Local optimization of electrode current densities

An end effector assembly for use with a bipolar forceps includes a pair of opposing first and second jaw members at least one of which being movable relative to the other to grasp tissue therebetween. Each jaw member includes a pair of spaced apart, electrically conductive tissue sealing surfaces. Each tissue sealing surface is adapted to connect to a source of electrosurgical energy to conduct electrosurgical energy through tissue held therebetween to effect a tissue seal. The forceps also includes an insulator disposed between each pair of electrically conductive sealing surfaces and an electrically conductive cutting element disposed within each insulator and defining a geometrical configuration including a plurality of peaks having a period that is a multiple of an operating frequency of the electrosurgical energy. The cutting elements are adapted to connect to the source of electrosurgical energy to conduct electrosurgical energy through tissue held therebetween to effect a tissue cut.

BACKGROUND

1. Technical Field

The following disclosure relates to an apparatus, system, and method for performing an electrosurgical procedure and, more particularly, to local optimization of electrode current densities utilizing electrode geometries.

2. Description of Related Art

It is well known in the art that electrosurgical generators are employed by surgeons in conjunction with electrosurgical instruments to perform a variety of electrosurgical surgical procedures (e.g., tonsillectomy, adenoidectomy, etc.). An electrosurgical generator generates and modulates electrosurgical energy which, in turn, is applied to the tissue by an electrosurgical instrument. Electrosurgical instruments may be either monopolar or bipolar and may be configured for open or endoscopic procedures.

Electrosurgical instruments may be implemented to ablate, seal, cauterize, coagulate, and/or desiccate tissue and, if needed, cut and/or section tissue. Typically, cutting and/or sectioning tissue is performed with a knife blade movable within a longitudinal slot located on or within one or more seal plates associated with one or more jaw members configured to receive a knife blade, or portion thereof. The longitudinal slot is normally located on or within the seal plate within a treatment zone (e.g., seal and/or coagulation zone) associated therewith. Consequently, the knife blade cuts and/or sections through the seal and/or coagulation zone during longitudinal translation of the knife blade through the longitudinal slot. In some instances, it is not desirable to cut through the zone of sealed or coagulated tissue, but rather to the left or right of the zone of sealed or coagulated tissue such as, for example, during a tonsillectomy and/or adenoidectomy procedure.

SUMMARY

According to an embodiment of the present disclosure, an end effector assembly for use with a bipolar forceps includes a pair of opposing first and second jaw members at least one of which being movable relative to the other to grasp tissue therebetween. Each jaw member includes a pair of spaced apart, electrically conductive tissue sealing surfaces. Each tissue sealing surface is adapted to connect to a source of electrosurgical energy to conduct electrosurgical energy through tissue held therebetween to effect a tissue seal. The end effector assembly also includes an insulator disposed between each pair of electrically conductive sealing surfaces and an electrically conductive cutting element disposed within each insulator and defining a geometrical configuration including a plurality of peaks having a period that is a multiple of an operating frequency of the electrosurgical energy. The cutting elements are adapted to connect to the source of electrosurgical energy to conduct electrosurgical energy through tissue held therebetween to effect a tissue cut.

According to another embodiment of the present disclosure, an end effector assembly for use with a bipolar forceps includes a pair of opposing first and second jaw members at least one of which being movable relative to the other 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. Each jaw member includes a pair of spaced apart, electrically conductive tissue sealing surfaces extending along a length thereof. Each tissue sealing surface is adapted to connect to a source of electrosurgical energy to conduct electrosurgical energy through tissue held therebetween to effect a tissue seal. The end effector assembly also includes an insulator disposed between each pair of electrically conductive sealing surfaces and an electrically conductive cutting element disposed within the insulator of the first jaw member and in general vertical registration with an electrically conductive cutting element disposed within the insulator of the second jaw member. Each of the electrically conductive cutting elements includes a plurality of peaks offset from a plurality of peaks of the other cutting element. The number of peaks of at least one of the cutting elements is a function of a wavelength of an operating frequency of the electrosurgical energy. The cutting elements are adapted to connect to the source of electrosurgical energy to conduct electrosurgical energy through tissue held therebetween to effect a tissue cut. The cutting elements are inactive during tissue sealing and the pair of spaced apart electrically conductive sealing surfaces on the first jaw member are energized to a different potential from the corresponding pair of spaced apart electrically conductive sealing surfaces on the second jaw member such that electrosurgical energy can be transferred through the tissue to effect a tissue seal.

