Patent Publication Number: US-2022225995-A1

Title: Surgical stapler with powered and manual functions

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63/140,066, filed Jan. 21, 2021, the entire contents each of which is incorporated by reference herein. 
    
    
     FIELD 
     This disclosure is generally related to surgical stapling devices and, more particularly, to surgical stapling devices for performing anastomoses procedures. 
     BACKGROUND 
     Circular stapling devices are used to perform a variety of anastomoses procedures in which two tubular anatomical tissues structures are joined together. These procedures include colorectal circular anastomosis, esophageal circular anastomosis, and bariatric circular anastomosis. Typically, a circular stapling device includes an adapter assembly that connects a tool assembly to a handle assembly. The tool assembly includes an anvil assembly and a shell assembly that are movable in relation to each other in response actuation of an approximation mechanism to clamp tissue between the anvil and shell assemblies. The shell assembly includes a staple cartridge, a staple pusher, and an annular knife. The staple cartridge supports one or more annular rows of staples, and the staple pusher is movable within the staple cartridge in response to actuation of a firing mechanism to eject the staples from the staple cartridge into the anvil assembly. The annular knife is positioned radially inward of the annular rows of staples and is movable from a retracted position to an advanced position to cut or core tissue against the anvil assembly. 
     Circular stapling devices are available in manual and powered configurations. Typically, the powered configurations include one or more motors located in the handle assembly that drive the approximation and firing mechanisms to actuate the stapling device, and the manual configurations include a rotation knob to actuate the approximation mechanism and a firing trigger to actuate the firing mechanism. Both device configurations have advantages. Due to higher costs of the components, powered stapling devices (or portions thereof) are configured to be reusable, whereas due to the lower costs, manual stapling devices are configured to be disposable. Reusable stapling devices must be properly sterilized. 
     A continuing need exists for a circular stapling device that has the advantages of both the powered and manual stapling device configurations and is disposable. 
     SUMMARY 
     This disclosure generally relates to a surgical stapling device for performing anastomoses procedures within a body of a patient. The surgical stapling device includes a handle assembly that includes a manually actuated approximation mechanism and a motorized firing mechanism. 
     Aspects of the disclosure are directed to a surgical stapling device that includes a handle assembly, an elongate body, an anvil retainer, and a tool assembly. The elongate body has a distal portion and a proximal portion. The anvil retainer extends from the distal portion of the elongate body. The tool assembly is supported on the distal portion of the elongate body and includes an anvil assembly and a shell assembly. The anvil assembly has an annular staple forming surface and the shell assembly has an annular staple cartridge. The anvil assembly is coupled to the anvil retainer and is movable with the anvil retainer to move the tool assembly between an open position in which the annular staple forming surface of the anvil assembly is spaced from the annular staple cartridge of the shell assembly and a clamped position in which annular staple forming surface of the anvil assembly is in juxtaposed opposition to the annular staple cartridge of the shell assembly. The shell assembly further includes a staple pusher and an annular knife that are movable in relation to the annular staple cartridge between retracted and advanced positions to eject staples from the annular staple cartridge and cut tissue. The handle assembly includes a body portion, a manually operated approximation mechanism, and a motorized firing mechanism. The approximation mechanism is coupled to the anvil retainer and is manually operable to retract the anvil retainer into the shell assembly to move the tool assembly from the open position to the clamped position. The firing mechanism includes a motor that is activated to move the staple pusher and the annular knife between their retracted and advanced positions. 
     In aspects of the disclosure, the body portion of the handle assembly supports a battery pack that includes one or more batteries that are electrically coupled to the motor by circuitry. 
     In some aspects of the disclosure, the manually operated approximation mechanism includes a rotation knob, a rotatable sleeve, a drive screw, and a screw extension. 
     In certain aspects of the disclosure, the rotatable knob is coupled to the drive screw by the rotatable sleeve such that rotation of the rotation knob causes longitudinal movement of the drive screw between advanced and retracted positions. 
     In aspects of the disclosure, the drive screw is coupled to the anvil retainer by one or more extensions that are formed of a resilient material and extend through the elongate body. 
