Intervertebral disc replacement

Abstract

An intervertebral disc prosthesis in a preferred embodiment has a matrix of bioincorporable fabric, and a nuclear core centrally mixed into the matrix. The core is formed by impregnating the fabric substrate centrally with a polymer, preferably of liquid form that cures into a viscoelastic solid, in which each component—polymer and fabric—reinforces the other against tearing, shearing and weakening under stress. The core is a hybrid composite adapted for elastic deformation centrally of the matrix, in which the polymer is mixed with the fabric, and is surrounded by the outer bioincorporable fabric margin of the matrix. In another embodiment, the nuclear core is separated from an outer sheath of the bioincorporable fabric by an intermediate ligament encasement that surrounds the purely polymeric core In either embodiment, each edge of the outer fabric that interfaces a vertebral end plate is impregnated with an agent to stimulate osseus incorporation and anchoring. An adjunct anchoring system with penetration of bone of adjacent vertebra may be used to for attachment until and after bioincorporation occurs.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates generally to intervertebral disc prostheses, and more particularly to improvements in and anchoring systems for disc prostheses to assure operation, fixation and stabilization of the prosthesis corresponding to a natural disc. [0002] The human backbone (the vertebral or spinal column) 10 (FIG. 1) consists of numerous longitudinally aligned vertebrae 11, adjacent ones of which are separated by individual cartilaginous intervertebral discs 12 and connected to one another by ligaments. The vertebral column is the vertical axis of the skeleton, extending from the skull (not show) at its proximal end to the pelvis (not shown) at the distal end. It serves to support the head and trunk of the body, and to protect the spinal cord (not shown) that passes through the vertebral (spinal) canal formed by openings in the vertebrae. Adjacent the distal end of the vertebral column, the sacrum portion 13 of the pelvis is formed by seve...

AI Technical Summary

Benefits of technology

[0029] In essence, the intervertebral disc is an anatomical spacer, stabilizer, load dampener and shock absorber, positioned between the vertebral end plates. The disc and surrounding ligaments also stabilize the spine, connect adjacent vertebrae, and prevent excessive rotation and subluxation of the vertebrae. As noted in the background section above, intervertebral discs have some desirable deformability attributable to their viscoelastic properties. They also demonstrate hysteresis, and have a high degree of hydration. The hysteresis is exhibited in response to the mild deformability of the disk under compressive loading, when, after unloading, the disc rebounds to its normal position. This resiliency to compressive loading and unloading is a key function of the disc. To yield suitable results, an artificial disc—a disc prosthesis—must replicate all of these properties, characteristics or functions of the natural intervertebral disc.

[0031] The intervertebral disc prosthesis of the invention possesses characteristics of being compressible, mildly deformable, resilient, hydrated, durable, nontoxic, nondegradable, nonfragmenting, and viscoelastic, among other properties. The prosthesis acts as a solid material to provide structural spacing and load dampening effect between vertebral end plates. It is suitable for replacement of a damaged natural disc in any of the cervical, thoracic or lumber spinal regions of the vertebral column.

Problems solved by technology

Injury, exertion or the aging process can produce changes in the discs, such as loss of firmness of the central region and thinning, weakening and cracking of the outer layer as a result of degenerative changes, and breakage of the outer layer and squeezing out of the central region as a result of injury from external pressure or heavy lifting.

The result is chronic lower back or leg pain, which can be disabling.

While fusion enjoys success in alleviating symptoms and stabilizing the joint at the previous vertebra-disc interface, it decreases the range of motion of the vertebral column in the portion of the region where the surgical procedure was performed.

Also, the biomechanical rigidity of the fused vertebrae may exacerbate deterioration of adjacent portions of the region.

However, so far as is known to the applicant herein, the prior art has not given promise of successful implementations and methods for anchoring implanted artificial intervertebral discs in the vertebral column to achieve relatively permanent fixation and stabilization of the implant.

Prior art artificial intervertebral discs, and techniques of fastening, anchoring and stabilizing implanted artificial discs do not appear likely to yield satisfactory results.

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