Surgery – Instruments – Orthopedic instrumentation
Patent
1998-08-13
2000-08-15
Smith, Jeffrey A.
Surgery
Instruments
Orthopedic instrumentation
A61B 1717
Patent
active
061029157
DESCRIPTION:
BRIEF SUMMARY
This application is the U.S. national phase application of PCT International Application No. PCT/FR97/00257, filed Feb. 10, 1997.
TECHNICAL FIELD OF THE INVENTION
The present invention concerns instruments used to fit hip prostheses, and in particular to fit the cotyloid implants forming the female part of the hip joint.
The first operation of the procedures habitually employed to fit a cotyloid implant is to mill a hemispherical cavity in the acetabulum, using a hemispherical milling tool. A hemispherical milling tool of this kind is described in the document EP-A-0 704 191 published after the priority date, for example, and includes a hollow substantially hemispherical dome with sharp-edged openings and an open base in which are provided radial spacer members to which a milling tool support can be fixed. The milling tool support is a handle with an external handling tube in which is journalled an operating tube in turn mounted to slide longitudinally on a drive shaft. The end of the drive shaft carries a bayonet bush, with L-shape notches at the end arranged around the terminal edge of the bush and shaped to receive and to retain the radial spacer members of the milling tool. The operating tube is attached to a sliding plate carrying locking lugs. A spring presses the operating tube and the sliding plate against the bayonet bush, in which position the locking lugs close the L-shape notches to trap the radial spacer members inserted in the L-shape notches and thereby lock the milling tool. At its other end, the operating tube has an operating ring, that the user can use to unlock the milling tool by causing the operating tube and the sliding plate to slide away from the bayonet bush.
Other milling tools are described in the documents FR-A-2 281 095, EP-A-0 147 339, EP-A-0 327 509, U.S. Pat. No. 4,712,951.
The tools described in all these documents have only a milling use.
The second operation is to fit a test piece into the bone cavity hollowed out by the milling tool, after removing the milling tool. The test piece is the same shape as the final implant to be fitted into the cavity subsequently. The test piece is then removed and the cotyloid implant cemented in place, for example with the help of an impact tool as described in the document EP-A-0 470 912.
In another operation procedure, described for example in the document EP-A-0 051 359, after a first operation identical to the formation of the hemispherical cavity in the bone using a milling tool, a metal cup is forcibly inserted into the cavity. A female test core is introduced into the metal cup, constituting an interface between the metal cup and a femoral prosthesis head. The test core is removed and the final core finally clipped into place.
A first drawback of these techniques is the relative complexity of the instruments, since dedicated test parts are required. Another drawback of these techniques is that the stability of the final joint, conditioned by the orientation of the implant, remains random.
SUMMARY OF THE INVENTION
Accordingly, a first problem to which the invention is addressed is that of simplifying the instruments, enabling test manoeuvring of the joint before final fixing of the prosthesis, without using separate dedicated test parts.
Another problem to which the invention is addressed is that of significantly reducing the residual risks of dislocation of the final joint. The basic idea of the invention is that these residual dislocation risks are the result of the difficulty of checking and fixing the orientation of the final joint relative to the pelvis and the femoral prosthesis of the patient. The invention accordingly provides means for the easy and effective selection, checking and fixing of the orientation of the final implant relative to the pelvis and to the femoral prosthesis of the patient, faithfully reproducing the position assumed by the parts during tests.
To achieve the above and other objects, instruments in accordance with the invention for fitting hip prostheses comprise a milling tool support and at lea
REFERENCES:
patent: 4023572 (1977-05-01), Weigand et al.
patent: 4712951 (1987-12-01), Brown
patent: 5100267 (1992-03-01), Salyer
patent: 5462548 (1995-10-01), Pappas et al.
patent: 5658290 (1997-08-01), Lechot
International Search Report mailed Apr. 22, 1997.
Bresler Franck
Catier Philippe
Caudal Philippe
Francois Jean-Marie
Godefroy Jean
Advanced Technical Fabrication
Robert Eduardo C.
Smith Jeffrey A.
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