Abstract:
A surgical fastening instrument is disclosed. The instrument comprises an end effector cartridge assembly, a handle, and a firing member, wherein an electric motor is configured to impart a firing motion to the firing member to eject fasteners from a fastener cartridge of the end effector cartridge assembly. The instrument further comprises an electronic lockout system configured to ascertain whether the fastener cartridge is present in the end effector, permit the motor to apply the firing motion to the firing member when the presence of the fastener cartridge has been ascertained, and prevent the motor from applying the firing motion to the firing member when the presence of the fastener cartridge has not been ascertained.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application under 35 U.S.C. §120 of U.S. patent application Ser. No. 13/627,241, filed Sep. 26, 2012, entitled SURGICAL INSTRUMENT, now U.S. Patent Application Publication No. 2013/0020375, which is a continuation application under 35 U.S.C. §120 of U.S. patent application Ser. No. 13/424,648, filed on Mar. 20, 2012, entitled SURGICAL INSTRUMENT HAVING RECORDING CAPABILITIES, now U.S. Pat. No. 8,752,747, which is a divisional application under 35 U.S.C. §121 of U.S. patent application Ser. No. 12/949,099, filed on Nov. 18, 2010, entitled SURGICAL INSTRUMENT HAVING RECORDING CAPABILITIES, now U.S. Pat. No. 8,167,185, which is a continuation application under 35 U.S.C. §120 of U.S. patent application Ser. No. 11/343,803, filed on Jan. 31, 2006, entitled SURGICAL INSTRUMENT HAVING RECORDING CAPABILITIES, now U.S. Pat. No. 7,845,537, the disclosures of which are incorporated herein by reference in their entireties. 
     The present application is related to the following U.S. patent applications, which were concurrently filed on Jan. 31, 2006, which are incorporated herein by reference:
     U.S. patent application Ser. No. 11/343,498, now U.S. Pat. No. 7,766,210, entitled MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH USER FEEDBACK SYSTEM; Inventors: Frederick E. Shelton, IV, John Ouwerkerk and Jerome R. Morgan   U.S. patent application Ser. No. 11/343,573, now U.S. Pat. No. 7,416,101, entitled MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH LOADING FORCE FEEDBACK; Inventors: Frederick E. Shelton, IV, John N. Ouwerkerk, Jerome R. Morgan, and Jeffrey S. Swayze   U.S. patent application Ser. No. 11/344,035, now U.S. Pat. No. 7,422,139, entitled MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH TACTILE POSITION FEEDBACK; Inventors: Frederick E. Shelton, IV, John N. Ouwerkerk, Jerome R. Morgan, and Jeffrey S. Swayze   U.S. patent application Ser. No. 11/343,447, now U.S. Pat. No. 7,770,775, entitled MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH ADAPTIVE USER FEEDBACK; Inventors: Frederick E. Shelton, IV, John N. Ouwerkerk, and Jerome R. Morgan   U.S. patent application Ser. No. 11/343,562, now U.S. Pat. No. 7,568,603, entitled MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH ARTICULATABLE END EFFECTOR; Inventors: Frederick E. Shelton, IV and Christoph L. Gillum   U.S. patent application Ser. No. 11/344,024, now U.S. Pat. No. 8,186,555, entitled MOTOR-DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT WITH MECHANICAL CLOSURE SYSTEM; Inventors: Frederick E. Shelton, IV and Christoph L. Gillum   U.S. patent application Ser. No. 11/343,321, now U.S. Patent Application Publication No. 2007/0175955, entitled SURGICAL CUTTING AND FASTENING INSTRUMENT WITH CLOSURE TRIGGER LOCKING MECHANISM; Inventors: Frederick E. Shelton, IV and Kevin R. Doll   U.S. patent application Ser. No. 11/343,563, now U.S. Patent Application Publication No. 2007/0175951, entitled GEARING SELECTOR FOR A POWERED SURGICAL CUTTING AND FASTENING STAPLING INSTRUMENT; Inventors: Frederick E. Shelton, IV, Jeffrey S. Swayze, Eugene L. Timperman   U.S. patent application Ser. No. 11/344,020, now U.S. Pat. No. 7,464,846, entitled SURGICAL INSTRUMENT HAVING A REMOVABLE BATTERY Inventors: Frederick E. Shelton, IV, Kevin R. Doll, Jeffrey S. Swayze and Eugene Timperman   U.S. patent application Ser. No. 11/343,439, now U.S. Pat. No. 7,644,848, entitled ELECTRONIC LOCKOUTS AND SURGICAL INSTRUMENT INCLUDING SAME; Inventors: Jeffrey S. Swayze, Frederick E. Shelton, IV, Kevin R. Doll   U.S. patent application Ser. No. 11/343,547, now U.S. Pat. No. 7,753,904, entitled ENDOSCOPIC SURGICAL INSTRUMENT WITH A HANDLE THAT CAN ARTICULATE WITH RESPECT TO THE SHAFT; Inventors: Frederick E. Shelton, IV, Jeffrey S. Swayze, Mark S. Ortiz, and Leslie M. Fugikawa   U.S. patent application Ser. No. 11/344,021, now U.S. Pat. No. 7,464,849, entitled ELECTRO-MECHANICAL SURGICAL CUTTING AND FASTENING INSTRUMENT HAVING A ROTARY FIRING AND CLOSURE SYSTEM WITH PARALLEL CLOSURE AND ANVIL ALIGNMENT COMPONENTS; Inventors: Frederick E. Shelton, IV, Stephen J. Balek and Eugene L. Timperman   U.S. patent application Ser. No. 11/343,546, now U.S. Patent Application Publication No. 2007/0175950, entitled DISPOSABLE STAPLE CARTRIDGE HAVING AN ANVIL WITH TISSUE LOCATOR FOR USE WITH A SURGICAL CUTTING AND FASTENING INSTRUMENT AND MODULAR END EFFECTOR SYSTEM THEREFOR; Inventors: Frederick E. Shelton, IV, Michael S. Cropper, Joshua M. Broehl, Ryan S. Crisp, Jamison J. Float, Eugene L. Timperman   U.S. patent application Ser. No. 11/343,545, now U.S. Pat. No. 8,708,213, entitled SURGICAL INSTRUMENT HAVING A FEEDBACK SYSTEM; Inventors: Frederick E. Shelton, IV, Jerome R. Morgan, Kevin R. Doll, Jeffrey S. Swayze and Eugene Timperman   

    
    
     BACKGROUND 
     The present invention relates in general to surgical instruments, and more particularly to minimally invasive surgical instruments capable of recording various conditions of the instrument. 
     Endoscopic surgical instruments are often preferred over traditional open surgical devices because 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 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, entitled “SURGICAL STAPLER INSTRUMENT” to Knodel et al., which discloses an endocutter with distinct closing and firing actions. A clinician using this device 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, or multiple firing strokes, depending on the device. Firing the surgical stapler causes severing and stapling of 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 and 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 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. 
     When endoscopic surgical instruments fail, they are often returned to the manufacturer, or other entity, for analysis of the failure. If the failure resulted in a critical class of defect in the instrument, it is necessary for the manufacturer to determine the cause of the failure and determine whether a design change is required. In that case, the manufacturer may spend many hundreds of man-hours analyzing a failed instrument and attempting to reconstruct the conditions under which it failed based only on the damage to the instrument. It can be expensive and very challenging to analyze instrument failures in this way. Also, many of these analyses simply conclude that the failure was due to improper use of the instrument. 
     SUMMARY 
     In various embodiments, a surgical fastening instrument is disclosed. The surgical fastening instrument comprises an end effector cartridge assembly, comprising a first jaw, a second jaw, wherein the first jaw is movable relative to the second iaw between an open position and a closed position, and a fastener cartridge comprising a plurality of fasteners removably stored therein. The surgical fastening instrument further comprises a handle, comprising an electric motor, an actuator configured to operate the electric motor, and a battery configured to supply power to the electric motor. The surgical instrument further comprises, one, a firing member, wherein the electric motor is configured to impart a firing motion to the firing member to eject the fasteners from the fastener cartridge and, two, an electronic lockout system configured to ascertain whether the fastener cartridge is present in the end effector, wherein the electronic lockout system is further configured to permit the electric motor to apply the firing motion to the firing member when the presence of the fastener cartridge has been ascertained and to prevent the electric motor from applying the firing motion to the firing member when the presence of the fastener cartridge has not been ascertained. 
     In various embodiments, a surgical fastening instrument is disclosed. The surgical fastening instrument comprises an end effector cartridge assembly, comprising a first jaw, a second jaw, wherein the first jaw is movable relative to the second jaw between an open position and a closed position, a fastener cartridge body, and a plurality of fasteners removably stored in the fastener cartridge body. The surgical fastening instrument further comprises a handle comprising an actuator, a firing member, wherein the actuator is configured to impart a firing motion to the firing member to eject the fasteners from the fastener cartridge body, and an electronic lockout system configured to permit the actuator to apply the firing motion to the firing member when the end effector cartridge assembly is in an unlocked firable condition and to prevent the actuator from applying the firing motion to the firing member when the end effector cartridge assembly is not in the unlocked firable condition. 
     In various embodiments, a surgical fastening instrument is disclosed. The surgical fastening instrument comprises an end effector cartridge assembly, comprising a first jaw, a second jaw, wherein the first jaw is movable relative to the second jaw between an open position and a closed position, a fastener cartridge body, and a plurality of fasteners removably stored in the fastener cartridge body. The surgical fastening instrument further comprises a handle comprising an electric motor, a firing member, wherein the motor is configured to impart a firing motion to the firing member to eject the fasteners from the fastener cartridge body, and observing means for observing whether the end effector cartridge assembly is in a fire-ready condition. The surgical fastening instrument further comprises permitting means for permitting the motor to apply the firing motion to the firing member when the end effector cartridge assembly is in the fire-ready condition and preventing means for preventing the motor from applying the firing motion to the firing member when the end effector cartridge assembly is not in the fire-ready condition. 
     In various embodiments, a surgical fastening instrument is disclosed. The surgical fastening instrument comprises an end effector cartridge assembly, comprising a first jaw, a second jaw, wherein the first jaw is movable relative to the second jaw between an open position and a closed position, a fastener cartridge body, and a plurality of fasteners removably stored in the fastener cartridge body. The surgical fastening instrument further comprises a handle comprising an electric motor, a firing member, wherein the electric motor is configured to impart a firing motion to the firing member to eject the fasteners from the fastener cartridge body, and means for deriving whether the fasteners are present in the fastener cartridge body, for permitting the electric motor to apply the firing motion to the firing member after the presence of the fasteners have been derived, and for preventing the electric motor from applying the firing motion to the firing member if the presence of the fasteners has not been derived. 
     In various embodiments, a surgical fastening instrument is disclosed. The surgical fastening instrument comprises an end effector cartridge assembly, comprising a first jaw, a second jaw, wherein the first jaw is movable relative to the second jaw between an open position and a closed position, a fastener cartridge body, and a plurality of fasteners removably stored in the fastener cartridge body. The surgical fastening instrument further comprises a handle comprising an electric motor, a firing member, wherein the electric motor is configured to impart a firing motion to the firing member to eject the fasteners from the fastener cartridge body, and controller means for educing whether the fasteners are present in the fastener cartridge body, for operating the electric motor to apply the firing motion to the firing member after the presence of the fasteners has been educed, and for preventing the electric motor from applying the firing motion to the firing member if the presence of the fasteners has not been educed. 
