Abstract:
A bipolar electrosurgical instrument that is configured for use in MIS and other electrosurgical procedures. The instrument is constructed as a bipolar electrode comprising a bare wire as the active electrode spaced from a window below which is the return electrode. The bare wire electrode preferably is configured as a straight wire projecting laterally from the distal end or with straight or curved sections that extend rearwardly toward the window. When energized, a bipolar discharge is generated between the active and return electrodes.

Description:
RELATED APPLICATION 
     This application is a continuation-in-part of U.S. application, Ser. No. 09/728,382, filed Dec. 4, 2000, commonly owned, for “Bipolar Electrosurgical Handpiece For Treating Tissue”, of which the present application is a continuation-in-part. 
     This invention relates to a bipolar electrosurgical probe for performing arthroscopic surgery. 
    
    
     BACKGROUND OF THE INVENTION 
     Our prior application, Ser. No. 09/728,382, and the applications to which it is related, describe electrosurgical electrodes and handpieces for treating tissue in a surgical procedure commonly known as minimally invasive surgery (MIS). Among the features described and claimed in the prior application is an electrosurgical handpiece that can be used in MIS and reduces the danger of excessive heat causing possible patient harm. This is achieved in one embodiment by an electrosurgical handpiece that is bipolar in operation and that is configured for use in MIS. The bipolar operation confines the electrosurgical currents to a small active region between the active ends of the bipolar electrode and thus reduces the possibility that excessive heat will be developed that can damage patient tissue. Moreover, the position of the active region can be controlled to avoid patient tissue that may be more sensitive to excessive heat. In a preferred embodiment, the flexible end is achieved by weakening at the end the housing for the electrode, and providing a pull string or wire connected to the weakened housing end and with a mechanism at the opposite end for the surgeon to pull the string or wire to flex the housing end to the desired position. This feature allows the surgeon to position the active electrode end at the optimum location for treating, say, a herniated disk to remove undesired regions and to provide controlled heat to shrink the tissue during surgery. In one of the prior applications referred to in the referenced application, a suitable bipolar electrode is described, which comprises a pair of rounded electrodes with spaced flat sides separated by an insulating layer. The referenced application describes a bipolar probe comprising substantially hemispherically-shaped active electrode segments spaced apart by a thin insulator. 
     There is a need in the art for rigid electrodes, i.e., without a flexible end, for treating orthopedic ailments, such as for example joint ailments of the shoulder, knee and hip, especially in a minimally invasive surgery (MIS) environment, also referred to from time to time as arthroscopy. 
     SUMMARY OF THE INVENTION 
     The present invention is a continuation-in-part of the referenced prior application and hereby incorporates by reference the total contents of it and its four related prior applications, Ser. Nos. 09/303,839, 09/393,286, 09/425,313, and 09/483,994. The present invention describes and claims among other things a bipolar electrode comprising an active electrode at the distal end of a rigid non-flexible handpiece. Since the present application otherwise makes use of the same teachings of the prior applications, it was felt unnecessary to repeat in the body of this specification many of the details present in the contents of the prior application. The present description will be confined solely to the modifications in the handpiece or electrode which will still achieve the same benefits as with the constructions of the prior applications. For more details, the reader is directed to the prior applications. 
     The new handpiece end constructions of the present improvement uses the bipolar principle and are configured to provide more controlled distribution of the electrosurgical currents to the tissue to be modulated. By “modulation” is meant ablation, cutting, smoothing, volumetric shrinkage, coagulation, hemostasis or cauterization. 
     In a preferred embodiment, the active electrode is formed by a projecting wire preferably extending laterally, or laterally and backwardly and connected to a first terminal of the bipolar source. The second terminal is connected to a return or ground electrode that is located rearward of the active electrode and is positioned on or inside of the handpiece but electrically accessible to electrosurgical currents emanating from the active electrode. The current path may include an electrically-conductive or semi-conductive fluid positioned between the active and return electrodes. The conductive fluid can be provided by an introduced fluid such as saline solution, or by body fluids normally present adjacent the tissue being modulated. 
     In a first preferred embodiment, the wire extends laterally, allowing its use as a cutting wire electrode and also as an ablative electrode. In a second preferred embodiment, the wire extends in a loop having a front section, a side section, and a rear section. The three sections are differently shaped allowing them to be used for different surgical purposes. By “laterally” is meant that the active electrode extend at right angles or at an acute angle, such as 45°, with respect to the longitudinal axis of the handpiece or the electrode shaft. 
