Multiple axis intervertebral prosthesis

Details Multiple axis intervertebral prosthesis Multiple axis intervertebral prosthesis

1998-08-04

2001-05-08

Willse, David H. (Department: 3738)

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

Implantable prosthesis

Bone

C623S017110

Reexamination Certificate

active

06228118

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an intervertebral prosthesis, for the replacement of multiply-operated or degenerative disks that are creating painful motion or nerve root compression. In particular, this invention relates to a prosthesis with two components, able to rotate inside the other, while each is fixed to its adjacent vertebra.
BACKGROUND OF THE INVENTION
Disk disease is endemic. When a spinal disk in a patient is no longer serviceable, a fusion is often done. A fusion involves the removal of the degenerative vertebral disk, which had allowed for movement and rotation of the adjacent vertebrae relative to one another. The two vertebrae surrounding the disk are then joined and fixed, removing the mobility from that area. However, fusions have many disadvantages. They are destructive and have a significant failure rate. They encourage degenerative disease of the disks above and below and most often require donor bone, which causes its own set of complications.
The evolution of surgical treatment of other diseased joints has progressed from fusion, to debridement and resurfacing and then to joint replacement. The standard of care for surgical treatment of advanced disease of hip and knee joints is now joint replacement. However, the search for a working spinal disk replacement has not yielded as great of a success as of yet. The currently available experimental prostheses are not widely accepted.
There are a number of ball and socket type arrangements that have been developed for disk prostheses, but the problem with existing prostheses is that none of the devices address the need for self centering of the ball within the socket. Self-centering is an important feature because it allows the prosthesis to imitate the normal motion of the disk. The availability of a mechanism which enables a ball and socket type prosthesis to self-center would give a patient a flexible, natural-feeling prosthesis. An additional problem which is not addressed by the existing devices is any sort of specific method for building lordosis into the prosthesis. The advantage of building lordosis into the prosthesis is that it allows the back to have a more natural curvature, rather than an artificial stiffness. For a disk prosthesis to be as successful as some other joint replacements, it needs to allow for as much natural movement as possible.
It is also important that a prosthesis allows the anatomy of the motion segment to be the constraining factor for the limits of motion. If the prosthesis is intrinsically constrained, then it must bear the stresses of constraint, particularly at the bone/prosthesis interface, as well as internally in the prosthesis. Other fully constrained protheses, such as total knees or elbows, have failed. If a prosthesis was developed that allowed the anatomy of the motion segment to be the constraining factor, then the facets and soft tissue would bear the stresses of constraint allowing for longer life of the prosthesis. The life of the prosthesis should be long enough to make the operation worthwhile, so it need not be repetitive.
It is desirable that a prosthesis be provided that allows for a significant range of motion, that mimics the motion of an actual vertebral disk. Ideally, it would be stable, without intrinsic constraining factors, but not stiff, so it will have a long lifetime, and feel as natural as possible.
SUMMARY OF THE INVENTION
Therefore, the present invention provides for an intervertebral prosthesis that self-centers, allows a range of motion, and in a preferred embodiment also provides for lordosis considerations. The prosthesis is designed to alleviate a painful motion segment, for degenerative disk disease, for the multiply operated disk, or to relieve nerve root compression.
The prosthesis assembly comprises a male component which can rest in the female component, while both are attached to adjacent vertebrae. The male component consists of a support plate, preferably wedge shaped, from which, in a particularly preferred embodiment, one flange extends. The flange is preferably defined as a mounting tab that extends vertically from the edge of the component. It contains at least one hole through which an attachment element, such as preferably a screw, may pass, for fixation to adjacent vertebrae. The hole may be preferably in the shape of a figure eight. The preferred means for attachment to the adjacent vertebra is screws which pass through holes in the flange. The male component also consists of an articulating projection, which is preferably doughnut shaped. When assembled with the female portion, it allows for multiple axes of rotation. The doughnut shaped projection preferably contains a double radius for ease in self-centering.
The female component consists of a support plate, preferably flat, from which, in a preferred embodiment, one flange extends vertically. The preferred means for attaching the female portion to the adjacent vertebra is screws which pass through holes in the flange. The female component also comprises a circular pocket with angled walls in which the male component can rest. In another preferred embodiment, the female component has a coating or insert on the inside surface of the pocket to reduce friction between the components. Preferably, the material for the coating is plastic or ceramic.
In a preferred embodiment, the system comprises a porous coating, on the bone-facing surfaces of the support plates, to allow for a second method of fixation to the vertebra. The components may preferably be made of a metal alloy or of a ceramic material. The two components can also be made of dissimilar materials from each other. A particularly preferred prosthesis conforming to the present invention is made of chromium cobalt alloy to give strength and longevity to the prosthesis.


REFERENCES:
patent: 5002576 (1991-03-01), Fuhrmann et al.
patent: 5258031 (1993-11-01), Salib et al.
patent: 5314477 (1994-05-01), Marnay
patent: 5360430 (1994-11-01), Lin
patent: 5401269 (1995-03-01), Büttner-Janz et al.
patent: 5425773 (1995-06-01), Boyd et al.
patent: 5458641 (1995-10-01), Ramirez Jimenez
patent: 5507816 (1996-04-01), Bullivant
patent: 5549680 (1996-08-01), Gordon
patent: 5556687 (1996-09-01), McMillin
patent: 5562738 (1996-10-01), Boyd et al.
patent: 5645596 (1997-07-01), Kim et al.
patent: 5674296 (1997-10-01), Bryan et al.
patent: 5676701 (1997-10-01), Yuan et al.
patent: 5683465 (1997-11-01), Shinn et al.
patent: 5782832 (1998-07-01), Larsen et al.
patent: 5895428 (1999-04-01), Berry
patent: WO91/13598 (1991-09-01), None

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