     In various embodiments, a surgical fastening instrument is disclosed. The surgical fastening instrument comprises an end effector cartridge assembly, comprising a first jaw, a second jaw, wherein the first jaw is movable relative to the second jaw between an open position and a closed position, and a fastener cartridge comprising a plurality of fasteners removably stored therein. The surgical fastening instrument further comprises a handle comprising an electric motor, a firing member, wherein the electric motor is configured to impart a firing motion to the firing member to eject the fasteners from the fastener cartridge, means for determining whether the fasteners are present, and means for permitting the electric motor to apply the firing motion to the firing member after the presence of the fasteners has been determined and for inhibiting the electric motor from applying the firing motion to the firing member if the presence of the fasteners has not been determined. 
     In various embodiments, a surgical fastening instrument system is disclosed. The surgical fastening instrument system comprises an end effector, comprising a first jaw and a second jaw, wherein the first jaw is movable relative to the second jaw between an open position and a closed position. The surgical fastening instrument system further comprises a fastener cartridge comprising a plurality of fasteners removably stored therein, a handle comprising an electric motor, and a firing member, wherein the electric motor is configured to impart a firing motion to the firing member to eject the fasteners from the fastener cartridge. The surgical fastening instrument system further comprises means for detecting whether the fastener cartridge is present in the end effector, means for detecting whether the fastener cartridge is unexpended, and means for allowing the electric motor to apply the firing motion to the firing member after the presence of an unexpended fastener cartridge within the end effector has been detected and for preventing the electric motor from applying the firing motion to the firing member if the presence of an unexpended fastener cartridge within the end effector has not been detected. 
    
    
     
       DRAWINGS 
       Various embodiments of the present invention are described herein by way of example in conjunction with the following figures, wherein 
         FIGS. 1 and 2  are perspective views of a surgical cutting and fastening instrument according to various embodiments of the present invention; 
         FIGS. 3-5  are exploded views of an end effector and shaft of the instrument according to various embodiments of the present invention; 
         FIG. 6  is a side view of the end effector according to various embodiments of the present invention; 
         FIG. 7  is an exploded view of the handle of the instrument according to various embodiments of the present invention; 
         FIGS. 8 and 9  are partial perspective views of the handle according to various embodiments of the present invention; 
         FIG. 10  is a side view of the handle according to various embodiments of the present invention; 
         FIGS. 10A and 10B  illustrate a proportional sensor that may be used according to various embodiments of the present invention; 
         FIG. 11  is a schematic diagram of a circuit used in the instrument according to various embodiments of the present invention; 
         FIGS. 12-13  are side views of the handle according to other embodiments of the present invention; 
         FIGS. 14-22  illustrate different mechanisms for locking the closure trigger according to various embodiments of the present invention; 
         FIGS. 23A-B  show a universal joint (“u-joint”) that may be employed at the articulation point of the instrument according to various embodiments of the present invention; 
         FIGS. 24A-B  shows a torsion cable that may be employed at the articulation point of the instrument according to various embodiments of the present invention; 
         FIGS. 25-31  illustrate a surgical cutting and fastening instrument with power assist according to another embodiment of the present invention; 
         FIGS. 32-36  illustrate a surgical cutting and fastening instrument with power assist according to yet another embodiment of the present invention; 
         FIGS. 37-40  illustrate a surgical cutting and fastening instrument with tactile feedback to embodiments of the present invention; 
         FIG. 41  illustrates an exploded view of an end effector and shaft of the instrument according to various embodiments of the present invention; 
         FIG. 42  illustrates a side view of the handle of a mechanically instrument according to various embodiments of the present invention; 
         FIG. 43  illustrates an exploded view of the handle of the mechanically actuated instrument of  FIG. 42 ; 
         FIG. 44  illustrates a block diagram of a recording system for recording various conditions of the instrument according to various embodiments of the present invention; 
         FIGS. 45-46  illustrate cut away side views of a handle of the instrument showing various sensors according to various embodiments of the present invention; 
         FIG. 47  illustrates the end effector of the instrument showing various sensors according to various embodiments of the present invention; 
         FIG. 48  illustrates a firing bar of the instrument including a sensor according to various embodiments of the present invention; 
         FIG. 49  illustrates a side view of the handle, end effector, and firing bar of the instrument showing a sensor according to various embodiments of the present invention; 
         FIG. 50  illustrates an exploded view of the staple channel and portions of a staple cartridge of the instrument showing various sensors according to various embodiments of the present invention; 
         FIG. 51  illustrates a top down view of the staple channel of the instrument showing various sensors according to various embodiments of the present invention; 
         FIGS. 52A and 52B  illustrate a flow chart showing a method for operating the instrument according to various embodiments; and 
         FIG. 53  illustrates a memory chart showing exemplary recorded conditions of the instrument according to various embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1 and 2  depict a surgical cutting and fastening instrument  10  according to various embodiments of the present invention. The illustrated embodiment is an endoscopic surgical instrument  10  and in general, the embodiments of the instrument  10  described herein are endoscopic surgical cutting and fastening instruments. It should be noted, however, that according to other embodiments of the present invention, the instrument  10  may be a non-endoscopic surgical cutting instrument, such as a laparoscopic instrument. 
     The surgical instrument  10  depicted in  FIGS. 1 and 2  comprises a handle  6 , a shaft  8 , and an articulating end effector  12  pivotally connected to the shaft  8  at an articulation pivot  14 . An articulation control  16  may be provided adjacent to the handle  6  to effect rotation of the end effector  12  about the articulation pivot  14 . It will be appreciated that various embodiments may include a non-pivoting end effector, and therefore may not have an articulation pivot  14  or articulation control  16 . Also, in the illustrated embodiment, the end effector  12  is configured to act as an endocutter for clamping, severing and stapling tissue, although, in other embodiments, different types of end effectors may be used, such as end effectors for other types of surgical devices, such as graspers, cutters, staplers, clip appliers, access devices, drug/gene therapy devices, ultrasound, RF or laser devices, etc. 
     The handle  6  of the instrument  10  may include a closure trigger  18  and a firing trigger  20  for actuating the end effector  12 . It will be appreciated that instruments having end effectors directed to different surgical tasks may have different numbers or types of triggers or other suitable controls for operating the end effector  12 . The end effector  12  is shown separated from the handle  6  by a preferably elongate shaft  8 . In one embodiment, a clinician or operator of the instrument  10  may articulate the end effector  12  relative to the shaft  8  by utilizing the articulation control  16 , as described in more detail in pending U.S. patent application Ser. No. 11/329,020, filed Jan. 10, 2006, entitled “Surgical Instrument Having An Articulating End Effector,” by Geoffrey C. Hueil et al., which is incorporated herein by reference. 
     The end effector  12  includes in this example, among other things, a staple channel  22  and a pivotally translatable clamping member, such as an anvil  24 , which are maintained at a spacing that assures effective stapling and severing of tissue clamped in the end effector  12 . The handle  6  includes a pistol grip  26  toward which a closure trigger  18  is pivotally drawn by the clinician to cause clamping or closing of the anvil  24  towards the staple channel  22  of the end effector  12  to thereby clamp tissue positioned between the anvil  24  and channel  22 . The firing trigger  20  is farther outboard of the closure trigger  18 . Once the closure trigger  18  is locked in the closure position as further described below, the firing trigger  20  may rotate slightly toward the pistol grip  26  so that it can be reached by the operator using one hand. Then the operator may pivotally draw the firing trigger  20  toward the pistol grip  26  to cause the stapling and severing of clamped tissue in the end effector  12 . In other embodiments, different types of clamping members besides the anvil  24  could be used, such as, for example, an opposing jaw, etc. 
     It will be appreciated that the terms “proximal” and “distal” are used herein with reference to a clinician gripping the handle  6  of an instrument  10 . Thus, the end effector  12  is distal with respect to the more proximal handle  6 . 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 closure trigger  18  may be actuated first. Once the clinician is satisfied with the positioning of the end effector  12 , the clinician may draw back the closure trigger  18  to its fully closed, locked position proximate to the pistol grip  26 . The firing trigger  20  may then be actuated. The firing trigger  20  returns to the open position (shown in  FIGS. 1 and 2 ) when the clinician removes pressure, as described more fully below. A release button on the handle  6 , when depressed may release the locked closure trigger  18 . The release button may be implemented in various forms such as, for example, release button  30  shown in  FIGS. 42-43 , slide release button  160  shown in  FIG. 14 , and/or button  172  shown in  FIG. 16 . 
       FIGS. 3-6  show embodiments of a rotary-driven end effector  12  and shaft  8  according to various embodiments.  FIG. 3  is an exploded view of the end effector  12  according to various embodiments. As shown in the illustrated embodiment, the end effector  12  may include, in addition to the previously-mentioned channel  22  and anvil  24 , a cutting instrument  32 , a sled  33 , a staple cartridge  34  that is removably seated in the channel  22 , and a helical screw shaft  36 . The cutting instrument  32  may be, for example, a knife. The anvil  24  may be pivotably opened and closed at pivot pins  25  connected to the proximate end of the channel  22 . The anvil  24  may also include a tab  27  at its proximate end that is inserted into a component of the mechanical closure system (described further below) to open and close the anvil  24 . When the closure trigger  18  is actuated, that is, drawn in by a user of the instrument  10 , the anvil  24  may pivot about the pivot pins  25  into the clamped or closed position. If clamping of the end effector  12  is satisfactory, the operator may actuate the firing trigger  20 , which, as explained in more detail below, causes the knife  32  and sled  33  to travel longitudinally along the channel  22 , thereby cutting tissue clamped within the end effector  12 . The movement of the sled  33  along the channel  22  causes the staples (not shown) of the staple cartridge  34  to be driven through the severed tissue and against the closed anvil  24 , which turns the staples to fasten the severed tissue. In various embodiments, the sled  33  may be an integral component of the cartridge  34 . U.S. Pat. No. 6,978,921, entitled “SURGICAL STAPLING INSTRUMENT INCORPORATING AN E-BEAM FIRING MECHANISM” to Shelton, IV et al., which is incorporated herein by reference, provides more details about such two-stroke cutting and fastening instruments. The sled  33  may be part of the cartridge  34 , such that when the knife  32  retracts following the cutting operation, the sled  33  does not retract. 
     It should be noted that although the embodiments of the instrument  10  described herein employ an end effector  12  that staples the severed tissue, in other embodiments different techniques for fastening or sealing the severed tissue may be used. For example, end effectors that use RF energy or adhesives to fasten the severed tissue may also be used. U.S. Pat. No. 5,709,680 entitled “ELECTROSURGICAL HEMOSTATIC DEVICE” to Yates et al., and U.S. Pat. No. 5,688,270 entitled “ELECTOSURGICAL HEMOSTATIC DEVICE WITH RECESSED AND/OR OFFSET ELECTRODES” to Yates et al. which are incorporated herein by reference, disclose an endoscopic cutting instrument that uses RF energy to seal the severed tissue. U.S. patent application Ser. No. 11/267,811 to Jerome R. Morgan, et. al, and U.S. patent application Ser. No. 11/267,383 to Frederick E. Shelton, IV, et. al, which are also incorporated herein by reference, disclose cutting instruments that uses adhesives to fasten the severed tissue. Accordingly, although the description herein refers to cutting/stapling operations and the like below, it should be recognized that this is an exemplary embodiment and is not meant to be limiting. Other tissue fastening techniques may also be used. 
       FIGS. 4 and 5  are exploded views and  FIG. 6  is a side view of the end effector  12  and shaft  8  according to various embodiments. As shown in the illustrated embodiment, the shaft  8  may include a proximate closure tube  40  and a distal closure tube  42  pivotably linked by a pivot link  44 . The distal closure tube  42  includes an opening  45  into which the tab  27  on the anvil  24  is inserted in order to open and close the anvil  24 , as further described below. Disposed inside the closure tubes  40 ,  42  may be a proximate spine tube  46 . Disposed inside the proximate spine tube  46  may be a main rotational (or proximate) drive shaft  48  that communicates with a secondary (or distal) drive shaft  50  via a bevel gear assembly  52 . The secondary drive shaft  50  is connected to a drive gear  54  that engages a proximate drive gear  56  of the helical screw shaft  36 . The vertical bevel gear  52   b  may sit and pivot in an opening  57  in the distal end of the proximate spine tube  46 . A distal spine tube  58  may be used to enclose the secondary drive shaft  50  and the drive gears  54 ,  56 . Collectively, the main drive shaft  48 , the secondary drive shaft  50 , and the articulation assembly (e.g., the bevel gear assembly  52   a - c ) are sometimes referred to herein as the “main drive shaft assembly.” 
     A bearing  38 , positioned at a distal end of the staple channel  22 , receives the helical drive screw  36 , allowing the helical drive screw  36  to freely rotate with respect to the channel  22 . The helical screw shaft  36  may interface a threaded opening (not shown) of the knife  32  such that rotation of the shaft  36  causes the knife  32  to translate distally or proximately (depending on the direction of the rotation) through the staple channel  22 . Accordingly, when the main drive shaft  48  is caused to rotate by actuation of the firing trigger  20  (as explained in more detail below), the bevel gear assembly  52   a - c  causes the secondary drive shaft  50  to rotate, which in turn, because of the engagement of the drive gears  54 ,  56 , causes the helical screw shaft  36  to rotate, which causes the knife driving member  32  to travel longitudinally along the channel  22  to cut any tissue clamped within the end effector  12 . The sled  33  may be made of, for example, plastic, and may have a sloped distal surface. As the sled  33  traverses the channel  22 , the sloped forward surface may push up or drive the staples in the staple cartridge through the clamped tissue and against the anvil  24 . The anvil  24  turns the staples, thereby stapling the severed tissue. When the knife  32  is retracted, the knife  32  and sled  33  may become disengaged, thereby leaving the sled  33  at the distal end of the channel  22 . 
     As described above, because of the lack of user feedback for the cutting/stapling operation, there is a general lack of acceptance among physicians of motor-driven endocutters where the cutting/stapling operation is actuated by merely pressing a button. In contrast, embodiments of the present invention provide a motor-driven endocutter with user-feedback of the deployment, force and/or position of the cutting instrument  32  in end effector  12 . 
       FIGS. 7-10  illustrate an exemplary embodiment of a motor-driven endocutter, and in particular the handle thereof, that provides user-feedback regarding the deployment and loading force of the cutting instrument  32  in the end effector  12 . In addition, the embodiment may use power provided by the user in retracting the firing trigger  20  to power the device (a so-called “power assist” mode). The embodiment may be used with the rotary driven end effector  12  and shaft  8  embodiments described above. As shown in the illustrated embodiment, the handle  6  includes exterior lower side pieces  59 ,  60  and exterior upper side pieces  61 ,  62  that fit together to form, in general, the exterior of the handle  6 . A battery  64 , such as a Li ion battery, may be provided in the pistol grip portion  26  of the handle  6 . The battery  64  powers a motor  65  disposed in an upper portion of the pistol grip portion  26  of the handle  6 . According to various embodiments, the motor  65  may be a DC brushed driving motor having a maximum rotation of, approximately, 5000 RPM. The motor  65  may drive a 90° bevel gear assembly  66  comprising a first bevel gear  68  and a second bevel gear  70 . The bevel gear assembly  66  may drive a planetary gear assembly  72 . The planetary gear assembly  72  may include a pinion gear  74  connected to a drive shaft  76 . The pinion gear  74  may drive a mating ring gear  78  that drives a helical gear drum  80  via a drive shaft  82 . A ring  84  may be threaded on the helical gear drum  80 . Thus, when the motor  65  rotates, the ring  84  is caused to travel along the helical gear drum  80  by means of the interposed bevel gear assembly  66 , planetary gear assembly  72  and ring gear  78 . 
     The handle  6  may also include a run motor sensor  110  (see  FIG. 10 ) in communication with the firing trigger  20  to detect when the firing trigger  20  has been drawn in (or “closed”) toward the pistol grip portion  26  of the handle  6  by the operator to thereby actuate the cutting/stapling operation by the end effector  12 . The sensor  110  may be a proportional sensor such as, for example, a rheostat or variable resistor. When the firing trigger  20  is drawn in, the sensor  110  detects the movement, and sends an electrical signal indicative of the voltage (or power) to be supplied to the motor  65 . When the sensor  110  is a variable resistor or the like, the rotation of the motor  65  may be generally proportional to the amount of movement of the firing trigger  20 . That is, if the operator only draws or closes the firing trigger  20  in a little bit, the rotation of the motor  65  is relatively low. When the firing trigger  20  is fully drawn in (or in the fully closed position), the rotation of the motor  65  is at its maximum. In other words, the harder the user pulls on the firing trigger  20 , the more voltage is applied to the motor  65 , causing greater rates of rotation. 
     The handle  6  may include a middle handle piece  104  adjacent to the upper portion of the firing trigger  20 . The handle  6  also may comprise a bias spring  112  connected between posts on the middle handle piece  104  and the firing trigger  20 . The bias spring  112  may bias the firing trigger  20  to its fully open position. In that way, when the operator releases the firing trigger  20 , the bias spring  112  will pull the firing trigger  20  to its open position, thereby removing actuation of the sensor  110 , thereby stopping rotation of the motor  65 . Moreover, by virtue of the bias spring  112 , any time a user closes the firing trigger  20 , the user will experience resistance to the closing operation, thereby providing the user with feedback as to the amount of rotation exerted by the motor  65 . Further, the operator could stop retracting the firing trigger  20  to thereby remove force from the sensor  100 , to thereby stop the motor  65 . As such, the user may stop the deployment of the end effector  12 , thereby providing a measure of control of the cutting/fastening operation to the operator. 
     The distal end of the helical gear drum  80  includes a distal drive shaft  120  that drives a ring gear  122 , which mates with a pinion gear  124 . The pinion gear  124  is connected to the main drive shaft  48  of the main drive shaft assembly. In that way, rotation of the motor  65  causes the main drive shaft assembly to rotate, which causes actuation of the end effector  12 , as described above. 
     The ring  84  threaded on the helical gear drum  80  may include a post  86  that is disposed within a slot  88  of a slotted arm  90 . The slotted arm  90  has an opening  92  its opposite end  94  that receives a pivot pin  96  that is connected between the handle exterior side pieces  59 ,  60 . The pivot pin  96  is also disposed through an opening  100  in the firing trigger  20  and an opening  102  in the middle handle piece  104 . 
     In addition, the handle  6  may include a reverse motor sensor (or end-of-stroke sensor)  130  and a stop motor (or beginning-of-stroke) sensor  142 . In various embodiments, the reverse motor sensor  130  may be a limit switch located at the distal end of the helical gear drum  80  such that the ring  84  threaded on the helical gear drum  80  contacts and trips the reverse motor sensor  130  when the ring  84  reaches the distal end of the helical gear drum  80 . The reverse motor sensor  130 , when activated, sends a signal to the motor  65  to reverse its rotation direction, thereby withdrawing the knife  32  of the end effector  12  following the cutting operation. 
     The stop motor sensor  142  may be, for example, a normally-closed limit switch. In various embodiments, it may be located at the proximate end of the helical gear drum  80  so that the ring  84  trips the switch  142  when the ring  84  reaches the proximate end of the helical gear drum  80 . 
     In operation, when an operator of the instrument  10  pulls back the firing trigger  20 , the sensor  110  detects the deployment of the firing trigger  20  and sends a signal to the motor  65  to cause forward rotation of the motor  65 , for example, at a rate proportional to how hard the operator pulls back the firing trigger  20 . The forward rotation of the motor  65  in turn causes the ring gear  78  at the distal end of the planetary gear assembly  72  to rotate, thereby causing the helical gear drum  80  to rotate, causing the ring  84  threaded on the helical gear drum  80  to travel distally along the helical gear drum  80 . The rotation of the helical gear drum  80  also drives the main drive shaft assembly as described above, which in turn causes deployment of the knife  32  in the end effector  12 . That is, the knife  32  and sled  33  are caused to traverse the channel  22  longitudinally, thereby cutting tissue clamped in the end effector  12 . Also, the stapling operation of the end effector  12  is caused to happen in embodiments where a stapling-type end effector  12  is used. 
     By the time the cutting/stapling operation of the end effector  12  is complete, the ring  84  on the helical gear drum  80  will have reached the distal end of the helical gear drum  80 , thereby causing the reverse motor sensor  130  to be tripped, which sends a signal to the motor  65  to cause the motor  65  to reverse its rotation. This in turn causes the knife  32  to retract, and also causes the ring  84  on the helical gear drum  80  to move back to the proximate end of the helical gear drum  80 . 
     The middle handle piece  104  includes a backside shoulder  106  that engages the slotted arm  90  as best shown in  FIGS. 8 and 9 . The middle handle piece  104  also has a forward motion stop  107  that engages the firing trigger  20 . The movement of the slotted arm  90  is controlled, as explained above, by rotation of the motor  65 . When the slotted arm  90  rotates counter clockwise as the ring  84  travels from the proximate end of the helical gear drum  80  to the distal end, the middle handle piece  104  will be free to rotate counter clockwise. Thus, as the user draws in the firing trigger  20 , the firing trigger  20  will engage the forward motion stop  107  of the middle handle piece  104 , causing the middle handle piece  104  to rotate counter clockwise. Due to the backside shoulder  106  engaging the slotted arm  90 , however, the middle handle piece  104  will only be able to rotate counter clockwise as far as the slotted arm  90  permits. In that way, if the motor  65  should stop rotating for some reason, the slotted arm  90  will stop rotating, and the user will not be able to further draw in the firing trigger  20  because the middle handle piece  104  will not be free to rotate counter clockwise due to the slotted arm  90 . 
       FIGS. 10A and 10B  illustrate two states of a variable sensor that may be used as the run motor sensor  110  according to various embodiments of the present invention. The sensor  110  may include a face portion  280 , a first electrode (A)  282 , a second electrode (B)  284 , and a compressible dielectric material  286  between the electrodes  282 ,  284 , such as, for example, an electroactive polymer (EAP). The sensor  110  may be positioned such that the face portion  280  contacts the firing trigger  20  when retracted. Accordingly, when the firing trigger  20  is retracted, the dielectric material  286  is compressed, as shown in  FIG. 10B , such that the electrodes  282 ,  284  are closer together. Since the distance “b” between the electrodes  282 ,  284  is directly related to the impedance between the electrodes  282 ,  284 , the greater the distance the more impedance, and the closer the distance the less impedance. In that way, the amount that the dielectric  286  is compressed due to retraction of the firing trigger  20  (denoted as force “F” in  FIG. 42 ) is proportional to the impedance between the electrodes  282 ,  284 , which can be used to proportionally control the motor  65 . 
