Patent Publication Number: US-2020297406-A1

Title: Surgical instrument

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/458,228, filed on Mar. 14, 2017, which is a continuation of U.S. patent application Ser. No. 14/196,066, filed on Mar. 4, 2014, now U.S. Pat. No. 9,655,673, which claims the benefit of the filing date of provisional U.S. Patent Application No. 61/776,136, filed on Mar. 11, 2013. 
    
    
     INTRODUCTION 
     The present disclosure relates generally to the field of surgical instruments. In particular, the disclosure relates to an endoscopic electrosurgical forceps that is economical to manufacture and is capable of sealing and cutting relatively large tissue structures. 
     BACKGROUND 
     Instruments such as electrosurgical forceps are commonly used in open and endoscopic surgical procedures to coagulate, cauterize and seal tissue. Such forceps typically include a pair of jaw members that can be controlled by a surgeon to grasp targeted tissue, such as, e.g., a blood vessel. The jaw members may be approximated to apply a mechanical clamping force to the tissue, and are associated with at least one electrode to permit the delivery of electrosurgical energy to the tissue. The combination of the mechanical clamping force and the electrosurgical energy has been demonstrated to join adjacent layers of tissue captured between the jaw members. When the adjacent layers of tissue include the walls of a blood vessel, sealing the tissue may result in hemostasis, which may facilitate the transection of the sealed tissue. A detailed discussion of the use of an electrosurgical forceps may be found in U.S. Pat. No. 7,255,697 to Dycus et al. 
     A bipolar electrosurgical forceps typically includes opposed electrodes disposed on clamping faces of the jaw members. The electrodes are charged to opposite electrical potentials such that an electrosurgical current may be selectively transferred through tissue grasped between the electrodes. To effect a proper seal, particularly in relatively large vessels, two predominant mechanical parameters must be accurately controlled; the pressure applied to the vessel, and the gap distance established between the electrodes. 
     Both the pressure and gap distance influence the effectiveness of the resultant tissue seal. If an adequate gap distance is not maintained, there is a possibility that the opposed electrodes will contact one another, which may cause a short circuit and prevent energy from being transferred through the tissue. Also, if too low a force is applied the tissue may have a tendency to move before an adequate seal can be generated. The thickness of a typical effective tissue seal is optimally between about 0.001 and about 0.006 inches. Below this range, the seal may shred or tear and above this range the vessel walls may not be effectively joined. Closure pressures for sealing large tissue structures preferably fall within the range of about 3 kg/cm 2  to about 16 kg/cm 2 . 
     SUMMARY 
     The present disclosure relates to an electrosurgical apparatus and methods for performing electrosurgical procedures. More particularly, the present disclosure relates to electrosurgically sealing tissue. 
     The present disclosure describes an electrosurgical instrument for treating tissue that is economical to manufacture and is capable of sealing and cutting relatively large tissue structures. 
     The electrosurgical instrument includes a housing including an elongated shaft having distal and proximal portions. The proximal portion is coupled to the housing. As is traditional, the term “distal” refers herein to an end of the apparatus that is farther from an operator, and the term “proximal” refers herein to the end of the electrosurgical forceps that is closer to the operator. 
     The elongated shaft defines a longitudinal axis. A stationary actuation member is axially disposed within the elongated shaft and includes a cam pin mechanically coupled to a distal end thereof. An actuating mechanism is operably coupled to the proximal portion of the elongated shaft and is moveable relative to the housing to selectively cause movement of the elongated shaft along the longitudinal axis relative to the stationary actuation member. An end effector includes a pair of opposing first and second jaw members operably coupled about a common pivot such that at least one of the jaw members is movable relative to the other jaw member from a first position wherein the jaw members are disposed in spaced relation relative to one another to a second position wherein the jaw members cooperate to grasp tissue therebetween. At least one of the first and second jaw members includes a camming slot configured to engage the cam pin to move the at least one movable jaw member between the first position and the second position upon movement of the elongated shaft along the longitudinal axis. Each jaw member includes an electrically conductive tissue sealing surface. Each tissue sealing surface is adapted to connect to a source of electrosurgical energy for conducting electrosurgical energy through tissue grasped therebetween to effect a tissue seal. A knife blade is supported in the elongated shaft and is moveable in a longitudinal direction through a knife channel defined along a length of at least one of the jaw members to cut tissue disposed between the jaw members. A switch is supported by the housing and is configured to be engaged by the actuating mechanism to initiate delivery of electrosurgical energy from the electrosurgical energy source to the end effector to treat tissue. 
     Additionally or alternatively, the switch is operably coupled to a depressible button extending from the housing. The button is configured to be selectively engaged by the actuating mechanism to activate the switch. 
     Additionally or alternatively, the second jaw member is mechanically coupled to a distal end of the elongated shaft and the first jaw member is configured to move relative to the second jaw member. 
     Additionally or alternatively, the stationary actuation member includes a longitudinal recess formed along a length thereof. The longitudinal recess is configured to permit movement of the pivot pin in a longitudinal direction upon movement of the elongated shaft. 
     Additionally or alternatively, the actuation mechanism is configured to engage a mechanical interface disposed within the housing. The mechanical interface is configured to generate a response to engagement with the actuation mechanism upon movement thereof relative to the housing. The mechanical interface may be constructed of a plastic film or the mechanical interface may be constructed of sheet metal. The response may be tactile and/or audible and may correspond to the second position of at least one jaw member. Additionally or alternatively, the response may indicate a position of the actuation mechanism relative to the switch. 
     Additionally or alternatively, the actuation mechanism includes a handle moveable relative to the housing between a distal position to move at least one jaw member to the first position and a proximal position to move the at least one jaw member to the second position. The handle may engage the switch upon movement of the handle to the proximal position. 