     In some aspects of the disclosure, the handle assembly supports a photo interrupter, and the drive screw supports a carriage that has an elongate rib. The carriage is fixedly secured to the drive screw and movable with the drive screw between advanced and retracted positions such that the elongate rib is received within the photo interrupter when the carriage and the drive screw are near their retracted positions. 
     In certain aspects of the disclosure, the handle assembly includes at least one safety switch that is supported within the body portion of the handle assembly and at least one safety button that is supported on the body portion of the handle assembly. 
     In aspects of the disclosure, the at least one safety switch is activated when the elongate rib of the carriage is received within the photo interrupter. 
     In some aspects of the disclosure, the handle assembly includes a fire switch and a fire button. The fire switch is supported within the body portion of the handle assembly and the fire button is supported on the body portion of the handle assembly. 
     In certain aspects of the disclosure, the fire switch is activated when the at least one safety button is depressed to close the at least one safety switch after the safety switch is activated, and the fire button is depressible to close the fire switch after the fire switch is activated to activate the motor. 
     In aspects of the disclosure, the at least one safety switch includes first and second safety switches and the at least one safety button includes first and second safety buttons. 
     In some aspects of the disclosure, the first and second safety buttons are supported on opposite sides of the body portion of the handle assembly. 
     In certain aspects of the disclosure, the safety button illuminates when the safety switch is activated, and the fire button illuminates when the fire switch is activated. 
     In aspects of the disclosure, the motorized firing mechanism includes a fire gear, a fire screw, an extender, a pusher link, and a pusher, and the motor includes a drive shaft that supports an output gear. 
     In some aspects of the disclosure, the fire gear includes an outer gear member that is engaged with the output gear such that activation of the motor causes rotation of the fire gear. 
     In certain aspects of the disclosure, the fire gear defines an internally threaded bore and the fire screw includes an outer threaded portion. The fire screw is received within the internally threaded bore of the of the fire gear such that rotation of the fire gear causes longitudinal movement of the fire screw between retracted and advanced positions. 
     In aspects of the disclosure, the fire screw is coupled to the pusher link by the extender and the pusher link is coupled to the pusher such that longitudinal movement of the fire screw causes corresponding longitudinal movement of the pusher link and the pusher. 
     In some aspects of the disclosure, the approximation knob defines a through bore and has a proximal portion that supports an indicator cap that defines at least one window. 
     In certain aspects of the disclosure, the stapling device includes an indicator mechanism that includes an indicator, an adjustment member, and a biasing member. 
     In aspects of the disclosure, the indicator includes indicia and is movable within the through bore of the approximation knob from an advanced position to a retracted position in response to movement of the drive screw from its&#39; advanced position towards its retracted position to position the indicia in a position within the approximation knob to be visualized through the at least one window in the indicator cap. 
     In some aspects of the disclosure, the adjustment member is threadedly engaged with the indicator and includes a distal portion that extends distally of the indicator and is positioned to engage the drive screw as the drive screw is moved towards its retracted position to move the indicator towards its&#39; retracted position. 
     In certain aspects of the disclosure, a longitudinal position of the adjustment member in relation to the indicator is adjustable to properly position the adjustment member in relation to the drive screw within the through bore of the approximation knob such that the indicia moves into the at least one window of the indicator cap when the tool assembly is in the clamped position. 
     Another aspect of the disclosure is directed to a handle assembly that includes a body portion, a manually operated approximation mechanism, and a motorized firing mechanism. The approximation mechanism includes an approximation knob and a drive screw. The approximation knob is rotatable to cause longitudinal movement of the drive screw. The firing mechanism includes a motor and a fire screw. The motor is coupled to the fire screw such that activation of the motor causes longitudinal movement of the drive screw. 
     In aspects of the disclosure, the motorized firing mechanism further includes a fire gear, and the motor includes an output shaft that supports an output gear. The fire gear includes an outer gear member that is engaged with the output gear such that activation of the motor causes rotation of the fire gear. 
     In some aspects of the disclosure, the fire gear defines an internally threaded bore and the fire screw includes an outer threaded portion. The fire screw is received within the internally threaded bore of the fire gear such that rotation of the fire gear causes longitudinal movement of the fire screw between retracted and advanced positions. 
