Abstract:
A surgical stapling and severing instrument particularly suited to endoscopic procedures incorporates a handle that produces separate closing and firing motions to actuate an end effector. In particular, the handle produces multiple firing strokes in order to reduce the required amount of force required to fire (i.e., staple and sever) the end effector. A linked transmission reduces the required handle longitudinal length, yet achieves a rigid, strong configuration when straightened for firing. A traction biased firing mechanism avoids binding in driving this straightened linked rack. The instrument further has a manually actuatable retraction system that does not require the use of additional springs or other mechanisms to generate retraction forces which must be overcome when generating the forces necessary to fire the device. In various embodiments, the retraction system provides a visual indication to the surgeon as to how far firing has progressed.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   The present application is related to commonly-owned U.S. patent application Ser. No. 11/729,013, to Chad P. Boudreaux and Christopher J. Schall, filed Mar. 28, 2007, entitled “Surgical Stapling and Cutting Instrument With Side Mounted Refraction Member”, the disclosure of which is hereby incorporated by reference in its entirety. 
   FIELD OF THE INVENTION 
   The present invention relates in general to endoscopic surgical instruments including, but not limited to, surgical stapler instruments that are capable of applying lines of staples to tissue while cutting the tissue between those staple lines and, more particularly, to improvements relating to surgical stapler instruments and improvements in processes for forming various components of such surgical stapler instruments that have manual retraction capabilities. 
   BACKGROUND OF THE INVENTION 
   Endoscopic surgical instruments are often preferred over traditional open surgical devices since a smaller incision tends to reduce the post-operative recovery time and complications. Consequently, significant development has gone into a range of endoscopic surgical instruments that are suitable for precise placement of a distal end effector at a desired surgical site through a cannula of a trocar. These distal end effectors engage the tissue in a number of ways to achieve a diagnostic or therapeutic effect (e.g., endocutter, grasper, cutter, staplers, clip applier, access device, drug/gene therapy delivery device, and energy device using ultrasound, RF, laser, etc.). 
   Known surgical staplers include an end effector that simultaneously makes a longitudinal incision in tissue and applies lines of staples on opposing sides of the incision. The end effector includes a pair of cooperating jaw members that, if the instrument is intended for endoscopic or laparoscopic applications, are capable of passing through a cannula passageway. One of the jaw members receives a staple cartridge having at least two laterally spaced rows of staples. The other jaw member defines an anvil having staple-forming pockets aligned with the rows of staples in the cartridge. The instrument commonly includes a plurality of reciprocating wedges which, when driven distally, pass through openings in the staple cartridge and engage drivers supporting the staples to effect the firing of the staples toward the anvil. 
   An example of a surgical stapler suitable for endoscopic applications is described in U.S. Pat. No. 5,465,895 to Brian D. Knodel, Richard P. Nuchols, and Warren P. Williamson, IV, which advantageously provides distinct closing and firing actions. Thereby, a clinician is able to close the jaw members upon tissue to position the tissue prior to firing. Once the clinician has determined that the jaw members are properly gripping tissue, the clinician can then fire the surgical stapler with a single firing stroke, thereby severing and stapling the tissue. The simultaneous severing and stapling avoids complications that may arise when performing such actions sequentially with different surgical tools that respectively only sever or staple. 
   One specific advantage of being able to close upon tissue before firing is that the clinician is able to verify via an endoscope that the desired location for the cut has been achieved, including that a sufficient amount of tissue has been captured between opposing jaws. Otherwise, opposing jaws may be drawn too close together, especially pinching at their distal ends, and thus not effectively forming closed staples in the severed tissue. At the other extreme, an excessive amount of clamped tissue may cause binding and an incomplete firing. 
   Generally, a single closing stroke followed by a single firing stroke is a convenient and efficient way to perform severing and stapling. However, in some instances, it would be desirable for multiple firing strokes to be required. For example, surgeons are able to select a length of staple cartridge for the desired length of cut from a range of jaw sizes. Longer staple cartridges require a longer firing stroke. Thus, to effect the firing, a hand-squeezed trigger is required to exert a larger force for these longer staple cartridges in order to sever more tissue and drive more staples as compared to a shorter staple cartridge. It would be desirable for the amount of force to be lower and comparable to shorter cartridges so as not to exceed the hand strength of some surgeons. In addition, some surgeons, not familiar with the larger staple cartridges, may become concerned that binding or other malfunction has occurred when an unexpectedly higher force is required. 
   One approach for lowering the required force for a firing stroke is a ratcheting mechanism that allows a firing trigger to be stroked multiple times, as described in U.S. Pat. Nos. 5,762,256 and 6,330,965, the disclosures of which are herein incorporated by reference. These known surgical stapling instruments with multiple-stroke firing mechanisms do not have the advantages of a separate closure and firing actions. 
   Other ratcheting surgical instruments are disclosed in commonly-owned U.S. Pat. No. 7,083,075, issued Aug. 1, 2006 to Jeffrey S. Swayze, Frederick E. Shelton, IV, Kevin Ross Doll, and Douglass B. Hoffman, entitled Multi-Stroke Mechanism With Automatic End of Stroke Retraction, which is hereby incorporated by reference. Various embodiments disclosed therein employ a handle that produces separate closing and firing motions to actuate an end effector. In particular, the handle is configured to generate the firing force necessary to staple and sever the tissue clamped within the end effector through multiple actuations of a firing trigger. The device may further employ a linked transmission which reduces the required handle length, yet achieves a rigid, strong configuration when straightened for firing. A traction biased firing mechanism avoids binding in driving this straightened linked rack in cooperation with an anti-backup mechanism, with a lockout mechanism that prevents releasing the closure trigger during firing. Furthermore, an external indicator gives feedback to the surgeon as to how far firing has progressed, as well as providing a manual retraction capability. These embodiments also generally employ a relatively strong spring to automatically retract the cutting member after the end effector has been fired. While such designs are extremely effective, the use of the retraction spring requires additional firing force to be generated to overcome the opposing spring force during firing. This problem can also be somewhat exacerbated when using articulating end effectors. In particular, when an articulating end effector is employed, a larger return spring must generally be employed to retract the articulating firing member. Use of such larger spring further increases the amount of firing forces that must be generated to overcome the spring force and fire the end effector components. 
   Consequently, a significant need exists for a surgical stapling instrument having a multiple stroke or other type of firing mechanism that is equipped with a manually actuatable retraction mechanism and does not employ an additional retraction means such as a spring or the like that generates forces that must be overcome during the firing stroke. 
