Abstract:
A bipolar electrosurgical hook probe includes an end effector that includes first and second electrodes placed in parallel, closely-spaced relationship, each being of a relatively large surface area and a conductive reciprocally movable hook member that is movable into and out of a space between the first and second electrodes. A switch mechanism is provided by which an RF current can alternatively be made to flow between the first and second electrodes during electrocoagulation and from the hook electrode to each of the first and second electrodes when the instrument is operating in its cut mode.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional patent Application Nos. 60/314,650, filed Aug. 27, 2001 and 60/382,439, filed May 22, 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     I. Field of the Invention 
     This invention relates generally to electrosurgical instruments, and more particularly to an improved, bipolar, hook-probe for use in endoscopic surgery to provide enhanced cutting and coagulation capability over existing hook-probe instruments. 
     II. Discussion of the Prior Art 
     In the course of minimally invasive procedures, electrosurgery is often employed to effect cutting and coagulation or cauterization of tissue structures. The electrosurgical instruments employed have one or more electrodes adapted to be energized by RF currents. In so-called monopolar systems, the current passes from the instrument, through the tissue to be cut or coagulated to a body plate type return electrode located remote from the surgical site. Since the electrical currents tend to follow a path of least resistance from the instrument to the return electrode, the path is somewhat unpredictable and it has led to burns at unintended locations. 
     In the case of bipolar instruments, the active electrode and the associated return electrode are disposed in close proximity to one another on the instrument itself so that there is less likelihood of current flow to tissues other than intended tissue structures being operated upon. Bipolar electrosurgery is considered by most as a safer procedure. 
     In the Fleenor et al. U.S. Pat. No. 5,484,435, there is described a bipolar electrosurgical instrument intended for use in minimally invasive surgical procedures for both cutting and coagulating tissue, thus obviating the need for an instrument exchange where separate instruments as required for the cutting and coagulating functions. The instrument described in the &#39;435 patent comprises a handle  98  disposed at one end of an elongated tubular barrel  96  having as one electrode a hook  90  in the form of a bent uninsulated wire and a one-piece return electrode  92  that is somewhat hemispherical in shape that projects outwardly from the distal end of the barrel and which has a slot formed therein for receiving the hook electrode therethrough. The walls of the slot are insulated so as to prevent short-circuiting with the hook member electrode but the portions of the electrode  92  on both sides of the slot are not insulated from each other. A lever assembly  98  on the handle, which when manipulated, allows the active hook electrode  90  to be extended and retracted relative to the fixed return electrode  92 . In use, the active hook electrode is made to frictionally engage or slightly puncture target tissue to grip it. Then, by manipulating the lever  98  on the handle, the tissue can be drawn proximally to engage the return electrode. The electrosurgical generator is then activated to achieve cutting or coagulation. 
     The device of the &#39;435 patent achieves acceptable levels of cutting because of the high current density present due to the small size and shape of the active electrode. However, coagulation with that instrument leaves much to be desired, given the small electrode surface area of the active electrode compared to that of the one-piece return electrode  92 . 
     Bipolar coagulation devices require equal electrode surface area or a ratio of 1:1 for optimum results. Bipolar cut devices require a 4:1 or greater return electrode to active electrode ratio for effective precision cutting. Prior art bipolar devices have tended to be either good coagulators or good cutters, but not both. 
     The present invention is deemed to be a substantial improvement over the prior art as represented by the Fleenor et al. &#39;435 patent. The device constructed in accordance with the present invention provides a hook probe that not only effectively cuts target tissue, but it also provides superior coagulation. 
     The Rydell U.S. Pat. No. 5,282,799 in the embodiment illustrated in FIG. 9 discloses an arrangement in which a pair of loop electrodes  28  and  30  are mounted on the distal end of a reciprocally movable control rod  60  that can be shifted longitudinally, via a thumb slide  224  so as to be extended from the distal tip of the instrument or retracted fully within the distal tip of the instrument. Also present on the insulating distal tip member  70  of the instrument are electrode surfaces  71  and  73 . A push-button  216  moves longitudinally with the control rod so as to overlay a first dome switch  210  or a second dome switch  212 . When the loop electrodes  28  and  30  are in their distalmost position projecting from the distal end of the instrument, the push-button  216  overlays the dome switch  210 . Thus, when the push-button  216  is depressed, a cutting potential is applied between the electrodes  28  and  30 . When the loop electrodes  28  and  30  are retracted by shifting the thumb slot in the proximal direction, the push-button  216  overlays the dome switch  212  so when it is depressed, a coagulating voltage is applied to the electrodes. Since the loop electrodes are retracted into a recess in the distal tip, they are not exposed to tissue. Only tissue bridging the surface contacts  71  and  73  will have a coagulating current flowing through it. 
     In this design, when electrosurgical cutting is involved, the same cutting voltage that is applied to the loop electrodes  28  and  30  is also present between the surface-mounted coagulating electrodes  71  and  73 . The surgeon must, therefore, exercise increased caution to avoid inadvertent contact of non-target tissue with the surface electrodes as the cutting operation is taken place. 
