Spring loaded reciprocating tissue cutting mechanism in a forceps-style electrosurgical instrument

[0001] The present application is a Continuation of U.S. application Ser. No. 11/242,488, now U.S. Pat. No. 7,500,975, filed on Oct. 3, 2005, which is a Continuation-in-Part of U.S. application Ser. No. 10/991,157, now U.S. Pat. No. 7,131,970, filed on Nov. 17, 2004, which claims the benefit of priority to U.S. Provisional Patent Application Ser. No. 60/523,387, filed on Nov. 19, 2003. U.S. patent application Ser. No. 11/242,488 also claims the benefit of priority to each of U.S. Provisional Patent Application Nos. 60/616,972, filed on Oct. 8, 2004, and 60/616,968, filed on Oct. 8, 2004. All of these applications are herein incorporated by reference in their entirety.

[0002] The present disclosure relates to forceps used for open surgical procedures. More particularly, the present disclosure relates to an open forceps, having a spring loaded reciprocating tissue cutting mechanism, which applies a combination of mechanical clamping pressure and electrosurgical energy to seal tissue and which cutting mechanism is selectively activatable to sever the tissue.

[0003] A forceps is a pliers-like instrument which relies on mechanical action between its jaws to grasp, clamp and constrict vessels or tissue. 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 affect hemostasis by heating tissue and blood vessels to coagulate and/or cauterize tissue.

[0004] Certain surgical procedures require more than simply cauterizing tissue and rely on the unique combination of clamping pressure, precise electrosurgical energy control and gap distance (i.e., distance between opposing jaw members when closed about tissue) to “seal” tissue, vessels and certain vascular bundles.

[0005] Vessel 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.

[0006] In 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 0.001 inches and 0.006 inches.

[0007] With 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.

[0008] Commonly owned, U.S. Pat. No. 6,511,480, PCT Patent Application Nos. PCT/US01/11420 and PCT/US01/11218, U.S. patent application Ser. Nos. 10/116,824, 10/284,562 and 10/299,650 all describe various open surgical forceps which seal tissue and vessels. All of these references are hereby incorporated by reference herein. In addition, several journal articles have disclosed methods for sealing small blood vessels using electrosurgery. An article entitled Studies on Coagulation and the Development of an Automatic Computerized Bipolar Coagulator, J. Neurosurg., Volume 75, July 1991, 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 Automatically Controlled Bipolar Electrocoagulation—“COA-COMP”, Neurosurg. Rev. (1984), pp. 187-190, describes a method for terminating electrosurgical power to the vessel so that charring of the vessel walls can be avoided.

[0009] Typically 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.

[0010] Many 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 U.S. application Ser. Nos. 10/116,944 and 10/179,863 describe one such endoscopic instrument 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.

[0011] There 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.

[0012] According to an aspect of the present disclosure, there is provided an open electrosurgical forceps for sealing tissue. The forceps have a pair of first and second shaft portions each having 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. In that position, the jaw members cooperate to grasp tissue therebetween. The forceps also have each jaw member including an electrically conductive sealing surface which communicates electrosurgical energy through tissue held therebetween. At least one of the jaw members include a knife slot defined along a length thereof with the knife slot dimensioned to reciprocate a knife blade therein. The forceps also have a cutting mechanism for selectively actuating the knife blade from a first position wherein the knife blade is disposed at least substantially entirely within the knife slot of one jaw member to at least one subsequent position wherein the knife blade is at least partially deployed from the knife slot of the same jaw member. The knife blade is displaceable in a direction substantially transverse to a longitudinal axis of the forceps.

[0013] According to another aspect of the present disclosure, the open electrosurgical forceps have the cutting mechanism with 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 with the knife blade and the forceps have a tab operatively connected to the drive rod for manipulating the drive rod in order to displace the knife blade between the first and the at least one subsequent positions.

