Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1982-12-01
1986-01-07
Apley, Richard J.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
128 92C, 128 92CA, 128 92BC, 128 92B, 623 20, 623 22, A61F 100, A61F 504
Patent
active
045625980
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an endoprosthesis (joint prosthesis) frequently employed in orthopedic surgery. The prosthesis can be used for all types of endoprostheses, although the embodiment described hereinafter refers exclusively to a hip joint prosthesis.
The most varied indications may make it appear advisable to implant a substitute joint in a patient. Conventional endoprostheses, however, have only a service life of about five to eight years. The most frequent type of failure of such prostheses is their coming loose from the cement quiver or, for prostheses which have been inserted without cement, from the outer covering of the femur. The conventional endoprosthesis that has been inserted without cement has the drawback that the shaft extending into the bone (e.g. the femur) is insufficiently adapted to the shape of the marrow cavity intramedullary cavity due to the requirement for production in a certain number of sizes and the lack of a further curvature out of the single curvature plane (no distinction made between right and left). The resulting point contacts lead to locally very high transverse stresses and stress relief of the outer covering in the longitudinal directon and thus to resorptions in the upper region of the attachment of the prosthesis. The cemented endoprosthesis, although form-lockingly anchored in the cavity, constitutes, in its junction between prosthesis shaft and cement quiver, a component which is more resistant to bending by about one power of ten than the outer covering tube of the bone. The result is a reorientation of the flow of forces in the outer covering with large-area stress relief and local overstressing transverse to the orientation of the fibers.
SUMMARY OF THE INVENTION
Consequently, it is the object of the invention to provide a joint prosthesis which can be adapted individually in shape and rigidity distribution to the outer covering of the bone without significant compromises and which is able to absorb statically as well as dynamically the forces required for the general sequence of movement and to introduce them into the outer covering in a physiological manner so that there is less chance of loosening than with conventional prostheses.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the joint prosthesis for insertion in a bone cavity comprises an adapter; a hollow, flexible prepreg member of hardenable material secured to the adapter; a hollow inflatable pressing member disposed in the prepreg member; and an arrangement for introducing fluid into the pressing member for inflating the same for causing the prepreg member to conform to the walls of the bone cavity.
It is noted that the term "prepreg" is the customary name given to fiber structures (glass, cabon, aramide or the like) which have already been wetted with a matrix plastic but have not yet hardened, i.e. whose polymerization process must still be initiated by extraneous influences such as heat, ultraviolet radiation, light, ultrasound or the like. The matrix plastic employed in this case is a plastic which, in its liquid form, is brought into contact with fibers or fabrics and, after hardening, produces a bond between the individual fibers. The structure contains these fibers in layers one on top of the other or in the form of oriented woven fabrics for the purpose of producing precisely defined, oriented rigidity as well as strength in the resulting laminate produced in conjunction with suitable matrix plastics.
Preferably, the prepreg member comprises specially cut strips which are fastened at their ends and take over the supporting and force introducing function of the prosthesis and which are hardened only during the surgery phase by the use of ultraviolet radiation or ultrasound and are thus adapted exactly to the outer cover of the bone. The force transmission to a joint head, for example an aluminum oxide ceramic sphere, is effected by means of a specially shaped
REFERENCES:
patent: 3643656 (1972-02-01), Young et al.
patent: 3681787 (1972-08-01), Perras
patent: 4274163 (1981-06-01), Malcom
patent: 4357716 (1982-11-01), Brown
patent: 4399814 (1983-08-01), Pratt, Jr. et al.
Apley Richard J.
Isabella David J.
MECRON medizinische Produkte GmbH
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