Abstract
Introduction: The artificial disc consists of proprietary polyolefin rubber core bonded between two titanium endplates. It has been developed for the treatment of symptomatic disc degeneration with the aim of providing segmental stability and motion following wide disc space clearance. It was designed to have similar properties to a normal adult human intervertebral disc when working in conjunction with the retained anulo-vertebral tissues and the supporting musculoligamentous system.
Methods: Over 120 discs were used to biomechanically characterize the Device. Range of motion tests were designed and performed to measure the axial compression, torsional, and shear stiffness of the artificial disc and to compare this with the known values for the human lumbar disc. Pullout test was performed to evaluate the immediate and short-term stability of the inserted device by assessing the mechanical resistance to pullout or expulsion. To assess the ability of the implant to withstand average daily living loads throughout its predicted life, compression and compressive shear fatigue testing were performed.
Discussion: The device was found to replicate many of the physiologic characteristics of the in-vivo FSU. The quasi-static testing showed the device to have higher strength values than the highest in-vivo loads and displacements. Fatigue testing showed the smallest device endurance limit of 3,500N at ten million cycles.
The results demonstrate that the failure modes of the device contain sufficient safety margins to support the use of the device in a prospective clinical study.
The abstracts were prepared by Professor Jegan Krishnan. Correspondence should be addressed to him at the Flinders Medical Centre, Bedford Park 5047, Australia.
