Forceps with spring loaded end effector assembly

[0001] This application claims the benefits of and priority to U.S. patent application Ser. No. 10/937,455 entitled “FORCEPS WITH SPRING LOADED END EFFECTOR ASSEMBLY”, now U.S. Pat. No. 7,195,631, which was filed on Sep. 9, 2004, the entire contents of which are hereby incorporated by reference herein.

[0002] 1. Technical Field

[0003] The present disclosure relates to endoscopic surgical instruments and, more particularly, to an end effector assembly for use in connection with endoscopic instruments for grasping, sealing, dividing and/or dissecting tissue.

[0004] 2. Background of Related Art

[0005] A hemostat or forceps is a simple pliers-like tool which uses mechanical action between its jaws to constrict vessels and is commonly used in open surgical procedures to grasp, dissect and/or clamp tissue. Electrosurgical forceps utilize both mechanical clamping action and electrical energy to effect hemostasis by heating the tissue and blood vessels to coagulate, cauterize and/or seal tissue.

[0006] Over the last several decades, more and more surgeons are complimenting traditional open methods of gaining access to vital organs and body cavities with endoscopes and endoscopic instruments which access organs through small puncture-like incisions. Endoscopic instruments are inserted into the patient through a cannula, or port, that has been made with a trocar. Typical sizes for cannula range from three millimeters to twelve millimeters. Smaller cannulas are usually preferred, which, as can be appreciated, ultimately presents a design challenge to instrument manufacturers who must find ways to make surgical instruments that fit through the particularly-sized cannulas.

[0007] Certain endoscopic surgical procedures require cutting blood vessels or vascular tissue. However, due to space limitations surgeons can have difficulty suturing vessels or performing other traditional methods of controlling bleeding, e.g., clamping and/or tying-off transected blood vessels. Blood vessels, in the range below two millimeters in diameter, can often be closed using standard electrosurgical techniques. However, if a larger vessel is severed, it may be necessary for the surgeon to convert the endoscopic procedure into an open-surgical procedure and thereby abandon the benefits of laparoscopy.

[0008] 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, Jul. 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, 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] As mentioned above, by utilizing an electrosurgical forceps, a surgeon can either cauterize, coagulate/desiccate and/or simply reduce or slow bleeding, by controlling the intensity, frequency and duration of the electrosurgical energy applied through the jaw members to the tissue. The electrode of each jaw member is charged to a different electric potential such that when the jaw members grasp tissue, electrical energy can be selectively transferred through the tissue.

[0010] In order to effect a proper seal with larger vessels, two predominant mechanical parameters must be accurately controlled: the pressure applied to the vessel; and the gap distance between the electrically conductive surfaces. More particularly, accurate application of pressure is important to oppose the walls of the vessel; to reduce the tissue impedance to a low enough value that allows enough electrosurgical energy through the tissue; to overcome the forces of expansion during tissue heating; and to contribute to the end tissue thickness which is an indication of a good seal. It has been determined that a typical fused vessel wall is optimum between about 0.001 and about 0.006 inches. Below this range, the seal may shred or tear and above this range the lumens may not be properly or effectively sealed.

[0011] With respect to smaller vessels, the pressure applied to the tissue tends to become less relevant whereas 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 vessels become smaller.

[0012] Various known electrosurgical instruments and methods may occasionally be able to seal larger vessels using an appropriate electrosurgical power curve, coupled with an instrument capable of applying a large closure force to the vessel walls, however, these instruments and methods rarely provide consistent and accurate vessel sealing. Moreover, the process of coagulating small vessels is fundamentally different than electrosurgical vessel sealing. For the purposes herein, “coagulation” is defined as a process of desiccating tissue wherein the tissue cells are ruptured and dried. “Vessel sealing” or “Tissue Sealing” is defined as the process of liquefying the collagen in the tissue so that it reforms into a fused mass. Thus, coagulation of small vessels is sufficient to permanently close the vessels but not necessarily seal the vessels. Larger vessels need to be sealed to assure permanent closure.

