Patent Publication Number: US-2022211425-A1

Title: Multi-function surgical instrument

Description:
CROSS REFERENCES TO RELATED APPLICATION 
     This application is a continuation application of U.S. patent application Ser. No. 16/047,139, filed on Jul. 27, 2018, which is a continuation application of U.S. patent application Ser. No. 14/802,726, filed on Jul. 17, 2015 and now U.S. Pat. No. 10,039,593, which claims the benefit of and priority to U.S. Provisional Application No. 62/051,409, U.S. Provisional Application No. 62/051,416, U.S. Provisional Application No. 62/051,415, and U.S. Provisional Application No. 62/051,412 all of which were filed on Sep. 17, 2014. This application is related to U.S. patent application Ser. No. 14/802,582 (now U.S. Pat. No. 9,877,777), U.S. Patent Application No. 14/802,654 (now U.S. Pat. No. 9,987,077), and U.S. patent application Ser. No. 14/802,687 (now U.S. Pat. No. 9,974,603), all of which were filed on Jul. 17, 2015. The entire contents of each of the above applications are incorporated herein by reference. 
    
    
     BACKGROUND Technical Field 
     The present disclosure relates to surgical instruments and, more particularly, to a multi-function surgical instrument including a bipolar end effector assembly and a deployable monopolar assembly. 
     Background of Related Art 
     Bipolar surgical instruments typically include two generally opposing electrodes charged to different electric potentials to selectively apply energy to tissue. Bipolar electrosurgical forceps, for example, utilize both mechanical clamping action and electrical energy to effect hemostasis by heating tissue to coagulate and/or cauterize tissue. Certain surgical procedures require more than simply coagulating and/or cauterizing tissue and rely on the unique combination of clamping pressure, precise electrosurgical energy control, and gap distance (i.e., distance between opposing jaw members when closed about tissue) to “seal” tissue. Once tissue is sealed or otherwise treated, e.g., cauterized, coagulated, desiccated, etc., it is often desirable to cut the treated tissue. Accordingly, many forceps have been designed which incorporate a knife that effectively severs the tissue after tissue treatment. 
     Monopolar surgical instruments, on the other hand, include an active electrode, and are used in conjunction with a remote return electrode, e.g., a return pad, to apply energy to tissue. Monopolar instruments have the ability to rapidly move through tissue and dissect through narrow tissue planes. 
     In some surgical procedures, it may be beneficial to use both bipolar and monopolar instrumentation, e.g., procedures where it is necessary to dissect through one or more layers of tissue in order to reach underlying tissue(s) to be treated. Further, it may be beneficial, particularly with respect to endoscopic surgical procedures, to provide a single instrument incorporating both bipolar and monopolar features, thereby obviating the need to alternatingly remove and insert the bipolar and monopolar instruments in favor of one another. 
     As can be appreciated, as additional functional components are added to a surgical instrument, additional deployment structures or deployment structures capable of actuating more than one component are required. However, multiple deployment structures and/or combined deployment structures may be limited by spatial constraints within the housing of the surgical instrument, functional constraints of the components (e.g., where a combined deployment structure imparts additional force requirements for deploying one or more of the components coupled thereto), and/or may overly complicate the operable components of the surgical instrument. 
     SUMMARY 
     As used herein, the term “distal” refers to the portion that is being described that is further from a user, while the term “proximal” refers to the portion that is being described that is closer to a user. Further, to the extent consistent, any of the aspects described herein may be used in conjunction with any of the other aspects described herein. 
     Provided in accordance with aspects of the present disclosure is a surgical instrument including a housing having a shaft extending distally therefrom, an end effector assembly disposed at a distal end of the shaft, a handle assembly coupled to the housing, a deployable assembly, one or more actuators, and a closure member. The end effector assembly includes first and second jaw members, either or both of which are movable relative to the other between a spaced-apart position and an approximated position for grasping tissue therebetween. The handle assembly includes a movable handle operably coupled to the jaw members such that movement of the movable handle relative to the housing between an initial position and a compressed position moves the jaw members between the spaced-apart position and the approximated position. The deployable assembly is movable relative to the end effector assembly between a storage condition and a use condition. The actuator(s) is disposed on the housing and operably coupled to the deployable assembly such that rotation of the actuator(s) relative to the housing from an un-actuated position to an actuated position moves the deployable assembly between the storage condition and the use condition. The closure member is keyed to the actuator(s) and operably positioned relative to the movable handle such that, upon rotation of the actuator(s) relative to the housing from the un-actuated position to the actuated position, the closure member is urged into contact with the movable handle to urge the movable handle from the initial position to the compressed position, thereby moving the jaw members from the spaced-apart position to the approximated position. 
     In an aspect of the present disclosure, the deployable assembly includes an elongated insulative sheath slidably disposed about the shaft, and an energizable member slidably disposed within the shaft. 
     In another aspect of the present disclosure, in the storage condition, the elongated insulative sheath and the energizable member are positioned proximally of the end effector assembly and, in the use condition, the elongated insulative sheath extends about the end effector assembly and the energizable member extends distally from the end effector assembly. 
     In still another aspect of the present disclosure, the elongated insulative sheath defines a diameter greater than that of the first and second jaw members in the approximated position thereof but less than that of the first and second jaw members in the spaced-apart position thereof 
     In yet another aspect of the present disclosure, a drive assembly having a drive bar slidably disposed within the shaft and operably coupled to the jaw members is provided such that translation of the drive bar through the shaft moves the jaw members between the spaced-apart position and the approximated position. 
     In still yet another aspect of the present disclosure, the movable handle includes an intermediate portion about which the movable handle is pivotably coupled to the housing, a grasping portion that extends from the intermediate portion and the housing in a first direction, and a coupling portion that extends from the intermediate portion is a second direction. The coupling portion of the movable handle is operably coupled to the drive bar such that pivoting of the movable handle relative to the housing between the initial position and the compressed position translates the drive bar through the shaft. 
     In another aspect of the present disclosure, the movable handle further includes a finger extending from the coupling portion thereof. Upon rotation of the actuator(s) relative to the housing from the un-actuated position to the actuated position, the closure member is urged into contact with the finger to urge the movable handle to pivot from the initial position to the compressed position. 
     In another aspect of the present disclosure, a gear assembly is disposed within the housing and operably coupled between the actuator(s) and the deployable assembly. 
     In yet another aspect of the present disclosure, the actuator(s) and the closure member are keyed to a drive pin such that rotation of the actuator(s) relative to the housing rotates the drive pin and urges the closure member to move relative to the housing. 