     Another aspect of the disclosure is directed to an approximation knob assembly including an approximation knob, an indicator cap, and an indicator mechanism. The approximation knob defines a through bore and has a proximal portion. The indicator cap is supported on the proximal portion of the approximation knob and defines at least one window. The indicator mechanism includes an indicator, an adjustment member, and a biasing member. The indicator includes indicia and is movable within the through bore of the approximation knob from an advanced position to a retracted position to position the indicia in a position within the approximation knob to be visualized through the at least one window in the indicator cap. The adjustment member is threadedly engaged with the indicator and includes a distal portion that extends distally from the indicator. The longitudinal position of the adjustment member is adjustable in relation to the indicator. 
     Other aspects, features, and advantages will be apparent from the description, the drawings, and the claims that follow. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Various aspects and features of the disclosure are described with reference to the drawings wherein like numerals designate identical or corresponding elements in each of the several views wherein: 
         FIG. 1  is a side perspective view of a circular stapling device according to aspects of the disclosure with a tool assembly in an unclamped position; 
         FIG. 2  is a side perspective view of the circular stapling device shown in  FIG. 1  with an anvil assembly and a battery pack separated from the stapling device; 
         FIG. 3  is an exploded side perspective view of the battery pack of the stapling device shown in  FIG. 2 ; 
         FIG. 4  is a side perspective view from above of the handle assembly shown in  FIG. 1  assembled with a body half-section of the handle assembly removed; 
         FIG. 5  is a side perspective view from below of the handle assembly shown in  FIG. 4  assembled with a body half-section of the handle assembly removed; 
         FIG. 6  is an exploded side perspective view of the handle assembly of the stapling device shown in  FIG. 1 ; 
         FIG. 7  is a side perspective view of the circular stapling device shown in  FIG. 1  in the unclamped position with an outer tube of the adapter assembly and the body of the handle assembly shown in phantom; 
         FIG. 8  is an enlarged view of the indicated area of detail shown in  FIG. 7 ; 
         FIG. 9  is an exploded side perspective view of approximation and firing mechanisms of the handle assembly shown in  FIG. 1 ; 
         FIG. 10  is a cross-sectional view taken along a longitudinal axis of the circular stapling device shown in  FIG. 1  in the unclamped position; 
         FIG. 11  is an enlarged view of the indicated area of detail shown in  FIG. 10 ; 
         FIG. 12  is an enlarged view of the indicated area of detail shown in  FIG. 9 ; 
         FIG. 13  is a cross-sectional view taken along section line  11 - 11  of  FIG. 12 ; 
         FIG. 14  is a cross-sectional view taken along section line  14 - 14  of  FIG. 5 ; 
         FIG. 15  is a cross-sectional view taken along section line  15 - 15  of  FIG. 5 ; 
         FIG. 16  is a cross-sectional view taken along section line  16 - 16  of  FIG. 5 ; 
         FIG. 17  is a cross-sectional view taken along section line  17 - 17  of  FIG. 5 ; 
         FIG. 18  is a cross-sectional view taken along section line  18 - 18  of  FIG. 5 ; 
         FIG. 19  is a cross-sectional view taken along the longitudinal axis of the circular stapling device shown in  FIG. 1  in the clamped position; 
         FIG. 20  is an enlarged view of the indicated area of detail shown in  FIG. 19 ; 
         FIG. 21  is a cross-sectional view taken along section line  21 - 21  of  FIG. 20 ; 
         FIG. 22  is a side cross-sectional view taken through a distal portion of the handle assembly as the circular stapling device is being fired; and 
         FIG. 23  is a cross-sectional view taken along section line  23 - 23  of  FIG. 22 . 
     
    
    
     DETAILED DESCRIPTION 
     The disclosed surgical stapling device 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 aspects 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 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 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 during use of the device for its intended purpose, while the term “distal” is used generally to refer to that portion of the device that is farther from the clinician during use of the device for its intended purpose. In addition, the terms “about” and “substantially” are intended to include a range that includes the listed parameter and plus or minus ten percent of the listed parameter. Further, the term “clinician” is used generally to refer to medical personnel including doctors, nurses, and support personnel. 