[0014] According to still another aspect of the present disclosure, the open electrosurgical forceps have the knife blade with a first edge defining a cutting edge and a second edge, opposite the first edge, defining a camming surface. The camming surface of the knife blade engages a corresponding camming surface formed in the slot of the jaw member to effectuate displacement of the knife blade between the first and the at least one subsequent positions.

[0015] According to another aspect of the present disclosure, the open electrosurgical forceps have a first edge of the knife blade residing in close proximity to the sealing surface when the knife blade is in the first position.

[0016] According to another aspect of the present disclosure, the open electrosurgical forceps have a slot of the jaw member defining a camming surface. The camming surface is configured to complement the camming surface of the knife blade.

[0017] According to another aspect of the present disclosure, the open electrosurgical forceps have the drive rod. The drive rod is displaced in a proximal direction with the camming surface of the knife blade engaging the camming surface of the slot formed in the jaw member to displace the knife blade from the first position to the at least one subsequent position.

[0018] According to yet another aspect of the present disclosure, the open electrosurgical forceps have a biasing member. The biasing member is for urging the drive rod to a distal most position.

[0019] According to still yet another aspect of the present disclosure, the open electrosurgical forceps have a hand switch. The hand switch is operatively associated therewith and provides a user with the ability to selectively apply electrosurgical energy.

[0020] According to another aspect of the present disclosure, the open electrosurgical forceps have a cable electrically interconnecting the forceps to a source of electrosurgical energy. The cable has a first lead electrically connected directly to a second of the jaw members and a second and third lead electrically connected to the hand switch.

[0021] According to another aspect of the present disclosure, the open electrosurgical forceps have the knife blade fabricated from a material capable of transmitting compressive and tensile forces or fabricated from spring steel.

[0022] According to another aspect of the present disclosure, the open electrosurgical forceps have each jaw member being arcuate.

[0023] According to another aspect of the present disclosure, the open electrosurgical forceps have the slot formed in the respective jaw member being arcuate.

[0024] According to another aspect of the present disclosure, the open electrosurgical forceps have the drive rod with a first rack formed therein. The first rack of the drive rod operatively engages a pinion gear rotatably supported in the second shaft portion.

[0025] According to another aspect of the present disclosure, the open electrosurgical forceps have a second gear rack slidably supported in the second shaft portion and operatively engaged with the pinion gear.

[0026] According to yet still another aspect of the present disclosure, the open electrosurgical forceps have a proximal displacement of the drive rod resulting in a distal displacement of the second gear rack.

[0027] According to another aspect of the present disclosure, the open electrosurgical forceps have a biasing member operatively connected to the second gear rack. The biasing member is for maintaining the second gear rack in a proximal-most position.

[0028] According to another aspect of the present disclosure, the open electrosurgical forceps have first and second shaft portions pivotable with respect to one another.

[0029] According to another aspect of the present disclosure, the open electrosurgical forceps with proximal displacement of the cutting mechanism results in the displacement of the knife blade in a direction having a longitudinal component of displacement and an orthogonal component of displacement. These displacements are relative to the longitudinal axis of the forceps.

[0030] According to another aspect of the present disclosure, the open electrosurgical forceps have the knife blade made from a biocompatible material.

[0031] According to another aspect of the present disclosure, the open electrosurgical forceps have a pair of first and second shaft portions with each having 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. The forceps have each jaw member including an electrically conductive sealing surface which communicates electrosurgical energy through tissue held therebetween and at least one of the jaw members including a slot defined along a length thereof. The slot is dimensioned to reciprocate a knife blade therefrom. The forceps also have a cutting mechanism which selectively actuates the knife blade from a first position to a second position. The knife blade is disposed at least substantially entirely within the knife slot of the jaw member in the first position and the knife blade moves distally from the first position to the second position in a cutting stroke. The knife blade partially deploys from the knife slot of the jaw member from the first position to the second position during the cutting stroke. The knife blade further moves in a direction perpendicular to a longitudinal axis of the jaw members from the first position to the second position during the cutting stroke when the jaw members are in the subsequent position.

