Surgery – Instruments – Orthopedic instrumentation
Patent
1989-09-20
1991-01-22
Yu, Mickey
Surgery
Instruments
Orthopedic instrumentation
606 99, 606177, A61B 1714
Patent
active
049868268
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.
DISCLOSURE OF THE INVENTION
The present inventor has now 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.
The present invention thus consists in a process for the removal of prosthetic cement from the medullary canal of a patient's 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 and along the said line, (c) forming a substantially planar cutting blade with a cutting edge having a profile substantially corresponding to the profile of the line, (d) forming on the cutting blade depth limiting means, the depth limiting means being spaced from adjacent points on the cutting edge by a distance substantially equal to the depth of the prosthetic cement at the corresponding points along the said plane, (e) inserting the cutting blade into the prosthetic cavity with the blade lying in the said plane and to a depth such that corresponding points on the cutting edge are adjacent corresponding points on the said line, (f) causing the cutting edge to reciprocate, (g) cutting into the prosthetic cement with the blade until the depth limiting means engage with the surface of the prosthetic cavity adjacent the said plane, (h) repeating steps (a) to (g) to form at least one other cut through the prosthetic cement, and (i) removing the segments of prosthetic cement so formed from the medullary canal.
In another aspect the present invention consists in a cutting blade 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, comprising a substantially planar blade having a cutting edge, the 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 cement/bone interface intersected by that plane, and cutting depth limiting means on the blade, the depth limiting means being spaced from an adjacent point on the cutting edge by a distance substantially equal to the depth of the prosthetic cement at the corresponding point along the said plane.
The blade is preferably formed with saw teeth along the cutting edge. The depth limiting means may comprise a rib exte
REFERENCES:
patent: 4502484 (1985-03-01), Giampapa et al.
patent: 4702236 (1987-10-01), Tarabichy et al.
Rooney Kevin G.
Yu Mickey
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