     Additionally or alternatively, movement of the knife blade in a longitudinal direction is prevented when the handle is in the distal position. 
     Additionally or alternatively, at least one of the jaw members includes an insulator coupled thereto. The insulator may be configured to electrically insulate the electrically conductive tissue sealing surface from the jaw member. The insulator may form at least one knife blade guide configured to guide the knife into the knife channel. 
     Additionally or alternatively, the insulator is configured to control splay of at least one of the jaw members. 
     According to another aspect of the present disclosure, an electrosurgical instrument is provided. The electrosurgical instrument includes a housing and an elongated shaft coupled to the housing and defining a longitudinal axis. An actuating mechanism is operably coupled to the elongated shaft and moveable relative to the housing to selectively cause movement of the elongated shaft along the longitudinal axis. An end effector is supported by the elongated shaft and is adapted for treating tissue. The end effector includes first and second jaw members pivotally coupled to one another to move between open and closed configurations. Each of the jaw members includes a camming surface. A switch is supported by the housing and is configured to be engaged by the actuating mechanism to initiate treatment of tissue. A knife rod extends at least partially through the elongated shaft and is selectively movable in a longitudinal direction. A blade operably coupled to the knife rod is extendable through a knife channel defined along a length of at least one of the jaw members. An inner actuation member extends at least partially through the elongated shaft and the elongated shaft is selectively movable in a longitudinal direction with respect to the knife and with respect to the inner actuation member. The inner actuation member carries a cam pin positioned to engage the camming surface of each of the jaw members to induce the jaw members to move between the open and closed configurations. 
     According to another aspect of the present disclosure, an electrosurgical system for performing electrosurgery is provided. The electrosurgical system includes an electrosurgical generator configured to provide electrosurgical energy and an electrosurgical instrument. The electrosurgical instrument includes a housing including an elongated shaft having distal and proximal portions. The proximal portion is coupled to the housing. The elongated shaft defines a longitudinal axis. A stationary actuation member is axially disposed within the elongated shaft and includes a cam pin mechanically coupled to a distal end thereof. An actuating mechanism is operably coupled to the proximal portion of the elongated shaft and is moveable relative to the housing to selectively cause movement of the elongated shaft along the longitudinal axis relative to the stationary actuation member. An end effector includes a pair of opposing first and second jaw members operably coupled about a common pivot such that at least one of the jaw members is movable relative to the other jaw member from a first position wherein the jaw members are disposed in spaced relation relative to one another to a second position wherein the jaw members cooperate to grasp tissue therebetween. At least one of the first and second jaw members includes a camming slot configured to engage the cam pin to move the at least one movable jaw member between the first position and the second position upon movement of the elongated shaft along the longitudinal axis. Each jaw member includes an electrically conductive tissue sealing surface. Each tissue sealing surface is configured to connect to the electrosurgical generator for conducting electrosurgical energy through tissue grasped therebetween to effect a tissue seal. A knife blade is supported in the elongated shaft and is moveable in a longitudinal direction through a knife channel defined along a length of at least one of the jaw members to cut tissue disposed between the jaw members. A switch is supported by the housing and is configured to be engaged by the actuating mechanism to initiate delivery of electrosurgical energy from the electrosurgical generator to the end effector to treat tissue. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the detailed description of the embodiments given below, serve to explain the principles of the disclosure. 
         FIG. 1  is a perspective view of an electrosurgical forceps according to an embodiment of the present disclosure including a housing, an elongated shaft, and an end effector; 
         FIG. 2A  is an enlarged, perspective view of the end effector of  FIG. 1  depicted with a pair of jaw members in an open configuration; 
         FIG. 2B  is an enlarged, perspective view of the end effector of  FIG. 1  depicted with the pair of jaw members in a closed configuration; 
         FIG. 3A  is a perspective view of the end effector and elongated shaft of  FIG. 1  with parts separated; 
         FIG. 3B  is cross-sectional view taken along line  3 B- 3 B of  FIG. 3A  showing a distal portion of the electrosurgical forceps of  FIG. 1  depicting a tube guide; 
         FIG. 3C  is a perspective view of another knife blade and knife bar configuration for use with the end effector and elongated shaft of  FIG. 1 ; 
         FIG. 3D  is an enlarged, perspective view of the area of detail indicated in  FIG. 3C ; 
         FIG. 3E  is a perspective view of a portion of another elongated shaft, similar to the elongated shaft of  FIG. 1 , configured for use with the end effector of  FIG. 1 ; 
         FIG. 4  is a proximally-facing, perspective view of a rotation knob depicting a passageway for receiving the elongated shaft of  FIG. 1 ; 
         FIG. 5  is a cross-sectional, perspective view of the end effector of  FIG. 1 ; 
         FIG. 6  is a partial, proximal-facing perspective view of a distal portion of a jaw actuation mechanism of the end effector of  FIG. 1 ; 
         FIG. 7  is a partial, distal-facing perspective view of distal portion of a knife actuation mechanism of the end effector of  FIG. 1 ; 
         FIG. 8  is a perspective view of a lower jaw member of the end effector of  FIG. 1 ; 
         FIG. 8A  is an enlarged, perspective view of a portion of another lower jaw member, similar to the lower jaw member of  FIG. 8 , configured for use with the end effector of  FIG. 1 ; 
         FIG. 9  is a cross-sectional, perspective view of the lower jaw member of  FIG. 8 ; 
         FIG. 10  is a perspective view of a proximal portion of the instrument of  FIG. 1  with a portion of the housing removed revealing internal components; 
         FIG. 10A  is a cross-sectional view of another switch and activation button configured for use with the instrument of  FIG. 1 ; 
         FIG. 11  is a partial, side view of a proximal portion of the instrument of  FIG. 1 ; 
         FIG. 12A  is a perspective view of a proximal portion of the knife actuation mechanism of the end effector of  FIG. 1 ; 
         FIG. 12B  is a cross-sectional, side view of a knife collar of the knife actuation mechanism of the end effector of  FIG. 1 ; 
         FIG. 13A  is a side view of the proximal portion of the instrument of  FIG. 10  depicting a movable handle in a separated position with respect to a stationary handle, which corresponds to the open configuration of the end effector depicted in  FIG. 2A , and a knife trigger in a separated configuration with respect to the stationary handle, which corresponds to an un-actuated or proximal configuration of a knife with respect to the jaw members; 
         FIG. 13B  is a side view of the proximal portion of the instrument of  FIG. 10  depicting the movable handle in an intermediate position with respect to the stationary handle, which corresponds to a first closed configuration of the end effector wherein the jaw members encounter one another; 
         FIG. 13C  is a side view of the proximal portion of the instrument of  FIG. 10  depicting the movable handle in an approximated configuration with respect to the stationary handle, which corresponds to a second closed configuration of the end effector wherein the jaw members apply an appropriate pressure to generate a tissue seal; and 
         FIG. 13D  is a side view of the proximal portion of the instrument of  FIG. 10  depicting the knife trigger in an actuated configuration, which corresponds to an actuated or distal position of the knife with respect to the jaw members. 
     
    
    
     DETAILED DESCRIPTION 
     Referring initially to  FIG. 1 , an electrosurgical forceps  100  generally includes a housing  112  that supports various actuators thereon for remotely controlling an end effector  114  through an elongated shaft  116 . Although this configuration is typically associated with instruments for use in laparoscopic or endoscopic surgical procedures, various aspects of the present disclosure may be practiced with traditional open instruments and in connection with endoluminal procedures as well. The housing  112  is constructed of a left housing half  112   a  and a right housing half  112   b . The left and right designation of the housing halves  112   a ,  112   b  refer to the respective directions as perceived by an operator using the forceps  100 . The housing halves  112   a ,  112   b  may be constructed of sturdy plastic, and may be joined to one another by adhesives, ultrasonic welding or other suitable assembly methods. 
     To mechanically control the end effector  114 , the housing  112  supports a stationary handle  120 , a movable handle  122 , a trigger  126  and a rotation knob  128 . The movable handle  122  is operable to move the end effector  114  between an open configuration ( FIG. 2A ) wherein a pair of opposed jaw members  130 ,  132  are disposed in spaced relation relative to one another, and a closed or clamping configuration ( FIG. 2B ) wherein the jaw members  130 ,  132  are closer together. Approximation of the movable handle  122  with the stationary handle  120  serves to move the end effector  114  to the closed configuration and separation of the movable handle  122  from the stationary handle  120  serves to move the end effector  114  to the open configuration. The trigger  126  is operable to extend and retract a knife blade  156  (see  FIGS. 2A and 2B ) through the end effector  114  when the end effector  114  is in the closed configuration. The rotation knob  128  serves to rotate the elongated shaft  116  and the end effector  114  about a longitudinal axis A-A extending through the forceps  114 . 
     To electrically control the end effector  114 , the stationary handle  120  supports a depressible button  137  thereon, which is operable by the user to initiate and terminate the delivery of electrosurgical energy to the end effector  114 . The depressible button  137  is mechanically coupled to a switch  136  ( FIGS. 13A-13D ) disposed within the stationary handle  120  and is engageable by a button activation post  138  extending from a proximal side of the moveable handle  122  upon proximal movement of the moveable handle  122  to an actuated or proximal position ( FIG. 13C ). The switch  136  is in electrical communication with an electrosurgical generator  141  via suitable electrical wiring (not explicitly referenced) extending from the housing  112  through a cable  143  extending between the housing  112  and the electrosurgical generator  141 . The generator  141  may include devices such as the LigaSure® Vessel Sealing Generator and the ForceTriad® Generator sold by Covidien. The cable  143  may include a connector (not shown) thereon such that the forceps  100  may be selectively coupled electrically to the generator  141 . 
     Referring now to  FIGS. 2A-3A , the end effector  114  may be moved from the open configuration ( FIG. 2A ) wherein tissue (not shown) is received between the jaw members  130 ,  132 , and the closed configuration ( FIG. 2B ), wherein the tissue is clamped and treated. The jaw members  130 ,  132  pivot about a pivot pin  144  to move the end effector  114  to the closed configuration of  FIG. 2B  wherein the sealing plates  148 ,  150  provide a pressure to tissue grasped therebetween. In some embodiments, to provide an effective tissue seal, a pressure within a range between about 3 kg/cm2 to about 16 kg/cm2 and, desirably, within a working range of about 7 kg/cm2 to about 13 kg/cm2, may be applied to the tissue. Also, in the closed configuration, a separation or gap distance is maintained between the sealing plates  148 ,  150  by an array of stop members  154  ( FIG. 2A ) disposed on or adjacent the sealing plates  148 ,  150 . The stop members  154  contact opposing surfaces on the opposing jaw member  130 ,  132  and prohibit further approximation of the sealing plates  148 ,  150 . In some embodiments, to provide an effective tissue seal, an appropriate gap distance of about 0.001 inches to about 0.010 inches and, desirably, between about 0.002 inches to about 0.005 inches, may be provided. In some embodiments, the stop members  154  are constructed of a heat-resistant ceramic deposited onto the jaw members  130 ,  132 . In other embodiments, the stop members  154  are constructed of an electrically non-conductive plastic molded onto the jaw members  130 ,  132 , e.g., by a process such as overmolding or injection molding. The stop members  154  may define any suitable number, arrangement, and/or configuration, depending on a particular purpose. 
     Referring momentarily to  FIG. 8A , another embodiment of a lower jaw member  132 ′ is shown. Lower jaw member  132 ′ is similar to lower jaw member  132  ( FIGS. 2A-3A ) except as detailed below. Lower jaw member  132 ′ includes a sealing plate  148 ′ having a plurality of stop members  154 ′ disposed thereon in any suitable configuration. A wetting ring  155 ′ defined within the sealing plate  148 ′ is disposed about each of the stop members  154 ′. Wetting rings  155 ′ may be formed via etching or other suitable process and are formed on sealing plate  148 ′ prior to depositing (or otherwise forming) the stop members  154 ′. Upon depositing the ceramic onto sealing plate  148 ′ to form the stop members  154 ′ (or prior to otherwise forming the stop members  154 ′), wetting rings  155 ′ facilitate the formation of each of the stop members  154 ′ in a particular shape, e.g., circular, thus providing greater shape uniformity among the plurality of stop members  154 ′. 
     Referring again to  FIGS. 2A-3A , upper and lower jaw members  130 ,  132  are electrically coupled to cable  143 , and thus to the generator  141  (e.g., via respective suitable electrical wiring extending through the elongated shaft  116 ) to provide an electrical pathway to a pair of electrically conductive, tissue-engaging sealing plates  148 ,  150  disposed on the lower and upper jaw members  132 ,  130 , respectively. The sealing plate  148  of the lower jaw member  132  opposes the sealing plate  150  of the upper jaw member  130 . In some embodiments, the sealing plates  148  and  150  are electrically coupled to opposite terminals, e.g., positive or active (+) and negative or return (−) terminals associated with the generator  141 . Thus, bipolar energy may be provided through the sealing plates  148  and  150  to tissue. Alternatively, the sealing plates  148  and  150  may be configured to deliver monopolar energy to tissue. In a monopolar configuration, one or both sealing plates  148  and  150  deliver electrosurgical energy from an active terminal, e.g., (+), while a return pad (not shown) is placed generally on a patient and provides a return path to the opposite terminal, e.g., (−), of the generator  141 . Each jaw member  130 ,  132  includes a jaw insert  140  and an insulator  142  that serves to electrically insulate the sealing plates  150 ,  148  from the jaw insert  140  of the jaw members  130 ,  132 , respectively. 
     Electrosurgical energy may be delivered to the tissue through the electrically conductive seal plates  148 ,  150  to effect a tissue seal. Once a tissue seal is established, a knife blade  156  having a sharpened distal edge  157  may be advanced through a knife channel  158  defined in one or both jaw members  130 ,  132  to transect the sealed tissue. Although the knife blade  156  is depicted in  FIG. 2A  as extending from the elongated shaft  116  when the end effector  114  is in an open configuration, in some embodiments, extension of the knife blade  156  into the knife channel  158  when the end effector  114  is in the open configuration is prevented, as discussed below with reference to  FIGS. 13A-13D . 
     Referring to  FIG. 3A , the elongated shaft  116  includes various longitudinal components that operatively couple the end effector  114  to the various actuators supported by the housing  112  ( FIG. 1 ). An outer shaft member  160  defines an exterior surface of the elongated shaft  116  and houses other components therein as described below. The outer shaft member  160  is configured for longitudinal motion with respect to an inner actuation member  180  axially received within the outer shaft member  160 . The inner actuation member  180  may be a rod, a shaft, a tube, folded metal, stamped metal, or other suitable structure. A proximal portion  166  of the outer shaft member  160  is configured for receipt within the housing  112  ( FIG. 1 ), and includes features for operatively coupling the outer shaft member  160  to various elements of the housing  112 . More specifically, the proximal portion  166  of the outer shaft member  160  includes, in order from distal to proximal, a longitudinal slot  169  to couple the outer shaft member  160  to the rotation knob  128 , a longitudinal knife slot  168  defined therethrough, a pair of opposing distal locking slots  161   a ,  161   b , and a pair of opposing proximal locking slots  171   a ,  171   b . The connection established between the outer shaft member  160  and the rotation knob  128  is described below with reference to  FIG. 4 . 
     A distal portion  186  of the inner actuation member  180  includes a longitudinal recess  190  defined therein that provides clearance for the pivot pin  144  and thus, permits longitudinal reciprocation of the pivot pin  144  (via longitudinal reciprocation of the outer shaft member  160 ) independent of the inner actuation member  180 . Distally of the longitudinal recess  190 , a cam pin  192  is mechanically coupled (e.g., via welding, friction-fit, laser welding, etc) to the distal portion  186  of the inner actuation member  180 . A proximal portion  188  of the inner actuation member  180  includes a washer  187  coupled thereto ( FIG. 10 ). The washer  187  is captured within the housing  112  and serves to prohibit longitudinal motion of the inner actuation member  180  parallel to the longitudinal axis A-A. 
     The pivot pin  144  extends through a proximal portion of each of the jaw members  130 ,  132  to pivotally support the jaw members  130 ,  132  at the distal end of the inner actuation member  180 . A proximal portion of each of the jaw members  130 ,  132  includes two laterally spaced parallel flanges or “flags”  130   a ,  130   b  and  132   a ,  132   b  respectively, extending proximally from a distal portion of the jaw members  130  and  132  ( FIGS. 3A, 5, and 7-9 ). A lateral cam slot  130   c  and a lateral pivot bore  130   d  extend through each of the flags  130   a ,  130   b  of the upper jaw member  130  ( FIG. 3A ). Similarly, a lateral cam slot  132   c  and a lateral pivot bore  132   d  extend through each of the flags  132   a ,  132   b  of the lower jaw member  132  ( FIGS. 8 and 9 ). The pivot bores  130   d ,  132   d  receive the pivot pin  144  in a slip-fit relation that permits the jaw members  130 ,  132  to pivot about the pivot pin  144  to move the end effector  114  between the open and closed configurations ( FIGS. 2A and 2B , respectively). 
     A knife rod  102  is coupled (e.g., via welding) at a distal-most end to the sharpened knife blade  156  and includes an angled proximal end  108  that provides a mechanism for operatively coupling the knife rod  102  to the trigger  126 . In some embodiments, the angled proximal end  108  of the knife rod  102  is formed by bending the knife rod  102  ninety degrees at its proximal end during manufacturing. The connection between the knife rod  102  and the trigger  126  is described in detail below with reference to  FIGS. 10, 11, 12A, and 12B . The sharpened distal edge  157  of the knife blade  156  may be applied to the distal end of the knife blade  156  using a variety of manufacturing techniques such as, for example, grinding, coining, electrochemical etching, electropolishing, or other suitable manufacturing technique, for forming sharpened edges. 
     Referring to  FIGS. 3A and 3B , a tube guide  109  is disposed within the outer shaft member  160  and includes a lumen  107  axially disposed therethrough. The inner actuation member  180  is received within the guide lumen  107 , which serves to orient and align the inner actuation member  180  within the outer shaft member  160 . The knife rod  102  is received within a longitudinal guide recess  105  formed in the outer surface of the guide tube  109 . The guide recess  105  serves to guide longitudinal motion of the knife rod  102  within the outer shaft member  160  and to radially space the knife rod  102  from the inner actuation member  180  to prevent the inner actuation member  180  from interfering with reciprocal motion of the knife rod  102 . 
     Referring now to  FIG. 4 , the rotation knob  128  includes a distal portion  125  extending distally therefrom and a passageway  129  defined therethrough for receiving the outer shaft member  160 . The passageway  129  has a generally circular profile corresponding to the circular profile of the outer shaft member  160 . The passageway  129  includes a longitudinal keying member  124  that is configured to align with and be seated within longitudinal slot  169  ( FIG. 3A ) of the outer shaft member  160 . The keying member  124  projects laterally inward along the length of passageway  129  such that the insertion of the outer shaft member  160  into the passageway  129  of the rotation knob  128  operatively couples the outer shaft member  160  to the rotation knob  128 . Rotational motion imparted to the rotation knob  128  may thus impart rotational motion to each of the components of the elongated shaft  116 , and to the end effector  114 , which is coupled thereto. As shown in  FIGS. 10, 11, and 13A-13D , the rotation knob  128  is supported in the housing  112  and, as shown in  FIG. 1 , extends radially outward from opposing sides of the housing  112  (only shown extending radially outward from housing half  112   b ). 
     Referring now to  FIG. 5 , the end effector  114  is coupled to the distal end of the inner actuation member  180  by the cam pin  192 . The cam pin  192  represents a longitudinally stationary reference for longitudinal movement of the outer shaft member  160  and the knife rod  102 . The cam pin  192  extends through the flags  132   a ,  132   b  of the lower jaw member  132  and the flags  130   a  and  130   b  of the upper jaw member  130 . 
     Referring now to  FIG. 6 , the end effector  114  is shown in the open configuration. Since the inner actuation member  180  is coupled to the cam pin  192 , when the outer shaft member  160  (removed from view in  FIG. 6  for clarity) is in an unactuated or distal position such that the inner actuation member  180  is in a proximal position relative to the outer shaft member  160 , the cam pin  192  is located in a proximal position in cam slots  130   c  and  132   c  defined through the flags  130   a ,  130   b ,  132   a ,  132   b  of the jaw members  130 ,  132 , respectively. 
     The outer shaft member  160  may be drawn proximally relative to the inner actuation member  180  and the cam pin  192  to move the end effector  114  to the closed configuration (see  FIG. 2B ). Since the longitudinal position of the cam pin  192  is fixed, and since the cam slot  130   c  is obliquely arranged with respect to the longitudinal axis A-A, proximal retraction of the outer shaft member  160  induces distal translation of the cam pin  192  through the cam slots  130   c ,  132   c  such that the jaw member  130  pivots toward jaw member  132  about the pivot pin  144 . Conversely, when the end effector  114  is in the closed configuration, longitudinal translation of the outer shaft member  160  in a distal direction induces proximal translation of the cam pin  192  through the cam slots  130   c ,  132   c  such that jaw member  130  pivots away from jaw member  132  toward the open configuration. 
     In some embodiments, the inner actuation member  180  may be configured to move relative to the outer shaft member  160  to move the end effector  114  between the open and closed configurations. In this scenario, the moveable handle  122  may be operably coupled to the inner actuation member  180  and the washer  187  coupled to the proximal portion  188  of the inner actuation member  180  may be removed such that the inner shaft member  180  is free to move longitudinally along the longitudinal axis A-A upon actuation of the moveable handle  122 . Proximal retraction of the inner actuation member  180  may induce proximal translation of the cam pin  192  through the cam slots  130   c ,  132   c  such that the jaw member  130  pivots away from jaw member  132  about the pivot pin  144  toward the open configuration. Conversely, when the end effector  114  is in the open configuration, longitudinal translation of the inner actuation member  180  in a distal direction induces distal translation of the cam pin  192  through the cam slots  130   c ,  132   c  such that jaw member  130  pivots toward jaw member  132  toward the closed configuration. 
     Referring now to  FIG. 7 , the pins  144 ,  192  do not interfere with the reciprocal motion of the knife blade  156 . A proximal portion of the insulator  142  forms a blade guide  152  (also see  FIGS. 5, 8, and 9 ) that serves to align the knife blade  156  such that the knife blade  156  readily enters the knife channel  158  defined in the jaw members  130 ,  132  (jaw member  130  removed from view in  FIG. 7  for clarity). 
     Referring now to  FIGS. 8 and 9 , the lower jaw member  132  is constructed of three major components: the jaw insert  140 , the insulator  142 , and the sealing plate  148 . The flags  132   a ,  132   b  of the jaw member  132  define a proximal portion of the jaw insert  140  and a generally u-shaped profile of the jaw insert  140  extends distally to support the tissue engaging portion of the jaw member  132 . Upper jaw member  130  includes the same three major components as lower jaw member  132 , including sealing plate  150 , jaw insert  140 , and insulator  142 , and is constructed in the same manner as lower jaw member  132 . However, lower jaw member  132  is fixedly engaged, e.g., welded, to outer shaft member  160 , while upper jaw member  130  is pivotable relative to lower jaw member  132  and outer shaft member  160  between the open and closed configurations. In order to facilitate alignment of lower jaw member  132  and, more particularly, jaw insert  140  of lower jaw member  132 , with outer shaft member  160  during welding (or other suitable fixed engagement), jaw insert  140  and outer shaft member  160  may include complementary alignment features, e.g., a complementary recess (not explicitly shown) defined within jaw insert  140  and a complementary protrusion (not explicitly shown) extending from outer shaft member  160 . As an alternative to the unilateral configuration detailed above, both of the upper and lower jaw members  130 ,  132 , respectively, may be pivotable relative to one another and outer shaft member  160 , thus defining a bilateral configuration. 
     The insulator  142  of jaw members  130 ,  132  may be constructed of an electrically insulative plastic such as a polyphthalamide (PPA) (e.g., Amodel®), polycarbonate (PC), acrylonitrile butadiene styrene (ABS), a blend of PC and ABS, nylon, ceramic, etc. The insulator  142  may be overmolded onto the jaw insert  140  in either a single-shot or a two-shot injection molding process such that each of the sealing plates  148 ,  150  are coupled to and in spaced relation with their respective jaw inserts  140 . Additionally or alternatively, the insulator  142  may be mechanically coupled to the jaw insert  140 , e.g., pressed, snapped, glued, etc. Various features may be molded into the insulator  142  that facilitate the attachment of the sealing plates  148 ,  150  to the jaw inserts  140 . For example, tabs may be provided that permit a snap-fit attachment, or ridges may be formed that permit ultrasonic welding of the sealing plates  148 ,  150  onto the insulators  142 . In some embodiments, the insulator  142  on the lower jaw member  132  forms a tissue stop  142   a  extending therefrom adjacent to the knife channel  158  and proximal to the sealing plate  148 . The tissue stop  142   a  serves to prevent tissue from entering the distal end of the outer shaft member  160  and to prevent splay of the flags  130   a ,  130   b  of the upper jaw member  130 . In some embodiments, the tissue stop  142   a  may be formed by the insulator  142  on the upper jaw member  130  or on both the upper jaw member  130  and the lower jaw member  132 . The tissue stop  142   a  may also serve to align the knife blade  156  as the knife blade  156  enters the knife channel  158  defined in the jaw members  130 ,  132 . To this end, the surface of the tissue stop  142   a  extending along the path of the knife blade  156  may define a chamfered configuration to further facilitate alignment of the knife blade  156  as the knife blade  156  enters the knife channel  158 . 
     Referring now to  FIG. 10 , the connection of the movable handle  122  and the knife trigger  126  to the longitudinally movable components of the elongated shaft  116  is described. The movable handle  122  may be manipulated to impart longitudinal motion to the outer shaft member  160 , and the knife trigger  126  may be manipulated to impart longitudinal motion to the knife rod  102 . As discussed above, longitudinal motion of the outer shaft member  160  serves to move the end effector  114  between the open configuration of  FIG. 2A  and the closed configuration of  FIG. 2B , and longitudinal motion of the knife rod  102  serves to move knife blade  156  through knife channel  158  ( FIG. 2A ). 
     The movable handle  122  is operatively coupled to the outer shaft member  160  by a clevis  178  defined at an upper end of the movable handle  122 . The clevis  178  is pivotally supported on the housing  112 . The clevis  178  extends upwardly about opposing sides of a drive collar  184  ( FIG. 11 ) supported on the outer shaft member  160  and includes rounded drive surfaces  197   a  and  197   b  thereon. Drive surface  197   a  engages a proximal-facing surface of a distal spring washer  184   a  and drive surface  197   b  engages a distal facing surface of a proximal rim  184   b  of the drive collar  184  ( FIG. 11 ). The distal spring washer  184   a  engages a proximal facing surface of a distal spring stop  184   c  that, in turn, engages the opposing distal locking slots  161   a ,  161   b  ( FIG. 3A ) extending through the proximal portion  166  ( FIG. 3A ) of the outer shaft member  160  to couple the distal spring stop  184   c  to the outer shaft member  160 . The drive surfaces  197   a ,  197   b  are arranged along the longitudinal axis A-A such that pivotal motion of the movable handle  122  induces corresponding longitudinal motion of the drive collar  184  ( FIG. 11 ) along the longitudinal axis A-A. 
     Referring now to  FIG. 11 , proximal longitudinal motion may be imparted to the outer shaft member  160  by pushing the proximal rim  184   b  of the drive collar  184  proximally with the movable handle  122  ( FIG. 10 ) as indicated by arrow D 4  ( FIG. 11 ). A spring  189  is constrained between a proximal facing surface of the drive collar  184  and a proximal spring stop  115 . The proximal spring stop  115  engages the opposing proximal locking slots  171   a ,  171   b  ( FIG. 3A ) extending through the proximal portion  166  ( FIG. 3A ) of the outer shaft member  160  to couple the proximal spring stop  115  to the outer shaft member  160 . Thus, the proximal spring stop  115  serves as a proximal stop against which spring  189  compresses. 
     Distal longitudinal motion is imparted to the outer shaft member  160  by driving the drive collar  184  distally with the movable handle  122  ( FIG. 10 ). Distal longitudinal motion of the drive collar  184  induces a corresponding distal motion of the outer shaft member  160  by virtue of the coupling of the drive collar  184  to opposing distal locking slots  181   a ,  181   b  extending through the proximal portion  166  of the outer shaft member  160  ( FIG. 3A ). In some embodiments, a kick-out spring  199  is positioned between proximal spring stop  115  and a portion of housing  112  to ensure full return of outer shaft member  160  distally upon release or return of movable handle  122  ( FIG. 10 ). The kick-out spring  199  may include a pair of plate surfaces interconnected via living hinges, as shown, although any other suitable spring may be provided. 
     Proximal longitudinal motion of the outer shaft member  160  draws jaw member  132  proximally such that the cam pin  192  advances distally to pivot jaw member  130  toward jaw member  132  to move the end effector  114  to the closed configuration as described above with reference to  FIG. 6 . Once the jaw members  130  and  132  are closed, the outer shaft member  160  essentially bottoms out (i.e., further proximal movement of the outer shaft member  160  is prohibited since the jaw members  130 ,  132  contact one another). Further proximal movement of the movable handle  122  ( FIG. 10 ), however, will continue to move the drive collar  184  proximally. This continued proximal movement of the drive collar  184  further compresses the spring  189  to impart additional force to the outer shaft member  160 , which results in additional closure force applied to tissue grasped between the jaw members  130 ,  132  (see  FIG. 2B ). 
     Referring again to  FIG. 10 , the trigger  126  is pivotally supported in the housing  112  about a pivot boss  103  protruding from the trigger  126 . The trigger  126  is operatively coupled to the knife rod  102  by a knife connection mechanism  104  such that pivotal motion of the trigger  126  induces longitudinal motion of the knife rod  102 . The knife connection mechanism  104  includes upper flanges  126   a ,  126   b  of the trigger  126  and a knife collar  110 . 
     Referring now to  FIGS. 11, 12A, and 12B , the knife collar  110  includes a pair of integrally formed pin bosses  139   a ,  139   b  extending from opposing sides thereof. As shown by  FIG. 12B , the knife collar  110  includes an interior circular channel  113  that captures the angled proximal end  108  of the knife rod  102  to couple the knife rod  102  to the knife collar  110 . Referring momentarily to  FIGS. 3C and 3D , in conjunction with  FIG. 12B , in some embodiments, the proximal end  108 ′ of the knife rod  102 ′ may alternatively define a hooked configuration to help further inhibit disengagement of the proximal end  108 ′ of the knife rod  102 ′ from within the channel  113  of the knife collar  110 . In such embodiments, as shown in  FIG. 3E , the knife slot  168 ′ defined within the outer shaft member  160 ′ further includes an angled portion  168   a ′ disposed at the proximal end thereof to accommodate the hooked proximal end  108 ′ of the knife rod  102 ′. 
     Referring again to  FIGS. 11, 12A, and 12B , longitudinal motion of the outer shaft member  160 , the angled proximal end  108  of the knife rod  102  translates longitudinally within knife slot  168  ( FIG. 3A ) of the outer shaft member  160  such that the longitudinal motion of outer shaft member  160  is unimpeded by the angled proximal end  108  of the knife rod  102 . Upon rotation of the elongated shaft  116  and end effector  114  about the longitudinal axis A-A via the rotation knob  128  ( FIG. 1 ), the angled proximal end  108  of the knife rod  102  freely rotates within the interior circular channel  113  of the knife collar  110  such that the outer and inner actuation members  160  and  180  (removed from view in  FIG. 12B  for clarity), and the knife rod  102  rotate within the knife collar  110  about the longitudinal axis A-A. In this way, the knife collar  110  serves as a stationary reference for the rotational movement of the outer shaft member  160 , the inner actuation member  180 , and the knife rod  102 . 
     Referring again to  FIG. 10 , the upper flanges  126   a ,  126   b  of the trigger  126  include respective slots  127   a ,  127   b  defined therethrough that are configured to receive the pin bosses  139   a ,  139   b , respectively, of the knife collar  110  such that pivotal motion of the trigger  126  induces longitudinal motion of the knife collar  110  and, thus, the knife rod  102  by virtue of the coupling of knife rod  102  to the knife collar  110 . 
     Referring now to  FIGS. 11 and 12A , when the trigger  126  is moved to induce motion of the knife collar  110  in order to translate the blade  156  through the knife channel  158 , the knife collar  110  translates along the outer shaft member  160  in the direction of arrow A 5  to abut a spring  119  such that spring  119  compresses against the distal portion  125  of the rotation knob  128  ( FIG. 12A ). The spring  119  biases the knife collar  110  proximally along the outer shaft member  160 . With reference to  FIG. 3C , in some embodiments, a hard stop  156   a ′ formed at the proximal end of knife blade  156 ′ is provided for interference with the pivot pin  144  of end effector  114  ( FIG. 2B ) to limit the travel distance, e.g., extension, of knife blade  156 ′. 
     Referring now to  FIGS. 13A, 13B, 13C and 13D , a sequence of motions may be initiated by moving the movable handle  122  to induce motion of the outer shaft member  160  in order to close the jaws  130 ,  132 , and by moving the trigger  126  to induce motion of the knife collar  110  in order to translate the blade  156  through the knife channel  158 . Initially, both the moveable handle  122  and the knife trigger  126  are in a distal or un-actuated position as depicted in  FIG. 13A . This arrangement of the moveable handle  122  and trigger  126  sustains the end effector  114  in the open configuration ( FIG. 2A ) wherein the jaw members  130 ,  132  are substantially spaced from one another, and the knife blade  156  is in a retracted or proximal position with respect to the jaw members  130 ,  132 . When both the moveable handle  122  and the knife trigger  126  are in the distal, un-actuated position, pivotal motion of the knife trigger  126  in a proximal direction, i.e., toward the stationary handle  120 , is passively prohibited by interference between the trigger  126  and moveable handle  122 . This interference prohibits advancement of the knife blade  156  through the knife channel  158  when the end effector  114  is in the open configuration. Movable handle  122  may additionally include a protrusion (not shown) or other feature extending distally therefrom that is configured to contact the trigger  126  upon return of the movable handle  122  distally towards the un-actuated position, thereby returning the trigger  126  towards its un-actuated position if not previously returned via the spring  119  ( FIG. 11 ). 
     The movable handle  122  may be moved from the distal position of  FIG. 13A  to the intermediate position depicted in  FIG. 13B  to move the jaw members  130 ,  132  to the closed configuration ( FIG. 2B ). As the movable handle  122  pivots in the direction of arrow M 1  ( FIG. 13B ), the drive surface  197   b  of the movable handle  122  engages the proximal rim  184   b  of the drive collar  184 . The drive collar  184  is driven proximally such that the spring  189  biases the proximal spring stop  115  and, thus, the outer shaft member  160  is driven proximally in the direction of arrow M 2  ( FIG. 13B ). As discussed above with reference to  FIG. 6 , proximal movement of the outer shaft member  160  serves to translate the cam pin  192  distally though the cam slots  130   c ,  132   c  ( FIG. 3A ) of the jaw members  130 ,  132 , respectively, and thus pivot jaw member  130  toward jaw member  132  ( FIG. 2B ). As the jaw members  130 ,  132  engage one another and no further pivotal movement of the jaw members  130 ,  132  may be achieved, further distal movement of the cam pin  192  and further proximal movement of the outer shaft member  160  are prevented. 
     As the movable handle  122  is moved from the distal position of  FIG. 13A  to the intermediate position depicted in  FIG. 13B , a tooth  122   a  extending proximally from an upper portion of the moveable handle  122  engages a clicker tab  120   a  supported within the stationary handle  120  to generate a tactile and/or an audible response. The clicker tab  120   a  may be constructed of a plastic film, sheet metal, or any suitable material configured to generate a “clicking” sound as the clicker tab  120   a  is engaged and disengaged by the tooth  122   a . This response generated by the clicker tab  120   a  corresponds to a complete grasping of tissue between the jaw members  130 ,  132  and serves to indicate to the surgeon that further pivotal motion of the moveable handle  122  in a proximal direction, i.e., toward the stationary handle  120 , will cause the button activation post  138  to engage the depressible button  137 . As the moveable handle  122  is moved from the intermediate position of  FIG. 13B  to the actuated or proximal position of  FIG. 13C , the button activation post  138  depresses the depressible button  137 , thereby activating the switch  136  disposed within the stationary handle  120  to initiate the delivery of electrosurgical energy to the end effector  114  to generate a tissue seal. 
     With reference to  FIG. 10A , in some embodiments, the depressible button  137 ′ includes an inner button member  137   a ′ operably coupled to the switch  136 ′, an outer button member  137   b ′ disposed about the inner button member  137   a ′, and a spring  137   c ′ disposed between the inner and outer button members  137   a ′,  137   b ′, respectively. In order to activate the switch  136 ′ in such a configuration, the moveable handle  122  ( FIG. 10 ) is moved to the actuated position such that the button activation post  138  ( FIG. 10 ) depresses the outer button member  137   b ′ which, in turn, compresses and urges the spring  137   c  into contact with the inner button member  137   a ′ to depress the inner button member  137   a ′ and activate the switch  136 ′. This configuration is advantageous at least in that the biasing force of spring  137   c ′ maintains the switch  136 ′ in an activated state even if handle  122  ( FIG. 10 ) is returned slightly, e.g., moved distally a slight distance. Thus, accidental release of some of the pressure on handle  122  ( FIG. 10 ) will not deactivate the switch  136 ′. 
     Referring again to  FIGS. 13A, 13B, 13C and 13D , the movable handle  122  is moved from the intermediate position of  FIG. 13B  to the actuated or proximal position of  FIG. 13C , the pressure applied by the jaw members  130 ,  132  is increased. As the movable handle  122  pivots further in the direction of arrow M 3  ( FIG. 13C ), the drive surface  197   b  presses the proximal rim  184   b  of the drive collar  184  further proximally against the spring  189  in the direction of arrow M 4  ( FIG. 13C ). The spring  189  is compressed against the proximal spring stop  115 , and a tensile force is transmitted through the outer shaft member  160  to the jaw members  130 ,  132 . The tensile force supplied by the spring  189  ensures that the jaw members  130 ,  132  apply an appropriate pressure to effect a tissue seal. 
     When the movable handle  122  is in the actuated or proximal position, the knife trigger  126  may be selectively moved from the distal position of  FIG. 13C  to the proximal position of  FIG. 13D  to advance the knife blade  156  distally through knife channel  158 . The knife trigger  126  may be pivoted in the direction of arrow M 5  ( FIG. 13D ), about pivot boss  103  to advance the flanges  126   a ,  126   b  of the knife trigger  126  distally in the direction of arrow M 6  such that the pin bosses  139   a ,  139   b  translate within respective slots  127   a ,  127   b  from the position shown in  FIGS. 13A-13C  to the position shown in  FIG. 13D  (flange  126   b , pin boss  139   b , and slot  127   b  are obstructed from view in  FIGS. 13A-13D ). Movement of flanges  126   a ,  126   b  draws the knife collar  110  distally, which induces distal longitudinal motion of the knife rod  102  by virtue of the coupling of the knife rod  102  to the knife collar  110 , as described above with reference to  FIG. 12B . 
     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 examples of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto. 
     Although the foregoing disclosure has been described in some detail by way of illustration and example, for purposes of clarity or understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims.