Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1997-08-06
1999-03-30
Milano, Michael J.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
A61F 236
Patent
active
058882065
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a modular joint prosthesis having a shaft part insertable into a tubular bone and a head part, adjoining the shaft part, and having a joint connection element, the longitudinal axes of the shaft part and joint connection element forming an obtuse angle.
Shaft prostheses of this kind are produced in various shapes and sizes, to assure that the needs of a given patient can be optimally met.
International Patent Application WO 85/05027 discloses an artificial joint system, in particular a hip joint prosthesis for cementless implantation, which has a shaft part that can be introduced into the upper thigh of the patient and a joint connection element connected to this shaft part. In the proximal region of the shaft part, a threaded sleeve is provided, into which the joint connection element is screwed; the longitudinal axis of the shaft part and the longitudinal axis of the joint connection element are inclined relative to one another. Accordingly, the joint connection element has a threaded peg, which on its proximal end is connected to a conical shaft part for receiving the ball of the joint. The process of screwing the prosthesis in is concluded once the conical shaft part of the joint connection element rests firmly on the proximal region, prepared for the implantation, of the upper thigh bone.
However, the above-described version has the disadvantage that only a complete replacement of the joint, including the ball of the joint, can be done with it.
SUMMARY OF THE INVENTION
Given the deficiencies of the prior art, it is the object of the invention to create a modular hip prosthesis shaft of the generic type described at the outset, whose structural design makes it simple even to replace component elements in the region of the joint, to allow adaptation to variously advanced stages of disease.
The above and other objects are accomplished according to the invention by the provision of a joint prosthesis, comprising: a shaft part insertable into a tubular bone and having a first longitudinal axis; a head part adjoining the shaft part and including a sleeve region which has a through bore that has a second longitudinal axis which forms an obtuse angle with the first longitudinal axis; and a joint connection element having a shaft for being received in the through bore of the head part, the through bore of the head part being adapted to a cross section of the shaft of the joint connection element, the joint connection element having a third longitudinal axis forming essentially the same obtuse angle with the first longitudinal axis that the second longitudinal axis makes with the first longitudinal axis when the joint connection element is introduced in the through bore, the shaft of the joint connection element including a cylindrical region that is expandable by a spreader device to lock the joint connection element in place in the through bore of the head part.
The invention encompasses the recognition that to preserve the natural ball of the joint in a modular prosthesis, one additional, alternatively usable head part is favorable that is provided with a bone screw in the direction of the neck of the ball of the joint that can be screwed into the separate, natural ball of the joint. Thus the joint with its natural parts, the ball and socket of the joint, may possibly be preserved for a still longer time. The head part can then later be replaced if needed, at little effort, without stressing the bone substance of the patient and without loosening and removing the prosthesis seat.
With the provisions of the invention, the prosthesis described can initially also replace a conventional hip screw, of the kind that is often inserted in the region of the femur in the event of fractures. Later reoperation is then facilitated in the sense that to obtain a full prosthesis, only the head part of the modular shaft prosthesis needs to be replaced with a head part that has an artificial ball for the joint.
The modular hip prosthesis shafts according to the inventio
REFERENCES:
patent: 3683421 (1972-08-01), Martinie
patent: 4693724 (1987-09-01), Rhenter
patent: 4795473 (1989-01-01), Grimes
patent: 5507830 (1996-04-01), DeMane
patent: 5591233 (1997-01-01), Kelman
Fischer Hans-Joachim
Kranz Curt
Lob Gunter
Steur Gerd
Kinberg Robert
Merck Patent GmbH
Milano Michael J.
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