Patent Document

BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to an electrosurgical forceps, and, more particularly, the present disclosure relates to an endoscopic electrosurgical forceps for sealing and/or cutting large tissue structures. 
         [0003]    2. Background of Related Art 
         [0004]    Electrosurgical forceps utilize both mechanical clamping action and electrical energy to affect hemostasis by heating the tissue and blood vessels to coagulate, cauterize and/or seal tissue. Many surgical procedures require cutting and/or ligating large blood vessels and large tissue structures. Due to the inherent spatial considerations of the surgical cavity, surgeons often have difficulty suturing vessels or performing other traditional methods of controlling bleeding, e.g., clamping and/or tying-off transected blood vessels or tissue. By utilizing an elongated electrosurgical forceps, a surgeon can either cauterize, coagulate/desiccate, dissect, and/or simply reduce or slow bleeding simply by controlling the intensity, frequency and duration of the electrosurgical energy applied through the jaw members to the tissue. Most small blood vessels, i.e., in the range below two millimeters in diameter, can often be closed using standard electrosurgical instruments and techniques. However, larger vessels can be more difficult to close using these standard techniques. 
         [0005]    In order to resolve many of the known issues described above and other issues relevant to cauterization and coagulation, a technology was developed by Valleylab, Inc. of Boulder, Colo., a division of Tyco Healthcare LP (now Covidien—Energy Based Devices) called vessel or tissue sealing. The process of coagulating vessels is fundamentally different than electrosurgical vessel sealing. For the purposes herein, “coagulation” is defined as a process of desiccating tissue wherein the tissue cells are ruptured and dried. “Vessel sealing” or “tissue sealing” is defined as the process of liquefying the collagen in the tissue so that it reforms into a fused mass with limited demarcation between opposing tissue structures. Coagulation of small vessels is sufficient to permanently close them, while larger vessels and tissue need to be sealed to assure permanent closure. 
         [0006]    In order to effectively seal larger vessels (or tissue) two predominant mechanical parameters are accurately controlled—the pressure applied to the vessel (tissue) and the gap distance between the electrodes—both of which are affected by the thickness of the sealed vessel. More particularly, accurate application of pressure is important to oppose the walls of the vessel; to reduce the tissue impedance to a low enough value that allows enough electrosurgical energy through the tissue; to overcome the forces of expansion during tissue heating; and to contribute to the end tissue thickness which is an indication of a good seal. 
         [0007]    Providing an instrument which consistently provides the appropriate closure force between opposing electrode within a preferred pressure range will enhance the chances of a successful seal. It has been found that the pressure range for assuring a consistent and effective seal for large vessels and tissue structures is between about 3 kg/cm2 to about 16 kg/cm2 and, desirably, within a working range of 7 kg/cm2 to 13 kg/cm2. As can be appreciated, manufacturing an instrument which is capable of consistently providing a closure pressure within these working ranges is quite a design challenge for instrument manufacturers. 
         [0008]    It may be necessary for a surgeon to perform both vessel sealing and dissection during certain surgical procedures. In such procedures, a greater number of instruments may be required to achieve the surgical objective. The use of greater numbers of instruments may affect surgical outcomes, due in part to the need to perform instrument changes in which additional time is used to withdraw one instrument, to prepare a subsequent instrument for use, and to manipulate the subsequent instrument into position for performing the required surgical steps. 
       SUMMARY 
       [0009]    An electrosurgical instrument is herein disclosed having the capability of being selectively operated in a monopolar mode and/or a bipolar mode. The disclosed instrument includes a housing having a shaft affixed thereto. The shaft includes a longitudinal axis defined therethrough and a pair of end effectors, e.g., jaw members, disposed at a distal end thereof. The end effectors are adapted to selectively connect to a source of electrosurgical energy such that the end effectors are capable of supplying energy in a monopolar mode wherein energy flows from the instrument, through tissue, and to a return pad positioned on the patient, and, additionally or alternatively, wherein the end effectors are capable of supplying energy in a bipolar wherein energy is conducted through tissue held therebetween to affect tissue sealing. A switch assembly provided by the instrument housing is adapted to selectively activate monopolar energy and/or bipolar energy. The disclosed instrument includes at least one momentary pushbutton switch that is configured to activate bipolar energy, and at least one momentary pushbutton switch that is configured to activate monopolar energy. In an envisioned embodiment, the disclosed instrument includes two monopolar activation pushbutton positioned on opposite sides of the handle to facilitate ambidextrous operation of the instrument. 
         [0010]    In an embodiment, the disclosed instrument includes a switch assembly disposed within the instrument housing. The switch assembly includes a switch carrier that includes a handle pivot mount which may be integrally formed therewith. A generally cruciform flex circuit assembly is positioned on an exterior surface of the switch housing. The flex circuit assembly includes at least one snap dome switch disposed on a multi-layer flexible printed circuit membrane. A snap dome switch is a momentary switch contact that, when used in conjunction with a printed circuit board, flex circuit, or membrane, forms a normally-open tactile switch. Metal domes may be placed on a substrate printed circuit board, flex circuit, or membrane circuit board by means of pressure-sensitive adhesive tape. In their relaxed state, the metal domes rest on the outer rim of an outer contact. When pushed, the dome collapses and establishes contact between the outer contact and an inner contact, thereby completing an electrical circuit. Actuation of a snap dome switch therefore causes electrical continuity to be established between corresponding traces provided by the circuit membrane. An edge connector provided by the flex circuit assembly enables circuit traces to be operatively coupled in electrical communication with, e.g., a source of electrosurgical energy such as without limitation an electrosurgical generator and/or a controller thereof. A wire harness may be provided within the instrument handle that is adapted to operably couple the flex circuit assembly edge connector to a connection cable. The connection cable may extend at least in part from the exterior of the instrument housing. Additionally or alternatively, the wire harness may be integrally formed with the connection cable. The flex circuit assembly includes at least two resistive circuit elements arranged to form a voltage dividing network that is adapted to cause an activation signal having a predetermined voltage to be generated in response to actuation of a snap dome switch. The switch assembly may include at least one ergonomic keytop configured to extend through a corresponding opening defined in the instrument housing which couples actuation force from, e.g., a finger of a user, to an underlying snap dome switch on the circuit membrane. 
         [0011]    The instrument includes a movable handle which is rotatable about a pivot to force a drive flange of the drive assembly to move the jaw members between the first and second positions. A selectively advanceable knife assembly is included having a knife bar which moves a knife to cut tissue between jaw members. A knife lockout mechanism operatively connects to the drive assembly. Movement of the drive assembly moves the lockout mechanism from a first orientation in obstructive relationship with the knife bar to prevent movement thereof to a second position which allows selective, unencumbered movement of the knife bar to cut tissue disposed between the jaw members. 
         [0012]    In another aspect, the disclosed instrument includes a monopolar activation lockout that is configured to inhibit monopolar mode activation when the end effector, e.g., jaws, are in a first (e.g., open) position. A monopolar safety switch is included within the switch assembly. A cam provided by the movable handle engages the safety switch when the movable handle is in the second (e.g., closed) position thereby enabling the activation of monopolar energy. 
         [0013]    A drive assembly having a selectively advanceable drive sleeve is configured to move the jaw members relative to one another 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 are closer to one another for manipulating tissue. 
         [0014]    In one embodiment, the drive assembly includes a drive stop disposed near the proximal end thereof. The drive stop is operatively engaged with the knife lockout mechanism such that selective movement of the drive assembly causes the drive stop to move or rotate the knife lockout mechanism between the first position and the second position. 
         [0015]    In another embodiment, the knife bar includes a generally t-shaped proximal end dimensioned to operatively engage a corresponding slot defined within the housing. The slot configured to guide the movement of the knife bar during translation thereof. The knife lockout mechanism may be dimensioned to obstruct the t-shaped proximal end of the knife bar when disposed in the first position. The knife assembly may include a cuff at the distal end of the knife bar which is dimensioned to encapsulate and move atop the drive sleeve upon movement of the knife bar. 
         [0016]    In yet another embodiment, the knife bar is operatively coupled to a knife slidingly disposed within the shaft and the forceps further includes a finger actuator operatively coupled to the knife assembly. Movement of the finger actuator moves the knife bar which, in turn, moves the knife to cut tissue disposed between the jaw members. 
         [0017]    A finger actuator may be operatively connected to the knife assembly. The finger actuator includes two generally u-shaped flanges which rotate about a pivot to abut and force the cuff distally which, in turn, results in distal translation of the knife bar. A spring may also be included which biases the knife assembly in a proximal-most orientation. A spring may also be included which biases the knife lockout mechanism in the first position. 
         [0018]    Another embodiment of the present disclosure includes a housing having a shaft affixed thereto. The shaft includes a longitudinal axis defined therethrough and a pair of jaw members disposed at a distal end thereof. The jaw members are adapted to connect to a source of electrosurgical energy such that the jaw members are capable of conducting energy through tissue held therebetween to affect a tissue seal. A drive assembly having a selectively advanceable drive sleeve is configured to move the jaw members relative to one another 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 are closer to one another for manipulating tissue. 
         [0019]    A movable handle is included which is rotatable about a pivot to force a drive flange of the drive assembly to move the jaw members between the first and second positions. The pivot is located a fixed distance above the longitudinal axis and the drive flange is located generally along the longitudinal axis. A knife assembly is included which has a knife bar with a t-shaped proximal end. The knife assembly is selectively movable to advance the knife bar which, in turn, moves a knife to cut tissue between jaw members. 
         [0020]    A knife lockout mechanism operatively connects to the drive assembly. Movement of the drive sleeve of the drive assembly pivots the knife lockout mechanism between a first orientation in obstructive relationship with the t-shaped proximal end of the knife bar to prevent movement thereof to a second position which allows selective, unencumbered movement of the t-shaped proximal end of the knife bar to reciprocate the knife to cut tissue disposed between the jaw members. 
         [0021]    In one aspect, the present disclosure provides an electrosurgical switch assembly that includes a switch carrier and a flex circuit assembly disposed on an exterior surface of the switch carrier. The flex circuit includes at least one monopolar switch configured to selectively activate a source of monopolar electrosurgical energy. Also included is a monopolar safety switch that is designed to enable (e.g., enable activation of) the at least one monopolar switch when the monopolar safety switch is actuated. The switch assembly also includes a bipolar switch that is configured to selectively activate a source of bipolar electrosurgical energy. 
         [0022]    Also disclosed is an electrosurgical forceps and system, comprising a housing having a shaft affixed thereto. The shaft includes jaw members at a distal end thereof that are configured to move relative to one another from a first (e.g., open) position, wherein the jaw members are disposed in spaced relation relative to one another, to a second (e.g., closed) position wherein the jaw members are closer to one another for manipulating tissue. A switch assembly as described herein is included within the housing. The electrosurgical forceps and system includes a movable handle configured to cause the jaw members to move between the first and second positions and to actuate the monopolar safety switch when the jaw members are in the second position. The disclosed electrosurgical forceps and system may additionally include a source of electrosurgical energy, which may be configured to provide monopolar electrosurgical energy and/or bipolar electrosurgical energy. 
         [0023]    Also disclosed is a method for performing electrosurgery, comprising the steps of providing an electrosurgical forceps that includes a housing having a shaft affixed thereto. the shaft includes jaw members at a distal end thereof, a drive mechanism which causes the jaw members to move relative to one another between an open position to a closed position for manipulating tissue, and a switch assembly that includes a supporting member and a flexible membrane circuit having a monopolar activation switch, a bipolar activation switch, and a monopolar safety switch. A determination is made as to whether the jaw members are in a closed position or an open position. If the jaw members are in a closed position, the monopolar activation switch is enabled (e.g., made ready for use), while if the jaw members are not in a closed position (e.g., in an open position), the monopolar activation switch is disabled. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Various embodiments of the subject instrument are described herein with reference to the drawings wherein: 
           [0025]      FIG. 1A  is a perspective view of a bipolar forceps shown in open configuration and including a housing, a shaft, a handle assembly, a movable handle, a trigger assembly, a button assembly, and an end effector assembly according to the present disclosure; 
           [0026]      FIG. 1B  is a perspective view of the bipolar forceps of  FIG. 1A  shown in closed configuration; 
           [0027]      FIG. 2A  is a side, cutaway view of the forceps of  FIG. 1A  shown in an open configuration; 
           [0028]      FIG. 2B  is a side, cutaway view of the forceps of  FIG. 1A  shown in a closed configuration; 
           [0029]      FIG. 3A  is side view of a handle assembly in accordance with the present disclosure; 
           [0030]      FIG. 3B  is perspective view of a handle assembly in accordance with the present disclosure; 
           [0031]      FIG. 3C  is perspective view of another handle assembly in accordance with the present disclosure; 
           [0032]      FIG. 4A  is a perspective view of a switch assembly carrier in accordance with the present disclosure; 
           [0033]      FIG. 4B  is a top, rear view of a switch assembly carrier in accordance with the present disclosure; 
           [0034]      FIG. 4C  is a bottom, front view of a switch assembly carrier in accordance with the present disclosure; 
           [0035]      FIG. 4D  is a top view of a switch assembly carrier in accordance with the present disclosure; 
           [0036]      FIG. 4E  is a bottom view of a switch assembly carrier in accordance with the present disclosure; 
           [0037]      FIG. 4F  is a side view of a switch assembly carrier in accordance with the present disclosure; 
           [0038]      FIG. 4G  is a side, cutaway view of a switch assembly carrier in accordance with the present disclosure; 
           [0039]      FIG. 5A  is a perspective view of a monopolar switch keytop in accordance with the present disclosure; 
           [0040]      FIG. 5B  is a side view of the monopolar switch keytop of  FIG. 5A ; 
           [0041]      FIG. 6A  is a perspective view of a bipolar switch keytop in accordance with the present disclosure; 
           [0042]      FIG. 6B  is a side view of the bipolar switch keytop of  FIG. 6A ; 
           [0043]      FIG. 7  is a electrical schematic diagram of a switch assembly in accordance with the present disclosure; 
           [0044]      FIG. 8A  is a view of a bottom circuit layer of a flex circuit assembly in accordance with the present disclosure; 
           [0045]      FIG. 8B  is a view of an adhesive spacer layer of a flex circuit assembly in accordance with the present disclosure; 
           [0046]      FIG. 8C  is a view of a top circuit layer of a flex circuit assembly in accordance with the present disclosure; 
           [0047]      FIG. 8D  is a view of a flex circuit assembly in accordance with the present disclosure; 
           [0048]      FIG. 9  is an exploded view of a flex circuit assembly in accordance with the present disclosure; 
           [0049]      FIG. 10  is an exploded view of a switch assembly in accordance with the present disclosure; and 
           [0050]      FIG. 11  is a perspective view of a switch assembly in accordance with the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0051]    Particular embodiments of the present disclosure will be described hereinbelow with reference to the accompanying drawings; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure, which may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure. 
         [0052]    In the drawings and in the descriptions that follow, the terms “proximal”, as is traditional, shall refer to the end of the instrument that is closer to the user, while the term “distal” shall refer to the end that is farther from the user. 
         [0053]    Turning now to  FIGS. 1A ,  1 B,  2 A, and  2 B, an embodiment of a forceps  10  is shown. The forceps  10  is adapted for use in various surgical procedures and generally includes a housing  20 , a handle assembly  30 , a rotating assembly  80 , a trigger assembly  70 , a switch assembly  180 , and an end effector assembly  100  which mutually cooperate to grasp, seal and divide large tubular vessels and large vascular tissues. Although the majority of the figure drawings depict a forceps  10  for use in connection with endoscopic surgical procedures, the present disclosure may be used for more traditional open surgical procedures. For the purposes herein, the forceps  10  is described in terms of an endoscopic instrument, however, it is contemplated that an open version of the forceps may also include the same or similar operating components and features as described below. 
         [0054]    Forceps  10  includes a shaft  12  that has a distal end  16  dimensioned to mechanically engage the end effector assembly  100  and a proximal end  14  that mechanically engages the housing  20 . The proximal end  14  of shaft  12  is received within the housing  20 . 
         [0055]    Forceps  10  also includes an electrosurgical cable  305  that connects the forceps  10  to a source of electrosurgical energy, e.g., a generator  500  (shown schematically). It is contemplated that generators such as those sold by Valleylab, Inc. (now Covidien), may be used as a source of electrosurgical energy, e.g., Ligasure™ Generator, FORCE EZ™ Electrosurgical Generator, FORCE FX™ Electrosurgical Generator, FORCE 1CT™, FORCE 2™ Generator, SurgiStat™ II or other envisioned generators which may perform different or enhanced functions. One such system is described in commonly-owned U.S. Pat. No. 6,033,399 entitled “ELECTROSURGICAL GENERATOR WITH ADAPTIVE POWER CONTROL”. Other systems have been described in commonly-owned U.S. Pat. No. 6,187,003 entitled “BIPOLAR ELECTROSURGICAL INSTRUMENT FOR SEALING VESSELS”. 
         [0056]    In one embodiment, the generator  500  includes various safety and performance features including isolated output, independent activation of accessories. It is envisioned that the electrosurgical generator includes Covidien&#39;s Instant Response™ technology features which provides an advanced feedback system to sense changes in tissue 200 times per second and adjust voltage and current to maintain appropriate power. The Instant Response™ technology is believed to provide one or more of the following benefits to surgical procedure, including consistent clinical effect through all tissue types; reduced thermal spread and risk of collateral tissue damage; less need to “turn up the generator”; and is well-adapted to the minimally invasive environment. 
         [0057]    Cable  305  is internally divided into control leads (not explicitly shown) that are adapted to transmit electrical potentials through their respective feed paths through the forceps  10  to the switch assembly  180 . Cable  305  may additionally or alternatively include energy leads (not explicitly shown) that are designed to transmit electrical potentials through their respective feed paths through the forceps  10  to the end effector assembly  100 . Details relating to the electrical connections are explained in more detail below with the discussion of the switch assembly  180 . 
         [0058]    Handle assembly  30  includes a fixed handle  50  and a movable handle  40 . Fixed handle  50  is integrally associated with housing  20  and handle  40  is movable relative to fixed handle  50  as explained in more detail below with respect to the operation of the forceps  10  and switch assembly  180 . Fixed handle  50  is oriented approximately 30 degrees relative a longitudinal axis A-A defined through shaft  12 . Fixed handle  50  may include one or more ergonomic enhancing elements to facilitate handling, e.g., scallops, protuberances, elastomeric material, etc. Rotating assembly  80  is operatively associated with the housing  20  and is rotatable approximately 180 degrees about a longitudinal axis A-A (See  FIG. 1A ). 
         [0059]    As mentioned above, end effector assembly  100  is attached at the distal end  14  of shaft  12  and includes a pair of opposing jaw members  110  and  120 . Movable handle  40  of handle assembly  30  is operably coupled to a drive assembly  130  which, together, mechanically cooperate to impart movement of the jaw members  110  and  120  from a first (e.g., open) position, wherein the jaw members  110  and  120  are disposed in spaced relation relative to one another, to a second (e.g., clamping or closed position), wherein the jaw members  110  and  120  cooperate to grasp tissue therebetween. 
         [0060]    It is envisioned that the forceps  10  may be designed such that it is fully or partially disposable depending upon a particular purpose or to achieve a particular result. For example, end effector assembly  100  may be selectively and releasably engageable with the distal end  16  of the shaft  12 , and/or the proximal end  14  of shaft  12  may be selectively and releasably engageable with the housing  20  and the handle assembly  30 . In either of these two instances, the forceps  10  would be considered “partially disposable” or “reposable”, e.g., a new or different end effector assembly  100  (or end effector assembly  100  and shaft  12 ) selectively replaces the old end effector assembly  100  as needed. As can be appreciated, the presently disclosed electrical connections would have to be altered to modify the instrument to a reposable forceps. 
         [0061]    Turning now to the more detailed features of the present disclosure as described with respect to  FIGS. 1A ,  1 B,  2 A, and  2 B, movable handle  40  includes a finger loop  43  which has an aperture  41  defined therethrough which enables a user to grasp and move the handle  40  relative to the fixed handle  50 . Finger loop  43  is typically ergonomically enhanced and may include one or more gripping elements (not shown) disposed along the inner peripheral edge of aperture  41  which are designed to facilitate gripping of the movable handle  40  during activation, e.g., a so-called “soft touch” or elastomeric material. Gripping elements may include one or more protuberances, scallops and/or ribs to enhance gripping. 
         [0062]    Referring to  FIGS. 2A and 2B , movable handle  40  is selectively movable about a pivot pin  45  from a first position relative to fixed handle  50  (as shown in  FIGS. 1A and 2A ) to a second position (as shown in  FIGS. 1B and 2B ) in closer proximity to the fixed handle  50  which, by operative association with drive assembly  130 , imparts movement of the jaw members  110  and  120  relative to one another. Referring to  FIGS. 3A and 3C , movable handle  40  includes a clevis  46  that forms a pair of upper flanges  46   a  and  46   b  each having an aperture  48  at an upper end thereof for receiving the pivot pin  45  therethrough and mounting the upper end of the handle  40  relative to the switch assembly  180 . In turn, pivot pin  45  mounts to switch housing  181  ( FIG. 4A-4C ) at pivot mount  182 . Pivot pin  45  is dimensioned to mount within a transverse opening  183  defined in pivot mount  182 . In an embodiment, a pivot pin  45   a  may be integrally formed with handle  40   a , as best seen in  FIG. 3B . At least one of upper flange  46   a  or  46   b  also includes a cam lobe  47  positioned at a proximal edge thereof, which, when assembled, abuts the switch assembly  180  such that pivotal movement of the handle  40  drives cam lobe  47  toward and, ultimately, in contact with, monopolar safety switch  430 , which, in turn, closes monopolar safety switch  430  and enables activation of monopolar energy upon actuation of a monopolar activation switch  465 ,  466 . 
         [0063]    Referring to  FIGS. 4A-4G ,  FIG. 8D , and  FIG. 10 , switch assembly  180  includes switch carrier  181 , a flex circuit assembly  200  mounted on the carrier  181 , and one or more keytop  60 ,  65 . Switch carrier  181  has a roughly saddle-shaped construction, having a top-proximal face  192 , a left face  193 , a right face  194 , a top face  195 , and a proximal face  191 . The switch carrier  181  may be formed from any suitable material, including without limitation, liquid crystal polymer (LCP), e.g., Vectra A430, manufactured by Ticona of Florence, Ky., USA. Faces  192 ,  193 ,  194  and  195  of switch carrier  181  are configured to support switch contacts  460 ,  465 ,  466 , and  430 , respectively, that are included with flex circuit  200 . An opening  196  is defined in proximal face  191  which may provide support to a proximal end of drive assembly  130 . At least one retention opening  186  is defined in each of left face  193  and right face  194  to receive retention clip  69  of keytop  65 . 
         [0064]    With reference to  FIGS. 7 ,  8 A- 8 D and  9 , flex circuit assembly  200  includes a bottom circuit layer  400   a , an adhesive layer  400   b , and a top circuit layer  400   c , each having a generally cruciform shape. Bottom circuit layer  400   a , adhesive layer  400   b , and/or top circuit layer  400   c  may be formed in part by die-cutting, laser-cutting, CNC cutting machines, and/or any suitable manner of fabrication. Bottom circuit layer  400   a  includes a substrate  401  and at least one circuit trace and/or contact pad disposed thereupon as best seen in  FIG. 8A . Substrate  401   a  may be formed from any suitable non-conductive material, such as without limitation polyimide, e.g., Kapton™ film manufactured by E, I. du Pont de Nemours and Company of Wilmington, Del., United States. Substrate  401  may have any suitable thickness, however, it is envisioned that substrate  401  has a thickness of about 0.005 inches. Circuit traces  416 ,  418  are arranged to electrically couple inner bipolar contact pad  460   a  and outer bipolar contact pad  460   b , respectively, to corresponding terminals  494  and  495  of edge connector  490 . Circuit trace  414  is arranged to couple left monopolar inner contact pad  465   a  and right monopolar inner contact pad  466   a  in common with terminal  493  of edge connector  490 . Circuit trace  415  is arranged to couple left monopolar outer contact pad  465   b  and right monopolar outer contact pad  466   b  in common with bottom safety switch contact pad  430   b . A generally circular opening  402 , having a diameter roughly corresponding to opening  196 , is defined in substrate  401 . The circuit traces as described herein may be formed from any suitable conductive material, including without limitation #5025 silver conductive ink manufactured by E, I. du Pont de Nemours and Company. A dielectric coating (not explicitly shown), such as without limitation, #5018 UV-curable coating manufactured by E. I. du Pont de Nemours and Company, may be selectively applied to the non-contact pad portions of the circuit traces. 
         [0065]    Adhesive layer  400   b  includes an adhesive substrate  403  that may be formed from any suitable adhesive and/or adhesive film-backed material, such as without limitation, double-sided adhesive tape, e.g., #7953 MP adhesive tape, manufactured by 3M of St. Paul, Minn., United States. Adhesive substrate  403  includes a plurality of openings  404 ,  405 ,  406 ,  407 , and  408  defined therein: a generally circular opening  408 , having a diameter roughly corresponding to opening  196 ; a pair of substantially square opening  405  and  406  that are each adapted to accommodate monopolar snap dome switches  465  and  466 , respectively; a substantially square opening  407  that is adapted to accommodate bipolar snap dome switch  460 , and a generally U-shaped opening  404  that is configured to provide a deformation region (not explicitly shown) which enables contact between bottom safety switch contact pad  430   b  and top safety switch contact pad  430   a  during actuation thereof. Opening  404  additionally may provide fluidic coupling between the deformation region (not explicitly shown) to the atmosphere via vent opening  431  of top circuit layer  400   c  to accommodate the reduced volume of the deformation region during actuation, e.g., when bottom safety switch contact pad  430   b  and top safety switch contact pad  430   a  are brought into electrical communication in response to force applied thereto by cam lobe  47  of handle  40 . 
         [0066]    Top circuit layer  400   c  includes circuit trace  410  that is arranged to couple edge contact  490  to resistor  420 , and circuit trace  412  that is arranged to couple edge contact  491  to resistor  422 . Resistors  420  and/or  422  may be formed from any suitable resistive material, such as without limitation, M3012-1 and/or M3013-1 RS carbon blend material manufactured by Minico/Asahi Chemical, of Congers, N.Y. United States. Resistors  420  and  422  form a voltage divider network to provide a reference voltage to top safety switch contact pad  430   a  via circuit trace  414 . In an embodiment, resistor  420  has a value of about 1,250Ω and resistor has a value of about 750Ω. Top circuit layer  400   c  has defined therein a pair of substantially square openings  432  and  433 , each adapted to accommodate a monopolar snap dome switch as described below, a substantially square opening  434  that is adapted to accommodate a bipolar snap dome switch as described below, a generally circular opening  435  having a diameter roughly corresponding to opening  196 , and a vent opening  431 . A cover  470  is fixed in a generally centered fashion over vent opening  431 . Vent cover  470  may be formed from liquid-resistant, gas-permeable material, such as without limitation, Gore™ Series VE4, manufactured by W. L. Gore &amp; Associates, Inc. of Newark, Del., United States. 
         [0067]    Bottom circuit layer  400   a , adhesive layer  400   b , and top circuit layer  400   c  are assembled as shown in  FIG. 9  to form flex circuit assembly  200 . Bottom circuit layer  400   a , is joined to top circuit layer  400   c  by adhesive layer  400   b . Snap dome switch  460  is joined to bottom circuit layer  400   a  in a sandwich fashion by the combination of bipolar dome retainer  470 , which captures snap dome switch  460  against bottom circuit layer  400   a , and bipolar dome adhesive layer  450 , which fixes bipolar dome retainer  470  and snap dome switch  460  in position over inner bipolar contact pad  460   a  and outer bipolar contact pad  460   b . By this configuration, deformation of snap dome switch  460  in response to actuation pressure establishes electrical continuity between inner bipolar contact pad  460   a  and outer bipolar contact pad  460   b.    
         [0068]    Monopolar snap dome switches  465 ,  466  are joined to bottom circuit layer  400   a  in a similar fashion to the respective positions thereof, e.g., snap dome switch  465  is joined to bottom circuit layer  400   a  by monopolar dome adhesive layer  455  and monopolar dome retainer  475 , and snap dome switch  466  is joined to bottom circuit layer  400   a  by monopolar dome adhesive layer  456  and monopolar dome retainer  476 . In an embodiment snap dome switches  460 ,  465 , and/or  466  may be a Snaptron F08400N snap dome switch having a 400 gram actuation pressure (a.k.a., “trip force”), however, the use of any suitable snap dome contact is contemplated within the scope of the present disclosure. 
         [0069]    Referring now to  FIGS. 10 and 11 , flex circuit assembly  200  is disposed upon switch carrier  181  such that bipolar snap dome switch  460  is disposed on top-proximal face  192 , monopolar snap dome switch  465  is disposed on left face  193 , monopolar snap dome switch  466  is disposed on right face  194 , and safety switch  430  is disposed on top face  195 . As best seen in  FIGS. 10 and 11 , the cruciform appendages of flex circuit assembly  200  are flexed to conform generally to the shape of carrier  181 . Flex circuit assembly  200  may be fixed to carrier  181  by any suitable manner of attachment, including without limitation, adhesive, and/or laser welding. A monopolar keytop  65  is operably coupled to carrier  181  by engagement of retention clips  69  with retention opening  186 . Nub  68  is substantially aligned with a center of the corresponding snap dome switch  465 ,  466  and is adapted to transfer actuation force from keytop  65  to the underlying snap dome switch  465 ,  466 . 
         [0070]    Bipolar keytop  60  is disposed within an opening  64  defined within the housing  20  ( FIGS. 1A and 2A ). Opening  64  is dimensioned to enable the top portion  62  of bipolar keytop  60  to move freely therein, e.g., inwardly and outwardly with respect to housing  20  and underlying bipolar snap dome switch  460 . Bipolar keytop  60  is retained within opening  64  by shoulder  61  of bipolar keytop  60 . Nub  63  is substantially aligned with a center of the bipolar snap dome switch  460  and is adapted to transfer actuation force from bipolar keytop  60  to the underlying bipolar snap dome switch  460 . 
         [0071]    Switch assembly  180  is disposed within housing  20  and configured to electromechanically cooperate with drive mechanism  130 , handle  40 , and bipolar keytop  60  to allow a user to selectively activate the jaw members  110  and  120  in a monopolar and/or bipolar mode. Monopolar safety switch  430  is configured such that the monopolar activation switches  65  are disabled when the handle  40  and/or jaw members  110  and  120  are in an open position, and/or when jaw members  110  and  120  have no tissue held therebetween ( FIGS. 2A and 2B ). When handle  40  is in an open position, e.g., distal position, cam  47  is effectively disengaged from monopolar safety switch  430  causing bottom safety switch contact pad  430   b  and top safety switch contact pad  430   a  to remain separated, causing an open circuit thereby inhibiting operation of either monopolar switch  465 ,  466 . When handle  40  is in a closed, e.g., proximal, position, cam  47  engages bottom safety switch  430  by deforming a region of flex circuit substrate region, causing contact pad  430   b  to electrically couple with top safety switch contact pad, establishing a closed circuit path which enables monopolar switch  465 ,  466 , upon actuation thereof, to provide a monopolar activation signal to, e.g., generator  500  via cable  305 . Actuation of bipolar switch  460  establishes continuity between contacts  494  and  495  and/or circuit traces  416  and  418 , thereby providing a bipolar activation signal to, e.g., generator  500  via cable  305 . 
         [0072]    A sensor (not shown) may be employed to determine if tissue is held between jaw members  110  and  120 . In addition, other sensor mechanisms may be employed which determine pre-surgical, concurrent surgical (i.e., during surgery) and/or post surgical conditions. The sensor mechanisms may also be utilized with a closed-loop feedback system coupled to the electrosurgical generator  500  to regulate the electrosurgical energy based upon one or more pre-surgical, concurrent surgical or post surgical conditions. Various sensor mechanisms and feedback systems are described in commonly-owned U.S. Pat. No. 7,137,980 entitled “METHOD AND SYSTEM FOR CONTROLLING OUTPUT OF RF MEDICAL GENERATOR”. 
         [0073]    As seen in FIGS.  1 A and  3 A-C, the lower end of the movable handle  40  includes a flange  42  which is typically integrally associated with or operatively connected to movable handle  40 . Flange  42  is typically T-shaped and includes a pin-like element  44  which projects laterally or transversally from a distal end thereof and is configured to engage a corresponding latch  55  disposed within fixed handle  50 . More particularly, the pin  44  is configured to ride within a pre-defined channel (not explicitly shown) disposed within the latch  55  to lock the movable handle  40  relative to the fixed handle  50  upon reciprocation thereof. 
         [0074]    The jaw members  110  and  120  are electrically isolated from one another such that electrosurgical energy can be effectively transferred through the tissue to form seal. Cable leads (not explicitly shown) are held loosely but securely along the cable path to permit rotation of the jaw members  110  and  120  about longitudinal axis “A” (See  FIG. 1A ). More particularly, cable leads (not explicitly shown) are fed through respective halves  80   a  and  80   b  of the rotating assembly  80  in such a manner to allow rotation of the shaft  12  (via rotation of the rotating assembly  80 ) in the clockwise or counter-clockwise direction without unduly tangling or twisting said cable leads. The presently disclosed cable lead feed path is envisioned to allow rotation of the rotation assembly approximately 180 degrees in either direction. 
         [0075]    From the foregoing and with reference to the various figure drawings, 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. For example, it may be preferable to add other features to the forceps  10 , e.g., an articulating assembly to axially displace the end effector assembly  100  relative to the elongated shaft  12 . 
         [0076]    It is also contemplated that the forceps  10  (and/or the electrosurgical generator used in connection with the forceps  10 ) may include a sensor or feedback mechanism (not shown) which automatically selects the appropriate amount of electrosurgical energy to effectively seal the particularly-sized tissue grasped between the jaw members  110  and  120 . The sensor or feedback mechanism may also measure the impedance across the tissue during sealing and provide an indicator (visual and/or audible) that an effective seal has been created between the jaw members  110  and  120 . Examples of such sensor systems are described in commonly-owned U.S. Pat. No. 7,137,980 entitled “METHOD AND SYSTEM FOR CONTROLLING OUTPUT OF RE MEDICAL GENERATOR”. 
         [0077]    Moreover, it is envisioned that the forceps  10  may be used to cut tissue without sealing. Alternatively, a knife assembly (not explicitly shown) may be coupled to the same or alternate electrosurgical energy source to facilitate cutting of the tissue. 
         [0078]    It is envisioned that the outer surface of the end effector assembly  100  may include a nickel-based material, coating, stamping, metal injection molding which is designed to reduce adhesion between the jaw members  110  and  120  with the surrounding tissue during activation and sealing. Moreover, it is also contemplated that the conductive surfaces  112  and  122  of the jaw members  110  and  120  may be manufactured from one (or a combination of one or more) of the following materials: nickel-chrome, chromium nitride, inconel 600, tin-nickel, and MedCoat 2000 manufactured by The Electrolizing Corporation of Ohio, Cleveland, Ohio, United States. The tissue conductive surfaces  112  and  122  may also be coated with one or more of the above materials to achieve the same result, i.e., a “non-stick surface”. As can be appreciated, reducing the amount that the tissue “sticks” during sealing improves the overall efficacy of the instrument. 
         [0079]    One particular class of materials disclosed herein has demonstrated superior non-stick properties and, in some instances, superior seal quality. For example, nitride coatings which include, but not are not limited to: TiN, ZrN, TiAlN, and CrN are preferred materials used for non-stick purposes. CrN has been found to be particularly useful for non-stick purposes due to its overall surface properties and optimal performance. Other classes of materials have also been found to reducing overall sticking. For example, high nickel/chrome alloys with a Ni/Cr ratio of approximately 5:1 have been found to significantly reduce sticking in bipolar instrumentation. One particularly useful non-stick material in this class is Inconel 600. Bipolar instrumentation having sealing surfaces  112  and  122  made from or coated with Ni200, Ni201 (˜100% Ni) also showed improved non-stick performance over typical bipolar stainless steel electrodes. 
         [0080]    As can be appreciated, locating switches  460 ,  465 , and  466  on the forceps  10  has many advantages. For example, the disclosed configuration of switches  60 ,  65  and  66  reduces the amount of electrical cable in the operating room and eliminates the possibility of activating the wrong instrument during a surgical procedure due to “line-of-sight” activation. Switches  60 ,  65 , and  66  may be configured such that operation thereof is mechanically or electro-mechanically inhibited during trigger activation, which may eliminate unintentionally activating the device during the cutting process. Switches  60 ,  65 , and  66  may be disposed on another part of the forceps  10 , e.g., the fixed handle  50 , rotating assembly  80 , housing  20 , etc. 
         [0081]    The described embodiments of the present disclosure are intended to be illustrative rather than restrictive, and are not intended to represent every embodiment of the present disclosure. Further variations of the above-disclosed embodiments and other features and functions, or alternatives thereof, may be made or desirably combined into many other different systems or applications without departing from the spirit or scope of the disclosure as set forth in the following claims both literally and in equivalents recognized in law.

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