Evaluation of a universal talus implant during gait: a combined musculoskeletal and finite element modelling approach

Universal talus implant has emerged as an innovative solution for talus bone collapse, aiming to retain the clinical benefits of custom total talus replacement while addressing its logistical drawbacks. A subject-specific combined musculoskeletal-finite element (MSK-FE) modeling framework was developed to evaluate two universal talus implant designs during dynamic gait: a purely cobalt chromium (CoCr) implant, and an implant coated with polycarbonate-urethane (PCU), both compared to the native talus. To do so, a MSK simulation of the stance phase of gait was conducted to estimate joint kinematics and joint reaction forces in the ankle complex, with a subsequent dynamic FE simulation performed to assess contact characteristics in terms of contact area and pressure, in cartilages surrounding the talus/implant. The FE model was built directly from the bone geometries of the MSK model to ensure consistency across the study. Results showed that the PCU-coated implant more closely replicated native biomechanics, while the CoCr implant produced consistently higher pressures and smaller contact regions. Normalized RMSE across gait confirmed lower deviation from the native case for the PCU-implant in most joints. These findings highlight the potential of PCU coated implants in improving contact mechanics in articular cartilage as well as the potential of the universal implant topology. This is the first study to dynamically evaluate intra-articular behaviour in all joints surrounding the talus bone during gait, and particularly by analysing the performance of universal talus implants, demonstrating the utility of a MSK-FE approach and offering valuable insights into implant performance under physiological conditions, informing future implant design.