     Components of an exemplary closure system for closing (or clamping) the anvil  24  of the end effector  12  by retracting the closure trigger  18  are also shown in  FIGS. 7-10 . In the illustrated embodiment, the closure system includes a yoke  250  connected to the closure trigger  18  by a pivot pin  251  inserted through aligned openings in both the closure trigger  18  and the yoke  250 . A pivot pin  252 , about which the closure trigger  18  pivots, is inserted through another opening in the closure trigger  18  which is offset from where the pin  251  is inserted through the closure trigger  18 . Thus, retraction of the closure trigger  18  causes the upper part of the closure trigger  18 , to which the yoke  250  is attached via the pin  251 , to rotate counterclockwise. The distal end of the yoke  250  is connected, via a pin  254 , to a first closure bracket  256 . The first closure bracket  256  connects to a second closure bracket  258 . Collectively, the closure brackets  256 ,  258  define an opening in which the proximate end of the proximate closure tube  40  (see  FIG. 4 ) is seated and held such that longitudinal movement of the closure brackets  256 ,  258  causes longitudinal motion by the proximate closure tube  40 . The instrument  10  also includes a closure rod  260  disposed inside the proximate closure tube  40 . The closure rod  260  may include a window  261  into which a post  263  on one of the handle exterior pieces, such as exterior lower side piece  59  in the illustrated embodiment, is disposed to fixedly connect the closure rod  260  to the handle  6 . In that way, the proximate closure tube  40  is capable of moving longitudinally relative to the closure rod  260 . The closure rod  260  may also include a distal collar  267  that fits into a cavity  269  in proximate spine tube  46  and is retained therein by a cap  271  (see  FIG. 4 ). 
     In operation, when the yoke  250  rotates due to retraction of the closure trigger  18 , the closure brackets  256 ,  258  cause the proximate closure tube  40  to move distally (i.e., away from the handle end of the instrument  10 ), which causes the distal closure tube  42  to move distally, which causes the anvil  24  to rotate about the pivot pins  25  into the clamped or closed position. When the closure trigger  18  is unlocked from the locked position, the proximate closure tube  40  is caused to slide proximately, which causes the distal closure tube  42  to slide proximately, which, by virtue of the tab  27  being inserted in the window  45  of the distal closure tube  42 , causes the anvil  24  to pivot about the pivot pins  25  into the open or unclamped position. In that way, by retracting and locking the closure trigger  18 , an operator may clamp tissue between the anvil  24  and channel  22 , and may unclamp the tissue following the cutting/stapling operation by unlocking the closure trigger  20  from the locked position. 
       FIG. 11  is a schematic diagram of an electrical circuit of the instrument  10  according to various embodiments of the present invention. When an operator initially pulls in the firing trigger  20  after locking the closure trigger  18 , the sensor  110  is activated, allowing current to flow there through. If the normally-open reverse motor sensor switch  130  is open (meaning the end of the end effector stroke has not been reached), current will flow to a single pole, double throw relay  132 . Since the reverse motor sensor switch  130  is not closed, the inductor  134  of the relay  132  will not be energized, so the relay  132  will be in its non-energized state. The circuit also includes a cartridge lockout sensor  136 . If the end effector  12  includes a staple cartridge  34 , the sensor  136  will be in the closed state, allowing current to flow. Otherwise, if the end effector  12  does not include a staple cartridge  34 , the sensor  136  will be open, thereby preventing the battery  64  from powering the motor  65 . 
     When the staple cartridge  34  is present, the sensor  136  is closed, which energizes a single pole, single throw relay  138 . When the relay  138  is energized, current flows through the relay  136 , through the variable resistor sensor  110 , and to the motor  65  via a double pole, double throw relay  140 , thereby powering the motor  65  and allowing it to rotate in the forward direction. 
     When the end effector  12  reaches the end of its stroke, the reverse motor sensor  130  will be activated, thereby closing the switch  130  and energizing the relay  134 . This causes the relay  134  to assume its energized state (not shown in  FIG. 13 ), which causes current to bypass the cartridge lockout sensor  136  and variable resistor  110 , and instead causes current to flow to both the normally-closed double pole, double throw relay  142  and back to the motor  65 , but in a manner, via the relay  140 , that causes the motor  65  to reverse its rotational direction. 
     Because the stop motor sensor switch  142  is normally-closed, current will flow back to the relay  134  to keep it closed until the switch  142  opens. When the knife  32  is fully retracted, the stop motor sensor switch  142  is activated, causing the switch  142  to open, thereby removing power from the motor  65 . 
     In other embodiments, rather than a proportional-type sensor  110 , an on-off type sensor could be used. In such embodiments, the rate of rotation of the motor  65  would not be proportional to the force applied by the operator. Rather, the motor  65  would generally rotate at a constant rate. But the operator would still experience force feedback because the firing trigger  20  is geared into the gear drive train. 
       FIG. 12  is a side-view of the handle  6  of a power-assist motorized endocutter according to another embodiment. The embodiment of  FIG. 12  is similar to that of  FIGS. 7-10  except that in the embodiment of  FIG. 12 , there is no slotted arm connected to the ring  84  threaded on the helical gear drum  80 . Instead, in the embodiment of  FIG. 12 , the ring  84  includes a sensor portion  114  that moves with the ring  84  as the ring  84  advances down (and back) on the helical gear drum  80 . The sensor portion  114  includes a notch  116 . The reverse motor sensor  130  may be located at the distal end of the notch  116  and the stop motor sensor  142  may be located at the proximate end of the notch  116 . As the ring  84  moves down the helical gear drum  80  (and back), the sensor portion  114  moves with it. Further, as shown in  FIG. 12 , the middle piece  104  may have an arm  118  that extends into the notch  12 . 
     In operation, as an operator of the instrument  10  retracts in the firing trigger  20  toward the pistol grip  26 , the run motor sensor  110  detects the motion and sends a signal to power the motor  65 , which causes, among other things, the helical gear drum  80  to rotate. As the helical gear drum  80  rotates, the ring  84  threaded on the helical gear drum  80  advances (or retracts, depending on the rotation). Also, due to the pulling in of the firing trigger  20 , the middle piece  104  is caused to rotate counter clockwise with the firing trigger  20  due to the forward motion stop  107  that engages the firing trigger  20 . The counter clockwise rotation of the middle piece  104  cause the arm  118  to rotate counter clockwise with the sensor portion  114  of the ring  84  such that the arm  118  stays disposed in the notch  116 . When the ring  84  reaches the distal end of the helical gear drum  80 , the arm  118  will contact and thereby trip the reverse motor sensor  130 . Similarly, when the ring  84  reaches the proximate end of the helical gear drum  80 , the arm will contact and thereby trip the stop motor sensor  142 . Such actions may reverse and stop the motor  65 , respectively as described above. 
       FIG. 13  is a side-view of the handle  6  of a power-assist motorized endocutter according to another embodiment. The embodiment of  FIG. 13  is similar to that of  FIGS. 7-10  except that in the embodiment of  FIG. 13 , there is no slot in the arm  90 . Instead, the ring  84  threaded on the helical gear drum  80  includes a vertical channel  126 . Instead of a slot, the arm  90  includes a post  128  that is disposed in the channel  126 . As the helical gear drum  80  rotates, the ring  84  threaded on the helical gear drum  80  advances (or retracts, depending on the rotation). The arm  90  rotates counter clockwise as the ring  84  advances due to the post  128  being disposed in the channel  126 , as shown in  FIG. 13 . 
     As mentioned above, in using a two-stroke motorized instrument, the operator first pulls back and locks the closure trigger  18 .  FIGS. 14 and 15  show one embodiment of a way to lock the closure trigger  18  to the pistol grip portion  26  of the handle  6 . In the illustrated embodiment, the pistol grip portion  26  includes a hook  150  that is biased to rotate counter clockwise about a pivot point  151  by a torsion spring  152 . Also, the closure trigger  18  includes a closure bar  154 . As the operator draws in the closure trigger  18 , the closure bar  154  engages a sloped portion  156  of the hook  150 , thereby rotating the hook  150  upward (or clockwise in  FIGS. 14-15 ) until the closure bar  154  completely passes the sloped portion  156  passes into a recessed notch  158  of the hook  150 , which locks the closure trigger  18  in place. The operator may release the closure trigger  18  by pushing down on a slide button release  160  on the back or opposite side of the pistol grip portion  26 . Pushing down the slide button release  160  rotates the hook  150  clockwise such that the closure bar  154  is released from the recessed notch  158 . 
       FIG. 16  shows another closure trigger locking mechanism according to various embodiments. In the embodiment of  FIG. 16 , the closure trigger  18  includes a wedge  160  having an arrow-head portion  161 . The arrow-head portion  161  is biased downward (or clockwise) by a leaf spring  162 . The wedge  160  and leaf spring  162  may be made from, for example, molded plastic. When the closure trigger  18  is retracted, the arrow-head portion  161  is inserted through an opening  164  in the pistol grip portion  26  of the handle  6 . A lower chamfered surface  166  of the arrow-head portion  161  engages a lower sidewall  168  of the opening  164 , forcing the arrow-head portion  161  to rotate counter clockwise. Eventually the lower chamfered surface  166  fully passes the lower sidewall  168 , removing the counter clockwise force on the arrow-head portion  161 , causing the lower sidewall  168  to slip into a locked position in a notch  170  behind the arrow-head portion  161 . 
     To unlock the closure trigger  18 , a user presses down on a button  172  on the opposite side of the closure trigger  18 , causing the arrow-head portion  161  to rotate counter clockwise and allowing the arrow-head portion  161  to slide out of the opening  164 . 
       FIGS. 17-22  show a closure trigger locking mechanism according to another embodiment. As shown in this embodiment, the closure trigger  18  includes a flexible longitudinal arm  176  that includes a lateral pin  178  extending therefrom. The arm  176  and pin  178  may be made from molded plastic, for example. The pistol grip portion  26  of the handle  6  includes an opening  180  with a laterally extending wedge  182  disposed therein. When the closure trigger  18  is retracted, the pin  178  engages the wedge  182 , and the pin  178  is forced downward (i.e., the arm  176  is rotated clockwise) by the lower surface  184  of the wedge  182 , as shown in  FIGS. 17 and 18 . When the pin  178  fully passes the lower surface  184 , the clockwise force on the arm  176  is removed, and the pin  178  is rotated counter clockwise such that the pin  178  comes to rest in a notch  186  behind the wedge  182 , as shown in  FIG. 19 , thereby locking the closure trigger  18 . The pin  178  is further held in place in the locked position by a flexible stop  188  extending from the wedge  184 . 
     To unlock the closure trigger  18 , the operator may further squeeze the closure trigger  18 , causing the pin  178  to engage a sloped backwall  190  of the opening  180 , forcing the pin  178  upward past the flexible stop  188 , as shown in  FIGS. 20 and 21 . The pin  178  is then free to travel out an upper channel  192  in the opening  180  such that the closure trigger  18  is no longer locked to the pistol grip portion  26 , as shown in  FIG. 22 . 
       FIGS. 23A-B  show a universal joint (“u-joint”)  195 . The second piece  195 - 2  of the u-joint  195  rotates in a horizontal plane in which the first piece  195 - 1  lies.  FIG. 23A  shows the u-joint  195  in a linear (180°) orientation and  FIG. 23B  shows the u-joint  195  at approximately a 150° orientation. The u-joint  195  may be used instead of the bevel gears  52   a - c  (see  FIG. 4 , for example) at the articulation point  14  of the main drive shaft assembly to articulate the end effector  12 .  FIGS. 24A-B  show a torsion cable  197  that may be used in lieu of both the bevel gears  52   a - c  and the u-joint  195  to realize articulation of the end effector  12 . 
       FIGS. 25-31  illustrate another embodiment of a motorized, two-stroke surgical cutting and fastening instrument  10  with power assist according to another embodiment of the present invention. The embodiment of  FIGS. 25-31  is similar to that of  FIGS. 6-10  except that instead of the helical gear drum  80 , the embodiment of  FIGS. 23-28  includes an alternative gear drive assembly. The embodiment of  FIGS. 25-31  includes a gear box assembly  200  including a number of gears disposed in a frame  201 , wherein the gears are connected between the planetary gear  72  and the pinion gear  124  at the proximate end of the drive shaft  48 . As explained further below, the gear box assembly  200  provides feedback to the user via the firing trigger  20  regarding the deployment and loading force of the end effector  12 . Also, the user may provide power to the system via the gear box assembly  200  to assist the deployment of the end effector  12 . In that sense, like the embodiments described above, the embodiment of  FIGS. 23-32  is another power assist motorized instrument  10  that provides feedback to the user regarding the loading force experienced by the instrument. 
