Mechanism for dividing tissue in a hemostat-style instrument

<u>BACKGROUND</u>

0001The present disclosure relates to forceps used for open surgical procedures. More particularly, the present disclosure relates to an open forceps which applies a combination of mechanical clamping pressure and electrosurgical energy to seal tissue and a cutting device which is selectively activatable to sever tissue.

0002For example, <patcit id="pcit0001" dnum="US20030199869A"><text>US-A-2003/0199869</text></patcit> discloses a vessel sealing instrument.

0003The invention is set out in the claims.

Technical Filed

0004A forceps is a plier-like instrument which relies on mechanical action between its jaws to grasp, clamp and constrict vessels or tissue therebetween. So-called "open forceps" are commonly used in open surgical procedures whereas "endoscopic forceps" or "laparoscopic forceps" are, as the name implies, used for less invasive endoscopic surgical procedures. Electrosurgical forceps (open or endoscopic) utilize both mechanical clamping action and electrical energy to effect hemostasis by heating tissue and blood vessels to coagulate and/or cauterize tissue.

0005Certain surgical procedures require more than simply cauterizing tissue and rely on the unique combination of clamping pressure, precisely controlling the application of electrosurgical energy and the gap distance (i.e., distance between opposing jaw members or opposing conducting surfaces when closed about tissue) to "seal" tissue, vessels and certain vascular bundles.

0006Vessel sealing or tissue sealing is a recently-developed technology which utilizes a unique combination of radiofrequency energy, pressure and gap control to effectively seal or fuse tissue between two opposing jaw members or sealing plates. Vessel or tissue sealing is more than "cauterization" which is defined as the use of heat to destroy tissue (also called "diathermy" or "electrodiathermy") and vessel sealing is more than "coagulation" which is defined as a process of desiccating tissue wherein the tissue cells are ruptured and dried. "Vessel sealing" is defined as the process of liquefying the collagen, elastin and ground substances in the tissue so that it reforms into a fused mass with significantly-reduced demarcation between the opposing tissue structures.

0007In order to effectively "seal" tissue or vessels, two predominant mechanical parameters must be accurately controlled: 1) the pressure applied to the vessel or tissue; and 2) the gap distance between the conductive tissue contacting surfaces (electrodes). As can be appreciated, both of these parameters are affected by the thickness of the tissue being sealed. Accurate application of pressure is important for several reasons: 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. It has been determined that a good seal for certain tissues is optimum between 25.4 µm and 152.4 µm (0.001 inches and 0.006 inches).

0008With respect to smaller vessels or tissue, the pressure applied becomes less relevant and the gap distance between the electrically conductive surfaces becomes more significant for effective sealing. In other words, the chances of the two electrically conductive surfaces touching during activation increases as the tissue thickness and the vessels become smaller.

0009Commonly owned, <patcit id="pcit0002" dnum="US6511480B"><text>U.S. Patent No. 6,511,480</text></patcit>, <patcit id="pcit0003" dnum="WO02080797A"><text>WO 02 080 797</text></patcit> (<patcit id="pcit0004" dnum="US0111420W"><text>PCT Patent Application Nos. PCT/US01/11420</text></patcit>) and <patcit id="pcit0005" dnum="WO02080793A"><text>WO 02080793</text></patcit> (<patcit id="pcit0006" dnum="US0111218W"><text>PCT/US01/11218</text></patcit>), <patcit id="pcit0007" dnum="US20030014053A1"><text>US 2003-0014053 A1</text></patcit>, <patcit id="pcit0008" dnum="US20030199869A1"><text>US 2003-0199869 A1</text></patcit> and <patcit id="pcit0009" dnum="US20030109875A1"><text>US 2003-0109875 A1</text></patcit> (<patcit id="pcit0010" dnum="US116824A" dnum-type="L"><text>U.S. Patent Applications Serial Nos. 10/116,824</text></patcit>, <patcit id="pcit0011" dnum="US10284562B" dnum-type="L"><text>10/284,562</text></patcit> and <patcit id="pcit0012" dnum="US10299650B" dnum-type="L"><text>10/299,650</text></patcit>) all describe various open surgical forceps which seal tissue and vessels. In addition, several journal articles have disclosed methods for sealing small blood vessels using electrosurgery. An article entitled <nplcit id="ncit0001" npl-type="s"><text>Studies on Coagulation and the Development of an Automatic Computerized Bipolar Coagulator, J. Neurosurg., Volume 75, July 1991</text></nplcit>, describes a bipolar coagulator which is used to seal small blood vessels. The article states that it is not possible to safely coagulate arteries with a diameter larger than 2 to 2.5 mm. A second article is entitled <nplcit id="ncit0002" npl-type="s"><text>Automatically Controlled Bipolar Electrocoagulation - "COA-COMP", Neurosurg. Rev. (1984), pp. 187-190</text></nplcit>, describes a method for terminating electrosurgical power to the vessel so that charring of the vessel walls can be avoided.