     In still another aspect of the present disclosure, the actuator(s) is biased towards the un-actuated position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of the present disclosure are described herein with reference to the drawings wherein like reference numerals identify similar or identical elements: 
         FIG. 1  is a front, perspective view of an endoscopic surgical instrument provided in accordance with the present disclosure with the monopolar assembly thereof disposed in a storage condition; 
         FIG. 2  is an enlarged, perspective view of the area of detail indicated as “ 2 ” in  FIG. 1 ; 
         FIG. 3  is a front, perspective view from a first side of the proximal end of the surgical instrument of  FIG. 1  with portions removed to illustrate the internal working components thereof; 
         FIG. 4  is a rear, perspective view from a second side of the proximal end of the surgical instrument of  FIG. 1  with portions removed to illustrate the internal working components thereof; 
         FIG. 5  is an exploded, perspective view of the proximal end of the surgical instrument of  FIG. 1  with portions removed; 
         FIG. 6  is an exploded, perspective view of various operable assemblies of the surgical instrument of  FIG. 1 ; 
         FIG. 7  is a perspective view of the deployment and retraction mechanism and the monopolar assembly of the surgical instrument of  FIG. 1  with portions removed; 
         FIG. 8  is a cross-sectional view taken along section line “ 8 - 8 ” of  FIG. 3 ; 
         FIG. 9  is a rear, perspective view from a first side of the deployment and retraction mechanism of  FIG. 7 ; 
         FIG. 10  is a front, perspective view from a second side of the deployment and retraction mechanism of  FIG. 7 ; 
         FIG. 11  is an exploded, perspective view of the deployment and retraction mechanism of  FIG. 7 ; 
         FIG. 12  is a perspective view of the first housing component of the deployment and retraction mechanism of  FIG. 7  having a planet gear operably engaged with the ring gear thereof; 
         FIGS. 13-16  are side views of the first housing component and planet gear of  FIG. 12  illustrating movement of the planet gear from a proximal position corresponding to the storage condition of the monopolar assembly to a distal position corresponding to a use condition of the monopolar assembly; 
         FIG. 17  is an enlarged, side view of a portion of the second housing component of the deployment and retraction mechanism of  FIG. 7  having a carrier member operably engaged therewith; 
         FIG. 18  is a side, perspective view of a ratchet gear of the deployment and retraction mechanism of  FIG. 7 ; 
         FIG. 19  is a perspective view of the carrier member of  FIG. 17  operably positioned relative to the ratchet gear of  FIG. 18 ; 
         FIG. 20  is a perspective view of the carrier member of  FIG. 17 ; 
         FIG. 21  is a side, perspective view of the deployment and retraction mechanism of  FIG. 7  with portions removed to illustrate the operable engagement of internal components thereof; 
         FIG. 22  is side, perspective view of the proximal end of the deployment and retraction mechanism as illustrated in  FIG. 21 , further including a disengagement plate; 
         FIG. 23  is a side, perspective view of the proximal end of the deployment and retraction mechanism as illustrated in  FIG. 22 , further including the carrier member; 
         FIGS. 24 and 25  are side views of the ratchet gear and carrier member of the deployment and retraction mechanism of  FIG. 7  operably engaged with one another for rotation in forward and reverse directions, respectively; 
         FIG. 26  is a side, perspective view of the disengagement plate of the deployment and retraction mechanism of  FIG. 7 ; 
         FIG. 27  is a side view of the carrier member and disengagement plate of the deployment and retraction mechanism of  FIG. 7  operably positioned relative to one another to disengage the carrier member; 
         FIGS. 28 and 29  are side, perspective views of the deployment and retraction mechanism of  FIG. 7  with the slider disposed in respective proximal and distal positions; 
         FIG. 30  is an enlarged, side, perspective view of a portion of the deployment and retraction mechanism of  FIG. 7 ; 
         FIG. 31  is a side view of the proximal end of the surgical instrument of  FIG. 1  with portions removed to illustrate the internal working components thereof; 
         FIG. 32  is a front, perspective view of the surgical instrument of  FIG. 1  with the monopolar assembly thereof disposed in the use condition; 
         FIG. 33  is an enlarged, perspective view of the area of detail indicated as “ 33 ” in  FIG. 32 ; 
         FIG. 34  is a side view of the proximal end of the surgical instrument of  FIG. 1  with portions removed and the monopolar assembly disposed in the storage condition; and 
         FIG. 35  is a side view of the proximal end of the surgical instrument of  FIG. 1  with portions removed and the monopolar assembly disposed in the use condition. 
     
    
    
     DETAILED DESCRIPTION 
     Referring generally to  FIGS. 1-6 , an endoscopic surgical instrument provided in accordance with the present disclosure is shown generally identified by reference numeral  10 . Instrument  10 , as described below, is configured to operate in both a bipolar mode, e.g., for grasping, treating, and/or mechanically dissecting tissue, and a monopolar mode, e.g., for treating and/or electrically/electromechanically dissecting tissue. Although the present disclosure is shown and described with respect to instrument  10 , the aspects and features of the present disclosure are equally applicable for use with any suitable surgical instrument or portion(s) thereof for selectively actuating, moving, and/or deploying one or more assemblies and/or components of the surgical instrument, for example, to transition between a bipolar mode of operation and a monopolar mode of operation. Obviously, different connections and considerations apply to each particular instrument and the assemblies and/or components thereof; however, the aspects and features of the present disclosure remain generally consistent regardless of the particular instrument, assemblies, and/or components provided. 
     Continuing with reference to  FIGS. 1-6 , instrument  10  generally includes a housing  20 , a handle assembly  30 , a trigger assembly  60 , a rotating assembly  70 , a shaft  80 , an end effector assembly  100 , a drive assembly  140 , a knife assembly  160 , bipolar and monopolar activation assemblies  170 ,  180 , respectively, a monopolar assembly  200 , and a deployment and retraction mechanism  300 . As detailed below, shaft  80  extends distally from housing  20  and supports end effector assembly  100  at a distal end thereof, drive assembly  140  operably couples handle assembly  30  with end effector assembly  100  to enable selective manipulation of jaw members  110 ,  120  of end effector assembly  100 , knife assembly  160  is operably coupled with trigger assembly  60  to enable selective translation of a knife  164  of knife assembly  160  relative to end effector assembly  100 , and deployment and retraction mechanism  300  is operably coupled with monopolar assembly  200  to enable selective deployment and retraction of monopolar assembly  200 . Rotating assembly  70  enables selective rotation of end effector assembly  100  and monopolar assembly  200  relative to shaft  80 , while bipolar and monopolar activation assemblies  170 ,  180  enable the appropriate energy to be selectively delivered to end effector assembly  100  and monopolar assembly  200 , respectively. 
     Instrument  10  may also include an electrosurgical cable (not shown) that connects instrument  10  to a generator (not shown) or other suitable power source, although instrument  10  may alternatively be configured as a battery-powered instrument. The electrosurgical cable (not shown) includes wires (not shown) extending therethrough that have sufficient length to extend through housing  20  and/or shaft  80  in order to provide energy to at least one of the electrically-conductive surfaces  112 ,  122  of jaw members  110 ,  120 , respectively, of end effector assembly  100 , e.g., upon activation of bipolar activation switch  172  of bipolar activation assembly  170  in the bipolar mode of operation. Similarly, one or more of the wires of the electrosurgical cable (not shown) extends through housing  20  and/or shaft  80  in order to provide energy to monopolar assembly  200 , e.g., upon activation of either of the monopolar activation switches  182  of monopolar activation assembly  180  in the monopolar mode of operation. As can be appreciated, additional wires (not shown) are provided to electrically couple the various inter-operable electrical components of instrument  10 , as detailed below. 
     With reference to  FIG. 2 , end effector assembly  100  is attached at the distal end of shaft  80  ( FIG. 6 ) and includes opposing jaw members  110 ,  120  pivotably coupled to one another. Each of the jaw members  110 ,  120  includes a jaw body  111 ,  121  supporting the respective electrically-conductive surface  112 ,  122 , and a respective proximally-extending jaw flange  114 ,  124 . Jaw bodies  111 ,  121  define a curved configuration, although other configurations are also contemplated. Flanges  114 ,  124  are pivotably coupled to one another to permit movement of jaw members  110 ,  120  relative to one another between a spaced-apart position and an approximated position for grasping tissue between surfaces  112 ,  122 . One or both of surfaces  112 ,  122  are adapted to connect to the source of energy (not shown), e.g., via one or more wires (not shown), and are configured to conduct energy through tissue grasped therebetween to treat tissue, e.g., cauterize, coagulate/desiccate, and/or seal tissue. More specifically, in some embodiments, end effector assembly  100  defines a bipolar configuration wherein surface  112  is charged to a first electrical potential and surface  122  is charged to a second, different electrical potential such that an electrical potential gradient is created for conducting energy between surfaces  112 ,  122  and through tissue grasped therebetween for treating tissue. Referring additionally to  FIGS. 3-5 , bipolar activation switch  172  of bipolar activation assembly  170  is operably coupled between the source of energy (not shown) and surfaces  112 ,  122  via one or more wires (not shown), thus allowing the user to selectively apply energy to surfaces  112 ,  122  of jaw members  110 ,  120 , respectively, of end effector assembly  100  during a bipolar mode of operation. 
     End effector assembly  100  is designed as a unilateral assembly, i.e., where jaw member  120  is fixed relative to shaft  80  ( FIG. 6 ) and jaw member  110  is movable relative to shaft  80  ( FIG. 6 ) and fixed jaw member  120 . However, end effector assembly  100  may alternatively be configured as a bilateral assembly, i.e., where both jaw member  110  and jaw member  120  are movable relative to one another and to shaft  80  ( FIG. 6 ). Further, in some embodiments, a longitudinally-extending knife channel (not shown) may be defined within one or both of jaw members  110 ,  120  to permit reciprocation of knife  164  ( FIG. 6 ) therethrough, e.g., upon actuation of a trigger  62  of trigger assembly  60 , to cut tissue grasped between jaw members  110 ,  120 . Jaw members  110 ,  120  of end effector assembly  100  may otherwise be configured similar to those of the end effector assembly detailed in U.S. patent application Ser. No. 14/196,066, filed on Mar. 4, 2014, the entire contents of which are hereby incorporated herein by reference. 
