Abstract:
A novel cutter instrument uses radiofrequency (RF) electrosurgery and RF energy to achieve the desired cutting action with minimum of mechanical force, thereby reducing the risk of tissue damage due to excessive mechanical cutting action. Preferably, a cutter head of the instrument comprises an outer tube of electrically-insulating material with an aperture into which is telescoped an inner electrically-conductive tube. When the working or leading end of the latter is reciprocated across the aperture in the outer tube while RF electrosurgical currents are applied to the inner tube, the cutting action of tissue entering the aperture takes place primarily via the RF electrosurgical currents.

Description:
This invention relates to an electrosurgical cutter for carrying out various surgical procedures. In particular, it relates to an electrosurgical cutter instrument of the reciprocating type, and cutter heads for use with such electrosurgical cutters. 
     BACKGROUND OF THE INVENTION 
     U.S. Pat. No. 4,108,182, whose contents are hereby specifically incorporated by reference, describes a suction reciprocating cutter head especially useful for removing vitreous material under suction and for other surgical uses. The technique there described applies mechanical forces for shredding and cutting the vitreous into pieces while sucking the cut vitreous to disposal means. Another feature is the use of a protective sheath over the instrument part that provides the reciprocating action coupled with making the cutter head removable, with the result that the latter can be made disposable after use without the need to sterilize the protected instrument part that provides the reciprocating action. 
     A disadvantage of such an instrument is that, however small the applied mechanical force, there can always be a pulling or pressing force on the vitreous than can cause tearing damage on the vitreous. 
     SUMMARY OF THE INVENTION 
     An object of the invention is a cutting instrument that reduces the risk of tearing, spooling, or wind-up damage to the vitreous, as well as to other tissue in other surgical procedures. 
     Briefly stated, the novel cutter instrument in accordance with a feature of the invention uses radiofrequency (RF) electrosurgery and RF energy to achieve the desired cutting action with minimum mechanical force, thereby reducing the risk of tissue damage due to excessive mechanical cutting action. 
     In a preferred embodiment, the cutter head comprises an outer tube of electrically-insulating material with an aperture into which is telescoped an inner electrically-conductive tube. When the working or leading end of the latter is reciprocated across the aperture in the outer tube while RF electrosurgical currents are applied to the inner tube, the cutting action of tissue entering the aperture takes place primarily via the RF electrosurgical currents, and the inner tube functions mainly to uncover the aperture to allow tissue to enter and subsequently to cover the aperture to allow the suction to suction away the separated material. Thus, the leading edge of the inner tube, that in the prior art device must be sharpened to function properly, need not be given a particularly sharp edge in the instrument of the invention as it plays a much smaller role than in the prior art device. To provide RF electrosurgical currents at the inner electrically-conductive tube, an electrically-conductive connection is preferably made to a region of the inner tube remote from its leading edge or to an electrically-conductive part that is mechanically and electrically connected to the inner tube. The electrically-conductive connection is terminated by an external connector that can be connected to standard electrosurgical apparatus at a unipolar outlet. 
     Preferably, the electrosurgical cutter instrument of the invention works best with relatively high-frequency RF electrosurgical currents in excess of 1.5 MHz, preferably in the range of 1.5–4 MHz, as we believe that using electrosurgical currents in the MHz range causes relatively low tissue temperatures avoiding possible damage to adjacent tissue. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a perspective view of one form of electrosurgical cutter instrument of the reciprocating type in accordance with the invention shown connected to suitable electrosurgical apparatus; 
         FIG. 2  is a cross-sectional view along the longitudinal axis of the removable cutter head of the embodiment of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The reader is directed to the referenced prior patent which will assist in understanding the improvements offered by the present application. For the convenience of the reader, the same instrument assembly as described in the patent is used to illustrate the invention with the improvements of the present invention incorporated therein. The same reference numerals as used in the drawings of the references patent are also used for the convenience of the reader. The reader is directed to that patent for any further details of the overall assembly construction which are omitted here as unnecessary to a complete understanding of the present invention. More particularly, those skilled in the art will recognize that the invention is not limited to the specific construction of the reciprocating mechanism described in the patent, and other well-known reciprocating mechanisms in similar type instruments are deemed within the scope of the present invention. Moreover, the invention is not limited to cutter constructions in which the cutter head is removable and disposable. 
