Hip replacement prosthesis

Details Hip replacement prosthesis Hip replacement prosthesis

1999-10-29

2001-06-19

Smith, Jeffrey A. (Department: 3732)

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

Implantable prosthesis

Bone

Reexamination Certificate

active

06248132

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates generally to artificial joints and particularly to an endoprosthesis for the hip joint.
Artificial joints and especially those for the hip have been known for many years. Such replacement devices include substitute members for the two parts of the natural joint, namely, the femoral head, which is joined to the femur, and the hip socket which receives and cooperates with the head to provide a natural universal joint.
Replacement of the natural hip joint parts is necessary when deterioration has occurred to one or both of the natural femoral head and socket. Ideally, the replacement members should reproduce the structure and function of the members which they replace. It is important that the femoral head be securely attached to the femur, that the head be received within the socket and that the resulting joint be produced with a degree of resilience or cushioning.
U.S. Pat. No. 4,770,661 discloses a replacement joint having a cup assembly which includes a generally hemispherical metal outer shell threaded at the rim and having an upper part received directly into the hip socket; an interfitting plastic core received within the shell and a split plastic locking ring. The core in turn receives the femoral head and the split plastic locking ring is installed by attaching the plastic parts under the head, cementing the parts together and then threadedly locking the plastic parts to the metal outer shell thereby encapsulating the ball. There is no metal casing encapsulating the head but rather a combined plastic and metal casing. Also lacking is any resilient feature between the head and the socket. U.S. Pat. No. 4,159,544 discloses an exterior spring system between the head and the socket. U.S. Pat. No. 3,648,294 discloses an arrangement which provides a rather complicated piston and cylinder construction within the head. U.S. Pat. No. 4,406,023 discloses the use of a lubricant filled bellows system for providing joint resilience. U.S. Pat. No. 4,199,824 discloses a femoral prosthesis having a flange and serrations to provide additional support and load transfer capability between the joint parts. All five of these prior patents are incorporated herein by reference.
The present hip joint replacement represents an improvement over prior art devices and overcomes problems and provides advantages in a manner not revealed in the known prior art.
SUMMARY OF THE INVENTION
This invention provides an artificial hip joint replacement which provides substantially universal joint movement between a stem assembly which is secured to the hollowed out passage of the femur and a cup assembly, which relatively receives the femoral head and is itself rotatively received within the prepared hip socket, said socket being fitted with a firmly attached socket shell.
The structural arrangement of parts provides for rotational movement of the cup assembly about the radial center of the socket and pivotal movement of the stem about the center of the femoral head and circular movement of the head about the axis of the femoral neck.
The hip joint prosthesis provides a stem assembly attached to the femur including a generally spherical head and a cup assembly having an outer casing received with the socket and an inner lining receiving the head.
It is an aspect of this invention to provide that the cup assembly outer casing includes an upper portion and a lower portion threadedly attached to the upper portion to encapsulate the lining, the lining including an upper portion received within the casing upper portion and having a recess receiving the head, said lining having a lower portion received within the casing lower portion and having a recess seating the head, said lining lower portion being split into at least two portions surrounding the head.
It is another aspect of this invention to provide that the cup assembly includes resilient means therewithin providing shock absorption between the head and the casing.
It is another aspect of this invention to provide that the stem assembly includes an elongated stem and a shield and means between the stem and the shield permitting independent movement of the stem relative to the shield following insertion of the stem and shield together in an elongate passage into the femur.
This invention provides a hip replacement which is relatively inexpensive, easy to manufacture and install and efficient in providing natural joint movement.


REFERENCES:
patent: Re. 31865 (1985-04-01), Roux
patent: 3813699 (1974-06-01), Giliberty
patent: 4021865 (1977-05-01), Charnley
patent: 4159544 (1979-07-01), Termanini
patent: 4180873 (1980-01-01), Fixel
patent: 4563778 (1986-01-01), Roche, et al.
patent: 4728335 (1988-03-01), Jurgutis
patent: 4795471 (1989-01-01), Oh
patent: 4960427 (1990-10-01), Noiles
patent: 5080678 (1992-01-01), Spotorno et al.
patent: 5824108 (1998-10-01), Huebner
patent: 2069338 (1981-08-01), None

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