Preliminary results of a biomechanics driven design of a total ankle prosthesis

Introduction A new design of total ankle replacement [1] was developed according to extensive prior biomechanical research [2-5]. A linkage-based mathematical model was used to design for the first time ligament-compatible shapes of the prosthesis components in the sagittal plane (Fig. 1). The radius of the metal talar component in the sagittal plane is about 50% longer than that of the normal talus, the metal tibial component is spherically convex. A fully conforming meniscal bearing is interposed between them and free to move. Experiments in cadaver specimens confirmed the mathematical prediction that the bearing moves forwards on both metal components during dorsiflexion and backwards during plantarflexion. FEA models [6] and experiments with a wear simulator [7] confirmed that the risk of wear is minimised. Preliminary clinical results are here reported as support to the biomechanical claims.