Surgery – Diagnostic testing – Sampling nonliquid body material
Reexamination Certificate
2001-03-07
2001-11-27
Hindenburg, Max (Department: 3736)
Surgery
Diagnostic testing
Sampling nonliquid body material
Reexamination Certificate
active
06322523
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a biopsy instrument, and to methods and apparatus for collecting tissue samples or the like from humans or animals, in particular by excising a segment from a tissue, using the biopsy instrument. The invention also relates to a loading assembly for a biopsy instrument and an impact damping element for biopsy instruments.
2. Description of the Related Art
The invention departs from an apparatus for collecting tissue samples by excising a segment from tissue, and a corresponding method for harvesting of tissue samples described in U.S. Pat. No. 5,655,542 (Weilandt), the entire disclosure of which is incorporated by reference into this specification.
In this specification, the terms “proximal” and “distal” are used with respect to the person extracting a biopsy sample. Thus, the proximal end of a biopsy apparatus is its rear end, proximate the practitioner, and pointing away from the patient.
The biopsy instrument of the '542 patent includes a first part having an end with means for penetrating a tissue at the end, and a wall having an opening extending through the wall of the first part; and a second part adapted for being slidingly disposed on the first part, excision means for separating a segment of the tissue then penetrated by the first part provided on the second part such that sliding movement of the second part on the first part in one direction causes the excision means to pass through the opening in the wall of the first part thereby separating a segment of the tissue for extraction.
The method of harvesting biopsy samples of the '542 patent includes the steps of injecting the biopsy instrument into tissue to a position proximal of a sample to be taken; displacing simultaneously the first part and the second part of the biopsy instrument for reception of the sample in the first part; displacing the second part to sever the sample from the tissue.
The first part may take the form of a canula and the second part that of a tube in which the canula is slidingly arranged. The tube is provided with a finger at its distal end, the finger entering an opening in the canula wall in the tissue-severing step when the tube is displaced in a distal direction with respect to the canula.
The joint displacement of the first part and the second part following the injection step is accomplished by spring means, in particular a steel coil. Compression steel coils have been found to work well in practice, except for very powerful springs providing high acceleration to the combination of the first and the second part. High acceleration is attractive since, thereby, the use of separate driving force for the second step becomes superfluous, the displacement of the second part with respect to the first part being accomplished through the inertia of the second part. Moreover, high acceleration allows for less variation in sample quality when using the instrument with a variety of tissues. The loading of a biopsy instrument provided with powerful spring means which have to be compressed in the loading procedure constitutes another problem.
SUMMARY OF THE INVENTION
The present invention provides a biopsy instrument that can be reliably driven by strong spring means. The invention also provides a means for damping the impact of a stylet or canula in a biopsy instrument. In addition, the invention provides a loading assembly for loading a biopsy instrument, in particular one with a powerful compression spring.
The invention is a biopsy instrument of the aforementioned kind including means for damping oscillations of the first part with respect to the second part arising from the sudden stop of the first part at the end of the first step when hitting a stopper and that of the second part at the end of the second step. On impact the thin-walled tubiform first and second parts become elongated in their axial direction. In general the canula and the finger tube of electropolished steel have very thin walls of from about 0.05 to 0.1 mm thick while their length varies from about 15 to about 20 cm.
In experiments with strong steel coils, oscillations of amplitudes of up to 1.15 mm were observed. In addition, the first and second part do not necessarily oscillate in phase; they may even oscillate in opposite phase. Undampted, the oscillations often damaged the finger, resulting in incomplete severing of the sample or breakage of the finger. The damage occurs by the finger hitting the distal rim of the opening in the tube wall. Thereby the finger is excessively bent or broken.
According to the present invention, oscillation damping means are provided by appropriate design of the stopper stopping the movement of the first part. With reference to the preferred embodiment of the '542 patent, the first stopping element is the plunger stop
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modified according to the teaching of the present invention. By using a powerful steel compression spring the actuator coil
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can be dispensed with. The displacement of the second part in relation to the first part then is caused entirely by inertia.
It is preferred for the steel coil of the biopsy instrument to exert a force of 35 N and more in a compressed state. Particularly preferred is a coil exerting a force of at least 50 N, most preferred of at least 65 N.
A reduction of oscillation by damping so as to keep oscillation of the first part with respect to the second part below 0.4 mm provides a satisfactory result and is preferred. Even more preferred is to keep oscillation within 0.35 mm, even within 0.30 mm and less.
A biopsy instrument according to the invention combines a powerful steel compression spring of the kind described above, an impact damping means to reduce oscillation of a canula with respect to a finger tube slidingly disposed on the canula arising on impact of the canula holder on a stopper, and a design dispensing with the use of spring means to displace the finger tube in a distal direction after the canula has been stopped by the stopper.
The impact damping means of the invention can also be advantageously applied to stop (decelerate) canulas and stylets in biopsy instruments other than that of U.S. Pat. No. 5,655,542, in particular canulas and stylets accelerated by a powerful compression spring, such as one which can be compressed to more than 35 N, preferably more than 50 N, most preferred more than 65 N. The damping means of the invention preferably constitutes an acrylonitrile-butadiene-styrene copolymer (ABS) having a yield tensile strength above 35 Mpa and an Izod impact strength of more than 325 J/m, or any other medical grade polymer or other material meeting these requirements.
The loading assembly of a biopsy apparatus incorporates, in a housing, the biopsy instrument according to the invention includes a loading arm swivellingly attached at its one end to the housing, an intermediate arm swivellingly attached at its one end to the loading arm and at its other end to a catch holding the canula holder during tensioning and in a tensioned position with respect to a tension spring or during compression, or in a compressed position with respect to a compression spring (the latter being preferred). The catch is displaceable in a proximal direction against the resistance of the spring and is adapted to be held there for intentional release. It is obvious that this loading assembly can also be advantageously used for tensioning or compressing spring means arranged for displacement of one or several elements of a biopsy apparatus different from that of the invention.
REFERENCES:
patent: 5156160 (1992-10-01), Bennett
patent: 5188118 (1993-02-01), Terwilliger
patent: 5282476 (1994-02-01), Terwillger
patent: 5535755 (1996-07-01), Heske
Lindgren Mikael
Weilandt Anders
Ascendia AB
Hindenburg Max
Ostrolenk Faber Gerb & Soffen, LLP
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