     Referring to  FIGS. 3-6 , handle assembly  30  includes movable handle  40  and a fixed handle  50 . Fixed handle  50  is integrally associated with housing  20  and movable handle  40  is movable relative to fixed handle  50  between an initial position, wherein movable handle  40  is spaced-apart from fixed handle  50 , and a compressed position, wherein movable handle  40  is compressed towards fixed handle  50 . More specifically, an intermediate portion  41  of movable handle  40  is pivotably coupled within housing  20  on either side of housing  20  via a split pivot  42 . Intermediate portion  41  of movable handle  40  includes a tooth  43  extending proximally from intermediate portion  41 , the importance of which is detailed below. A grasping portion  44  of movable handle  40  extends from split pivot  42  in a first direction, ultimately exiting housing  20  to facilitate grasping and manipulation of movable handle  40  from the exterior of housing  20 . A bifurcated portion  45  of movable handle  40  extends from split pivot  42  in a second, opposite direction further into housing  20 . Bifurcated portion  45  of movable handle  40  includes a pair of spaced-apart flanges  46  each including an enlarged area  47 . One of flanges  46  also include a finger  48  extending from the free end thereof, the importance of which is detailed below. 
     Drive assembly  140  includes a drive bar  142  that is slidably disposed within shaft  80  and configured to operably couple movable handle  40  with end effector assembly  100 . More specifically, a proximal end  143   a  of drive bar  142  is operably coupled to movable handle  40  while a distal end  143   b  of drive bar is operably coupled to jaw members  110 ,  120 . A proximal collar  144  is engaged about drive bar  142  towards the proximal end  143   a  thereof and a clip  145  is engaged about drive bar  142  towards proximal end  143   a  thereof but distally-spaced from proximal collar  144 . A mandrel  146  having a proximal sleeve  147  and a distal washer  148  is slidably disposed about drive bar  142  between proximal collar  144  and clip  145 . A biasing member  149  is disposed about drive bar  142  between distal washer  148  of mandrel  146  and clip  145 . Spaced-apart flanges  46  of movable handle  40  are disposed on either side of proximal sleeve  147  of mandrel  146  with enlarged areas  47  of spaced-apart flanges  46  disposed longitudinally between proximal collar  144  and distal washer  148 . Drive bar  142  further includes an elongated cut-out  150  ( FIG. 8 ) and a pair of opposed longitudinal slots  152  defined therethrough, the importance of which are detailed below. 
     As noted above, bipolar activation switch  172  of bipolar activation assembly  170  is provided to selectively supply energy to surfaces  112 ,  122  ( FIG. 2 ) of jaw members  110 ,  120 , respectively, of end effector assembly  100 . Bipolar activation switch  172  is disposed within fixed handle  50  adjacent a depressible button  174  that is operably coupled to and extends from fixed handle  50 . Upon sufficient compression of movable handle  40  relative to fixed handle  50 , a button activation post  49  extending from movable handle  40  is urged into contact with depressible button  174  so as to depress depressible button  174  into fixed handle  50  to activate bipolar activation switch  172 . Bipolar activation switch  172  is disposed in electrical communication with the source of energy (not shown) and surfaces  112 ,  122  ( FIG. 2 ) of jaw members  110 ,  120  via one or more wires (not shown). 
     In use, upon compression of movable handle  40  towards fixed handle  50 , grasping portion  44  of movable handle  40  is pivoted about split pivot  42  in a generally proximal direction while bifurcated portion  45  of movable handle  40  is pivoted about split pivot  42  in a generally distal direction. Such distal movement of bifurcated portion  45  of movable handle  40  urges enlarged areas  47  of spaced-apart flanges  46  distally into contact with distal washer  148  to thereby urge mandrel  146  to slide distally about drive bar  142 . Distal sliding of mandrel  146  about drive bar  142  compresses biasing member  149  between distal washer  148  of mandrel  146  and clip  145  until sufficient potential energy is built up to urge clip  145  distally, thereby translating drive bar  142  distally through shaft  80  and relative to end effector assembly  100  to pivot jaw member  110  relative to jaw member  120  from the spaced-apart position to the approximated position to grasp tissue therebetween. 
     As movable handle  40  is compressed towards fixed handle  50 , tooth  43  of intermediate portion  41  of movable handle  40  engages a clicker tab  52  supported within fixed handle  50  to generate a tactile and/or an audible response. Clicker tab  52  may be constructed of a plastic film, sheet metal, or any suitable material configured to generate a “clicking” sound as clicker tab  52  is engaged and disengaged by tooth  43 . The response generated by clicker tab  52  indicates to the user that jaw members  110 ,  120  are sufficiently approximated so as to grasp tissue therebetween and that further compression of movable handle  40  toward fixed handle  50  will cause button activation post  49  to contact and depress depressible button  174  to activate bipolar activation switch  172 . Thus, upon further compression of movable handle  40 , bipolar activation switch  172  is activated to initiate the delivery of energy to surfaces  112 ,  122  ( FIG. 2 ) of jaw members  110 ,  120  to treat tissue grasped therebetween. 
     Once tissue has been treated, movable handle  40  is released or returned to its initial position. Upon return of movable handle  40  to the initial position, spaced-apart flanges  46  of bifurcated portion  45  of movable handle  40  are returned proximally to thereby return mandrel  146  and drive bar  142  proximally such that jaw member  110  is pivoted relative to jaw member  120  back to the spaced-apart position. Movable handle  40  may further include a biasing member (not shown) for biasing movable handle  40  towards the initial position such that, upon release of movable handle  40 , movable handle  40  is returned to its initial position and, accordingly, jaw member  110  is returned to the spaced-apart position relative to jaw member  120 . 
     Referring still to  FIGS. 3-6 , trigger  62  of trigger assembly  60  is selectively actuatable relative to housing  20  from an un-actuated position to an actuated position. More specifically, trigger  62  includes an intermediate portion  63  having a split pivot  64  about which trigger  62  is pivotably coupled to housing  20  on either side of housing  20 . A toggle portion  65  of trigger  62  extends from split pivot  64  in a first direction, ultimately exiting housing  20  to facilitate manipulation of trigger  62  from the exterior of housing  20 . A bifurcated portion  66  of trigger  62  extends from split pivot  64  in a second, opposite direction further into housing  20 . Bifurcated portion  66  of trigger  62  includes a pair of spaced-apart arms  67  interconnected via a transverse pin  68 . 
     Knife assembly  160  is operably coupled to trigger  62  such that actuation of trigger  62  from the un-actuated position to the actuated position translates knife  164  of knife assembly  160  from a retracted position, wherein knife  164  is disposed within shaft  80  proximally of jaw members  110 ,  120 , to an extended position, wherein knife  164  extends at least partially between jaw members  110 ,  120  and through the knife channel(s) (not shown) thereof to cut tissue grasped between jaw members  110 ,  120 . Knife assembly  160  includes a knife bar  162  that is slidably disposed within drive bar  142 , knife  164 , and a knife collar  166 . Knife  164  is engaged to and extends distally from knife bar  162 . Knife  164  defines a sharpened distal cutting edge  165  to facilitate cutting tissue, although other configurations are also contemplated. Knife collar  166  is slidably disposed about drive bar  142  of drive assembly  140 . A proximal foot  163  of knife bar  162  extends through elongated cut-out  150  ( FIG. 8 ) defined through drive bar  142  and is received within a corresponding slot  167  defined within knife collar  166  to engage knife collar  166  about the proximal end of knife bar  162 . Knife collar  166  further defines a transverse aperture  168  configured to receive transverse pin  68  of trigger assembly  60  to operably couple trigger assembly  60  and knife assembly  160  with one another. 
     In use, upon actuation of trigger  62  from the un-actuated position to the actuated position, toggle portion  65  of trigger is pivoted about split pivot  64  in a generally proximal direction while bifurcated portion  66  is pivoted about split pivot  64  in a generally distal direction. Such distal movement of bifurcated portion  66  of trigger  62  urges transverse pin  68  distally, thereby urging knife collar  166  distally. Distal urging of knife collar  166  urges proximal foot  163  of knife bar  162  to translate through elongated cut-out  150  ( FIG. 8 ) of drive bar  142 , thereby translating knife bar  162  and knife  164  distally through shaft  80  and relative to end effector assembly  100  from the retracted position to the extended position to cut tissue grasped between jaw members  110 ,  120 . 
     A biasing member  169  is disposed about drive bar  142  between knife collar  166  and rotation wheel  72  of rotating assembly  70  such that, upon release of trigger  62 , trigger  62  is returned under bias to the un-actuated position wherein bifurcated portion  66  is pivoted about split pivot  64  in a generally proximal direction to pull knife collar  166 , knife bar  162 , and knife  164  proximally, thereby returning knife  164  to the retracted position. 
