Surgical instrument having a directional switching mechanism

[0001] The present application is related to the following commonly-owned U.S. Patent Applications filed concurrently herewith, and which are hereby incorporated by reference in their entirety:

[0002] (1) U.S. patent application Ser. No. 11/809,935, now U.S. Publication No. 2008/0296345A1, entitled SURGICAL INSTRUMENT HAVING A COMMON TRIGGER FOR ACTUATION AN END EFFECTOR CLOSING SYSTEM AND A STAPLE FIRING SYSTEM; and

[0003] (2) U.S. patent application Ser. No. 11/810,015, now U.S. Publication No. 2008/0300613A1, entitled SURGICAL INSTRUMENT HAVING A MULTIPLE RATE DIRECTIONAL SWITCHING MECHANISM.

[0004] 1. Field of the Invention

[0005] The present invention generally relates to surgical stapling instruments and, more particularly, to surgical staplers having an end effector closing system and a firing system for deploying staples.

[0006] 2. Description of the Related Art

[0007] As known in the art, surgical staplers are often used to deploy staples into soft tissue to reduce or eliminate bleeding from the soft tissue, especially as the tissue is being transected, for example. Surgical staplers, such as an endocutter, for example, often comprise an end effector which is configured to secure the soft tissue between first and second jaw members. The first jaw member often includes a staple cartridge which is configured to removably store staples therein and the second jaw member often includes an anvil. In use, the staples are typically deployed from the staple cartridge by a driver which traverses a channel in the staple cartridge and causes the staples to be deformed against the anvil and secure layers of the soft tissue together. Often, as known in the art, the staples are deployed in several staple lines, or rows, in order to more reliably secure the layers of tissue together. The end effector may also include a cutting member, such as a knife, for example, which is advanced between two rows of the staples to resect the soft tissue after the layers of the soft tissue have been stapled together.

[0008] After the driver and the cutting member have been advanced within the end effector, it is often necessary to retract the driver and/or cutting member to their starting positions. Previous surgical staplers have included a return spring which retracts the cutting member relative to the staple cartridge after a release button or toggle switch on the surgical stapler has been actuated by the surgeon. Such staplers, however, are unable to partially retract the cutting member and, as a result, the cutting member must be fully retracted before it can be readvanced. Other previous surgical staplers have included a plurality of triggers which are operatively engaged with systems for closing a jaw member and for advancing and/or retracting the driver and cutting member. Such devices, while suitable for their intended purposes, often require a surgeon to release a trigger operably engaged with the closing system and reposition their hand to grasp a different trigger which is operatively engaged with a system for advancing the staple driver and cutting member. While previous surgical staplers have been developed which have a single trigger for both closing the jaw member and advancing the driver and cutting member, such devices perform both functions upon the initial actuation of the trigger. While suitable in some circumstances, devices which perform both functions in the same trigger actuation are often exceedingly difficult to operate owing to the high degree of force required to actuate the trigger. Furthermore, such devices, as they close the jaw member and deploy staples in the same trigger actuation, do not afford the surgeon with an opportunity to evaluate the position of the closed jaw member and reposition the jaw member before the staples are deployed into the soft tissue. What is needed is an improvement over the foregoing.

[0009] In at least one form of the invention, a surgical instrument can include a switching mechanism which can allow a surgeon, or other clinician, to selectively advance or retract a staple driver and/or cutting member within a staple cartridge. In various embodiments, the surgical instrument can include a handle, a trigger operatively coupled to the handle, a firing drive, and an end effector. In at least one embodiment, the firing drive can include a first ratchet assembly configured to advance a cutting member in the end effector and a second ratchet assembly configured to retract the cutting member. In various embodiments, the trigger can include first and second pawls pivotably mounted thereon which are configured to be selectively engaged with the first and second ratchet assemblies, respectively. In at least one such embodiment, the trigger can be configured to slide between a first position in which the first pawl is engaged with the first ratchet assembly and a second position in which the second pawl is engaged with the second ratchet assembly. In such embodiments, a surgeon can quickly and conveniently select between advancing and retracting motions of the cutting member.

[0010] In at least one form of the invention, a surgical instrument can include a drive mechanism configured to advance a staple driver and/or cutting member at a first rate and retract the staple driver and/or cutting member at a different rate. In at least one embodiment, the rate at which the driver and cutting member are advanced and/or retracted is the distance that the driver and cutting member are translated per actuation, or stroke, of a trigger, for example. Accordingly, in such embodiments, a first rate is considered to be faster than a second rate if the trigger advances or retracts the cutting member a greater distance per actuation. In various embodiments, the cutting member can be retracted at a faster rate as compared to the rate in which it is advanced. In such embodiments, the surgical instrument can, owing to the slower advancing rate, provide a greater torque or advancing force to the cutting member while, owing to the faster retracting rate, reduce the time required for the surgeon to retract the cutting member. In various embodiments, as described above, the surgical instrument can include a switching mechanism configured to selectively engage one of a first drive system and a second drive system with a rotatable drive shaft. In at least one such embodiment, the first drive system can include a first gear having a first pitch radius and the second drive system can include a second gear having a different pitch radius where the first and second gears can rotate the drive shaft at different rates.

[0011] In at least one form of the invention, a surgical instrument can include a trigger which can be configured to close a jaw member onto soft tissue, for example, upon a first actuation of the trigger and advance a staple driver and/or cutting member upon a subsequent, or second, actuation of the trigger. In various embodiments, such a surgical instrument can allow a surgeon to position the surgical instrument in a surgical site and close the jaw member with an initial actuation of the trigger without deploying any staples into, or incising, the tissue. In such embodiments, as a result, the surgeon can manipulate the position of the surgical instrument and then actuate the trigger a second time to deploy staples into, and/or incise, the tissue. In at least one such embodiment, the first actuation of the trigger which closes the jaw member can also unlock a firing drive configured to advance the staple driver and cutting member during the second actuation of the trigger. In various embodiments, the surgical instrument can include a switching mechanism which can allow the surgeon to reopen the jaw member and, if they so choose, to reposition the jaw member in a more suitable position.

[0046] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate preferred embodiments of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

[0047] Certain exemplary embodiments will now be described to provide an overall understanding of the principles of the structure, function, manufacture, and use of the devices and methods disclosed herein. One or more examples of these embodiments are illustrated in the accompanying drawings. Those of ordinary skill in the art will understand that the devices and methods specifically described herein and illustrated in the accompanying drawings are non-limiting exemplary embodiments and that the scope of the various embodiments of the present invention is defined solely by the claims. The features illustrated or described in connection with one exemplary embodiment may be combined with the features of other embodiments. Such modifications and variations are intended to be included within the scope of the present invention.

