Artificial condyle for the human hip joint

Details Artificial condyle for the human hip joint Artificial condyle for the human hip joint

2000-01-11

2001-11-06

Isabella, David J. (Department: 3738)

Prosthesis (i.e., artificial body members), parts thereof, or ai

Implantable prosthesis

Bone

Reexamination Certificate

active

06312471

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an artificial condyle for use in a human hip joint, having a spherically constructed joint shell which has a radius of curvature R
1
and a curvature midpoint M
1
and, in the cross-section, a concave section contour. At least in its region which articulates in the joint shell, this condyle has a joint surface which is spherically shaped such that, in the state in which it is inserted in the hip shell, in a longitudinal plane extending through the midpoint M
1
of the hip shell, a radius R
K1
=R
1
(R
1
being equal to the radius of the hip shell) is formed which has a midpoint M
K1
coinciding with the midpoint M
1
, and, in a transverse plane perpendicular to the longitudinal plane, extending through the midpoint M
K1
, a radius R
K2
<R
K1
exists which has the midpoint M
K2
, and, in the transverse plane, a stable dimeric joint chain is formed, in the case of which the joint axis path of the midpoints M
K1
and M
K2
has a radius R=R
K1
−R
K2
, R being a positive value.
From German Patent Document DE-PS 39 08 958, an artificial joint for replacing the human hip joint is known, which consists of at least two artificial joint parts with spherical functional surfaces which move with respect to one another, the curvature conditions of the functional surfaces having a circular section contour being constructed convexly/concavely with respect to one another such that their centers are rotation M
1
and M
2
are situated inside the joint part with the convex functional surface and a pressure distribution body is arranged as a third artificial joint part between the two functional surfaces. The embodiment of this artificial joint is such that a stable configuration is created, a pressure force along the connection line of the two curvature midpoints leading to a stable positional state. The pressure distribution body aligns itself between the two joint parts such that it cannot move out laterally. This joint is constructed like a joint chain with two joint axes; that is, it is a so-called dimeric joint chain, in which case, because of the special embodiment, a dimeric joint chain exists which is resistant to pressure. This known artificial hip joint permits a movement in five degrees of freedom for a body coupled thereto or for a limb. This is achieved in that the midpoint of the condyle and the midpoint of the joint socket do not coincide and, as the result of their constant distance, in a frictional connection, they form the force-transmitting dimeric chain. As the result of the use of the additional pressure distribution body, the manufacturing costs for this joint are higher than for artificial hip joints consisting of only two joint parts. Furthermore, the placing of this hip joint consisting of three parts in the human body requires higher expenditures than the placing of a two-part hip joint.
From European Patent Document DE-A-0 590 241, an artificial shoulder joint having a condyle is known which has a functional surface which is convex at least in its region which articulates in the joint shell.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an endoprosthesis for the hip condyle of a human hip joint, in the case of which an additional pressure distribution body can be eliminated, but a turned-over dimeric chain which is resistant to pressure can be implemented in the main functional plane, which chain always has the same size when the main functional plane is swivelled.
According to the invention, this is achieved in that, in the case of a condyle of the above-mentioned type, the radius R
K1
is constant along the whole circumference.
According to the invention, this condyle is inserted such into the joint shell while forming an artificial hip joint or a partially artificial hip joint that the transverse plane of the condyle coincides with the main functional plane of the joint. In this case, the longitudinal plane of the condyle according to the invention is disposed perpendicularly on the main functional plane. The radius discrepancy between the radius of the spherical socket with the concave functional surface which is circular in its cross-section and the smaller radius R
K2
will then define in the main functional plane a turned-over stable dimeric joint chain, in which case the radius discrepancy according to the invention may advantageously amount to between 0.5 to 10 mm. Because of the embodiment of the condyle according to the invention, in all functional positions of the condyle in the joint shell, a linear contact can be achieved between the condyle and the joint shell. The construction according to the invention permits that, in the case of limbs which are connected with a joint equipped with a condyle according to the invention, the main functional plane can be swivelled and it is ensured that a dimeric chain always exists in it which has the same size. Because of the embodiment according to the invention, perpendicularly to the main functional plane, no dimeric chain or only a minimal dimeric chain (up to maximally {fraction (1/10)} of the dimeric chain existing in the main functional plane) exists in the original position.
Additional advantageous embodiments are also described hereinafter.


REFERENCES:
patent: 4129902 (1978-12-01), Harmon
patent: 5383936 (1995-01-01), Kubein-Meesenburg et al.
patent: 5556432 (1996-09-01), Kubein-Meesenburg et al.
patent: 5728172 (1998-03-01), Krieger
patent: 5738686 (1998-04-01), Kubien-Meesenburg et al.
patent: 5800370 (1998-09-01), Kubein-Meesenburg et al.

Affiliated with

Also associated with

Rating

Artificial condyle for the human hip joint does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Artificial condyle for the human hip joint, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Artificial condyle for the human hip joint will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2576407