Patent Publication Number: US-2022211372-A1

Title: Loading unit and adapter with modified coupling assembly

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/800,100, filed on Feb. 25, 2020, which claims the benefit of, and priority to, U.S. Provisional Patent Application No. 62/828,204, filed on Apr. 2, 2019, the entire contents of which are hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     1. Technical Description 
     The present disclosure is directed to a loading unit and adapter assembly for a surgical stapling device and, more particularly, to a loading unit and adapter assembly for a surgical stapling device including a modified coupling assembly for connecting the loading unit to the adapter assembly. 
     2. Background of Related Art 
     Stapling devices for suturing body tissue during surgical procedures are well known. The stapling devices include a tool assembly having an anvil and a staple cartridge that supports a plurality of surgical staples. The staples can be driven from the staple cartridge into the anvil to staple tissue clamped between the staple cartridge and the anvil. Some stapling devices include a knife member that is adapted to cut body the tissue clamped between the anvil and the staple cartridge as the tissue is being stapled. These stapling devices have reduced the amount of time required to perform surgical procedures by reducing the time required to join tissue segments during the surgical procedure. 
     In order to minimize costs associated with performing surgical procedures, known stapling devices include a loading unit or reload that is removably attached to an adapter assembly of the stapling device. After the staples are fired from the staple cartridge into the anvil through the tissue, the loading unit can be replaced to facilitate reuse of the stapling device. 
     Generally, a loading unit includes a proximal body portion and a tool assembly pivotally supported on a distal end of the proximal body portion. The proximal body portion of the loading unit supports a drive assembly and an articulation link and includes a proximal end that is adapted to engage an adapter or body of a stapling device such that the drive assembly of the loading unit is coupled with a drive member of the stapling device and the articulation link of the loading unit is coupled to an articulation mechanism of the stapling device. 
     In some instances, if the drive assembly of the loading unit is not properly coupled to the drive member of the surgical stapling device, the tool assembly can be locked in a clamped position after the stapling device is fired. In addition, coupling of the articulation link of the loading unit to the articulation mechanism of the stapling device generally requires multiple components with clearances that cause the tool assembly to wobble during firing and retraction of the drive assembly. 
     A continuing need exists in the stapling arts for a stapling device including a loading unit that can be selectively coupled to a body of the stapling device in a manner to ensure proper engagement of the components of the reload with the components of the stapling device to provide a reliable and stable device. 
     SUMMARY 
     One aspect of the disclosure is directed to a surgical stapling device including a body portion and a tool assembly. The body portion includes a housing, a base member positioned on the housing, and a drive assembly supported within the housing. The base member defines a longitudinal slot and spaced keyways. The drive assembly includes a proximal portion having a connector and a distal portion including a working end. The drive assembly is movable within the housing between a retracted position in which the working end of the drive assembly is positioned within the longitudinal slot of the base member and an advanced position. The tool assembly includes a first jaw, a second jaw, and a mounting member. The first jaw and the second jaw are secured to the mounting member such that the first jaw is movable in relation to the second jaw between an open position and an unclamped position. The mounting member defines a channel having an open end that is dimensioned to receive the base member of the body portion. The mounting member includes locking tabs positioned within the channel. Each of the locking tabs is configured to be received within one of the spaced keyways of the base member to releasably secure the tool assembly to the body portion. 
     In some embodiments, each of the spaced keyways includes an axial portion and a radial portion, wherein axial movement of the tool assembly in relation to the body portion moves the locking tabs through the axial portions of the keyways and rotatable movement of the tool assembly in relation to the body portion moves the locking tabs through the radial portions of the spaced keyways to secure the tool assembly to the body portion. 
     In certain embodiments, the working end of the drive assembly is configured to be movable through the tool assembly when the drive assembly is moved from the retracted position to the advanced position to move the tool assembly from the open position to the clamped position and to fire the tool assembly. 
     In embodiments, the body portion includes a lead screw and an inner tube, and the lead screw is rotatable to axially advance the inner tube within the housing, wherein the inner tube engages the connector of the drive assembly to axially advance the drive member within the housing from the retracted position to the advanced position. 
     In some embodiments, the body portion includes a biasing member that is positioned between a distal portion of the inner tube and the connector to urge the drive assembly distally within the housing in relation to the inner shaft. 
     In certain embodiments, the first jaw includes an anvil and the second jaw includes a channel member that supports a staple cartridge. 
