Surgery – Instruments – Electrical application
Reexamination Certificate
2001-06-14
2002-10-29
Peffley, Michael (Department: 3739)
Surgery
Instruments
Electrical application
C606S048000
Reexamination Certificate
active
06471701
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Filed of the Invention
The present invention generally relates to a high-frequency (hf) resectoscope implement to cut body tissue in a body cavity filled with an electrically conducting fluid, such as the human bladder. More particularly, the present invention is directed toward an hf resectoscope implement having a loop support and a loop-shaped cutting electrode mounted distally to the loop support, wherein a plane of the electrode slants relative to a longitudinal axis of the loop support.
2. Description of Related Art
Conventional resectoscopes make use of the mono-pole technique, wherein an hf current is set up between the resection electrode, which is the active electrode, through the body of the patient and a neutral electrode of substantial surface, which is mounted externally on the patient, for instance on the thigh.
However, passing current through the patient's body entails certain risks which, even when the resectoscope is expertly handled, can never be completely eliminated. For instance, uncontrolled or stray leakage currents may lead to painful skin bums on the patient when the patient contacts a metallic object such as the operating table. If there are current-induced muscle contractions, there is danger that the patient will move in an uncontrolled and sudden manner and, thus, be subjected to unintended cutting injury by the resectoscope implement. Latently, there is also a danger that the muscles or nerves near the resection area may be damaged, at least temporarily, by stray currents.
The above dangers can be widely eliminated using bi-polar techniques wherein both the active electrode and the neutral electrode are inserted into the patient's body. As a result, the hf current is set up only between the two implement electrodes, but not, and if so only over defined short paths, through the body of the patient.
A bi-polar hf resectoscope implement is disclosed in the German Offenlegungsschrift 25 21 719, which is considered the nearest state of the art. Therein, the neutral electrode is mounted at the loop support arm and together with the loop support arm can be axially moved into and out of the stem of a resectoscope. This feature offers the advantage that the spacing between the active and neutral electrodes remains constant and that, accordingly, the current paths are also substantially constant. Therefore, the cutting action of the cutting electrode is approximately constant at any advanced position of the implement.
As regards implements of this kind, the neutral electrode is in the fluid and spaced from the body tissue. When the active electrode makes contact with the tissue, the hf current passes through the body tissue and then into the fluid and from the fluid back to the neutral electrode.
However, the bi-polar technique incurs problems of current losses arising from current passing directly through the electrically well-conducting fluid between the active and the neutral electrodes without passing through the body tissue. Consequently, only a portion of the current applied to the hf implement will effect the cutting by the active electrode, namely that portion which passes from the active electrode into the body tissue and from there back to the neutral electrode.
These current losses are amplified especially if the intervention takes place in body cavities containing an especially electrically well-conducting fluid. This may occur, for instance, when resection rinsing is carried out using a fluid rich in electrolyte, illustratively an isotonic fluid. In such cases even the major portion of the current goes straight from the cutting site, that is, from the active electrode to the neutral one, without contributing to cutting. Accordingly, cutting by means of hf resectoscope implements of the state of the art in body cavities filled with an electrically conducting fluid is impossible, or only possible in an unsatisfactory manner.
The state of the art meets this problem by typically using electrically poorly conducting fluids when rinsing. It must be considered, however, that blood vessels are opened during resection and that part of the fluid inevitably enters the blood circulation of the patient. As a result, the patient may experience a complex of symptoms, also known as the TUR [transurethral resection] syndrome, such as vomiting, heart arrhythmia, kidney failure, shock. Therefore, using electrically poorly conducting fluids as rinses appears inappropriate, especially when it is realized that the above-noted reactions arise less intensely, sometimes not at all, when the isotonic fluids are used.
SUMMARY OF THE INVENTION
Therefore, an objective of the present invention is to create an hf resectoscope implement that overcomes the above difficulties and is optimized for the resection of body tissue in a body cavity filled with an electrically well-conducting fluid.
The effectiveness and, hence, an advantage of the present invention is an insulator structure, hereafter “insulator”, between the cutting electrode and the neutral one, that hampers the straight current between the two electrodes. Hence, the present invention reduces current flow directly between the electrodes, so that a larger portion of the supplied hf power is fed from the cutting electrode into the body tissue and there into cutting work. Vice-versa, less power is required by the implement of the invention relative to those of the state of the art to attain the cutting.
The basic idea of mounting an insulator between the active and the neutral electrode is known from the extra-species patent document WO 97/24993 which, in its FIG. 9, shows an implement comprising a rolling, spherical electrode of vaporization mounted in rotatable manner on a support. The ball's axis of rotation is perpendicular to the support's longitudinal axis. A hemispheric insulator, which also rests on the support, is mounted a slight distance above the ball. The neutral electrode is mounted on the insulator side, which is away from the vaporization electrode. In this manner a lesser straight current is attained between the active electrode and the neutral one. However, this design masks much of the field of view otherwise available to the surgeon. This drawback is inherent when using a spherical electrode.
The neutral electrode of the bipolar hf implement may, in principle, be mounted anywhere on the loop support. In further accordance with the present invention, however, the neutral electrode is configured distally at the loop support. This feature offers the advantage that when the implement is inserted into the stem tube of the resectoscope it need not move past the observation or illumination optics mounted in the stem tube. Instead, if the implement is properly dimensioned, the implement will be distally in front of the optics when it is inserted. In order to prevent arcing, care must be taken that the neutral electrode does not touch the optics. It is understood that the insulator must also be mounted distally at the loop support so that it can shield the electrodes from each other.
The cutting electrode, the insulator and the neutral electrode all are mounted on the loop support and held in place by the loop support. In the most general design, the three elements may be mounted in a mutually independent manner on the loop support, for instance by means of arms spreading from the loop support. Such a feature, however, is both uneconomical as regards manufacture and of low mechanical strength. Therefore, in accordance with another feature of the present invention, the neutral electrode is mounted directly on the insulator side away from the cutting electrode. Accordingly, the insulator supports the neutral electrode and imparts mechanical strength to the neutral electrode while improving the shielding geometry.
The geometry of the neutral electrode is widely arbitrary. However, in accordance with another feature of the invention, the-neutral electrode is mounted face-to-face or surface-on-surface to the insulator to be better held in place. More
Brommersma Pieter
Kikuchi Yasuhiko
Olympus Winter & Ibe GmbH
Peffley Michael
Rankin, Hill Porter & Clark LLP
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