0010Typically and particularly with respect to open electrosurgical procedures, once a vessel is sealed, the surgeon has to remove the sealing instrument from the operative site, substitute a new instrument and accurately sever the vessel along the newly formed tissue seal. As can be appreciated, this additional step may be both time consuming (particularly when sealing a significant number of vessels) and may contribute to imprecise separation of the tissue along the sealing line due to the misalignment or misplacement of the severing instrument along the center of the tissue sealing line.

0011Many endoscopic vessel sealing instruments have been designed which incorporate a knife or blade member which effectively severs the tissue after forming a tissue seal. For example, commonly-owned <patcit id="pcit0013" dnum="US7083618A"><text>US-A-7,083,618</text></patcit>, <patcit id="pcit0014" dnum="US7101371A"><text>US-A-7,101,371</text></patcit> and <patcit id="pcit0015" dnum="US7156846A"><text>US-A-7,156,846</text></patcit> (U.S. Application Serial Nos. <patcit id="pcit0016" dnum="US10116944B"><text>10/116,944</text></patcit>; <patcit id="pcit0017" dnum="US10179863B"><text>10/179,863</text></patcit>; and <patcit id="pcit0018" dnum="US10460926B"><text>10/460,926</text></patcit>) all describe endoscopic instruments which effectively seals and cuts tissue along the tissue seal. Other instruments include blade members or shearing members which simply cut tissue in a mechanical and/or electromechanical manner and are relatively ineffective for vessel sealing purposes.

0012There exists a need to develop an open electrosurgical forceps which is simple, reliable and inexpensive to manufacture and which effectively seals tissue and vessels and which allows a surgeon to utilize the same instrument to effectively sever the tissue along the newly formed tissue seal.

<u>SUMMARY</u>

0013The invention is set out in the claims. In the present disclosure, the embodiments which do not fall within the scope of the claims are provided for illustrative purpose only and do not form part of the present invention.

0014According to one aspect of the present disclosure, an open electrosurgical forceps for sealing tissue is provided. The forceps includes first and second shaft portions pivotably associated with one another. Each shaft portion has a jaw member disposed at a distal end thereof. The jaw members are movable from a first position in spaced relation relative to one another to at least one subsequent position wherein the jaw members cooperate to grasp tissue therebetween. Each of the jaw members includes an electrically conductive sealing surface for communicating electrosurgical energy through tissue held therebetween. At least one of the jaw members includes a slot formed through the sealing surface thereof.

0015The forceps further includes a cutting mechanism operatively associated with the first and second jaw members. The cutting mechanism includes a cutting element disposed within the slot of the at least one jaw member. The cutting element is movable from a first position wherein the cutting element is retracted within the slot of the at least one jaw member and a second position in which the cutting element at least partially projects from the sealing surface of the at least one jaw member. The cutting element includes at least one angled slot defined therethrough which receives a pivot pin fixed to one of the jaw members. The cutting mechanism further includes an actuator operatively associated with the cutting element which upon movement thereof selectively advances the cutting element from the first position to the second positions.

0016In one embodiment, the actuator is integrally associated with the cutting element. The cutting mechanism is pivotable about a pivot which connects the first and second jaw members. The actuator is spaced a distance from the first shaft portion. The actuator selectively activates the cutting element when moved relative to the first shaft portion.

0017In another embodiment, the cutting mechanism may include a drive rod extending through a channel formed in at least one of the first and second shaft portions. The drive rod includes a distal end operatively connected to the cutting element. The cutting mechanism may further include a tab operatively connected to the drive rod for manipulating the drive rod to urge the cutting element between the first and second positions.

0018The cutting element is supported in the slot of the jaw member such that proximal displacement of the drive rod urges the cutting element from within the slot of the jaw member to cut tissue.

0019In one embodiment, each angled slot formed in the cutting element includes a first portion in close proximity to the sealing surface and a second portion extending distally and away from the sealing surface. Proximal movement of the drive rod urges the cutting element from the first position to the second position by a camming action between the pin and the slot formed in the cutting element.

0020The open electrosurgical forceps may further include a biasing element for urging the drive rod to a distal-most position. The cutting element is pivotably disposed within the slot of the jaw member. The cutting element projects out through the jaw member and defines a camming surface.