     In embodiments, the working end of the drive member includes a vertical strut having a knife edge and the channel member and staple cartridge define longitudinal slots that receive the vertical strut when the tool assembly is secured to the body portion. 
     In some embodiments, when the locking tabs are in the axial portions of the spaced keyways, the vertical strut of the working end of the drive assembly is misaligned with the longitudinal slot in the channel member such that when the tool assembly is moved towards the base member to move the locking tabs through the axial portions of the spaced keyways, the working end of the drive assembly abuts the channel member to prevent axial movement of the drive assembly in relation to the tool assembly. 
     In certain embodiments, axial advancement of the base member within the channel of the mounting member when the working end of the drive assembly is in abutment with the channel member causes the drive assembly to move axially in relation to the inner tube to compress the biasing member. 
     In embodiments, when the tool assembly is rotated in relation to body portion to move the locking tabs through the radial portions of the spaced keyways, the vertical strut of the drive assembly is moved into alignment with the longitudinal slots of the channel member and the staple cartridge. 
     In some embodiments, when the vertical strut is rotated into alignment with the longitudinal slots of the channel member and the staple cartridge, the biasing member urges the working end of the drive assembly into a proximal portion of the tool assembly. 
     In certain embodiments the housing includes a distal portion, and the base member is pivotally supported on the distal portion of the housing. 
     In embodiments, the body portion includes a platform that is supported on the distal portion of the housing. 
     In some embodiments, the base member defines a transverse slot and the platform includes a flange that is pivotably received within the transverse slot of the base member. 
     In certain embodiments, the platform defines upper and lower recesses that diverge outwardly in a distal direction. 
     In embodiments, the drive assembly includes an elongate flexible body having an upper body portion and a lower body portion, and the platform is positioned between the upper and lower body portions. 
     In some embodiments, the stapling device includes upper and lower U-shaped guides, wherein the upper guide is positioned in the upper recess of the platform and receives the upper body portion of the flexible body of the drive assembly and the lower guide is positioned in the lower recess of the platform and receives the lower body portion of the flexible body of the drive assembly. 
     In certain embodiments, each of the upper and lower U-shaped guides has a proximal portion including a pivot member, wherein the pivot members pivotably support the upper and lower U-shaped guides within the upper and lower recesses. 
     In embodiments, the stapling device includes an upper blowout plate assembly positioned within the upper guide on opposite sides of the upper body portion of the flexible body and a lower blowout plate assembly positioned within the lower guide on opposite sides of the lower body portion of the flexible body. 
     In some embodiments, the stapling device includes an articulation assembly having an articulation drive member, a first articulation link secured to the articulation drive member, a second articulation link pivotably coupled to the first articulation link and to the base member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments of the presently disclosed loading unit and adapter assembly are described herein below with reference to the drawings, wherein: 
         FIG. 1  is a side perspective view of a surgical stapling device including an exemplary embodiment of the presently disclosed loading unit and adapter assembly; 
         FIG. 2  is an exploded perspective view of the loading unit of the surgical stapling device shown in  FIG. 1 ; 
         FIG. 2A  is a perspective view from the distal end of an end cap of the loading unit of the surgical stapling device shown in  FIG. 2 ; 
         FIG. 3  is a side perspective view of the loading unit and adapter assembly shown in  FIG. 1  with the loading unit separated from the adapter assembly; 
         FIG. 4  is a perspective view of the proximal end of the loading unit and the distal end of the adapter assembly with the loading unit separated from the adapter assembly; 
         FIG. 5  is an exploded perspective view of the adapter assembly of the surgical stapling device shown in  FIG. 1 ; 
         FIG. 6  is an enlarged view of the indicated area of detail shown in  FIG. 3 ; 
         FIG. 6A  is a side perspective view of the pivot base of the adapter assembly shown in  FIG. 5 ; 
         FIG. 6B  is a top perspective view of the pivot base of the adapter assembly shown in  FIG. 6A ; 
         FIG. 7  is a side perspective view of a distal end of the adapter assembly shown in  FIG. 3  with an outer tube and a housing half-section removed; 
         FIG. 7A  is a side perspective view of a drive assembly guide of the adapter assembly shown in  FIG. 5 ; 
