Typical shape differences in talus and calcaneus between subjects with chronic ankle instability and controls

The aim of this study is to quantitatively compare threedimensional (3D) shape variations in the talus and calcaneus within individuals with unilateral CAI and healthy controls. Statistical shape models (SSM) of the talus and calcaneus were built based on the mixed data of 26 patients with CAI (mean age: 29 years) and 26 healthy controls (mean age: 36 years). Using the models and ANCOVA (Analysis of Covariance) test, shape variations were quantitatively compared between the groups. Tali and calcanei did not significantly vary within CAI patients. Statistically significant shape differences between the tali (p = 0.015) and calcanei (p = 0.003) of CAI patients and healthy controls were found. In the talus, it was the curvature of talar lateral process combined with the inclination angle of talar neck relative to the body. In the calcaneus, it was the medial and lateral tuberosity combined with contour of anterior articular surface.