[0048] In various embodiments, a surgical instrument in accordance with the present invention can include systems for inserting surgical staples into soft tissue, for example. In at least one embodiment, the surgical instrument can include a staple cartridge configured to removably store staples therein and an anvil for deforming the staples as they are deployed from the staple cartridge. In order to deploy the staples, the surgical instrument can include a staple driver configured to traverse the staple cartridge and a firing drive for advancing the staple driver within the staple cartridge. In various embodiments, the firing drive can include a drive bar which is translated in a substantially linear direction by a trigger operably engaged therewith. In other embodiments, the firing drive can include a drive shaft which is rotated by the trigger. In such embodiments, the surgical instrument can include a shaft assembly which can convert the rotary motion of the drive shaft into linear motion and translate the staple driver within the staple cartridge. While the exemplary embodiment illustrated in FIGS. 1-20 and described below includes a firing drive having a rotary drive shaft, the present invention is not so limited. Furthermore, while a general description of a firing drive having a rotary drive shaft is provided below, other such devices are described and illustrated in greater detail in the commonly-owned, co-pending U.S. patent application Ser. No. 11/475,412, entitled MANUALLY DRIVEN SURGICAL CUTTING AND FASTENING INSTRUMENT and filed on Jun. 27, 2006, the entire disclosure of which is hereby incorporated by reference herein.

[0049] Referring to FIG. 1, surgical instrument 50 can include handle portion 52, trigger 54, elongate shaft assembly 56, and end-effector 58. In various embodiments, end-effector 58 can include anvil 62 and staple cartridge channel 64, where channel 64 can be configured to receive staple cartridge 66 and anvil 62 can be pivotably connected to channel 64. In at least one embodiment, at least one of anvil 62 and channel 64 can be operably connected to trigger 54 such that, upon an actuation of trigger 54, anvil 62 can be rotated into a closed position as illustrated in FIG. 8. In various embodiments, referring to FIGS. 2-4, trigger 54 can be operably engaged with a closure drive system configured to translate both anvil 62 and channel 64 relative to outer sheath 57 of elongate shaft assembly 56. Referring primarily to FIG. 4, the closure drive can include cam 68 operably engaged with trigger 54 such that a first actuation of trigger 54 can rotate cam 68 about pin 70 and drive closure links 72 in a substantially linear direction. More particularly, trigger 54 can include lift pin 55 (FIG. 3) extending therefrom which can be configured to contact surface 71 of cam 68 and lift cam 68 into the position illustrated in FIG. 8. Cam 68 can further include cam slot 69 where, when cam 68 is rotated from its position illustrated in FIG. 4 to its position illustrated in FIG. 8, the side walls of cam slot 69 can engage closure link pin 76 and, in the present embodiment, slide closure links 72 in a direction illustrated by arrow A (FIG. 4).

[0050] Referring to FIGS. 2 and 4, surgical instrument 50 can further include a spine assembly within elongate shaft assembly 56 (FIG. 1), where the spine assembly can include proximal channel portion 78 and distal channel portion 80. In various embodiments, channel portions 78 and 80 can be interconnected by the cooperative engagement of projection, or tongue, 84 and groove 86. More particularly, referring to FIG. 2, proximal channel portion 78 can include, in various embodiments, first half 77 and second half 79 which can be assembled to distal channel portion 80 such that projection 84 is secured within groove 86. In at least one embodiment, proximal channel portion halves 77 and 79 can include projections 81 and/or apertures 83 configured to provide a snap-fit or press-fit engagement between proximal channel portion halves 77 and 79. In various other embodiments, channel portions 78 and 80 can be interconnected by any suitable means and, in at least one embodiment, although not illustrated, portions 78 and 80 can be integrally formed. Similar to the above, referring to FIG. 2, distal channel portion 80 can include distal end 88 which can be connected to staple cartridge channel 64. More particularly, distal channel portion 80 and staple cartridge channel 64 can include cooperating tongue and groove features, for example, which can provide a press-fit or snap-fit interconnection therebetween, although any other suitable interconnection therebetween can be used.

[0051] Referring to FIG. 4, proximal end 82 of channel portion 78 can be coupled to closure links 72 by pin 53 such that, when closures links 72 are translated by cam 68, channel portion 78 is translated within elongate shaft assembly 56. In at least one embodiment, channel portion 78 can further include projections 87 extending therefrom which can be configured to slide within recesses 85 (FIG. 3) in housing portions 90 and substantially limit the translation of channel portion 78 along an axis. As staple cartridge channel 64 is connected to proximal channel portion 78 via distal channel portion 80, channel 64, and anvil 62 pivotably connected thereto, can be moved in direction A when cam 68 is rotated by trigger 54 as described above. In at least one embodiment, referring to FIG. 2, proximal end 63 of anvil 62 can be configured to abut outer sheath 57 of elongate shaft assembly 56 when channel 64 and anvil 62 are translated relative to sheath 57. After proximal end 63 of anvil 62 contacts outer sheath 57, anvil 62 can be configured to rotate toward channel 64 and staple cartridge 66 in order to close anvil 62 as illustrated in FIG. 8. In various embodiments, referring to FIG. 2, channel 64 can include slots 65 therein which can be configured to guide anvil 62 as it is pivoted relative to channel 64. Once anvil 62 is closed, the surgical instrument can further include a lock which holds anvil 62 in its closed position. In various embodiments, referring to FIGS. 9-11, surgical instrument 50 can include spring lock 92 mounted to housing 90, where spring lock 92 can be configured to releasably hold cam 68 in position which, as a result, locks closure links 72, channel portions 78 and 80, channel 64, and anvil 62 in position until a surgeon desires to open anvil 62 as described in detail further below.

[0052] In various embodiments, after anvil 62 has been placed into its closed position, trigger 54 can be actuated a second time to operate a firing drive which advances cutting member 96 within end effector 58. In at least one embodiment, the firing drive can be disengaged from trigger 54 prior to the first actuation of trigger 54. In such embodiments, the first actuation of trigger 54 can operably engage trigger 54 with the firing drive and/or release a component of the firing drive such that the firing drive becomes operably engaged with trigger 54. In the illustrated embodiment, referring to FIGS. 3 and 4, the firing drive can include trigger gear portion 100 extending from trigger 54, gear train 102, gear carriage 130, and rotatable drive shaft 106 which can be configured to advance cutting member 96 within end effector 58 as described in greater detail below. As illustrated in FIGS. 3-7, gear train 102 can include ratchet gear 108, main drive gear 110, bevel drive gear 112, and bevel gear 114 where, prior to the first actuation of trigger 54, cam 68 can be configured to bias ratchet gear 108 out of engagement with main drive gear 110. More particularly, referring to FIG. 3, ratchet gear 108 can include shaft 116 and collar 118 where cam 68 can be configured to contact collar 118 and bias ratchet gear 108 away from main drive gear 112 such that ratchet face 109 on ratchet gear 108 is not engaged with ratchet face 111 on main drive gear 110.