     Shaft  80  defines a proximal portion  82  that extends into housing  20  and is engaged with rotation wheel  72  of rotating assembly  72  to longitudinally fix shaft  80  relative to housing  20 . A pair of opposed longitudinal slots  84  are defined through proximal portion  82  of shaft  80 , the importance of which are detailed below. As mentioned above, the distal end of shaft  80  engages jaw members  110 ,  120  of end effector assembly  100 . Further, an insulative plate  86  may be engaged to the distal end of shaft  80 . Insulative plate  86  extends along jaw flange  124  of jaw member  120 , facilitates the support of jaw members  110 ,  120  at the distal end of shaft  80 , and facilitates the electrical insulation of energizable member  220  of monopolar assembly  200  from end effector assembly  100  in the storage condition of monopolar assembly  200 . 
     With reference to  FIGS. 1, 2, and 6-8 , monopolar assembly  200  includes a sheath assembly  210  and an energizable member  220 . Sheath assembly  210  includes a proximal ferrule  212  and an elongated insulative sheath  214 . Proximal ferrule  212  includes a body  215  having an annular flange  216  extending radially outwardly from body  215  at the proximal end of body  215 . Annular flange  216  is retained within an annular slot  22  defined within housing  20  to fix proximal ferrule  212  in position relative to housing  20 . Elongated insulative sheath  214  is slidably disposed about shaft  80  and extends into proximal ferrule  212 . Elongated insulative sheath  214  defines a body portion  217  and an enlarged-diametered distal portion  218  extending distally from body portion  217 . An annular step  219  is defined at the interface between body portion  217  and enlarged-diametered distal portion  218  of elongated insulative sheath  214 . A proximal hub  230  is secured to the proximal end of elongated insulative sheath  214 . As detailed below, proximal hub  230  is slidable within ferrule  212  to thereby slide elongated insulative sheath  214  relative to proximal ferrule  212 . More specifically, elongated insulative sheath  214  is selectively movable about and relative to proximal ferrule  212 , shaft  80  and end effector assembly  100  between a storage position ( FIG. 2 ), wherein elongated insulative sheath  214  is disposed proximally of end effector assembly  100 , and a use position ( FIG. 33 ), wherein elongated insulative sheath  214  is substantially disposed about end effector assembly  100 . 
     Energizable member  220  of monopolar assembly  200  includes a proximal cap  222 , a proximal shaft  224 , an energizable element  226 , and an insulative sleeve  228 . Proximal cap  222  is engaged to proximal shaft  224  at the proximal end thereof and is operably engaged with deployment and retraction mechanism  300  for selectively deploying and retracting monopolar assembly  200 . Proximal shaft  224  extends from proximal cap  222  distally through housing  20 . Energizable element  226  extends through proximal shaft  224  and distally therefrom to a distal tissue-treating portion  227 . Energizable element  226  is coupled to the source of energy (not shown) and monopolar activation assembly  180  ( FIG. 5 ) via one or more wires (not shown). As detailed below, distal tissue-treating portion  227  of energizable element  226  of energizable member  220  functions as the active electrode of monopolar assembly  200 . Distal tissue-treating portion  227  of energizable member  220  may be hook-shaped (as shown), or may define any other suitable configuration, e.g., linear, ball, circular, angled, etc. Insulative sleeve  228  is disposed about at least a portion of energizable element  226 , proximally of distal tissue-treating portion  227  so as to facilitate the electrical insulation of energizable element  226  from its surroundings. 
     Energizable member  220  is disposed on the inner-edge side of the curved jaw bodies  111 ,  121  of jaw members  110 ,  120  of end effector assembly  100  and is movable relative thereto between a storage position ( FIG. 2 ), wherein distal tissue-treating portion  227  of energizable member  220  is positioned adjacent insulative plate  86  and proximal flanges  114 ,  124  of jaw members  110 ,  120  of end effector assembly  100 , and a use position ( FIG. 33 ), wherein distal tissue-treating portion  227  of energizable member  220  extends distally from end effector assembly  100  to facilitate treating tissue therewith. In the storage position ( FIG. 2 ), insulative plate  86 , jaw bodies  111 ,  121  of jaw members  110 ,  120 , and insulative sleeve  228  serve to electrically-insulate distal tissue-treating portion  227  of energizable member  220  from electrically-conductive surfaces  112 ,  122  of jaw members  110 ,  120 , respectively. In the use position ( FIG. 33 ), elongated insulative sheath  214  of sheath assembly  210  serves to electrically insulate end effector assembly  100  from distal tissue-treating portion  227  of energizable member  220 , while distal tissue-treating portion  227  extends distally from end effector assembly  100 . Further, in the use position ( FIG. 33 ), energy may be supplied to distal tissue-treating portion  227  of energizable member  220 , e.g., via activation of either of the activation switches  182  of monopolar activation assembly  180  ( FIG. 5 ), for treating tissue in the monopolar mode of operation. 
     An engagement pin  232  extends transversely from either side of proximal shaft  224  of energizable member  220 . Engagement pin  232  extends through opposed longitudinal slots  152  of drive bar  142  and opposed longitudinal slots  84  of shaft  80  and is engaged within proximal hub  230  of sheath assembly  210  at each end of engagement pin  232 , thereby securing sheath assembly  210  and energizable member  220  to one another. Thus, with proximal hub  230  and engagement pin  232  securing sheath assembly  210  and energizable member  220  with one another, and with proximal cap  222  of energizable member  220  operably coupled to deployment and retraction mechanism  300 , deployment and retraction mechanism  300  is operable to cooperatively translate sheath assembly  210  and energizable member  220  between their respective storage positions, collectively the storage condition of monopolar assembly  200  ( FIG. 2 ), and their respective use conditions, collectively the use condition of monopolar assembly  200  ( FIG. 33 ). Various safety features may be employed for this purpose and are described hereinbelow. 
     With reference to  FIG. 5 , monopolar activation assembly  180 , as noted above, includes a pair of monopolar activation switches  182 . Monopolar activation switches  182  are positioned adjacent windows  24  defined within housing  20  on either side thereof. A depressible button  184  is operably coupled within each window  24  and extends outwardly therefrom. Depressible buttons  184  are selectively depressible from the exterior of housing  20  and, upon sufficient depression, are urged into contact with the respective monopolar activation switch  182  to activate that monopolar activation switch  182 . Monopolar activation switches  182  are coupled to one another via a flex circuit  185  that extends along the inner perimeter of housing  20  about deployment and retraction mechanism  300 . Monopolar activation assembly  180  further includes a connector member  186  and is coupled to a safety assembly  188  having proximal and distal safety switches  189   a,    189   b.  Connector member  186  is coupled to the source of energy (not shown) and energizable element  226  of monopolar assembly  200  ( FIG. 6 ) via one or more wires (not shown) to enable the selective supply of energy to energizable element  226  upon activation of either of monopolar activation switches  182 . Safety switches  189   a,    189   b,  as detailed below, are coupled to bipolar activation assembly  170  and monopolar activation assembly  180 , respectively, via one or more wires (not shown) such that bipolar energy may only be supplied to jaw members  110 ,  120  ( FIG. 6 ) when monopolar assembly  200  is disposed in the storage condition ( FIG. 2 ), and such that monopolar energy may only be supplied to energizable member  220  ( FIG. 6 ) when monopolar assembly  200  is disposed in the use condition ( FIG. 33 ). 
     Referring to  FIGS. 1, 3, 6, and 8 , rotating assembly  70  includes rotation wheel  72  that is rotatably disposed but longitudinally constrained within a vertically-oriented slot  26  defined within housing  20 . Rotation wheel  72  extends at least partially through slot  26  on either side of housing  20  to enable manipulation of rotation wheel  72  on either exterior side of housing  20 . Rotation wheel  72 , as noted above, is mounted about the proximal end of shaft  80 . Thus, with rotation wheel  72  fixed about shaft  80 , with end effector assembly  100  engaged at the distal end of shaft  80 , with engagement pin  232  engaged to sheath assembly  210  and energizable member  220  of monopolar assembly  200  and extending through opposed longitudinal slots  152  of drive bar  142 , and with proximal foot  163  of knife bar  162  extending through elongated cut-out  150  ( FIG. 8 ) of drive bar  142 , shaft  80 , end effector assembly  100 , drive assembly  140 , knife assembly  160 , and monopolar assembly  200  are rotatably fixed relative to one another and are capable of being rotated relative to housing  20  and in cooperation with one another via rotation of rotation wheel  72 . 