         FIG. 8  is a side perspective view of the distal end of the adapter assembly shown in  FIG. 7  with the outer tube, the housing half-section, and the drive member removed; 
         FIG. 9  is a cross-sectional view taken along section line  9 - 9  of  FIG. 3 ; 
         FIG. 10  is an enlarged view of the indicated area of detail shown in  FIG. 9 ; 
         FIG. 11  is a cross-sectional view of the loading unit and the distal end of the adapter assembly of the surgical stapling device shown in  FIG. 1  with the loading unit separated from the adapter assembly; 
         FIG. 12  is an enlarged view of the indicated area of detail shown in  FIG. 9 ; 
         FIG. 13  is a cross-sectional view of the loading unit and the distal end of the adapter assembly of the surgical stapling device shown in  FIG. 11  as the loading unit is moved axially towards the adapter assembly to initiate coupling of the loading unit with the adapter assembly; 
         FIG. 14  is a cross-sectional view of the loading unit and the distal end of the adapter assembly of the surgical stapling device shown in  FIG. 13  as the loading unit continues to be axially advanced and coupled to the adapter assembly; 
         FIG. 15  is an enlarged view of the indicated area of detail shown in  FIG. 5 ; 
         FIG. 16  is a cross-sectional view of a proximal portion of the adapter assembly shown in  FIG. 14  with a drive member biasing member of the adapter assembly fully compressed; 
         FIG. 17  is a cross-sectional view taken along section line  17 - 17  of  FIG. 14 ; 
         FIG. 18  is a cross-sectional view taken along section line  18 - 18  of  FIG. 14 ; 
         FIG. 19  is a side cross-sectional view of the loading unit and the distal end of the adapter assembly of the surgical stapling device shown in  FIG. 14  as the loading unit is rotated in relation to the adapter assembly to fully couple to loading unit to the adapter assembly; 
         FIG. 20  is a cross-sectional view taken along section line  20 - 20  of  FIG. 19 ; and 
         FIG. 21  is a cross-sectional view taken along section line  21 - 21  of  FIG. 19 . 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The presently disclosed stapling device including a loading unit and an adapter assembly will now be described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. However, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure and may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure. 
     In this description, the term “proximal” is used generally to refer to that portion of the device that is closer to a clinician, while the term “distal” is used generally to refer to that portion of the device that is farther from the clinician. In addition, the term “endoscopic” is used generally used to refer to endoscopic, laparoscopic, arthroscopic, and/or any other procedure conducted through a small diameter incision or cannula. Further, the term “clinician” is used generally to refer to medical personnel including doctors, nurses, and support personnel. 
       FIGS. 1 and 2  illustrate a surgical stapling device shown generally as stapling device  10  including a handle assembly  100 , and exemplary embodiments of the presently disclosed tool assembly  200  (e.g., an end effector, multiple or single use tool assembly) and adapter assembly  300 . The adapter assembly  300  includes an elongate body  308  having a distal portion that supports the tool assembly  200 . The handle assembly  100  is configured for releasable connection to the adapter assembly  300 , and, in turn, the adapter assembly  300  is configured for releasable connection to the tool assembly  200 . Together, the handle assembly  100  and the adapter assembly  300  cooperate to actuate the tool assembly  200 . The stapling device  10  may be an electromechanically powered system and the handle assembly  100  may support a power source, e.g., a battery pack. Alternatively, the stapling device  10  may be manually actuated and the adapter assembly  300  may be fixedly secured to the handle assembly  100 . 
     In embodiments, the handle assembly  100  includes a stationary handle  102  and a plurality of actuation switches  104 . The actuation switches  104  are provided to control various functions of the stapling device  10  including approximation of the tool assembly  200 , and cutting, and firing of tissue. 
       FIG. 2  illustrates an exemplary embodiment of the presently disclosed tool assembly  200  of the stapling device  10  ( FIG. 1 ) which includes an anvil assembly  210 , and a cartridge assembly  211 . The cartridge assembly  211  includes a cartridge channel member  212 , and a staple cartridge  214 . The anvil assembly  210  includes an anvil cover  220  and an anvil plate  222 . The anvil cover  220  includes a mounting portion  224  that defines a proximal cutout  226 , and a cover portion  228  that extends along the distal portion of the anvil plate  222 . The mounting portion  224  includes spaced proximal extensions  224   a  that define the cutout  226  and bores  225 . The tool assembly  200  also includes a mounting member  216  that is secured to the proximal portions of the anvil assembly  210  and the cartridge assembly  211 . 