     The Rydell U.S. Pat. No. 5,891,141 describes an electrosurgical instrument for cutting and coagulating tubular tissue structures, such as vein and arterial tissue, by grasping the tissue between a pair of spaced-apart electrodes that when energized by RF energy coagulates the portion of the tissue structure contained between the two electrodes. Once desiccated, a thumb switch is manipulated to cause a cutting blade to mechanically cut through the desiccated tissue. 
     The Roos U.S. Pat. No. 5,269,780 describes an electrosurgical instrument designed to both cut and coagulate tissue. It includes a handle having a pair of stationary L-shaped hook electrodes  22  and  23  projecting from a distal end of the handle in parallel, spaced-apart relation. These electrodes function to coagulate tissue and once coagulated, a cutting electrode  21  is made to descend into the gap between the two stationary electrodes while a cutting voltage is applied between it and the two stationary coagulating electrodes which function as a neutral. No provision is made for retracting any of electrodes  21 - 23  into the handle member. 
     SUMMARY OF THE INVENTION 
     The foregoing objects and advantages of the present invention are provided by designing a bipolar electrosurgical cutting and coagulating probe that has an elongated, tubular barrel with a proximal end, a distal end and a lumen extending between the two. A handle member is affixed to the proximal end of the barrel and an end effector is affixed to its distal end. The end effector in accordance with the present invention includes first and second electrodes that are placed in parallel, closely-spaced, non-contacting relationship where each is of a relatively large surface area. A conductive, reciprocally movable hook member is operatively coupled to a mechanism on the handle member so that manipulation of the mechanism causes the hook member to be movable in and out of the space separating the first and second electrodes from one another. The hook member has a relatively small surface area compared to the combined surface area of the first and second electrodes. A plurality of elongated conductors extends through the handle and into the lumen of the barrel, the first being electrically connected to the first electrode, the second to the second electrode and the third to the hook member electrode. In its cut mode, an appropriate RF voltage is applied between the hook electrode and the first and second electrodes as tissue comes into contact with all three electrodes or is gripped by the hook drawn toward and against the first and second electrodes which together function as the return electrode for the bipolar instrument. When operating in a coagulation mode, however, the RF voltage is only applied between the first and second electrodes. The hook is not energized. Because the first and second electrodes are of generally equal surface area, coagulation occurs over the entire active surfaces of the first and second electrodes, providing appreciably greater margins than result from the Fleenor-type instrument, 
     There are, of course, additional features of the invention that will be described hereinafter which will form the subject matter of the appended claims. Those skilled in the art will appreciate that the preferred embodiments may readily be used as a basis for designing other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions since they do not depart from the spirit and scope of the present invention. The foregoing and other features and other advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial side elevation view of the bipolar electrosurgical hook probe comprising a preferred embodiment of the invention; 
     FIG. 2A is a partial view of the distal end portion of the instrument of FIG. 1 with the hook member extended; 
     FIG. 2B is a partial view of the distal end portion of the instrument; and 
     FIG. 3 illustrates a switching circuit for selecting either the cut mode or the coagulation mode of operation. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring first to FIG. 1, there is indicated generally by numeral  10  a bipolar electrosurgical hook probe instrument embodying the present invention. It is seen to comprise an elongated tubular barrel  12  whose outside diameter is dimensioned so as to pass through a viewing endoscope or a trocar when used in a minimally invasive surgical procedure. The barrel  12  has a proximal end  14  and a distal end  16  along with a lumen  18  extending therebetween. The tubular barrel  12  may comprise an extruded metal tube of a predetermined length having an electrically insulating coating on its exterior surface. Alternatively, the tubular barrel  12  may be formed from a suitable plastic in an extrusion operation. 
     Affixed to the proximal end  14  of the tubular barrel  12  is a handle member  20  that is generally longitudinally aligned with the barrel. The handle  20  is ergonomically designed to be grasped with the curved bottom surface  22  lying generally across the joints between the metacarpals and proximal phalanges of a surgeon&#39;s hand and with the surgeon&#39;s thumb resting on a slide mechanism  24 . The handle  20  is preferably molded from a suitable medical-grade plastic and formed interiorly therein is a channel through which electrical conductors  26 ,  28  and  30  may pass. Affixed to the proximal end of the conductors  26 ,  28  and  30  are plugs  32 ,  34  and  36 , which are adapted to mate with jacks (not shown) on a standard electrosurgical generator or mode control switch (also not shown). 