[0053] Upon the first actuation of trigger 54, as described above, cam 68 can be rotated into the position illustrated in FIG. 8 and, as a result of such rotation, groove 120 (FIGS. 4 and 5) in cam 68 can be configured to release ratchet gear 108. More particularly, referring to FIGS. 5-7, groove 120 can be dimensioned such that, when the rotation of cam 68 aligns groove 120 with collar 118, collar 118 can slide past cam 68 and allow ratchet spring 122 to bias ratchet gear 108 into operative engagement with main drive gear 110. Thereafter, trigger 54 can be released and then returned to its starting position by trigger spring 124 where trigger spring 124 can be connected to pin 126 extending from housing 90 and pin 128 extending from trigger 54. Notably, eventhough trigger 54 can be returned to its starting position, cam 68 can remain locked in its second position by lock 92, as described above, thereby maintaining the alignment between groove 120 and collar 118. With ratchet gear 108 now operably engaged with drive gear 110, a second actuation of trigger 54 can advance cutting member 96 and the staple driver within end effector 58.

[0054] Referring primarily to FIGS. 3 and 4, an actuation of trigger 54 can rotate trigger gear portion 100 about an axis defined by pin 70. Trigger gear portion 100 can include gear teeth extending along the perimeter thereof which can, referring to FIGS. 5 and 6, be engaged with gear teeth extending around the circumference, for example, of ratchet gear 108. In use, as a result, the actuation, or rotation, of trigger 54 can rotate ratchet gear 108 about an axis defined by shaft 116 and pin 117 (FIG. 3). As described above, ratchet gear 108 can, referring to FIGS. 5 and 6, include ratchet face 109 which can be configured to engage ratchet face 111 of main drive gear 110. In at least one embodiment, ratchet faces 109 and 111 can be configured to transmit the rotational motion of trigger 54 to main drive gear 110 upon the second actuation, or other subsequent actuation, of trigger 54 but also permit relative sliding movement therebetween when trigger 54 is released and returned to its unactuated position. In effect, ratchet faces 109 and 111 can be configured to transmit rotational motion to main drive gear 110 when ratchet gear 108 is rotated in one direction but not transmit rotational motion to main drive gear 110 when ratchet gear 108 is rotated in the opposite direction. Although a ratchet mechanism has been described and illustrated herein, any other suitable mechanism for transmitting motion between trigger 54 and main drive gear 110 can be used. Furthermore, although trigger 54 has been described and illustrated as a lever, any other suitable device can be used to motivate the firing and closing drives described herein.

[0055] Referring primarily to FIGS. 5-7, main drive gear 110 can include gear teeth extending around the circumference thereof, for example, which can be engaged with gear teeth extending around the perimeter, for example, of bevel drive gear 112. In use, as a result, the rotational motion transmitted to main drive gear 110 from ratchet gear 108, for example, can be transmitted to bevel drive gear 112. In various embodiments, bevel drive gear 112 can be mounted to or integrally formed with shaft 113, where shaft 113 can define an axis about which bevel drive gear 112 can be rotated. In at least one embodiment, referring to FIG. 3, surgical instrument 50 can further include bracket 115 about which bevel drive gear 112 and shaft 113 can be rotated. As described in greater detail below, bracket 115 can also include supports 119 which can be configured to slidably support at least a portion of gear carriage 130. In various embodiments, referrring to FIGS. 5-7, bevel gear 114 can be attached to bevel drive gear 112 or, alternatively, bevel gear 114 can be mounted to or integrally formed with shaft 113. In either event, the rotational motion transmitted to bevel drive gear 112 can be transmitted to bevel gear 114.

[0056] In various embodiments, although not illustrated, bevel gear 114 could be directly engaged with drive shaft 106 via cooperating bevel gear teeth. In at least one such embodiment, bevel gear 114 could rotate drive shaft 106 in a clockwise direction, for example, and advance cutting member 96 within end effector 58 as described below. In such embodiments, the actuation of trigger 54 could advance cutting member 96 within end effector 58, however, cutting member 96 would have to be retracted either manually or via an additional retraction system. In the illustrated embodiment of the present invention, referring to FIGS. 3 and 5-7, surgical instrument 50 can further include a switching mechanism which can allow drive shaft 106 to be rotated in either a clockwise or counter-clockwise direction and, correspondingly, allow cutting member 96 to be advanced or retracted via the actuation of trigger 54. In various embodiments, referring primarily to FIGS. 5 and 6, the switching mechanism can include gear carriage 130 which can be shifted between a first position in which the rotational motion of bevel gear 114 rotates drive shaft 106 in a clockwise direction, for example, and a second position in which the rotational motion of bevel gear 114 rotates drive shaft 106 in a counter-clockwise direction.

[0057] In various embodiments, referring to FIGS. 5-7, gear carriage 130 can include housing 132, forward gear 134, and reversing gear 136 where forward gear 134 and reversing gear 136 can be rotatably mounted to housing 132. In at least one embodiment, drive shaft 106 can include substantially hex-shaped end 107, for example, which can be received within apertures (not illustrated) in forward gear 134 and reversing gear 136 such that gears 134 and 134 are rotatably engaged with drive shaft 106. In other various embodiments, end 107 can include any other suitable shape or configuration such that gears 134 and 136 are rotatably engaged with drive shaft 106. In either event, referring to FIG. 5, gear carriage 130 can be slid along end 107 such that either forward gear 134 or reversing gear 136 can be engaged with bevel gear 114. In use, when forward gear 134 is engaged with bevel gear 114, for example, the rotational motion of bevel gear 114 can be transmitted to forward gear 134 and, owing to cooperating geometries of end 107 and the aperture in forward gear 134, the rotational motion of gear 134 can be transmitted to drive shaft 106. In order to rotate drive shaft in the opposite direction, gear carriage 130 can be slid proximally, or rearward, such that reversing gear 136 engages bevel gear 114. A mechanism for motivating gear carriage 130 in this manner is described further below.

[0058] In various embodiments, when forward gear 134 is engaged with bevel gear 114, as illustrated in FIG. 5, reversing gear 136 can be disengaged from bevel gear 114 such that reversing gear 136 is free to rotate with drive shaft 106. In at least one embodiment, gear carriage 130 can further include spacer 135 which can be configured to rotatably support and align gears 134 and 136 yet permit gears 134 and 136 to rotate independent of one another. In some embodiments, gear carriage 130 can be placed in a position intermediate the forward and rearward positions such that both gears 134 and 136 engage bevel gear 114 and hold drive shaft 106 in a ‘locked-out’ condition such that trigger 54 cannot be actuated. In other various embodiments, gear carriage 130 can be placed in an intermediate position such that neither gears 134 and 136 engage bevel gear 114. In such embodiments, the firing drive is in a ‘free’ condition and the rotational motion of bevel gear 114 is not transmitted to drive shaft 106.

