a preferred embodiment of the bipolar electrosurgical instrument of the present invention is shown in fig1 . generally designated as 10 , the instrument is comprised of a tubular member 12 having a proximal end 14 and a distal end 16 . fitted into the distal end 16 is a cylindrical insulating plug 18 , preferably comprised of ceramic , or the like . mounted upon a distal end surface 20 of plug 18 is a surface electrode 22 , preferably of stainless steel , tungsten or tungsten alloy . with no limitation intended , and as better seen in fig2 electrode 22 preferably has a pentagon shaped cross - section , providing a knife edge 24 facing outward from the end 20 of insulating plug 18 . distal end surface 20 of plug 18 may preferably be generally circular or oval . a longitudinal bore 26 is drilled or otherwise formed lengthwise through plug 18 , communicating with the lumen of tubular member 12 . an actuator or push rod member 28 is preferably made of plastic or covered with a nonconductive material and extends through tubular member 12 . near the distal end of tubular member 12 , it is joined , as at junction 48 , with an &# 34 ; l &# 34 ;- shaped rigid support member or rod , such as stainless steel rod 30 , which is inserted through bore 26 . rod 30 further includes blade electrode 32 , preferably of stainless steel , tungsten or tungsten alloy , and which is disposed to operably cooperate with surface electrode 22 . the actuator member 28 extends through the length of the tubular member 12 and terminates at its proximal end in a thumb loop 34 . alternatively , the rigid support rod 30 may be comprised of a one - piece rod which extends the full length of member 12 and protrudes from its proximal end , as depicted in fig4 . a pair of rigid finger loops 36 and 38 are attached at the proximal end 14 of the tubular member 12 to provide a secure grip for moving actuator member 28 and concomitantly , stainless steel support rod 30 , reciprocally within the bore 26 , causing electrode 32 to move toward or away from electrode 22 on plug 18 . a pair of flexible conductive wires 40 and 42 are insulated from one another and extend through tubular member 12 . a conventional cord 44 , with electrical connector 46 on its free end , is electrically joined to the wires 40 and 42 at their proximal ends to facilitate their connection to an electrosurgical generator . the distal ends of wires 40 and 42 are electrically joined to electrodes 22 and 32 , respectively . specifically , conductive wire 40 extends the full length of tubular member 12 from cord 44 to surface electrode 22 . conductive wire 42 extends from cord 44 to a junction point 48 , where it is mechanically and electrically joined to steel rod 30 . when the thumb loop 34 and actuator member 28 are formed from plastic , there is no danger of shock to the surgeon . if a one - piece metal push rod is used , the thumb loop 34 should be appropriately insulated . it is suggested that cord 44 be supplied with rf voltage from an rf source 50 . control of this supply may be attained by use of a conventional on / off foot switch 52 , as known in the art . when the foot switch is depressed , a circuit is completed and electrical current is permitted to flow from the electrosurgical generator 50 and through electrodes 22 and 32 when tissue is captured therebetween . one skilled in the art will readily recognize that a finger - operated switch , such as switch 92 in fig4 mounted on housing 12 is equally useful to provide current in a controlled fashion to electrodes 22 and 32 . fig3 depicts a cross - sectional view showing an alternative tip arrangement for the present invention . in this embodiment , blade electrode 32 is mounted on a rigid support member 30 which is stationary . however , the insulating plug 54 is made moveable by virtue of being rigidly affixed to an actuator member such as stainless steel rod 56 . a thumb loop 58 is affixed at its proximal end and coated with a thin , insulative coating ( not shown ). thumb loop 58 is positioned in opposable relation to finger loops 36 and 38 on the tubular member 12 , as in the previous embodiment . thus , moving thumb loop 58 in a distal direction will simultaneously extend plug 54 beyond the distal end of member 12 and toward stationary blade electrode 32 . stationary blade electrode 32 may be mounted on support rod 30 , which is secured in retainer 60 comprised of a block of plastic . movement of thumb loop 58 brings cutting edge 24 toward or away from stationary electrode 32 . when radio frequency ( rf ) energy from source 62 is applied using foot switch 64 , a polyp or other tissue segment held between electrodes 22 and 32 will be severed . fig4 depicts an alternative embodiment featuring a variation of the plug shown in fig3 and eliminating the foot switch option . designated generally as 80 , this cylindrical plug can similarly be made to extend outward from the distal end of tubular member 12 by movement of a thumb switch . as better seen in fig5 the plug 80 features metal traces 82 and 84 inlaid in noncontacting and spiral relation upon the peripheral surface 86 . when energized , these traces 82 and 84 function as bipolar electrodes for effecting electrocoagulation of tissue and blood . additional flexible wire conductors 88 and 90 pass through the tubular member and supply rf voltage to these traces , which are preferably comprised of a tungsten alloy . to activate the electrocoagulating electrodes 82 and 84 , conductors 88 and 90 are joined to thumb switch 92 . when thumb