     As shown in  FIG. 6 , a tube guide  90  fixedly disposed within shaft  80  may also be provided to facilitate the alignment of the various internal sliding components disposed within shaft  80 , e.g., drive bar  142 , knife assembly  160 , and energizable member  220 . More specifically, tube guide  90  defines a central lumen (not shown) configured to slidably receive drive bar  142  and first and second channels (not shown) defined within the outer periphery thereof and extending longitudinally therealong to slidably receive knife assembly  160  and energizable member  220 , respectively. U.S. patent application Ser. No. 14/196,066, previously incorporated herein by reference, details a tube guide suitable for this purpose. 
     Referring generally to  FIGS. 1, 3-5, and 7-29 , deployment and retraction mechanism  300  is configured for selectively transitioning monopolar assembly  200  between its storage condition and its use condition, although deployment and retraction mechanism  300  may similarly be used in connection with any suitable surgical instrument for deploying and retracting any suitable deployable component(s). Deployment and retraction mechanism  300  generally includes a gear box  302  mounted within housing  20 , a gear assembly  330  operably disposed within gear box  302 , a pair of rotatable actuators  380  operably coupled to the input of gear assembly  330 , and a slider  390  configured to operably engage monopolar assembly  200  with the output of gear assembly  330 . As will become apparent in view of the following, deployment and retraction mechanism  300  is configured to enable both deployment and retraction of monopolar assembly  200  in a push-push manner, e.g., wherein monopolar assembly  200  is both deployed and retracted by pushing either of rotatable actuators  380  in the same direction, return monopolar assembly  200  back to its previous condition in the event of an incomplete actuation, retain monopolar assembly  200  in the use condition or the storage condition upon a full actuation, provide an advantageous gear ratio for deploying and retracting monopolar assembly  200 , actuate movable handle  40  to approximate jaw members  110 ,  120  prior to deployment of monopolar assembly  200  if necessary, permit the supply of energy to energizable member  220  only when monopolar assembly  200  is disposed in the use condition, and permit the supply of energy to jaw members  110 ,  120  only when monopolar assembly  200  is disposed in the storage condition. 
     Referring to  FIGS. 9-11 , gear box  302  of deployment and retraction mechanism  300  is formed from first and second housing components  310 ,  320 , respectively, secured to one another in snap-fit engagement, although other configurations are also contemplated, to enclose and retain gear assembly  330  therein. First and second housing components  310 ,  320  each define three overlapping disc-shaped cavity portions  312   a,    312   b,    312   c,  and  322   a,    322   b,    322   c  that cooperate to define three overlapping cavities  304 ,  306 ,  308  within gear box housing  302 . First housing component  310  further includes a longitudinal slot  314 , a support portion  316 , and a distal aperture  319 . 
     First disc-shaped cavity portion  312   a  of first housing component  310  includes ring gear  332  of gear assembly  330  disposed on the inwardly-facing surface thereof. As detailed below, planet gear  334 , carrier member  340 , ratchet gear  350 , and disengagement plate  355  of gear assembly  330  are retained within first cavity  304  of gear box  302  in operable engagement with ring gear  332 . Longitudinal slot  314  is defined through first housing component  310  adjacent first disc-shaped cavity portion  312   a  to provide access to the interior area defined within ring gear  332 . A longitudinal track  315  defined within first housing component  310  on either side of longitudinal slot  314  and extending therealong is configured to operably engage slider  390  to guide longitudinal translation of slider  390  between the proximal and distal ends of longitudinal slot  314 . 
     Second disc-shaped cavity portion  312   b  of first housing component  310  is disposed adjacent to and in communication with first disc-shaped cavity portion  312   a.  Second cavity  306  of gear box  302  is configured to retain first and second compound gears  360 ,  365 , respectively, of gear assembly  330  in operable engagement with those components of gear assembly  330  retained within cavity  304 , e.g., ring gear  332 , planet gear  334 , carrier member  340 , ratchet gear  350 , and disengagement plate  355 . 
     Third disc-shaped cavity portion  312   c  of first housing component  310  is disposed adjacent to and in communication with second disc-shaped cavity portion  312   b.  Third cavity  308  of gear box  302  is configured to retain drive gear  370  of gear assembly  330  in operable engagement with first and second compound gears  360 ,  365 , respectively, of gear assembly  330 . Third disc-shaped cavity portion  312   c  of first housing component  310  further defines distal aperture  319  therethrough that is configured to receive pin  372 , which extends through gear box  302  in order to operably couple rotatable actuators  380  to one another and gear assembly  330 , as detailed below. 
     Support portion  316  of first housing component  310  includes a pair of posts  317  extending outwardly therefrom that are configured to support safety assembly  188 . A back plate  318  is also provided to retain safety assembly  188  on posts  317  and in position adjacent first housing component  310  such that proximal and distal safety switches  189   a,    189   b  of safety assembly  188  are maintained in position adjacent the respective proximal and distal ends of longitudinal slot  314 . Support portion  316  of first housing component  310  may additionally include cut-outs, slots, apertures, channels, or other suitable features for routing wires (not shown) to/from proximal and distal safety switches  189   a,    189   b  and/or energizable element  226  of monopolar assembly  200  ( FIG. 6 ). 
     Second housing component  320 , as mentioned above, defines three overlapping disc-shaped cavity portions  322   a,    322   b,    322   c  that are configured to cooperate with respective disc-shaped cavity portions  312   a,    312   b,    312   c  of first housing component  310  upon engagement of first and second housing components  310 ,  320  to define overlapping cavities  304 ,  306 ,  308  within gear box  302 . First disc-shaped cavity portion  322   a  of second housing component  320  defines a first post  324  extending inwardly therefrom that is configured to rotatably support carrier member  340  and ratchet gear  350  of gear assembly  330  with disengagement plate  355  of gear assembly  330  disposed therebetween. Second housing component  320  further includes a cut-out  325  adjacent first disc-shaped cavity portion  322   a  and a first pawl  326  extending into cut-out  325 . First pawl  326  is formed integrally with second housing component  320  to define a living hinge therebetween, thus permitting the free end of first pawl  326  to flex within cut-out  325  and relative to second housing component  320 . The living hinge defined between first pawl  326  second housing component  320  is configured such that first pawl  326  is biased inwardly towards first post  324 . 
     Second housing component  320  further includes a pair of radially-opposed protrusions  327  disposed on the interior surface thereof that are positioned about the perimeter of first disc-shaped cavity portion  322   a.  Disengagement plate  355  of gear assembly  330  includes a corresponding pair of radially-opposed gaps  356  defined between each pair of tabs  357  thereof that are configured to receive protrusions  327  to seat disengagement plate  355  within second housing component  320  in fixed rotational orientation relative to second housing component  320 , the important of which is detailed below. 
     Second disc-shaped cavity portion  322   b  of second housing component  320  defines a second post  328   a  extending inwardly therefrom, while a third post  328   b  extends inwardly from the overlapping region defined between second and third disc-shaped cavity portions  322   b,    322   c . Second post  328   a  is configured to rotatably support first compound gear  360  of gear assembly  330  in operable engagement with the components of gear assembly  330  retained within cavity  304 , e.g., ring gear  332 , planet gear  334 , carrier member  340 , ratchet gear  350 , and disengagement plate  355 , while third post  328   b  is configured to rotatably support second compound gear  365  in operable engagement with first compound gear  360 . 
     Third disc-shaped cavity portion  322   c  of second housing component  320  further defines a distal aperture  329  therethrough that is configured to receive pin  372 , which extends through gear box  302  in order to operably couple rotatable actuators  380  to one another and gear assembly  330 , as detailed below. Distal apertures  319 ,  329  of third disc-shaped cavity portions  312   c,    322   c  of first and second housing components  310 ,  320 , respectively, are aligned with one another and positioned such that drive gear  370  of gear assembly  330  is retained within third cavity  308  in operable engagement with second compound gear  365  of gear assembly  330 . 
