Ball-and-socket joint, particularly a prosthetic hip joint
OwnerAaron L. Marlowinventor
Life of this patent
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Abstract
A ball-and-socket joint has a race with bearing balls interposed between the head and the socket of the joint. The race is secured to the head. In use as a prosthetic hip joint, the formation of metallic debris is reduced or completely eliminated thus eliminating or at least reducing the occurrence of the need for corrective surgery. The hip joint is of an unconstrained type which often enables correction of an accidental dislocation of the joint without surgery.
Claims19
An antifriction insert adapted for placement over a generally spherical head of a ball-and-socket joint including a stem portion to one end of which the head is secured, to provide a rolling ball interface between the head and a cavity of a socket of the joint, said insert comprising:
- (a) a generally hemispherical race portion, said race portion holding a plurality of spaced apart bearing balls freely rotatable relative to the race portion, said balls being held in the race portion such that radially outer portions and radially inner portions of the bearing balls project radially outwardly and radially inwardly of the race portion, respectively;
- (b) said radially outer portions of the bearing balls being in general coincidence with a generally hemispheric, outer reference surface having a major radius;
- (c) said radially inner portions of the bearing balls encompassing a generally hemispheric, inner reference surface having a minor radius;
- (d) said major radius being generally equal to that of the socket of an associated joint;
- (e) said minor radius being generally equal to that of the head of an associated joint;
- and
- (f) retainer means fixedly securable to said race portion and movably engageable with the head of an associated joint to encompass a circular locus at a location of the head, said locus being axially spaced from:
- (i) said race portion,
- (ii) an equatorial portion of the head, and
- (iii) a minimum diameter portion of the head, the diameter of said minimum diameter portion being equal to the diameter of the head at the stem portion of an associated joint;
- whereby, on securement of the retainer means to the race portion over the head of an associated joint, the combined race portion and retainer means encompass more than one-half of the head while permitting free movement in common of the combined retainer means and race portion about the head.
A kit for producing an artifical ball-and-socket hip joint, said kit comprising:
- (a) a head adapted to be sucured, or secured, to one end of a femoral portion of the hip joint, said head defining a spherical surface;
- (b) a generally hemispherical, hollow, acetabular socket bearing adapted for implanting in a patient's acetabulum;
- (c) a generally hemispherical race portion, said race portion holding a plurality of spaced apart bearing balls freely rotatable relative to the race portion, said balls being held in the race portion such that radially outer portions and radially inner portions of the bearing balls project radially outwardly and radially inwardly of the race portion, respectively;
- (d) said radially outer portions of the bearing balls being in general coincidence with a generally hemispherical, outer reference surface having a radius generally corresponding to that of the acetabular socket bearing;
- (e) said radially inner portions of the bearing balls encompassing a generally hemispheric, inner reference surface having a radius generally corresponding to that of the head;
- and
- (f) retainer means fixedly securable to said race portion and movably engageable with the head to encompass a circular locus of said spherical surface, said locus being axially spaced from:
- (i) said race portion,
- (ii) an equatorial portion of the spherical surface, and
- (iii) a minimum diameter portion of the spherical surface equal to the diameter of the head at said femoral portion;
- whereby, on securement of the retainer means to the race portion over the head of an associated joint, the combined race portion and retainer means encompass more than one-half of the head while permitting free movement in common of the combined retainer means and race portion about the spherical surface.
Dependencies are inferred from the claim text.