Abstract:
In an embodiment, a method for cutting tissue comprising inserting at least a portion of a medical instrument into a body; and cutting tissue of the body with first and second blades of the medical instrument, wherein the first blade includes: a first member having a shearing surface; an electrically insulative member supported by the first member; and a conductive member adjacent to the electrically insulative member and electrically insulated from the first member by the electrically insulative member.

Description:
This is a continuation of application Ser. No. 10/626,599, filed Jul. 25, 2003, now U.S. Pat. No. 7,063,697, which is a continuation of application Ser. No. 09/177,502, filed Oct. 23, 1998, now U.S. Pat. No. 8,114,074, which is a continuation of application Ser. No. 08/354,992, filed Dec. 13, 1994, abandoned, all of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to endoscopic surgical instruments. More particularly, the invention relates to an endoscopic surgical instrument having end effectors made out of a combination of conductive and non-conductive materials. The invention has particular use with respect to bipolar endoscopic cautery. For purposes herein, the term “endoscopic instruments” is to be understood in its broadest sense to include laparoscopic, arthroscopic, and neurological instruments, as well as instruments which are inserted through an endoscope. 
     2. State of the Art 
     Endoscopic surgery is widely practiced throughout the world today and its acceptance is growing rapidly. In general, endoscopic/laparoscopic surgery involves one or more incisions made by trocars where trocar tubes are left in place so that endoscopic surgical tools may be inserted through the tubes. A camera, magnifying lens, or other optical instrument is often inserted through one trocar tube, while a cutter, dissector, or other surgical instrument is inserted through the same or another trocar tube for purposes of manipulating and/or cutting the internal organ. Sometimes it is desirable to have several trocar tubes in place at once in order to receive several surgical instruments. In this manner, organ or tissue may be grasped with one surgical instrument, and simultaneously may be cut with another surgical instrument; all under view of the surgeon via the optical instrument in place in the trocar tube. 
     Various types of endoscopic surgical instruments are known in the art. These instruments generally comprise a slender tube containing a push rod which is axially movable within the tube by means of a handle or trigger-like actuating means. An end effector is provided at the distal end of the tube and is coupled to the push rod by means of a clevis so that axial movement of the push rod is translated to rotational or pivotal movement of the end effector. End effectors may take the form of scissors, grippers, cutting jaws, forceps, and the like. Because of their very small size and the requirements of strength and/or sharpness, end effectors are difficult to manufacture and are typically formed of forged stainless steel. As such, they form an expensive portion of the endoscopic instrument. 
     Modern endoscopic procedures often involve the use of electrocautery, as the control of bleeding by coagulation during surgery is critical both in terms of limiting loss of blood and in permitting a clear viewing of the surgical site. As used herein, cautery, electrocautery, and coagulation are used interchangeably. Several types of electrocautery devices for use in endoscopic surgery are described in the prior art. Monopolar electrosurgical instruments employ the instrument as an electrode, with a large electrode plate beneath and in contact with the patient serving as the second electrode. High frequency voltage spikes are passed through the instrument to the electrode (i.e., end effector) of the endoscopic instrument to cause an arcing between the instrument and the proximate tissue of the patient. The current thereby generated continues through the patient to the large electrode plate beneath the patient. Monopolar cautery has the disadvantage that the current flows completely through the patient. Because control of the current path through the body is not possible, damage can occur to tissue both near and at some distance from the surgical site. In addition, it is has been observed that monopolar cautery can result in excessive tissue damage due to the arcing between the end effector and the tissue. 
     In order to overcome the problems associated with monopolar cautery instruments, bipolar instruments have been introduced. In bipolar electrosurgical instruments, two electrodes which are closely spaced together are utilized to contact the tissue. Typically, one end effector acts as the first electrode, and the other end effector acts as the second electrode, with the end effectors being electrically isolated from each other and each having a separate current path back through to the handle of the instrument. Thus, in a bipolar instrument, the current flow is from one end effector electrode, through the tissue to be cauterized, to the other end effector electrode. 
     Various endoscopic instruments with cautery capability are known in the art. U.S. Pat. No. 4,418,692 to Guay, for example, discloses a device for use in laparoscopic tubal cauterization for blocking the Fallopian tubes of a patient. The device comprises a substantially tubular body member having a spring-biased piston slidably mounted therein. A pair of electrodes (either monopolar or bipolar) are disposed to grasp living tissue when the piston is in a first position biased by the spring and to release the tissue when a button is pressed which moves the piston into a second position. The device includes a circuit breaker which interrupts current flowing to the electrodes when the piston is in the second position. When the electrodes grasp the tissue, however, current is supplied to the entire surface of the electrode, that is, both the grasping surface and the outer non-grasping surface. 