     The anvil plate  222  includes a tissue engaging surface  230  that is in opposed relation to the staple cartridge  214  and defines a plurality of staple deforming recesses (not shown). The anvil plate  222  has a side opposite to the tissue engaging surface  230  that defines an elongated recess  232  that is configured to receive an upper beam  336  ( FIG. 4 ) of a drive assembly  320  ( FIG. 14 ) of the adapter assembly  300  as described in further detail below. The anvil cover  220  is secured to the anvil plate  222 , e.g., by welding or crimping, such that the cover portion  228  encloses the elongated recess  232 . The anvil plate  222  also defines an elongated knife slot  236  that extends through the tissue engaging surface  230  of the anvil plate  222  into the elongated recess  232 . 
     The cartridge channel member  212  includes a bottom wall  240  and a pair of spaced side walls  242  that define a channel  244 . The channel  244  is dimensioned to receive the staple cartridge  214 . The side walls  242  of the channel member  212  each include a proximal extension  246  that defines a bore  246   a.  The bottom wall  240  defines a longitudinal slot  243  ( FIG. 17 ) that is open at its proximal end to receive a working end  328  ( FIG. 5 ) of the drive assembly  320  as described in detail below. The staple cartridge  214  also defines a longitudinal slot  214   a  that is aligned with the longitudinal slot  243  of the channel member  212 . 
     Referring also to  FIG. 2A , the mounting member  216  includes a substantially cylindrical proximal portion  250  and a distal portion  252 . The distal portion  252  of the mounting member  216  defines an I-shaped slot  255  ( FIG. 2A ) and includes flat outer side walls  254  that define bores  254   a.  The side walls  254  are received between the pair of proximal extensions  224   a  of the mounting portion  224  of the anvil cover  220  within the cutout  226  such that the bores  225  of the proximal extensions  224   a  are aligned with the bores  254   a  of the mounting member  216 . The extensions  246  of the side walls  242  of the channel member  212  are also positioned between the flat side walls  254  of the mounting member  216  and the proximal extensions  224   a  of the anvil cover  220  such that the bores  246   a  are aligned with the bores  225  of the anvil cover and with the bores  254   a  of the mounting member  216 . 
     A pivot pin  260  is positioned through each of the bores  225  of the anvil cover  220 , the bores  246   a  of the channel member  212 , and the bores  254   a  of the mounting member  216  on each side of the anvil assembly  210  to fixedly secure the anvil assembly  210  to the mounting member  216 , and to pivotably secure the cartridge channel member  212  in relation to the mounting member  216  and the anvil assembly  210 . The channel member  212  is pivotal about the pivot pins  260  from an open position ( FIG. 1 ) to a clamped position ( FIG. 3 ). 
     Referring to  FIGS. 2-4 , a distal portion of the adapter assembly  300  ( FIG. 3 ) is dimensioned to be received in the proximal portion  250  ( FIG. 2 ) of the mounting member  216  to releasably couple the tool assembly  200  to the adapter assembly  300 . More specifically, the proximal portion  250  of the mounting member  216  defines a channel  262  that is configured to receive a pivot base  302  ( FIG. 4 ) of the adapter assembly  300  which is described in further detail below. The mounting member  216  includes locking tabs  264  ( FIG. 4 ) that project inwardly from an inner surface of the mounting member  216  into the channel  262 . In embodiments, an outer surface of the mounting member  216  includes a pair of arrows  270 ,  272  that extend in directions perpendicular to each other. A first arrow  270  of the pair of arrows points in a direction that is parallel to a longitudinal axis “X” of the tool assembly  200  and the second arrow  272  of the pair of arrows points in a direction that is perpendicular to the longitudinal axis “X” of the tool assembly  200 . The arrows  270 ,  272  assist a clinician with coupling the tool assembly  200  to the adapter assembly  300  as described in detail below. 
     Referring to  FIGS. 4-10 , the adapter assembly  300  includes a housing  304  ( FIG. 9 ) that includes an upper housing portion  304   a  and a lower housing portion  304   b.  The upper and lower housing portions  304   a,    304   b  are secured together using any of a variety of known fastening technique, e.g., welding, interlocking structure, etc., to define a cavity  306  ( FIG. 9 ) that receives other components of the adapter assembly  300 . A distal portion of each of the upper and lower housing portions  304   a,    304   b  defines a recess  310  and a cutout  312  ( FIG. 5 ). The recesses  310  of the upper and lower housing portions  304   a,    304   b  diverge outwardly in the distal direction. The upper and lower housing portions  304   a,    304   b  are supported within an outer cylindrical housing  313  to prevent separation of the upper housing portion  304   a  from the lower housing portion  304   b.    
