Needle and needle probe

Details Needle and needle probe Needle and needle probe

1999-06-11

2001-06-05

Getzow, Scott M. (Department: 3737)

Surgery

Diagnostic testing

Structure of body-contacting electrode or electrode inserted...

Reexamination Certificate

active

06241664

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a needle for use in a needle probe for measurement of electrical activity in a patient. The invention also relates to a needle probe comprising such a needle. The invention relates particularly to a needle and needle probe suitable for use in electromyography (EMG).
BACKGROUND OF THE INVENTION
In EMG, the electrical activity of muscle tissue is recorded and interpreted. When a muscle fibre contracts, a potential is generated. Signals from a given muscle, or group of muscles, can be detected by use of an appropriately situated electrode. This is generally achieved by use of a needle probe having a conducting inner core fixed within a conducting outer cannula, the two being insulated from each other by an intervening insulating layer. The conductive parts of the needle are connected to separate pins of a plug for attachment to the recording equipment. Conventionally, this is achieved by use of separate connecting pins attached to the outer cannula and attached to the inner core, which generally consists of a metal wire.
During an EMG procedure, it is often necessary to use such a probe to take a number of measurements for a single patient. However, to reduce risk of infection to patients, it is desirable to dispose of a needle altogether after it has been used for one patient. This is an expensive procedure if conventional needle probes are used, as several manufacturing stages are required to produce the needle probe, which comprises not only a needle but also an electrical plug. It is thus desirable to provide a new design of needle probe in which new needles can be used for each patient without there being a need to replace an expensive part each time that this is done.
A potential line of development is to simplify the disposable part. This however poses difficulty, because of the need to provide reliable electrical connection between the plug of the probe and, separately, the inner core and the outer cannula.
OBJECT OF THE INVENTION
Accordingly the invention provides a needle for a needle probe for measurement of electrical activity in a patient, comprising: an electrically conducting core; an electrically conducting outer cannula; and an insulating element electrically insulating the core from the outer cannula; wherein the needle has a first end for insertion into a patient, and a second end for making electrical connection to a further part of the needle probe, and wherein said second end has a substantially conical or pyramidal shape. Advantageously, said second end is substantially conical and has a semi-vertical angle lying in the range from 20° to 87.5°: alternatively, said second end is substantially pyramidal, preferably pyramidal with a four-sided base, especially where said four-sided base is substantially square and also the angle between each triangular face at said second end and the longitudinal axis of the needle lies in the range from 20° to 87.5°.
It is of benefit if the substantially conical or pyramidal shape of the core is blunted by application of a blunting force to the second end of the needle. Also preferable are that the outer cannula comprises stainless steel and that the insulating layer comprises polyesterimide. Advantageously, the needle further comprises a receiving socket having a conducting inner wall electrically connected to the outer cannula.
There is further provided a needle probe, comprising a needle as indicated above and a further part, wherein the needle is selectively engageable with said further part, said further part having an electrical connector, first means to provide electrical connection between the core and a first connection point of the electrical connector on engagement of the needle with the further part, and second means to provide electrical connection between the outer cannula and a second connection point of the electrical connector on engagement of the needle with the further part. Advantageously, said first means comprises a spring contact probe adapted to press against the core at said second end of the needle when the needle is engaged with said further part of the needle probe, especially where said spring contact probe is adapted to press against said core with a force lying in the range of 52 to 108 gf. Also advantageously, said second means comprises a plurality of resilient fingers adapted to bear against the conducting inner wall of the receiving portion of the needle when the needle is engaged with the further part of the needle probe, especially where said second means comprises six resilient fingers.
The invention therefore solves problems of the prior art by provision of an inexpensive and replaceable needle which can be brought reliably into the necessary electrical contact with a reusable further part of the needle probe.


REFERENCES:
patent: 5170788 (1992-12-01), Blumenfeld
patent: 5452716 (1995-09-01), Clift

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