The Effects of Implant Orientations and Implant–Bone Interfacial Conditions on Potential Causes of Failure of Tibial Component Due to Total Ankle Replacement

Abstract

Aseptic loosening of implant components is a major issue of failure for total ankle replacement (TAR). One of the causes of implant loosening is a result of excessive bone density loss. This study is aimed at determining the effects of implant orientations and implant–bone interface conditions on the potential causes of failure of the tibial component. Three-dimensional finite element (FE) models of intact and implanted ankles were developed using computed tomography data sets. To understand the effect of implant orientations, four other FE models of the implanted ankle were developed separately, which consist of a variation of varus and valgus angles of 5° and 10°, respectively. Dorsiflexion and neutral and plantar flexion positions were considered as applied loading conditions. Orientations of the implant caused a decrease in strain energy density (SED) of the tibia bone away from the implant vicinity, where around 10–50 and 10–60% reduction in SED was found owing to the orientation of the 5° and 10° varus and valgus angles. Decreases in SED were found to be greater in the case of debonded implant–bone interface conditions compared to bonded interface conditions. This study indicates that proper bonding between implant and bone and implant orientation are important for long-term survival of the tibial component owing to TAR.