[0059] In various embodiments, referring primarily to FIG. 2, drive shaft 106 can further include threaded drive portion 138 which can be operably engaged with firing nut 140. In at least one embodiment, threaded drive portion 138 can be configured to slidably advance and/or retract firing nut 140 in response to rotational motion of drive shaft 106. More particularly, firing nut 140 can include threaded aperture 141 which can be configured to threadably receive threaded drive portion 138 such that the rotation of drive shaft 106 produces a reactional force which advances firing nut 140 distally. In at least one embodiment, firing nut 140 can include projection 142 extending therefrom which can be configured to extend through a slot defined between proximal channel portion halves 77 and 79 in order to constrain the movement of firing nut 140 along an axis. In effect, the slot can prevent firing nut 140 from rotating with drive shaft 106 and can define a path for projection 142 as firing nut 140 is translated within channel portion 78.

[0060] In various embodiments, referring to FIG. 2, cutting member 96 can be operably engaged with firing nut 140 such that the translation of firing nut 140, as described above, can result in the translation of cutting member 96 within end effector 58. In at least one embodiment, surgical instrument 50 can further include firing rod 144 connected to firing nut 140, drive bar 146 connected to cutting member 96, and adapter 148 configured to connect drive bar 146 to firing rod 144. In various embodiments, firing rod 144 can include proximal end 145 which can include an aperture configured to receive at least a portion of firing nut 140 in a press-fit manner. In at least one embodiment, proximal end 145 of firing rod 144 can include deformable member 147 which can be configured to engage recess 143 in firing nut 140 after deformable member 147 has been depressed or deformed inwardly toward recess 143. In either event, firing rod 144 can further include distal end 149 which can be configured to receive plug 150 in a press-fit manner, for example, where plug 150 can include projection 152 extending therefrom which can be received within slot 154 in adapter 148. In various embodiments, adapter 148 can further include slot 151, where slot 151 can be configured to receive connector tab 154 of drive bar 146 such that, when adapter 148 is translated by firing rod 144, drive bar 146 can be translated within distal retainer section 80. In at least one embodiment, drive bar 146 can further include distal end 156 which can be configured to engage recess 97 in cutting member 96 and advance and/or retract cutting member 96 within end effector 58. As described above, cutting member 96 can include knife 99 which can be configured to incise tissue positioned between anvil 62 and staple cartridge 66 as cutting member 96 is advanced within end effector 58. Further, as described above, cutting member 96 can include portion 95, where portion 95 can be configured to push a staple driver (not illustrated) within staple cartridge 66 to deploy staples (not illustrated) removably stored therein.

[0061] In various embodiments, the surgical instrument can be configured to advance cutting member 96 a desired distance upon a single actuation of trigger 54, i.e., the second overall actuation of trigger 54 in embodiments where the first actuation of trigger 54 closes anvil 62 as described above. In other embodiments, however, more than one actuation of trigger 54 can be used to advance cutting member 96 a desired distance. In at least one such embodiment, referring to FIGS. 12-16, trigger 54 can be actuated three times to advance cutting member 96 from proximal end 59 to distal end 61 of end effector 58. The quantity of such actuations in other embodiments, however, will depend largely upon the overall distance that cutting member 96 is to be displaced and the displacement of cutting member 96 as a result of each actuation. Notably, prior to the second actuation of trigger 54, cutting member 96 can be positioned in proximal end 59 of end effector 58 and firing nut 140 can be positioned in its most proximal position. Upon the second actuation of trigger 54, referring to FIGS. 13 and 14, cutting member 96 can be advanced approximately one-third of the distance between proximal end 59 and distal end 61 and, similarly, firing nut 140 can be advanced distally along drive shaft 106. Thereafter, referring to FIG. 15, cutting member can be advanced an additional one-third of the distance between proximal end 59 and distal end 61 upon the third actuation of trigger 54 and, similarly, referring to FIG. 16, cutting member 96 can be advanced into distal end 61 of end effector 58 upon the fourth actuation of trigger 54.

[0062] In various embodiments, in order to assist a surgeon in monitoring the amount of times that trigger 54 has been actuated, surgical instrument 50 can include a counting mechanism which can be configured to display the amount of times that trigger 54 has been actuated and/or the amount of actuations remaining to deploy all of the staples in the staple cartridge. In either event, referring primarily to FIGS. 3 and 9, one embodiment of counting mechanism 170 can include indicator nut 172, indicator plate 174, and indictor window 171 (FIG. 1) in housing 90. In at least one embodiment, indicator plate 174 can include indicia thereon which can communicate to the surgeon the amount of times that trigger 54 has been actuated to advance cutting member 96. In such embodiments, indicator plate 174 can include blank portion 173 which is visible through window 171 before and after the first actuation of trigger 54, i.e., the actuation of trigger 54 which closes anvil 62 as described above. Upon the second actuation of trigger 54, the rotation of drive shaft 106 can advance indicator nut 172 and indicator plate 174, which is mounted to indicator nut 172, distally such that the numeral “1” or other appropriate indicia on indicator plate 174 can be seen through indicator window 171. Accordingly, such an indicium can indicate to the surgeon that cutting member 96 has been advanced by one actuation of trigger 54. Similar to firing nut 140, indicator nut 172 can include a threaded aperture which can be threadably engaged with threaded portion 176 of drive shaft 106 such that the rotation of drive shaft 106 applies a reactional force to indicator nut 172 and advances it distally. Subsequent actuations of trigger 54 can move the numerals ‘2’ and ‘3’ beneath indicator window 171.

[0063] In order to retract cutting member 96, as outlined above, gear carriage 130 can be shifted such that forward gear 134 is disengaged from bevel gear 114 and, referring to FIGS. 17 and 18, reversing gear 136 is engaged with bevel gear 114. Thereafter, subsequent actuations of trigger 54 can rotate drive shaft 106 in the opposite direction and translate firing nut 140 proximally. More particularly, owing to the threaded engagement between firing nut 140 and threaded portion 138 of drive shaft 106, the rotation of shaft 106 in the opposite direction applies a reactional force to firing nut 140 which displaces firing nut 140 in the proximal direction. Accordingly, firing rod 144, drive bar 146 and cutting member 96, which can be connected to firing nut 140 as described above, are also displaced in the proximal direction thereby retracting cutting member 96 within end effector 58. Similarly, the rotation of shaft 106 in the opposite direction can displace indictor nut 172 of indicator assembly 170 proximally as well. More particularly, the first actuation of trigger 54 after gear carriage 130 has been shifted, i.e., the fifth overall actuation of trigger 54, can cause drive shaft 106 to apply a reactional force to indicator nut 172 and move nut 172 proximally. In such circumstances, indicator nut 172 can move indicator plate 174 relative to window 171 such that the numeral ‘2’ is visible through indicator window 171 which can remind the surgeon that two more actuations of trigger 54 are required to fully retract cutting member 96.

[0064] Although trigger 54 is actuated three times to advance and/or retract cutting member 96 in the present embodiment, the actuations required to advance cutting member 96 can be different than the actuations required to retract cutting member 96 in other embodiments. Exemplary embodiments including features for advancing and retracting cutting member 96 at different rates are described in detail further below. Furthermore, in at least one embodiment, portion 95 of cutting member 96 can be engaged with the staple driver such the retraction of cutting member 96 also retracts the staple driver. In other embodiments, however, the staple driver can be left behind in the staple cartridge and only the cutting member 96 is retracted. Such embodiments may be utilized where a spent staple cartridge assembly is replaced with a new staple cartridge assembly which includes its own staple driver therein and, as a result, it may be desirable to leave the used staple driver in the spent cartridge.