   SUMMARY 
   In one aspect of the invention, there is provided a surgical instrument has a handle assembly and an end effector for performing a surgical operation. The end effector is operably coupled to the handle assembly and may operably support a firing member that is movable from a retracted position to a fired position in response to a longitudinal firing motion applied thereto. The instrument may also include a firing drive that is supported by the handle assembly and is configured to selectively generate the longitudinal firing motion upon actuation of a firing trigger operably coupled to the handle assembly. A retraction assembly may be supported by the handle assembly and interface with the firing drive such that manual actuation of the retraction assembly causes the firing drive to apply a sole retraction motion which is communicated to the firing member to cause the firing member to move from the fired position to the retracted position. 
   In another general aspect of various embodiments of the present invention there is provided a surgical instrument that has a handle assembly that is coupled to an end effector for performing a surgical operation. The end effector may operably support a firing member that is movable from a retracted position to a fired position in response to a longitudinal firing motion applied thereto. A linked rack may be operably supported by the handle assembly and a firing rod may communicate with the linked rack and the end effector for transmitting the firing and retraction motions from the linked rack to the end effector. A firing trigger may be operably supported by the handle assembly and may be configured to interface with the linked rack such that actuation of the firing trigger causes the linked rack to apply the firing motion to the firing rod. A first gear may be in meshing engagement with the linked rack and a retraction lever may be movably supported by the handle assembly and may be configured to interface with the first gear such that actuation of the retraction lever applies the sole retraction motion or force to the first gear which thereby transfers the sole retraction motion to the linked rack. 
   In still another general aspect of various embodiments of the present invention there is provided a surgical instrument that has a handle assembly that is coupled to an end effector. The end effector may operably support a firing member that is movable from a retracted position to a fired position in response to a longitudinal firing motion applied thereto. A first linked rack may be operably supported by the handle assembly. A firing rod may communicate with the linked rack and the end effector for transmitting the firing and retraction motions from the linked rack to the end effector. A firing trigger may be operably supported by the handle assembly and may be configured to selectively interface with the linked rack such that actuation of the firing trigger causes the linked rack to apply the firing motion to the firing rod. A second gear rack may be operably supported by the handle assembly. A drive gear may be in meshing engagement with the first linked rack and the second gear rack. A retraction lever may be movably coupled to the handle assembly and the second gear rack such that actuation of the retraction lever applies the sole retraction motion to the drive gear which thereby transfers the sole retraction motion to the linked rack. 
   These and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof. 

   
     BRIEF DESCRIPTION OF THE FIGURES 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention, and, together with the general description of the invention given above, and the detailed description of the embodiments given below, serve to explain various principles of the present invention. 
       FIG. 1  is a perspective view of a surgical stapling and severing instrument of various embodiments of the present invention. 
       FIG. 2  is a left side elevation view taken along line  2 - 2  in longitudinal cross section of an end effector at a distal portion of the surgical stapling instrument of  FIG. 1 . 
       FIG. 3  is a front perspective view of the end effector of  FIG. 2 . 
       FIG. 4  is a perspective, exploded view of an implement portion of the surgical stapling and severing instrument of  FIG. 1 . 
       FIG. 5  depicts a left side elevation view in section of the end effector of  FIG. 3  of the surgical instrument of  FIG. 1 , the section generally taken along lines  5 - 5  of  FIG. 3  to expose portions of a staple cartridge but also depicting the firing bar along the longitudinal centerline. 
       FIG. 6  depicts a left side elevation view in section of the end effector of  FIG. 5  after the firing bar has fully fired. 
       FIG. 7  is a left side elevation view of the handle of the surgical stapling and severing instrument of  FIG. 1  with a left housing shell removed. 
       FIG. 8  is a perspective, exploded view of the handle of  FIG. 7 . 
       FIG. 9  is a right side elevational view of the handle of the surgical stapling and severing instrument of  FIG. 1  with a right handle shell portion removed and with the closure trigger in the unlocked position. 
       FIG. 10  is a right side exploded assembly view of the linked rack of the firing mechanism of  FIG. 9 . 
       FIG. 11  is another right side elevational view of the handle of the surgical stapling and severing instrument of  FIG. 1  with a right handle shell portion removed and with the closure trigger in the locked position. 
       FIG. 12  is a right side exploded assembly view of a manual retraction assembly embodiment employed in the surgical stapling and severing instrument of  FIG. 1 . 
       FIG. 13  is a right side perspective assembly view of the manual retraction assembly of  FIG. 12 . 
       FIG. 14  is a left side assembly view of the manual retraction assembly of  FIGS. 11 and 12 . 
       FIG. 15  is another left side assembly view of the manual retraction assembly of  FIGS. 11-13  with the second gear shown in cross-section. 
       FIG. 16  is a left side elevational view of the manual retraction assembly and corresponding portion of the handle housing of  FIGS. 12-15 , with the manual retraction assembly shown in an up position and with portions of the assembly shown in cross-section for clarity. 
       FIG. 17  is another left side elevational view of the manual retraction assembly and corresponding portion of the handle housing of  FIGS. 12-16 , with the manual retraction assembly shown in a down or actuated position and with portions of the assembly shown in cross-section for clarity. 
       FIG. 18  is a perspective view of another surgical stapling and severing instrument of other various embodiments of the present invention. 
       FIG. 19  is a left side elevation view of the handle of the surgical stapling and severing instrument of  FIG. 18  with a left handle shell portion removed. 
       FIG. 20  is a perspective, exploded view of the handle of  FIG. 19 . 
       FIG. 21  is a left side assembly view of a manual retraction assembly of the surgical stapling and severing instrument of  FIG. 18 . 
       FIG. 22  is a perspective view of another surgical stapling and severing instrument of other various embodiments of the present invention. 
       FIG. 23  is a perspective, exploded view of the handle of the surgical stapling and severing instrument of  FIG. 22 . 
       FIG. 24  is an exploded assembly view of a manual retraction assembly of the surgical stapling and severing instrument of  FIG. 12 . 
       FIG. 25  is a perspective view of the manual retraction assembly of  FIG. 24 . 
       FIG. 26  is a left side elevation view of the handle of the surgical stapling and severing instrument of  FIG. 22  with a left handle shell portion removed and the instrument in an unfired position. 
       FIG. 27  is another left side elevational view of the handle of the surgical stapling and severing instrument of  FIG. 22  with the left handle shell portion removed and with the closure trigger in the locked position and the manual retraction assembly in the fully retracted position. 