0021In one embodiment, the second shaft portion reciprocably supports the actuator. The actuator is movable from a first position spaced from the cutting element to a second position in contact with the cutting element. In use, displacement of the actuator from the first position to the second position, the actuator engages the camming surface of the cutting element and urges the cutting element from the first position to the second position.

0022The open electrosurgical forceps may further include a biasing element for urging the cutting element to the first position. It is envisioned that movement of the actuator pivots the cutting element between the first and second positions.

0023According to another embodiment of the present disclosure, the open electrosurgical forceps may include a pair of shaft portions pivotably coupled to one another at a pivot point. Each shaft portion includes a jaw member at a distal end thereof for grasping tissue therebetween. Each jaw member includes a sealing surface for conducting electrosurgical energy through tissue grasped therebetween and one of the sealing surfaces has a slot formed therein. The forceps further includes a cutting mechanism operatively coupled to the shaft portions and has a cutting element operatively secured proximate the distal end of the forceps. The cutting mechanism is selectively movable from a first position in which the cutting element is retracted within the slot and a second position in which the cutting element at least partially projects from the slot to cut tissue disposed between the jaw members.

0024In one embodiment, the cutting mechanism includes a drive rod extending through a channel formed in at least one of the first and second shaft portions. The drive rod includes a distal end operatively connected to the cutting element. The cutting mechanism further includes a tab operatively connected to the drive rod for manipulating the drive rod to urge the cutting element between the first and second positions.

0025The cutting element is operatively engaged in the slot of the one jaw member such that axial displacement of the drive rod results in transverse displacement of the cutting element from the slot to cut tissue disposed between jaw members.

<u>BRIEF DESCRIPTION OF THE DRAWINGS</u>

0026Various embodiments of the present disclosure are described with reference to the following drawing figures. It should be understood, however, that the drawings are designed for the purpose of illustration only and not as a definition of the limits of the invention, which is defined by the appended claims.

0027<figref idref="f0001">FIG. 1A</figref> is a perspective view of a forceps according to one embodiment of the present disclosure;

0028<figref idref="f0002">FIG. 1B</figref> is a side, elevational view of the forceps of <figref idref="f0001">FIG. 1A</figref> shown in an open position;

0029<figref idref="f0003">FIG. 1C</figref> is a side, elevational view of the forceps of <figref idref="f0001">FIGS. 1A</figref> and <figref idref="f0002">1B</figref> shown in a closed position and the cutting assembly shown in an unactuated position;

0030<figref idref="f0004">FIG. 1D</figref> is a side, elevational view of the forceps of <figref idref="f0001 f0002 f0003">FIGS. 1A-1C</figref> shown in a closed position and the cutting assembly shown in an actuated position;

0031<figref idref="f0005">FIG. 2A</figref> is a cross-sectional, side elevational view of an alternate embodiment of a forceps according to the present disclosure;

0032<figref idref="f0006">FIG. 2B</figref> is an enlarged view of the indicated area of detail of <figref idref="f0005">FIG. 2A</figref>, illustrating a cutting element of the forceps in a first position;

0033<figref idref="f0007">FIG. 2C</figref> is an enlarged view of the indicated area of detail of <figref idref="f0005">FIG. 2A</figref>, illustrating the cutting element of the forceps in a second position;

0034<figref idref="f0008">FIG. 2D</figref> is an enlarged view of the indicated area of detail of <figref idref="f0005">FIG. 2A</figref>, illustrating a cutting element of the forceps according to an alternate embodiment of the disclosure;

0035<figref idref="f0009">FIG. 3A</figref> is an enlarged, schematic side elevational view of a distal end of a forceps constructed according to another embodiment of the present disclosure, illustrating a cutting assembly in a first position;

0036<figref idref="f0010">FIG. 3B</figref> is an enlarged, schematic side elevational view of the distal end of the forceps of <figref idref="f0009">FIG. 3A</figref>, illustrating the cutting assembly in a second position;

0037<figref idref="f0011">FIG. 3C</figref> is an enlarged, schematic view of an alternate biasing arrangement for the cutting assembly shown in a first position;

0038<figref idref="f0012">FIG. 3D</figref> is an enlarged, schematic view of an alternate biasing arrangement of <figref idref="f0011">FIG. 3C</figref> in a second position;

0039<figref idref="f0013">FIG. 4A</figref> is an enlarged schematic side elevational view of a distal end of a forceps constructed according to yet another embodiment of the present disclosure, illustrating a cutting assembly in a first position; and

0040<figref idref="f0014">FIG. 4B</figref> is an enlarged schematic side elevational view of the distal end of the forceps of <figref idref="f0013">FIG. 4A</figref>, illustrating the cutting assembly in a second position.

