Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1995-11-17
1998-04-14
Isabella, David
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
A61F 238
Patent
active
057386862
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an artificial joint, especially an endoprosthesis for the joint which connects the patella to the thigh, consisting of two joint parts with curved joint surfaces which move with respect to one another.
From German Patent Application No. P 3,908,958.4, an artificial joint is known for the replacement of human joints which consists of at least two joint parts with spherical functional surfaces which move with respect to one another. The curvature ratios of the functional surfaces which have a circular section contour, are convex-convex, convex-concave, or concave-concave with respect to one another and the joint geometry is determined by a link chain with two articulated axles, dimer link chains, which run through the centers of rotation of the functional surfaces and is defined by the centers and their distance. Here, the joint surfaces are designed in a spherical shape so that joint movement with five degrees of freedom is possible.
Nevertheless, it has been shown that such a joint is not suitable to approximate the special joint function as it is present in the human patella joint.
The object of the present invention is to create an artificial joint which is suitable to replace the human patella joint whereby the natural relationships are to be essentially reproduced.
According to the invention, this is achieved by an artificial joint consisting of two joint bodies which move with respect to one another, one joint body with two attached joint heads and one joint body with two attached joint sockets which have toroid joint surfaces in each case which have functional surfaces, in planes which are vertical with respect to one another--a longitudinal plane and a corresponding transverse plane, with different circular section contours, whereby the curvature relationships of the functional surfaces of each of the planes are either concave-convex or convex-convex, and the joint geometry of the functional surfaces which come into contact with one another is determined in each of the two functional planes by a link chain with two articulated axles, dimer link chains, which run through the middle point of the curvature of the functional surfaces and are established by them.
Thus, the invention is based on the knowledge that the joint tracks of the human patella joint can be replaced by toroid-shaped surfaces in each case of the section contours in the planes which are vertical with respect to one another.
The pressure stresses which occur in this case can be controlled by use of materials with appropriate strength. Thus, an artificial joint is created which has a particular freedom of movement in one joint plane and which simultaneously has high mechanical stability with a great range of variation for adaptation to individual situations as well as an additional ease of mobility in the transverse plane vertical to the longitudinal plane towards the lateral, due to special structural features.
Advantageous embodiments of the invention are to be found in the subclaims.
The invention is explained in more detail on the basis of the embodiment examples presented in the attached drawings. Shown are:
FIG. 1, a perspective view of a joint body according to the invention with two attached joint heads,
FIG. 2, a perspective view of a joint body according to the invention with two attached joint sockets,
FIG. 3, a longitudinal cut through a joint according to the invention in the area of the lateral joint part,
FIG. 4, a cross section according to cut line IV--IV in FIG. 3 in the transverse plane,
FIG. 5, a longitudinal cut through a joint according to the invention in the medial joint part,
FIG. 6, a cut along cut line VI--VI in FIG. 5 in the transverse plane,
FIG. 7, a longitudinal cut through a joint according to the invention composed of the joints according to FIGS. 3 and 5.
FIG. 8, a perspective view of another embodiment form of a joint body according to the invention with two attached joint sockets.
In FIG. 1, a perspective representation of a part of the hip, femur, is shown with hip j
REFERENCES:
patent: 3816855 (1974-06-01), Saleh
patent: 3878566 (1975-04-01), Bechtol
patent: 4151615 (1979-05-01), Hall
patent: 4178641 (1979-12-01), Grundei et al.
Kubein-Meesenburg Dietmar
Nagerl Hans
Isabella David
Theusner Joachim
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