     The cutouts  312  of the upper and lower housing portions  304   a,    304   b  define a slot in the distal end of the housing  304  that receives a platform  314  ( FIG. 5 ) when the upper and lower housing portions  304   a,  and  304   b  are assembled. The platform  314  can be secured between the upper and lower housing portions  304   a,    304   b  using any known fastening technique including screws, welding or the like. The platform  314  defines upper and lower recesses  316  ( FIG. 5 ) that have shapes that correspond to the shapes of the recesses  310  in the upper and lower housing portions  304   a,    304   b.  When the platform  314  is secured between the upper and lower housing portions  304   a,    304   b,  the recesses  310  of the upper and lower housing portions  304   a,    304   b  and the recesses  316  of the platform  314  define upper and lower cavities  318  ( FIG. 7 ) at the distal portion of the housing  304  that diverge outwardly in the distal direction. 
     The adapter assembly  300  includes the pivot base  302 , a drive assembly  320 , a lead screw  322 , a firing nut  324 , and an inner tube  326 . The pivot base  302  defines a longitudinal slot  302   a  and the lead screw  322  includes a threaded outer wall  322   a.  The drive assembly  320  is positioned within the housing  304  ( FIG. 9 ) and includes a distal working end  328 , a proximal connector  330 , and an elongate flexible body  332  positioned between the working end  328  and the connector  330 . The flexible body  332  includes an upper body portion  332   a  and a lower body portion  332   b.  The working end  328  includes an upper beam  336 , a lower beam  338 , and a vertical strut  340 . The vertical strut  340  includes a knife edge  342 . When the drive assembly  320  is in a retracted position, the vertical strut  340  is positioned within the longitudinal slot  302   a  of the pivot base  302 . The upper and lower beams  336 ,  338  are positioned to engage the anvil assembly  210  and the cartridge channel member  212  to move the anvil assembly  210  and the cartridge channel member  212  between open and clamped positions as is known in the art. For a more detailed description of the working end  328  of the drive assembly  320 , see U.S. Pat. No. 5,865,361 (“&#39;361 Patent”) which is incorporated herein by reference in its entirety. 
     Referring briefly to  FIG. 15 , the connector  330  extends proximally from the flexible body  332  of the drive assembly  320  and includes a distal portion  346  and a proximal portion  348 . The distal portion  346  of the connector  330  is secured to a proximal end of the flexible body  332  between the upper body portion  332   a  and a lower body portion  332   b  of the flexible body  332 . The proximal portion  348  of the connector  330  includes an annular recess  350  ( FIG. 10 ) and is configured to be received within a distal end of the firing nut  324 . Pins  352  extend through a distal portion of the firing nut  324  through the annular recess  350  of the connector  330  to secure the distal portion of the firing nut  324  to the connector  330 . The annular recess  350  has a length that is greater than the diameter of the pins  352  such that the connector  330  is axially movable within the firing nut  324  independently of the firing nut  324 . More specifically, the connector  330  is axially movable in relation to the firing nut  324  between an advanced position ( FIG. 10 ) in which the pins  352  engage a proximal wall  350   a  defining the proximal end of the annular recess  350  and a retracted position ( FIG. 16 ) in which the pins  352  engage a distal wall  350   b  defining the distal end of the annular recess  350 . The connector  330  translates movement of the firing nut  324  into movement of the drive assembly  320  when the pins  352  are engaged with the walls  350   a  and  350   b  defining the annular recess  350 . 