<u>DETAILED DESCRIPTION</u>

0041Referring now to <figref idref="f0001 f0002 f0003 f0004">FIGS. 1A-1D</figref>, a forceps or hemostat for use in open surgical procedures is generally designated as 100. Forceps 100 includes a first elongated shaft portion 110 and a second elongated shaft portion 120 each having a proximal end 112 and 122, respectively. In the drawings and in the descriptions which follow, the term "proximal", as is traditional, will refer to the end of forceps 100 which is closer to the user, while the term "distal" will refer to the end which is further from the user.

0042Forceps 100 includes an end effector assembly 130 which attaches to distal ends 114, 124 of shaft portions 110, 120, respectively. As explained in more detail below, end effector assembly 130 includes a pair of opposing jaw members 132, 134 which are pivotably connected about a pivot pin 135 and which are movable relative to one another to grasp tissue therebetween.

0043Each shaft portion 110 and 120 includes a handle 116, 126, respectively, disposed at proximal ends 112, 122, thereof. Each handle 116, 126 defines a finger hole 116a, 126a, respectively, therethrough for receiving a finger of the user. As can be appreciated, finger holes 116a, 126a, facilitate movement of shaft portions 110 and 120 relative to one another which, in turn, pivot the jaw members 132 and 134, about pivot pin 135, from an open position wherein the jaw members 132 and 134 are disposed in spaced relation relative to one another to a clamping or closed position wherein jaw members 132 and 134 cooperate to grasp tissue therebetween.

0044Shaft portions 110, 120 are designed to transmit a particular desired force to the opposing sealing surfaces 132a, 134a of jaw members 132, 134, respectively, when clamped. In particular, since shaft portions 110, 120 effectively act together in a spring-like manner (i.e., bending that behaves like a spring), the length, width, height and deflection of shaft portions 110, 120 will directly effect the overall transmitted force imposed on opposing jaw members 132, 134. Jaw members 132, 134 are more rigid than shaft portions 110, 120 and the strain energy stored in the shaft portions 110, 120 provides a constant closure force between jaw members 132, 134.

0045Each shaft portion 110, 120 also includes a ratchet portion 118, 128. Each ratchet, e.g., 118, extends from a proximal end of its respective shaft portion 110 towards the other ratchet 128 in a generally vertically aligned manner. The inner facing surfaces of each ratchet 118, 128 includes a plurality of flanges 118a, 128a, respectively, which project from the inner facing surface of each ratchet 118, 128 such that the ratchets 118, 128 can interlock in at least one position. In the embodiment shown in <figref idref="f0001">FIG. 1A</figref>, ratchets 118, 128 interlock at several different positions. Each ratchet position holds a specific, i.e., constant, strain energy in shaft portions 110, 120 which, in turn, transmits a specific force to jaw members 132, 134.

0046One of the shaft portions, e.g., shaft portion 120, includes a proximal shaft connector 150 which is designed to connect forceps 100 to a source of electrosurgical energy, e.g., an electrosurgical generator (not shown). Connector 150 electromechanically engages a conducting cable 152 such that the user may selectively apply electrosurgical energy as needed.

0047As briefly discussed above, jaw members 132, 134 are selectively movable about pivot pin 135 from the open position to the closed position for grasping tissue therebetween. Jaw members 132 and 134 are generally symmetrical and include similar component features which cooperate to permit facile rotation about pivot pin 135 to effect the grasping and sealing of tissue. As a result and unless otherwise noted, jaw member 132 and the operative features associated therewith are initially described herein in detail and the similar component features with respect to jaw member 134 will be briefly summarized thereafter. Moreover, many of the features of jaw members 132 and 134 are described in detail in commonly-owned <patcit id="pcit0019" dnum="US20030199869A1"><text>US 2003-0199869 A1</text></patcit>, <patcit id="pcit0020" dnum="US20030014053A1"><text>US 2003-0014053 A1</text></patcit>, <patcit id="pcit0021" dnum="US6266502A"><text>US-A-6,266,502</text></patcit>, <patcit id="pcit0022" dnum="US6277117A"><text>US-A-6,277,117</text></patcit> and <patcit id="pcit0023" dnum="WO02080797A"><text>WO 02080797</text></patcit> (<patcit id="pcit0024" dnum="US284562A" dnum-type="L"><text>U.S. Patent Application Serial Nos. 10/284,562</text></patcit>, <patcit id="pcit0025" dnum="US10116824B" dnum-type="L"><text>10/116,824</text></patcit>, <patcit id="pcit0026" dnum="US09425696B" dnum-type="L"><text>09/425,696</text></patcit>, <patcit id="pcit0027" dnum="US09178027B" dnum-type="L"><text>09/178,027</text></patcit> and <patcit id="pcit0028" dnum="US11420W" dnum-type="L"><text>PCT Application Serial No. PCT/US01/11420</text></patcit>).