     Affixed to the distal end  16  of the tubular barrel  12  is an end effector assembly indicated generally by numeral  38 . As can be seen from FIG.  1  and from the enlarged view of the distal end portion of the instrument illustrated in FIGS. 2A and 2B, the end effector comprises first and second hemispherical shaped electrodes  40  and  42  which are disposed in parallel, closely spaced but non-contacting relationship to one another and which are fixedly secured to the distal end  16  of the barrel  12 . The exterior surface of the electrodes comprises conductive metal. The electrodes may be solid metal or may comprise a ceramic substrate on which a conductive metal layer has been deposited. The walls  44  and  46  that define a slot  48  have an insulating layer  50  thereon. Without limitation, the insulating layers  50  may be a ceramic. 
     The conductor  26  extends through the handle  20  and through the lumen  18  of the barrel to electrically connect to the electrode  42 . Likewise, the conductor  30  also extends through the handle  20  and through the lumen  18  and connects to the electrode  40 . It should be recognized that the barrel itself can be metal and can serve as a medium for coupling a voltage to one or the other of electrodes  40  and  42 . 
     Disposed in the slot  48  is the shank portion  52  of a conductive hook-shaped member electrode  54 . The distal end portion of the shank  52  is bent to form a hook portion  56  as can best be seen in the view of FIG.  1 . The conductor forming the hook electrode  54  extends through the lumen of the tubular barrel  12  and partway through the handle  20  where it is coupled to an ear  56  affixed to the thumb slide  24 . Thus, by shifting the thumb slide  24  forward and rearward, the hook portion  57  of the electrode  54  can be made to project from or withdraw into the slot  48 . The insulating layers  50  prevent electrical shorting between the hook electrode  54  and the return electrodes  40  and  42 . The conductor  28  electrically connects to the shank  52  of the hook. 
     FIG. 3 illustrates a switching circuit for controlling the mode of operation of the bipolar electrosurgical hook probe comprising a preferred embodiment of the present invention. The switching circuit of FIG. 3 may be resident in the electrosurgical generator used with the instrument or it may be located within the handle  20  of the instrument. Alternatively, the switching arrangement may be physically located in an adapter box disposed between the instrument leads  26 ,  28  and  30  and a conventional electrosurgical generator. 
     In the view of FIG. 3, the electrosurgical generator is identified by numeral  58  and it is connected through an on/off switch  60  to a junction point  62  to which the conductor  26  joined to electrode  42  connects. The junction  62  is connected to the pole  64  of a single-pole, double-throw switch having associated with it contacts  68  and  70 . Contact  70  is connected to conductor  30  which leads to the electrode  40 . The RF generator  58  is also connected by a conductor  72  to a pole  74  of a single-pole, single-throw switch having a contact  76  that is coupled by the conductor  28  to the conductive hook  54 . 
     The switch  60  may be physically located so as to be operable by the surgeon&#39;s foot and, when the mode switches are in the coagulation mode, the RF voltage from the generator  58  is applied between the first and second electrodes  40  and  42 , with the hook electrode  54  being open circuited. When the mode switches are placed in the cut mode, the voltage from the generator  58  will be applied between the electrodes  40  and  42  together and the hook electrode  54 . 
     When it is desired to use the hook probe  10  to cut through tissue such as a tubular blood vessel or the like, the surgeon loops the hook  56  about the tubular vessel and, by using the thumb slide, draws it against electrodes  40  and  42 . The surgeon then applies a first voltage, via switch  60  and the mode selection switches S 1  and S 2  between the hook electrode  54  and the return electrode, which, as explained above, during cutting, comprise both the first electrode  40  and the second electrode  42  which are maintained at the same potential. Because of the small surface area of the hook electrode compared to the combined surface area of electrodes  40  and  42 , a high current density is developed proximate the hook to effect cutting through tissue. 
     Where it is desired to cut through connective tissue, the hook can be retracted to a point where only the bottom of the hook protrudes out from the slot  48 . By applying a cut voltage to the hook electrode and using the coagulation electrodes as a return, the instrument&#39;s end can be swept over the tissue causing it to be transected. 
     To effect coagulation, the hook electrode may be retracted fully within the slot  48  and a potential applied by the generator  58  through switch  60  and switches S 1  and S 2  between the first electrode  40  and the second electrode  42 . As the two electrodes are brought into engagement with the bleeding tissue, the RF current produces sufficient heating over the areas defined by the electrodes  40  and  42  to produce coagulation. In that the electrodes  40  and  42  are of generally equal surface area, either one can function as the active electrode while the other serves as the return electrode. The hook can also be used to catch and draw target tissue into contact with the electrodes  40  and  42  to effect coagulation where the hook remains electrically passive. To cut through the coagulated tissue, then, a cut voltage is applied to the hook electrode while the electrodes  40 - 42  act as a common return. 
     The coagulation performed by the instrument of the present invention is significantly more satisfactory than what can be achieved when a hook electrode is used as the active electrode and the return electrode comprises a single slotted hemispherical member as in the Fleenor et al. &#39;435 patent. 
     This invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required. However, it is to be understood that the invention can be carried out by specifically different equipment and devices, and that various modifications, both as to the equipment and operating procedures, can be accomplished without departing from the scope of the invention itself.