Surgery – Truss – Perineal
Patent
1987-06-29
1989-07-11
Hafer, Robert A.
Surgery
Truss
Perineal
128 92VP, 128317, A61B 1732
Patent
active
048461610
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND ART
The present invention relates to a method and apparatus for the removal of prosthetic cement from the bone of a patient undergoing total joint replacement, particularly total hip joint replacement.
Some prostheses, used in total hip replacements especially those used in early procedures, included long stems which were embedded in prosthetic cement within a suitable cavity within the bone. Loosening of such prostheses requires that they be removed and replaced. Many such prostheses last approximately five to ten years before loosening. The major problem in the removal and replacement of the original prosthesis is found in the removal of the prosthetic cement which is normally polymethylmethacrylate.
The removal of the cement is usually effected with hammer and chisel. The surgeon is working within a live bone, down a narrow curved cylindrical cavity with poor lighting and visibility. Also used, on some occasions, are tungsten burr drills, assorted reeming drills, more recently experimental laser cutting devices, and alternative surgical techniques which involve making a "window" in the bone in a position corresponding to where it is thought the prosthetic cement finishes and then removing the cement from below.
These techniques are poor in that they are of long duration and generally place the live bone in risk of damage. Damage, such as facture, can be a serious problem because many of the patients are elderly.
DISCLOSURE OF THE INVENTION
In one broad form the present invention may be said to provide a template profiled so as to correspond to the profile of the line of intersection of a generally longitudinal pre-selected plane of a joint prosthesic cavity and the associated prosthetic cement/bone interface of a patient.
An alternative broad form of the invention can be said to provide a method of forming a guide means for use in removing prosthetic cement from a bone of a patient comprising the steps of determining the profile of the prosthetic cement/bone interface along a predetermined line running longitudinally of the bone and forming said guide means adapted to guide a suitable cutting means such that it cuts through the cement along said lines substantially without cutting into the bone.
Broadly speaking the invention can also be said to provide a method of producing a template, such as the template described above, including the steps of:
scanning the patient in the area of the joint prosthesis so as to obtain a profile of the prosthetic cement/bone interface at its intersection with the longitudinal pre-selected plane of the cavity; and
feeding the profile into a machine which, in response thereto, forms the template being profiled correspondingly to the profile of the line of intersection of the pre-selected plane and the cement/bone interface.
Preferred apparatus of the invention can be said to comprise:
the template as described above;
a linear saw guide being rigidly attached to, or integral with, the template;
a saw adapted for reciprocating cutting action and traversable along the guide for linear advancement of the cutting action; and
a template follower urging the saw to cut along a path being substantially the line of intersection of the pre-selected plane and the cement/bone interface.
In a particular preferred embodiment the template may be the base of a groove of a saw guide.
In another particular preferred embodiment the template may be the saw which is advanced transversely of the guide, in which case no template follower is required.
Another broad form of the invention may be said to provide a method of longitudinally cutting prosthetic cement in a bone of a patient, using the above-described apparatus, and comprising:
positioning the guide and template fixedly relative to the prosthetic cavity approximately in the longitudinal pre-selected plane associated with the template profile;
introducing the saw cooperatively to the guide;
commencing reciprocating cutting action of the saw, and
advancing the saw such that a groove is cut into the prosthetic cement to a dep
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patent: 4248232 (1981-02-01), Engelbrecht et al.
patent: 4399813 (1983-08-01), Barber
patent: 4612922 (1986-09-01), Barber
patent: 4617930 (1986-10-01), Saunders
patent: 4696292 (1987-09-01), Heiple
patent: 4702236 (1987-10-01), Tarabichy et al.
Hafer Robert A.
Rooney Kevin G.
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