0048Jaw member 132 includes an electrically conductive sealing surface 132a which conducts electrosurgical energy of a first potential to the tissue upon activation of forceps 100. Exemplary embodiments of conductive sealing surface 132a are discussed in commonly-owned, co-pending <patcit id="pcit0029" dnum="WO02080786A"><text>WO 02080786</text></patcit> (<patcit id="pcit0030" dnum="US11412W" dnum-type="L"><text>PCT Application Serial No. PCT/US01/11412</text></patcit>) and commonly owned, co-pending <patcit id="pcit0031" dnum="WO02082785A"><text>WO 02 082785</text></patcit> (<patcit id="pcit0032" dnum="US11411W" dnum-type="L"><text>PCT Application Serial No. PCT/US01/11411</text></patcit>).

0049Similar to jaw member 132, jaw member 134 includes an electrically conductive sealing surface 134a for conducting electrosurgical energy of a second potential to the tissue upon activation of forceps 100.

0050It is envisioned that one of the jaw members, e.g., 132, includes at least one stop member (not shown) disposed on the inner facing surface of the electrically conductive sealing surface 132a (and/or 134a). Alternatively or in addition, the stop member(s) may be positioned adjacent to the electrically conductive sealing surfaces 132a, 134a or proximate the pivot pin 135. The stop member(s) is/are designed to define a gap between opposing jaw members 132 and 134 during sealing. The separation distance during sealing or the gap distance is within the range of about 25.4 µm (0.001 inches) (~0.03 millimeters) to about 152.4 µm (0.006 inches) (~0.016 millimeters).

0051A detailed discussion of these and other envisioned stop members as well as various manufacturing and assembling processes for attaching, disposing, depositing and/or affixing the stop members to the electrically conductive sealing surfaces 132a, 134a are described in commonly-assigned, co-pending <patcit id="pcit0033" dnum="WO0207627A"><text>WO 0207627</text></patcit> (<patcit id="pcit0034" dnum="US11222W" dnum-type="L"><text>PCT Application Serial No. PCT/US01/11222</text></patcit>) and <patcit id="pcit0035" dnum="US20040122423A1"><text>US 2004-0122423 A1</text></patcit> (U.S. Application Serial No. <patcit id="pcit0036" dnum="US10471818B"><text>10/471,818</text></patcit>).

0052As mentioned above, two mechanical factors play an important role in determining the resulting thickness of the sealed tissue and effectiveness of the seal, i.e., the pressure applied between opposing jaw members 132 and 134 and the size of the gap between opposing jaw members 132 and 134 (or opposing sealing surface 132a and 134a during activation). It is known that the thickness of the resulting tissue seal cannot be adequately controlled by force alone. In other words, too much force and jaw members 132 and 134 may touch and possibly short resulting in little energy traveling through the tissue thus resulting in an inadequate seal. Too little force and the seal would be too thick. Applying the correct force is also important for other reasons: to oppose the walls of the vessel; to reduce the tissue impedance to a low enough value that allows enough current through the tissue; and to overcome the forces of expansion during tissue heating in addition to contributing towards creating the required end tissue thickness which is an indication of a good seal.

0053Sealing surfaces 132a and 134a are relatively flat to avoid current concentrations at sharp edges and to avoid arcing between high points. In addition, and due to the reaction force of the tissue when engaged, jaw members 132 and 134 are manufactured to resist bending, i.e., tapered along their length to provide a constant pressure for a constant tissue thickness at parallel and the thicker proximal portion of jaw members 132 and 134 will resist bending due to the reaction force of the tissue.

0054As best shown in <figref idref="f0001 f0002 f0003 f0004">FIGS. 1A-1D</figref>, forceps 100 further includes a cutting mechanism 140 operatively associated therewith. Cutting mechanism 140 includes an arm portion 142 pivotably connected to one of the first and second shaft portions 110, 120, a cutting element 144 (e.g., blade, knife, scalpel, etc.) disposed at a distal end 146a thereof, and a finger gripping element 148 disposed at a proximal end 146b thereof.

