Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1991-01-29
1992-12-15
Isabella, David
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
606 96, 606 80, A61F 228
Patent
active
051712776
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an improved process for the removal of prosthetic cement from the medullary canal of a patient's long bone during the replacement of a joint prosthesis, and to a cutting blade for use therein.
BACKGROUND ART
The present inventor has proposed in PCT patent application PCT/AU86/00321 that the removal of prosthetic cement from the medullary canal of a patient's long bone can be facilitated during a joint prosthesis replacement operation by making two or more longitudinally extending cuts through the bone cement after removal of the old prosthesis. These cuts divide the originally tubular bone cement into a number of segments which may be conveniently levered away from the associated bone and removed from the medullary canal. In the aforementioned patent application means were described for forming such cuts through the prosthetic cement substantially without cutting into the underlying bone. These means included guide means to guide a saw blade along the line of intersection of a longitudinal plane extending through the bone, the prosthetic cement and a prosthetic cavity therein and a bone/prosthetic cement interface intersected by the plane.
The present inventor has also discovered that these guide means may be dispensed with if a cutting blade with a suitably profiled cutting edge is provided with depth limiting means which can bear against the surface of the prosthetic cavity adjacent the said plane to limit the depth to which the blade can cut into the prosthetic cement along the plane to the depth of the prosthetic cement along that plane (see PCT/AU88/00019).
It has been now found by the inventor that there may be some difficulty in forming appropriate depth limiting means on the blade and that if such means are formed on the blade that the blade is then dedicated to a single cut on a single patient and cannot be reused. It has also been found that as the blade is quite long but necessarily quite thin there may be difficulty in applying sufficient cutting pressure to the blade adjacent its tip to effectively cut through the full depth of the cement.
DISCLOSURE OF THE INVENTION
The present invention thus consists in a process for the removal of prosthetic cement from the medullary canal of a patients long bone during replacement of a joint prosthesis, comprising the steps of:
a) determining the profile of a line of intersection of a plane, which extends longitudinally through the bone, the prosthetic cement and a prosthetic cavity therein, and a cement/bone interface intersected by that plane,
b) determining the thickness of the prosthetic cement in the said plane at least at selected points along the said bone,
c) forming or selecting a substantially planar cutting blade with a cutting edge having a profile substantially corresponding to the profile of the line,
d) inserting the cutting blade into the prosthetic cavity with the blade lying in the said plane, the cutting edge directed towards the said cement/bone interface, and to a depth such that corresponding points on the cutting edge are adjacent corresponding points on the said line,
e) causing the cutting blade to reciprocate,
f) inserting into the prosthetic cavity between a non-cutting edge of the blade and a wall of the prosthetic cavity spaced from the said cement/bone interface a guide member adapted to urge the cutting edge of the blade into the prosthetic cement towards the said cement/bone interface but substantially not beyond it,
g) repeating steps (e) to (f) to form at least one other cut through the prosthetic cement, and canal.
In another aspect the present invention consists in a kit of parts for use in the removal of prosthetic cement from the medullary canal of a patient's long bone during the replacement of a joint prosthesis, the kit of parts comprising cutting edge having a profile substantially corresponding to the profile of the line of intersection of a plane, which extends longitudinally through the long bone, the prosthetic cement and a prosthetic cavity therein, and a
REFERENCES:
patent: 4222382 (1980-09-01), Antonsson et al.
patent: 4781181 (1988-11-01), Tanguy
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