     The constructions of the invention will provide the same important benefits not only for MIS of herniated disks but also for other MIS arthroscopic procedures where controlled electrode position and/or controlled heat generation is of importance as described in the prior applications, as well as for general electrosurgical procedures where the volumetric reduction of tissue or ablation of tissue is desirable. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described the preferred embodiments of the invention, like reference numerals designating the same or similar elements. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a schematic view of a bipolar electrode according to the invention mounted in a handle or handpiece; 
     FIG. 2 is a perspective view of the active end of one form of bipolar electrode according to the invention; 
     FIG. 3 is a side view of the electrode of FIG. 2; 
     FIG. 4 is a side view similar to FIG. 3 of another bipolar electrode according to the invention; 
     FIG. 5 is a side view similar to FIG. 3 of still a further bipolar electrode according to the invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     The reader is directed to the referenced prior applications for a more detailed description of the prior applications which will assist in understanding the improvements offered by the present application. 
     In the present application, FIG. 1 is a schematic view of one form of electrosurgical instrument  10  in accordance with the invention. It comprises a rigid handle  12  with a conventional front end adapted to receive and hold rigidly the shank end (not shown) of an elongated support member  14  whose working end  16  is shown at the left. The support member  14  terminates in a distal end section  22  of reduced diameter. The handle  12  is electrically-insulating or if conductive covered with an electrically-insulating coating. Similarly, the shaft of the elongated support member  14  is also coated with an electrically-insulating coating, leaving bare the active electrode  20  at the working end  16  (See FIGS.  2  and  3 ). The support member  14  is long enough (see reference numeral  18 ) to extend through a conventional trocar or channel so that its working end  16  is exposed inside the patient. At the right end of the handle  12  is shown a cable  6  which contains two insulated wires for receiving bipolar electrosurgical currents from a conventional electrosurgical apparatus  8 . The active parts of the bipolar electrode comprise a metal wire electrode  20  and a return or ground electrode  26  which is accessible via a window  24  in the insulated support member  14 . As illustrated in FIG. 3, the cable  6  which extends through most of the handle and support member electrode comprises a first conductor  32  which is connected internally to the return electrode  26 , and a second conductor  30  which is connected internally to the wire  20  via a channel shown schematically at  21 . In this first embodiment, the active wire electrode  20  extends laterally of the longitudinal or long axis of the support member  14 . Specifically, and preferably, it extends at an angle of 90° to the long axis. In the structure shown, all exposed surfaces are electrically-insulating, except for the active wire  20  and the return  26  which is accessible via the window  24 . The end section  22  is made of electrically-insulating material. The support member body  14 , from the dividing line  36  is coated with an electrically-insulating coating  38 . As a result, part of the conductive ground  26  underlying the electrically-insulating coating  38  is not exposed to the outside, but, if a conductive or semi-conductive fluid is present, it will be able to access at least some of the conductive return underlying the coating  38 . The two wires  30 ,  32  are not only insulated from each other so that bipolar electrosurgical voltages can be applied between them, but they are also insulated from the support member  14 . In this description, by “axial” is meant parallel to the long axis of the support member  14  (horizontal in FIG.  3 ). By “lateral” is meant transverse to the long axis of the support member  14  (vertical in FIG.  3 ). “Lateral” is intended to include 90° for the embodiments of FIGS. 1-3, as well as an acute angle, such as 45°, for the embodiment of FIG.  5 . 
     Once the surgeon has positioned the working end  16  of the instrument with respect to the tissue to be operated on, he or she then activates the electrosurgical apparatus  8  causing a discharge of bipolar currents between the active wire electrode  20  and the return electrode  26  capable of causing excision of or ablation of or shrinkage of tissue or cauterization of a blood vessel in the usual way. The active wire is best used as a needle electrode or with its front side passing over the tissue. As with the embodiments of the prior application, the insulating coating on the support member  14  will prevent accidental touching of patient tissue by the electrode sides, so that the bipolar discharge is locallized to the spacing between the bare parts  20 ,  26 . The operation can take place in a wet field with a conductive or semi-conductive fluid completing the current path, or in a dry field where the electrosurgical currents from the active wire  20  seek out the closest return or ground which will be the electrode  26 . The surgeon positions the electrode  20  so as to touch or pass lightly over the tissue to be modulated as needed for the procedure being followed. 