     Referring again to  FIGS. 4-10 , the firing nut  324  includes an inner wall having a threaded portion  356  ( FIG. 9 ) and an outer side wall defining a flat  358  ( FIG. 5 ). The threaded portion  356  is positioned to engage the threaded outer wall  322   a  of the lead screw  322  such that rotation of the lead screw  322  within the firing nut  324  causes longitudinal movement of the firing nut  324  within the housing  304  ( FIG. 9 ). The inner tube  326  includes an inner wall having a flat surface portion (not shown) that defines an axial bore  360  ( FIG. 5 ). The flat surface portion of the inner wall of the inner tube  326  is positioned to engage the flat  358  ( FIG. 5 ) on the outer side wall of the firing nut  324  to prevent rotation of the firing nut  324  within the inner tube  326  of the adapter assembly  300 . The inner tube  326  also has an outer wall that defines a flat  362 . The flat  362  of the inner tube  326  is positioned within the housing  304  to prevent rotation of the inner tube  326  within the housing  304 . 
     In use, when the lead screw  322  is rotated within the firing nut  324 , engagement between the threaded outer wall  322   a  of the lead screw  322  and the threaded portion  356  (FIG.  9 ) of the inner wall of the firing nut  324  causes axial movement of the firing nut  324  within the inner tube  326  of the adapter assembly  300 . As discussed above, engagement between the flat  358  of the firing nut  324  and the flat surface portion (not shown) on the inner wall of the inner tube  326  prevents the firing nut  324  from rotating and, thus, limits the firing nut  324  to axial movement within the inner tube  326  of the adapter assembly  300 . As the firing nut  324  is moved axially within the inner tube  326 , the pins  352  are moved within the annular recess  350  of the connector  330  until the pins  352  engage one of the ends  350   a,    350   b  of the wall defining the annular recess  350 . When this occurs, axial movement of the firing nut  324  will cause axial movement of the connector  330  and corresponding axial movement of the drive assembly  320 . Axial movement of the drive assembly  320  causes the working end  328  of the drive assembly  320  to move within the tool assembly  200  to actuate the tool assembly  200  as is known in the art. 
     As discussed above, the platform  314  ( FIG. 5 ) is secured between a distal portion of the upper and lower housing portions  304   a,    304   b  and defines upper and lower cavities  318  ( FIG. 7 ) (only the upper cavity is shown). A distal end of the platform  318  includes a flange  364  ( FIG. 5 ) that extends distally from the housing  304  of the adapter  300 . The flange  364  defines a bore  366 . 
     Referring to  FIGS. 6A and 6B , the pivot base  302  includes a body  370  ( FIG. 5 ) having a distal portion  372  that defines the longitudinal slot  302   a  and a proximal portion  374 . The distal portion  372  of the body  370  is dimensioned to be received in the channel  262  ( FIG. 4 ) defined in the proximal portion  250  ( FIG. 2 ) of the mounting member  216  and defines spaced keyway slots  376 . Each of the keyway slots  376  is dimensioned to receive one of the locking tabs  264  ( FIG. 4 ) of the mounting member  216  when the tool assembly  200  is secured to the adapter assembly  300 . 
     The keyway slots  376  are substantially J-shaped and have an axial portion  378  and a transverse portion  380 . 
     The proximal portion  374  of the body  370  of the pivot base  302  has a radiused proximal end  382  and defines a transverse through slot  384  and a vertical opening  386  ( FIG. 6B ). The slot  384  receives the flange  364  ( FIG. 5 ) of the platform  314 . A pivot member  388  is received through the opening  386  in the proximal portion  374  of the pivot base  302  and the vertical bore  366  in the flange  364  of the platform  314  to pivotably secure the pivot base  302  to the platform  314 . In embodiments, top and bottom surfaces of the proximal portion  374  of the body  370  of the pivot base  302  define annular guide channels  390  ( FIG. 6B ). 
     Referring to  FIGS. 5 and 7-8 , the adapter  300  ( FIG. 1 ) includes upper and lower drive assembly guides  392 . Each of the guides  392  ( FIG. 7A ) is substantially U-shaped and includes side walls  394 , a base wall  396 , and an open end  398  opposite to the base wall  396  that define a channel  392   a  that has a divergent distal portion  393 . The open end  398  of the guides  392  is dimensioned to receive one of the upper and lower body portions  332   a,    332   b  of the flexible body  332  of the drive assembly  320 . The base wall  396  defines spaced elongated slots  400  ( FIG. 5 ) and includes a proximal circular pivot member  402 . The pivot member  402  is received within an opening  404  ( FIG. 5 ) that is formed in a proximal end of the platform  314  to pivotably secure each of the drive assembly guides  392  within one of the cavities  318  of the platform  314  ( FIG. 6 ) in the distal end of the housing  304 . 
