Monopolar and bipolar electrode for a urological resectoscope

Details Monopolar and bipolar electrode for a urological resectoscope Monopolar and bipolar electrode for a urological resectoscope

2002-06-04

2004-12-07

Rollins, Rosiland (Department: 3739)

Surgery

Instruments

Electrical application

C606S041000

Reexamination Certificate

active

06827717

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a monopolar and to a bipolar electrode for a urological resectoscope.
2. Description of Related Art
Resectoscopes are mostly used foremost for prostate resections, though, depending on the particular design, they also may be used for other surgical purposes. Herein the concept of “resectoscope” denotes endoscopic instruments wherein an optics and a monopolar or bipolar electrode-support, together with one or two distal electrodes, for instance a resecting and a neutral electrode configured in a stem tube. Further, the electrode support together with the electrodes are configured in an axially displaceable manner and are affixed at its proximal end to a resectoscope slide block with which it makes electric contact. The slide block is axially displaceable by manually driving a grip in order to axially displace the electrode.
During prostate resection, the resectoscope is advanced by its distal stem tube end through the urethra inside the prostrate. When hf is applied to the electrode, this electrode may be advanced and retracted by manually driving the slide block in order to cut tissue. Generally, the electrode is configured as a wire loop to trim tissue snippets. Furthermore, the electrode may assume other geometries, for instance being a button electrode, a roller electrode, a knife electrode or the like, in order to allow application to different purposes such as coagulation, cutting or the like.
Classical resectoscopy makes use of the monopolar or unipolar technology. Therein an hf current is set up between the resection electrode—the active electrode—through the patient's body and a neutral electrode of comparatively large surface externally affixed to the patient, for instance to his thigh.
However, the electric current through the patient's body entails risks that cannot be totally excluded even when the resectoscope is handled expertly. For instance, there are uncontrollable leakage or drift currents which, if the patient were to touch metal, for instance that of the operational table, may result in painful skin burns. Also, as regards current-induced muscle contractions, there is the danger the patient may move suddenly in an uncontrolled manner whereby he might be cut by the resectoscope. There is always some danger that muscles or nerves in the vicinity of the resection zone shall be damaged at least temporarily by drifting currents.
The above cited risks may be nearly entirely eliminated when using bipolar techniques. All such techniques offer the feature that not only the active electrode, but also the neutral or return electrode, are inserted into the body of the patient. As a result of this, the hf current is set up only between the two electrodes at the electrode support—but not, or merely over defined, short paths, through the body of the patient. Such a bipolar electrode is disclosed in the German Offenlegungsschrift 25 21 719 wherein, therefore, the electrode support is crossed by two electrical conductor wires.
It is also known, with respect to bipolar electrodes, to replace the neutral electrode with a second active electrode acting as the return electrode, the electric current being set up between these two electrodes each of which makes contact with the tissue. Such a bipolar electrode is shown in the patent document WO 96/234449.
However, both the monopolar and bipolar electrodes incur the problem of properly setting up electrical contact between the conductor wires feeding an electric current to the electrodes and their contact zones in the slide block. There the electrical connection or contact must be set up using extension cables leading to the output terminals of a separately set up hf generator. HF-loaded contact sites are problematical and tend to defects such as charring.
In older designs, a tightening screw simultaneously sets up the contact and the mechanical affixation of the electrode support inside the slide block. Once such a contact site chars, the entire slide block must be replaced.
A monopolar design of this kind is known from FIG. 3 of each of U.S. Pat. Nos. 4,917,621 and 4,919,131. The slide block is fitted with a continuous transverse cavity accepting the plug of the hf extension cable to contact the bared contact zone of the electrode support in this cavity. A clamping element acting on the affixation zone of the electrode support is configured distally relative to the cavity.
This design offers the advantage of separately mechanically affixing the electrode support and the clamping element on the slide block, as a result of which it is possible to first check this slide block's appropriate mechanical operation. Thereupon contact may be implemented with the plug. If the contact site should char, only the electrode support and the cable together with the plug need be changed. The clamping element and the slide block, on the other hand, remain intact because the clamping element is separate.
However, the known design of the above species has drawbacks. Because the affixation device is configured distally from the contacting element, the electrode support site where affixation takes place is crossed by the electric conductor connecting the contacting site to the active electrode. As a result the electrode support lacks mechanical strength in this region. The affixation device must allow for this lack of strength and, illustratively, may only operate with minute tightening forces. If affixation takes place by means of a slide block entering a groove and acting on the electrode support, then the groove may only be very shallow and consequently the reliability of affixation shall be considerably reduced.
The proximal end zone of the electrode support is constituted by the zone wherein affixation takes place and by the contacting zone. Therefore, these zones, namely the full end zone of the electrode support, are rigid and more resistant to bending than the remainder of the electrode support, which consists only of an inner conductor and an outer insulation. In resectoscopes, however, the electrode support typically will be configured tightly against the optics inside the stem tube, whereas, in the region of the slide block, the support and optics must be farther apart in order to subtend enough space for the contacting system and the affixation device. Therefore, the electrode support must be pivotably supported inside the main block in the manner indicated, for instance, in FIG. 13 of the patent document WO 96/234449. Since the main block is required to be of moderate length on technical grounds, substantial pivoting must take place over a short path. However, such pivoting motion is hampered by the considerable length of the rigid end region of the known electrode supports.
Moreover assembly may be defective if the electrode support was insufficiently inserted and thereupon was fixed in place and contacted.
With reference to FIG. 16 of the patent document WO 96/234449, which includes a bipolar electrode, the electrode support is fitted with two contact zones in the region of the slide block. An extension cable plug, which can be affixed to the slide block, sets up contact with both contact zones, which it furthermore clamps onto. This design does not provide a separate, special affixation element. Therefore, this design precludes affixing the electrode support to test mechanical operation before contacting takes place.
SUMMARY OF THE INVENTION
An objective of the present invention is to create an improved, monopolar or bipolar electrode of the above species, allowing to affix the electrode support in the slide block and to set up an electrical connection or contact with both steps being implemented in problem-free manner.
In accordance with the preset invention, the electrode support of the electrode is separate from the affixation zone and is configured proximally relative to the first contact zone. Accordingly, as regards the resectoscope's slide block, the affixation element must be proximal relative to the first contact elemen

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