switch 92 is advanced distally to lock on detent 93 , the circuit is completed and the traces 82 and 84 are energized . when the circuit is completed , rf voltage is supplied via cord 44 from rf source 62 . the electrodes 22 and 32 must be energized independently from traces 82 and 84 . push button 99 mounted on thumb switch 92 is connected to conductors 40 and 42 and cord 44 . it permits the user to exactly control the duration of cutting by the duration it is depressed . the plug 80 may also be extended or retracted . a rigid actuator member 94 is affixed to a sliding thumb switch 96 . movement in a distal direction extends the plug 80 , while proximal movement retracts it . slippage is prevented by detents 98 . fig6 and 8 depict alternative embodiments for the seductive electrodes 22 and 32 of fig1 - 4 . a pair of generally u - shaped electrodes either pass through or are secured within a plug member , such as plug 100 . in fig6 the legs of the moveable u - shaped electrode 102 are embedded and fixed within an oval - shaped plug 100 , better seen in fig7 . they are securely held in place with , for example , beads of potting material 104 and 106 . stationary electrode 108 is dimensioned to be slightly larger in total surface area than electrode 102 . bores have been drilled through the insulating plug 100 to receive legs 110 and 112 of electrode 108 . these legs 110 , 112 extend into tubular member 12 and are secured in a pair of nonconductive retainers 114 and 116 . a rigid actuator means , as depicted in fig3 includes a stainless steel rod 118 , which extends through tubular member 12 to a thumb loop , as in previously described embodiments . the rod 118 is securely affixed at its distal end to plug 100 so translational movement of the thumb loop causes the end plug carrying electrode 102 to be displaced along the longitudinal axis of tubular member 12 toward or away from fixed electrode 108 . the converse is depicted by plug 120 in fig8 . the legs of moveable electrode 122 are embedded within plug 120 and secured with potting material 124 and 126 . fixed electrode 128 is disposed coaxially with moveable electrode 122 and has legs 130 and 132 which extend through bores 134 and 136 in plug 120 to retainers 138 and 140 inside tubular member 12 . plug 120 is similarly affixed to an actuator means , here depicted as stainless steel rod 142 , which extends to a thumb loop ( not shown ), as in previous embodiments . it is well within the contemplation of one skilled in the art that although the electrodes in fig6 and 8 are depicted as being somewhat rectangular in shape , electrodes 102 , 108 , 122 and 128 may be dimensioned in various curved configurations as well . an example is provided in fig9 wherein electrodes 150 and 152 feature distal curves to provide a scoop - like excision in tissue . furthermore , as better seen in fig1 , plug 120 may have a circular distal surface . one skilled in the art will appreciate that many variations in electrode configuration are possible , but such variations do not depart from the spirit of the present invention . for example , fig1 and 12 show a variant of the embodiment of fig1 , in which the electrode tips 160 and 162 have been flattened into a plane perpendicular to that of the longitudinal axis of the tubular member 12 . in operation , a surgeon grasps tubular member 12 at its proximal end , inserting his thumb and fingers in loops 34 , 36 and 38 . the distal portion of the electrosurgical instrument is then advanced through a laparoscopic trocar or endoscope and the distal end carrying or otherwise supporting the bipolar electrodes is positioned near the tissue to be removed . by moving thumb loop 34 toward tubular member 12 , electrode 30 in fig1 is moved distally from electrode 22 . in the embodiment of fig8 electrode 122 is moved distally from electrode 128 . in the embodiments of fig3 and 5 , the thumb loop 34 , 54 is pulled proximally . this draws the plug ( 54 , 86 or 100 ) proximally and away from the electrode ( 32 or 108 ). in all embodiments , movement of the thumb loop , as herein described , provides a gap into which the tissue to be excised is inserted . upon reciprocal movement and simultaneous application of radio frequency energy , the tissue is electrocauterized and severed . to provide enhanced electrocoagulation , traces such as depicted in fig4 may be included on all embodiments . 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 equipment details and operating procedures , can be accomplished without departing from the scope of the invention itself .
an electrosurgical instrument for the removal of tissue polyps and the like is disclosed . it features a bipolar pair of conductive electrodes for the cutting of tissue in which at least one electrode is moveable in relation to the other . these electrodes are mounted relative to an insulating plug , which is secured at the distal end of a tubular member . pressure exerted on a thumb loop shifts the position of one electrode relative to the other . upon application of rf voltage , the distance at which the electrodes are placed controls the amount of arcing which will occur between electrodes , when placed within a proper range . the electrodes are supplied with power from a standard rf energy source , controlled from a foot or hand switch . the insulating plug may further include metal traces disposed on the peripheral surface . when energized , these traces function as a bipolar pair of electrodes for effecting electrocoagulation of tissue and blood .