     The adapter  300  also includes an upper and a lower blow out plate assemblies  406 . Each of the upper and lower blow-out plate assemblies  406  includes a pair of blow-out plates  408  and a support block  410 . One blow-out plate  408  is positioned on each side of the upper body portion  332   a  of the flexible body  332  within a respective one of the channels  392   a  of the drive assembly guides  392 . In addition, one blow-out plate  408  is positioned on each side of the lower body portion  332   b  of the flexible body  332  within a respective one of the channels  392   a  of the drive assembly guides  392 . Each of the blow-out plates  408  includes a distal end having a transverse portion  412  ( FIG. 8 ) and a central vertical extension  414  ( FIG. 5 ). The transverse portion  412  ( FIG. 8 ) is received within a slot  416  ( FIG. 8 ) formed in the pivot base  302  distally of the pivot member  388  to axially fix the distal ends of the blow-out plates  408  to the pivot base  302 . The vertical extensions  414  of the blow-out plates  408  are each received within one of the spaced elongated slots  400  formed in the guides  392  to properly position the blow-out plates  408  about the flexible body  332  of the drive assembly  320 . Proximal ends of the blow-out plates  408  are free to move axially along the flexible body  332  when the tool assembly  200  is articulated in relation to the adapter assembly  300  to prevent binding of the flexible body  332  when the tool assembly  200  is articulated. 
     The blow-out plate assemblies  406  are positioned on opposite sides of the flexible body  332  of the drive assembly  320  and extend from a position proximal of the pivot axis of the tool assembly  200  defined by the pivot member  388  ( FIG. 5 ) to stabilize the flexible body  332  of the drive assembly  320  and minimize the likelihood of outward buckling of the flexible body  332  of the drive assembly  320  during approximation and firing of the stapling device  10  ( FIG. 1 ). 
     Referring to  FIGS. 5-9 , the adapter assembly  300  includes an articulation assembly  420  including an articulation drive member  422 , a first articulation link  424 , and a second articulation link  426 . The articulation drive member  422  is supported on the housing  304  and is movable between a retracted position and an advanced position. The articulation drive member  422  includes a distal end  430  that is coupled to a proximal end of the first articulation link  424 . In embodiments, the distal end of the articulation drive member  422  defines a slot  432  and the proximal end of the first articulation link  424  includes a rib  434  that is received in the slot  432  to couple the articulation drive member  422  to the first articulation link  424 . Alternately, other coupling mechanisms may be used to secure the articulation drive member  422  to the first articulation link  424 . In embodiments, the distal end of the first articulation link  424  is coupled to a proximal end of the second articulation link  426  by a pivot pin  428  ( FIG. 7 ) and the distal end of the second articulation link  426  is pivotably secured to the pivot base  302  by a pivot pin  430  ( FIG. 7 ). The pivot pin  430  is laterally offset from the pivot axis of the tool assembly  200  defined by the pivot member  388 . 
     In use, axial movement of the articulation drive member  422  within the housing  304  causes corresponding movement of the first and second articulation links  424 ,  426 , respectively. As the second articulation link  426  moves axially, the tool assembly  200  is articulated about the pivot axis defined by the pivot member  388  from a position in which a longitudinal axis of the tool assembly  200  is aligned with a longitudinal axis of the adapter assembly  300  to a position in which the longitudinal axis of the loading unit defines an acute angle with the longitudinal axis of the adapter assembly  300 . By providing two pivotally coupled articulation links  424 ,  426 , a greater range of articulation of the tool assembly  200  can be achieved. 
     Referring to  FIGS. 9 and 10 , the proximal connector  330  of the drive assembly  320  defines channels  500  that are closed by a radial flange  501  that extends transversely across a proximal end of the channels  500 . The channels  500  receive the upper and lower body portions  332   a,    332   b  of the flexible body  332  of the drive assembly  320 . The radial flange  501  is positioned to engage a biasing member  502  that is supported between a distal end of the firing nut  324  and a proximal surface of the radial flange  500 . The biasing member  502  is positioned to urge the drive assembly  320  in relation to the firing nut  324  towards an advanced position (FIG.  10 ). In the advanced position, the pins  352  supported on the distal end of the firing nut  324  engage the proximal wall  350   a  of the annular recess  350  in the connector  330 . In embodiments, the biasing member  502  is a coil spring and the distal end of the firing nut  324  defines an annular recess  504  that receives the coil spring  502  to align the coil spring  502  with the flange  500  of the connector  330 . 