   

   DETAILED DESCRIPTION 
   Turning to the Drawings, wherein like numerals denote like components throughout the several views,  FIGS. 1 and 2  depict a surgical stapling and severing instrument  10  that is capable of practicing the unique benefits of the present invention. The surgical stapling and severing instrument  10  may incorporate an end effector  12  having an anvil  14  that is pivotally attached to an elongate channel  16 , forming opposing jaws for clamping tissue to be severed and stapled. The end effector  12  may be coupled by an elongate shaft assembly  18  to a handle  20  ( FIG. 1 ). An implement portion  22 , formed by the end effector  12  and shaft assembly  18 , is advantageously sized for insertion through a trocar or small laparoscopic opening to perform an endoscopic surgical procedure while being controlled by a surgeon grasping the handle assembly  20 . The handle assembly  20  may advantageously include features that allow separate closure motions and firing motions, lockouts to prevent inadvertent or ill-advised firing of the end effector, as well as enabling multiple firing strokes to effect firing (i.e., severing and stapling) of the end effector  12  while indicating the degree of firing to the surgeon. In addition, as will be described in detail below, various embodiments may employ a unique and novel manually actuatable retraction mechanism for retracting the firing members without any assistance from a retraction spring or other retraction arrangement, the forces of which must be overcome during the firing operation. 
   To these ends, a closure tube  24  of the shaft assembly  18  is coupled between a closure trigger  26  ( FIG. 1 ) and the anvil  14  to cause closure of the end effector  12 . Within the closure tube  24 , a frame  28  is coupled between the elongate channel  16  and the handle assembly  20  to longitudinally position and support the end effector  12 . A rotation knob  30  may be coupled with the frame  28 , and both elements are rotatably coupled to the handle assembly  20  with respect to a rotational movement about a longitudinal axis of the shaft assembly  18 . Thus, the surgeon can rotate the end effector  12  by turning the rotation knob  30 . The closure tube  24  is also rotated by the rotation knob  30  but retains a degree of longitudinal movement relative thereto to cause the closure of the end effector  12 . Within the frame  28 , a firing rod  32  is positioned for longitudinal movement and coupled between the anvil  14  of the end effector  12  and a multiple-stroke firing trigger  34 . The closure trigger  26  is distal to a pistol grip  36  of the handle assembly  20  with the firing trigger  34  distal to both the pistol grip  36  and closure trigger  26 . 
   In endoscopic operation, once the implement portion  22  is inserted into a patient to access a surgical site, a surgeon may refer to an endoscopic or other diagnostic imaging device to position tissue between the anvil  14  and elongate channel  16 . Grasping the closure trigger  26  and pistol grip  36 , the surgeon may repeatedly grasp and position the tissue. Once satisfied as to the location of the tissue relative to the end effector  12  and the amount of tissue therein, the surgeon depresses the closure trigger  26  fully toward the pistol grip  36 , clamping the tissue in the end effector  12  and locking the closure trigger  26  in this clamped (closed) position. If not satisfied with this position, the surgeon may release the closure trigger  26  by depressing a closure release button  38  and thereafter repeat the procedure to clamp tissue. 
   If the clamping is correct, the surgeon may proceed with firing the surgical stapling and severing instrument  10 . Specifically, the surgeon grasps the firing trigger  34  and pistol grip  36 , depressing the firing trigger  34  a predetermined number of times. The number of firing strokes necessary may be ergonomically determined based on a maximum hand size, maximum amount of force to be imparted to the instrument during each firing stroke, and the longitudinal distance and force needed to be transferred through the firing rod  32  to the end effector  12  during firing. 
   During these strokes, the surgeon may reference an indicator, depicted as an indicating knob  40 , that positionally rotates in response to the multiple firing strokes. Additionally, the position of the indicating knob  40  may confirm that full firing has occurred when encountering resistance to further cycling of the firing trigger  34 . It should be appreciated that various indicia and instructions may be added to the handle assembly  20  to enhance the indication provided by the rotation of the indicating knob  40 . 
   It will be appreciated that the terms “proximal” and “distal” are used herein with reference to a clinician gripping a handle of an instrument. Thus, the end effector  12  is distal with respect to the more proximal handle assembly  20 . Analogous terms such as “front” and “back” similarly correspond respectively to distal and proximal. It will be further appreciated that for convenience and clarity, spatial terms such as “vertical” and “horizontal” are used herein with respect to the drawings. However, surgical instruments are used in many orientations and positions, and these terms are not intended to be limiting and absolute. 
   The present invention is being discussed in terms of endoscopic procedures and apparatus. However, use herein of terms such as “endoscopic”, should not be construed to limit the present invention to a surgical stapling and severing instrument for use only in conjunction with an endoscopic tube (i.e., trocar). On the contrary, it is believed that the present invention may find use in any procedure where access is limited to a small incision, including but not limited to laparoscopic procedures, as well as open procedures. 
   E-Beam Firing Member 
   The advantages of a handle assembly  20 , which is capable of providing multiple-stroke firing motion, has application to a number of instruments, with one such end effector  12  being depicted in  FIGS. 2-6 . With particular reference to  FIG. 4 , the end effector  12  responds to the closure motion from the handle assembly  20  (not depicted in  FIGS. 2-6 ) first by including an anvil face  50  ( FIGS. 2 ,  4 ,  6 ) connecting to an anvil proximal end  52  that includes a pair of laterally projecting anvil pivot pins  54  that are proximal to a vertically projecting anvil feature  56  ( FIG. 4 ). The anvil pivot pins  54  translate within kidney shaped openings  58  in the elongate channel  16  to open and close anvil  14  relative to elongate channel  16 . The anvil feature  56  engages a tab  59  ( FIGS. 2 ,  4 ,  6 ) extending inwardly in tab aperture  60  on a distal end  62  of the closure tube  24 , the latter distally terminating in a distal edge  64  that pushes against the anvil face  50 . Thus, when the closure tube  24  moves proximally from its open position, the tab  59  of the closure tube  24  draws the anvil feature  56  proximally, and the anvil pivot pins  54  follow the kidney shaped openings  58  of the elongate channel  16  causing the anvil  14  to simultaneously translate proximally and rotate upward to the open position. When the closure tube  24  moves distally, the tab  59  in the tab aperture  60  releases from the anvil feature  56  and the distal edge  64  pushes on the anvil face  50 , closing the anvil  14 . 
   With continued reference to  FIG. 4 , the implement portion  22  also includes components that respond to the firing motion of the firing rod  32 . In particular, the firing rod  32  rotatably engages a firing trough member  66  having a longitudinal recess  68 . Firing trough member  66  moves longitudinally within frame  28  in direct response to longitudinal motion of firing rod  32 . A longitudinal slot  70  in the closure tube  24  operably couples with the rotation knob  30  (not shown in  FIGS. 2-6 ). The length of the longitudinal slot  70  in the closure tube  24  is sufficiently long to allow relative longitudinal motion with the rotation knob  30  to accomplish firing and closure motions respectively with the coupling of the rotation knob  30  passing on through a longitudinal slot  72  in the frame  28  to slidingly engage the longitudinal recess  68  in the frame trough member  66 . 