According to another embodiment of the present disclosure, a method of manufacturing an electrically conductive cutting element adapted to be coupled to an end effector assembly for effecting a tissue cut includes the steps of providing an electrically conductive electrode having a predetermined length and calculating a number of peaks along the predetermined length and a period based on a repetition of the peaks. The number of peaks is a function of an operating frequency of an energy source adapted to supply electrosurgical energy to the electrically conductive cutting element.

DETAILED DESCRIPTION

For the purposes herein, vessel/tissue cutting or vessel/tissue division is believed to occur when heating of the vessel/tissue leads to expansion of intracellular and/or extra-cellular fluid, which may be accompanied by cellular vaporization, desiccation, fragmentation, collapse and/or shrinkage along a so-called “cut zone” in the vessel/tissue. By focusing the electrosurgical energy and heating in the cut zone, the cellular reactions are localized creating a fissure. Localization is achieved by regulating the vessel/tissue condition and energy delivery, which may be controlled by utilizing one or more of the various geometrical electrode configurations described herein. The cut process may also be controlled by utilizing a generator and feedback algorithm (and one or more of the hereindescribed geometrical configurations of the electrode assemblies) that increases the localization and maximizes the so-called “cutting effect”.

In general, the below-described factors contribute and/or enhance vessel/tissue division using electrosurgical energy. Each of the factors described below may be employed individually or in any combination to achieve a desired cutting effect. For the purposes herein, the term “cut effect” or “cutting effect” refers to the actual division of tissue by one or more of the electrical or electromechanical methods or mechanisms described below. The term “cutting zone” or “cut zone” refers to the region of vessel/tissue where cutting will take place. The term “cutting process” refers to steps that are implemented before, during, and/or after vessel/tissue division that tend to influence the vessel/tissue as part of achieving the cut effect.

For the purposes herein, the terms “tissue” and “vessel” may be used interchangeably since it is believed that the present disclosure may be employed to seal and cut tissue or seal and cut vessels utilizing the same principles described in the present disclosure.

By way of example and without limitation, factors that either alone or in combination play an important role in dividing tissue include: (1) localizing or focusing electrosurgical energy in the cut zone during the cutting process while minimizing energy effects to surrounding tissues; (2) focusing the current density in the cut zone during the cutting process; (3) creating an area of increased temperature in the cut zone during the cutting process (e.g., heating that occurs within the tissue or heating the tissue directly with a heat source); and (4) pulsing the energy delivery to influence the tissue in or around the cut zone.

Electrode assemblies described herein utilize various geometrical configurations of electrodes, cutting elements, insulators, partially conductive materials, and semiconductors to produce or enhance the cutting effect. In addition, by controlling or regulating the electrosurgical energy from the generator in any of the ways described above, tissue cutting may be initiated, enhanced, or facilitated within the tissue cutting zone.

For example, the geometrical configuration of the electrodes may be configured to produce a so-called “cut effect” that is directly related to the current density applied to a point in the tissue. The geometry of the electrodes may be configured such that the surface area ratios between the electrical poles focus electrical energy at the tissue. Moreover, optimization of the “cut effect” may be achieved by configuring the geometry of bipolar-type electrodes to include a specific number of peaks (seeFIGS. 4A,4B, and4C) as a function of the operating frequency (e.g., the fundamental frequency) of the energy source used to produce the “cut effect”. More specifically, bipolar-type electrodes having peaks repeating at a particular period T (seeFIG. 4A) and that period T is a multiple of the operating frequency of the energy being applied to tissue to produce the “cut effect”, the current density between the electrodes will be maximized, thereby optimizing the “cut effect”. The present disclosure provides for various electrode geometries configured in accordance with the operating frequency of the output energy and a method for calculating such geometric configurations as a function of the operating frequency of energy output for purposes of optimizing the “cut effect”.

Referring now toFIGS. 1A and 1B,FIG. 1Adepicts a bipolar forceps10for use in connection with endoscopic surgical procedures andFIG. 1Bdepicts an open forceps100for use in connection with traditional open surgical procedures. For the purposes herein, either an endoscopic instrument or an open instrument may be utilized with the electrode assembly described herein. Different electrical and mechanical connections and considerations apply to each particular type of instrument, however, the novel aspects with respect to the electrode assembly and its operating characteristics remain generally consistent with respect to both the open or endoscopic designs.

