  16  has been pivoted to move bi-linkage assembly  111  to the substantially aligned positioned (slightly over-center position) and clamp slide assembly has been fully advanced such that cartridge assembly  20  and anvil assembly  22  are in the approximated position. Once again, note the position of pins  80   a  and  80   b  within clamp slide slots  78   a  and  78   b  and thrust bar slots  102   a  and  102   b . Because pins  80   a  and  80   b  are located at the proximal end of clamp slide slots  78   a  and  78   b , only thrust bar  70  can be advanced further distally. If the alignment pin pusher was manually advanced prior to approximation, disengaging post  94  from C-clip  126 , advancement of clamp slides  66   a  and  66   b  to the fully advanced position moves post  94  of bell crank  96  back into engagement with C-clip  126 . Thus, when clamp slides  66   a  and  66   b  are returned to their refracted position, cam slots  140  in clamp slides  66   a  and  66   b  pivot bell crank  96  in a direction to move pin pusher  68  to the retracted position. 
     Referring to  FIG. 17B , trigger  16  has been pivoted to remove cam member  180  from cam recess  178  in clamping pawl  108 . As bi-linkage assembly  111  moves overcenter to the substantially aligned position, rear link  114  engages abutment member  200  ( FIGS. 10-11 ) formed on clamping pawl  108  and firing pawl  110  to rotate the clamping and firing pawls approximately 10° counter-clockwise. This rotation removes cam surface  176  from the path of cam member  180  during the return of trigger  16  to the non-compressed position. 
     Referring to  FIG. 17C  cam member  180 ′ formed opposite to cam member  180  on extension  115  of trigger  16  is now positioned above cam surface  190  of firing pawl  110 . As trigger  16  is released by the surgeon and returned to the non-compressed position by spring  182 , cam member  180 ′ moves along the backside  190   a  of cam surface  190 . As cam member  180 ′ reaches the bottom edge of backside  190   a , cam member  180 ′ moves over a nub  220  formed on firing pawl  110 . Movement of cam member  180 ′ over nub  220  provides an audible click and a tactile indication that surgical stapling apparatus  10  is in a fire-ready position. 
       FIGS. 18-18C  illustrate the surgical stapling device  10  in the fully approximated position with the trigger  16  in the non-compressed position. As illustrated, with thrust bar  70  in an advanced position, notch  104  is now aligned with firing link  106  such that movement of trigger  16  through the firing stroke will effect advancement of thrust bar  70 . Referring to  FIG. 18C , camming member  180 ′ is now positioned below cam surface  190  of firing pawl  110 . 
       FIGS. 19-19C  illustrate surgical stapling instrument  10  after trigger  16  has been moved through the firing stroke. As illustrated, thrust bar  70  has been advanced distally to eject staples from cartridge assembly  20 . Note pins  80   a  and  80   b  are now positioned adjacent the proximal end of slots  102   a  and  102   b . Referring particularly to  FIG. 19C , cam member  180 ′ of extension  115  of trigger  16  has moved up cam surface  190  and is positioned in recess  192 . Engagement between cam member  180 ′ and recess  192  prevents spring  182  from returning trigger  16  to the non-compressed position to provide a visual indication to the surgeon that the surgical device has been fired. Movement of cam member  180 ′ into recess  192 , also provides an audible indication that firing of the device has occurred. 
       FIG. 20  illustrates surgical stapling device  10  after it has been fired and the release mechanism  26  has been depressed to return bi-linkage assembly  111  to the misaligned position. Once bi-linkage assembly  111  is moved back overcenter, spring  71  returns thrust bar  70  and clamp slide members  66   a  and  66   b  proximally to return links  112  and  114  to the misaligned position. 
     As illustrated in  FIG. 20A , interlock  42  is normally urged by pusher assembly  54  to a position located within recess  40 . After cartridge assembly  20  has been fired, pusher assembly  54  is no longer positioned to bias interlock  42  into recess  40 . Until a new cartridge has been inserted into surgical stapling device  10 , interlock  42  will extend from recess  40  to prevent thrust bar  70  from being advanced distally. 
       FIG. 21  illustrates tissue  300  having an applied array of staples  310  formed therein.  FIG. 22  illustrates tissue  300  after it has been bisected with a scalpel (not shown). 
     It will be understood that various modifications may be made to the embodiments disclosed herein. For example, the components of the surgical stapling device can be formed of any material suitable for surgical use and having the required strength characteristics. 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.