   The distal end of the frame trough member  66  is attached to a proximal end of a firing bar  76  that moves within the frame  28 , specifically within a guide  78  therein, to distally project an E-beam firing member  80  into the end effector  12 . The end effector  12  includes a staple cartridge  82  that is actuated by the E-beam  80 . The staple cartridge  82  has a tray  84  that holds a staple cartridge body  86 , a wedge sled driver  88 , staple drivers  90  and staples  92 . It will be appreciated that the wedge sled driver  88  longitudinally moves within a firing recess  94  ( FIG. 2 ) located between the cartridge tray  84  and the cartridge body  86 . The wedge sled driver  88  presents camming surfaces that contact and lift the staple drivers  90  upward, driving the staples  92  up from staple apertures  96  ( FIG. 3 ) into contact with staple forming grooves  98  ( FIG. 3 ) of the anvil  14 , creating formed “B”-shaped staples, such as depicted at  100  of  FIG. 6 . With particular reference to  FIG. 3 , the staple cartridge body  86  further includes a proximally open, vertical slot  102  for passage of the E-beam  80 . Specifically, a cutting surface  104  is provided along a distal end of E-beam  80  to cut tissue after it is stapled. 
   In  FIGS. 2 ,  5 ,  6 , respectively, the end effector  12  is depicted in a sequence of open (i.e., start) condition, clamped and unfired condition or position, and fully fired condition or position. Features of the E-beam  80  that facilitate firing of the end effector  12 , in particular, are depicted. In  FIG. 2 , the wedge sled driver  88  is in its fully proximal position, indicating an unfired staple cartridge  82 . A middle pin  106  is aligned to enter the firing recess  94  in the staple cartridge  82 , for distally driving the wedge sled driver  88 . A bottom pin or cap  108  of the E-beam  80  slides along a bottom surface of the elongate channel  16 , thus the middle and bottom pins  106 ,  108  slidingly engage the elongate channel  16 . In the open and unfired state of  FIG. 2 , a top pin  110  of the E-beam  80  has entered and is residing within an anvil pocket  112  of the anvil  14 , and thus does not impede repeated opening and closing of the anvil  14 . 
   In  FIG. 5 , the end effector  12  is depicted as clamped and ready to fire. The top pin  110  of the E-beam  80  is aligned with an anvil slot  114  in the anvil  14  distal to and communicating with the anvil pocket  112 . In  FIG. 6 , the E-beam  80  has been fully fired, with the upper pin  110  translating down the anvil slot  114 , affirmatively spacing the anvil  14  from the elongate channel  16  as the cutting surface  104  severs clamped tissue. Simultaneously, the middle pin  106  has actuated the staple cartridge  82  as previously described. Thereafter, the E-beam  80  is retracted prior to opening the end effector  12  and replacing the staple cartridge  82  for an additional operation. 
   The illustrative end effector  12  is described in greater detail in four commonly-owned U.S. patents and a patent application, the disclosure of each being hereby incorporated by reference in their entirety: (1) U.S. Pat. No. 7,044,352 to Frederick E. Shelton IV, Michael E. Setser, William B. Weisenburgh II, issued May 16, 2006 and entitled “Surgical Stapling Instrument Having a Single Lockout Mechanism For Prevention of Firing”; (2) U.S. Pat. No. 7,000,818 to Frederick E. Shelton IV, Michael E. Setser, Brian J. Hemmelgarn II, issued Feb. 21, 2006 and entitled “Surgical Stapling Instrument Having Separate Distinct Closing and Firing Systems”; (3) U.S. Pat. No. 6,988,649 to Frederick E. Shelton IV, Michael E. Setser, and William B. Weisenburgh II, issued Jan. 24, 2006 and entitled “Surgical Stapling Instrument Having A Spent Cartridge Lockout”; (4) U.S. Pat. No. 7,143,923, to Frederick E. Shelton IV, Michael E. Setser, and William B. Weisenburgh II, issued Dec. 5, 2006 and entitled Surgical Stapling Instrument Having A Firing Lockout For An Unclosed Anvil”; and (5) U.S. patent application entitled “Surgical Stapling Instrument Incorporating an E-Beam Firing Mechanism”, Ser. No. 10/443,617, to Frederick E. Shelton IV, Michael E. Setser, William B. Weisenburgh II, filed 20 June 2003, now U.S. Pat. No. 6,978,921. However, the unique and novel features of various embodiments of the present invention may also be employed with different types of end effectors without departing from the spirit and scope of the present invention. 
   It should be appreciated that although a nonarticulating shaft assembly  18  is illustrated herein, applications of the present invention may include instruments capable of articulation, such as those described in three commonly owned U.S. patents and two commonly owned U.S. patent applications, the disclosure of each being hereby incorporated by reference in their entirety: (1) U.S. Pat. No. 7,111,769 to Kenneth S. Wales, Douglas B. Hoffman, Frederick E. Shelton IV, and Jeffrey S. Swayze, issued Sept. 26, 2006, entitled “Surgical Instrument Incorporating An Articulation Mechanism Having Rotation About the Longitudinal Axis”; (2) U.S. Pat. No. 6,981,628 to Kenneth S. Wales, issued January 3, 2006, entitled “Surgical Instrument With A Lateral-Moving Articulation Control”; (3) U.S. Pat. No. 7,055,731 to Frederick E. Shelton IV, Michael E. Setser, William B. Weisenburgh II, issued June 6, 2006entitled “Surgical Stapling Instrument Incorporating A Tapered Firing Bar For Increased Flexibility Around The Articulation Joint”; (4) U.S. Patent Publication No. 2005/0006429entitled “Surgical Stapling Instrument Having Articulation Joint Support Plates For Supporting A Firing Bar”, Ser. No. 10/615,971, to Kenneth S. Wales and Joseph Charles Hueil, filed 9 July 2003, now U.S. Pat. No. 6,964,363; and (5) U.S. patent application entitled “Surgical Stapling Instrument Incorporating An Articulation Joint For a Firing Bar Track”, Ser. No. 10/615,962, to Brian J. Hemmelgarn, filed 9 July 2003. Those of ordinary skill in the art will readily understand, however, that the unique and novel aspects of various features of the present invention may be employed in connection with other types of articulating surgical instruments without departing from the spirit and scope of the present invention. 