     Another electrosurgical instrument for use in combination with an endoscope is disclosed in U.S. Pat. No. 5,007,908 to Rydell for “Electrosurgical Instrument Having Needle Cutting Electrode and Spot-Coag Electrode”. Rydell&#39;s device includes an elongated flexible tubular member with a plurality of lumens. The distal end of the tubular member is provided with a bullet shaped ceramic tip covered with a conductive layer and having an opening coupled to a first one of the lumens. The conductive layer is coupled to a conductor which extends through a second one of the lumens to an electrical source. A second conductor, also coupled to the electrical source is slidable through the first lumen by a plunger. The two electrodes form a bipolar pair. In a second embodiment, the conductive layer on the ceramic tip is split by an insulating gap and both halves of the tip form a bipolar pair of electrodes. As with the Guay device, above, substantially the entire distal surface of Rydell&#39;s device serves as an electrode when energized. 
     Several hemostatic bipolar electrosurgical scissors have also been described. U.S. Pat. No. 3,651,811 to Hildebrandt describes a bipolar electrosurgical scissors having opposing cutting blades forming active electrodes. The described scissors enables a surgeon to sequentially coagulate the blood vessels contained in the tissue and then to mechanically sever the tissue with the scissor blades. In particular, with the described bipolar electrosurgical scissors, the surgeon must first grasp the tissue with the scissor blades, energize the electrodes to cause hemostasis, de-energize the electrodes, and then close the scissor blades to sever the tissue mechanically. The scissors are then repositioned for another cut accomplished in the same manner. With the bipolar electrosurgical scissors of Hildebrandt, the surgeon cannot maintain the electrodes in a continuously energized state because the power supply would be shorted out and/or the blades damaged if the blades are permitted to contact each other while energized. 
     The disadvantages of the bipolar scissors of Hildebrandt are overcome by the disclosure in U.S. Pat. Nos. 5,324,289 and 5,330,471 to Eggers. In its preferred embodiment, the bipolar electrosurgical scissors of Eggers comprise a pair of metal scissor blades which are provided with an electrically insulating material interposed between the shearing surfaces of the blades so that when the scissor blades are closed, the metal of one blade never touches the metal of the other blade; i.e., the insulating material provides the cutting edge and the shearing surface. With the arrangement provided by Eggers, a cautery current will pass from the top back edge of the bottom metal blade through the tissue which is to be cut and to the bottom back edge of the top metal blade directly in advance of the cutting action. As the scissors are gradually closed, the hemostasis preferentially occurs at a location just in advance of the cutting point which itself moves distally along the insulated cutting edges of the blades in order to sever the hemostatically heated tissue. With this arrangement, the scissors may be maintained in a continuously energized state while performing the cutting. The Eggers patent describes various alternative embodiments of the bipolar scissors, including the use of metal blades with only one blade being insulated on its shearing surface, and the use of insulating blades with back surfaces coated with metal. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide a pair of scissor blades for a bipolar cauterizing surgical scissors which provide a metal on metal cutting/shearing action. 
     It is another object of the invention to provide a pair of scissor blades for a bipolar cauterizing surgical scissors which have shearing surfaces that are insulated from cautery surfaces. 
     It is also an object of the invention to provide an endoscopic bipolar cauterizing scissors which provides a metal on metal cutting action and which may be either curved or flat. 