0055Cutting mechanism 140 is pivotably coupled to shaft portion 110 about pivot pin 135. Cutting mechanism 140 is pivotably coupled to shaft portion 110 in such a manner that cutting element 144 is biased (via a spring or the like) in a retracted position within a slot 134b defined in sealing surface 134a of jaw member 134. Cutting mechanism 140 is selectively movable about pivot pin 135 to deploy cutting element 144 from within slot 134b to cut tissue. Cutting element 144 may also be movably retractable depending upon a particular purpose.

0056In particular, cutting mechanism 140 is pivotable from a first position in which cutting element 144 is retained at least substantially within slot 134b of jaw member 134 to a second position in which cutting element 144 is deployed from jaw member 134. When cutting element 144 is disposed in jaw member 134, arm portion 142 of cutting assembly 142 is spaced a distance from shaft portion 110.

0057With reference to <figref idref="f0002 f0003 f0004">FIGS. 1B-1D</figref>, a method of using forceps 100 will now be described in detail. As seen in <figref idref="f0002">FIG. 1B</figref>, with shaft portions 110, 120 in the open position, such that jaw members 132, 134 are spaced from one another, and with cutting assembly 140 in the first position (i.e., within slot 134b), jaw members 132, 134 are maneuvered around the target tissue "T". As seen in <figref idref="f0003">FIG. 1C</figref>, following manipulation and positioning of jaw members 132, 134 about target tissue "T", forceps 100 is moved from the open position to the closed position. In particular, proximal ends 112, 122 of shaft portions 110 and 120 are moved toward one another, in the direction of arrows "A", to thereby proximate jaw members 132, 134 toward one another.

0058In so doing, target tissue "T" is clamped or grasped between jaw members 132, 134. Desirably, the user then activates a hand switch or a foot switch (not shown) to provide electrosurgical energy to each jaw member 132, 134 to communicate energy through target tissue "T" held therebetween to effect a tissue seal. Once target tissue "T" is sealed, as seen in <figref idref="f0004">FIG. 1D</figref>, cutting mechanism 140 is actuated, e.g., arm portion 142 is moved toward shaft portion 110 in the direction of arrow "B", to sever target tissue "T" along the tissue seal. In particular, upon movement of arm portion 142 cutting element 144 pivots about pivot pin 135 and deploys from jaw member 134 toward jaw member 132 to thereby slice, cut and/or otherwise divide target tissue "T" along the previously formed tissue seal.

0059Turing now to <figref idref="f0005 f0006 f0007">FIGS. 2A-2C</figref>, a forceps in accordance with another embodiment of the present disclosure is shown generally as 200. Forceps 200 is similar to forceps 100 and will only be described in detail to the extent necessary to identify differences in construction and operation.

0060Forceps 200 includes a cutting mechanism 240 operatively associated therewith. Cutting mechanism 240 includes a drive rod 242 for advancing cutting mechanism 240 through shaft portion 210, which will be explained in greater detail below. Drive rod 242 includes a distal end 242a configured to mechanically support a cutting element 244. Cutting element 244 is disposed in slot 234b formed in seal surface 234a of jaw member 234 (see <figref idref="f0006">FIG. 2B</figref>). Cutting mechanism 240 further includes a finger tab 246 operatively associated with drive rod 242 such that movement of finger tab 246 moves drive rod 242 in the corresponding direction.

0061Shaft portion 210 includes at least one guide channel 222 formed therein for controlling and/or guiding drive rod 242 through movement therethrough. Drive rod 242 is made from a flexible wire or plastic sheath which does not buckle upon movement thereof.

0062A spring 248 may be employed within guide channel 222 to bias cutting mechanism 240 back to the unactuated position upon proximal movement of tab 246 such that upon release of finger tab 246, the force of spring 248 automatically returns cutting mechanism 240 to its distal-most position within guide channel 222 which, in turn, retracts cutting element 244 within slot 234. While a spring 248 is shown for maintaining cutting mechanism 240 in a distal-most position, it is envisioned and within the scope of the present disclosure that a spring, e.g., a coil spring, (not shown) can be operatively associated therewith for maintaining cutting mechanism 240 in a proximal-most position and wherein finger tab 246 is positioned so as to drive cutting mechanism 240 in a distal direction.

0063As best seen in <figref idref="f0006">FIGS. 2B</figref> and <figref idref="f0007">2C</figref>, cutting element 244 is provided with at least one elongated slot, preferably a pair of elongated slots 244a, 244b, formed therein. Slots 244a, 244b are oriented at an angle with respect to the longitudinal axis of forceps 200. The portion of slots 244a, 244b which is closest to seal surface 234a of jaw member 234 is located proximal of the portion of slots 244a, 244b which is furthest from seal surface 234a of jaw member 234.