FIG. 1Ashows a bipolar forceps10for use with various endoscopic surgical procedures and generally includes a housing20, a handle assembly30, a rotating assembly80, a switch assembly70, and an electrode assembly105having opposing jaw members110and120that mutually cooperate to grasp, seal, and divide tubular vessels and vascular tissue. More particularly, forceps10includes a shaft12which has a distal end16dimensioned to mechanically engage the electrode assembly105and a proximal end14that mechanically engages the housing20. The shaft12includes one or more mechanically engaging components that are designed to securely receive and engage the electrode assembly105such that the jaw members110and120are pivotable about a pivot pin19relative to one another to engage and grasp tissue therebetween.

The proximal end14of shaft12mechanically engages the rotating assembly80(not shown) to facilitate rotation of the electrode assembly105. In the drawings and in the descriptions that follow, the term “proximal”, as is traditional, will refer to the end of the forceps10that is closer to the user, while the term “distal” will refer to the end that is farther from the user. Details relating to the mechanically cooperating components of the shaft12and the rotating assembly80are described in commonly-owned U.S. Pat. No. 7,156,846.

Handle assembly30includes a fixed handle50and a movable handle40. Fixed handle50is integrally associated with housing20and, handle40is movable relative to fixed handle50to impart movement of the jaw members110and120from an open position wherein the jaw members110and120are disposed in spaced relation relative to one another, to a clamping or closed position wherein the jaw members110and120cooperate to grasp tissue therebetween. Switch assembly70is configured to selectively provide electrical energy to the electrode assembly105.

Referring now toFIG. 1B, an open forceps100includes a pair of elongated shaft portions112aand112beach having a proximal end114aand114b, respectively, and a distal end116aand116b, respectively. The forceps100includes jaw members120and110which attach to distal ends116aand116bof shafts112aand112b, respectively. The jaw members110and120are connected about pivot pin119such that jaw members110and120pivot relative to one another from the first to second positions for treating tissue. The electrode assembly105is connected to opposing jaw members110and120and may include electrical connections through or around the pivot pin119.

Each shaft112aand112bincludes a handle117aand117bdisposed at the proximal end114aand114bthereof which each define a finger hole118aand118b, respectively, therethrough for receiving a finger of the user. Finger holes118aand118bfacilitate movement of the shafts112aand112brelative to one another that, in turn, pivot the jaw members110and120from the open position wherein the jaw members110and120are disposed in spaced relation relative to one another to the clamping or closed position wherein the jaw members110and120cooperate to grasp tissue therebetween. A ratchet130is included for selectively locking the jaw members110and120relative to one another at various positions during pivoting.

As best seen inFIG. 1B, forceps100also includes an electrical interface or plug200that connects the forceps100to a source of electrosurgical energy, e.g., electrosurgical generator500(FIG. 1A). An electrical cable210extends from the plug200and securely connects the cable210to the forceps100. Cable210is internally divided within the shaft112bto transmit electrosurgical energy through various electrical feed paths to the electrode assembly105.

One of the shafts, e.g.,112b, includes a proximal shaft connector/flange121that is configured to connect the forceps100to a source of electrosurgical energy (e.g., electrosurgical generator500). More particularly, flange121mechanically secures electrosurgical cable210to the forceps100such that the user may selectively apply electrosurgical energy as needed.

As best shown in the schematic illustration ofFIG. 2, the jaw members110and120of both the endoscopic version ofFIG. 1Aand the open version ofFIG. 1Bare generally symmetrical and include similar component features that cooperate to permit facile rotation about pivot19,119to effect the grasping and sealing of tissue. Each jaw member110and120includes an electrically conductive tissue contacting surface112and122, respectively, that cooperate to engage the tissue during sealing and cutting. At least one of the jaw members, e.g., jaw member120, includes an electrically energizable cutting element127disposed therein, explained in detail below. Together and as shown in the various figure drawings described hereafter, the electrode assembly105includes the combination of the sealing electrodes112and122and the cutting element(s)127.

