Compliant Mechanism as a Motion-Preserving Artificial Spinal Disc: A Novel Concept

Abstract

Investigations of spinal disc replacement options have been conducted for several decades but, as yet, the suggested solutions have not been proven to correctly preserve the natural joint motion. This paper focuses on a new structure of an artificial intervertebral disc joint that closely supports a close-to-natural three-dimensional motion of two adjacent vertebrae. The disc design is based on a passive parallel mechanism, with different stiffnesses for each link. Optimization of the artificial disc dimensions and link stiffnesses enabled convergence of the finite screw axis (FSA) of the artificial disc joint with that of a natural disc. As a result, the natural motion of the spine vertebrae was maintained and the loads on the facet joints minimized. The mechanism design was optimized, built, tested, and proven to be a feasible artificial disc with natural motion preservation characteristics.