Wear studies for development of an intervertebral disc prosthesis

Two long-term wear behavior studies used in part of the process of selecting the best materials for a new all-metal orthopaedic spinal implant are presented. The relative and absolute wear volume rates of candidate metals were investigated through simulation of two bearing regions of an intervertebral disc prosthesis. It was determined gravimetrically that hot isostatically pressed Co-Cr-Mo alloy provided the lowest Co-Cr-Mo alloy wear debris generation. It had an average wear volume rate of 0.093 mm3/million cycles from a spring-in-pocket simulation and 0.126 mm3/million cycles from a hinge (pin-in-slot) simulation. The estimated total wear volume of a hot isostatically pressed intervertebral disc prosthesis with titanium-6%Al-4%V alloy springs was 2.9 mm3/million cycles.