Abstract:
An electrosurgical knife blade of insulating material having a pair of electrodes adapted to be connected to a radiofrequency generator.

Description:
BACKGROUND OF THE INVENTION 
     Electrosurgical blades of the type employed by surgeons heretofore, have comprised essentially conventional surgical steel cutting tool, such as a scalpel, connected to a suitable radiofrequency source. In the prior art, the patient is placed in electrical contact with a &#34;patient plate.&#34; The &#34;patient plate&#34; was connected to the ground terminal of the radiofrequency source, while the cutting blade was connected to the &#34;hot&#34; terminal of the radiofrequency source. Radiofrequency current flows from the edge of the cutting blade to the &#34;patient plate&#34; through the patient. Since the cutting blade is narrow and the &#34;patient plate&#34; is wide, the radiofrequency energy concentrates at the cutting edge of the knife, fanning out to the &#34;patient plate&#34; at the other side of the patient. Electrosurgical cutting blades cauterize small blood vessels as the blade penetrates tissue. However, in such prior art electrosurgery, patients have suffered from radiofrequency burns due to poor contact with the &#34;patient plate.&#34; As will be apparent, if the radiofrequency energy is not spread over a large area as it leaves the patient&#39;s body entering the &#34;patient plate,&#34; concentrations of radiofrequency energy due to lack of good overall contact may cause serious rf burns, since radiofrequency energy on the order of 100 W must be provided to enable sufficient energy concentration at the knife blade to be effective. 
     SUMMARY OF THE INVENTION 
     The electrical surgical blade of the present invention concentrates the radiofrequency field to the immediate vicinity of the blade. A blade of insulating material is provided, with rf electrodes closely adjacent to one another. As a result, much less radiofrequency power is required. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of one embodiment of the electrosurgical knife of the present invention; 
     FIG. 2 illustrates the rf field produced by the knife of FIG. 1 in use; 
     FIG. 3 illustrates another embodiment of the electrosurgical blade of the present invention; 
     FIG. 4 is an exploded cross section of the embodiment of FIG. 3; and 
     FIG. 5 illustrates the mode of operation of the embodiment of FIG. 3. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to FIG. 1, the electrosurgical knife of the present invention comprises a blade 11 of a hard, strong insulating material, sharpened to provide a cutting edge 12 on either side. The insulating material blade 11 may have any desired shape as found in conventional steel surgical blades. Insulated blade 11 is preferably fabricated of a suitable ceramic material providing the necessary strength and capable of providing and maintaining a sharp edge. Each face of the insulating blade is coated with a thin layer of a suitable conductive material 13 and 14. Conductive coating 13 and 14 may conveniently be a layer of tungsten. The tungsten coating may be applied to the ceramic substrate in a variety of ways. At present, the preferred method is to brush-coat the substrate with a slurry of water and finely-divided tungsten powder. After drying, this coating is fired in a hydrogen atmosphere. The tungsten coatings on faces 13 and 14 are isolated from one another by the uncoated sharp edge 12 of the blade. As illustrated in FIG. 2 the radiofrequency field extends across the sharp edge of the blade 12 from electrode 13 to electrode 14. 
     An alternative configuration of the electrosurgical blade of the present invention is illustrated in FIGS. 3, 4, and 5. In this embodiment the ceramic blade 11 may be substantially similar to that of FIG. 1 in plan, but having cutting edges adjacent to only one face. In this embodiment, the electrodes are placed on the same side of the blade as the cutting edge in the asymmetric cross section. A lower electrode 15, having a comb-shaped configuration, adheres directly to the ceramic substrate, with the teeth extended to the vicinity of cutting edge 12. An internal insulating layer 17 is placed on top of electrode 15. A second comb-like electrode 16 is placed on top of the insulating layer 17, with teeth extending to cutting edge 12 alternating with the teeth of electrode 15. The whole is covered with a surface insulating layer 21. 
     With the hereinabove disclosed configuration, the radiofrequency field runs parallel to the edge of the knife blade, in contrast with the arrangement of the embodiment of FIG. 1, wherein the radiofrequency field is directed across the edge of the blade. Conveniently, conventional printed circuit techniques may be employed for fabrication of the embodiment of the invention illustrated in FIG. 3. Exemplarily, the lower electrode 15 may be applied directly to the ceramic substrate 11 employing conventional printed circuit techniques. Insulating layer 17 may be applied in any convenient manner, well known to those skilled in the art. Upper electrode 16 is then applied to insulating layer 17. Finally surface insulator 21, preferably of a non-sticking material such as that known by the trade name &#34;Teflon&#34;, may be applied in any convenient manner over the top of the upper printed circuit 16. 
     Other electrical circuit fabrication techniques may be employed. Exemplarily, the electrodes may be fabricated by vapor deposition, electroplating, electroless deposition, and other means known to the art. 
     In contrast with the relatively high power--i.e., 100 W--required with prior art electrosurgical blades, the short distance between the electrodes in the electrosurgical blade of the present invention allows the employment of rf generators having an output of only 2 W. As illustrated in FIGS. 2 and 5, the rf field is concentrated between the closely adjacent electrodes. Rf burns are eliminated, together with the causes, high rf power flowing through the patient&#39;s body to the &#34;patient plate.&#34; There is no need to have the &#34;patient plate&#34; electrode make good rf contact over a large part of the patient&#39;s body. 
     The various features and advantages of the invention are thought to be clear from the foregoing description. However, various other features and advantages not specifically enumerated will undoubtedly occur to those versed in the art, as likewise will many variations and modifications of the preferred embodiment illustrated, all of which may be achieved without departing from the spirit and scope of the invention as defined by the following claims.