     Conventional electrosurgical apparatus can be used with instruments of the invention, but it is preferred to use low-power electrosurgical apparatus. Such apparatus is available from Ellman International of Hewlett, N.Y. as Model IEC50. The latter has the advantage that it generates RF electrosurgical currents in the MHz range, specifically, about 1.5–4 MHz, which we prefer for their less damaging effect on neighboring tissue. 
     In the preferred embodiment of a reciprocating cutter instrument according to the invention illustrated in  FIG. 1 , the instrument  10  comprises a drive housing  12  containing on its interior a power source and a conventional motor section. A switch  44  turns the motor on and off. The disposable, removable cutter head  16  when mounted engages a bayonet type connector to maintain the units assembled with the motor shaft engaging and rotating a cam  80  having a cam surface  82  in the cutter head  16 . 
     The RF cutting device  10  of the present invention contains all the parts such as battery, motor, switch, spring coil  86 , as described in the patent, but certain critical changes are necessary to implement the invention. These changes include the following. 
     The housing of the drive section  12 , which is generally cylindrical, is made of an electrically-insulating material, such as a suitable plastic. Also, the body  70  of the cutter head  16  also is made of an electrically-insulating material, such as a suitable plastic. In addition, the cam  80  is similarly made of an electrically-insulating material, such as a suitably hard plastic provided with a smooth inclined cam face  82  which contacts an electrically-conductive metal cam follower assembly  84  held against the cam face by an electrically-conductive coil spring  86 . Other changes are also necessary which will be explained below. 
     In this embodiment, the cam follower assembly  84  comprises a periphery which is hexagonal in shape slightly smaller than the hexagonal bore  73  of the body which permits axial movement of the cam follower assembly  84  but which prevents rotation. In this manner, well known in the art, rotary movement of the cam  80  is converted to reciprocating movement of the cam follower  84 . Bearing against the reverse side of follower  84  is the metal spring  86  which is seated against an electrically-conductive retaining ring  92 , for example, of metal, mounted in the bore  93  of the body  70 . The electrically-conductive retaining ring  92  has a wire  201  mechanically bound and soldered to the ring  92  on the side of the bore  93  and is thus electrically connected to the wire  201 . The wire  201 , which is insulated wire, extends through a tubular extension  202  to an external small electrical jack  203 , to which it may be connected by, for example, a quick banana connector (not shown) to the unipolar outlet of an electrosurgical generator  19  via the usual cable. 
     The generated RF energy from the electrosurgical generator  19  will go through the cable to the wire  201 , the conductive retaining ring  92 , the conductive coil spring  86 , and then the cam follower  84  which has a hollow cutting inner electrically-conductive tube blade  95 , for example, of metal, mounted in the bore  93  in the stem of the cam follower and reciprocates therewith. The inner electrically-conductive tube  95  is positioned within an outer stationary electrically-insulating, for example, of hard plastic, outer tube  94  fixed to the end of the nose body in a plastic cap member  97 . The inner metal cutting tube blade  95  and the outer plastic tube  94  may be of any configuration as long as they are matched for a close telescoping fit in the area where tissue cutting or separation takes place. As in the instrument described in the patent, a tubular extension  76  provides access to the inner bore  71 . The extension  76  in turn is coupled to a conduit  104  which terminates in a suction-generating device  102 . The inner tube  95  is also provided with an aperture  151  which provides access to the hollow inner tube interior. When suction is activated, the bore  71  is emptied as well as the hollow inner tube  95  when the tube is in its retracted position and the tube aperture  151  exposed. At the distal end of the structure, to the left in  FIG. 2 , the outer tube end is closed off  99  except for an aperture  98  which provides access for tissue into the distal end of the outer tube  94 . In the patent arrangement, when the inner tube  95  is reciprocated to its forward extended position, the open cutter end  101  of the inner tube  95  traverses the aperture  98  thereby slicing off or separating, and receiving in the hollow inner tube  95 , any tissue drawn by the suction through the aperture  98  into the interior of the hollow outer tube  94 . The suction then suctions away the tissue or any fluids present via the aperture  151  and the tubular extension  76  to the collecting means of the suction generator  102 . 
     In the inventive instrument, however, the tissue excision takes place mainly due to the RF energy supplied by the electrosurgical apparatus  19  which is present at the electrically-conductive end  101  of the inner tube  95 , substantially free of the mechanical pressing force of the prior art device. The return path for the RF energy is the usual large indifferent plate placed in contact with the patient. The aperture  98  in the outer plastic tube  94  may be of any preferred shape or size in the side wall near the end of the outer plastic tube  94  to permit entry of the tissue, especially, vitreous material, when suction is applied. 
