Tribology of ball-and-socket total disc arthroplasty

Abstract

Total disc arthroplasty (TDA) can be used to replace a degenerated intervertebral disc in the spine. There are different designs of TDAs, but one of the most common is a ball-and-socket combination. Contact between the bearing surfaces of such designs can result in high frictional torque, which can then result in wear and implant loosening. This study was designed to determine the effects of change in design factors, such as dimensions and material combinations, on friction and wear of ball-and-socket TDAs. Friction tests were carried out on generic models with ball radii 10, 12, 14 and 16 mm. Three material combinations were investigated; metal-on-metal, metal-on-polymer and for the first time polymer-on-metal. Wear tests were performed on metal-on-polymer Charité® TDAs and generic metal-on-metal models to compare the wear rate under the same conditions. Friction test results showed that polymer-on-metal TDAs create less friction than metal-on-polymer and metal-on-metal TDAs. Wear test results showed that under the same conditions, metal-on-metal TDAs create 23 times less wear debris than metal-on-polymer. The results were in agreement with studies on total hip arthroplasty (THA). The results of this work suggest possible alternatives for future TDA designs.