     Gear assembly  330  includes ring gear  332 , planet gear  334 , carrier member  340 , ratchet gear  350 , disengagement plate  355 , first and second compound gears  360 ,  365 , and drive gear  370 . With reference to  FIGS. 11-16 , ring gear  332 , as mentioned above, is disposed on the inwardly-facing surface of first disc-shaped cavity portion  312   a  of first housing component  310 . Planet gear  334  is disposed in meshed engagement with ring gear  332  so as to permit orbiting of planet gear  334  about the interior perimeter of ring gear  332 . Planet gear  334  defines a central aperture  336  about which planet gear  334  is rotatably mounted on off-center pivot  344  of carrier member  340 . Planet gear  334  further includes an off-center pin  338  extending therefrom and through longitudinal slot  314  of first housing component  310  to rotatably support slider  390  thereon. Off-center pin  338  serves as the output of gear assembly  330 . 
     The ratio of the pitch diameters of ring gear  332  and planet gear  334  is  2 : 1  such that as planet gear  334  is orbited about the interior perimeter of ring gear  332 , off-center pin  338  of planet gear  334  is translated linearly through longitudinal slot  314  of first housing component  310 . More specifically, upon a first half-orbit of planet gear  334  within ring gear  332 , off-center pin  338  is translated from the proximal end of longitudinal slot  314  to the distal end of longitudinal slot  314 . Upon completion of the second half-orbit of planet gear  334  within ring gear  332  to return planet gear  334  back to its initial position, off-center pin  338  is translated from the distal end of longitudinal slot  314  back to the proximal end of longitudinal slot  314 . As noted above, off-center pin  338  of planet gear  334  supports slider  390  thereon such that each half-orbit of planet gear translates slider  390  through track  315  from one end of longitudinal slot  314  to the other end of longitudinal slot  314 . 
     Referring to  FIGS. 7, 11, 19, and 20 , carrier member  340  of gear assembly  330  defines a central aperture  342  about which carrier member  340  is rotatably supported on first post  324  of second housing component  320  adjacent planet gear  334 . As noted above, off-center pivot  344  of carrier member  340  rotatably supports planet gear  334  thereon. Carrier member  340  is generally disc-shaped except that the outer annular periphery of carrier member  340  is irregular so as to define a pair of tangentially-facing, radially-opposed shoulders  345   a,    345   b  thereon. Carrier member  340  further includes a pair of opposed cut-outs  346   a,    346   b  defined radially between central aperture  342  and the outer annular periphery of carrier member  340 , and second and third pawls  347 ,  349  defined within respective cut-outs  346   a,    346   b.  Second and third pawls  347 ,  349  are integrally formed with carrier member  340  via respective living hinges so as to permit the free ends of second and third pawls  347 ,  349  to flex within respective cut-outs  346   a,    346   b  and relative to carrier member  340 . 
     With reference to  FIGS. 7, 11, and 18 , ratchet gear  350  defines a central aperture  351  about which ratchet gear  350  is rotatably supported on first post  324  of second housing component  320  adjacent the interior surface of second housing component  320 . A face  352  of ratchet gear  350  has a recessed portion  353   a  defining a perimeter wall  353   b.  Perimeter wall  353   b  defines a pair of radially-opposed, arcuate cut-outs  354   a,  each having a notch  354   b  disposed at either end thereof. 
     Referring to  FIGS. 7, 11 and 26 , disengagement plate  355  defines a central opening  358  defined by a pair of opposed arcuate segments  359   a  interconnected with one another at opposed pinch points  359   b.  Disengagement plate  355  further includes first and second pairs of opposed, radially-outwardly extending tabs  357 . Each pair of tabs  357  defines a gap  356  therebetween that, as mentioned above, is configured to receive one of the protrusions  327  of second housing component  320  to seat disengagement plate  355  within second housing component  320  in fixed rotational orientation relative to gear box  302 . 
     With reference to  FIGS. 7, 11 and 21 , first compound gear  360  defines a central aperture  362  about which first compound gear  360  is rotatably supported on second post  328   a  of second housing component  320 . First compound gear  360  further includes a semi-annular outer gear portion  363  disposed in meshed engagement with ratchet gear  350 , and an annular inner gear portion  364 . Second compound gear  365  defines a central aperture  366  about which second compound gear  365  is rotatably supported on third post  328   b  of second housing component  320 . Second compound gear  365  further includes a semi-annular outer gear portion  367  that is disposed in meshed engagement with annular inner gear portion  364  of first compound gear  360 , and an annular inner gear portion  368 . 
     Drive gear  370  is mounted on pin  372 , which extends through and is rotatable relative to apertures  319 ,  329  of first and second housing components  310 ,  320 , respectively. Pin  372  serves as the input of gear assembly  330 . Drive gear  370  includes a semi-annular gear portion  371  that is disposed in meshed engagement with annular inner gear portion  368  of second compound gear  365 . A torsion spring  374  is operably disposed about pin  372  and is positioned within gear box  302  between drive gear  370  and first housing component  310 . The ends of pin  372  each define a bifurcated configuration having a pair of spaced-apart arms  375 . A closure plate  376  defining a rectangular aperture  377  is disposed about one of the ends of pin  372  and is rotationally keyed thereto via receipt of arms  375  within rectangular aperture  377  of closure plate  376 . Closure plate  376  is disposed about pin  372  within housing  20  between first housing component  310  of gear box  302  and the interior surface of housing  20 . As an alternative to closure plate  376 , other suitable closure mechanisms are also contemplated such as, for example, a cam/slider mechanism. 
     A portion of each of the ends of pin  372  extends from first and second housing components  310 ,  320  through apertures  28  defined within housing  20  on either side thereof. Bases  382  of actuators  380  are mounted on the ends of pin  372  exteriorly of housing  20  and are rotationally keyed thereto via receipt of arms  375  within rectangular apertures  383  defined within bases  382  of actuators  380 . Lever portions  384  of actuators  380  extend from bases  382  and define enlarged free ends  386  to facilitate manipulation thereof. Spring clips  388  extend through rectangular apertures  383  of actuators  380  and engage the interior surface of housing  20  on either side thereof to rotatably couple actuator  380  to housing  20  and retain actuators  380  about pin  372 . 
     With reference to  FIGS. 7, 11, and 28-30 , slider  390 , as noted above, is positioned adjacent longitudinal slot  314  of first housing component  310  and is operably engaged within track  315  of first housing component  310  to enable slider  390  to translate relative to first housing component  310  between the proximal and distal ends of longitudinal slot  314 . Slider  390  includes a hub  392  defining a recess  394  that is configured to receive proximal cap  222  of energizable member  220  of monopolar assembly  200  in rotatable engagement therewith. Thus, monopolar assembly  200 , along with shaft  80 , end effector assembly  100 , drive assembly  140 , and knife assembly  160 , may be rotated together relative to housing  20  and deployment and retraction mechanism  300 , e.g., via rotation of rotation wheel  72 . 
     Referring to  FIGS. 11 and 21-30 , as can be appreciated in view of the above, gear box  302  is configured so as to operably retain semi-annular gear portion  371  of drive gear  370  in meshed engagement with annular inner gear portion  368  of second compound gear  365 , semi-annular outer gear portion  367  of second compound gear  365  in meshed engagement with annular inner gear portion  364  of first compound gear  360 , and semi-annular outer gear portion  363  of first compound gear  360  in meshed engagement with ratchet gear  350 . Further, ratchet gear  350 , disengagement plate  355 , and carrier member  340  are stacked in operable engagement with one another within cavity  304  of gear box  302  with the free ends of second and third pawls  347 ,  349  of carrier member  340  each initially disposed within one of the cut-outs  354   a  of ratchet gear  350 . In addition, planet gear  334  is pivotably coupled to carrier member  340  at an off-center position relative thereto, is disposed in meshed engagement with ring gear  332 , and is coupled to slider  390 . 
     In operation, with monopolar assembly  200  disposed in the storage condition or the use condition, the free end of first pawl  326  is engaged with one of radially-opposed shoulders  345   a,    345   b  of carrier member  340  to inhibit reverse rotation (e.g., counterclockwise rotation as viewed in  FIG. 23 ) of carrier member  340 , thereby fixing planet gear  334  and slider  390  in position and retaining monopolar assembly  200  in the storage condition or the use condition (see  FIG. 23 ). More specifically, in the storage condition, first pawl  326  is engaged with radially-opposed shoulder  345   a  to retain monopolar assembly  200  in the storage condition, while, in the use condition, first pawl  326  is engaged with the other radially-opposed shoulder  345   b  to retain monopolar assembly  200  in the use condition. 
