Finite element analysis of biomechanical effects of oversized total talar prosthesis and collateral ligament reconstruction on total talar replacement.

Abstract

Background: Total talar replacement (TTR) using a personalized customized total talar prosthesis (TTP) is an emerging and promising surgical option for the treatment of ankle problems. However, how to solve ankle instability after total talar replacement, and the influence of related solutions on foot biomechanics has not been investigated.

Methods: Our preliminary studies have found that enlarging a personalized total talar prosthesis (TTP0) by 1.5 % along the coronal axis (TTP-FP1.5) and reconstructing the anterior talofibular ligament (ATFL) significantly can enhance ankle stability. However, there is a lack of insight into the effect of the two options on biomechanics. Consequently, this work constructed anatomically detailed finite element models of the foot, including an intact model and four surgical models, including replacement of TTP0, replacement of TTP-FP1.5, and two models of TTP-coupled ATFL reconstruction. Biomechanical differences were evaluated by numerical simulation of a balanced-standing and three characteristic instants of the stand phase.

Results: Changes in plantar pressure distribution, joint contact pressure and force transmission, von Mises stress on bone, and prosthesis stress were predicted and analyzed. It was found that significant changes in foot biomechanics occurred after TTP-FP1.5 replacement compared to TTP0 replacement. In contrast, no ligament reconstruction versus ATFL reconstruction exerts a minor effect on biomechanics.

Conclusion: The findings indicate that the shape of the prosthesis is the primary factor affecting foot biomechanics after total talar replacement. In contrast, reconstruction of the ATFL has only a minimal effect on the biomechanics of the foot. The above findings will provide a solid basis for the improvement of TTR surgical plans in clinical.