     In the illustrated embodiment, the firing trigger  20  includes two pieces: a main body portion  202  and a stiffening portion  204 . The main body portion  202  may be made of plastic, for example, and the stiffening portion  204  may be made out of a more rigid material, such as metal. In the illustrated embodiment, the stiffening portion  204  is adjacent to the main body portion  202 , but according to other embodiments, the stiffening portion  204  could be disposed inside the main body portion  202 . A pivot pin  207  may be inserted through openings in the firing trigger pieces  202 ,  204  and may be the point about which the firing trigger  20  rotates. In addition, a spring  222  may bias the firing trigger  20  to rotate in a counter clockwise direction. The spring  222  may have a distal end connected to a pin  224  that is connected to the pieces  202 ,  204  of the firing trigger  20 . The proximate end of the spring  222  may be connected to one of the handle exterior lower side pieces  59 ,  60 . 
     In the illustrated embodiment, both the main body portion  202  and the stiffening portion  204  includes gear portions  206 ,  208  (respectively) at their upper end portions. The gear portions  206 ,  208  engage a gear in the gear box assembly  200 , as explained below, to drive the main drive shaft assembly and to provide feedback to the user regarding the deployment of the end effector  12 . 
     The gear box assembly  200  may include as shown, in the illustrated embodiment, six (6) gears. A first gear  210  of the gear box assembly  200  engages the gear portions  206 ,  208  of the firing trigger  20 . In addition, the first gear  210  engages a smaller second gear  212 , the smaller second gear  212  being coaxial with a large third gear  214 . The third gear  214  engages a smaller fourth gear  216 , the smaller fourth gear being coaxial with a fifth gear  218 . The fifth gear  218  is a 90° bevel gear that engages a mating 90° bevel gear  220  (best shown in  FIG. 31 ) that is connected to the pinion gear  124  that drives the main drive shaft  48 . 
     In operation, when the user retracts the firing trigger  20 , a run motor sensor (not shown) is activated, which may provide a signal to the motor  65  to rotate at a rate proportional to the extent or force with which the operator is retracting the firing trigger  20 . This causes the motor  65  to rotate at a speed proportional to the signal from the sensor. The sensor is not shown for this embodiment, but it could be similar to the run motor sensor  110  described above. The sensor could be located in the handle  6  such that it is depressed when the firing trigger  20  is retracted. Also, instead of a proportional-type sensor, an on/off type sensor may be used. 
     Rotation of the motor  65  causes the bevel gears  68 ,  70  to rotate, which causes the planetary gear  72  to rotate, which causes, via the drive shaft  76 , the ring gear  122  to rotate. The ring gear  122  meshes with the pinion gear  124 , which is connected to the main drive shaft  48 . Thus, rotation of the pinion gear  124  drives the main drive shaft  48 , which causes actuation of the cutting/stapling operation of the end effector  12 . 
     Forward rotation of the pinion gear  124  in turn causes the bevel gear  220  to rotate, which causes, by way of the rest of the gears of the gear box assembly  200 , the first gear  210  to rotate. The first gear  210  engages the gear portions  206 ,  208  of the firing trigger  20 , thereby causing the firing trigger  20  to rotate counter clockwise when the motor  65  provides forward drive for the end effector  12  (and to rotate counter clockwise when the motor  65  rotates in reverse to retract the end effector  12 ). In that way, the user experiences feedback regarding loading force and deployment of the end effector  12  by way of the user&#39;s grip on the firing trigger  20 . Thus, when the user retracts the firing trigger  20 , the operator will experience a resistance related to the load force experienced by the end effector  12 . Similarly, when the operator releases the firing trigger  20  after the cutting/stapling operation so that it can return to its original position, the user will experience a clockwise rotation force from the firing trigger  20  that is generally proportional to the reverse speed of the motor  65 . 
     It should also be noted that in this embodiment the user can apply force (either in lieu of or in addition to the force from the motor  65 ) to actuate the main drive shaft assembly (and hence the cutting/stapling operation of the end effector  12 ) through retracting the firing trigger  20 . That is, retracting the firing trigger  20  causes the gear portions  206 ,  208  to rotate counter clockwise, which causes the gears of the gear box assembly  200  to rotate, thereby causing the pinion gear  124  to rotate, which causes the main drive shaft  48  to rotate. 
     Although not shown in  FIGS. 25-31 , the instrument  10  may further include reverse motor and stop motor sensors. As described above, the reverse motor and stop motor sensors may detect, respectively, the end of the cutting stroke (full deployment of the knife  32 ) and the end of retraction operation (full retraction of the knife  32 ). A similar circuit to that described above in connection with  FIG. 11  may be used to appropriately power the motor  65 . 
       FIGS. 32-36  illustrate a two-stroke, motorized surgical cutting and fastening instrument  10  with power assist according to another embodiment. The embodiment of  FIGS. 32-36  is similar to that of  FIGS. 25-31  except that in the embodiment of  FIGS. 32-36 , the firing trigger  20  includes a lower portion  228  and an upper portion  230 . Both portions  228 ,  230  are connected to and pivot about a pivot pin  207  that is disposed through each portion  228 ,  230 . The upper portion  230  includes a gear portion  232  that engages the first gear  210  of the gear box assembly  200 . The spring  222  is connected to the upper portion  230  such that the upper portion is biased to rotate in the clockwise direction. The upper portion  230  may also include a lower arm  234  that contacts an upper surface of the lower portion  228  of the firing trigger  20  such that when the upper portion  230  is caused to rotate clockwise the lower portion  228  also rotates clockwise, and when the lower portion  228  rotates counter clockwise the upper portion  230  also rotates counter clockwise. Similarly, the lower portion  228  includes a rotational stop  238  that engages a shoulder of the upper portion  230 . In that way, when the upper portion  230  is caused to rotate counter clockwise the lower portion  228  also rotates counter clockwise, and when the lower portion  228  rotates clockwise the upper portion  230  also rotates clockwise. 
     The illustrated embodiment also includes the run motor sensor  110  that communicates a signal to the motor  65  that, in various embodiments, may cause the motor  65  to rotate at a speed proportional to the force applied by the operator when retracting the firing trigger  20 . The sensor  110  may be, for example, a rheostat or some other variable resistance sensor, as explained herein. In addition, the instrument  10  may include reverse motor sensor  130  that is tripped or switched when contacted by a front face  242  of the upper portion  230  of the firing trigger  20 . When activated, the reverse motor sensor  130  sends a signal to the motor  65  to reverse direction. Also, the instrument  10  may include a stop motor sensor  142  that is tripped or actuated when contacted by the lower portion  228  of the firing trigger  20 . When activated, the stop motor sensor  142  sends a signal to stop the reverse rotation of the motor  65 . 
     In operation, when an operator retracts the closure trigger  18  into the locked position, the firing trigger  20  is retracted slightly (through mechanisms known in the art, including U.S. Pat. No. 6,978,921 to Frederick Shelton, IV et. al and U.S. Pat. No. 6,905,057 to Jeffery S. Swayze et. al, which are incorporated herein by reference) so that the user can grasp the firing trigger  20  to initiate the cutting/stapling operation, as shown in  FIGS. 32 and 33 . At that point, as shown in  FIG. 33 , the gear portion  232  of the upper portion  230  of the firing trigger  20  moves into engagement with the first gear  210  of the gear box assembly  200 . When the operator retracts the firing trigger  20 , according to various embodiments, the firing trigger  20  may rotate a small amount, such as five degrees, before tripping the run motor sensor  110 , as shown in  FIG. 34 . Activation of the sensor  110  causes the motor  65  to forward rotate at a rate proportional to the retraction force applied by the operator. The forward rotation of the motor  65  causes, as described above, the main drive shaft  48  to rotate, which causes the knife  32  in the end effector  12  to be deployed (i.e., begin traversing the channel  22 ). Rotation of the pinion gear  124 , which is connected to the main drive shaft  48 , causes the gears  210 - 220  in the gear box assembly  200  to rotate. Since the first gear  210  is in engagement with the gear portion  232  of the upper portion  230  of the firing trigger  20 , the upper portion  232  is caused to rotate counter clockwise, which causes the lower portion  228  to also rotate counter clockwise. 
     When the knife  32  is fully deployed (i.e., at the end of the cutting stroke), the front face  242  of the upper portion  230  trips the reverse motor sensor  130 , which sends a signal to the motor  65  to reverse rotational directional. This causes the main drive shaft assembly to reverse rotational direction to retract the knife  32 . Reverse rotation of the main drive shaft assembly also causes the gears  210 - 220  in the gear box assembly to reverse direction, which causes the upper portion  230  of the firing trigger  20  to rotate clockwise, which causes the lower portion  228  of the firing trigger  20  to rotate clockwise until the lower portion  228  trips or actuates the stop motor sensor  142  when the knife  32  is fully retracted, which causes the motor  65  to stop. In that way, the user experiences feedback regarding deployment of the end effector  12  by way of the user&#39;s grip on the firing trigger  20 . Thus, when the user retracts the firing trigger  20 , the operator will experience a resistance related to the deployment of the end effector  12  and, in particular, to the loading force experienced by the knife  32 . Similarly, when the operator releases the firing trigger  20  after the cutting/stapling operation so that it can return to its original position, the user will experience a clockwise rotation force from the firing trigger  20  that is generally proportional to the reverse speed of the motor  65 . 
     It should also be noted that in this embodiment the user can apply force (either in lieu of or in addition to the force from the motor  65 ) to actuate the main drive shaft assembly (and hence the cutting/stapling operation of the end effector  12 ) through retracting the firing trigger  20 . That is, retracting the firing trigger  20  causes the gear portion  232  of the upper portion  230  to rotate counter clockwise, which causes the gears of the gear box assembly  200  to rotate, thereby causing the pinion gear  124  to rotate, which causes the main drive shaft assembly to rotate. 
     The above-described embodiments employed power-assist user feedback systems, with or without adaptive control (e.g., using a sensor  110 ,  130 , and  142  outside of the closed loop system of the motor  65 , gear drive train, and end effector  12 ) for a two-stroke, motorized surgical cutting and fastening instrument. That is, force applied by the user in retracting the firing trigger  20  may be added to the force applied by the motor  65  by virtue of the firing trigger  20  being geared into (either directly or indirectly) the gear drive train between the motor  65  and the main drive shaft  48 . In other embodiments of the present invention, the user may be provided with tactile feedback regarding the position of the knife  32  in the end effector, but without having the firing trigger  20  geared into the gear drive train.  FIGS. 37-40  illustrate a motorized surgical cutting and fastening instrument with such a tactile position feedback system. 
     In the illustrated embodiment of  FIGS. 37-40 , the firing trigger  20  may have a lower portion  228  and an upper portion  230 , similar to the instrument  10  shown in  FIGS. 32-36 . Unlike the embodiment of  FIG. 32-36 , however, the upper portion  230  does not have a gear portion that mates with part of the gear drive train. Instead, the instrument includes a second motor  265  with a threaded rod  266  threaded therein. The threaded rod  266  reciprocates longitudinally in and out of the motor  265  as the motor  265  rotates, depending on the direction of rotation. The instrument  10  also includes an encoder  268  that is responsive to the rotations of the main drive shaft  48  for translating the incremental angular motion of the main drive shaft  48  (or other component of the main drive assembly) into a corresponding series of digital signals, for example. In the illustrated embodiment, the pinion gear  124  includes a proximate drive shaft  270  that connects to the encoder  268 . 