     The relative lengths of the inner  95  and outer  94  tubes are such that the open end  101  of the inner tube  95 , which may or may not be sharpened, passes across the aperture  98  with each down stroke of the cam  80 . Each upstroke of the cam  80  uncovers the aperture  98  to permit entry of fresh vitreous or other tissue material. The upstroke is accomplished by the action of the conductive coil spring  86  which is sealed on the retaining ring  92  pushing against the force of the cam follower  84  and driving it towards the cam face  82 . The down stroke action of the blade  95  with RF energy at its working end  101  disintegrates the vitreous material between the tube end  101  of the inner tube  95  and the edge of the aperture  98 . It is not necessary to have a sharp cutting surface for the aperture, since the cutting is mainly by the RF energy, and very little, if any, pressing force is required. The cam follower assembly is mounted in the retainer ring  92  which abuts a circular seal  100  to prevent entry of foreign material from cavity  71  into the bore  52  of the cutter head. The reciprocating cutter tube blade  95  is also provided with the aperture  151  which allows the cut vitreous or tissue or fluids to be drawn upward through the inside diameter of the inner cutting tube  95  and out through the opening  151  into the suction chamber  71  and then into the syringe  102 . 
     The external fixed thin wall tube  94  projects from the end of the body  70  with the distal end  99  being formed into a smoothly blended non-conductive enclosure to prevent any unintended scattering of RF energy. 
     The conductive retaining ring  92  and seal  100  are mounted around the cam follower  84  to keep fluids from entering into the cavity housing the coupling means, thus preventing any leakage of vitreous material, fluid, blood or other materials past the shaft. The seal also prevents air from being drawn into the syringe via motor shaft leakage. The cam follower shaft  105  and ring  92  and seal  100  effectively seal off bore  71  to form the fluid receiving chamber  71 . It is important to confine the RF energy in the controlled area adjacent the distal end  101  of the electrically-conductive inner tube  95 . 
     It will be appreciated that, in the preferred embodiment, the outer parts of the structure are electrically insulating to prevent accidental electrical shock to the surgeon or patient and prevent inadvertent tissue damage upon contact. The electrically-conductive parts which carry the RF electrosurgical currents are all buried within the structure. In order to transmit the RF energy from the wire  201  to the inner tube  95 , the wire is electrically connected to the conductive retaining ring  92  which in operation is axially fixed. The electrical path is from the retaining ring  92  to the electrically-conductive spring  86  to the electrically-conductive cam follower  84  and thereby to the electrically-conductive inner tube  95  which is mounted to the cam follower  84  via the shaft  105 . Of those parts, only the retaining ring  92  is immovable and thus the preferred wire connecting member. Extending the wire  201  to connect to the reciprocating cam follower shaft  105  or directly to the inner tube  95  is also possible, but has the possible disadvantages of constant flexing of the wire end that may reduce its lifetime and exposure of the wire end to the withdrawn body fluids. However, this is less of a problem with a disposable cutter head which undergoes only one use before being thrown out. By also making the cam  80  of electrically-insulating material prevents the RF energy from flowing back to the power source, which may include control circuitry, that may be damaged by the RF energy. 
     The structure  77  at the right end of  FIG. 2  is for mounting of the cutter head  16  to the power assembly  12 . 
     The surgical procedure is as follows. Only the steps relative to the invention are recited in broad terms. The cutter  10  is connected in the usual way to the electrosurgical apparatus  19 . The surgeon inserts the working end  99  into the tissue to be excised and removed. The surgeon then activates the electrosurgical apparatus  19  choosing operating parameters such that relatively low power, low voltage settings of the apparatus are chosen. For the IEC50 instrument, which generates an output power of about 50 watts, a typical power setting of about 3–8 can be used. These values can be determined beforehand using test tissue, typically animal, and measuring the temperature due to resistive heating in the tissue surrounding the tip of the needle after a reasonable ON time of the instrument, say about 2–10 sec. The goal should be a low tissue temperature of about 50EC. The ON switch of the cutter is then depressed. The tissue inside the aperture  98  and subject to the RF energy from the reciprocating inner tube end  101  disintegrates and is suctioned out by the applied suction. The procedure is otherwise the same as that used with the electromechanical reciprocating cutter. No heating occurs around the electrically-insulating sections, because they are adequately electrically-insulated and no electrosurgical currents flow into the tissue from those sections. 
     The device described has particular utility for treating viscera disorders. 
     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.