[0013] Many known electrosurgical 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. Other instruments rely on clamping pressure alone to procure proper sealing thickness and are not designed to take into account gap tolerances and/or parallelism and flatness requirements which are parameters which, if properly controlled, can assure a consistent and effective tissue seal. For example, it is known that it is difficult to adequately control thickness of the resulting sealed tissue by controlling clamping pressure alone for either of two reasons: 1) if too much force is applied, there is a possibility that the two poles will touch and energy will not be transferred through the tissue resulting in an ineffective seal; or 2) if too low a force is applied the tissue may pre-maturely move prior to activation and sealing and/or a thicker, less reliable seal may be created.

[0014] As mentioned above, in order to properly and effectively seal larger vessels or tissue, a greater closure force between opposing jaw members is required. It is known that a large closure force between the jaws typically requires a large moment about the pivot for each jaw. This presents a challenge because the jaw members are typically affixed with pins which are positioned to have a small moment arms with respect to the pivot of each jaw member. A large force, coupled with a small moment arm, is undesirable because the large forces may shear the pins. As a result, designers must compensate for these large closure forces by either designing instruments with metal pins and/or by designing instruments which at least partially offload these closure forces to reduce the chances of mechanical failure (see, for example, commonly owned U.S. Pat. No. 6,585,735). As can be appreciated, if metal pivot pins are employed, the metal pins must be insulated to avoid the pin acting as an alternate current path between the jaw members which may prove detrimental to effective sealing.

[0015] Increasing the closure forces between electrodes may have other undesirable effects, e.g., it may cause the opposing electrodes to come into close contact with one another which may result in a short circuit and a small closure force may cause pre-mature movement of the issue during compression and prior to activation.

[0016] Typically and particularly with respect to endoscopic electrosurgical procedures, once a vessel or tissue is sealed, the surgeon has to remove the sealing instrument from the operative site, substitute a new instrument through the cannula and accurately sever the vessel or tissue along the newly formed seal. As can be appreciated, this additional step may be both time consuming (particularly when sealing a significant number of vessels or tissue) and may contribute to imprecise separation of the vessels or tissue along the sealing line due to the misalignment or misplacement of the severing instrument along the center of the sealing line.

[0017] Several attempts have been made to design an instrument which incorporates a knife or blade member which effectively severs the tissue after forming a tissue seal. For example, U.S. Pat. No. 5,674,220 to Fox et al. discloses a transparent instrument which includes a longitudinally reciprocating knife which severs the tissue once sealed. The instrument includes a plurality of openings which enable direct visualization of the tissue during the sealing and severing process. This direct visualization allows a user to visually and manually regulate the closure force and gap distance between jaw members to reduce and/or limit certain undesirable visual effects known to occur when sealing vessels, e.g., thermal spread, charring, etc. As can be appreciated, the overall success of creating an effective tissue seal with this instrument is greatly reliant upon the user's expertise, vision, dexterity, and experience in judging the appropriate closure force, gap distance and length of reciprocation of the knife to uniformly, consistently and effectively seal and separate the tissue at the seal along an ideal cutting plane.

[0018] U.S. Pat. No. 5,702,390 to Austin et al. discloses a vessel sealing instrument which includes a triangularly-shaped electrode which is rotatable from a first position to seal tissue to a second position to cut tissue. Again, the user must rely on direct visualization and expertise to control the various effects of sealing and cutting tissue.

[0019] Some systems utilize rigid-faced jaw members to provide the necessary closure force to coagulate tissue. These instruments typically rely on drive rod or pull rod to carry the longitudinal force to maintain consistent and repeatable pressure between the jaw members to effectively clamp or coagulate tissue (e.g., a spring actuated pull rod disposed in the handle which provides the necessary clamping force).

[0020] Still other systems utilize arcuately-shaped, wire-like jaw members which cooperate with a closure tube to grasp tissue for dissection and coagulation. It is believed that these wire-like jaw frames are not designed to seal tissues since, by and large, the jaw frames do not provide the forces necessary to effect consistent and accurate vessel sealing.

[0021] Thus, a need exists to develop an endoscopic electrosurgical instrument which provides the necessary closure forces to seal vessels and other vascular tissue and, when activated, effectively and consistently seals and separates the vessel or the tissue along the seal.