The various electrical connections of the electrode assembly105are configured to provide electrical continuity to the tissue contacting surfaces110and120and the cutting element(s)127through the electrode assembly105. For example, cable lead210may be configured to include three different leads, namely, leads207,208and209that carry different electrical potentials. The cable leads207,208and209are fed through shaft112band connect to various electrical connectors (not shown) disposed within the proximal end of the jaw member110which ultimately connect to the electrically conductive sealing surfaces112and122and cuffing element(s)127.

The various electrical connections from lead210are dielectrically insulated from one another to allow selective and independent activation of either the tissue contacting surfaces112and122or the cutting element127. Alternatively, the electrode assembly105may include a single connector that includes an internal switch (not shown) to allow selective and independent activation of the tissue contacting surfaces112,122and the cutting element127.

As best seen inFIG. 3, an embodiment of the electrode assembly105is shown that is configured to effectively seal and cut tissue disposed between the sealing surfaces112and122and the cutting elements127of the opposing jaw members110and120, respectively. More particularly and with respect toFIGS. 2 and 3, jaw members110and120include conductive tissue contacting surfaces112and122, respectively, disposed along substantially the entire longitudinal length thereof (e.g., extending substantially from the proximal to distal end of the respective jaw member110and120). In embodiments, tissue contacting surfaces112and122may be attached to the jaw members110,120by stamping, by overmolding, by casting, by overmolding a casting, by coating a casting, by overmolding a stamped electrically conductive sealing plate, and/or by overmolding a metal injection molded seal plate.

With respect toFIG. 3, jaw members110and120both include an insulator or insulative material113and123, respectively, disposed between each pair of electrically conductive sealing surfaces on each jaw member110and120, i.e., between pairs112aand112band between pairs122aand122b. Each insulator113and123is generally centered between its respective tissue contacting surface112a,112band122a,122balong substantially the entire length of the respective jaw member110and120such that the two insulators113and123generally oppose one another.

At least one jaw member110and/or120includes an electrically conductive cutting element127disposed substantially within or disposed on the insulator113,123. As described in detail below, the cutting element127(in many of the embodiments described hereinafter) plays a dual role during the sealing and cutting processes, namely: 1) to provide the necessary gap distance between conductive surfaces112a,112band122a,122bduring the sealing process; and 2) to electrically energize the tissue along the previously formed tissue seal to cut the tissue along the seal. With respect toFIG. 3, the cutting elements127a,127bare electrically conductive, however, one or both of the cutting elements127a,127bmay be made from an insulative material with a conductive coating disposed thereon or one (or both) of the cutting elements127a,127bmay be non-conductive. In some embodiments, the distance between the cutting element(s)127aand the opposing cutting element127b(or the opposing return electrode in some cases) is within the range of about 0.008 inches to about 0.015 inches to optimize the cutting effect.

The general characteristics of the jaw members110and120and the electrode assembly105will initially be described with respect toFIG. 3while the changes to the other embodiments disclosed herein will become apparent during the description of each individual embodiment. Moreover,FIG. 3shows an electrical configuration and polarity during the cutting phase only. During the so called “sealing phase”, the jaw members110and120are closed about tissue and the cutting elements127aand127bform the requisite gap between the opposing sealing surfaces112a,122aand112b,122b. During activation of the sealing phase, the cutting elements127aand127bare not necessarily energized such that the majority of the current is concentrated between opposing sealing surfaces,112aand122aand112band122bto effectively seal the tissue. In embodiments, stop members (not shown) may be employed to regulate the gap distance between the sealing surfaces in lieu of the cutting elements127aand127b. The stop members may be disposed on the sealing surfaces112a,122aand112b,122b, adjacent the sealing surfaces112a,122aand112b,122bor on the insulator(s)113,123.

In some embodiments, the cutting elements127aand127bare configured to extend from their respective insulators113and123, respectively, and extend beyond the tissue contacting surfaces112a,112band122a,122bsuch that the cutting elements127aand127bact as stop members (i.e., create a gap distance “G” (SeeFIG. 3) between opposing conductive sealing surfaces112a,122aand112b,122b) that as mentioned above, promotes accurate, consistent, and effective tissue sealing. The cutting elements127aand127balso prevent the opposing tissue contacting surfaces112a,122aand112b,122bfrom touching to eliminate the chances of the forceps10,100shorting during the sealing process.

