BACKGROUND OF THE INVENTION

1. Field of the Invention This invention relates to electrosurgical electrode in¬ struments for surgical cutting of body tissue.

2. Technical Background

Electrosurgical instruments are used extensively in surgi¬ cal practice and the advantages to their use over conventional non-electrical surgical instruments are well recognized in the practice. A common approach taken in the art of electrosurgery that is effective for both cauterizing and cutting tissue entails the use of a monopolar circuit. A monopolar circuit is composed of an electrosurgical generator with two outlet con- nections: an active and a dispersive. The dispersive outlet connects to a dispersive pad which is attached to a patient's body. The electrosurgical generator sends high frequency electrical energy through the patient's body by means of the dispersive connection. The active connection is connected to an electrode which is then placed in proximity to or in contact with the body. Thus, the electrical energy present in the body is concentrated to those specific areas in proximity to the electrode. Those cells of the body thus exposed to the concen¬ trated electrical energy are heated and then exploded by sparks arcing from the electrode to the cells. In this manner, the circuit is completed and, depending on further techniques, cauterization or cutting is achieved.

The shape and size of the electrode may vary depending on the purpose of the surgery. Commonly found in the surgical practice are electrosurgical instruments that utilize thin, wire electrodes. Typically, the wire electrodes are configured into needle or loop shapes. Both the needle and the loop electrodes are efficient cutters because their thinness allows the surgeon to concentrate the electrical energy to a very limited region of body tissue, thus fully utilizing the energy in the cutting process and preventing any unnecessary exposure to the electrical energy where cutting or burning of tissue is not desired. The principles that govern the electrosurgical

cutting process are well known, and the observation that thin wire electrodes are the best cutters is not a surprising con¬ clusion to any knowledgeable practitioner.

However, the wire electrodes are limited in their cutting performance due to their lack of mechanical rigidity and their general fragile nature. This is especially true when the electrodes become hot during the surgical cutting process. Furthermore, it is often desirable for the surgeon to use the cutting electrode, without current applied, as a mechanical tool to separate tissues (i.e.. cold or mechanical dissection) that are adjacent to each other but which should not be exposed to the electrical energy of electrosurgical cutting. Natural¬ ly, the thin electrodes function poorly in mechanically sepa¬ rating body tissue because they lack sufficient mechanical reinforcement to effect proper dissection.

An electrosurgical instrument that is conveniently used both for electrosurgical cutting and mechanical dissection is the paddle electrode. This elongated, flat electrode has the mechanical strength to allow mechanical dissection and is able to create sufficient current concentration on its edges to accomplish good electrosurgical cutting. However, compared to a needle or wire loop electrode, the paddle electrode is a less efficient cutter because much of the high frequency electrical energy supplied by the electrosurgical generator flows to the body tissue through the sides of the paddle electrode where no exposure or cutting activity is desired. In some circumstanc¬ es, the current flowing through the sides of the paddle elec¬ trode may have a beneficial effect in cauterizing the wound created in cutting through the tissue. However, in most cases, it is a wasteful use of current resulting in an extra burden for the electrosurgical generator and requires a larger power setting of the generator to accomplish the cut. Using a paddle electrode also frequently results in thermal damage to the tissue along the cut and in troublesome sticking of tissue to the sides of the paddle. Nevertheless, the paddle electrode has the advantages of superior mechanical strength and a flat shape that acts as a rudder giving the surgeon a better ability to guide the electrode along a straight or smooth curved line.

One attempt to solve the side conduction problem of the paddle electrode has been to coat the sides of the paddle with plastic, typically Teflon, which diminishes the current con¬ ducted out the side and prevents sticking of the tissue to the paddle electrode. This solution is only partially successful because at the high frequencies used for electrosurgery, there is substantial current that is capacitively coupled from the metal of the paddle, through the plastic coating, and to the body tissue. Thus, a more successful and permanent solution has yet to be realized.

From the foregoing, it will be appreciated that it would be an advancement in the art to provide an improved electro¬ surgical cutting device which realizes the advantages of the wire electrode and paddle electrode and at the same time elimi- nating their disadvantages. Specifically, it would be an advancement in the art to provide an electrosurgical cutting device which concentrates the electrical energy to a limited area of body tissue, yet has sufficient mechanical rigidity to allow improved cutting performance and to permit mechanical dissection. Yet another advancement in the art is to provide a device with the above features which is simple and economical to manufacture.

Such an electrosurgical cutting device is disclosed and claimed herein.

BRIEF SUMMARY OF THE INVENTION The present invention provides an electrosurgical cutting device to be used generally in all areas of surgical cutting. The present invention particularly contemplates the use of the electrosurgical cutting device as the active outlet in a mono¬ polar circuit. The present invention is designed to efficient¬ ly cut body tissue through the process of cell lysis using heat produced by electrical current concentrated at the site where cutting is desired. In the absence of electrical energy, the device is capable of manipulating or mechanically dissecting body tissue. Compared to conventional paddle electrodes, cutting efficiency is improved by greater concentration of current in the tissues. Tissue thermal damage is reduced by

elimination of current dispersed away from the cutting edge. This is accomplished by disposing a conducting member along the outer perimeter of a non-conductive support member. In the preferred embodiment the conducting member comprises a thin, wire electrode. The support member gives the wire electrode additional support, strength, and rigidity which will allow for better cutting. The rigidity provided by the non-conducting support member allows the surgeon better handling in position¬ ing the device and guiding the device to cut along a precise path. Furthermore, with the electrical energy to the conduct¬ ing member on or off, the support member allows sufficient mechanical strength to manipulate or mechanically dissect body tissue.

The support member is generally of a shape and length suitable to cutting body tissue and may be embodied as a paddle shape with two major surface areas and a width dimension. The support member has a peripheral edge that is sufficiently thin to allow efficient cutting, but thick enough to ensure suffi¬ cient strength in the support member. The support member is preferably composed of a rigid, thermally stable, non-conduc¬ tive material. Thus, the support member retains its strength and utility when exposed to the heat produced by electrical energy passing through the supported conducting member and the adjacent tissue. Furthermore, the support member does not conduct electrical energy, hence electrical energy is not conducted through the major surface areas of the support mem¬ ber, only along the peripheral edge where the conducting member is disposed. Consequently, electrical energy is only applied where the conducting member comes into contact with the body tissue. In a preferred embodiment, the support member is composed of any of a variety of ceramic substrates or plastics commonly known in the art but can be made of any other suitable rigid, non-conductive material.

The electrode embodied in the present invention may in- elude a handle for its manipulation by a surgeon or it may include an adaptable connector on its proximal end which in¬ serts into any of the common surgical electrode handles known in the industry to achieve an electrical connection to the

generator through the handle. The support member extends from the distal end of the handle or the adaptable connector. The conducting member may be disposed along a portion of or to the entire exposed peripheral edge of the support member. Those skilled in the art will recognize that many design configura¬ tions are possible by altering the shape of the support member and the placement of the conducting member along at least a portion of the peripheral edge of the support member. Although such configurations may result in different methods of handling the device due to different shapes and different points of contact of electrical energy, such variations do not depart from the spirit and scope of the claimed invention.

Connection between the conducting member and an electro¬ surgical generator is effectuated through the use of a conven- tional connecting wire or any other suitable means. The con¬ necting wire is of a type suitable for the conduction of high frequency electrical current, and is preferably insulated. The electrosurgical generator is of a type commonly used in the industry for transmitting high frequency electrical energy during electrosurgical operations. In the course of operation, the electrosurgical generator produces a high frequency energy which is transmitted through the connecting wire to the con¬ ducting member. The surgeon then guides the conducting member to the specified area of body tissue where the incision is to occur.

BRIEF DESCRIPTION OF THE DRAWINGS To better understand the invention, a more particular description of the invention will be rendered by reference to the appended drawings. These drawings only provide information concerning typical embodiments of the invention and are not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings, in which: FIG. 1 is a perspective view of one embodiment of the electrosurgical cutting device of the present invention;

FIG. 2 is a side view illustrating one embodiment of the electrosurgical cutting device of the present invention showing

the thickness of the support member and the placement of the conducting member along its peripheral edge;

Fig. 3 is a side view of one embodiment of the electrosur¬ gical cutting device of the present invention showing the obverse, or reverse surface area of the support member;

Fig. 4 is an enlarged sectional view of the support member along line 4-4 of Fig. 3;

Figs. 5 and 6 are side views of alternative embodiments of the electrosurgical cutting device with the conducting member encompassing additional fill material other than the support member;

Fig. 7 is a side view of an embodiment of the electrosur¬ gical cutting device with a portion of the conducting member (shown in phantom lines) passing internally through the support member; and

Fig. 8 is a perspective view of an embodiment of the electrosurgical cutting device with the support member extend¬ ing from the handle.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference is now made to the figures wherein like parts are referred to by like numerals throughout. With reference to Figs. 1, 2, and 3, there is illustrated an electrosurgical cutting device 10 of the present invention. The cutting device 10 may be used as the active outlet of a monopolar circuit. The cutting device 10 comprises a support member 12 composed of a strong, non-conductive material and a conducting member 14. The conducting member 14 is preferably embodied as a wire electrode and primary consideration is given to this embodiment in the specification. However, it is understood, and those skilled in the art will recognize, that other embodiments of the conducting member 14 such as conductive materials in the form of deposits, etchings, or sprays would be included within the scope of the present invention. Preferably the material for the support member 12 is thermally stable so that the support member 12 will be unaffected by the heat produced by electrical energy passing through the conducting member 14.

The material is preferably from any one of a variety of ceramic substrates commonly known and used in the art but can be made of any other suitable material such as plastic. The support member 12 may be configured in various shapes suitable for cutting body tissue, including paddle shapes similar to conven¬ tional paddle electrodes with an obverse side, reverse side, width dimension, and a peripheral edge 16. Optionally, the support member 12 may also be configured in a variety of knife blade or scalpel shapes such as shown in Figures 7 and 8. The support member 12 is configured with a thin peripheral edge 16 with the conducting member 14 disposed thereon, yet has suffi¬ cient mechanical strength to permit cold or mechanical dissec¬ tion, separating and manipulating the body tissue without conduction of electrical energy. There is sufficient space on the peripheral edge 16 to receive the conducting member 14.

Optionally, the support member 12 may be formed with a groove 15 along the peripheral edge 16 in which the conducting member 14 is securely seated as shown in Figure 4.

The conducting member 14 is separate and distinct from the support member 12 and is composed of a material which is suit¬ able to conduct high frequency electrical energy for cutting body tissue. In a preferred embodiment, the conducting member 14 is composed of tungsten or stainless steel. The conducting member 14 is secured to the peripheral edge 16 of the support member 12, such that the surgeon can easily guide the conduct¬ ing member 14 to the position of desired contact with the body tissue.

In the preferred embodiment depicted in Figs. 1-3, the conducting member 14 is embodied as a wire loop electrode with a wire forming a loop around the support member 12. In the preferred embodiment, the conducting member 14 is disposed along the entire exposed peripheral edge 16. However, those skilled in the art will recognize that a variety of configura¬ tions and embodiments are possible. For example, as shown in Figures 5 and 6, the loop formed by the conducting member 14 may encompass the support member 12 as well as some other fill material, such as air. The conducting member 14 may only be partially disposed along the peripheral edge 16, see Figures 7

and 8. In Fig. 7 the conducting member 14 is partially dis¬ posed along the peripheral edge 16 and a portion of the con¬ ducting member 14 is internal to the support member 12. In Fig. 8, the conducting member 14 the support member 12 is embodied in a scalpel shape and the conducting member 14 is disposed only along the leading edge of the support member 12. These configurations are illustrative of a variety of embodi¬ ments which are possible without departing from the scope of the invention. A typical practice in the art is to have the conducting member 14 attached to one end of a conducting adaptable connec¬ tor 20. The adaptable connector 20 is engageable with a handle 26, and electrical energy is transmitted from the electrosur¬ gical generator 22 through the handle 26 and adaptable connec- tor 20 to the conducting member 14. Fig. 1 illustrates dispo¬ sition of the handle 26 and adaptable connector 20 when dis¬ posed in electrical communication.

As illustrated in Fig. 1, support member 12 and conducting member 14 extend from the distal end of a conducting adaptable connector 20. The adaptable connector 20 serves two purposes. It engages a source for electrical energy from some conductive carrier such as the electrosurgical generator 22 and transmits the electrical energy to the conducting member 1 . It also permits attachment of the support member 12 and conducting member 14 to a handle 26 to facilitate hand-held manipulation of the cutting device 10. The adaptable connector 20 is of a configuration commonly known in the industry and its proximal end is insertable into a receiving handle 26 which is also commonly known in the industry. The handle 26 receives in mechanical engagement the adapt¬ able connector 20 and accommodates the communication of elec¬ trical energy through a connecting wire 18 which exits out the proximal end of the handle 26 and connects to an electrosurgi¬ cal generator 22. Fig. 1 shows the preferred embodiment of the invention in which the handle 26 is shown with an interior cavity 17 for receiving the connecting wire 18.

The connecting wire 18 connects to the electrosurgical generator 22 and preferably enters in the proximal end or

midsection of the handle 26 and passes into the interior cavity 17 of the handle 26, along a longitudinal axis of the handle 26. The connecting wire 18 electrically engages the adaptable connector 20. The connecting wire 18 is insulated and capable of carrying high frequency electrical energy to the conducting member 14 through the adaptable connector 20. In a preferred embodiment, the connecting wire 18 exiting from the electrosur¬ gical generator 22 is shielded within a cable 24 suitable for protecting the connecting wire 18. The electrosurgical generator 22 is of a type commonly known and used in the industry, and has an adjustable output of high frequency electrical energy. By controlling the output of the electrosurgical generator 22, the operator or surgeon is able to transmit sufficient high frequency electrical energy through the connecting wire 18 to the adaptable connector 20 and to the conducting member 14 to enable the conducting member 14 to cut body tissue.

Those skilled in the art will recognize that many other embodiments are possible without departing from the scope of the invention. For instance, rather than using an adaptable connector 20, the connecting wire 18 may connect directly to the conducting member 14. An embodiment may also forgo the use of an adaptable connector 20 and have the support member 12 and conducting member 14 extend from the distal end of a handle 26 as seen in Fig. 8. In such an embodiment the handle 26 would have means for conducting electrical energy from an electrosur¬ gical generator 22 to the conducting member 14.

It should be appreciated that the apparatus of the present invention is capable of being incorporated in the form of a variety of embodiments, only a few of which have been illus¬ trated and described above. The invention may be embodied in other forms without departing from its essential characteris¬ tics. The described embodiments are to be considered in all respects only as illustrative and not restrictive and the scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description.