[0022] The present disclosure relates to an endoscopic forceps for treating tissue including a handle assembly and an end effector assembly. The handle assembly has an elongated shaft extending therefrom. The elongated shaft is movable relative to the handle assembly by an actuator. The end effector assembly is attached to a distal end of the elongated shaft and has first and second jaw members. The jaw members are movable about a pivot from a first position in a spaced relation relative to one another to a second position for clamping tissue. Each of the jaw members includes an insulative housing and a flange. The insulative housing has an electrically conductive, inwardly facing tissue contacting surface. The flange has at least one camming surface. The flange includes a spring-like tail which mounts at least partially within the distal end of the elongated shaft to bias the jaw members in an open configuration. A proximal portion of the spring-like tail is biased radially outward within the distal end of the elongated shaft. The actuator is movable relative to the handle to actuate the elongated shaft from a first position wherein the elongated shaft remains proximal to the flanges of the jaw members and the jaw members are biased in a open configuration to at least one subsequent position wherein the distal end of the elongated shaft cams the flanges to pivot the jaw members toward the second position to clamp tissue.

[0023] In an embodiment of the present disclosure, the flanges of the jaw members cooperate with the distal end of the elongated shaft to provide a clamping pressure within the range of at least about 3 kg/cm² to effectively seal tissue upon application of electrosurgical energy.

[0024] It is envisioned for the flanges of the jaw members to include sloped forward surfaces which cooperate with the distal end of the elongated shaft to maintain the jaw members in the second position.

[0025] In an exemplary embodiment of the disclosure, clamping pressure is maintained within the range of at least about 3 kg/cm² once the distal end of the elongated shaft translates over the forward surfaces of the flanges.

[0026] In an embodiment of the present disclosure, an endoscopic forceps for treating tissue is provided. The forceps of this embodiment includes a handle assembly, an end effector assembly and a knife actuator. The handle assembly has an elongated shaft extending from it. The shaft is movable relative to the handle assembly by an actuator. The end effector assembly is attached to a distal end of the shaft and includes first and second jaw members. The jaw members are movable about a pivot from a first position in a spaced relation to one another to a second position for clamping tissue. The knife actuator advances a knife through tissue held between the jaw members. Each of the jaw members includes an insulative housing, a flange and a knife channel. The insulative housing has an electrically conductive, inwardly facing tissue contacting surface. The flange has at least one camming surface. The flange also includes a spring-like tail which mounts at least partially within the distal end of the elongated shaft to bias the jaw members in an open configuration. A proximal portion of the spring-like tail is biased radially outward within the distal end of the elongated shaft. The actuator is movable relative to the handle to actuate the elongated shaft from a first position where the elongated shaft remains proximal to the flanges of the jaw members and the jaw members are biased in an open configuration to at least one subsequent position where the distal end of the elongated shaft cams the flanges to pivot the jaw members toward the second position to clamp tissue

[0037] Detailed embodiments of the presently disclosed instruments, devices and systems will now be described in detail with reference to the drawing figures wherein like reference numerals identify similar or identical elements. In the drawings and in the description which follows, the term “proximal”, as is traditional, will refer to the end of the instrument, device and/or system which is closest to the operator while the term “distal” will refer to the end of the instrument, device and/or system which is furthest from the operator.

[0038] Referring to FIG. 1A, an endoscopic instrument according to one embodiment of the present disclosure is designated generally as reference numeral 10. Endoscopic instrument 10 includes an elongated shaft 12 which is mechanically coupled to a handle assembly 18 at a proximal end 12a thereof and a distal end 12b which is mechanically coupled to an end effector assembly 100. Elongated shaft 12 is preferably hollow and includes internal electrical connections which provide electrical continuity to the end effector assembly 100 as described in more detail below.

[0039] End effector assembly 100 includes a pair of opposing jaw members 110 and 120 which are operatively associated with the distal end 12b of elongated shaft 12. Preferably, handle assembly 18 mechanically engages proximal end 12a of shaft 12 and includes an activator 20 for imparting movement to the jaw members 110 and 120 from an open position wherein jaw members 110 and 120 are disposed in spaced relation relative to one another, to a clamping or closed position wherein jaw members 110 and 120 cooperate to grasp tissue therebetween.