     For example, a suitable metal for the electrodes is brass, tungsten or stainless steel. The spacing  34  between the two electrodes can vary between 0.35-0.55 inches, preferably about 0.47 inches. The spacing  34  also happens to be the distance between the wire electrode  20  and the nearer edge of the window  24 . The height  36  of the wire electrode  20  can vary between 0.06-0.1 inches, preferably about 0.08 inches. The width  38  of the insulated end can vary between 0.08-0.1 inches, preferably about 0.1 inches. The dimensions of the window  24  can vary between about 0.3-0.5×0.6-0.9 inches, preferably about 0.38×0.6 inches. The underlying conductive ground  26  will have about the same width dimension as the window, and extend in the length direction about 2-3 times longer than the window length. The depth of the conductive return or ground below the window surface is preferably about 0.023 inches. The overall length of the support member  14  typically will be about 3-8 inches. 
     FIGS. 1-3 illustrate a preferred embodiment of the invention in which the active wire electrode  20  is configured as a straight wire extending at right angles to the long axis of the support member  14 . Both the point, as well as the side of the wire, can be used by the surgeon. FIGS. 4 and 5 show two other preferred embodiments of the invention involving an active wire in which only sides of the wire can be used to modulate the tissue. The rest of the electrode remains the same, except that some of the spacings and dimensions change. 
     In FIG. 4, the active wire electrode  46  is configured as a leading first section that extends at right angles to the long axis of the support member  14 , a second mid-section that extends parallel to the long axis, and a trailing third section that also extends at right angles to the long axis of the support member  14 . The corresponding preferred dimensions are: the first section has a height  52  of 0.03-0.07 inches, preferably about 0.05 inches; the second section has a length  44  of 0.2-0.3 inches, preferably about 0.24 inches; the third section has a height the same as that of the first section and is spaced  45  from the window edge of 0.15-0.25 inches, preferably about 0.2 inches. In this case, the front side of the first and the top side of the second section can be used for tissue modulation. 
     In FIG. 5, the active wire electrode  46  is configured as a leading curved first section that extends out at right angles from a sloped end surface of the end section  22  and bends rearward to form a second straight mid-section that extends roughly parallel to the sloped end surface of the end section  22  and then bends rearward to form a trailing curved third section followed by a short straight section before it ends embedded in the end section  22 . The corresponding preferred dimensions are: 
     the end surface slopes to form an acute angle  72  of about 20-40°, preferably about 30°; the first section has a radius of curvature  76  of about 0.04-0.06 inches, preferably about 0.05 inches; the second section has a length  64  of 0.14-0.17 inches, preferably about 0.16 inches; the third section has a radius of curvature  74  approximately the same as that of the first section; and the fourth section has a length  66  of 0.03-0.07 inches, preferably about 0.05 inches. In this case, the front curved side of the first section, the outer straight side of the second section, the rear curved side of the third section, or the rearwardly-facing straight side of the fourth section can be used for tissue modulation. For example, the curved sections can serve to cut or shave or smooth tissue, the straight sections to shave or smooth tissue, the third curved section for point coagulation of bleeders, and the fourth straight section for cutting. Thus, this electrode configuration offers the most flexibility to the surgeon in his or her choice of modulating surfaces. Where the end of the fourth section embeds in the holder can be spaced about the same distance from the window edge as  45  of FIG.  2 . 
     Other usable mechanical or electrical structures following the teachings of the prior applications when combined with that of the present application will be appreciated by those skilled in this art. 
     The electrosurgical apparatus  8  preferably is an ultra high frequency (RF) radiosurgical energy source, which operates in the range of about 1.5-4 MHz. Studies have shown that the 1.5-4 MHz frequency range is the preferred RF energy to incise and coagulate tissue, generally modulate tissue, because tissue thermal necrosis is minimal and, when interfaced with the electrosurgical electrode of the invention, provides excellent cutting, smoothing and hemostasis especially for joint orthopedic procedures. An example of suitable electrosurgical apparatus is the Model SURGITRON Dual-Frequency electrosurgical unit manufactured by and available from Ellman International, Inc. of Hewlett, N.Y. 
     While the invention has been described in connection with preferred embodiments, it will be understood that modifications thereof within the principles outlined above will be evident to those skilled in the art and thus the invention is not limited to the preferred embodiments but is intended to encompass such modifications.