Spacerless artificial disc replacements

Abstract

Spacerless artificial disc replacements (ADRs) are disclosed. One preferred embodiment includes two saddle-shaped components to facilitate more normal spinal flexion, extension, and lateral bending while limit axial rotation, thereby protecting the facet joints and the annulus fibrosus (AF). Either or both the superior and inferior components are made of a hard material such as chrome cobalt, titanium, or a ceramic including alumina, zirconia, or calcium phosphate. The articulating surfaces of the ADR are also preferably highly polished to reduce friction between the components. Metals, alloys or other materials with shape-memory characteristics may also prove beneficial.

Description

REFERENCE TO RELATED APPLICATION [0001] This application claims priority from U.S. Provisional Patent Application Serial No. 60 / 372,520, filed Apr. 12, 2002, the entire content of which is incorporated herein by reference.FIELD OF THE INVENTION [0002] This invention relates generally to artificial disc replacements (ADRs) and, more particularly, to devices that operate without softer spacer materials such as polyethylene. BACKGROUND OF THE INVENTION [0003] Polyethylene spacers are common in some artificial joint situations, including total knee replacements (TKRs). Polyethylene spacers are also used between metal plates in many artificial disc replacement (ADR) designs. [0004] Complications arising from poly debris are well documented, however, including fracture of the spacer once it becomes too thin, absorption and migration of poly particles throughout the body, and loosening of the bone metal junction as a reaction of the poly debris. [0005] Metal-on-metal and ceramic-on-metal s...

AI Technical Summary

Benefits of technology

[0007] The present invention replaces polyethylene artificial disc replacement (ADR) spacers with harder, more wear-resistant materials. In the preferred embodiments, an ADR according to the invention includes opposing saddle-shaped components to facilitate more normal spinal flexion, extension, and lateral bending. Preferably, the ADR allows at least 10 degrees of movement in the flexion to extension direction and at least 5 degrees of movement in the lateral bending direction. The saddle-shaped articulating surfaces also limit axial rotation, thereby protecting the facet joints and the annulus fibrosus (AF).

[0008] According to the invention, either or both the superior and inferior components are made of a hard material such as chrome cobalt, titanium, or a ceramic including alumina, zirconia, or calcium phosphate. The articulating surfaces of the ADR are also preferably highly polished to reduce friction between the components. Metals, alloys or other materials with shape-memory characteristics may also prove beneficial.

Problems solved by technology

Instead, axial rotation is limited through the use of multiple ball-and-socket joints or an elongated ball-and-socket joint, which complicates the design.

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