[0032] According to another aspect of the present disclosure, the movement of the knife from the first position to the second position during the cutting stroke places the knife blade under tensile stress. Movement of the knife blade from the first position to the second position during the cutting stroke does not compress the knife blade.

[0033] According to another aspect of the present disclosure, the open electrosurgical forceps have a pair of first and second shaft portions each having 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 with each of said jaw members including an electrically conductive sealing surface which communicates electrosurgical energy through tissue held therebetween and at least one of the jaw members including a slot. The slot is defined along a length thereof and is dimensioned to reciprocate a knife blade therein. The knife blade has a complementary size to fit in the length of the slot. The forceps also have a cutting mechanism which selectively actuates the knife blade from a first position to a second position in a cutting stroke. The knife blade partially deploys from the knife slot of the jaw member from the first position to the second position during the cutting stroke and the knife blade cuts the sealed tissue during a first stroke in a direction from a proximal location to a distal location when the jaw members are disposed in the subsequent position.

[0034] According to another aspect of the present disclosure, the open electrosurgical forceps have the knife blade with an edge. The edge is pulled along the sealed tissue from the proximal location to the distal location upon the knife blade being deployed.

[0035] According to another aspect of the present disclosure, the open electrosurgical forceps have the cutting stroke which moves the knife from the proximal location to the distal location being actuated by a switch. This provides convenience to the surgeon.

[0062] Referring now to FIGS. 1-13, a forceps or hemostat for use in open surgical procedures, preferably, open electrosurgical procedures, is generally designated as 100. Forceps 100 includes a first elongated shaft portion 110 and a second elongated shaft portion 120. Each shaft portion 110, 120 includes a proximal end 112 and 122, respectively, and a distal end 114, 124, 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.

[0063] Forceps 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 (see FIG. 7) and which are movable relative to one another to grasp tissue therebetween.

[0064] Preferably, each 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.

[0065] As best seen in FIGS. 1, 3 and 7, second shaft portion 120 is bifurcated to define an elongated channel 121 therealong which is dimensioned to receive first shaft portion 110 therein. More particularly, second shaft portion 120 is made from two halves 120a, 120b (see FIG. 7) which are matingly engaged during assembly to form second shaft portion 120 and to define elongated channel 121. It is envisioned that the two halves 120a, 120b may be secured to one another by sonic welding at a plurality of different points along the perimeter thereof of the two housing halves 120a, 120b may be mechanically engaged in any other known fashion, including and not limited to, snap-fitting, gluing, screwing, and the like. During assembly, first shaft portion 110 is positioned within second shaft portion 120 and secured about pivot pin 135 which allows first and second shaft portions 110 and 120 to pivot with respect to one another.

[0066] As seen in FIGS. 1-3 and 7, one of shaft portions 110, 120, e.g., second 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 an electrosurgical conducting cable 151 such that the user may selectively apply electrosurgical energy as needed. Alternatively, cable 151 may be fed directly into second shaft portion 120 as best seen in FIG. 3.

[0067] As explained in more detail below, the distal end of cable 151 connects to a handswitch 50 to permit the user to selectively apply electrosurgical energy, as needed, to seal tissue grasped between jaw members 132, 134. More particularly, the interior of cable 151 houses leads 151a, 151b and 151c which upon activation of handswitch 50 conduct the different electrical potentials from the electrosurgical generator to jaw members 132, 134. As can be appreciated, positioning handswitch 50 on forceps 100 gives the user more visual and tactile control over the application of electrosurgical energy. These aspects are explained below with respect to the discussion of handswitch 50 and the electrical connections associated therewith.

[0068] As briefly discussed above, jaw members 132, 134 of end effector assembly 130 are selectively pivotable about pivot pin 135 from the open position, for receiving tissue therebetween, 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 affect 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 U.S. patent application Ser. Nos. 10/284,562, 10/116,824, 09/425,696, 09/178,027 and PCT Application Serial No. PCT/US01/11420 the contents of which are all hereby incorporated by reference in their entirety herein.