       FIGS. 11-21  illustrate the stapling device  10  as the tool assembly  200  is releasably coupled to the distal portion of the adapter assembly  300 . Referring initially to  FIGS. 11-13 , in order to attach the tool assembly  200  to the adapter assembly  300 , a proximal end of the tool assembly  200  is moved towards the distal end of the adapter assembly  300  in the direction indicated by arrows “A” in  FIGS. 11 and 13  to position the distal portion  372  of the body  370  of the pivot base  302  and the working end  328  of the drive assembly  320  positioned in the longitudinal slot  380  of the pivot base  302  into the channel  262  ( FIG. 4 ) of the mounting member  216  of the tool assembly  200 . When the distal portion  372  of the pivot base  302  is received within the channel  262  of the mounting member  216 , the locking tabs  264  of the mounting member are received within the axial portion  378  of the keyway slots  376 . When the locking tabs  264  are positioned within the axial portion  378  of the keyway slots  376 , the vertical strut  340  of the working end  328  of the drive assembly  320  is misaligned with the slot  255  ( FIG. 2A ) in the distal end of the mounting member  216  and with the knife slot  243  ( FIG. 17 ) in the channel member  212 . As such, the working end  328  of the drive assembly  320  presses against the proximal end of the channel member  212 . Thus, as the pivot base  302  is advanced into the channel  262  of the mounting member  216 , the drive assembly  320  is urged from its advanced position ( FIG. 10 ) towards its retracted position ( FIG. 16 ) and the biasing member  502  is compressed. 
     Referring to  FIGS. 14-18 , as the locking tabs  264  of the mounting member  216  are moved through the axial portion  378  of the keyway slots  376  in the direction indicated by arrows “A” in  FIG. 14 , the drive assembly  320  is pressed rearward by the channel member  212  to move the drive assembly  320  including the connector  330  proximally in relation to the firing nut  324  in the direction indicated by arrow “B” in  FIG. 16  from its advanced position ( FIG. 10 ) to its retracted position ( FIG. 16 ). As shown in  FIG. 16 , in the retracted position of the drive assembly  320 , the pins  352  on the distal end of the firing nut  324  are engaged with the distal wall  350   b  defining the annular recess  350  of the proximal connector  330  ( FIG. 16 ) and the locking tabs  264  are positioned in the distal ends of the axial portion  378  of the keyway slots  376 . 
     Referring to  FIGS. 19-21 , in order to secure the tool assembly  200  to the pivot base  302  of the adapter assembly  300 , the tool assembly  200  is rotated in relation to the adapter assembly  300  in the direction indicated by arrows “C” to move the locking tabs  264  in the direction indicated by arrow “D” in  FIG. 19  into and through the transverse portion  380  of the keyway slots  376 . As the tool assembly  200  is rotated in relation to the adapter assembly  300 , the working end  328  of the drive assembly  320  moves into alignment with the slot  255  ( FIG. 2A ) in the distal end of the mounting member  216  and with the knife slot  243  in the channel member  212 . Once the working end  328  of the of the drive assembly  320  is aligned with the slot  255  ( FIG. 2A ) in the distal end of the mounting member  216  and with the knife slot  243  in the channel member  212 , the biasing member  502  urges the drive assembly  320  back to the advanced position in the direction indicated by arrows “E” in  FIG. 19  to move the working end  328  of the drive assembly  320  into the knife slot  243  of the channel member  212 . In this position, the tool assembly  200  is secured to the adapter assembly  300 , and the stapling device  10  is ready for use. For a detailed description of the operation of a stapling device, see the &#39;361 Patent. 
     In the presently described stapling device  10 , the tool assembly  200  forms a loading unit that does not include an articulation assembly or a drive assembly that must be coupled to the different mechanisms in the adapter assembly to operate. As such, drawbacks associated with known loading units or reloads are minimized to provide a more reliable tool assembly. 
     Persons skilled in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments. It is envisioned that the elements and features illustrated or described in connection with one exemplary embodiment may be combined with the elements and features of another without departing from the scope of the present disclosure. As well, one skilled in the art will appreciate further features and advantages of the disclosure based on the above-described embodiments. Accordingly, the disclosure is not to be limited by what has been particularly shown and described, except as indicated by the appended claims.