     In accord with the objects of the invention, the scissor blades of the present invention are comprised of an electrically conductive electrode, an electrically insulating material, and a metal shearing surface which is electrically insulated and physically spaced from the electrode by the insulating material which is disposed therebetween. The scissor blades, for example, may comprise but are not limited to a composite assembly of an electrode layer, an insulating layer, and a metal shearing surface layer. In the presently preferred embodiment, the electrode layer is a metal blade which is typically constructed from stainless steel, while the insulating layer is a ceramic which is deposited, bonded, or otherwise fixed on the metal blade, and the metal shearing surface layer which also provides the cutting edge is a metal (e.g., copper, gold, stainless steel etc.) which is metalized, deposited, sputtered, plated, bonded, or otherwise fixed onto the ceramic. In a second embodiment, the insulating layer is a ceramic support, with the electrode layer and the metal shearing surface layer being metalized, deposited, sputtered, plated, bonded, or otherwise fixed to the ceramic support. In a third embodiment, the insulating layer is deposited, bonded, or otherwise fixed onto a metal blade which includes the cutting edge and shearing surface, while the electrode metal layer is metalized, deposited, sputtered, plated, bonded, or otherwise fixed onto the insulating layer. In a fourth embodiment, the insulating layer is a composite material such as fiberglass which is provided with metal electrode and metal shearing surface layers which are metalized, deposited, sputtered, plated, bonded, or otherwise fixed onto opposite sides of the fiberglass layer. In all embodiments, since the metal cutting edges and shearing surfaces are insulated from the electrodes, no short circuit can form between the electrodes even though the cutting edges and shearing surfaces are metal. 
     As the scissor blades are intended for use as part of an endoscopic instrument, each blade is preferably provided with a first hole which receives an axle or clevis pin around which the blades rotate. In addition, each blade is preferably provided with a pin or protrusion extending from a proximal or base portion of the blade. The pins are provided to receive links which couple the blades to an actuator mechanism. 
     The endoscopic bipolar cautery scissors instrument which utilizes the blades of the invention is substantially as is described in copending application U.S. Ser. No. 08/284,793, the complete disclosure of which is hereby incorporated by reference herein, and utilizes a push rod assembly with two conductive push rods which are stabilized and insulated relative to each other. The distal ends of the push rods are coupled to the end effectors by the links. The proximal ends of the push rods extend through the handle and lever of the scissors instrument and present electrical cautery pins onto which a standard bipolar cautery plug can be mated. 
     Additional objects and advantages of the invention will become apparent to those skilled in the art upon reference to the detailed description taken in conjunction with the provided figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a broken side elevation view in partial section of an endoscopic bipolar scissors instrument according to the invention; 
         FIG. 2  is a broken top view in partial section of the instrument of  FIG. 1 ; 
         FIG. 3  is an enlarged broken side elevation view in partial section of the distal end of the instrument of  FIG. 1 ; 
         FIG. 3   a  is an enlarged broken top view in partial section of the distal end of the instrument of  FIG. 1 ; 
         FIG. 4  is a view similar to  FIG. 3   a  of a second embodiment of a distal push rod collar; 
         FIG. 4   a  is a side elevation view of the collar of  FIG. 4 ; 
         FIG. 4   b  is a distal end view of the collar of  FIG. 4   a;    
         FIG. 4   c  is a proximal end view of the collar of  FIG. 4   a;    
         FIG. 5  is an enlarged top view of a first embodiment of scissor blades according to the invention; 
         FIG. 6  is a cross sectional view of the scissor blades of  FIG. 5  taken along lines  6 - 6  and shown in their operating positions; 
         FIG. 7  is a view similar to  FIG. 6  but showing one of the scissor blades of  FIGS. 5 and 6  in use with a conventional scissor blade in an alternative first embodiment; 
         FIG. 8  is a view similar to  FIG. 5  of a second embodiment of the scissor blades according to the invention; 
         FIG. 9  is a cross sectional view of the scissor blades of  FIG. 8  taken along lines  9 - 9  and shown in their operating positions; 
         FIG. 10  is a view similar to  FIGS. 5 and 8  of a third embodiment of the scissor blades according to the invention; 
         FIG. 11  is a cross sectional view of the scissor blades of  FIG. 10  taken along lines  11 - 11  and shown in their operating positions; 
         FIG. 12  is a view similar to  FIGS. 5 ,  8 , and  10  of a fourth embodiment of the scissor blades according to the invention; and 
         FIG. 13  is a cross sectional view of the scissor blades of  FIG. 12  taken along lines  13 - 13  and shown in their operating positions. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning now to  FIGS. 1 through 3   a , an endoscopic bipolar scissors instrument  10  includes a proximal handle  12  with a manual lever actuator  14  pivotally coupled to the handle by a pivot pin  15 . A hollow stainless steel tube  16  is rotatably coupled to the handle  12  and is preferably rotatable about its longitudinal axis relative to the handle  12  through the use of a ferrule  18  such as described in detail in previously incorporated copending application Ser. No. 08/284,793. A push rod assembly  20  extends through the hollow tube  16  and is coupled at its proximal end  22  to the manual lever actuator  14  as described in more detail in copending application Ser. No. 08/284,793. The distal end of the tube  16  has an integral clevis  24  within which a pair of scissor blades  26 ,  28  are mounted on an axle screw  30 . The distal end  23  of the push rod assembly  20  is coupled to the scissor blades  26 ,  28  so that reciprocal movement of the push rod assembly  20  relative to the tube  16  opens and closes the scissor blades  26 ,  28 . It will be appreciated that the reciprocal movement of the push rod assembly  20  relative to the tube  16  is effected by movement of the manual lever actuator  14  relative to the handle  12 . 