With respect toFIG. 3, the conductive cutting elements127aand127bare oriented in opposing, vertical registration within respective insulators113and123of jaw members110and120. In some embodiments, the cutting elements127aand127bare substantially dull so as to not inhibit the sealing process (i.e., premature cutting) during the sealing phase of the electrosurgical activation. In other words, the surgeon is free to manipulate, grasp and clamp the tissue for sealing purposes without the cutting elements127aand127bmechanically cutting into the tissue. Moreover, in this instance, tissue cutting can only be achieved through either: 1) a combination of mechanically clamping the tissue between the cutting elements127aand127band applying electrosurgical energy from the cutting elements127aand127b, through the tissue and to the return electrodes, i.e., the electrically conductive tissue contacting surfaces112band122bas shown inFIG. 3; or 2) applying electrosurgical energy from the cutting elements127aand127bthrough the tissue and to the return tissue contacting surfaces112band122b.

In some embodiments, the geometrical configuration of the cutting elements127aand127bmay, at least in part, determine the overall effectiveness of the tissue cut. Certain geometries of the cutting elements127aand127bmay create higher areas of current density than other geometries. Moreover, the spacing of the return electrodes112band122bto these current density affects the electrical fields through the tissue. Therefore, by configuring the cutting elements127aand127band the respective insulators113and123within close proximity to one another, the current density remains high which is ideal for cutting and the instrument will not short due to accidental contact between conductive surfaces. The relative size of the cutting elements127aand127band/or the size of the insulator113and123may be selectively altered depending upon a particular or desired purpose to produce a particular surgical effect.

Turning now to the embodiments of the electrode assembly105as disclosed herein,FIG. 3as mentioned above includes first and second jaw members110and120having an electrode assembly105disposed thereon. More particularly, the electrode assembly105includes first electrically conductive sealing surfaces112aand112beach disposed in opposing registration with second electrically conductive sealing surfaces122aand122bon jaw members110and120, respectively. Insulator113electrically isolates sealing surfaces112aand112bfrom one another allowing selective independent activation of the sealing surfaces112aand112b. Insulator123separates sealing surfaces122aand122bfrom one another in a similar manner thereby allowing selective activation of sealing surfaces122aand122b.

Each insulator113and123is set back a predetermined distance between the sealing surfaces112a,112band122a,122bto define a recess149a,149band159a,159b, respectively, that as mentioned above, affects the overall current densities between the electrically activated surfaces during both the sealing and cutting phases. Cutting element127ais disposed within and/or deposited on insulator113and extends inwardly therefrom to extend beyond the sealing surfaces112a,112bby a predetermined distance.

During sealing, the opposing sealing surfaces112a,122aand112b,122bare activated to seal the tissue disposed therebetween to create two tissue seals on either side of the insulators113and123. During the cutting phase, the cutting elements127aand127bare energized with a first electrical potential “+” and the right opposing sealing surfaces112band122bare energized with a second electrical potential “−”. This creates a concentrated electrical path between the potentials “+” and “−” through the tissue to cut the tissue between the previously formed tissue seals. Once the tissue is cut, the jaw members110and120are opened to release the two tissue halves.

With reference toFIGS. 4A,4B, and4C, to maximize the current density between cutting elements127aand127band, thereby optimize the “cutting effect”, the geometry of the cutting elements127aand127bmay be configured to include a plurality of peaks131separated by valleys133interposed therebetween to define waveforms having a period T (illustrated, for example, inFIG. 4A). In the illustrated embodiments ofFIGS. 4A,413, and4C, the waveforms defined by cutting elements127a,127bare off-set from one another such that the peaks131of cutting element127acomplement the valleys133of cutting element127band vice-versa. The various peak131and valley133configurations depicted byFIGS. 4A,4B, and4C are intended to illustrate the concept that the period T of the waveforms defined by cutting element127aand/or127bis configured as a function of the operating frequency of the output energy from the energy source (e.g., generator500) to maximize the current density between cutting elements127aand127b, thereby optimizing the “cut effect”. The geometric configurations depicted byFIGS. 4A,4B, and4C are illustrative only in that any suitable geometric shape of peaks131and/or valleys133may be used to maximize current density between cutting elements127aand127bin the manner described hereinabove and hereinafter.