     The instrument  10  also includes a control circuit (not shown), which may be implemented using a microcontroller or some other type of integrated circuit, that receives the digital signals from the encoder  268 . Based on the signals from the encoder  268 , the control circuit may calculate the stage of deployment of the knife  32  in the end effector  12 . That is, the control circuit can calculate if the knife  32  is fully deployed, fully retracted, or at an intermittent stage. Based on the calculation of the stage of deployment of the end effector  12 , the control circuit may send a signal to the second motor  265  to control its rotation to thereby control the reciprocating movement of the threaded rod  266 . 
     In operation, as shown in  FIG. 37 , when the closure trigger  18  is not locked into the clamped position, the firing trigger  20  rotated away from the pistol grip portion  26  of the handle  6  such that the front face  242  of the upper portion  230  of the firing trigger  20  is not in contact with the proximate end of the threaded rod  266 . When the operator retracts the closure trigger  18  and locks it in the clamped position, the firing trigger  20  rotates slightly towards the closure trigger  20  so that the operator can grasp the firing trigger  20 , as shown in  FIG. 38 . In this position, the front face  242  of the upper portion  230  contacts the proximate end of the threaded rod  266 . 
     As the user then retracts the firing trigger  20 , after an initial rotational amount (e.g. 5 degrees of rotation) the run motor sensor  110  may be activated such that, as explained above, the sensor  110  sends a signal to the motor  65  to cause it to rotate at a forward speed proportional to the amount of retraction force applied by the operator to the firing trigger  20 . Forward rotation of the motor  65  causes the main drive shaft  48  to rotate via the gear drive train, which causes the knife  32  and sled  33  to travel down the channel  22  and sever tissue clamped in the end effector  12 . The control circuit receives the output signals from the encoder  268  regarding the incremental rotations of the main drive shaft assembly and sends a signal to the second motor  265  to cause the second motor  265  to rotate, which causes the threaded rod  266  to retract into the motor  265 . This allows the upper portion  230  of the firing trigger  20  to rotate counter clockwise, which allows the lower portion  228  of the firing trigger to also rotate counter clockwise. In that way, because the reciprocating movement of the threaded rod  266  is related to the rotations of the main drive shaft assembly, the operator of the instrument  10 , by way of his/her grip on the firing trigger  20 , experiences tactile feedback as to the position of the end effector  12 . The retraction force applied by the operator, however, does not directly affect the drive of the main drive shaft assembly because the firing trigger  20  is not geared into the gear drive train in this embodiment. 
     By virtue of tracking the incremental rotations of the main drive shaft assembly via the output signals from the encoder  268 , the control circuit can calculate when the knife  32  is fully deployed (i.e., fully extended). At this point, the control circuit may send a signal to the motor  65  to reverse direction to cause retraction of the knife  32 . The reverse direction of the motor  65  causes the rotation of the main drive shaft assembly to reverse direction, which is also detected by the encoder  268 . Based on the reverse rotation detected by the encoder  268 , the control circuit sends a signal to the second motor  265  to cause it to reverse rotational direction such that the threaded rod  266  starts to extend longitudinally from the motor  265 . This motion forces the upper portion  230  of the firing trigger  20  to rotate clockwise, which causes the lower portion  228  to rotate clockwise. In that way, the operator may experience a clockwise force from the firing trigger  20 , which provides feedback to the operator as to the retraction position of the knife  32  in the end effector  12 . The control circuit can determine when the knife  32  is fully retracted. At this point, the control circuit may send a signal to the motor  65  to stop rotation. 
     According to other embodiments, rather than having the control circuit determine the position of the knife  32 , reverse motor and stop motor sensors may be used, as described above. In addition, rather than using a proportional sensor  110  to control the rotation of the motor  65 , an on/off switch or sensor can be used. In such an embodiment, the operator would not be able to control the rate of rotation of the motor  65 . Rather, it would rotate at a preprogrammed rate. 
       FIGS. 41-43  illustrate an exemplary embodiment of a mechanically actuated endocutter, and in particular the handle  6 , shaft  8  and end effector  12  thereof. Further details of a mechanically actuated endocutter may be found in U.S. patent application Ser. No. 11/052,632 entitled, “Surgical Stapling Instrument Incorporating A Multi-Stroke Firing Mechanism With Automatic End Of Firing Travel Retraction,” which is incorporated herein by reference. With reference to  FIG. 41 , the end effector  12  responds to the closure motion from the handle  6  (not depicted in  FIG. 41 ) first by including an anvil face  1002  connecting to an anvil proximal end  1004  that includes laterally projecting anvil pivot pins  25  that are proximal to a vertically projecting anvil tab  27 . The anvil pivot pins  25  translate within kidney shaped openings  1006  in the staple channel  22  to open and close anvil  24  relative to channel  22 . The tab  27  engages a bent tab  1007  extending inwardly in tab opening  45  on a distal end  1008  of the closure tube  1005 , the latter distally terminating in a distal edge  1008  that pushes against the anvil face  1002 . Thus, when the closure tube  1005  moves proximally from its open position, the bent tab  1007  of the closure tube  1005  draws the anvil tab  27  proximally, and the anvil pivot pins  25  follow the kidney shaped openings  1006  of the staple channel  22  causing the anvil  24  to simultaneously translate proximally and rotate upward to the open position. When the closure tube  1005  moves distally, the bent tab  1007  in the tab opening  45  releases from the anvil tab  27  and the distal edge  1008  pushes on the anvil face  1002 , closing the anvil  24 . 
     With continued reference to  FIG. 41 , the shaft  8  and end effector  12  also include components that respond to a firing motion of a firing rod  1010 . In particular, the firing rod  1010  rotatably engages a firing trough member  1012  having a longitudinal recess  1014 . Firing trough member  1012  moves longitudinally within frame  1016  in direct response to longitudinal motion of firing rod  1010 . A longitudinal slot  1018  in the closure tube  1005  operably couples with the right and left exterior side handle pieces  61 ,  62  of the handle  6  (not shown in  FIG. 41 ). The length of the longitudinal slot  1018  in the closure tube  1005  is sufficiently long to allow relative longitudinal motion with the handle pieces  61 ,  62  to accomplish firing and closure motions respectively with the coupling of the handle pieces  61 ,  62  passing on through a longitudinal slot  1020  in the frame  1016  to slidingly engage the longitudinal recess  1014  in the frame trough member  1012 . 
     The distal end of the frame trough member  1012  is attached to a proximal end of a firing bar  1022  that moves within the frame  1016 , specifically within a guide  1024  therein, to distally project the knife  32  into the end effector  12 . The end effector  12  includes a staple cartridge  34  that is actuated by the knife  32 . The staple cartridge  34  has a tray  1028  that holds a staple cartridge body  1030 , a wedge sled driver  33 , staple drivers  1034  and staples  1036 . It will be appreciated that the wedge sled driver  33  longitudinally moves within a firing recess (not shown) located between the cartridge tray  1028  and the cartridge body  1030 . The wedge sled driver  33  presents camming surfaces that contact and lift the staple drivers  1034  upward, driving the staples  1036 . The staple cartridge body  1030  further includes a proximally open, vertical slot  1031  for passage of the knife  32 . Specifically, a cutting surface  1027  is provided along a distal end of knife  32  to cut tissue after it is stapled. 
     It should be appreciated that the shaft  8  is shown in  FIG. 4  as a non-articulating shaft. Nonetheless, applications of the present invention may include instruments capable of articulation, for example, as such shown above with reference to  FIGS. 1-4  and described in the following U.S. patents and patent applications, the disclosure of each being hereby incorporated by reference in their entirety: (1) “SURGICAL INSTRUMENT INCORPORATING AN ARTICULATION MECHANISM HAVING ROTATION ABOUT THE LONGITUDINAL AXIS”, U.S. Publication No. 2005/0006434, by Frederick E. Shelton IV, Brian J. Hemmelgarn, Jeffrey S. Swayze, Kenneth S. Wales, filed 9 Jul. 2003; (2) “SURGICAL STAPLING INSTRUMENT INCORPORATING AN ARTICULATION JOINT FOR A FIRING BAR TRACK”, U.S. Pat. No. 6,786,382, to Brian J. Hemmelgarn; (3) “A SURGICAL INSTRUMENT WITH A LATERAL-MOVING ARTICULATION CONTROL”, U.S. Pat. No. 6,981,628, to Jeffrey S. Swayze; (4) “SURGICAL STAPLING INSTRUMENT INCORPORATING A TAPERED FIRING BAR FOR INCREASED FLEXIBILITY AROUND THE ARTICULATION JOINT”, U.S. Pat. No. 6,964,363, to Frederick E. Shelton IV, Michael Setser, Bruce Weisenburgh II; and (5) “SURGICAL STAPLING INSTRUMENT HAVING ARTICULATION JOINT SUPPORT PLATES FOR SUPPORTING A FIRING BAR”, U.S. Publication No. 2005/0006431, by Jeffrey S. Swayze, Joseph Charles Hueil, filed 9 Jul. 2003. 
       FIGS. 42-43  show an embodiment of the handle  6  that is configured for use in a mechanically actuated endocutter along with the embodiment of the shaft  8  and end effector  12  as shown above in  FIG. 41 . It will be appreciated that any suitable handle design may be used to mechanically close and fire the end effector  12 . In  FIGS. 42-43 , the handle  6  of the surgical stapling and severing instrument  10  includes a linked transmission firing mechanism  1060  that provides features such as increased strength, reduced handle size, minimized binding, etc. 
     Closure of the end effector  12  (not shown in  FIGS. 42-43 ) is caused by depressing the closure trigger  18  toward the pistol grip  26  of handle  6 . The closure trigger  18  pivots about a closure pivot pin  252  that is coupled to right and left exterior lower side pieces  59 ,  60  the handle  6 , causing an upper portion  1094  of the closure trigger  18  to move forward. The closure tube  1005  receives this closure movement via the closure yoke  250  that is pinned to a closure link  1042  and to the upper portion  1094  of the closure trigger  18  respectively by a closure yoke pin  1044  and a closure link pin  1046 . 
     In the fully open position of  FIG. 42 , the upper portion  1094  of the closure trigger  18  contacts and holds a locking arm  1048  of the pivoting closure release button  30  in the position shown. When the closure trigger  18  reaches its fully depressed position, the closure trigger  18  releases the locking arm  1048  and an abutting surface  1050  rotates into engagement with a distal rightward notch  1052  of the pivoting locking arm  1048 , holding the closure trigger  18  in this clamped or closed position. A proximal end of the locking arm  1048  pivots about a lateral pivotal connection  1054  with the pieces  59 ,  60  to expose the closure release button  30 . An intermediate, distal side  1056  of the closure release button  30  is urged proximally by a compression spring  1058 , which is compressed between a housing structure  1040  and closure release button  30 . The result is that the closure release button  30  urges the locking arm  1048  counterclockwise (when viewed from the left) into locking contact with the abutting surface  1050  of closure trigger  18 , which prevents unclamping of closure trigger  18  when the linked transmission firing system  1040  is in an un-retracted condition. 
     With the closure trigger  18  retracted and fully depressed, the firing trigger  20  is unlocked and may be depressed toward the pistol grip  26 , multiple times in this embodiment, to effect firing of the end effector  12 . As depicted, the linked transmission firing mechanism  1060  is initially retracted, urged to remain in this position by a combination tension/compression spring  1062  that is constrained within the pistol grip  26  of the handle  6 , with its nonmoving end  1063  connected to the pieces  59 ,  60  and a moving end  1064  connected to a downwardly flexed and proximal, retracted end  1067  of a steel band  1066 . 