     The presently preferred embodiment of the push rod assembly  20  includes a pair of stainless steel rods  32 ,  34  which are molded into a proximal collar  36  and captured in a distal collar  46 . The proximal collar has a radial groove  40  in its distal portion and an increased diameter proximal portion  37  which carries a pair of electrical coupling pins  39  which are electrically coupled to the rods  32 ,  34 . As shown, the pins  39  are spaced farther apart from each other than the rods  32 ,  34  so as to accommodate a standard cautery connector. The rods  32 ,  34  are covered with insulating high density polyethylene (HDPE) tubes along substantially their entire length between the proximal and distal collars  36 ,  46 . A plurality of spaced apart polypropylene cylinders  50  are molded about the rods between the proximal collar  36  and the distal collar  46 . These cylinders stabilize the rods against helical twisting when the tube  16  is rotated and, by being discontinuous, prevent against warping of the push rod assembly. 
     According to one embodiment, and as seen best in  FIGS. 3 and 3   a , the distal collar  46  is made from two ceramic pieces  46   a ,  46   b  which are snap fit and bonded to each other. A pair of clevis insulators  76  are placed in the clevis as shown in  FIG. 3   a . Each clevis insulator  76  has a proximal side slot  76   a  and a distal bushing hole  76   b . The collar  46  has a pair of guiding wings  47 ,  49  which engage slots  76   a  in the clevis insulators  76 . The electrically conductive rods  32 ,  34  exit the distal collar  46  through opposite sides at substantially right angles. The distal ends of the rods  32 ,  34  are mechanically and electrically coupled to the respective blades  26 ,  28  by respective electrically conductive links  99 . 
     According to a presently preferred embodiment, and as best seen in  FIGS. 4 ,  4   a ,  4   b , and  4   c , a distal collar  146  is a single ceramic unit which is substantially circular in cross section except for upper and lower projections  147 ,  149 . These projections engage the space between arms  24   a ,  24   b  of the clevis  24  and prevent the collar  146  from rotating in the clevis  24  and from passing beyond the proximal end  24   c  of the clevis  24 . Consequently, the projections each have a pair of substantially parallel edges  147   a ,  147   b ,  149   a ,  149   b  and a rounded proximal edge  147   c ,  149   c . The collar  146  has a pair of push rod receiving channels  150 ,  152  for receiving the push rods  32 ,  34  respectively. The channels have portions  150   a ,  152   a  which are radially open to the surface of the collar  146  from the proximal end thereof to a point approximately half way under the projections  147 ,  149 . The channels  150 ,  152  terminate under the projections  147 ,  149  with a right angle bend  150   b ,  152   b . A radial opening  150   c ,  152   c  extends proximally along each side of the collar from the right angle bend  150   b ,  152   b  to a point contiguous with the radially open part  150   a ,  152   a  of the channels  150 ,  152 . The radial openings  150   c ,  152   c  are each substantially orthogonal to the radially open parts  150   a ,  152   a . The distal end of the collar  146  has a pair of ramped slot openings  154 ,  156  which terminate at their proximal ends with substantially semi-circular grooves  158 ,  160 . The slot openings and grooves are provided to accommodate the ends of links  99  (see  FIGS. 1 and 3 ) for coupling the distal ends of the push rods  32 ,  34  to scissor blades. The collar  146  is easily attached to the distal ends of the push rods  32 ,  34  by pressing the push rods into the radially open parts  150   a ,  152   a  of the channels  150 ,  152  so that the bent ends of the push rods enter the radial openings  150   c ,  152   c . The push rods and/or the collar  146  are pushed towards each other so that the bent ends of the push rods abut the right angle bends  150   b ,  152   b  in the channels  150 ,  152 , at which location the links  99  are coupled to the push rods. 