The relationship between the operating frequency of the energy source and the geometric configuration of the cutting element(s)127aand/or127bis illustrated by the following set of equations:
λ=f/v;(1)

wherein λ is the wavelength of the waveform defined by cutting element(s)127aand/or127b; f is the operating frequency (or fundamental frequency) of the output energy of the energy source (e.g., generator500); and v is the velocity of the output energy.

Equation (1), in turn, is utilized to yield equation
d=λ/x;(2)

wherein d is a distance between any two points along the waveform defined by cutting element(s)127aand/or127bthat may be used to define the period T of the waveform; and x is the number of peaks131along the waveform.

Equations (1) and (2), in turn, are utilized to yield equation
d*x=f/v;(3)

Equations (1) and (3), in turn, are utilized to yield equation
d=λ/x;(4)

wherein the number x of peaks131can be varied as necessary to yield the appropriate number of peaks131for a given length L of cutting element(s)127aand/or127b.

Utilizing equation (4), the current density between cutting elements127aand127bmay be maximized by configuring each cutting element127aand/or127bto include the appropriate number x of peaks131for a given length L of cutting element127aand/or127bas a function of the wavelength λ of the operating frequency of the energy source (e.g., generator500) used to produce the “cut effect”. In this manner, the “cut effect” produced by application of energy to tissue via cutting element(s)127aand/or127bis optimized.

When manufacturing cutting element(s)127aand/or127b, the “cut effect” may be optimized by using equation (4) to calculate the appropriate number of peaks x for a given length L of cutting element(s)127aand/or127bas a function of the operating frequency f of the energy source associated with forceps10,100. Conversely, the “cut effect” may be optimized by using equation (4) to calculate the appropriate operating frequency f as a function of the geometric configuration of cutting element(s)127aand/or127b(e.g., the number of peaks x for a given length L) and adjusting (e.g., discretely) the operating frequency of the energy source (e.g., generator500) accordingly. That is, for example, a suitable control mechanism (not shown) may be disposed on the generator500to allow a user to selectively adjust the operating frequency of the generator500in accordance with the geometric configuration of a cutting element and/or electrode of an instrument connected to the generator500for purposes of sealing and/or cutting tissue utilizing the energy output of the generator500.

In some embodiments, the current density and/or current concentration around the cutting elements127aand127bis based upon the particular geometrical configuration of the cutting elements127aand127band the cutting elements'127aand127bproximity to the return electrodes, i.e., tissue contacting surfaces112band122b.

In addition, the cutting element(s)127a(and/or127b) may be independently activated by the surgeon or automatically activated by the generator once sealing is complete. A safety algorithm may be employed to assure that an accurate and complete tissue seal is formed before cutting. An audible or visual indicator (not shown) may be employed to assure the surgeon that an accurate seal has been formed and the surgeon may be required to activate a trigger (or deactivate a safety) before cutting. For example, a smart sensor or feedback algorithm (not shown) may be employed to determine seal quality prior to cutting. The smart sensor or feedback loop may also be configured to automatically switch electrosurgical energy to the cutting element(s)127a(and/or127b) once the smart sensor determines that the tissue is properly sealed. In embodiments, the electrical configuration of the electrically conductive sealing surfaces112a,112band122a,122bmay be automatically or manually altered during the sealing and cutting processes to effect accurate and consistent tissue sealing and cutting.

The various geometrical configurations and electrical arrangements of the aforementioned electrode assemblies allow the surgeon to initially activate the two opposing electrically conductive tissue contacting surfaces and seal the tissue and, subsequently, selectively and independently activate the cutting element and one or more tissue contacting surfaces to cut the tissue utilizing the various above-described and shown electrode assembly configurations. Hence, the tissue is initially sealed and thereafter cut without re-grasping the tissue.

However, the cutting element and one or more tissue contacting surfaces may also be activated to simply cut tissue/vessels without initially sealing. For example, the jaw members may be positioned about tissue and the cutting element may be selectively activated to separate or simply coagulate tissue. This type of alternative embodiment may be particularly useful during certain endoscopic procedures wherein an electrosurgical pencil is typically introduced to coagulate and/or dissect tissue during the operating procedure.

A switch (e.g., switch assembly70shown inFIG. 1A) may be employed to allow the surgeon to selectively activate one or more tissue contacting surfaces or the cutting element independently of one another. This allows the surgeon to initially seal tissue and then activate the cutting element by simply actuating the switch.