Cutting loop electrode for high-frequency instrument

Details Cutting loop electrode for high-frequency instrument Cutting loop electrode for high-frequency instrument

1999-05-26

2001-06-12

Dvorak, Linda C. M. (Department: 3739)

Surgery

Instruments

Electrical application

C606S046000, C606S045000

Reexamination Certificate

active

06245069

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a loop electrode for a high-frequency instrument. Electrodes of this type are utilized, for example, in HF-resectoscopes.
BACKGROUND OF THE INVENTION
With conventional loop-shaped electrodes comprising a thin wire with a diameter of typical up to 1 mm or a corresponding flat material, incision and surface coagulation effects utilized for stanching the blood of cut blood vessels occur depending on the type of current—cutting mode, coagulation mode, spray coagulation mode—of the employed high-frequency generator.
The kind of current influences the “processing result”: dependent on the applied current, in addition to the cutting effect, surface coagulation is generated which permits stanching the bleeding of blood vessels running near the surface.
Large area ball or roller electrodes to which “coagulation current” is applied usually are used only for large-area stanching of blood as the final step of the surgical procedure.
As an alternative for high-frequency tissue removal, lasers can be employed for tissue ablation. Lasers suited for this purpose are substantially more expensive than high-frequency generators, therefore attempts have been made to find ways to also be able to remove adinomatous tissue as bloodlessly as possible using a high-frequency generator.
A number of authors have suggested using conventional monopolar electrodes with a cylindrical roll. Reference is made to U.S. Pat. No. 5,395,363. The surface of the cylindrical roll can be designed in a variety of ways: rolls with smooth surfaces, with grooved surfaces or with pointed surfaces are known. However, using high-frequency electrodes with rolls has the drawback that the relatively large roll impedes the surgeon's vision. Secondly, it is only possible in practice to vaporize the tissue with such type rolls by supplying higher high-frequency power, efficiency being unsatisfactory. This means the patient is not only exposed to very high current flow respectively high energy, which involves potential risk, for considerable time, but also the narcosis time is distinctly longer than in other surgical techniques.
Cutting loop electrodes are also known. Reference is made to U.S. Pat. No. 5,569,244. Conventional cutting loops typically employ a single flat lower surface. By flat is meant that a plane P would intersect the loop lower surface S in a line L. In other words, as viewed from the side (see FIG.
5
), or in cross section the loop exhibits a flat lower surface S. A drawback exists with this design in that a trailing edge E of the flat lower surface may increase irritation of the coagulated tissue.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an electrode for a high-frequency instrument which vaporizes as well as cuts the tissue and with which surgery time is shortened and/or irritation of the coagulated tissue is reduced.
The invention relates to high-frequency electrodes having a sharpened cutting edge which permits optimized current flow from the cutting edge into the tissue upon incision. The high current density occurring at the edge leads to optimum incision into the tissue. As the invented electrodes essentially has the general shape of a loop, it does not impede the surgeon's vision at the surgical site.
An element of the present invention is that it was recognized that it is possible to vaporize as well as cut with an electrode with reduced irritation to coagulated tissue, if the electrode is provided with a curved and/or multiple flat lower, i.e., approximately curved surface portions. By “curved” is meant that a plane P would intersect loop lower surface C in a point T somewhere on the surface (depending upon inclination of the plane) since the surface is a complex curved surface (see FIG.
1
). In other words, the electrode as viewed from the side or in cross section, exhibits a curved lower surface C. By “multiple flat” is meant that a plane P would intersect loop lower surface M in two or more lines L depending upon inclination of the plane (see FIG.
6
A). In other words, the electrode as viewed from the side or in cross section exhibits a lower surface having two or more, and preferably having three or more flat surfaces M.
The invented electrodes permit simultaneous “bloodless” cutting and vaporizing of the tissue with a reduction in the irritation which might occur due to a dragging of the known electrode's single flat lower surface's trailing edge E over the coagulated tissue (see FIG.
5
). On the basis of the inventive embodiment of a curved or multiple flat lower surface of the loop, high-frequency current flows into the tissue in a large surface and performs a coagulation and vaporization procedure during the cutting procedure. Nonetheless, it is still possible to “dig” respectively “excavate” to remove tissue with the invented electrode.
The selective application of the lateral stirrups to join the loop and lead or leads of the electrode provides advantages particular to conventional thin loop electrodes, notably removing respectively cutting off “parasol” sections of tissue.
In embodiment including stirrups, it is preferred if the stirrups do not comprise a wire material having a round cross section, but a band-shaped material respectively a material having an elliptical cross section, the longer axis of which extends in the direction of the longitudinal axis of the lead. In embodiments which desirably include stirrups, it is also generally preferred that the lead, the stirrups and the central section are arranged in a kind of “Z” configuration, facilitates cleaning the cut-off tissue from the invented electrodes.
The preferred dimensions of the cutting loop are a radius ® of about 3 mm at an angle (A) of about 60°. The radius of curvature ® of the lower surface is preferably about 2.5 mm.
The invented high-frequency electrode can be fabricated in a known manner and, in particular, can be made of high temperature resistant materials, in particular titanium alloys.
The top surface of the loop may be insulated in such a manner that current only flows through the bottom surface and cutting edge of the loop, thereby confining the current flow for vaporization and coagulation to the required region and reducing the patient's current load. The electrode trailing edge may also be insulated.


REFERENCES:
patent: 5782829 (1998-07-01), Swaintek et al.
patent: 5919190 (1999-07-01), VanDusseldorp
patent: 5957923 (1999-09-01), Hahnen et al.
patent: 6033400 (2000-03-01), Grossi et al.
patent: 6080152 (2000-06-01), Nardella et al.
patent: 2521719 (1976-11-01), None
patent: 295 19 844 (1996-03-01), None
patent: 825301 (1938-03-01), None

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