Surgery – Instruments – Orthopedic instrumentation
Patent
1997-12-22
2000-01-18
Buiz, Michael
Surgery
Instruments
Orthopedic instrumentation
A61B 1758, A61B 1760
Patent
active
060154136
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a device for the extraction of screwthreaded wires for osteosynthesis at the end of treatment.
As is known from German Patent Application No. P4309707 published in the file of DE-44,06,374-C, screwthreaded wires are an improvement on the Kirschner's wires used in orthopaedic surgery for compacting bone fragments onto the main bone or in the reconstruction of small fractured bones. Unlike Kirschener's wires, screwthreaded wires are not completely smooth: instead, the end that is to be inserted into the bone is threaded, and the diameter of the thread is less than that of the remaining cylindrical shank of the wire. There is thus a shoulder at the point where the screwthreaded part ends and the smooth part begins. This shoulder serves to exert a compressive action on the bone fragment towards the part of the bone from which said fragment has become detached, when the screwthreaded wire is screwed in.
Depending on the characteristics and dimensions of the bone fragment and of the bone from which said fragment has become detached, screwthreaded wires of different diameters and with different thread diameters are used, as for example 1.5-mm, 2.0-mm, or 3.0-mm diameter wires with thread diameters of 1.2 mm, 1.6 mm or 2.2 mm respectively, and with different lengths of the threaded part.
When the treatment is finished, that is to say when the bone fragment has become firmly fixed to the bone from which it was detached, the screwthreaded wire or wires must be removed.
A known method for the extraction of screwthreaded wires for osteosynthesis involves using ordinary forceps consisting of two levers giving mechanical advantage which are held by their longer arms and enable a gripping couple to be produced in the two jaws provided on the shorter arms.
During the operation of extracting a wire with forceps the following problem can arise.
Since the operator (the orthopaedic surgeon) is wearing elastic gloves his grip may relax as a result of slight slippages between his hand and the tool. This produces a relaxing of the effort applied to the levers and consequently a reduction in the gripping forces, as a result of which the jaws may slip on the end of the wire is to be extracted.
Also known is a wire-extracting device consisting of a spanner in which the opposite end from that on which the grip is formed contains a cylindrical seat in which the cylindrical end of the wire to be extracted is accommodated. In the side wall of said cylindrical cavity is a set screw whose axis is perpendicular to the axis of said cylindrical cavity. This screw can be driven from the outside by a hexagon socket wrench in order to clamp the end of the wire to be extracted.
The problem with the known extractor device is that it cannot be used for removing a wire whose end is completely below the skin of the patient from whom the wire is to be extracted, The cause in order to clamp the cylindrical end of the wire to be extracted in this instrument, it is necessary to turn said set screw, and since the latter must grip the lateral surface of said end, it would be necessary to work underneath the external surface of the skin, a position which is virtually inaccessible.
During the operations of removing the wire, the known extractor devices must be turned together with the wire itself, and in cases in which the end of the wire is deep below the external surface of the skin there could be accidental impact of the instrument on the soft tissues surrounding the end of the wire in question.
U.S. Pat. No. 4,438,769 discloses a device for holding, driving and withdrawing a medical staple, comprising a staple retaining member having spaced and opposed portions normally and inherently urged away from each other and being adapted to receive and retain a medical staple therebetween, the spaced and opposed portions having force application surfaces to which force may be applied to overcome the normal and inherent urging away force to releasably retain a medical staple therebetween; and a force applying and force reduction
REFERENCES:
patent: 5476467 (1995-12-01), Benoist
patent: 5531751 (1996-07-01), Schultheiss et al.
Faccioli Giovanni
Pennig Dietmar
Venturini Daniele
Bui Vy Q.
Buiz Michael
Orthofix S.r.l.
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