BIOMECHANICAL ANALYSIS OF FIXATION OF TOTAL ANKLE REPLACEMENT

Abstract

Primary stability of a total ankle replacement (TAR) is essential in preventing long-term aseptic loosening failure, and could be analysed biomechanically in terms of bone-prosthesis interface relative micromotion (BPIRM). Clinical outcome studies have shown that aseptic loosening of the TAR is commonly due to the failure of the talar component. Hence it was of interest to investigate the failure mechanism of the talar component when subjected to physiological loading conditions. The influence of different design features of the talar component on BPIRM was also studied. Simulation studies through Finite Element Analysis and cadaveric experiments were completed. High BPIRM due to de-bonding was predicted for the STAR™ Ankle talar component at posterior region which coincided with clinical observations. The final design that incorporated the 3 mm pin length was found to be a favourable design with reduced the BPIRM and talus bone stresses thereby reducing the risk of long-term aseptic loosening.