Posterior spinal arthroplasty-development of a new posteriorly inserted artificial disc and an artificial facet joint

Abstract

Lumbar disc and facet joint replacement prosthesis are provided. The lumbar disc prosthesis includes first member having a vertebral disc contact surface and a recessed portion on an opposing surface thereof and a second member having a vertebral disc contact surface and a protruding portion on an opposing surface thereof. The protruding portion of the second member engages the recessed portion of the first member in use. The first and second members are provided with at least a middle section and two end sections. The recessed and protruding portions are provided in the middle section of the respective members and each end section has a narrowing taper. The facet joint prosthesis includes a first member for attachment to a first posterior lumbar disc and a second member for attachment to a second posterior lumbar disc. At least a part of the first member is telescopically mounted in at least a part of the second member.

Description

REFERENCE TO PENDING APPLICATIONS [0001] This application claims priority to Great Britain Patent Application No. 0422963.9 filed Oct. 15, 2004. FIELD OF THE INVENTION [0002] This invention relates to devices and surgical methods for the treatment of various types of lumbar spine pathologies. It is specifically directed to the different types of degenerative pathologies in the lumbar spine. It deals with the development of an artificial facet joint, and an artificial lumbar disc replacement that is specifically designed to be inserted from a posterior approach to the spine. BACKGROUND OF THE INVENTION [0003] Back pain affects 40% of the population. Up to 20% of the population visit their family doctor requesting help with their back problem. Up to 30% of patients continue to complain of significant back pain at one year following the onset of their symptoms. [0004] Although the majority of patients have minor sprains or strains which are self limiting, a significant number of patien...

AI Technical Summary

Benefits of technology

[0032] Preferably one or both ends of the first and second disc members have a narrowing taper (i.e. the prosthesis as a whole has a narrowing taper). This narrowing taper is as a result of the outer or vertebral end plate contact surface of said first and / or second disc member being provided at an acute angle with respect to the horizontal at one or both ends. These angled surfaces are preferably substantially planar in form. For example, the outer or vertebral end plate contact surface of the first disc member slopes downwardly towards the ends of the disc member and / or the outer or vertebral end plate contact surface of the second disc member slopes upwardly towards the ends of the disc member. The narrowing taper of the prosthesis allows easy insertion of the prosthesis in the disc space via a posterior route.

[0057] Thus, the present invention overcomes the problems and disadvantages associated with current disc replacement strategies. It has all the benefits associated with posterior lumbar inter-body fusion surgery, but at the same time it allows movement at that level and reduces the strain on adjacent discs and the risks of adjacent segment disc failure. This invention also address all three pain generators at the lumbar disc level including the degenerative disc, the impingement of the neural structures, and the facet joint.

Problems solved by technology

The facet joint is in fact a synovial joint and suffers from the problems that are known to affect other synovial joints in the body like the hip and the knee.

Anterior inter-body fusion on its own is still questioned because it does not provide a posterior tension band.

One of the disadvantages of anterior lumbar arthroplasty is that the facet joints at this level continue to move and also continue to act as a pain generator.

The other disadvantage of anterior lumbar arthroplasty is that the majority of spine surgeons are not familiar with the anterior approach, and although complications are uncommon, they can be life and limb threatening when they do occur.

There is therefore a concern among researchers and the surgical community, that long term results of anterior lumbar disc arthroplasty may be compromised by progressive degeneration of the facet joint at the same level.

In addition, after lumbar disc arthroplasty, several patients continue to complain of facet joint pain because of increased loads being placed on the facet joint as a result of the surgical procedure.

At present there is no posterior lumbar arthroplasty procedure available.

Images