[0065] In order to motivate gear carriage 130 as described above, surgical instrument 50 can include, referring to FIGS. 3-5, switching mechanism 160. In at least one embodiment, switching mechanism 160 can include shaft switch 162, shifter handles 164 extending therefrom, and shifter link 166, where shifter link 166 can be connected to shaft 162 via shifter pin 169 and gear carriage housing 132 via pin 168. In order to slide gear carriage 130 relative to drive shaft 106 as described above, shifter handles 164 can be configured to rotate shaft 162 such that crank arm 163 extending from shaft 162 displaces shifter link 166 and drives gear carriage 130 along axis 105 of drive shaft 106. In the illustrated embodiment, when shifter handles 164 are oriented in a substantially downward direction, as illustrated in FIG. 8, crank arm 163 is oriented in a substantially upward direction. In this configuration, referring to FIG. 5, gear carriage 130 is positioned in its most rearward, or proximal, position such that forward gear 134 is operably engaged with bevel gear 114. In order to shift surgical instrument 50 into a configuration in which cutting member 96 is retracted, shifter handles 164 can be rotated upwardly, as illustrated in FIG. 17, to rotate crank arm 163 forward, or distally. Correspondingly, crank arm 163 can be configured to displace link arm 166 distally and pull gear carriage 130 into its most distal position, thereby engaging reversing gear 136 with bevel gear 114. In the event that the surgeon desires to advance cutting member 96 after at least partially retracting cutting member 96, the surgeon can rotate shifter handles 164 downwardly and re-engage forward gear 134 with bevel gear 114.

[0066] In various embodiments, referring to FIGS. 3 and 5, surgical instrument 50 can further include a bistable compliant mechanism for biasing switching mechanism 160 into a configuration where one of gears 134 or 136 is engaged with bevel gear 114. Stated another way, the bistable compliant mechanism can cause switching mechanism 160 to become dynamically unstable when a surgeon only partially rotates shifter handles 164. In such circumstances, the bistable compliant mechanism can bias switching mechanism 160 into one of two configurations where it is stable, i.e., the forward and reversing configurations. In various embodiments, bistable compliant mechanism 180, referring primarily to FIG. 3, can include receiver 182, spring 184, plunger 186 and toggle pin 188. In at least one embodiment, toggle pin 188 can connect plunger 186 to switch shaft 162 and receiver 182 can be connected to projection 183 extending from housing 90. In use, spring 184 can be configured to apply a biasing force to shaft 162 via plunger 186 and can be configured to rotate shaft 162 in the event that shaft 162 is only partially rotated between its forward and reversing orientations.

[0067] In various embodiments, once cutting member 96 has been fully retracted, the end effector closing system and the staple firing system can be reset so that the spent staple cartridge can be removed from surgical instrument 50, a new staple cartridge 66 can be positioned within staple cartridge channel 64, and surgical instrument 50 can be used to further staple and cut tissue as described above. In the illustrated embodiment, cam 68 can be released from lock 92 to open anvil 62 and reset the end effector closure system. Similarly, ratchet gear 108 can be disengaged from main drive gear 110 to disengage trigger 54 from gear train 102 and reset the staple firing system. In at least one embodiment, cam 68 and ratchet gear 108 can be manually reset, however, referring primarily to FIGS. 3-5, 9, 10, 19 and 20, surgical instrument 50 can include a reset system which can automatically reset the end effector closure system and staple firing system described above. In various embodiments, the final return actuation of trigger 54 can reset these systems as described in detail below.

[0068] As outlined above, the first actuation of trigger 54 can rotate cam 68 into the position illustrated in FIG. 8 and spring lock 92 can be configured to hold cam 68 in place as the firing drive is operated by subsequent actuations of trigger 54. As also illustrated in FIG. 8, surgical instrument 50 can further include cam spring 67 which can be configured to bias cam 68 downwardly and, referring to FIGS. 9 and 10, hold cam lock arm 73 extending from cam 68 against spring lock 92. In such embodiments, cam lock arm 73 can include recess 74 which can be configured to receive at least a portion of spring lock 92. In order to assist cam spring 67 in keeping cam 68 from lifting upwardly during subsequent actuations of trigger 54 and becoming disengaged from cam spring 92, indicator nut 174 can be configured to contact cam rail 75 and hold cam lock arm 73 against spring lock 92. More particularly, as indicator nut 174 is advanced distally, as described above, indicator nut 174 can be slid along contact rail 75 providing a positive stop against which cam 68 cannot rotate. Once indicator nut 174 is returned to its most proximal position, however, indicator nut 174 can become aligned with ramp 89 and, as a result, the third return actuation of trigger 54 can cause cam 68 to rotate upward slightly, thereby disengaging lock arm 73 from spring lock 92 as illustrated in FIG. 10.

[0069] After cam 68 has been released from lock 92, cam return spring 67 can be configured to rotate cam 68 downwardly and return it to its original position. As cam 68 is rotated downwardly, the walls of cam slot 69 can be configured to drive closure links 72 distally and, correspondingly, drive channel portions 78 and 80 and staple cartridge channel 64 distally as well. In at least one embodiment, end effector 58 can further include a spring (not illustrated) configured to bias anvil 62 upwardly as staple cartridge channel 64 is slid distally, i.e., away from outer sheath 57 of elongate shaft assembly 56. In other various embodiments, although not illustrated, surgical instrument 50 can further include an actuator in which a surgeon can operate to pull or push anvil 62 into an open position. In either event, in at least one embodiment, cam return spring 67 can assert a force sufficient for cam 68 to displace ratchet gear 108 out of engagement with main drive gear 110 and, as a result, reset the firing drive. In other various embodiments, cam return spring 67 may not be strong enough to pull cam 68 downwardly with sufficient force to disengage ratchet gear 108 from main drive gear 110. In at least one such embodiment, surgical instrument 50 can further include, referring to FIGS. 3-5 and 19, a toggle switch assembly which can selectively bias ratchet gear 108 away from main drive gear 110.

[0070] In various embodiments, referring primarily to FIGS. 3, 4, and 9, toggle switch assembly 190 can include toggle actuator 192 mounted to drive shaft 106, where toggle actuator 192 can include toggle arm 193 extending therefrom. Upon the final return actuation of trigger 54, in at least one embodiment, indicator nut 172 can contact toggle actuator 192 and rotate it about drive shaft 106 such that toggle arm 193 is rotated toward ratchet gear 108. In at least one such embodiment, referring to FIG. 9, indicator nut 172 can further include ramp 179 which can be configured to engage projection 191 extending from toggle actuator 192 and rotate toggle actuator 192 clockwise about drive shaft 106. In various embodiments, toggle arm 193 can be configured to contact ratchet gear 108 as it is rotated about drive shaft 106 and displace ratchet gear 108 away from main drive gear 110. In at least one embodiment, ratchet gear 108 can be sufficiently displaced away from drive gear 110 to allow cam return spring 67 to position cam 68 adjacent collar 118. Thereafter, cam 68 can hold ratchet gear 108 in this position until cam 68 is rotated upwardly as described above.