     Upon actuation of either or both actuators  380 , e.g., upon distal urging of either or both of enlarged free ends  386  of actuators  380  relative to housing  20  to rotate actuators  380  in their forward directions, pin  372  is rotated relative to housing  20  in a forward direction to thereby rotate drive gear  370  in its forward direction which, in turn, drives rotation of second compound gear  365  in its forward direction. Such rotation of second compound gear  365  drives rotation of first compound gear  360  in its forward direction which, in turn, drives rotation of ratchet gear  350  in its forward direction. As ratchet gear  350  is rotated within cavity  302  in its forward direction, the free end of second pawl  347  of carrier member  340  is slid through the corresponding cut-out  354   a  of ratchet gear  350  until the free end of second pawl  347  is engaged within one of the notches  354   b  of ratchet gear  350  to couple carrier member  340  and ratchet gear  350  to one another (see  FIG. 24 ). Thus, upon further forward rotation of ratchet gear  350 , carrier member  340  is driven to rotate in its forward direction (e.g., clockwise as viewed in  FIG. 23 ). With planet gear  334  pivotably coupled to carrier member  340  at an off-center position relative thereto, disposed in meshed engagement within ring gear  332 , and supporting slider  390  thereon, rotation of carrier member  340  in its forward direction drives planet gear  334  to orbit in its forward direction within ring gear  332  to thereby translate slider  390  through longitudinal slot  314  to initiate deployment or retraction of monopolar assembly  200  (see  FIGS. 28 and 29 ). 
     Upon a full actuation of actuator(s)  380 , drive gear  370 , second compound gear  365 , first compound gear  360 , and ratchet gear  350  are sufficiently rotated in their respective forward directions so as to rotate carrier member  340  through a one-half revolution in its forward direction. Such a one-half revolution of carrier member  340  in its forward direction drives planet gear  334  to orbit within ring gear  332  through a half-orbit, thereby translating slider  390  through longitudinal slot  314  from either the proximal or distal end thereof to the other of the proximal or distal end thereof to transition monopolar assembly  200  from the storage condition to the use condition or from the use condition to the storage condition, respectively. Upon completion of the one-half revolution of carrier member  340 , first pawl  326  of second housing component  320  cams over the adjacent radially-opposed shoulder  345   a,    345   b  of carrier member  340  ultimately falling into engagement therewith such that reverse rotation of carrier member  340  is inhibited, thereby retaining monopolar assembly  200  in the storage condition or the use condition (see  FIG. 23 ). Further, in each of the two end rotational orientations of carrier member  340 , e.g., the positions reached upon a one-half revolution of carrier member  340 , carrier member  340  is oriented relative to disengagement plate  355  such that one of the pinch points  359   b  of disengagement plate  355  urges the free end of third pawl  349  inwardly towards the center of carrier member  340  (see  FIG. 27 ). In this position, the free end of third pawl  349  is withdrawn from the corresponding cut-out  354   a  of ratchet gear  350  to thereby disengage carrier member  340  from ratchet gear  350 . 
     Release of actuator(s)  380  after a full actuation allows the bias of torsion spring  374  to urge actuators  380  to rotate in a reverse direction back to their initial, proximal positions and likewise urges pin  372  to rotate relative to housing  20  in its reverse direction, thereby rotating drive gear  370 , second compound gear  365 , first compound gear  360 , and ratchet gear  350  in their respective reverse directions. As noted above, however, carrier member  340  is inhibited from reverse rotation once the half-revolution thereof has been achieved, due to the engagement of first pawl  326  with one of the radially-opposed shoulders  345   a,    345   b  of carrier member  340  (see  FIG. 23 ). Thus, during reverse rotation of the above-noted components, carrier member  340  is maintained fixed relative to gear box  302 . Such relative rotation of the above-noted components relative to carrier member  340  is permitted due to the fact that, as detailed above, upon completion of a full actuation, disengagement plate  355  serves to disengage carrier member  340  from ratchet gear  350 . Accordingly, carrier member  340 , planet gear  334 , and slider  390  are retained in position to retain monopolar assembly  200  in its condition, while actuators  380 , pin  372 , drive gear  370 , second compound gear  365 , first compound gear  360 , and ratchet gear  350  are returned to their initial positions. 
     Subsequent full actuations and releases of actuator(s)  380  may be effected to repeatedly transition monopolar assembly  200  between the storage condition and the use condition. As can be appreciated, upon each full actuation and release of actuators  380 , actuators  380 , pin  372 , drive gear  370 , second compound gear  365 , first compound gear  360 , and ratchet gear  350  are rotated in their respective forward directions from their initial positions to their end positions and then in their respective reverse directions from the end positions back to their initial positions. Carrier member  340  and planet gear  334 , however, are rotatable in a single direction with each full actuation, and are rotated through a half-revolution and half-orbit, respectively, with each full actuation. 
     Should actuator(s)  380  be released after only a partial-actuation, e.g., prior to being rotated through a full actuation, torsion spring  374  urges pin  372  to rotated relative to housing  20  in a reverse direction thereof, thereby rotating drive gear  370 , second compound gear  365 , first compound gear  360 , and ratchet gear  350  in their respective reverse directions, similarly as if a full actuation had been achieved. However, since carrier member  340  does not complete a one-half revolution in response to a partial actuation, first pawl  326  of second housing component  320  is not moved into engagement with one of the radially-opposed shoulders  345   a,    345   b  of carrier member  340  to inhibit reverse rotation of carrier member  340 , and carrier member  340  is not oriented such that one of the pinch points  359   b  of disengagement plate  355  urges the free end of third pawl  349  inwardly to disengage carrier member  340  from ratchet gear  350 . Rather, upon reverse rotation of ratchet gear  350  after a partial-actuation, the free end of third pawl  349  of carrier member  340  is slid through the corresponding cut-out  354   a  of ratchet gear  350  until the free end of third pawl  349  is engaged within one of the notches  354   b  of ratchet gear  350  to couple carrier member  340  and ratchet gear  350  to one another (see  FIG. 25 ). Thus, upon further rotation of ratchet gear  350  in its reverse direction under the bias of torsion spring  374 , carrier member  340  is urged, similarly as ratchet gear  350 , to rotate in its reverse direction to thereby drive planet gear  334  to orbit in its reverse direction and translate slider  390  back to its previous position, e.g., the position of slider  390  prior to the partial actuation. Put generally, the above-detailed feature returns monopolar assembly  200  back to its previous condition in the event of a partial actuation and, thus, avoids monopolar assembly  200  from stalling in an intermediate condition between the storage and use conditions. 
     With reference to  FIGS. 28 and 29 , as detailed above, safety assembly  188  is mounted on first housing component  310  of gear box  302  and includes proximal and distal safety switches  189   a,    189   b,  respectively. Proximal safety switch  189   a  inhibits the supply of energy to surfaces  112 ,  122  of jaw members  110 ,  120  ( FIG. 2 ), respectively, unless proximal safety switch  189   a  is activated, while distal safety switch  189   b  inhibits the supply of energy to energizable member  220  unless distal safety switch  189   b  is activated. Proximal safety switch  189   a  is operably positioned adjacent the proximal end of longitudinal slot  314  of first housing component  310  such that slider  390  activates proximal safety switch  189   a  only when disposed at the proximal end of longitudinal slot  314  (corresponding to the storage condition of monopolar assembly  200  ( FIG. 32 )). Distal safety switch  189   b  is operably positioned adjacent the distal end of longitudinal slot  314  of first housing component  310  such that slider  390  activates distal safety switch  189   b  only when disposed at the distal end of longitudinal slot  314  (corresponding to the use condition of monopolar assembly  200  ( FIG. 32 )). Thus, energy may only be supplied to surfaces  112 ,  122  of j aw members  110 ,  120  ( FIG. 2 ), respectively, when monopolar assembly  200  ( FIG. 32 ) is disposed in the storage condition, and energy may only be supplied to energizable member  220  of monopolar assembly  200  ( FIG. 32 ) when monopolar assembly  200  ( FIG. 32 ) is disposed in the use position. 