     This disclosure is directed to a surgical stapling device for performing anastomoses procedures that includes a motor for driving a firing mechanism and a manually actuated approximation knob for approximating a tool assembly of the stapling device. 
       FIGS. 1 and 2  illustrate a circular stapling device shown generally as stapling device  10  which includes a handle assembly  12 , an elongate body  14 , and a tool assembly  16 . The tool assembly  16  includes an anvil assembly  18  that has an annular staple forming surface  18   a  ( FIG. 7 ) and a shell assembly  20  that has an annular staple cartridge  20   a  ( FIG. 1 ) that supports staples (not shown). The anvil assembly  18  is supported for movement in relation to the shell assembly  20  between an open or unclamped position ( FIG. 1 ) and a clamped position ( FIG. 19 ). In aspects of the disclosure, the shell assembly  20  includes a proximal portion  22  that is coupled to a distal portion of the elongate body  14  and the adapter assembly  20  includes a proximal portion that is coupled to the handle assembly  12 . It is envisioned that the shell assembly  20  can be releasably secured to the elongate body  14  and/or the elongate body  14  can be releasably secured to the handle assembly  12 . The shell assembly also includes a knife  23  ( FIG. 1 ) that is movable between retracted and advanced positions to cut tissue during an anastomosis procedure. 
     The circular stapling device  10  includes a hybrid type handle assembly  12  that includes a manually operated approximation knob  74  for approximating the anvil assembly  18  with the shell assembly  20  and a fire button  24  for activating a motor  26  ( FIG. 4 ) for stapling and cutting tissue. The handle assembly  12  includes a body portion  28  that is ergonomically shaped to be gripped by a clinician. The body portion  28  defines an internal cavity  30  ( FIG. 4 ) and an external recess  32  ( FIG. 2 ). The internal cavity  30  receives drive components of the handle assembly described below. The external recess  32  receives a battery pack  34  that is releasably coupled to the body portion  28  of the handle assembly  12 . The battery pack  34  includes a housing  36  and one or more batteries  38  that are received within the housing  36 . The housing  36  of the battery pack  34  has a distal portion that is formed with a resilient latch  40  that is received in a slot  42  ( FIG. 2 ) formed in the body portion  28 . The resilient latch  40  engages the body portion  28  in a snap-fit manner to releasably secure the battery pack  34  to the body portion  28  of the handle assembly  12 . 
       FIG. 3  illustrates the battery pack  34  of the handle assembly  12 . In aspects of the disclosure, the housing  36  of the battery pack  34  is formed from half-sections  36   a ,  36   b  that are coupled together to define a cavity  46  that receives the batteries  38 . The batteries  38  are supported on a printed circuit board  48  that includes electrical contacts  50 . The half-sections  36   a ,  36   b  when coupled together define an opening  52  that receives the electrical contact  50  such that the electrical contact  50  can engage contacts within the handle assembly  12  to supply power to the motor  26 . The battery contacts may be in the form of spring fingers  54 . 
       FIGS. 4-6  illustrate the internal cavity  30  of the body portion  28  of the handle assembly  12  and the components received in the cavity  30 . The handle assembly  12  includes a printed circuit board  58  that divides the internal cavity  30  into an upper half  30   a  and a lower half  30   b  as viewed in  FIG. 4 . The printed circuit board  58  is secured between half-sections  28   a ,  28   b  ( FIG. 6 ) of the body portion  28  of the handle assembly  12  and supports the motor  26  within the upper half  30   a  of the cavity  30  distally of the battery pack  34 . The motor  26  includes a rotating drive shaft  59  ( FIG. 6 ) that supports an output gear  60  ( FIG. 15 ) that is aligned with a cutout  62  defined in the printed circuit board  58 . Rotation of the drive shaft  59  causes corresponding rotation of the output gear  60 . 
     The printed circuit board  58  includes a distal portion and a proximal portion. The proximal portion of the printed circuit board  58  supports the battery contacts  54  and the distal portion of the  58  supports safety switches  64 . The safety switches  64  are positioned to be activated by safety buttons  66  that are positioned on opposite sides of the body portion  28  of the handle assembly  12  as described in further detail below. The distal portion of the  58  also supports a fire switch  68  that is positioned to be activated by the fire button  24 . Although not shown, the  58  can also support circuitry to electrically couple the battery pack  34  and motor  26  to the switches  64  and  68  and include a micro controller and motor driver circuitry. The lower half  30   b  of the cavity  30  receives a proximal portion of an approximation mechanism  72  and a proximal portion of a firing mechanism  73 . 