[0069] Jaw member 132 includes an insulated outer housing 133 which is dimensioned to mechanically engage an electrically conductive sealing surface 132a (see FIG. 15). Insulated outer housing 133 extends along the entire length of jaw member 132 to reduce alternate or stray current paths during sealing and/or incidental burning of tissue. The electrically conductive sealing surface 132a conducts electrosurgical energy of a first potential to the tissue upon activation of handswitch 50. Insulated outer housing 133 is dimensioned to securely engage the electrically conductive sealing surface 132a. It is envisioned that this may be accomplished by stamping, by overmolding, by overmolding a stamped electrically conductive sealing plate and/or by overmolding a metal injection molded seal plate. Other methods of affixing electrically conductive sealing surface 132a to insulated outer housing 133 are described in detail in one or more of the above-identified references.

[0070] It is also envisioned that the electrically conductive sealing surface 132a may include a pinch trim (not shown) which facilitates secure engagement of the electrically conductive sealing surface 132a to the insulated outer housing 133 and also simplifies the overall manufacturing process. It is also contemplated that the electrically conductive sealing surface 132a may include an outer peripheral edge which has a radius and the insulated outer housing 133 meets the electrically conductive sealing surface 132a along an adjoining edge which is generally tangential to the radius and/or meets along the radius. Preferably, at the interface, the electrically conductive sealing surface 132a is raised relative to the insulated outer housing 133. These and other envisioned embodiments are discussed in commonly-owned, co-pending PCT Application Serial No. PCT/US01/11412 and commonly owned, co-pending PCT Application Serial No. PCT/US01/11411, the contents of both of these applications being incorporated by reference herein in their entirety.

[0071] Preferably, the insulated outer housing 133 and the electrically conductive sealing surface 132a are dimensioned to limit and/or reduce many of the known undesirable effects related to tissue sealing, e.g., flashover, thermal spread and stray current dissipation. All of the aforementioned and cross referenced manufacturing techniques produce an electrode having an electrically conductive sealing surface 132a which is substantially surrounded by an insulated outer housing 133.

[0072] Likewise, as seen in FIG. 7, jaw member 134 includes similar elements which include: an outer housing 135 which engages an electrically conductive sealing surface 134a. The electrically conductive sealing surface 134a conducts electrosurgical energy of a second potential to the tissue upon activation of the handswitch 50.

[0073] It 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 preferably designed to facilitate gripping and manipulation of tissue and to define a gap between opposing jaw members 132 and 134 during sealing. Preferably the separation distance during sealing or the gap distance is within the range of about 0.001 inches (˜0.03 millimeters) to about 0.006 inches (˜0.016 millimeters).

[0074] A 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 PCT Application Serial No. PCT/US01/11222 which is hereby incorporated by reference in its entirety herein.

[0075] As 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.

[0076] Preferably, sealing 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 preferably 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.

[0077] As best seen in FIGS. 7, 9 and 12, each jaw member 132, 134 includes a knife slot 132b, 134b disposed therebetween (i.e., formed in respective sealing surfaces 132a, 134a thereof which is configured to allow reciprocation of a cutting mechanism 140 therewithin. One example of a knife slot is disclosed in commonly-owned U.S. patent application Ser. No. 10/284,562, the entire contents of which are hereby incorporated by reference herein. Preferably, the complete knife slot is formed when two opposing knife slots 132b, 134b come together upon grasping of the tissue. It is envisioned that the knife slot may be tapered or some other configuration which facilitates or enhances cutting of the tissue during reciprocation of cutting mechanism 140 in the proximal and distal directions. Moreover, the knife channel may be formed with one or more safety features which prevent cutting mechanism 140 from advancing through and/or otherwise slicing tissue until jaw members 132, 134 are closed onto the tissue.

[0078] For example, a lockout mechanism, operatively associated with cutting mechanism 140, may be provided to prevent advancement of cutting mechanism 140 until jaw embers 132, 134 are positioned about the tissue to be treated. Examples of lockout mechanisms and features are described in commonly-owned U.S. application Ser. Nos. 10/460,926, 10/461,550 and 10/462,121, which are all incorporated by reference herein in their entirety.

[0079] As best shown in FIGS. 3, 4 and 7, the arrangement of first shaft portion 110 is different from second shaft portion 120. More particularly, second shaft portion 120 is hollow to define a chamber therein, which chamber is dimensioned to house both handswitch 50 (and the electrical components associated therewith as explained in more detail below) and cutting mechanism 140.

[0080] As best seen in FIGS. 4-7, 10 and 11, cutting mechanism 140 includes a finger tab 142 which is operatively associated with a drive rod 144 such that movement of finger tab 142 moves drive rod 144 in a corresponding direction within second shaft portion 120. Preferably, finger tab 142 extends from elongated slot 121 formed in second shaft portion 120. Drive rod 144 includes a distal end 144a which is configured to mechanically support a knife blade 146 thereto.

[0081] Desirably, drive rod 144 defines a first gear track or rack 148 formed in a surface thereof. In one embodiment, it is envisioned that a pinion gear 160 may be rotatably supported in second shaft portion 120 so as to operatively engage first rack 148 of drive rod 144. A second gear rack 162 may be slidably supported in second shaft portion 120 so as to also operatively engage pinion gear 160. Pinion gear 160 is inter-disposed between first gear rack 148 and second gear rack 162 so as to mechanically mesh both gear racks 148 and 162 with one another and convert proximal displacement of drive rod 144 into distal translation of second gear rack 162 and vice versa. More particularly, when the user pulls finger tab 142 in a proximal direction, as represented by arrow “A” of FIG. 22, the drive rod 144 is translated proximally which, in turn, rotates pinion gear 160. Rotation of pinion gear 160, in turn, forces second rack 162 to translate in a distal direction.

[0082] It is envisioned that multiple gears or gears with different gear ratios may be employed to reduce surgical fatigue which may be associated with actuating cutting mechanism 140. In addition, it is contemplated that racks 148 and 162 may be of different length to provide additional mechanical advantage for advancing the jaw members through the tissue. Desirably, the rack and pinion arrangement may be curved for spatial purposes and to facilitate handling and/or to enhance the overall ergonomics of the forceps 10.

[0083] Preferably, a biasing member 164 (e.g., a coil spring) is operatively connected to second gear rack 162 in such a manner that biasing member 164 tends to draw and/or bias second gear rack 162 to a proximal-most position and, in turn, tends to press and/or bias drive rod 142 to a distal-most position. As will be described in greater detail below, biasing member 164 automatically returns drive rod 144 to an un-advanced position and, in turn, return knife blade 146 to the retracted position. A biasing member may be operatively associated with drive rod 144 and/or second gear rack 162 in any manner so as to achieve the same purpose.

[0084] Preferably, drive rod 144 is made from a flexible sheet or band of metal or plastic which does not buckle upon forward movement thereof. In other words, drive rod 144 is fabricated from a flexible material capable of transmitted both compressive and tensile forces. For example, drive rod 144 may be fabricated from spring steel.

[0085] Preferably, finger tab 142 includes one or more ergonomically friendly features which enhance the tactile feel and grip of the user to facilitate actuation of finger tab 142. Such features may include, raised protuberances, rubber inserts, scallops and gripping surfaces, and the like.

[0086] As seen in FIGS. 7, 10, 11, 15, 18, 21, 23 and 24, knife blade 146 includes an elongate body portion 146a having a distal end 146b and a proximal end 146c. Preferably, proximal end 146c of knife blade 146 is configured to mechanically engage distal end 144a of drive rod 144. Knife blade 146 defines a first edge 146d forming the cutting edge of knife blade 146 and a second edge 146e, opposite first edge 146d, defining a camming surface or bulge 146f. Preferably, knife blade 146 is disposed in knife slot 132b of first jaw member 132 such that first edge 146d of knife blade 146 is oriented toward tissue contacting surface 132a. As such, knife blade 146 is seated in knife slot 132b such that camming surface 146f of second edge 146e is operatively associated with a camming surface 132c formed in knife slot 132b of first jaw member 132.

[0087] As will be described in greater detail below, as cutting mechanism 140 is drawn in a proximal direction (e.g., in the direction of arrow “A” of FIG. 22), knife blade 146 is also drawn in a proximal direction. In so doing, camming surface 146f of second edge 146e of knife blade 146 engages and/or otherwise rides against camming surface 132c formed in knife slot 132b of first jaw member 132. As such, distal end 146b and, in turn, first edge 146d of knife blade 146 is urged out of knife slot 132b of first jaw member 132 and towards knife slot 134b of second jaw member 134. Due to the resiliency of knife blade 146, as cutting mechanism 140 is driven in a distal direction, knife blade 146 and, in turn, first edge 146d of knife blade 146 is retracted into knife slot 132b.

[0088] Camming surface 146f of second edge 146e of knife blade 146 engages with camming surface 132c of knife slot 132b in order to displace knife blade 146 in a direction which is transverse to a longitudinal axis of forceps 100, preferably transverse to a longitudinal axis of second shaft portion 120. In other words, longitudinal displacement of finger tab 142 results in knife blade 146 displacing in a direction having a component of displacement which is parallel to the longitudinal axis and a component of displacement which is orthogonal to the longitudinal axis. This results in knife blade 146 cutting tissue with a slicing action and/or motion.

[0089] As seen in FIGS. 1-3, 7, 8, 16 and 17, forceps 100 may include a ratchet for selectively locking jaw members 132, 134 relative to one another at various positions during pivoting. A first ratchet interface 76 preferably extends from proximal end 112 of first shaft portion 110 towards a second ratchet interface 78 preferably extending from proximal end 122 of second shaft portion 120, in a generally vertically aligned manner such that the inner facing surfaces of each ratchet 76 and 78 abut one another upon closure about the tissue. Preferably, each ratchet interface 76, 78 includes a plurality of flanges 76a, 78a, respectively, (in the interest of clarity, only one flange is shown) which project from the inner facing surface of each ratchet interface 76 and 78 such that the ratchet interfaces 76a, 78a interlock in at least one position.

[0090] Preferably, each position associated with the cooperating ratchet interfaces 76a, 78a hold a specific, i.e., constant, strain energy in the shaft portions 110, 120, which, in turn, transmits a specific closing force to jaw members 132, 134. It is envisioned that the ratchet may include graduations or other visual markings which enable the user to easily and quickly ascertain and control the amount of closure force desired between jaw members 132, 134.

[0091] As seen in FIG. 4, the electrical details relating to switch 50 are shown in greater detail. More particularly, and as mentioned above, cable 150 includes three electrical leads 151a-151c which are fed through second shaft portion 120. Cable 150 is fed into the bottom or proximal end of second shaft portion 120 and is held securely therein by one or more mechanical interfaces (not shown). Lead 151c extends directly from cable 150 and connects to jaw member 134 to conduct the second electrical potential thereto. Leads 151a, 151b extend from cable 150 and connect to the hand switch or joy-stick-like toggle switch 50.

[0092] Several different types of handswitches 50 are envisioned, for example, one particular type of handswitch is disclosed in commonly-owned, co-pending U.S. patent application Ser. No. 10/460,926, the entire contents of which are hereby incorporated by reference herein.

[0093] Electrical leads 151a and 151b are electrically connected to switch 50. When switch 50 is depressed, a trigger lead carries the first electrical potential from switch 50 to first jaw member 132. As mentioned above, the second electrical potential is carried by lead 151c directly from the generator (not shown) to second jaw member 134. It is envisioned that a safety switch or circuit (not shown) may be employed such that switch 50 cannot fire unless jaw members 132 and 134 are closed and/or unless jaw members 132 and 134 have tissue held therebetween. In the latter instance, a sensor (not shown) may be employed to determine if tissue is held therebetween. 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 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, co-pending U.S. patent application Ser. No. 10/427,832 the entire contents of which are hereby incorporated by reference herein.

[0094] Preferably, jaw members 132 and 134 are electrically isolated from one another such that electrosurgical energy can be effectively transferred through the tissue to form a tissue seal. Preferably, each jaw member, e.g., 132, includes a uniquely-designed electrosurgical cable path disposed therethrough which transmits electrosurgical energy to the electrically conductive sealing surface 132a. It is envisioned that jaw member 132 may include one or more cable guides or crimp-like electrical connectors to direct the cable lead towards electrically conductive sealing surface 132a. Preferably, the cable lead is held loosely but securely along the cable path to permit pivoting of jaw member 132 about pivot pin 135.

[0095] Desirably, as seen in FIG. 7, cable leads 151a-151c are protected by two insulative layers, an outer protective sheath which surrounds all three leads 151a-151c and a secondary protective sheath which surrounds each individual cable lead 151a-151c. The two electrical potentials are isolated from one another by virtue of the insulative sheathing surrounding each cable lead 151a-151c.

[0096] Turning now to FIGS. 14-25, in operation, the surgeon simply utilizes the two opposing handles 116, 126 to approximate and grasp tissue between jaw members 132, 134. The surgeon then activates handswitch 50 (or in certain instances a footswitch, not shown) to provide electrosurgical energy to each jaw member 132, 134 to communicate energy through the tissue held therebetween. Once sealed, the surgeon activates cutting mechanism 140 to deploy knife blade 146 to slice through the treated tissue to sever and divide the tissue along the tissue seal.

[0097] In particular, as seen in FIGS. 14 and 15, with forceps 100 in the open condition, the surgeon positions end effector 130 of forceps 100, in the operative field, such that the tissue to be treated “T” is disposed between jaw members 132, 134. As seen in FIGS. 16-22, the surgeon then squeezes (i.e., approximates) opposing handles 116, 126 to thereby close jaw members 132, 134 onto tissue “T”. Desirably, flange 76a of first ratchet interface 76 may be interlocked with flange 78a of second ratchet interface 78 in order to transmit a specific closing force to jaw members 132, 134. The surgeon then activates handswitch 50 to provide electrosurgical energy to each jaw member 132, 134 and to communicate energy through tissue “T” held therebetween and to effectively seal tissue “T” at “S”, see FIGS. 19 and 20.

[0098] Once tissue “T” has been sealed at “S”, as seen in FIGS. 21-24, the surgeon may, if desired and/or necessary, activate cutting mechanism 140. As described above, cutting mechanism 140 is activated by withdrawing on finger tab 142 in a proximal direction (i.e., in the direction of arrow “A”) which, in turn, draws knife blade 146 in a proximal direction. In so doing, the camming surface of second edge 146e of knife blade 146 engages and/or otherwise rides against camming surface 132c formed in knife slot 132b of first jaw member 132. As such, distal end 146b and, in turn, first edge 146d of knife blade 146 is urged out of knife slot 132b of first jaw member 132 and towards knife slot 134b of second jaw member 134 to thereby cut, slice and/or otherwise divide tissue “T” at “S”.

[0099] Following the cutting action, the surgeon may displace finger tab 142 in a distal direction in order to return knife blade 146 to knife slot 132b. In particular, knife blade 146 and, in turn, first edge 146d of knife blade 146 is retracted into knife slot 132b.

[0100] 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, none of the afore described 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.

[0101] For example, it is also contemplated that forceps 100 (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 jaw members 132 and 134. 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 U.S. patent application Ser. No. 10/073,761, filed on Feb. 11, 2002, entitled “Vessel Sealing System”; U.S. patent application Ser. No. 10/626,390, filed on Jul. 24, 2003, entitled “Vessel Sealing System”; U.S. patent application Ser. No. 10/427,832, filed on May 1, 2003, entitled “Method and System for Controlling Output of RF Medical Generator”; U.S. patent application Ser. No. 10/761,524, filed on Jan. 21, 2004, entitled “Vessel Sealing System”; U.S. Provisional Application No. 60/539,804, filed on Jan. 27, 2004, entitled “Method of Tissue Fusion of Soft Tissue by Controlling ES Output Along Optimal Impedance Curve”; U.S. Provisional Application No. 60/466,954; filed on May 1, 2003, entitled “Method and System for Programming and Controlling an Electrosurgical Generator System”; and U.S. Pat. No. 6,398,779, disclose several different types of sensory feedback mechanisms and algorithms which may be utilized for this purpose. The contents of these applications are hereby incorporated by reference herein.

[0102] Experimental 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, preferably, 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 tissue bundles.

[0103] In one embodiment, shaft portions 110, 120 are manufactured such that the spring constant of shaft portions 110, 120, in conjunction with the placement of the ratchet interfaces 76a, 78a, will yield pressures within the above working range. In addition, the successive positions of the ratchet interfaces (if provided) increase the pressure between opposing sealing surfaces incrementally within the above working range.

[0104] Also, although the electrical connections are preferably incorporated within second shaft portion 120 and forceps 100 is intended for right-handed use, it is contemplated that the electrical connections may be incorporated within first shaft portion 110 depending upon a particular purpose and/or to facilitate manipulation by a left-handed user.

[0105] It is also envisioned that drive rod 142 may be connected to the same or alternate source of electrosurgical energy and may be selectively energizable by the surgeon during cutting. As can be appreciated, this would enable the surgeon to electrosurgically cut tissue “T” along the tissue seal at “S”. As a result thereof, a substantially dull blade may be employed to electrosurgically cut tissue “T”.

[0106] It is also envisioned that a substantially dull knife blade may be utilized for cutting mechanism 140 which, due to the clamping pressure between the opposing jaw members 132, 134 and due to the force with which knife blade 146 is urged out of knife slot 132a, tissue “T” will sever along the tissue seal at “S”.

[0107] In one embodiment, a sealing and cutting mechanism is utilized which is selectively attachable to a conventional forceps. In other words, the sealing and cutting mechanisms are disposable which shaft portions 110, 120 are reposable. The disposable sealing and cutting mechanisms, along with their respective electrosurgical elements, simply mount atop one or both shafts of a conventional forceps to enable the surgeon to seal and cut tissue.

[0108] In one embodiment, knife blade 146 is desirably flexible to advance through a curved knife channel. For example, upon distal or proximal displacement of the cutting mechanism, the knife blade will simply flex and ride around the knife slot through the tissue held therebetween by the jaw members. It is also contemplated that the forceps may include a safety blade return mechanism (not shown). For example and as mentioned above, cutting mechanism 140 may include one of more biasing members which automatically return the knife blade to the retracted position after actuation thereof. In addition, a manual return may be included which allows the user to manually return knife blade 146 if the automatic blade return (e.g., biasing member) should fail due to sticking, skewing, or some other unforeseen surgical condition. Should the automatic return fail, the surgeon simply has to displace finger tab 142 in a distal direction to drive cutting mechanism forward and retract knife blade 146 into slot 132a of jaw member 132. A significant advantage of the present disclosure is that movement of the knife from a first position to a second position during a cutting stroke places the knife blade under tensile stress. The movement of the knife from the first position to the second position during the cutting stroke also does not compress the knife. This arrangement is very conducive as any compressive stress on the knife is disfavored greatly as this compressive stress may break the knife. Also, the movement of the knife from the first position to the second position during a cutting stroke placing the knife blade under tensile stress promotes using the knife edge instead of another chopping motion that places strain on the knife. The tensile stress is more conducive to a more natural motion of the knife for cutting, and is advantageous over any other types of devices.

[0109] While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of preferred embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.