   With reference to  FIGS. 7-9 , the elongate shaft assembly  18  has as its outer structure a longitudinally reciprocating closure tube  24  that pivots the anvil  14  ( FIGS. 1 and 2 ) to effect closure in response to proximal depression of the closure trigger  26  of the handle assembly  20 . The elongate channel  18  is connected to the handle assembly  20  by a frame  28  that is internal to the closure tube  24 . The frame  28  is rotatably engaged to the handle assembly  20  so that twisting the rotation knob  30  causes rotation of the implement portion  22 . With particular reference to  FIG. 8 , each half shell  30   a ,  30   b  of the rotation knob  30  includes an inward projection  31  that enters a respective longer side opening  70  in the closure tube  24  and inward to engage the frame  28  that determines the rotated position of the implement portion  22 . The longitudinal length of the longer opening  70  is sufficiently long enough to facilitate longitudinal movement of the closure tube  24  during the closure operation. 
   Closure System 
   In various embodiments, operation of the closure tube  24  is controlled by means of a closure drive  23  which includes the closure trigger  26 . The closure trigger  26  has a an upper portion  160  that is configured to activate a closure yoke  162  via a closure link  164 . The closure link  164  is pivotally attached at its distal end to the closure yoke  162  by a closure yoke pin  166  and is pivotally attached to the closure trigger  26  at its proximal end by a closure link pin  168 . As can be seen in  FIG. 7 , the closure trigger  26  is urged to the open position by a closure trigger tension spring  246  that is connected proximally to the upper portion  160  of the closure trigger  26  and a handle housing  154  formed by right and left half shells  156 ,  158 . 
   The upper portion  160  of the closure trigger  26  also includes a proximal crest  170  that has an aft notch  171  formed therein. See  FIGS. 7 and 8 . In various embodiments, a closure release button  38  is pivotally attached to the handle housing  154  by a pivot rod arrangement  174 . As can be seen in  FIG. 8 , a locking arm  172  protrudes from the closure release button  38  and, as will be discussed in further detail below, is configured to lockingly engage the upper portion  160  of the closure trigger  26 . A compression spring  180  is employed between the closure release button  38  and the handle housing  154  to bias the closure release button away from the housing  154  about the pivot rod assembly  174 .  FIG. 7  depicts the closure trigger  26  in an unactuated position. As can be seen in that Figure, when in that position, the pivoting locking arm  172  rides upon the proximal crest  170 . Such action of the locking arm  172  causes the closure release button  38  to be drawn in towards the handle housing  154  against the force of coil spring  180 . When the closure trigger  26  reaches its fully depressed position, the pivoting locking arm  172  drops into the aft notch  171  in the upper portion of the locking trigger  26  under the urging of the compression spring  180 . When in that position, the closure trigger is locked in position. In addition, as will be further discussed below, when the locking arm  172  is in that locked position, the firing trigger  34  may be actuated to actuate the firing mechanism  150 . When the firing mechanism  150  is in the retracted position, manual depression of the closure release button  38  rotates the pivoting locking arm  172  upward out of retaining engagement with the aft notch  171  in the upper portion of the closure trigger  26  and thereby unlocks the closure trigger  26 . 
   Firing System 
   In various embodiments of the invention, a linked transmission firing drive  150  of the type disclosed in U.S. Pat. No. 7,083,075 to Jeffrey S. Swayze, Frederick E. Shelton, IV, Kevin R. Doll, and Douglas B. Hoffman, entitled Multi-Stroke Mechanism With Automatic End of Stroke Retraction, issued Aug. 1, 2006, the relevant portions of which are herein incorporated by reference, may be employed to extend and retract the firing rod  32  as will be further discussed below. With the closure trigger  26  retracted and fully depressed, the firing trigger  34  is unlocked and may be depressed toward the pistol grip  36  multiple times to effect the firing of the end effector  12 . As depicted in  FIG. 8 , the firing trigger  34  pivots about a firing trigger pin  202  that laterally traverses and is attached to the right and left half shells  156 ,  158 . 
   An upper portion  204  of the firing trigger  34  moves distally about the firing trigger pin  202  as the firing trigger  34  is depressed toward the pistol grip  36 , stretching a proximally placed firing trigger tension spring  206  connected between an upper portion  204  of the firing trigger  34  and the housing  154 . See  FIGS. 7 and 8 . The upper portion  204  of the firing trigger  34  engages a firing mechanism  150  in the form of a linked rack  200  during each firing stroke depression by a spring biased side pawl mechanism  210  that also disengages when the firing trigger  34  is released. 
   Linked Rack 
   As can be seen in  FIGS. 8 and 10 , each link  196   a - d  is pinned to adjacent links  196   a - d  for downward, proximal rotation into the pistol grip  36 . Although bendable in this direction, the linked rack  200  forms a rigid configuration when against a columnar loading, especially a loading that would otherwise urge the distal links  196   a - d  to bend upwardly. In particular, each link  196   a - c  proximally terminates in an extension  300  having lateral through hole  302  on a lower portion thereof; Similarly, each link  196   b - d  distally terminates in an extension  300   a  that has a lateral hole  302   a  therethrough. As can be seen in  FIG. 10 , the holes  300 ,  300   a  are aligned to receive corresponding pivot pins  310  therethrough to hingedly attach the links  196   a - d  together in a linear fashion. 
   Each leading link  196   a - d  has a flat surface  312  at the proximal end that is generally perpendicular to the direction of columnar loading from the firing rod  32 . Each trailing link  196   a - d  has a contact surface  314  at the distal end that is also generally perpendicular to the direction of columnar loading. The lateral through hole  302  is spaced away sufficient so that a notch  316  is formed between lower portions of adjacent flat surface  312  and contact surface  314  to provide clearance for downward pivoting of the trailing link  196   a - d  relative to the leading link  196   a - d . Yet, the upper portions of the adjacent flat surface  312  and contact surface  314  are registered for abutment as the leading and trailing links  196   a - d  are longitudinally aligned, thereby resisting further upward deflection. 
   When adjacent links  196   a - d  are horizontally aligned, the holes  302  and pins  310  are located below the line of action of the firing rod  32 . As will be discussed in further detail below, when loads are applied to the firing trigger  34 , a traction biasing mechanism  210  applies a pushing load along the line of action and biases consecutive horizontal links  196   a - d  together. Thus, imparting a line of action of a firing force above the pivot pins  310  maintains any leading links  196   a - d  in a rigid, straight configuration. It should be appreciated that although pinned connections between links  196   a - d  have been advantageously depicted, other resilient or flexible connection arrangements may be used. In addition, four links  196   a - d  are depicted, but various numbers and lengths of links may be selected depending on firing travel, radius of curvature, etc. 
