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This invention relates to neurological pins. They are used for testing objective sensation; for example, awareness of the difference between sharp (pain) and blunt by comparison between a sharp point and a rounded end on the patient's skin. These are provided at opposite ends of the pin.
The most commonly used neurological pin consists of a relatively narrow rod, of which one end is sharpened to provide the point, and the other end carriers a spherical body for providing the rounded end for blunt sensation. It is used by grasping it between thumb and forefinger, pincer like, halfway between its two ends and applying one or the other to the patient's, asking the patient, whose eyes are closed or at least is not watching, to identify which end is being used. The clinician's hand has to invert or switch the pin through 180° to change ends. Pressure is applied manually and may vary. Although not as sharp as a needle, the sharp end of the pin is still easily capable of penetrating skin, especially in the hands of the inexperienced, the fatigued or the over zealous.
The traditional neurological pin has been looked upon as a permanent piece of equipment, traditionally to be found in the lapel of the hospital doctor's coat and the consultant's jacket or in the family doctor's bag.

It would be used from patient to patient as the hospital practitioner moves form bed to bed, or as the GP moves from house to house. The pin is placed back in its place of storage with as much afterthought as the stethoscope. It may be used by the practitioner on multiple occasions in one day. There are obvious risks involved in such multiple utilisation of the same piece of equipment. The multiple use of an item which can potentially puncture the skin involves a particular risk of cross-infection.

The present invention is directed at a neurological pin, broadly of the traditional type as described above, but adapted to minimise the risk of the patients' skin being puncture during its use. According to the
invention, a neurological pin comprises a shaft with a sharp end and a blunt end wherein the sharp end is surrounded by an element defining an annular surface traversing the axis of the shaft. The blunt end is normally defined by a spherical body and typically, the diameter of the sphere will be substantially equal to that of the annular surface. The element defining the annular surface conveniently is frusto-conical, tapering towards the blunt end.
In preferred embodiments of the invention the annular surface defines a plane from which the sharp end of the shaft projects. Normally, the annular surface is substantially circular, and the sharp end projects beyond the plane of the annulus by a distance not exceeding the radius thereof. The element may have a substantially planar surface defined by the annular surface and normally perpendicular to the shaft, from which the sharp end of the shaft projects. While these arrangement are currently preferred, the disposition of the sharp end or point relative to the annular surface can be varied. For example the annular surface might define a plane substantially containing the point at the sharp end of the shaft. In another example, the annular surface could define a plane traversing the axis of the shaft beyond the sharp end thereof.
The element defining the annular surface at the sharp end of the pin shaft is usually substantially rigid, and normally fixed to the shaft. It may be formed integrally therewith.
The sharp end of the pin shaft will define a point at its tip. The actual shape of this point can be significant. I have found that better; ie, better assessable responses, can be achieved if the actual tip is flattened. The area of the flattened tip will be small, normally in the range 6.2 x 10"4 mm2 to 0.04mm2. A typical area is 0.025mm2. The shape of the tip area may vary, but is preferably substantially square.
Neurological pins of the invention offer a number of benefits. They may be made of plastics material in a moulding process. They can be sterilised at the point of manufacture or of packaging, and may be kept so sterilised up to the up to the point of use. They can be inexpensive to manufacture, and therefore made disposable. Handling and use can be facilitated by the enlargements normally present at both ends, and further assisted by the provision of a friction area midway down the shaft. Most significantly perhaps, the provision of the annular surface at the sharp end of the shaft can substantially eliminate the risk of piercing a patient's skin during normal use, while facilitating the
application of consistent pressure on the skin during use.

The invention will now be described by way of example and with reference to the accompanying drawings wherein:
Figures 1 and 2 are side views of two embodiments of the invention;
Figure 3 is an enlarged detail side view of the sharp end of the pin shown in Figure l or in Figure 2 showing the point thereat; and
Figure 4 is a view taken in the direct of arrow A in Figure 3.

The neurological pin shown in Figure 1 comprises a shaft 2 at one end of which is formed a solid sphere 4, and at the other end is formed a point 6 which projects from an enlarged section 8. The entire pin can be moulded in a suitable plastics material such as
polythene or ABS, and is typically around 6cms long.

The enlarged section 8 defines an annular surface 10, better shown in Figures 3 and 4, in a plane which traverses the axis of the shaft 2. The diameter of the annular surface 10 is substantially equal to that of the sphere 4 at around 5mms.
The pin shown in Figure 2 differs from that of Figure 1 in that a central position 12 of the shaft 2 is formed with a knurled or roughened section bounded by two annular projections 14. This section can make it easier to hold the pin, inhibit or control slippage, and facilitate pivoting or inverting it in use to apply alternate ends to a patient's skin.
In the detail views of Figures 3 and 4, the shape and configuration of the point 6 is clearly shown projecting from the plane defined by the annular surface 10. The surface 10 actually extends around a recess formed in the section 8, and the base 16 of the point 6 protrudes from the floor 10 of the recess. This base 16 is of uniform circular cross-section up to the plane defined by the annular surface 10. The upper section 20 of the point has been machined to form four planar sides 22 which converge towards a flat surface 24 at the distal extremity. The shape of the flat surface is thus square, with an area typically up to 0.025mm2. The configuration of the point at the sharp end of the shaft is not critical, but a flat surface of the type
illustrated is preferred as it has been found to provoke a particularly effective and assessable response from a patient when applied to the skin.
The enlarged section 8 serves the effective
function of restricting the depth to which the point 6 can press into a patient's skin. While the formation of the recess is sometimes preferred, in modification of the configuration shown in Figures 3 and 4 the recess is filled, and the surface 10 is not strictly annular, but circular.
While the point 6 of the pin shown in the drawings projects from the plane defined by the annular surface 10, in some embodiments of the invention, the distal extremity can be located in the plane, or even on the other side thereof; ie, within the recess, if more sensitive responses are under review.
The enlarged section of the shaft is shown as an integral part of the shape. However, it may be a separate element, and in some case it can be mounted for axial movement along the shaft to alter the extent to which the distal extremity of the point projects or fails to project from the plane of the annular surface.

In most cases, the enlarged section will be
substantially rigid, but a degree of flexibility can be desirable in some circumstances. Nevertheless, it is important that the basic function of the annular
surface, to provide some protection for, and. define a plane relative to the point, is preserved.
Neurological pins according to the invention can be easily and economically manufactured and packaged, and can be sterilised for single patient use and subsequent disposal. They are thus particularly beneficial in terms of hygiene and cleanliness. The enlarged section and the annular surface thereon ensures that consistent and accurate tests can be performed, with minimal risk of skin penetration. It also reduces the chance of a practitioner injuring his or herself accidentally, as the full effect of the sharp end of the shaft, which is itself restricted by the annular surface, is only available when the shaft is substantially perpendicular to the skin.