       FIGS. 5-11  illustrate the approximation mechanism  72  which includes the approximation knob  74 , a anvil clamp screw  76 , a rotatable sleeve  78 , first and second screw resilient extensions  80 ,  82  ( FIG. 10 ), and an anvil retainer trocar  84  ( FIG. 7 ). The rotatable sleeve  78  includes a cylindrical hollow body portion  86  and a cylindrical collar  88  supported on a distal portion of the hollow body portion  86 . The rotatable sleeve  78  defines a longitudinal through bore  90 . ( FIG. 9 ) The collar  88  has a diameter greater than the body portion  86  and is received between inwardly extending flanges  92  ( FIG. 5 ) formed on inner walls of the half-sections  28   a ,  28   b  of the body portion  28  of the handle assembly  12 . Receipt of collar  88  between the flanges  92  axially fixes the rotatable sleeve  78  within the body portion  28  of the handle assembly  12  while permitting rotation of rotatable sleeve  78 . A proximal portion of the rotatable sleeve  78  extends through an opening  94  ( FIG. 6 ) in the proximal end of the body portion  28  of the handle assembly  12  and is fixedly coupled to the approximation knob  72 . The hollow body portion  86  of the rotatable sleeve  78  includes a pair of diametrically opposed ribs  96  ( FIG. 9 ) that are formed on the outer surface of the body portion  76  and are received within slots (not shown) defined within the rotation knob  74  to rotatably fix the rotatable sleeve  78  to the approximation knob  74  such that rotation of the approximation knob  72  causes concurrent rotation of rotatable sleeve  78 . In aspects of the disclosure, the distal portion of the approximation knob  74  defines an annular channel  74   a  that receives an internal rib  75  ( FIG. 11 ) formed on an inner wall of the body portion  28  of the handle assembly  12  to rotatably secure the approximation knob  74  to body portion  28  of the handle assembly  12 . 
     The proximal half of the anvil clamp screw  76  includes a helical channel  98  and is positioned within the through bore  90  of the rotatable sleeve  78 . A pin  100  ( FIG. 11 ) is supported on the collar  88  of the rotatable sleeve  78  ( FIG. 11 ) and extends radially from the collar  88  into helical channel  98 . Since the rotatable sleeve  78  is axially fixed with respect to body portion  28  of the handle assembly  12 , rotation of rotatable sleeve  78  about anvil clamp screw  76  causes pin  100  ( FIG. 11 ) to move along helical channel  98  of anvil clamp screw  76  to effect axial movement of anvil clamp screw  76  within the body portion  28  of the handle assembly  12 . 
     The anvil clamp screw  76  has a distal portion that defines a transverse slot  102  ( FIG. 9 ). The screw extensions  80 ,  82  each include a proximally located flexible flat band portion  104  ( FIG. 10 ) and a distally located flat band portion  106 . The band portions  104  are secured within the transverse slot  102  of the drive screw  76  with a pin  108  ( FIG. 9 ) to secure the band portions  80 ,  82  to the drive screw  76 . The band portions  80 ,  82  extend from the drive screw  76  through the elongated body  14  ( FIG. 10 ) into the shell assembly  20 . The flat band portions  106  of the screw extensions  80 ,  82  are secured within a slot  110  ( FIG. 10 ) defined in the anvil retainer  84  with pins  112  ( FIG. 10 ) to secure the anvil retainer  84  to the screw extensions  80 ,  82 . When the approximation knob  74  is rotated to move the anvil clamp screw  76  axially within the body portion  28  of the handle assembly  12 , the screw extensions  80 ,  82  are also moved axially within the elongate body  14  and the anvil retainer  84  is moved axially within the shell assembly  20  ( FIG. 10 ). It is envisioned that although pins are shown to secure the screw extensions  80 ,  82  to the drive screw  76  and the anvil retainer  84  ( FIG. 10 ), other techniques and/or attachment devices can be used to perform this function. 
