A resectoscope having parts of conventional construction is disclosed in FIG. 1 as background for disclosure of the invention, and comprises a metallic tubular sheath 2 which provides a passageway through the human urethra to the area of visual and operative interest, and which has at its distal end a beak 4 which is formed of an electrically insulating material such as a synthetic plastic. At its proximate end the sheath is attached to a metallic block 6 at which there is a tube 8 with stopcock 10 for the introduction of clear irrigating fluid, and a thumb screw 12 for attaching the sheath's metallic socket to the block 6 which activates the cutting loop assembly and electrode in performing an operation.
Within the sheath are the telescope 14 and the cutting loop assembly 16. The telescope has an objective lens 18 at its distal end and an ocular lens (not shown) and eyepiece 20 at its proximal end. Fiberglass light conductors (not shown) extend through the telescope from an external connection 22 to the distal end for providing illumination. The telescope is supported and stabilized within the sheath by an elongated metallic tube 24 which partially or entirely surrounds the telescope in tight engagement. This tube is connected at its proximal end to the block 6 and in all resectoscopes prior to this invention its distal end is positioned proximal to the distal end of the telescope.
The cutting loop assembly 16 comprises, in one of its conventional forms, the elongated hollow stem 26 which extends along and beneath the telescope stem and from the distal end of which there protrude two parallel arms 28, 30 which are insulated wires positioned on opposite sides of the telescope adjacent its distal end and which are connected at their distal ends by a depending semi-circular bare wire cutting loop 32 which is activated by high frequency electrical energy and is used to resect pathological tissues and coagulate bleeding vessels. The stem 26 transmits the reciprocating movement of the working element to the cutting loop 32, and the wire in the stem and arms 28, 30 transmits high frequency electrical energy to the cutting loop 32. A tube 34 is connected to the distal end of the stem 26, and is positioned above the stem, and slidably surrounds the tube 24 in order to provide support to the cutting loop 16.
In performing an operative procedure using the resectoscope, electrical arcing between the un-insulated distal ends of the arms or the upper ends of the cutting loop and the adjacent distal end of the telescope often occurs when the cutting loop assembly is moved to rest position and the end of the telescope is touched by a piece of resected tissue which has adhered to the cutting loop or by the wire of a broken or deformed cutting loop. This arcing may damage the telescope, adversely affect the operative procedure and injure the surgeon. There have been many reports in the literature of eye injury to surgeons while performing transurethral operations, and it is well known that most surgeons have experienced electrical shocks and burning of the hand, cheek, nose and ears caused by arcing during performance of an operation with the use of a resectoscope. Among the methods suggested to correct this difficulty are (1) positioning the distal end of the telescope backward within the sheath beyond the position of optimum vision, (2) reducing the proximal movement of the cutting loop assembly in order to maintain the bare wire cutting loop at a safe distance from the telescope, and (3) extending the insulation of the spaced parallel arms of the cutting loop assembly over and beyond the junction of the arms and depending loop. None of these have been satisfactory as none have completely prevented arcing, and the object of my present invention has been to prevent arcing while at the same time maintaining the increased illumination and field of vision provided by modern telescopes of resectoscopes, without interference with the endoscopic field of vision and without decreasing the capacity of resection at each stroke of the cutting loop.