     A distally-disposed end  1068  of the steel band  1066  is attached to a link coupling  1070  for structural loading, which in turn is attached to a front link  1072   a  of a plurality of links  1072   a - 1072   d  that form a linked rack  1074 . Linked rack  1074  is flexible yet has distal links that form a straight rigid rack assembly that may transfer a significant firing force through the firing rod  1010  in the shaft  6 , yet readily retract into the pistol grip  26  to minimize the longitudinal length of the handle  6 . It should be appreciated that the combination tension/compression spring  1062  increases the amount of firing travel available while essentially reducing the minimum length by half over a single spring. 
     The firing trigger  20  pivots about a firing trigger pin  96  that is connected to the handle pieces  59 ,  60 . An upper portion  228  of the firing trigger  20  moves distally about the firing trigger pin  96  as the firing trigger  20  is depressed towards pistol grip  26 , stretching a proximally placed firing trigger tension spring  222  proximally connected between the upper portion  228  of the firing trigger  20  and the pieces  59 ,  60 . The upper portion  228  of the firing trigger  20  engages the linked rack  1074  during each firing trigger depression by a traction biasing mechanism  1078  that also disengages when the firing trigger  20  is released. Firing trigger tension spring  222  urges the firing trigger  20  distally when released and disengages the traction biasing mechanism  1078 . 
     As the linked transmission firing mechanism  1040  actuates, an idler gear  1080  is rotated clockwise (as viewed from the left side) by engagement with a toothed upper surface  1082  of the linked rack  1074 . This rotation is coupled to an indicator gear  1084 , which thus rotates counterclockwise in response to the idler gear  1080 . Both the idler gear  1080  and indicator gear  1084  are rotatably connected to the pieces  59 ,  60  of the handle  6 . The gear relationship between the linked rack  1074 , idler gear  1080  and indicator gear  1084  may be advantageously selected so that the toothed upper surface  1082  has tooth dimensions that are suitably strong and that the indicator gear  1084  makes no more than one revolution during the full firing travel of the linked transmission firing mechanism  1060 . 
     As described in greater detail below, the indicator gear  1084  performs at least four functions. First, when the linked rack  1074  is fully retracted and both triggers  18 , are open as shown in  FIG. 42 , an opening  1086  in a circular ridge  1088  on the left side of the indicator gear  1084  is presented to an upper surface  1090  of the locking arm  1048 . Locking arm  1048  is biased into the opening  1086  by contact with the closure trigger  18 , which in turn is urged to the open position by a closure tension spring  1092 . Closure trigger tension spring  1092  is connected proximally to the upper portion  1094  of the closure trigger  18  and the handle pieces  59 ,  60 , and thus has energy stored during closing of the closure trigger  18  that urges the closure trigger  18  distally to its unclosed position. 
     A second function of the indicator gear  1084  is that it is connected to the indicating retraction knob  1096  externally disposed on the handle  6 . Thus, the indicator gear  1084  communicates the relative position of the firing mechanism  1060  to the indicating retraction knob  1096  so that the surgeon has a visual indication of how many strokes of the firing trigger  20  are required to complete firing. 
     A third function of the indicator gear  1084  is to longitudinally and angularly move an anti-backup release lever  1098  of an anti-backup mechanism (one-way clutch mechanism)  1097  as the surgical stapling and severing instrument  10  is operated. During the firing strokes, proximal movement of anti-backup release lever  1098  by indicator gear  1084  activates the anti-backup mechanism  1097  that allows distal movement of firing bar  1010  and prevents proximal motion of firing bar  1010 . This movement also extends the anti-backup release button  1100  from the proximal end of the handle pieces  59 ,  60  for the operator to actuate should the need arise for the linked transmission firing mechanism  1060  to be retracted during the firing strokes. After completion of the firing strokes, the indicator gear  1084  reverses direction of rotation as the firing mechanism  1060  retracts. The reversed rotation deactivates the anti-backup mechanism  1097 , withdraws the anti-backup release button  1100  into the handle  6 , and rotates the anti-backup release lever  1098  laterally to the right to allow continued reverse rotation of the indicator gear  1084 . 
     A fourth function of the indicator gear  1084  is to receive a manual rotation from the indicating retraction knob  1096  (clockwise in the depiction of  FIG. 42 ) to retract the firing mechanism  1060  with anti-backup mechanism  1097  unlocked, thereby overcoming any binding in the firing mechanism  1060  that is not readily overcome by the combination tension/compression spring  1062 . This manual retraction assistance may be employed after a partial firing of the firing mechanism  1060  that would otherwise be prevented by the anti-backup mechanism  1097  that withdraws the anti-backup release button  1100  so that the latter may not laterally move the anti-backup release lever  1098 . 
     Continuing with  FIGS. 42-43 , anti-backup mechanism  1097  consists of the operator accessible anti-backup release lever  1098  operably coupled at the proximal end to the anti-backup release button  1100  and at the distal end to an anti-backup yoke  1102 . In particular, a distal end  1099  of the anti-backup release lever  1098  is engaged to the anti-backup yoke  1102  by an anti-backup yoke pin  1104 . The anti-backup yoke  1102  moves longitudinally to impart a rotation to an anti-backup cam slot tube  1106  that is longitudinally constrained by the handle pieces  59 ,  90  and that encompasses the firing rod  1010  distally to the connection of the firing rod  1010  to the link coupling  1070  of the linked rack  1074 . The anti-backup yoke  1102  communicates the longitudinal movement from the anti-backup release lever  1098  via a cam slot tube pin  1108  to the anti-backup cam slot tube  1106 . That is, longitudinal movement of cam slot tube pin  1108  in an angled slot in the anti-backup cam slot tube  1106  rotates the anti-backup cam slot tube  1106 . 
     Trapped between a proximal end of the frame  1016  and the anti-backup cam slot tube  1106  respectively are an anti-backup compression spring  1110 , an anti-backup plate  1112 , and an anti-backup cam tube  1114 . As depicted, proximal movement of the firing rod  1010  causes the anti-backup plate  1112  to pivot top to the rear, presenting an increased frictional contact to the firing rod  1010  that resists further proximal movement of the firing rod  1010 . 
     This anti-backup plate  1112  pivots in a manner similar to that of a screen door lock that holds open a screen door when the anti-backup cam slot tube  1106  is closely spaced to the anti-backup cam tube  1114 . Specifically, the anti-backup compression spring  1110  is able to act upon a top surface of the plate  1112  to tip the anti-backup plate  1112  to its locked position. Rotation of the anti-backup cam slot tube  1106  causes a distal camming movement of the anti-backup cam tube  1114  thereby forcing the top of the anti-backup plate  1112  distally, overcoming the force from the anti-backup compression spring  1110 , thus positioning the anti-backup plate  1112  in an untipped (perpendicular), unlocked position that allows proximal retraction of the firing rod  1010 . 
     With particular reference to  FIG. 43 , the traction biasing mechanism  1078  is depicted as being composed of a pawl  1116  that has a distally projecting narrow tip  1118  and a rightwardly projecting lateral pin  1120  at its proximal end that is rotatably inserted through a hole  1076  in the upper portion  230  of the firing trigger  20 . On the right side of the firing trigger  20  the lateral pin  1120  receives a biasing member, depicted as biasing wheel  1122 . As the firing trigger  20  translates fore and aft, the biasing wheel  1122  traverses an arc proximate to the right half piece  59  of the handle  6 , overrunning at its distal portion of travel a biasing ramp  1124  integrally formed in the right half piece  59 . The biasing wheel  1122  may advantageously be formed from a resilient, frictional material that induces a counterclockwise rotation (when viewed from the left) into the lateral pin  1120  of the pawl  1116 , thus traction biasing the distally projecting narrow tip  1118  downward into a ramped central track  1075  of the nearest link  1072   a - d  to engage the linked rack  1074 . 
     As the firing trigger  20  is released, the biasing wheel  1122  thus tractionally biases the pawl  1116  in the opposite direction, raising the narrow tip  1118  from the ramped central track  1075  of the linked rack  1074 . To ensure disengagement of the tip  1118  under high load conditions and at nearly full distal travel of the pawl  1116 , the right side of the pawl  1116  ramps up onto a proximally and upwardly facing beveled surface  1126  on the rightside of the closure yoke  250  to disengage the narrow tip  1118  from the ramped central track  1075 . If the firing trigger  20  is released at any point other than full travel, the biasing wheel  1122  is used to lift the narrow tip  1118  from the ramped central track  1075 . Whereas a biasing wheel  1122  is depicted, it should be appreciated that the shape of the biasing member or wheel  1122  is illustrative and may be varied to accommodate a variety of shapes that use friction or traction to engage or disengage the firing of the end effector  12 . 
     Various embodiments of the surgical instrument  10  have the capability to record instrument conditions at one or more times during use.  FIG. 44  shows a block diagram of a system  2000  for recording conditions of the instrument  10 . It will be appreciated that the system  2000  may be implemented in embodiments of the instrument  10  having motorized or motor-assisted firing, for example, as described above with reference to  FIGS. 1-40 , as well as embodiments of the instrument  10  having mechanically actuated firing, for example, as described above with reference to  FIGS. 41-43 . 
     The system  2000  may include various sensors  2002 ,  2004 ,  2006 ,  2008 ,  2010 ,  2012  for sensing instrument conditions. The sensors may be positioned, for example, on or within the instrument  10 . In various embodiments, the sensors may be dedicated sensors that provide output only for the system  2000 , or may be dual-use sensors that perform other functions with in the instrument  10 . For example, sensors  110 ,  130 ,  142  described above may be configured to also provide output to the system  2000 . 
     Directly or indirectly, each sensor provides a signal to the memory device  2001 , which records the signals as described in more detail below. The memory device  2001  may be any kind of device capable of storing or recording sensor signals. For example, the memory device  2001  may include a microprocessor, an Electrically Erasable Programmable Read Only Memory (EEPROM), or any other suitable storage device. The memory device  2001  may record the signals provided by the sensors in any suitable way. For example, in one embodiment, the memory device  2001  may record the signal from a particular sensor when that signal changes states. In another embodiment, the memory device  2001  may record a state of the system  2000 , e.g., the signals from all of the sensors included in the system  2000 , when the signal from any sensor changes states. This may provide a snap-shot of the state of the instrument  10 . In various embodiments, the memory device  2001  and/or sensors may be implemented to include 1-WIRE bus products available from DALLAS SEMICONDUCTOR such as, for example, a 1-WIRE EEPROM. 
     In various embodiments, the memory device  2001  is externally accessible, allowing an outside device, such as a computer, to access the instrument conditions recorded by the memory device  2001 . For example, the memory device  2001  may include a data port  2020 . The data port  2020  may provide the stored instrument conditions according to any wired or wireless communication protocol in, for example, serial or parallel format. The memory device  2001  may also include a removable medium  2021  in addition to or instead of the output port  2020 . The removable medium  2021  may be any kind of suitable data storage device that can be removed from the instrument  10 . For example, the removable medium  2021  may include any suitable kind of flash memory, such as a Personal Computer Memory Card International Association (PCMCIA) card, a COMPACTFLASH card, a MULTIMEDIA card, a FLASHMEDIA card, etc. The removable medium  2021  may also include any suitable kind of disk-based storage including, for example, a portable hard drive, a compact disk (CD), a digital video disk (DVD), etc. 