0064A pin 250 is provided within each slot 244a, 244b. Each pin 250 is fixedly positioned relative to jaw member 234. When cutting element 244 is in a distal-most position, pins 250 are located in the portion of slots 244a, 244b closest to seal surface 234a.

0065As seen in <figref idref="f0006">FIGS. 2B</figref> and <figref idref="f0007">2C</figref>, in operation and following application of electrosurgical energy to jaw members 232, 234, to thereby seal the target tissue held therebetween, the user activates finger tab 246 to thereby urge drive rod 242 in a proximal direction, as indicated by arrow "A". In so doing, cutting element 244 is urged in an angular direction relative to the longitudinal axis, as indicated by arrows "B". In particular, cutting element 244 is drawn both proximally and toward jaw member 232 (i.e., deployed from slot 234b formed in sealing surface 234a of jaw member 234, to thereby slice the target tissue which is clamped between jaw members 232, 234. In other words, cutting element 244 is drawn in direction "B" by the camming action created between slots 244a, 244b and pins 250. While cam slots 244a, 244b may be diagonal, as seen in <figref idref="f0008">FIG. 2D</figref>, cutting element 244 may be provided with cam slots 244a' and 244b' having a diagonal portion and a longitudinally extending portion integrally connected to the diagonal portion to thereby by create a slicing or cutting motion for cutting element 244.

0066Following the cutting of the target tissue, finger tab 246 may be released to thereby allow the force of spring 248 to automatically return cutting mechanism 240 to its distal-most position within guide channel 222 for subsequent sealing and cutting, which, as mentioned above, retract cutting element 244 to within slot 234b.

0067Turing now to <figref idref="f0009 f0010 f0011 f0012">FIGS. 3A-3D</figref>, a forceps 300, having a distal end in accordance with another embodiment of the present disclosure, is shown. Forceps 300 is similar to forceps 100 and 200 and will only be described in detail to the extent necessary to identify differences in construction and operation.

0068Forceps 300 includes a cutting mechanism 340 operatively associated therewith. Cutting mechanism 340 includes a cutting element 344 disposed in slot 334b formed in sealing surface 334a of jaw member 334. Cutting element 344 includes a camming surface 346 at a rear portion thereof, i.e., which extends outwardly from a side opposite sealing surface 334a of jaw member 334.

0069Cutting element 344 is pivotably supported in slot 334b by a pivot pin 350. A biasing member 348, e.g., a torsion spring or the like, may be employed within jaw member 334 to bias cutting element 344 in a retracted, i.e., undeployed, condition. Upon at least partial deployment of cutting element 344, biasing member 348 is biased such that upon release of cutting element 344, the force of the biasing member 348 automatically returns cutting element 344 into jaw member 334. Cutting mechanism 340 further includes an advancing sheath 342 operatively associated with forceps 300 for deploying cutting element 344. Any type of known actuation may be employed to advance sheath 342.

0070As seen in <figref idref="f0009">FIGS. 3A</figref> and <figref idref="f0010">3B</figref>, following application of electrosurgical energy to jaw members 132, 134 to seal tissue held therebetween, the user advances sheath 342 a distal direction, as indicated by arrow "A", to engage camming surface 346 of cutting element 344 and urge cutting element 344 out of slot 334b in the direction of arrow "B" to sever tissue. Following the cutting of the tissue, sheath 342 is withdrawn in a proximal direction until camming surface 346 of cutting element 344 is disengaged. The force of biasing member 348 automatically returns cutting mechanism 340 into slot 334b of jaw member 334.

0071Turning now to <figref idref="f0011">FIGS. 3C</figref> and <figref idref="f0012">3D</figref>, a detailed discussion of biasing member 348 is provided. As seen in <figref idref="f0011">FIG. 3C</figref>, cutting element 344 includes a rear flange or arm 360 which defines a notch 362 formed between a proximal end of cutting element 344 and arm 360. Notch 362 is located proximal of pin 350. Notch 362 extends through cutting edge 347 of cutting element 344. Cutting element 344 is fabricated from spring type steel or any other material exhibiting resilient characteristics.

0072In operation, as seen in <figref idref="f0011">FIGS. 3C</figref> and <figref idref="f0012">3D</figref>, as cutting element 344 is urged out of slot 334b of jaw member 334, in the direction of arrow "B" (<figref idref="f0010">FIG. 3B</figref>), notch 362 closes against the bias created by arm 360. Following the cutting of the target tissue, sheath 342 is withdrawn in a proximal direction until camming surface 346 of cutting element 344 is disengaged. The biasing force created by arm 360 automatically returns cutting mechanism 340 into slot 334b of jaw member 334.

0073Turning now to <figref idref="f0013">FIGS. 4A</figref> and <figref idref="f0014">4B</figref> an alternative embodiment includes a cutting element 444 is pivotably connected to a drive rod 452 by a pin 454. In this manner, as drive rod 452 is driven in a distal direction, as indicated by arrow "A", cutting element 444 is pivoted about pin 450 and urged out of slot 334b of jaw member 334. Following the cutting step, drive rod 452 is withdrawn in a proximal direction to urge cutting element 444 back into jaw member 334.

0074It is envisioned and within the scope of the present disclosure that a biasing member, e.g., a spring, (not shown) may be provided for returning cutting element 444 into jaw member 334 following deployment by drive rod 452.

0075It is further envisioned and within the scope of the present disclosure to provide a cutting element 444 configured such that cutting element 444 is pivotable about pivot pin 435.

0076It is envisioned that any of the cutting elements disclosed herein may be fabricated from plastic and/or metal (e.g., stainless steel, titanium, etc.). Desirably, the cutting elements are fabricated from non-conductive materials to thereby reduce the potential for stray currents and/or shorting.

0077From 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, none of the aforedescribed forceps require that the tissue be necessarily cut after sealing or that the tissue be sealed prior to cutting. As can be appreciated, this gives the user additional flexibility when using the instrument.

0078For example, it is also contemplated that forceps 100, 200 and/or 300 (and/or the electrosurgical generator used in connection therewith) 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. 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 jaw members 132 and 134. Commonly-owned <patcit id="pcit0037" dnum="US6796981A"><text>US-A-6,796,981</text></patcit> (<patcit id="pcit0038" dnum="US073761A" dnum-type="L"><text>U.S. Patent Application No. 10/073,761</text></patcit>, filed on February 11, 2002, entitled "Vessel Sealing System"); <patcit id="pcit0039" dnum="US20040193148A1"><text>US 2004-0193148 A1</text></patcit> (<patcit id="pcit0040" dnum="US626390A" dnum-type="L"><text>U.S. Patent Application No. 10/626,390</text></patcit>, filed on July 24, 2003, entitled "Vessel Sealing System"); <patcit id="pcit0041" dnum="US20040015163A1"><text>US 2004-0015163 A1</text></patcit> (<patcit id="pcit0042" dnum="US427832A" dnum-type="L"><text>U.S. Patent Application No. 10/427,832</text></patcit>, filed on May 1, 2003, entitled "Method and System for Controlling Output of RF Medical Generator"); <patcit id="pcit0043" dnum="US20040167508A1"><text>US 2004-0167508 A1</text></patcit> (<patcit id="pcit0044" dnum="US761524A" dnum-type="L"><text>U.S. Patent Application No. 10/761,524</text></patcit>, filed on January 21, 2004, entitled "Vessel Sealing System"); <patcit id="pcit0045" dnum="US20050203501A1"><text>US 2005-0203501 A1</text></patcit> (<patcit id="pcit0046" dnum="US539804P" dnum-type="L"><text>U.S. Provisional Application No. 60/539,804</text></patcit>, filed on January 27, 2004, entitled "Method of Tissue Fusion of Soft Tissue by Controlling ES Output Along Optimal Impedance Curve"); <patcit id="pcit0047" dnum="US20050004564A1"><text>US 2005-0004564 A1</text></patcit> (<patcit id="pcit0048" dnum="US466954P" dnum-type="L"><text>U.S. Provisional Application No. 60/466,954</text></patcit>; filed on May 1, 2003, entitled "Method and System for Programming and Controlling an Electrosurgical Generator System"); and <patcit id="pcit0049" dnum="US6398779B"><text>U.S. Patent No. 6,398,779</text></patcit>, disclose several different types of sensory feedback mechanisms and algorithms which may be utilized for this purpose.

0079Experimental results suggest that the magnitude of pressure exerted on the tissue by the sealing surfaces of jaw members 132 and 134 are important in assuring a proper surgical outcome. Tissue pressures within a working range of about 3 kg/cm² to about 16 kg/cm² and, desirably, within a working range of 7 kg/cm² to 13 kg/cm² have been shown to be effective for sealing arteries and vascular bundles. Tissue pressures within the range of about 4 kg/cm² to about 6.5 kg/cm² have proven to be particularly effective in sealing arteries and particular tissue bundles.

0080While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope of the claims appended hereto.