NEW CONCEPT FOR AN ARTIFICIAL INTERVERTEBRAL DISC (AID) AS A TOTAL REPLACEMENT OF A HERNIATED LUMBAR DISC

摘要

A novel concept was developed of an artificial intervertebral disc (AID) for the total replacement of herniated lumbar discs from L1/L2 down to L5/S1. To implement the necessary biomechanical properties, a spring element based on a shape memory alloy (SMA) of Nitinol is placed between the caudal and cranial end plates of the AID. The flexibility of the AID results from the superelastic deformation capability of the Nitinol. Therefore, no friction between moving parts and no mechanical abrasion occurs, which leads to a very high mechanical durability of the device. The superelastic properties of Nitinol, together with an appropriate geometric design of the spring element, allow the most important biomechanical properties of the natural disc to be mimicked. The biomechanical properties (e.g., axial torsion, axial compression, and axial extension, lateral translation and flexion) can be implemented simultaneously--each of them with separately tuneable damping and limiting functions. First, mechanical tests on simple prototypes of the spring element led to the conclusion that an AID with excellent biomechanical properties and a very high mechanical durability can be obtained, opening a new perspective for better herniated disc replacement therapy.