     The anvil retainer  84  is configured to be releasably coupled to the anvil assembly  18  ( FIG. 10 ) such that rotation of the approximation knob  74  moves the anvil assembly  18  in relation to the shell assembly  20  between the open and clamped positions. U.S. Pat. No. 7,303,106 describes a stapling device including an anvil assembly and anvil retainer that are releasably coupled together and are suitable for use with the stapling device  10 . 
     The approximation knob  74  defines a through bore  114  and supports an indicator cap  116 . The indicator cap  116  is fixedly secured to a proximal portion of the approximation knob  74  and defines windows  118  that are spaced about the indicator cap  116 . The approximation knob  74  supports an indicator assembly  120  ( FIG. 9 ) that includes an indicator  122 , an adjustment member or screw  124 , and a biasing member  126 . The indicator  122  includes a cylindrical body  128  and a head portion  130  that has a diameter that is larger than the cylindrical body  128 . The head portion  130  of the indicator  122  is received within the indicator cap  116  and includes indicia  132  ( FIG. 9 ). The indicator  122  is movable within the approximation knob  74  from an advanced position towards a retracted position in response to movement of the drive screw  76  towards a retracted position to move the head portion  130  of the indicator  122  within the indicator cap  116  from an advanced position to a retracted position. The indicia  132  is visible through the windows  118  in the indicator cap  116  when the stapling device  10  is moved to a clamped position. As used herein, the term “clamped position” means positions in which the anvil assembly  18  located in close enough approximation with the staple cartridge  20   a  ( FIG. 1 ) of the shell assembly  20  such that staples can be properly formed against the anvil assembly  18 . As such, the clamped position includes a range of positions. The clamped position is determined by the thickness of tissue being clamped and the discretion of a clinician. 
     The adjustment screw  124  is threaded into a threaded bore  136  defined in the distal portion of the indicator  122  to secure the adjustment screw  124  to the indicator  122 . The adjustment screw  124  extends into the through bore  90  of the rotatable sleeve  78  and includes a distal end that is positioned to engage the drive screw  76  when the drive screw  76  is moved towards the retracted position. The biasing member  126  is positioned between the indicator cap  116  and the indicator  122  to urge the indicator  122  towards the advanced position. When the drive screw  76  moves towards its&#39; retracted position ( FIG. 20 ), the drive screw  76  engages the adjustment screw  124  to move the adjustment screw  124  and the indicator  122  proximally within the approximation knob  74 . As the indicator  122  moves within the approximation knob  74 , the head portion  130  of the indicator  122  moves within the indicator cap  116  such that the indicia  132  becomes visible through the windows  118  in the indicator cap  116 . This provides an indication to a clinician that the stapling device  10  ( FIG. 1 ) is in a fire-ready position, i.e., that the anvil assembly  18  and the shell assembly  20  are in close enough opposition to facilitate proper formation of staples. The position of the adjustment screw  124  within the through bore  90  of the rotatable sleeve  78  can be adjusted or calibrated by rotating the adjustment screw  124  during manufacturing of the stapling device  10  ( FIG. 1 ) to properly position the adjustment screw  124  within the through bore  90  of the rotatable sleeve  78  so that the indicia  132  moves into the windows  118  of the indicator cap  116  when the anvil assembly  18  and the shell assembly  20  are properly spaced from each other. 
     The drive screw  76  supports a carriage  140  ( FIG. 9 ) that is secured to the drive screw  76  with a carriage screw  142 . The carriage  140  is received in a threaded bore  144  in the drive screw  76  and is movable with the drive screw  76  as the drive screw  76  moves within the body portion  28  of the handle assembly  12  between retracted and advanced positions. The carriage  140  includes an elongate rib  146  ( FIG. 9 ) that engages or activates a switch, e.g., a photo interrupter  148  ( FIG. 17 ), supported within the handle assembly  12  when the stapling device  10  ( FIG. 1 ) is moved to the clamped position to activate the safety switches as described below. The carriage  140  also includes wings  140   a  ( FIG. 16 ) that are received in slots  141  defined within the body portion  28  of the handle assembly  12  to prevent rotation of the carriage  140  and guide the carriage  140  within the body portion  28  of the handle assembly  12  of the stapling device  10 . 
       FIGS. 5-13  illustrate the firing mechanism  73  ( FIG. 8 ) which includes a fire gear  150 , a fire screw  152 , an extender  154 , a pusher link  156  ( FIG. 10 ), and a pusher  158  ( FIG. 10 ). The fire gear  150  is rotatably supported about the drive screw  76  and defines an internal threaded bore  160  and an outer gear member  162  that includes a plurality of gear teeth  162   a . The gear member  162  is received between flanges  164  ( FIG. 13 ) formed on the body portion  28  of the handle assembly  12  such that the fire gear  150  can rotate within the body portion  28  of the handle assembly  12  but is axially fixed. The fire screw  152  is received within the internal threaded bore  160  of the fire gear  150  and includes an outer threaded portion  166  and an inner through bore  168 . The drive screw  76  extends through the through bore  168  of the fire screw  152  such that the fire screw  152  is slidable about the drive screw  76 . 
     The fire screw  152  includes a distal portion  152   a  that has a reduced diameter and is received within a proximal portion of the extender  154 . The distal portion  152   a  of the fire screw  152  includes diametrically opposed longitudinal slots  170  that are aligned with longitudinal slots  172  formed within the extender  154 . Pins  173  ( FIG. 14 ) are supported on the body portion  28  and extend through the slots  170  and  172  and into channels  175  ( FIG. 9 ) formed in the body portion  28  of the handle assembly  12  to prevent rotation of the extender  154  in relation to the fire screw  152 . The distal portion of the extender  154  receives a proximal portion of the pusher link  156  and the distal portion of the pusher link  156  is engaged with the pusher  158  which is received within the shell assembly  20  ( FIG. 10 ). In aspects of the disclosure, a thrust bearing  159  ( FIG. 23 ) is supported within the body portion  28  of the handle assembly  12  and is engaged with the proximal end of the fire gear  150  to absorb the firing forces generated by the fire gear  150 . 
     When the motor  26  is activated, the output gear  60  of the motor  26  is rotated. The output gear  60  is engaged with outer gear member  162  ( FIG. 15 ) of the fire gear  150  such that rotation of the output gear  60  rotates the fire gear  150 . The internal threaded bore  160  of the fire gear  150  is threadedly engaged with the outer threaded portion  166  of the fire screw  152 . As the fire gear  150  is rotated, the fire screw  152  is driven longitudinally within the fire gear  150  about the drive screw  76 . The distal portion  152   a  of the fire screw  152  is engaged with the proximal portion of the extender  154  and the distal portion of the extender  154  is engaged with the proximal portion of the pusher link  156  such that advancement of the fire screw  152  advances the pusher link  156  within the elongate body  14  of the stapling device  10  ( FIG. 10 ). The distal portion of the pusher link  156  is coupled to the pusher  158  such that advancement of the pusher link  156  causes the pusher  158  ( FIG. 10 ) to move within the shell assembly  20  to eject staples from the shell assembly  20 . 
       FIG. 6  illustrates the safety buttons  64 , the safety switches  66 , the fire button  24 , and the fire switch  68 . When the approximation knob  74  is manually actuated to move the stapling device  10  ( FIG. 1 ) to the clamped position in the fire-ready zone, the elongated rib  146  on the carriage  140  will move into the photo interrupter  148  ( FIG. 5 ) to interrupt a light beam. When this occurs, the photo interrupter  148 , which is connected by circuitry within the handle assembly  12  to the safety switches  66 , will cause the safety buttons  64  to illuminate to provide an indication to a clinician that the stapling device  10  is able to be fired. The safety buttons  64  can include an LED or other illuminating device to illuminate the safety buttons  64 . To fire the stapling device  10 , one of the safety buttons  64  must be pressed to close the safety switches  66  and activate the fire switch  68 . Once one of the safety buttons  64  is pressed, the fire button  24  can be pressed to close the fire switch  68  and initiate firing of the stapling device  10 , i.e., activate the motor  26  to advance the pusher link  156  and advance the pusher  158  to fire staples from the shell assembly  20 . The fire button  24  may also be illuminated such as a with a light emitting diode (LED). For example, when the safety buttons  64  are pressed, the fire button  24  will illuminate to provide an indication to a clinician that the stapling device  10  is ready to be fired. It is noted that the safety switches  66  will not activate the firing switch  68  until the elongated rib  146  on the carriage  140  moves into the photo interrupter  148 . 
     In aspects of the disclosure, the safety buttons  64  and the fire button  24  may be configured to blink when the stapling device  10  is coupled to the battery pack  34  prior to movement of the stapling device  10  to the clamped position. In this aspect of the disclosure, the safety buttons  64  will blink until the stapling device is moved to the clamped position. When the stapling device  10  is moved to the clamped position, the safety buttons  64  will illuminate continuously but the fire button  24  will continue to blink intermittently until one of the safety buttons  64  is depressed. When one of the safety buttons  64  is depressed to close the safety switch  66 , the fire button  24  will illuminate continuously to indicate to a clinician that the stapling device  10  is ready to fire. In aspects of the disclosure, the circuitry within the stapling device  10  includes a timer that resets the safety switches  66  if the stapling device  10  is not fired within a predetermined time after one of the safety buttons  64  is depressed. If the stapling device  10  is not fired in the predetermined time, the safety switches  66  will reset such that one of the safety buttons  64  will have to be depressed again to activate the fire button  24 . In aspects of the disclosure, the predetermined time can be from about 10 seconds to about 30 seconds although other times are envisioned. 
       FIGS. 19-21  illustrate the stapling device  10  as the stapling device  10  is moved from the open position to the clamped position. When the approximation knob  74  is rotated in the direction indicated by arrow “A” in  FIG. 20 , the drive screw  76  is retracted in the direction of arrow “B”. As summarized above, the drive screw  76  is coupled to the screw extensions  80 ,  82  and the screw extensions  80 ,  82  are coupled to the anvil retainer  84  such that movement of the drive shaft  76  in the direction of arrow “B” moves the anvil retainer in the direction of arrow “C” in  FIG. 19  to move the anvil assembly  18  in the direction of arrow “D” to the clamped and fire-ready position ( FIG. 19 ). As shown in  FIG. 21 , when the drive screw  76  is retracted and the stapling device  10  moves to the clamped position, the elongate rib  146  on the carriage  140  moves into the photo interrupter  148  to activate the safety switches  66 . When this occurs, the safety switches  66  will illuminate to provide an indication to a clinician that the stapling device  10  is ready to be fired. In this position, one of the safety buttons  64  can be depressed to activate the fire button  24 . When one of the safety buttons  64  is depressed, the fire button  24  will illuminate. 
       FIGS. 22 and 23  illustrate the stapling device  10  as the stapling device  10  is fired. When the firing button  24  is depressed to activate the firing switch  68 , the motor is activated to rotate the output gear  60 . When the output gear  60  is rotated, the output gear  60  rotates the fire gear  150 . The internal threaded bore  160  of the fire gear  150  is threadedly engaged with the outer threaded portion  166  of the fire screw  152 . As the fire gear  150  is rotated, the fire screw  152  is driven longitudinally within the fire gear  150  about the drive screw  76 . The distal portion  152  of the fire screw  152  is engaged with the proximal portion of the extender  154  and the distal portion of the extender  154  is engaged with the proximal portion of the pusher link  156  such that advancement of the fire screw  152  advances the pusher link  156  within the elongate body  14  of the stapling device  10  ( FIG. 10 ). The distal portion of the pusher link  156  is coupled to the pusher  158  such that advancement of the pusher link  156  causes the pusher  158  ( FIG. 10 ) to move within the shell assembly  20  to eject staples from the shell assembly  20 . The disclosed stapling device  10  incorporates benefits of manually operated stapling devices and powered stapling devices into a single instrument that can be manufactured as a disposable instrument. More particularly, the stapling device  10  includes a manually operated approximation mechanism  72  that preserves tactile feedback to the clinician for user-controlled compression. In addition, the stapling device  10  includes a powered or motorized firing mechanism  73  that allows for controlled stable firing with minimal influence on tissue movement. 
     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 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.