[0040] With continued reference to FIG. 1A, activator 20 includes a movable handle 26 having an aperture 34 defined therethrough for receiving at least one of an operator's fingers and a fixed handle 28 having an aperture 32 defined therein for receiving an operator's thumb. Movable handle 26 is selectively movable from a first position relative to fixed handle 28 to a second position in closer proximity to fixed handle 28 to close jaw members 110 and 120. The specific mechanics of how the actuator 20 moves the jaw members 110 and 120 from the open to close positions is discussed in more detail below with reference to FIGS. 1B and 1C. The internal mechanically cooperating components associated with longitudinally translating the elongated shaft 12 (or another tube concentrically disposed therein (not shown)) to cam the jaw members 110 and 120 from the open to closed positions is commonly known.

[0041] Preferably, fixed handle 28 includes a channel 27 which extends proximally for receiving a ratchet 30 which is coupled to movable handle 26. Ratchet 30 is preferably designed to allow a user to progressively lock, at multiple positions, and subsequently release movable handle 26 relative to fixed handle 28. The handle structure, in turn, allows for the progressive closure of end effector assembly 100 as well as locking engagement of opposing jaw members 110, 120. In some cases it may be preferable to include other mechanisms to control and/or limit the movement of handle 26 relative handle 28, such as, for example, hydraulic, semi-hydraulic and/or gearing systems.

[0042] In one particular embodiment according to the present disclosure, a ratchet is not included for selectively locking the jaw members 110 and 120 relative to one another and to maintain the pressure between jaw members 110 and 120. In this particular embodiment, the forceps 10 relies on the operating characteristics of the jaw members 110 and 120 and elongated tube 12 which, when moved into the closed position, will automatically maintain the two jaw members 110 and 120 engaged about tissue within the preferred pressure range to effectively seal tissue. As explained below with reference to FIGS. 1B, 1C and 2, the particular configuration of each jaw member 110 and 120 is designed to close upon distal advancement of the elongated tube 12 and also maintain pressure between the jaw members 110 and 120 until the handle 26 is re-actuated to open the jaw members 110 and 120 relative to one another. Thus, ratchet 30 in this instance is not necessary and may simply be utilized to guide handle 26 relative to handle 28.

[0043] Desirably, handle 28 includes a rotating assembly 23 for controlling the rotational movement of end effector assembly 100 about a longitudinal axis “X” defined along elongated shaft portion 12. In use, as rotating assembly 23 is rotated about the longitudinal “X” axis, end effector assembly 100 is correspondingly rotated about the longitudinal “X” axis. One such type of rotating assembly 23 is disclosed in commonly-owned U.S. patent application Ser. No. 10/472,295 entitled “VESSEL SEALER AND DIVIDER” and U.S. patent application Ser. No. 10/460,926 entitled “VESSEL SEALER AND DIVIDER FOR USE WITH SMALL TROCARS AND CANNULAS” the contents of both of these applications being incorporated by reference herein in their entirety.

[0044] As best seen in FIG. 1A, forceps 10 also includes an electrosurgical connector 62 which connects the forceps 10 to a source of electrosurgical energy, e.g., a generator (not shown) by virtue of a cable lead 60. Preferably, generators such as those sold by Valleylab—a division of Tyco Healthcare LP, located in Boulder, Colo. are used as a source of electrosurgical energy, e.g., FORCE EZ™ Electrosurgical Generator, FORCE FX™ Electrosurgical Generator, FORCE 1C™, FORCE 2™ Generator, SurgiStat™ II. One such system is described in commonly-owned U.S. Pat. No. 6,033,399 entitled “ELECTROSURGICAL GENERATOR WITH ADAPTIVE POWER CONTROL” the entire contents of which are hereby incorporated by reference herein. Other systems have been described in commonly-owned U.S. Pat. No. 6,187,003 entitled “BIPOLAR ELECTROSURGICAL INSTRUMENT FOR SEALING VESSELS”, U.S. patent application Ser. No. 10/427,832 entitled “METHOD AND SYSTEM FOR CONTROLLING OUTPUT OF RF MEDICAL GENERATOR” and U.S. patent application Ser. No. 10/626,390 entitled “VESSEL SEALING SYSTEM” the entire contents of all of which are also incorporated by reference herein.

[0045] With reference to FIGS. 1B, 1C and 2, end effector assembly 100 includes a first jaw member 110 and a second jaw member 120 which are movable from an open position to a closed position by movement of handle assembly 18 as described above. Jaw members 110 and 120 are generally symmetrical and include similar component features which cooperate to permit facile rotation about a pivot pin 119 to effect opening and closing of end effector assembly 100. As a result, and unless otherwise noted, only second jaw member 120 (shown in FIG. 2) and the operative features associated therewith are described in detail herein but as can be appreciated, many of these features apply to first jaw member 110 as well.

[0046] Jaw member 120 includes a jaw housing 124 having a flange 130 extending proximally therefrom. Flange 130 includes a pivot hole 121 formed therethrough for receiving pivot pin 119 (see FIG. 1B). Jaw housing 124 of jaw member 120 includes an electrically conductive tissue contacting surface 122 disposed on an inner facing surface thereof which aligns with a corresponding electrically conductive tissue contacting surface 112 of jaw member 110 when the jaw members 110 and 120 are moved to the closed position (see FIG. 1C). It is envisioned that the electrically conductive surface 122 may be integrally associated with the jaw housing 124 or engaged in some known mechanical fashion, e.g., by stamping, by overmolding, by overmolding a stamped plate, snap-fit, sonic welding and/or by overmolding a metal injection molded plate or other ways customary in the trade. Mounting the electrically conductive surface 122 to the jaw housing 124 in any one of these fashions is known to effectively reduce the thermal spread to adjacent tissue structures during and/or immediately following activation. The electrically conductive surface 122 may also include a pinch trim (not shown) which facilitates secure engagement of the electrically conductive surface 122 to the insulating housing 124 and also simplifies the overall manufacturing process.

[0047] As mentioned above, jaw member 120 includes a proximal flange 130 which is configured and dimensioned to cooperate with a proximal flange 140 of jaw member 110 to facilitate actuation of the jaw members 110 and 120 from the open to close positions when handle 26 is moved relative to fixed handle 28. More particularly and as best shown in FIG. 2, proximal flange 130 has a shaped profile which includes forward ski-slope like surfaces 136 and 137 and a rear inclined surface 134 which are designed to cooperate with the distal end 12b of the elongated shaft 12 to close, lock and maintain the jaw members 110 and 120 about the tissue within the predefined working pressure ranges for sealing tissue of about 3 kg/cm² to about 16 kg/cm². Flange 130 also includes a rear ski-slope like surface 138 which is designed to facilitate engagement of the distal end 12b of shaft 12 with the flange 130.

[0048] Jaw member 120 also includes a tail-like spring 135 which extends proximally from flange 130 and is designed to abuttingly engage an inner peripheral surface 13 of the distal end 12b elongated shaft 12. When jaw member 120 is mechanically engaged within surface 13 of the distal end 12b of shaft 12, spring 135 biases jaw member 120 in an open configuration prior to distal advancement of the elongated shaft 12.

[0049] As mentioned above, jaw member 110 includes similar elements to jaw member 120, i.e., electrically conductive surface 112, insulative jaw housing 114 and flange 140. Flange 140, likewise includes similar elements to flange 130, e.g., forward surfaces 146 and 147, inclined surface 144, rear slope 148 and tail-like spring 145.

[0050] Upon distal activation of the elongated shaft 12 in the direction of arrow “A” (See FIG. 1B), the rear slopes 138 and 148 of flanges 130 and 140 guide distal end 12b into the inclined surfaces 134, 144. The distal end 12b then cams the surfaces 134 and 144 against the inner peripheral surface 13 of the distal end 12b of shaft 12 thus forcing the jaw members 110 and 120 closer to one another in the direction of arrow “B” to engage tissue disposed therebetween. Once the jaw members 110 and 120 are fully cammed and closed about the tissue, continued forward movement of the shaft 12 forces the distal end 12b over the forward slope surfaces 136, 137 and 146, 147 which, in turn, lock the distal end 12b atop the flanges 130 and 140 thus maintaining consistent pressure between the two jaw members 110 and 120.

[0051] After the sealing process has been completed, the user simply de-actuates the actuator 20 (i.e., moves handle 26 relative to handle 28 in the opposite direction) which retracts the shaft 12 which, in turn, pulls the distal end 12b of the shaft 12 proximally over the forward slopes 137, 136 and 147, 146, respectively, to release the jaw members 110 and 120 from their locked orientation. Continued movement of the actuator 20 retracts the distal end 12b over inclined surfaces 134, 144 to allow the jaw members 110 and 120 to open relative to one another. As can be appreciated, the biasing action of the springs 135 and 145 force the jaw members 110 and 120 to open as the distal end 12b retracts along inclined surfaces 134 and 144. Proximal slopes 138 and 148 are preferably dimensioned to facilitate opening of the jaw members 110 and 120 with respect to one another as the distal end 12b of the shaft 12 is retracted to its proximal-most position.

[0052] Preferably, each spring 135, 145 is made from a durable, semi-resilient material which continually provides an adequate force to repeatedly bias the jaw members 110 and 120 to the open position relative to one another during periods of prolonged use. It is envisioned that the proximal sloped surfaces 138 and 148 may be dimensioned to cooperate with the springs 135 and 145 to facilitate opening of the jaw members 110 and 120 upon proximal movement of the shaft 12.

[0053] It is envisioned that proximal flanges 130 and 140 are made from a substantially rigid material which can withstand the necessary forces associated with sealing tissue. More particularly and as mentioned above, it is necessary to maintain a closure pressure of about 3 kg/cm² to about 16 kg/cm² between sealing surfaces 112 and 122 to effectively seal tissue during electrical activation. Thus, the cammed surfaces 134 and 144 are preferably made from a substantially durable material which can easily withstand these forces during operational periods of prolonged and repeated use. The proximal flanges 130 and 140 of the jaw members 110 and 120 cooperate with the distal end 12b of the elongated shaft 12 to provide and maintain a clamping pressure within the above working range. Moreover, the clamping pressure is maintained at a point proximal to the pivot 119 which removes the need to provide a pressure-assisting spring (or other mechanically-assisting element) within the handle 18. Once the shaft 12 translates over the forward slopes 136 and 146, the jaw members 110 and 120 lock in the closed position which eliminates the need to provide a ratchet mechanism in the handle to relieve clamping pressure during activation.

[0054] Alternatively, it is envisioned that the flange portions 130 and 140 may be made from a semi-compressible material having a specific spring rate (or compression rate) which cooperates with the distal end 12b of the shaft 12 to maintain the jaw members within the specified working range of 3 kgcm² to about 16 kg/cm².

[0055] It is envisioned that the jaw members 110 and 120 are energized to different potentials when the forceps 10 is configured for bipolar procedures and the same potential for monopolar procedures. With respect to the bipolar configuration, one of the jaw members, e.g., 110, may be adapted to connect to a first potential of an electrosurgical generator (not shown), while the other jaw member, e.g., may be adapted to connect to a second electrical potential to communicate bipolar energy through tissue held therebetween. It is contemplated that one or both of the jaw members 110 and 120 may be adapted to connect to the electrosurgical generator by electrical leads, one or more electrical conductors (e.g., an electrically conductive tube or elongated rod) or in other ways know in the trade. For example, commonly-owned U.S. patent application Ser. No. 10/179,863 entitled “VESSEL SEALER AND DIVIDER”, U.S. patent application Ser. No. 10/369,894 entitled “VESSEL SEALER AND DIVIDER AND METHOD FOR MAKING SAME” U.S. patent application Ser. No. 10/246,107 entitled “ENDOSCOPIC BIPOLAR ELECTROSURGICAL FORCEPS” and U.S. patent application Ser. No. 10/460,926 entitled “VESSEL SEALER AND DIVIDER FOR USE WITH SMALL TROCARS AND CANNULAS” include various electrical configurations for supplying the jaw members 110 and 120 with electrosurgical energy to treat tissue, the contents of all of which being hereby incorporated by reference herein.

[0056] It is also envisioned that the forceps 10 may be electrically or electro-mechanically configured for both monopolar activation and bipolar activation and may include circuitry and/or various switching arrangements disposed therein (not shown) for accomplishing this purpose. For example, the forceps may include circuitry which allows the surgeon to selectively apply either monopolar energy or bipolar energy depending upon a particular purpose. In this instance, circuitry is preferably included to prevent inadvertent monopolar activation without verification of a return pad (not shown) being in contact with the patient.

[0057] Desirably, when in the closed position, end effector assembly 100 defines a gap distance “G” between tissue contact surface 112 of first jaw member 110 and tissue contact surface 122 of second jaw member 120. Preferably, gap distance “G”, between opposing tissue contact surfaces 112, 122, ranges from about 0.001 inches to about 0.006 inches and, more preferably, between about 0.002 inches and about 0.003 inches.

[0058] Alternatively, one or a series of stop members (not shown) may be employed on the inner facing surfaces of the electrically conductive sealing surfaces 112 and 122 to define the gap “G” between the opposing jaw members 110 and 120. The stop member(s) may also be positioned proximal the pivot 119 or adjacent the electrically conductive surfaces 112 and 122 to define the gap “G”. A detailed discussion of these and other envisioned stop members as well as various manufacturing and assembling processes for attaching and/or affixing the stop members to the electrically conductive sealing surfaces are described in commonly assigned, co-pending U.S. application Ser. No. 10/471,818 entitled “VESSEL SEALER AND DIVIDER WITH NON-CONDUCTIVE STOP MEMBERS”, which is hereby incorporated by reference in its entirety herein.

[0059] It is envisioned that the closure of the jaw members 110 and 120 may be selectively controlled to allow delicate manipulation of fine tissue as need during the course of a particular operation. More particularly, distal translation of the shaft end 12b against flanges 130 and 140 may be regulated to control the relative closure distance between jaw members 110 and 120 and/or control the relative closure force between the jaw members 110 and 120. Moreover, the inclined surfaces 134 and 144 may be dimensioned to enhance the surgeon's level of tactical control during the tissue clamping. Further, moving the jaw members 110 and 120 from the open to closed orientations allows the jaw members 110 and 120 to act as dissectors for separating tissue and other structures during operating conditions.

[0060] Turning now to FIGS. 3A-4C, another embodiment of the present disclosure is shown which includes a forceps 300 having an end effector assembly 200 which includes first and second jaw members 210 and 220. The jaw members 210 and 220 are movable from an open position to a closed position by movement of handle assembly 18 as described above. Again, jaw members 210 and 220 are generally symmetrical and include similar component features as described above with respect to FIGS. 1A-2, namely, jaw housings 214 and 224 each having an electrically conductive tissue contacting surface 212 and 222, respectively, flanges 240 and 230, spring-like tails 245 and 235 and a pivot 219.

[0061] Each jaw member 110 and 120 includes an elongated channel 215a and 215b disposed therein which together (i.e., when the jaw members 110 and 120 are disposed in a closed orientation) define a knife channel 215 therebetween. Knife channel 215 is dimensioned to allow selective reciprocation of a knife or cutting edge 250 therethrough. Knife 250 includes an elongated slot 255 defined therein which is dimensioned to facilitate reciprocation of knife 250 within channel 215 and about pivot 219. It is also envisioned that pivot 219 and channel 215 may be appropriately dimensioned to guide knife 250 through channel 215 upon reciprocation thereof. In this particular configuration and as best illustrated in FIGS. 3B and 4B, the spring-like tails 235 and 245 of each jaw member 220 and 210, respectively, are preferably transversally offset relative to the knife 250 to facilitate selective reciprocation of the knife 250 through channel 215.

[0062] As best shown in FIG. 4C, a knife actuator 310 is included with the forceps 300 and is preferably integrally associated with handle assembly 18. Knife actuator 310 is selectively movable relative to handle assembly 18 from a first position wherein the knife 250 is retracted (i.e., proximally disposed relative to the tissue) to a second position wherein the knife 250 is distally extended through the knife channel 215. It is envisioned that the knife actuator 310 may include a safety mechanism which prevents movement of the knife 250 when the jaw members 110 and 120 are disposed in the open configuration. Commonly-owned U.S. patent application Ser. No. 10/369,894 entitled “VESSEL SEALER AND DIVIDER AND METHOD FOR MAKING SAME”, U.S. patent application Ser. No. 10/460,926 entitled “VESSEL SEALER AND DIVIDER FOR USE WITH SMALL TROCARS AND CANNULAS” and U.S. patent application Ser. No. 10/873,860 entitled “OPEN VESSEL SEALING INSTRUMENT WITH CUTTING MECHANISM AND DISTAL LOCKOUT” disclose several different types of safety mechanisms which may be associated with either the handle, housing or end effector assembly to accomplish this purpose, the contents of all of which being incorporated by reference herein in their entirety.

[0063] In one embodiment, it is contemplated that knife 250 includes a sharpened distal end 259 which allows the knife 250 to easily navigate through tissue structures disposed between the jaw members 110 and 120 upon activation of the knife actuator 310. Alternatively, the knife 250 may be substantially dull but the knife actuator 310 includes a large cutting force associated therewith such that selective activation of the knife actuator 310 forces the substantially dull blade through the tissue disposed between the jaw members 210 and 220. A spring or other mechanically advantageous element may be utilized to generate the forces necessary to repeatedly navigate the knife 250 through the tissue.

[0064] 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, while jaw members are shown as being substantially linear, including a substantially linear knife channel formed therein, it is envisioned that jaw members may be arcuate and include arcuate knife channel formed therein. As such, knife may be made from a semi-compliant material or may be multi-segmented to assure consistent, facile and accurate cutting and/or reciprocation through knife channel.

[0065] It is envisioned that the outer surface of the end effector assembly may include a nickel-based material, coating, stamping, metal injection molding which is designed to reduce adhesion between the end effector assembly (or components thereof) with the surrounding tissue during operation thereof. Moreover, it is also contemplated that the sealing surfaces of jaw members may be manufactured from one (or a combination of one or more) of the following materials: nickel-chrome, chromium nitride, MedCoat 2000 manufactured by The Electrolizing Corporation of OHIO, inconel 600 and tin-nickel. Sealing surfaces may also be coated with one or more of the above materials to achieve the same result, i.e., a “non-stick surface”. Preferably, the non-stick materials are of a class of materials that provide a smooth surface to prevent mechanical tooth adhesions. As can be appreciated, reducing the amount that the tissue “sticks” during sealing improves the overall efficacy of the instrument. Reference may be made to commonly assigned and owned U.S. patent application Ser. No. 10/284,562 entitled “VESSEL SEALING INSTRUMENT”, which is hereby incorporated by reference in its entirety herein, for a detailed discussion of the manufacture of the sealing surfaces.

[0066] Although many of the instruments described herein may be designed to seal and divide tissue through standard-sized cannula, one envisioned embodiment of the present disclosure includes a reduced-diameter shaft and end effector assembly which is specifically dimensioned to fit through a 5 mm cannula. As can be appreciated, utilizing a smaller-sized surgical instrument can be extremely beneficial to the patient (i.e., reduced trauma, healing and scar tissue).

[0067] Preferably, any of the instruments disclosed herein may be designed to be electrically couple to a foot switch (not shown) which allows the surgeon to selectively control the electrosurgical energy transferred to the tissue. In an alternate embodiment, instrument may be activated via a handswitch (not shown) located on the handle assembly. Reference may be made to the above-identified, commonly assigned U.S. patent application Ser. No. 10/460,926 for a detailed discussion of one example of a handswitch which may be utilized with the present disclosure.

[0068] It is also envisioned that knife may be energized and/or may be dimensioned as a so called “hot wire” which is selectively activateable by the user to divide the tissue after sealing. More particularly, a separate wire (not shown) may be mounted between the jaw members which is selectively movable and energizable upon activation of a handswitch or footswitch. The hot wire may be configured such that the user can move the wire in an inactivated or activated state which, as can be appreciated, would allow the user to cut the tissue on a reverse stroke if desired.

[0069] Although the subject instrument has been described with respect to preferred embodiments, it will be readily apparent to those having ordinary skill in the art to which it appertains that changes and modifications may be made thereto without departing from the spirit or scope of the subject instrument.

[0070] 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 particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.