[0071] Although the above-described mechanisms can reset cam 68 and ratchet gear 108 into their initial positions, toggle arm 193 of toggle actuator 192, at least in the illustrated embodiment, can remain positioned against collar 118 of ratchet gear 108. Accordingly, even if cam 68 is rotated upwardly such that groove 120 is aligned with collar 118 upon the first actuation of trigger 54, ratchet gear 108 may not be released to engage main drive gear 110 as described above. In view of this, in at least one embodiment, surgical instrument 50 can include a reset mechanism for rotating toggle arm 193 out of engagement with ratchet gear 108. Such a mechanism can, in various embodiments, be manually operated and/or automatically operated in response to an actuation of trigger 54, for example. In at least one embodiment, as illustrated in FIG. 20, housing 90 can include projection 91 extending therefrom which can be configured to rotate toggle actuator 192 about drive shaft 106 and return it to its original, unactuated position as illustrated in FIG. 9. More particularly, in various embodiments, projection 91 can be configured to engage toggle link 194 (FIG. 3) as gear carriage 130 is moved from its distal position in which reversing gear 136 is engaged with bevel gear 114 to its proximal position in which forward gear 134 is engaged with bevel gear 114. Such movement can be effected by switching mechanism 160 when shifter handles 164 are rotated downwardly to move gear carriage 130 proximally and place surgical instrument 50 in its ‘advancing’ configuration described above. As a result of the contact between toggle link 194 and projection 91, toggle link 194 can be rotated about pin 195 such that toggle link 194 contacts actuator arm 193 and rotates toggle actuator 192 counterclockwise about drive shaft 106. In various embodiments, toggle switch assembly 190 can further include bistable compliant mechanism 196, which can assist in assuring that toggle switch assembly 190 does not become stuck in an intermediate configuration.

[0072] As described above, surgical instruments in accordance with the present invention can include a single trigger for actuating both an end effector closure system and a staple firing system. While the above-described features were described in connection with such single trigger surgical instruments, several of the features described above can be used in surgical instruments having a first trigger for actuating an end effector closure system and a second trigger for actuating a staple firing system. Referring to FIGS. 23-30, for example, surgical instrument 200 can include trigger 201 for actuating an end effector closure system and trigger 204 for actuating a staple firing system. In various embodiments, referring to FIG. 25, the end effector closure system can include closure link 203 operably engaged with closure trigger 201 via pin 209. The end effector closure system can further include slider 205 and closure tube 207 (FIG. 23), where closure tube 207 can be operably connected to closure link 203 via slider 205 and pin 211. More particularly, referring to FIG. 29, closure tube 207 can include flange 213 at its most proximal end which can be configured to be received within slot 215 in slider 205 such that the sliding motion of slider 205 is transmitted to closure tube 207.

[0073] In use, referring primarily to FIGS. 29 and 30, the actuation of trigger 201 can translate closure link 203 distally and, correspondingly, translate slider 205 and closure tube 207 distally as well. In various embodiments, closure tube 207 can include features which are cooperatively engaged with anvil 62 such that translation of closure tube 207 causes anvil 62 to rotate toward staple cartridge channel 64. More particularly, referring to FIG. 24, anvil 62 can include projection 51 extending therefrom which can be received within aperture 217 of closure tube 207 such that sidewalls of aperture 217 can abut projection 51 and rotate anvil 62 downwardly. To guide anvil 62, as outlined above, staple cartridge channel 64 can include slots 65 which can define a path for anvil 62 as it is rotated. Surgical instrument 200 can further include lock 219 which can be configured to hold trigger 201 in an actuated position thereby holding anvil 62 in a closed position. To open anvil 62, lock 219 (FIG. 28) can be disengaged from trigger 201 such that trigger 201 can be returned to its unactuated position. As trigger 201 is returned to its unactuated position, trigger 201 can drive slider 205 and closure tube 207 proximally and, owing to the operative engagement between projection 51 and aperture 217, rotate anvil 62 upwardly.

[0074] As indicated above, surgical instruments in accordance with the present invention can include a firing drive which can be configured to advance a cutting member, for example, at a first rate and retract the cutting member at a different rate. In various embodiments, referring to FIGS. 23-30, surgical instrument 200 can include firing drive 202 which can comprise trigger 204, drive shaft 206, first ratchet assembly 210, and second ratchet assembly 212. In at least one embodiment, ratchet assemblies 210 and 212 can be configured to rotate drive shaft 206 in clockwise and counter-clockwise directions, respectively, in order to advance or retract cutting member 96 within end effector 58. In various embodiments, referring to FIG. 25, trigger 204 can be selectively engageable with ratchet assemblies 210 and 212 such that, when trigger 204 is actuated, only one of ratchet assemblies 210 and 212 is driven by trigger 204. In at least one such embodiment, trigger 204 can be slidable along pin 214 in order to engage trigger 204 with one of ratchet assemblies 210 and 212. In the illustrated embodiment, pin 214 can be rotatably received in apertures 216 in housing portions 218 and provide an axis of rotation for trigger 204.

[0075] In various embodiments, referring to FIG. 27, trigger 204 can be positioned such that pawl 220, which can be pivotably mounted to trigger 204, is engaged with ratchet wheel 222 and, upon the actuation of trigger 204, ratchet wheel 222 is rotated about pin 214 by pawl 220. Upon the release of trigger 204, pawl 220 can slide over ratchet teeth 224 of ratchet wheel 222 permitting relative movement therebetween. In at least one embodiment, ratchet assembly 210 can further include a pawl spring (not illustrated) configured to bias pawl 220 into engagement with ratchet teeth 224 and re-engage pawl 220 with ratchet teeth 224 when trigger 204 is reactuated. In order to transmit the rotation of ratchet wheel 222 to drive shaft 206, drive shaft 206 can include forward gear 226 connected thereto. More particularly, in at least one embodiment, ratchet wheel 222 can further include gear teeth 228 which can be operably engaged with forward gear 226 such that the rotation of ratchet wheel 222 rotates forward gear 226 and drive shaft 206 about axis 230 (FIG. 25). In various embodiments, forward gear 226 can be press-fit, for example, onto drive shaft 206 or, in other various embodiments, forward gear 226 can be integrally formed with drive shaft 206.

[0076] In various embodiments, similar to the surgical instruments described above, drive shaft 206 can, referring to FIG. 24, be operably engaged with firing nut 140 in order to translate firing nut 140 within proximal retainer portion 232. As also described above, the translation of firing nut 140 can be transmitted to cutting member 96 via drive bar 146 in order to advance cutting member 96 within end effector 58. In order to retract cutting member 96 within end effector 58, in at least one embodiment, trigger 204 can be slid into engagement with second ratchet assembly 212 such that drive shaft 206 is rotated in the opposite direction when trigger 204 is actuated. Similar to ratchet assembly 210, referring to FIG. 28, ratchet assembly 212 can include ratchet wheel 234 and pawl 236 where pawl 236 can be pivotably mounted to trigger 204 and can be operatively engaged with ratchet wheel 234 via ratchet teeth 238. Similar to ratchet wheel 222, ratchet wheel 234 can include gear teeth 240 which can be operably engaged with reversing gear 242 mounted to drive shaft 206. As ratchet wheels 222 and 234 engage drive shaft 206 on substantially opposite sides, ratchet wheels 222 and 234 can rotate drive shaft 206 in opposite directions, i.e. clockwise and counter-clockwise directions, respectively. Thus, in order to select whether cutting member 96 is advanced or retracted within end effector 58, trigger 204 can be slid into operative engagement with either first ratchet assembly 210 or second ratchet assembly 212.

[0077] In various embodiments, although not illustrated, first ratchet wheel 222 and second ratchet wheel 234 can have substantially the same diameter, or pitch radius. Stated another way, the distance between the center, or axis of rotation, of the ratchet wheels and the gear teeth of the ratchet wheels can be the same. In such embodiments, the distance that cutting member 96 is advanced per actuation of trigger 204 will be substantially the same distance that cutting member 96 is retracted per actuation of trigger 204. While suitable in some circumstances, such embodiments may require a surgeon to actuate trigger 204 several times before cutting member 96 is completely retracted. In view of the above, in various embodiments, first ratchet wheel 222 can have a pitch radius which is different than the pitch radius of second ratchet wheel 234. In at least one embodiment, second ratchet wheel 234 can have a larger pitch radius than first ratchet wheel 222 such that cutting member 96 is retracted a distance per actuation of trigger 204 which is greater than the distance that cutting member 96 is advanced per actuation of trigger 204. Stated another way, second ratchet assembly 212 can, at least in these embodiments, retract cutting member 96 at a rate which is greater than which it is advanced. In such embodiments, first ratchet assembly 210 can, owing to the slower advancing rate, provide a greater torque or advancing force to cutting member 96 while second ratchet assembly 212 can, owing to the faster retracting rate, reduce the time required for the surgeon to retract the cutting member.

[0078] While the term ‘rate’, as used above, is used to describe the distance that cutting member 96 can be advanced or retracted per actuation of trigger 204, the term ‘rate’ is not so limited. In at least one embodiment, the term ‘rate’ can be used to describe the velocity and/or acceleration in which the cutting member is moved. In such embodiments, it may be desirable to have a cutting member which is advanced at a lower velocity and/or acceleration to better control the cutting member and retracted at a greater velocity and/or acceleration to reduce the time required to retract the cutting member. Furthermore, while the illustrated embodiments include ratchet assemblies for providing the different advancing and retracting rates, the invention is not so limited. On the contrary, other embodiments are envisioned which include spur gear trains, bevel gears, and/or other motion transmission devices.

[0079] In various embodiments, surgical instruments in accordance with the present invention may include a gearbox for increasing or decreasing the rotational speed of the drive shaft. In at least one embodiment, referring to FIG. 25, surgical instrument 200 can further include gearbox 250 which can be operably positioned intermediate drive shaft 206 and ratchet assemblies 210 and 212. In various embodiments, gearbox 250 can be used to ‘gear down’ the speed of drive shaft 206 such that shaft 206 turns at a slower speed than if gearbox 250 were not utilized. In alternative embodiments, a gearbox can be used to ‘gear up’ the speed of drive shaft 206 such that drive shaft 206 turns at a faster speed. In at least one embodiment, gearbox 250 can include at least one set of planetary gears for changing the speed of drive shaft 206. In other various embodiments, a gearbox, such as gearbox 252 illustrated in FIGS. 21 and 22, can include housing 253, input gear 254 mounted to input shaft 256, pinion gears 258, and output gear 260 mounted to output shaft 262. In such embodiments, owing to the different pitch radii of input gear 254 and output gear 260, input shaft 256 and output shaft 262 will rotate at different speeds. To facilitate the rotational movement of gears 254, 258, and 260 within housing 253, gearbox 252 can further include various support plates 264, spacers 266, and pins 268 as illustrated in FIG. 22. In addition to the above, gearbox 252 can also be used to convert the clockwise motion of input shaft 256, for example, into counter-clockwise motion of output shaft 262.

[0080] In various embodiments described above, trigger 204 of surgical instrument 200 can be slid between a first position in which it is operatively engaged with first ratchet assembly 210 and a second position in which it is operatively engaged with second ratchet assembly 212. In at least one embodiment, firing drive 202 can be configured such that first pawl 220, for example, is disengaged from first ratchet wheel 222 before second pawl 236 is engaged with second ratchet wheel 234. In such embodiments, trigger 204 may be positioned in an intermediate position where it is not operably engaged with either first ratchet assembly 210 or second ratchet assembly 212. In various embodiments, as a result, firing drive 202 can be in a ‘free’ state where the actuation of trigger 204 does not result in the rotation of drive shaft 206. In alternative embodiments, firing drive 202 can be configured such that second pawl 236, for example, is engaged with second ratchet wheel 234 before first pawl 220 is operatively disengaged from first ratchet wheel 222. In such embodiments, trigger 204 may be positioned in an intermediate ‘locked’ state where trigger 204 cannot be actuated, thereby indicating to the surgeon that trigger 204 is not completely engaged with either one of the ratchet assemblies and trigger 204 requires further adjustment.

[0081] In various embodiments, surgical instrument 200 can include a device which biases trigger 204 into engagement with one of first ratchet assembly 210 and second ratchet assembly 212. In at least one embodiment, referring to FIG. 33, surgical instrument 200 can further include bistable compliant mechanism 270 which can bias trigger 204 out of an intermediate position described above and into engagement with either first ratchet assembly 210 and second ratchet assembly 212. In various embodiments, bistable compliant mechanism 270 can include spring 272 and link 274, where spring 272 can apply a biasing force to trigger 204 via link 274 such that the biasing force acts to move trigger 204 out of its intermediate position illustrated in FIG. 33 and into engagement with either first ratchet wheel 222 or second ratchet wheel 234. More particularly, when trigger 204 is positioned in its intermediate position, spring 272 can be stretched to a length X1 and, owing to the resiliency of spring 272, spring 272 can seek to shorten itself to its unstretched length, or at least a length shorter than X1, such as length X2 for example. In order for spring 272 to shorten itself to length X2, spring 272 can rotate link 274 about pin 275 where pin 275 can extend from and pivotably mount link 274 to surgical instrument housing 218. More particularly, as the first end of spring 272 is mounted to pin 276 extending from housing 218 and the second end of spring 272 is mounted to pin 277 extending from link 274, spring 272 can shorten itself by moving pin 277 closer to pin 276 which is most easily accomplished by rotating link 274 about pin 275. As link 274 is rotated about pin 275, the side walls of slot 278 in link 274 can be configured to engage pin 279 extending from trigger 204 and slide trigger 204 into engagement with first ratchet wheel 222 or second ratchet wheel 234. In effect, the intermediate position of trigger 204 illustrated in FIG. 33 represents a dynamically unstable position and the positions of trigger 204 where trigger 204 is engaged with ratchet wheels 222 and 234 represent the dynamically stable positions of the firing drive system.

[0082] In various embodiments, as described above, surgical instruments in accordance with the present invention can include devices for rotating a drive shaft in a first direction in which the drive shaft advances a cutting member within an end effector, for example, and a second direction in which the drive shaft retracts the cutting member. In at least one embodiment, referring to FIGS. 31 and 32, a surgical instrument can include transmission 280, for example, which can allow a surgeon to select whether the drive shaft advances or retracts the cutting member. In various embodiments, transmission 280 can include housing 282, internal input shaft 284, external input shaft 285, output drive shaft 286, and switching mechanism 288, where switching mechanism 288 can be configured to selectively engage internal input shaft 284 and external input shaft 285 with output shaft 286. Although not illustrated, the surgical instrument can further include a trigger, for example, which is operatively engaged with external drive shaft 285 in order to rotate drive shaft 285 about axis 287 in a clockwise direction, for example. In at least one embodiment, transmission 280 can include pinion gears 292 rotatably mounted within housing 282, input gear 293 fixedly mounted to external input shaft 285, and output gear 294 mounted to output drive shaft 286, where input gear 293 can be operably engaged with outer gear teeth 290 of pinion gears 292 such that the rotation of external shaft 285 is transmitted to pinion gears 292.

[0083] In a first configuration of transmission 280, output gear 294 can be operatively engaged with inner gear teeth 291 of pinion gears 292 such that the rotation of pinion gears 292 is transmitted to output drive shaft 286. More particularly, output gear 294 can be operably engaged with output drive shaft 286 via splined end 296 such that output gear 294 drives output drive shaft 286 about axis 287. In this first configuration, a clockwise rotation of external input shaft 285, for example, can be converted into a counter-clockwise motion of output drive shaft 286. In a second configuration of transmission 280, output gear 294 can be disengaged from pinion gears 292 such that the rotation of external input shaft 285 is not transmitted to output drive shaft 286 via pinion gears 292. In order to disengage output gear 294 from pinion gears 292, internal drive shaft 284 can be slid relative to external drive shaft 285 such that input gear 297 contacts recess 298 in output gear 294 and pushes output gear 294 away from pinion gears 292. In at least one embodiment, recess 298 can include teeth 299 which can be operatively engaged with input gear 297 of internal input shaft 284 such that the rotation of internal input shaft 284 is transmitted to output drive shaft 286. In this second configuration of transmission 280, a clockwise rotation of internal input shaft 284 can be directly transmitted to output drive shaft 286 such that output shaft 286 rotates in a clockwise direction as well. In order to reengage output gear 294 with pinion gears 292, internal input gear 284 can be disengaged from output gear 294 to allow spring 281 to slide output gear 294 along splined end 296.

[0084] In the embodiments described above, a surgeon can selectively move internal input shaft 284 relative to external input shaft 285 to place transmission 280 in either a forward or reversing configuration. In order to move input shaft 284, in various embodiments, the surgical instrument can further include an actuator or trigger configured to translate internal input shaft 284. In at least one embodiment, the surgical instrument can include a first actuator or trigger for rotating external input shaft 285 and a second actuator or trigger for translating internal shaft 284 relative to external shaft 285. In such embodiments, internal input shaft 284 can include splines 283 which can be slidably engaged with external input shaft 285 such that the rotation of external shaft 285 is transmitted to internal shaft 284 yet sliding motion is permitted therebetween. In at least one embodiment, transmission 280 can further include bearing 300 which can rotatably support input gear 293 and, when compressed between input gear 293 and housing 282, provide a biasing force to keep input gear 293 operably engaged with pinion gears 292. In various embodiments, output shaft 286 can include member 302 extending therefrom which can be configured to be received within recess 301 of housing 282 in order to reduce, or even eliminate, relative movement between output shaft 286 and housing 282. In at least one embodiment, although not illustrated, transmission 280 may only have one pinion gear 292 and still operate in the manner described above.

[0085] In various embodiments, transmission 280 can also be configured to advance cutting member 96, for example, at a different rate than which it is retracted. In at least one embodiment, referring to FIGS. 31 and 32, the operative engagement between internal input shaft 284 and output shaft 286 can be used to advance cutting member 96 and, owing to the direct engagement between input gear 297 and output gear 294, internal input shaft 284 and output shaft 286 can rotate in a 1:1 ratio, i.e., for every rotation of internal input shaft 284, output shaft 286 is rotated once. In various embodiments, the operative engagement between external input shaft 285 and output shaft 286 can be used to retract cutting member 96 and, owing to the different pitch radii of input gear 293 and output gear 294 and their operative engagement with pinions 292, external input shaft 285 and output shaft 286 can rotate in a ratio different than 1:1. In the illustrated embodiment, output shaft 286 can rotate at a faster speed than external input shaft 285 when they are mated via pinions 292. In various embodiments, as a result, cutting member 96 can be translated at a faster rate when external input shaft 285 is operably engaged with output shaft 286 than when internal input shaft 284 is operably engaged with output shaft 286.

[0086] The devices disclosed herein can be designed to be disposed of after a single use, or they can be designed to be used multiple times. In either case, however, the device can be reconditioned for reuse after at least one use. Reconditioning can include any combination of the steps of disassembly of the device, followed by cleaning or replacement of particular pieces, and subsequent reassembly. In particular, the device can be disassembled, and any number of the particular pieces or parts of the device can be selectively replaced or removed in any combination. Upon cleaning and/or replacement of particular parts, the device can be reassembled for subsequent use either at a reconditioning facility, or by a surgical team immediately prior to a surgical procedure. Those skilled in the art will appreciate that reconditioning of a device can utilize a variety of techniques for disassembly, cleaning/replacement, and reassembly. Use of such techniques, and the resulting reconditioned device, are all within the scope of the present application.

[0087] Preferably, the invention described herein will be processed before surgery. First, a new or used instrument is obtained and if necessary cleaned. The instrument can then be sterilized. In one sterilization technique, the instrument is placed in a closed and sealed container, such as a plastic or TYVEK bag. The container and instrument are then placed in a field of radiation that can penetrate the container, such as gamma radiation, x-rays, or high-energy electrons. The radiation kills bacteria on the instrument and in the container. The sterilized instrument can then be stored in the sterile container. The sealed container keeps the instrument sterile until it is opened in the medical facility.

[0088] While this invention has been described as having exemplary designs, the present invention may be further modified within the spirit and scope of the disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains.