Surgery – Instruments – Electrical application
Reexamination Certificate
2001-02-27
2003-01-28
Jeffery, John A. (Department: 3742)
Surgery
Instruments
Electrical application
C606S039000, C606S041000
Reexamination Certificate
active
06511479
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a disposable electrosurgical blade or active electrode used to perform electrosurgical procedures and to a method manufacturing such a blade. More particularly, the present invention relates to a new and improved electrosurgical blade exhibiting release characteristics as a result of having a relatively thin and uniform cross-sectional coating of nonstick material comprising silicone which is directly adhered to and supported on a metallic body of the blade. Even more particularly, the present invention relates to a new and improved method of fabricating an electrosurgical blade having non-stick, release characteristics by steps involving adhering a nonstick coating comprising silicone to an oxide of the metal body, thereby avoiding the typical requirements for mechanically roughening the metal body to achieve adequate adhesion or for applying intermediate layers of primer materials or multiple layers of materials to attain the desired characteristics.
BACKGROUND OF THE INVENTION
In general, electrosurgery involves the application of relatively high frequency or radio frequency (RF) current to living tissue. Depending upon the characteristics of the RF signal, electrosurgery is used to cut tissue, to coagulate bleeding (hemostasis) from the tissue or to both cut and coagulate simultaneously. The typical frequency of the electrosurgical current is from approximately 400 kHz to 750 kHz, because this frequency range avoids stimulating the nervous system. The electrical power applied can vary from a few watts for delicate neurosurgical procedures to approximately 300 watts for cutting substantial tissues in open surgical procedures. The open circuit voltage prior to energy transfer into the tissue may be in the range of 5,000-10,000 volts peak to peak. Of course, the voltage drops substantially as the current flow increases through the impedance of the tissue. Typical tissue impedances range between about 10 ohms and 500 ohms.
Electrosurgery is performed by connecting the electrosurgical blade or active electrode to an electrosurgical generator, activating the generator to supply the electrosurgical waveform, and delivering the energy of the electrosurgical waveform to the tissue through the blade. The blade is positioned in a pencil-like handpiece which the surgeon manipulates to achieve the desired effect at the surgical site. Selecting and adjusting the characteristics of the electrosurgical waveform delivered by the electrosurgical generator allows the surgeon to cut the tissue, to coagulate bleeding from the tissue, or to simultaneously cut and coagulate. The ability to control the application of electrical energy to the tissue to cut and coagulate tissue is one of the substantial advantages of electrosurgery, and such advantages contribute to the use of electrosurgery in most major surgical procedures.
The physical characteristics of the typical electrosurgical blade also are used advantageously by the surgeon to accomplish different surgical procedures. The typical electrosurgical blade has an elongated working area with a shape similar to a rectangle in cross-section. Two relatively-broad and generally-parallel sides extend along and exist on opposite sides of the working area. The two broad sides are joined by a narrow edge which extends between the broad sides and which curves around a distal end or tip of the working area. The edges form the narrow legs of the cross-sectional rectangle while the broad sides form the wide legs of the cross-sectional rectangle.
Cutting is achieved by bringing the narrow edge into close adjacency with the tissue. A high current density at the narrow leading edge transfers energy into the tissue as relatively short arcs, thereby causing enough heat to explode or rupture the cells of the tissue at the interface with the narrow leading edge. The tissue separates at the leading edge leaving a well-defined incision. It is in this manner that the current from the electrosurgical blade cuts the tissue, rather than the tissue being separated from the physical contact and mechanical action of a sharp edge, as is the case with a traditional scalpel. Indeed, the narrow edge of the typical electrosurgical blade is not sharp and cannot cut tissue as a result of mechanical action. The separated tissue passes by the broad sides of the working area of the active electrode as the surgeon guides the blade, while the electrical energy creates the incision.
Coagulating bleeding surfaces usually involves bringing the tip of the working area of the blade to a point spaced slightly above the bleeding surface and delivering a duty cycle type of coagulating electrosurgical waveform. The duty cycle coagulating waveform includes an on time period during which the high frequency electrical signal is delivered, followed by an off-time during which no electrical energy is delivered. The coagulating duty cycles are repeated at a frequency in the neighborhood of approximately 30 kHz, with a power of approximately 50-80 watts. Longer arcs of electrical energy are transferred in a spray-like manner from the tip of the blade and these arcs penetrate into the tissue to create a reticulum which both activates the normal clotting mechanism in the blood and thermally seals the surface of the tissue. Bleeding vessels are coagulated in much the same manner except that the tip of the blade is sometimes placed in close adjacency with the severed vessel, causing the arcs to be concentrated at that location.
Simultaneous cutting and coagulating occurs by blending the duty cycle coagulation waveform with a continuous waveform. In general, this involves increasing the on-time of the duty cycle to sufficient amount which permits cutting to occur but which still allows coagulation to be achieved. Because of the relative convenience and quickness with which coagulation can be achieved, many surgical procedures will usually progress more rapidly by using electrosurgery than if electrosurgery was not used.
The bursting cells release cell protein and fluids into contact with the surface of the electrosurgical blade. Blood also contacts the surface of the electrosurgical blade as the tissue is severed and when the surgeon uses the electrosurgical blade to coagulate blood flow. Different types of tissues emit other types of body fluids into the surgical field, and these other body fluids may contact the electrosurgical blade.
The amount of electrical energy delivered to the tissue through the electrosurgical blade is sufficiently high so that the current flow through the blade itself heats the blade. Since the typical tissue impedance ranges in the neighborhood of tens of ohms to a few hundreds of ohms, the impedance of the blade itself is significant enough relative to the impedance of the tissue that the blade absorbs enough of the transferred energy to increase its temperature significantly during electrosurgery. The increased temperature of the blade causes the cell fluids, body fluids and blood to dehydrate, denature and accumulate on the blade in the form of a crust-like buildup. Unless periodically removed, the crust-like buildup increases as the blade is used.
The crust-like buildup is a significant distraction to the surgeon. The crust-like material negatively affects the electrosurgical performance. The crust-like buildup spaces the blade from the tissue, thereby making it difficult or impossible to transfer energy into the tissue to achieve the desired electrosurgical effect. The crust-like buildup on the broad sides of the blade also causes the blade to drag against the tissue at the incision, thereby creating an undesirable “feel” when manipulating the instrument. The crust-like buildup may obscure the vision of the surgeon at the expected location of energy delivery from the blade into the tissue, thereby making it more difficult to achieve the precise effect desired. The problem and consequences of the crust-like buildup on electrosurgical blades has been recognized as a significant issue in electrosurgery for many years.
One app
Gentelia John S.
Karpowich Ronald P.
Robb Alexander F.
Rodriguez Angel R.
Zobrist William P.
ConMed Corporation
Jeffery John A.
Ley John R.
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