     Referring now to a first embodiment of the scissor blade invention seen in  FIGS. 5 and 6 , the first scissor blade  26  has a distal portion  26   a , a lower proximal tang  26   c , and a mounting hole  26   d  therebetween. A connecting lug  26   e  extends orthogonally outward from the surface of the tang  26   c  in a first direction. As shown in  FIGS. 5 and 6 , the distal portion  26   a  includes an lower cutting edge  26   b  and an inner surface  26   f  (also called the shearing surface). Behind the inner surface  26   f  of the first scissor blade is an insulating layer  26   r , and a conducting electrode layer  26   q . The opposed second scissor blade  28  is configured similarly to the first scissor blade and has a distal portion  28   a , an upper proximal tang  28   c , and a mounting hole  28   d  therebetween. A connecting lug  28   e  extends orthogonally from the surface of the tang  28   c  in a second direction which is opposite to the first direction mentioned above. The distal portion  28   a  includes an upper cutting edge  28   b  and an inner surface  28   f . Behind the inner surface  28   f  of the second scissor blade  28  is an insulating layer  28   r , and a conducting electrode layer  28   q.    
     According to the first embodiment shown in  FIGS. 5 and 6 , both scissor blade assemblies  26  and  28  are laminated assemblies which include a metal support (also called a metal blade support)  26   q ,  28   q , an intermediate electrically insulative layer  26   r ,  28   r  and a metal blade or face  26   f ,  28   f  defining a shearing surface. It will be appreciated that the metal faces  26   f ,  28   f  are preferably provided with sharpened opposed cutting edges  26   b ,  28   b . The metal blade supports  26   q ,  28   q  form the electrically conductive portions (i.e., the electrodes) of the scissor blades through which cautery current is applied. In this regard, substantially the entire lengths of blade supports  26   q ,  28   q  are conductive, including the proximal lugs  26   e  which make electrical connection with the respective rods  32 ,  34  via links  99  as described above with reference to  FIGS. 3-4   c . As seen in  FIG. 6 , the preferential path of current flow “E” is through the metal support portions  26   q ,  28   q  of the scissor blades which are insulated from the cutting edges  26   b ,  28   b  and the shearing surfaces (faces)  26   f ,  28   f  of the blades. Because of this arrangement, cautery and coagulation current may be applied continuously throughout the cutting/shearing procedure since the contact of the cutting edges and shearing surfaces of the blades will not short circuit the device. 
     The embodiment shown in  FIGS. 5 and 6  may be manufactured by first laminating machined or cast stainless steel, superalloy, bronze or other conductive metal blade supports  26   q ,  28   q  with the insulating layers  26   r ,  28   r  such as by gluing, glazing, spraying, depositing, firing, or otherwise fixing a ceramic to the inner surfaces of blade supports  26   q ,  28   q . The metal faces  26   f ,  28   f  having the cutting edges and shearing surfaces may then be applied by gluing, sputtering, metalizing, thermal spraying, plating, or otherwise fixing the metal layers  26   f ,  28   f  onto the insulating layers  26   r ,  28   r . The edges  26   b ,  28   b  may be sharpened after the laminating process is completed. The insulating layers may advantageously be made of an aluminum-oxide or another ceramic, and a nickel/aluminum coating may be advantageously applied to the blade supports to aid in bonding the aluminum-oxide ceramic insulating layers to the metallic blade supports. 
     From the foregoing, it will be appreciated that in order to achieve the object of preventing the cutting edges and shearing surface from short circuiting the device, it is only necessary that one of the scissor blades be constructed as described above.  FIG. 7  shows an alternative to the first embodiment of the invention where one of the blades  26  of the first embodiment is used in conjunction with a conventional scissor blade  128  which is entirely conductive. In this embodiment and in the embodiments described below, similar reference numerals refer to similar elements of the embodiments. As illustrated in  FIG. 7 , the preferential path of current flow “E” is through the metal support portion  26   q  of blade  26  to the shearing surface  128   f  and/or cutting edge  128   b  of the scissor blade  128 . 
       FIGS. 8 and 9  show a second embodiment of scissor blades  226 ,  228 . According to this embodiment, both scissor blades  226  and  228  are laminated assemblies which include a blade support  226   q ′,  228   q ′, which itself is a laminated sub-assembly of a non-conductive core support  226   r ,  228   r  and an outer metallic layer support  226   q ,  228   q . A metal blade layer or face  226   f ,  228   f  defining a shearing surface is laminated to the inner surface of the non-conductive core  226   r ,  228   r . It will be appreciated that the metal blade layers  226   f ,  228   f  are preferably provided with sharpened opposed cutting edges  226   b ,  228   b . The outer metallic layers  226   q ,  228   q  of the blade supports  226   q ′,  228   q ′ form the electrode portions of the blades through which cautery current is applied. As seen best in  FIG. 8 , the outer metallic layers  226   q ,  228   q  extend along substantially the entire length of the blades (over the non-conductive cores  226   r ,  228   r ) to make an electrical connection with a source of cautery at the proximal connecting lugs  226   e ,  228   e  of the blades. As seen in  FIG. 9 , the path of preferential current flow “E” is through the electrode portions  226   q ′,  228   q ′ of the blades which are insulated from the cutting edges and the shearing surfaces of the blades. Because of this arrangement, cautery current may be applied continuously throughout the cutting procedure since the contact of the shearing surfaces of the blades will not short circuit the device. 
     The embodiment shown in  FIGS. 8 and 9  may be manufactured by molding ceramic cores  226   r ,  228   r  and laminating both the inner and outer surfaces with metal by gluing, sputtering, metalizing, thermal spraying, plating, etc. the metal layers onto the ceramic cores. In this case, the ceramic material should preferably be formed with a flange type cross section as denoted by  226   r ′,  228   r ′ so that the inner and outer metal laminates do not contact each other. According to the presently preferred embodiment, the outer layers may be formed from a metal such as copper, gold, stainless steel, superalloy, or other conducting material. Preferably, the inner surface layer including the cutting edges  226   b ,  228   b  are formed from a metal which can be sharpened after the laminating process is completed. The ceramic cores  226   r ,  228   r  may be made of aluminum-oxide ceramic and nickel/aluminum coated to aid in bonding with the inner and outer metal laminates. 
     It will be appreciated that either of the blades  226 ,  228  from  FIGS. 8 and 9  may be used with an opposed blade  28 ,  26  from  FIGS. 5 and 6 , or with a conventional blade  128  from  FIG. 7  as explained above with reference to  FIG. 7 . 
       FIGS. 10 and 11  show a third embodiment of scissor blades  326 ,  328 . According to this embodiment, both scissor blades  326  and  328  are formed from metallic blades  326   f ,  328   f  which include the cutting edges  326   b ,  328   b  and shearing faces, and which are coated with a thin non-conductive layer  326   r ,  328   r  on their outer surface by gluing, glazing, spraying, depositing, firing, or otherwise fixing the non-conductive layer to the outer surfaces of the blade supports  326   f ,  328   f . An outer metallic conductive layer or support  326   q ,  328   q  is then applied to the non-conductive layer  326   r ,  328   r  by gluing, sputtering, metalizing, thermal spraying, plating, or otherwise. The outer metallic layers  326   q ,  328   q  form the electrically conductive portions of the blades through which cautery current is applied. As seen in  FIG. 10 , both the insulating coating  326   r ,  328   r  and the outer metallic coating  326   q ,  328   q  extend along substantially the entire length of the blades so that electrical connection to a source of cautery current may be made at the connecting lug  326   e ,  328   e  of the blade to the outer metallic coatings  326   q ,  328   q  only. As seen in  FIG. 11 , the path of preferential current flow “E” is through the electrode portions  326   q ,  328   q  of the blades which are insulated from the cutting edges and the shearing surfaces of the blades. One advantage of this third embodiment is that the cutting edges  326   b ,  328   b  of the scissor blades  326 ,  328  are part of standard type blades  326   f ,  328   f  which are coated. Thus, the feel of the endoscopic bipolar cautery instrument should be substantially the same as the feel of non-cautery endoscopic scissors. 
     Again, it should be noted that either of the blades  326 ,  328  of the third embodiment may be utilized with an opposed blade  28 ,  26 ,  228 , or  226  from  FIG. 5 ,  6 ,  8 , and  9 , or with a conventional blade  128  from  FIG. 7  as explained above with reference to  FIG. 7 . It will also be appreciated that although the blades shown herein are relatively flat, curved scissor blades such as those shown in the copending application Ser. No. 08/284,793 may be used instead. 
     A fourth embodiment of scissor blades  426 ,  428  is shown in  FIGS. 12 and 13 . The first scissor blade  426  has a curved distal portion  426   a , a lower proximal tang  426   c , and a mounting hole  426   d  therebetween. A connecting lug  426   e  extends orthogonally outward from the surface of the tang  426   c  in a first direction. As shown in  FIGS. 12 and 13 , the distal portion  426   a  includes a lower cutting edge  426   b  and an inner or shearing surface  426   f . Behind the inner surface  426   f  of the first scissor blade is an insulating layer  426   r , and a conducting electrode layer  426   q . The opposed second scissor blade  428  is configured similarly to the first scissor blade and has a curved distal portion  428   a , an upper proximal tang  428   c , and a mounting hole  428   d  therebetween. A connecting lug  428   e  extends orthogonally from the surface of the tang  428   c  in a second direction which is opposite to the first direction mentioned above. The distal portion  428   a  includes a upper cutting edge  428   b  and an inner surface  428   f . Behind the inner surface  428   f  of the second scissor blade  428  is an insulating layer  428   r , and a conducting electrode layer  428   q.    
     According to this fourth embodiment, both blades  426  and  428  are laminated assemblies having a non-conductive core  426   r ,  428   r . The core  426   r ,  428   r  is preferably formed from a fiberglass or a similar material and includes the curved distal portion  426   a ,  428   a , the proximal tang  426   c ,  428   c , and the mounting hole  426   d ,  428   d . A metal blade layer  426   f ,  428   f  defining a shearing surface is laminated to the inner surface of the non-conductive core  426   r ,  428   r  along the curved distal portion  426   a ,  428   a . It will be appreciated that the metal blade layers  426   f ,  428   f  are preferably provided with sharpened opposing cutting edges  426   b ,  428   b . An outer metallic support layer  426   q ,  428   q  is laminated to the outer surface of the non-conductive core  426   r ,  428   r  from the mounting hole  426   d ,  428   d  along the curved distal portion  426   a ,  428   a . The outer metallic support layers  426   q ,  428   q  form the electrically conductive portions of the blades through which cautery current is applied. Thus, the outer metallic support layer  426   q ,  428   q  extends along substantially the entire length of the core  426   r ,  428   r  to make and electrical connection at the lug  426   e ,  428   e  as described above with reference to  FIGS. 3-4   c . As seen in  FIG. 14 , the path of preferential current flow “E” is through portions  426   q ,  428   q  of the blades which are insulated from the cutting edges and the shearing surfaces of the blades. It should be noted that the laminated blades of the fourth embodiment can be made more flexible than the blades of the other embodiments. It should also be noted that the laminated blades of the fourth embodiment could be provided as straight blades. Further, it will be appreciated that a straight or curved blade of the fourth embodiment can be used with any of the blades of the first, second, or third embodiments, or with a conventional blade such as shown in  FIG. 7 . 
     There have been described and illustrated herein several embodiments of bipolar endoscopic surgical scissor blades and an instrument incorporating them. While particular embodiments of the invention have been described, it is not intended that the invention be limited thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. Thus, while particular conductive and non-conductive materials have been disclosed, it will be appreciated that other materials could be utilized. Also, while blades of specific shape and dimension have been shown, it will be recognized that blades having different shapes and dimensions could be used with similar results obtained. While means for pivotally joining the blades has been shown as an axle screw with a nut, other pivotal joining means could be used. For example, a clevis with an integral axle pin, or a snap-in axle pin, or a riveted axle pin could all be used. While means for supplying each blade with a voltage has been shown as a bipolar push rod, it will be appreciated that other means such as a bipolar clevis and bipolar hollow tube could be used. Individual shielded electrical conductors within the hollow tube could also be used for this purpose. In addition, while the electrical coupling of the conductive portion of each blade has been shown as the proximal connecting lug which connects to a link, it will be appreciated that an electrical coupling could be made through a two piece bipolar clevis axle. Also, while the means for imparting scissor-like movement to the blades has been shown as a push rod, a pull wire or other reciprocating arrangement might be used as well. In addition, while the means for coupling the scissor blades to the push rod has been shown as an orthogonal lug, it will be understood that other means such as a connecting hole could be used while achieving substantially the same results. Moreover, while particular methods have been disclosed in reference to laminating conductive and non-conductive layers, it will be appreciated that other methods could be used as well.