Three-dimensional morphometric analysis of the talus: implication for variations in kinematics of the subtalar joint

Purpose Three-dimensional (3D) movement of the clinical subtalar joint (CSTJ) is primarily determined by the morphology of the articular surfaces of the talus. The purposes of this study were to assess the 3D orientation of the CSTJ facets of the talus and the talar head and to determine the tri-axial angular relationship. Methods Fifty dry tali were scanned using computed tomography to create a 3D bone model of the talus. The tri-axial angles of the anterior, middle, and posterior facets and the talar head were calculated. A correlation analysis between the angles of the posterior facet and the talar head was also performed. Results The transverse angle at both the posterior facet and the talar head was significantly correlated with the sagittal angle (r = -0.441, p < 0.001; and r = -0.694, p < 0.001, respectively). The sagittal angle of the posterior facet was significantly correlated with that of the talar head (r = 0.478, p < 0.001). Conclusions When the posterior facet of the talus and the talar head exhibits a greater downward and lesser medial orientation, a greater inversion/eversion at the CSTJ should be induced, while an opposite orientation should induce greater plantarflexion/dorsiflexion and medial/lateral rotation at the CSTJ. Our findings will be useful for planning rehabilitation programs and surgical interventions to correct the subtalar joint orientation in clinical settings.