     With reference to  FIGS. 1, 2, and 32-35 , as also detailed above, deployment and retraction assembly  300  includes a closure plate  376  that is rotationally keyed to pin  372  and positioned within housing  20 . Closure plate  376  defines a generally rectangular configuration (although other configurations are also contemplated) and is operably positioned relative to finger  48  of flange  46  of movable handle  40  such that, if movable handle  40  has not been compressed to sufficiently approximate jaw members  110 ,  120  so as to permit passage of elongated insulative sheath  214  thereabout prior to actuation of deployment and retraction mechanism  300 , the rotation of closure plate  376  upon actuation of actuator(s)  380  serves to do so. More specifically, upon actuation of actuator(s)  380  with movable handle  40  disposed in its in initial positon or an insufficiently compressed position, closure plate  376  is rotated into contact with finger  48  to urge finger  48  distally, thereby urging movable handle  40  to rotate towards the compressed position to approximate (or further approximate) jaw members  110 ,  120 . Closure plate  376  is oriented about pin  372  such that this approximation (or further approximation) of jaw members  110 ,  120  is effected prior to advancement of elongated insulative sheath  214  about jaw members  110 ,  120 , thus ensuring that jaw members  110 , 120  are sufficiently approximated so as to permit uninhibited advancement of elongated insulative sheath  214  about jaw members  110 ,  120  to the use position. With respect to retraction, once elongated insulative sheath  214  has cleared jaw members  110 ,  120 , closure plate  376  is rotated out of contact with finger  48 , thus permitting movable handle  40  to return to its initial position corresponding to the spaced-apart position of jaw members  110 ,  120 . As noted above, as an alternative to closure plate  376 , a cam/slider mechanism operably coupled to pin  372  may be provided for urging movable handle  40  to rotate towards the compressed position to approximate (or further approximate) jaw members  110 ,  120  upon actuation of actuator(s)  380  with movable handle  40  disposed in its in initial positon or an insufficiently compressed position. In such embodiments, rather than having closure plate  376  itself urge movable handle  40  towards the compressed position, the cam washer (not shown), which is rotationally keyed to pin  372 , is urged into contact with a cam slider (not shown) which, in turn, is translated into contact with movable handle  40  to urge movable handle  40  to rotate towards the compressed position. 
     Referring to  FIGS. 1, 2, and 28-35 , the use and operation of instrument  10  in both the bipolar mode, e.g., for grasping, treating (for example, sealing), and/or cutting tissue, and the monopolar mode, e.g., for electrical/electromechanical tissue treatment, is described. With respect to use in the bipolar mode, monopolar assembly  200  is maintained in the storage condition, wherein elongated insulative sheath  214  is positioned proximally of jaw members  110 ,  120 , distal tissue-treating portion  227  of energizable member  220  is disposed adjacent jaw flanges  114 ,  124  of jaw members  110 ,  120 , respectively, of end effector assembly  100 . In use, instrument  10  is inserted through a cannula, access port, other access device, or directly into a surgical site such that end effector assembly  100  is positioned adjacent tissue to be treated in the bipolar mode of operation. At this point, movable handle  40  may be moved to the initial position such that jaw members  110 ,  120  are disposed in the spaced-apart position. Further, trigger  62  of trigger assembly  60  remains un-actuated at this point such that knife  164  ( FIG. 6 ) remains disposed in its retracted position. 
     With jaw members  110 ,  120  disposed in the spaced-apart position, end effector assembly  100  may be further manipulated into position and/or rotated, e.g., via rotation of rotation wheel  72 , such that tissue to be grasped, treated, and/or cut, is disposed between jaw members  110 ,  120 . Next, movable handle  40  is compressed towards fixed handle  50  such that jaw member  110  is pivoted relative to jaw member  120  from the spaced-apart position to the approximated position to grasp tissue therebetween. In this approximated position, and since monopolar assembly  200  is disposed in the storage condition at this point, movable handle  40  may be further compressed, e.g., beyond the point indicated via clicker tab  52  ( FIG. 3 ), such that button activation post  49  depresses depressible button  174  to supply energy to surface  112  of jaw member  110  and/or surface  122  of jaw member  120  for conduction through tissue to treat tissue. Once tissue treatment is complete (or to cut untreated tissue), knife  164  ( FIG. 6 ) may be deployed between jaw members  110 ,  120 , e.g., via actuation of trigger  62  of trigger assembly  60 , to cut tissue grasped between jaw members  110 ,  120 . 
     When tissue cutting is complete, trigger  62  may be released to return knife  164  ( FIG. 6 ) to the retracted position. Thereafter, movable handle  40  may be released or returned to its initial position such that jaw members  110 ,  120  are moved back to the spaced-apart position to release the treated and/or divided tissue. 
     For operation of instrument  10  in the monopolar mode, jaw members  110 ,  120  are first moved to the approximated position, e.g., by compressing movable handle  40  relative to fixed handle  50 . However, as detailed above, deployment and retraction mechanism  300  includes a closure feature that operates to urge movable handle  40  towards the compressed position to approximate jaw members  110 ,  120  upon deployment of monopolar assembly  200 , if such has not been done manually prior to deployment. Thus, manual movement of jaw members  110 ,  120  to the approximated position via compression of movable handle  40  prior to deployment of monopolar assembly  200  need not be performed. 
     Next, either or both actuators  380  are rotated through a full actuation stroke to deploy monopolar assembly  200  from the storage condition ( FIG. 2 ) to the use condition ( FIG. 33 ), wherein elongated insulative sheath  214  is extended about jaw members  110 ,  120  and distal tissue-treating portion  227  of energizable member  220  is extended distally from jaw members  110 ,  120 . As can be appreciated, proximal ferrule  212  of monopolar assembly  200 , which is fixed relative to housing  20 , serves as a buffer between elongated insulative sheath  214  and the cannula, access port, or other access device (not shown), e.g., the instrument seal thereof, and/or between elongated insulative sheath  214  and tissue to reduce friction and inhibit catching of elongated insulative sheath  214  upon deployment and retraction of monopolar assembly  200  and rotation of monopolar assembly  200  relative to housing  20 . Upon full actuation, actuator(s)  380  may be released, allowing actuators  380  to return to their initial positions while monopolar assembly  200  is maintained in the use condition. As noted above, if only a partial actuation is effected, monopolar assembly  200  is instead returned with actuators  380  to its previous condition, e.g., the storage condition. 
     With monopolar assembly  200  disposed in the use condition, either of activation buttons  184  may be depressed to supply energy to distal tissue-treating portion  227  of energizable member  220  to treat tissue therewith. During application of energy to distal tissue-treating portion  227 , instrument  10  may be moved relative to tissue, e.g., longitudinally, transversely, and/or radially, to facilitate electromechanical treatment of tissue. At the completion of tissue treatment, either or both of actuators  380  may be actuated through a full actuation a subsequent time to return monopolar assembly  200  to the storage condition. 
     The various embodiments disclosed herein may also be configured to work with robotic surgical systems and what is commonly referred to as “Telesurgery.” Such systems employ various robotic elements to assist the surgeon in the operating room and allow remote operation (or partial remote operation) of surgical instrumentation. Various robotic arms, gears, cams, pulleys, electric and mechanical motors, etc. may be employed for this purpose and may be designed with a robotic surgical system to assist the surgeon during the course of an operation or treatment. Such robotic systems may include remotely steerable systems, automatically flexible surgical systems, remotely flexible surgical systems, remotely articulating surgical systems, wireless surgical systems, modular or selectively configurable remotely operated surgical systems, etc. 
     The robotic surgical systems may be employed with one or more consoles that are next to the operating theater or located in a remote location. In this instance, one team of surgeons or nurses may prep the patient for surgery and configure the robotic surgical system with one or more of the instruments disclosed herein while another surgeon (or group of surgeons) remotely control the instruments via the robotic surgical system. As can be appreciated, a highly skilled surgeon may perform multiple operations in multiple locations without leaving his/her remote console which can be both economically advantageous and a benefit to the patient or a series of patients. 
     The robotic arms of the surgical system are typically coupled to a pair of master handles by a controller. The handles can be moved by the surgeon to produce a corresponding movement of the working ends of any type of surgical instrument (e.g., end effectors, graspers, knifes, scissors, etc.) which may complement the use of one or more of the embodiments described herein. The movement of the master handles may be scaled so that the working ends have a corresponding movement that is different, smaller or larger, than the movement performed by the operating hands of the surgeon. The scale factor or gearing ratio may be adjustable so that the operator can control the resolution of the working ends of the surgical instrument(s). 
     The master handles may include various sensors to provide feedback to the surgeon relating to various tissue parameters or conditions, e.g., tissue resistance due to manipulation, cutting or otherwise treating, pressure by the instrument onto the tissue, tissue temperature, tissue impedance, etc. As can be appreciated, such sensors provide the surgeon with enhanced tactile feedback simulating actual operating conditions. The master handles may also include a variety of different actuators for delicate tissue manipulation or treatment further enhancing the surgeon&#39;s ability to mimic actual operating conditions. 
     From the foregoing and with reference to the various drawing figures, those skilled in the art will appreciate that certain modifications can also be made to the present disclosure without departing from the scope of the same. While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.