   As can also be seen in  FIG. 10 , a left side  304  of each link  196   a - d  includes the toothed upper surface  222 . In addition, a right side  306  of each link  196   a - c  has a ramped right-side track  282  formed by a proximally and rightwardly facing beveled surface  284 . The distal end of the front link  196   a  is configured for attachment to the proximal end of the firing rod  32 . As shown in  FIG. 8 , an arcuate band  192  may be employed to support the firing mechanism  150  as it is actuated. In various embodiments, the band is fabricated from steel or other metal. However, the band  192  may be successfully fabricated from other suitable materials. As can be seen in  FIG. 8 , a distally-disposed end  194  of the band  192  is attached to an attachment feature  195  on the front link  196   a . In various embodiments, a small spring  400  may be coupled to the proximal end of the link  196   d  and the proximal end of the band  192  ( FIGS. 8 and 9 ) to draw the links  196   a - d  into conforming engagement with the arcuate band  192 . Those of ordinary skill in the art will understand that the links  196   a - d  and band  192  move essentially as a unit. Thus, spring  400  does not apply any retraction force whatsoever to the firing rod  32 . 
   Side Pawl Mechanism 
   In various embodiments, the upper portion  204  of the firing trigger  34  engages the linked rack  200  during each firing trigger depression through a spring biased side pawl mechanism  210  that also disengages when the firing trigger  34  is released. In particular, a ramped right-side track  282  formed by a proximally and rightwardly facing beveled surface  284  in each of the links  1196   a - 1196   d  is engaged by a side pawl assembly  285  as the firing trigger  34  is depressed. Turning to  FIG. 8 , one form of a side pawl assembly  285  that may be successfully employed includes a pawl slide  270  that is configured with right and left lower guides  272 . One guide  272  slides in a left track  274  formed in the closure yoke  162  below the rack channel  291  and the other guide  272  slides in a right track  275  in a closure yoke rail  276  that parallels rack channel  291 . As can be seen in  FIG. 8 , the closure yoke rail  276  is attached to or is integral with a rack channel cover  277  that is coupled to the closure yoke  162  to enclose the rack channel  291 . A compression spring  278  is attached between a hook  279  on a top proximal position on the closure yoke rail  276  and a hook  280  on a distal right-side of the pawl slide  270 , which keeps the pawl slide  270  drawn proximally into contact with the upper portion  204  of the firing trigger  34 . 
   With reference to  FIGS. 8 and 11 , a pawl block  318  is located on the pawl slide  270  and is pivotally attached thereto by a vertical aft pin  320  that passes through a left proximal corner of pawl block  318  and pawl slide  270 . A kick-out block recess  322  is formed on a distal portion of a top surface of the block  318  to receive a kick-out block  324  pivotally pinned thereto by a vertical pin  326  whose bottom tip extends into a pawl spring recess  328  on a top surface of the pawl slide  270 . A pawl spring  330  ( FIG. 8 ) in the pawl spring recess  328  extends to the right of the vertical front pin  326  urging the pawl block  318  to rotate counterclockwise when viewed from above into engagement with the ramped right-side track  282 . A small coil spring  332  ( FIG. 8 ) in the kick-out block recess  322  urges the kick-out block  324  to rotate clockwise when viewed from above, its proximal end urged into contact with a contoured lip  334  formed in the closure yoke  162  above the rack channel  291 . 
   As the firing trigger  34  is fully depressed and begins to be released, the kick-out block  324  encounters a ridge  336  in the contoured lip  334  as the pawl slide  270  retracts, forcing the kick-out block  324  to rotate clockwise when viewed from above and thereby kicking out the pawl block  318  from engagement with the linked rack  200 . The shape of the kick-out block recess  322  stops the clockwise rotation of the kick-out block  324  to a perpendicular orientation to the contoured lip  334  maintaining this disengagement during the full retraction and thereby eliminating a ratcheting noise. 
   Retraction System 
   The embodiment depicted in  FIGS. 7-17  contains a retraction assembly  500  that is configured to enable the surgeon to manually retract the firing bar  32  without any other assistance from springs or other retraction arrangements that serve to place a drag on the firing system and which ultimately require the generation of higher firing forces to actuate the firing mechanism. As can be most particularly seen in  FIGS. 16 and 17 , in these embodiments, a first gear  220  is operably mounted to mesh with the toothed upper, left surfaces  222  of the linked rack  200 . The first gear  220  also engages a second gear  230  that has a smaller right-side ratchet gear  231  thereon. Both the first gear  220  and second gear  230  are rotatably connected to the handle housing  154  respectively on front axle  232  and aft axle  234 . One end of the axle  232  extends through the respective right housing half shell  156  and is attached to a right indication member in the form of an indicator gauge wheel  40 . Similarly, the other end of the aft axle  232  extends through the left housing half shell  158  and is attached to a left indicator gauge wheel  41 . Because the aft axle  234  is free spinning in the handle housing  154  and has a keyed engagement to the second gear  230 , the indicator gauge wheels  40 ,  41  rotate with the second gear  230 . The gear relationship between the linked rack  200 , first gear  220  and second gear  230  may be advantageously selected so that the toothed upper surface  222  has tooth dimensions that are suitably strong and that the second gear  230  makes no more than one revolution during the full firing travel of the linked transmission firing mechanism  150 . 
   The smaller right-side ratchet gear  231  of the second gear  230  extends into a hub  506  of a manual retraction member in the form of retraction lever  42  specifically aligned with a vertical longitudinally-aligned slot  508  ( FIGS. 12 and 15 ) bisecting the hub  506 . A lateral through hole  510  of the hub  506  communicates with an upper recess  512 . See  FIG. 12 . A front portion  514  is shaped to receive a proximally directed retraction pawl  516  that pivots about a rightward lateral pin  518  formed in a distal end of the upper recess  512 . An aft portion  520  is shaped to receive an L-shaped spring tab  522  that urges the retraction pawl  516  downward into engagement with the right-side smaller ratchet gear  231 . A hold-up structure  524  ( FIGS. 16 and 17 ) projects from the right half shell  156  into the upper recess  512  for supporting and preventing the retraction pawl  516  from engaging the smaller right-side ratchet gear  231  when the manual retraction lever  42  is up ( FIG. 16 ). A spring  525  ( FIG. 8 ) urges the manual retraction lever  42  into the up position. 
   After the firing sequence has been completed, the clinician can use the manual retraction lever  42  to retract the firing bar  32  to the unactuated position. This can be accomplished by grasping the pistol grip  36  and sequentially depressing and releasing the manual retraction lever  42 . As the manual retraction lever  42  is depressed ( FIG. 17 ), the locking pawl  516  rotates clockwise and no longer is held up by the hold-up structure  524  and engages the smaller right-side ratcheting gear  231 , rotating the second gear  230  clockwise when viewed from the left. Because the second gear  230  is in meshing engagement with the forward idler gear  220 , clockwise rotation of the second gear  230  causes the forward idler gear  220  to rotate in a counterclockwise direction. As the forward idler gear  220  rotates in a counterclockwise direction, it drives the linked rack in a proximal direction. Thus, continued ratcheting action (arrow A in  FIG. 17 ) of the manual retraction lever  42  will cause the linked rack  200  to be retracted (arrow B) and draw the firing rod  32  to a fully retracted position. 
   In various embodiments, the invention may be constructed with means for providing the clinician with an indication of how far the firing bar  32  has been advanced and retracted. In those embodiments, the axle  234  on which the indicator gear  230  is journaled is connected to the externally viewable indicator wheels  40 ,  41 . See  FIG. 8 . In such arrangement, the surgeon can determine the relative position of the firing mechanism  150  by observing the positions of the indicator wheels  40 ,  41  and thereby determine how many strokes of the firing trigger  34  are required to complete firing. For instance, full firing travel may require three full firing strokes and thus the indicator wheels  40 ,  41  rotate up to one-third of a revolution each per stroke. The gear relationship between the linked rack  200 , first gear  220  and second gear  230  may be advantageously selected so that the toothed upper surface  222  has tooth dimensions that are suitably strong and that the second gear  230  makes no more than one revolution during the full firing travel of the linked transmission firing mechanism  150 . 
   Interaction Between the Closure System and Firing System 
   When the linked rack  200  is fully retracted and both triggers  26 ,  34  are open as shown in  FIGS. 7 and 9 , an opening  240  in a circular ridge  242  on the left side of the second gear  230  is presented to an upper surface  244  of the locking arm  172 . See  FIG. 7 . Locking arm  172  is biased into the opening  240  by contact with the closure trigger  26 , which in turn is urged to the open position by a closure tension spring  246 . As can be seen in FIG.  7 ,when a portion of the locking arm  172  extends into the opening  240  in the circular ridge  242 , the second gear  230  cannot rotate. Thus, when the locking trigger  26  is in the unlocked position, the firing mechanism  150  cannot be actuated. 
     FIGS. 18-21  illustrate another surgical stapling and severing instrument  10 ′ of the present invention. As can be seen in  FIG. 20 , this embodiment may employ the same elements as the instrument  10  described above, except for the side mounted and rotatably supported manual retraction and indicating lever  642  and related components. More particularly and with reference to  FIGS. 19 and 20 , the instrument  10 ′ includes a first gear  620  that is operably mounted to mesh with the toothed upper, left surfaces  222  of the linked rack  200 . The first gear  620  also engages a hubbed aft gear  630 . Both the first gear  620  and the aft gear  630  are rotatably connected to the handle housing  154 ′ respectively on front idler axle  232  and aft idler axle  234 . One end of the aft axle  232  extends through the respective right housing half shell  156 ′ and is attached to a right indicator gauge wheel  40 . The other end of the aft axle  232  extends through the left housing half shell  158 ′ and is attached to the manual retraction indication lever  642 . Because the aft axle  234  is free spinning in the handle housing  154 ′ and has a keyed engagement to the second gear  630 , the manual retraction and indication lever  642  rotates with the second gear  630 . 
   As the clinician advances the firing rod  32  distally by ratcheting the firing handle  34  in the manner described in detail above, the toothed portions  222  of the links  196   a - d  cause the first gear  620  to rotate (direction “C” in  FIG. 19 ) which, by virtue of its meshing engagement with the second gear  630 , causes the second gear  630  and the manual retraction and indication lever  642  to rotate (direction “D” in  FIG. 19 ).  FIGS. 18 and 19  illustrate the position of the manual retraction and indication lever  642  in the unfired and fully fired positions. The gear relationship between the linked rack  200 , first gear  620  and second gear  630  may be advantageously selected so that the toothed upper surface  222  has tooth dimensions that are suitably strong and that the second gear  630  makes no more than one revolution during the full firing travel of the linked transmission firing mechanism  150 . Thus, the clinician can determine how far along the firing sequence is by monitoring the position of the manual retraction and indication lever  642 . 
   After the firing sequence has been completed, the clinician can use the manual retraction lever  642  to retract the firing bar  32  to the unactuated (retracted) position. This can be accomplished by grasping the manual retraction lever  642  and rotating it in the clockwise (arrow “E” in  FIG. 18 ). As the retraction lever  642  is rotated in that direction, it causes the second gear  630  to also rotate in that direction. Because the second gear  630  is in meshing engagement with the first gear  620 , the first gear  620  rotates in a clockwise direction in  FIG. 18  which draws the linked rack in the proximal direction until it reaches it starting-unfired position. Again, this embodiment does not employ any spring as or other retraction members that apply a retraction force to the firing system which must be overcome during the firing sequence. The gear relationship between the linked rack  200 , first gear  620  and second gear  630  may be advantageously selected so that the toothed upper surface  222  has tooth dimensions that are suitably strong and that the second gear  630  makes no more than one revolution during the full firing travel of the linked transmission firing mechanism  150 . 
     FIGS. 22-27  illustrate another surgical stapling and severing instrument  10 ″ of the present invention. As can be seen in  FIG. 23 , this embodiment may employ many of the same elements as the instrument  10  described above. As can be most particularly seen in  FIGS. 23-27 , this embodiment employs a manual retraction assembly  700  for manually retracting the firing rod  32 . In various embodiments, the manual retraction assembly  700  includes a drive gear  720  that is operably mounted to mesh with the toothed upper, left surfaces  222  of the linked rack  200 . The drive gear  720  is rotatably supported within the handle housing  154 ″ on an axle  232  that is supported between handle shell portions  156 ″,  158 ″. The manual retraction assembly  700  may further include a second gear rack  800  that is movably supported within a rack passage  820  formed in the handle housing  154 ″. As can be seen in  FIG. 23 , a track portion  822  is formed in the right shell portion  156  and a track portion  824  is formed in the left shell portion  158 . When the shell portions  156 ,  158  are interconnected together to form the handle housing  154 ″, the track portions  822 ,  824  cooperate to form the rack passage  820 . The rack passage  820  is sized relative to the second gear rack  800  such that the second gear rack  800  can move axially back and forth (arrow “F” in  FIG. 26 ) within the handle housing  154 ″. Second gear rack  800  is movably supported within the rack passage  820  and is in meshing engagement with the drive gear  720 . 
   As can be seen in  FIGS. 24 and 25 , the second gear rack  800  is attached to a retraction handle  900  by means of a handle yoke  910  that is pinned to the second gear rack  800  with a pin  912  and is also pinned to the retraction handle  900  by pin  914 . The retraction handle  900  may be configured with a pair of pivot legs  902 ,  904  for pivotal attachment to the handle housing  154 ″. In particular, leg  902  may be pinned to the right hand shell portion  156 ″ by pin  906  and leg  904  may be pivotally pinned to left hand shell portion  158 ″ by pin  908 . See  FIG. 23 . 
   As the clinician advances the firing rod  32  distally by ratcheting the firing trigger  34  in the manner described above, the toothed portions  222  of the links  196   a - d  cause the drive gear  720  to rotate clockwise (direction “G” in  FIGS. 26 and 27 ) which, by virtue of its meshing engagement with the second gear rack  800 , causes the second gear rack  800  to move in the proximal direction (arrow “H” in  FIG. 27 ).  FIG. 27  illustrates the position of the second gear rack  800  and the manual retraction handle  900  at the completion of the firing stroke (i.e., the position wherein the firing rod  32  has been moved to its distal most position). As can be seen in that Figure, a grip portion  930  of the retraction handle is spaced away from the handle housing  154 . To retract the firing rod  32 , the clinician simply pushes the retraction handle in the “H” direction until the second gear rack  800  reaches the position illustrated in  FIG. 26  wherein the grip portion  930  is adjacent the handle housing  154 . Those of ordinary skill in the art will appreciate that the clinician can monitor the progress of the firing stroke by observing the position of the retraction handle  900  as the clinician continues to ratchet the firing trigger  34 . In addition, this embodiment does not employ any springs or other retraction members that apply a retraction force to the firing system which must be overcome during the firing sequence. 
   In various embodiments, the closure trigger  26  has a an upper portion  160  that is configured to activate a closure yoke  162  via a closure link  164 . The closure link  164  is pivotally attached at its distal end by a closure yoke pin  166  to the closure yoke  162  and is pivotally attached at its proximal end by a closure link pin  168 . As can be seen in  FIG. 26 , the closure trigger  26  is urged to the open position by a closure trigger tension spring  246  that is connected proximally to the upper portion  160  of the closure trigger  26  and a handle housing  154 ″. 
   The upper portion  160  of the closure trigger  26  includes a proximal crest  170  with an aft notch  171 . See  FIGS. 23 and 26 . The closure release button  38  and a pivoting locking arm  172 ″ are connected by a central lateral pivot  174 . A compression spring  180  biases the closure release button  38  proximally (clockwise about the central lateral pivot  174  as viewed from the right). With the upper portion  160  back when the closure trigger  26  is released as depicted in  FIG. 26 , the pivoting locking arm  172 ″ rides upon the proximal crest  170  drawing in the closure release button  38 . As can also be seen in  FIG. 26 , the upper end  173 ″ of the pivoting locking arm  172 ″ is configured to extend into a recess  802  in the second gear rack  800  to thereby prevent actuation of the gear rack  800  to fire the instrument  10 ″. When the closure trigger  26  reaches its fully depressed position, it should be appreciated that the aft notch  171  is presented below the pivoting locking arm  172 ″ which drops into and locks against the aft notch  171  under the urging of the compression spring  180 . When the pivoting locking arm  172 ″ drops out of engagement with the second gear rack  800 , the gear rack  800  can then be axially advanced. With the firing components retracted, manual depression of the closure release button  38  rotates the pivoting locking arm  172 ″ upward unclamping the closure trigger  26 . 
   While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in considerable detail, it is not the intention of the applicant to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications may readily appear to those skilled in the art. 
   For instance, while a surgical stapling and severing instrument  10  is described herein that advantageously has separate and distinct closing and firing actuation, providing clinical flexibility. However, it should be appreciated that applications consistent with the present invention may include a handle that converts a single user actuation into a firing motion that closes and fires the instrument. 
   In addition, while a manually actuated handle is illustrated, a motorized or otherwise powered handle may benefit from incorporating a linked rack as described herein, allowing reduction of the size of the handle or other benefits. For instance, while partially stowing the linked rack into the pistol grip is convenient, it should be appreciated that the pivot connection between links allows for stowing the link parallel to the straight portion defined by the shaft and the barrel of the handle. In addition, various embodiments employ a unique and novel retraction assembly that enables the clinician to manually retract the firing rod and thus, the end effector firing bar, without the assistance of springs or other force generating members that may be employed to apply a retraction force to the firing drive. Such additional force generating devices, while helpful when retracting the firing rod, require the instrument to generate firing forces that must also overcome the forces generated by such additional retraction force generating members. Thus, the various retraction systems disclosed herein are said to generate the “sole” retraction motion or force. This means that the retraction motions/forces are generated by manipulation of the various retraction members by the clinician without any assistance from additional springs or force generating members. 
   While several embodiments of the invention have been described, it should be apparent, however, that various modifications, alterations and adaptations to those embodiments may occur to persons skilled in the art with the attainment of some or all of the advantages of the invention. For example, according to various embodiments, a single component may be replaced by multiple components, and multiple components may be replaced by a single component, to perform a given function or functions. This application is therefore intended to cover all such modifications, alterations and adaptations without departing from the scope and spirit of the disclosed invention as defined by the appended claims. 
   The devices disclosed herein can be designed to be disposed of after a single use, or they can be designed to be used multiple times. In either case, however, the device can be reconditioned for reuse after at least one use. Reconditioning can include an combination of the steps of disassembly of the device, followed by cleaning or replacement of particular pieces, and subsequent reassembly. In particular, the device can be disassembled, and any number of particular pieces or parts of the device can be selectively replaced or removed in any combination. Upon cleaning and/or replacement of particular parts, the device can be reassembled for subsequent use either at a reconditioning facility, or by a surgical team immediately prior to a surgical procedure. Those of ordinary skill in the art will appreciate that the reconditioning of a device can utilize a variety of different techniques for disassembly, cleaning/replacement, and reassembly. Use of such techniques, and the resulting reconditioned device, are all within the scope of the present application. 
   Preferably, the invention described herein will be processed before surgery. First a new or used instrument is obtained and, if necessary, cleaned. The instrument can then be sterilized. In one sterilization technique, the instrument is placed in a closed and sealed container, such as a plastic or TYVEK® bag. The container and instrument are then placed in a field of radiation that can penetrate the container, such as gamma radiation, x-rays, or higher energy electrons. The radiation kills bacteria on the instrument and in the container. The sterilized instrument can then be stored in the sterile container. The sealed container keeps the instrument sterile until it is opened in the medical facility. 
   Any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated materials does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material. 
   The invention which is intended to be protected is not to be construed as limited to the particular embodiments disclosed. The embodiments are therefore to be regarded as illustrative rather than restrictive. Variations and changes may be made by others without departing from the spirit of the present invention. Accordingly, it is expressly intended that all such equivalents, variations and changes which fall within the spirit and scope of the present invention as defined in the claims be embraced thereby.