     The closure trigger sensor  2002  senses a condition of the closure trigger  18 .  FIGS. 45 and 46  show an exemplary embodiment of the closure trigger sensor  2002 . In  FIGS. 45 and 46 , the closure trigger sensor  2002  is positioned between the closure trigger  18  and closure pivot pin  252 . It will be appreciated that pulling the closure trigger  18  toward the pistol grip  26  causes the closure trigger  18  to exert a force on the closure pivot pin  252 . The sensor  2002  may be sensitive to this force, and generate a signal in response thereto, for example, as described above with respect to sensor  110  and  FIGS. 10A and 10B . In various embodiments, the closure trigger sensor  2002  may be a digital sensor that indicates only whether the closure trigger  18  is actuated or not actuated. In other various embodiments, the closure trigger sensor  2002  may be an analog sensor that indicates the force exerted on the closure trigger  18  and/or the position of the closure trigger  18 . If the closure trigger sensor  2002  is an analog sensor, an analog-to-digital converter may be logically positioned between the sensor  2002  and the memory device  2001 . Also, it will be appreciated that the closure trigger sensor  2002  may take any suitable form and be placed at any suitable location that allows sensing of the condition of the closure trigger. 
     The anvil closure sensor  2004  may sense whether the anvil  24  is closed.  FIG. 47  shows an exemplary anvil closure sensor  2004 . The sensor  2004  is positioned next to, or within the kidney shaped openings  1006  of the staple channel  22  as shown. As the anvil  24  is closed, anvil pivot pins  25  slides through the kidney shaped openings  1006  and into contact with the sensor  2004 , causing the sensor  2004  to generate a signal indicating that the anvil  24  is closed. The sensor  2004  may be any suitable kind of digital or analog sensor including a proximity sensor, etc. It will be appreciated that when the anvil closure sensor  2004  is an analog sensor, an analog-to-digital converter may be included logically between the sensor  2004  and the memory device  2001 . 
     Anvil closure load sensor  2006  is shown placed on an inside bottom surface of the staple channel  22 . In use, the sensor  2006  may be in contact with a bottom side of the staple cartridge  34  (not shown in  FIG. 46 ). As the anvil  24  is closed, it exerts a force on the staple cartridge  34  which is transferred to the sensor  2006 . In response, the sensor  2006  generates a signal. The signal may be an analog signal proportional to the force exerted on the sensor  2006  by the staple cartridge  34  and due to the closing of the anvil  24 . Referring the  FIG. 44 , the analog signal may be provided to an analog-to-digital converter  2014 , which converts the analog signal to a digital signal before providing it to the memory device  2001 . It will be appreciated that embodiments where the sensor  2006  is a digital or binary sensor may not include analog-to-digital converter  2014 . 
     The firing trigger sensor  110  senses the position and/or state of the firing trigger  20 . In motorized or motor-assisted embodiments of the instrument, the firing trigger sensor may double as the run motor sensor  110  described above. In addition, the firing trigger sensor  110  may take any of the forms described above, and may be analog or digital.  FIGS. 45 and 46  show an additional embodiment of the firing trigger sensor  110 . In  FIGS. 45 and 46 , the firing trigger sensor is mounted between firing trigger  20  and firing trigger pivot pin  96 . When firing trigger  20  is pulled, it will exert a force on firing trigger pivot pin  96  that is sensed by the sensor  110 . Referring to  FIG. 44 , In embodiments where the output of the firing trigger sensor  110  is analog, analog-to-digital converter  2016  is included logically between the firing trigger sensor  110  and the memory device  2001 . 
     The knife position sensor  2008  senses the position of the knife  32  or cutting surface  1027  within the staple channel  22 .  FIGS. 47 and 48  show embodiments of a knife position sensor  2008  that are suitable for use with the mechanically actuated shaft  8  and end effector  12  shown in  FIG. 41 . The sensor  2008  includes a magnet  2009  coupled to the firing bar  1022  of the instrument  10 . A coil  2011  is positioned around the firing bar  1022 , and may be installed; for example, along the longitudinal recess  1014  of the firing trough member  1012  (see  FIG. 41 ). As the knife  32  and cutting surface  1027  are reciprocated through the staple channel  22 , the firing bar  1022  and magnet  2009  may move back and forth through the coil  2011 . This motion relative to the coil induces a voltage in the coil proportional to the position of the firing rod within the coil and the cutting edge  1027  within the staple channel  22 . This voltage may be provided to the memory device  2001 , for example, via analog-to-digital converter  2018 . 
     In various embodiments, the knife position sensor  2008  may instead be implemented as a series of digital sensors (not shown) placed at various positions on or within the shaft  8 . The digital sensors may sense a feature of the firing bar  1022  such as, for example, magnet  2009 , as the feature reciprocates through the shaft  8 . The position of the firing bar  1022  within the shaft  8 , and by extension, the position of the knife  32  within the staple channel  22 , may be approximated as the position of the last digital sensor tripped. 
     It will be appreciated that the knife position may also be sensed in embodiments of the instrument  10  having a rotary driven end effector  12  and shaft  8 , for example, as described above, with reference to  FIGS. 3-6 . An encoder, such as encoder  268 , may be configured to generate a signal proportional to the rotation of the helical screw shaft  36 , or any other drive shaft or gear. Because the rotation of the shaft  36  and other drive shafts and gears is proportional to the movement of the knife  32  through the channel  22 , the signal generated by the encoder  268  is also proportional to the movement of the knife  32 . Thus, the output of the encoder  268  may be provided to the memory device  2001 . 
     The cartridge present sensor  2010  may sense the presence of the staple cartridge  34  within the staple channel  22 . In motorized or motor-assisted instruments, the cartridge present sensor  2010  may double as the cartridge lock-out sensor  136  described above with reference to  FIG. 11 .  FIGS. 50 and 51  show an embodiment of the cartridge present sensor  2010 . In the embodiment shown, the cartridge present sensor  2010  includes two contacts,  2011  and  2013 . When no cartridge  34  is present, the contacts  2011 ,  2013  form an open circuit. When a cartridge  34  is present, the cartridge tray  1028  of the staple cartridge  34  contacts the contacts  2011 ,  2013 , a closed circuit is formed. When the circuit is open, the sensor  2010  may output a logic zero. When the circuit is closed, the sensor  2010  may output a logic one. The output of the sensor  2010  is provided to memory device  2001 , as shown in  FIG. 44 . 
     The cartridge condition sensor  2012  may indicate whether a cartridge  34  installed within the staple channel  22  has been fired or spent. As the knife  32  is translated through the end effector  12 , it pushes the sled  33 , which fires the staple cartridge. Then the knife  32  is translated back to its original position, leaving the sled  33  at the distal end of the cartridge. Without the sled  33  to guide it, the knife  32  may fall into lock-out pocket  2022 . Sensor  2012  may sense whether the knife  32  is present in the lock-out pocket  2022 , which indirectly indicates whether the cartridge  34  has been spent. It will be appreciated that in various embodiments, sensor  2012  may directly sense the present of the sled at the proximate end of the cartridge  34 , thus eliminating the need for the knife  32  to fall into the lock-out pocket  2022 . 
       FIGS. 52A and 52B  depict a process flow  2200  for operating embodiments of the surgical instrument  10  configured as an endocutter and having the capability to record instrument conditions according to various embodiments. At box  2202 , the anvil  24  of the instrument  10  may be closed. This causes the closure trigger sensor  2002  and or the anvil closure sensor  2006  to change state. In response, the memory device  2001  may record the state of all of the sensors in the system  2000  at box  2203 . At box  2204 , the instrument  10  may be inserted into a patient. When the instrument is inserted, the anvil  24  may be opened and closed at box  2206 , for example, to manipulate tissue at the surgical site. Each opening and closing of the anvil  24  causes the closure trigger sensor  2002  and/or the anvil closure sensor  2004  to change state. In response, the memory device  2001  records the state of the system  2000  at box  2205 . 
     At box  2208 , tissue is clamped for cutting and stapling. If the anvil  24  is not closed at decision block  2210 , continued clamping is required. If the anvil  24  is closed, then the sensors  2002 ,  2004  and/or  2006  may change state, prompting the memory device  2001  to record the state of the system at box  2213 . This recording may include a closure pressure received from sensor  2006 . At box  2212 , cutting and stapling may occur. Firing trigger sensor  110  may change state as the firing trigger  20  is pulled toward the pistol grip  26 . Also, as the knife  32  moves through the staple channel  22 , knife position sensor  2008  will change state. In response, the memory device  2001  may record the state of the system  2000  at box  2013 . 
     When the cutting and stapling operations are complete, the knife  32  may return to a pre-firing position. Because the cartridge  34  has now been fired, the knife  32  may fall into lock-out pocket  2022 , changing the state of cartridge condition sensor  2012  and triggering the memory device  2001  to record the state of the system  2000  at box  2015 . The anvil  24  may then be opened to clear the tissue. This may cause one or more of the closure trigger sensor  2002 , anvil closure sensor  2004  and anvil closure load sensor  2006  to change state, resulting in a recordation of the state of the system  2000  at box  2017 . After the tissue is cleared, the anvil  24  may be again closed at box  2220 . This causes another state change for at least sensors  2002  and  2004 , which in turn causes the memory device  2001  to record the state of the system at box  2019 . Then the instrument  10  may be removed from the patient at box  2222 . 
     If the instrument  10  is to be used again during the same procedure, the anvil may be opened at box  2224 , triggering another recordation of the system state at box  2223 . The spent cartridge  34  may be removed from the end effector  12  at box  2226 . This causes cartridge present sensor  2010  to change state and cause a recordation of the system state at box  2225 . Another cartridge  34  may be inserted at box  2228 . This causes a state change in the cartridge present sensor  2010  and a recordation of the system state at box  2227 . If the other cartridge  34  is a new cartridge, indicated at decision block  2230 , its insertion may also cause a state change to cartridge condition sensor  2012 . In that case, the system state may be recorded at box  2231 . 
       FIG. 53  shows an exemplary memory map  2300  from the memory device  2001  according to various embodiments. The memory map  2300  includes a series of columns  2302 ,  2304 ,  2306 ,  2308 ,  2310 ,  2312 ,  2314 ,  2316  and rows (not labeled). Column  2302  shows an event number for each of the rows. The other columns represent the output of one sensor of the system  2000 . All of the sensor readings recorded at a given time may be recorded in the same row under the same event number. Hence, each row represents an instance where one or more of the signals from the sensors of the system  2000  are recorded. 
     Column  2304  lists the closure load recorded at each event. This may reflect the output of anvil closure load sensor  2006 . Column  2306  lists the firing stroke position. This may be derived from the knife position sensor  2008 . For example, the total travel of the knife  32  may be divided into partitions. The number listed in column  2306  may represent the partition where the knife  32  is currently present. The firing load is listed in column  2308 . This may be derived from the firing trigger sensor  110 . The knife position is listed at column  2310 . The knife position may be derived from the knife position sensor  2008  similar to the firing stroke. Whether the anvil  24  is open or closed may be listed at column  2312 . This value may be derived from the output of the anvil closure sensor  2004  and/or the anvil closure load sensor  2006 . Whether the sled  33  is present, or whether the cartridge  34  is spent, may be indicated at column  2314 . This value may be derived from the cartridge condition sensor  2012 . Finally, whether the cartridge  34  is present may be indicated a column  2316 . This value may be derived from cartridge present sensor  2010 . It will be appreciated that various other values may be stored at memory device  2001  including, for example, the end and beginning of firing strokes, for example, as measured by sensors  130 ,  142 . 
     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 example, although the embodiments described above have advantages for an endoscopically employed surgical severing and stapling instrument  100 , a similar embodiments may be used in other clinical procedures. It is generally accepted that endoscopic procedures are more common than laparoscopic procedures. Accordingly, the present invention has been 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 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. 
     Any patent, publication, or information, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this document. As such the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference.