Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1996-12-24
2000-10-17
Yu, Mickey
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
623 16, 606 61, A61F 244
Patent
active
061324647
DESCRIPTION:
BRIEF SUMMARY
This invention relates to devices for replacement of posterior vertebral facets articular surfaces affected by varying degrees of degeneration and/or destruction, and elements for anchoring these prostheses on the vertebrae. These prosthetic elements are made of a solid casting of support plate-artificial articular blade, fixed on the corresponding vertebra by anchoring means onto the pedicles and/or transverse processes and/or spinous process.
With respect to vertebral articular surface degeneration, arthrosis of the joint facets is found which shows a reduced thickness of cartilage and may advance to entire disappearance thereof. Furthermore, surrounding the degenerated articular surfaces, there is bony formation able to give neurological compressions inside either foramenae or spinal canal. These facts induce lower back and nerve roots pain which involve a large part of the population.
As often as not, a degenerative disease is found which involves articular surfaces only, but may also have a more invasive pathology including traumatic, infectious, tumorous or dysmorphic (spondylolisthesis, for example) effecting the destruction of all or part of the articular process.
It is essential to reduce and/or to remove frictions on degenerated articular surfaces: until now, this aim has been achieved either by fixing all motions between concerned vertebrae with spinal arthrodesis or fusion more or less associated with an osteosynthesis (Harrington, Cotrel-Dubousset, TSRH, New Orleans, etc.) or by reducing these frictions with a spinal ligamentoplasty (Graaf, Senegas, Lemaire, etc.).
The locking of vertebral motions by spinal arthrodesis or ligamentoplasty induces, beyond a spinal stiffness, an increased strength on the joint facets of the adjacent vertebrae above and below the fusion, usually sustained by the considered intervertebral space and therefore an increase of degeneration of these joint facets.
With regard to discal prostheses, they provide a "space" between two vertebral bodies while preserving some motion. They solve the aging intervertebral disc problem but don't function for reducing the strength on posterior joint facets of which the motions and the frictions are maintained.
Therefor the invention aims at overcoming disadvantages of all known devices by providing a new device which enables replacement of degenerated articular surfaces with articular prostheses. These prostheses preserve vertebral motion while cancelling "bone-cartilage" frictions of degenerated surfaces and therefore pain and/or osteophytic induction with nerve root compressions in foramenae.
Further, the invention relates to prosthetic devices for treatment of the articular surface and to larger prosthetic elements for total replacement of bony process and its articular surface. The invention aims at preserving the spinal stability by the intervertebral "hooking" of the process prosthetic devices between them, as made by the natural vertebral processes, and at preserving the potential of functional motion without damaging the spinal muscles-ligaments system.
According to the invention, these prosthetic elements, built with biocompatible materials such as metallic alloy (stainless steel, titanium, or other) and/or composite material have a first "articular" surface which is matched with the similar surface of the adjacent vertebra for sliding between themselves with a minimal friction, and second opposite "bony" porous surface, with scattered protruding points, coated or not with hydroxy-apatite, for resting on the remaining bone of the vertebral articular process. Thus according to the invention, these prosthetic elements replace at least the articular surfaces of one intervertebral space according to inferior joint facets of the superior vertebra and to superior joint facets of the inferior vertebra. If necessary, the prostheses may be unilateral but more often than not, and preferably, bilateral.
According to the invention, if the remaining bone of the articular process is too weak, the prosthesis replaces the total process an
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Dutton, Jr. Harold H.
Fairant Paulette
Nguyen Tram A.
Yu Mickey
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