Three-dimensional talar shape seems not a factor in chronic mechanical ankle instability

BACKGROUND: There is a long-lasting discussion on whether the anatomical shape of the talus is a predisposing factor in the development of chronic ankle instability (CAI). The progression from two- to three-dimensional imaging techniques allows for a new investigation on this topic. METHODS: MRI studies of 25 young and healthy adults with CAI and 25 controls without CAI were conducted in neutral-null position and in plantarflexion-supination. The talar angle and the talar radius were transposed to a three-dimensional approach and compared between the groups and the positions. RESULTS: There was no significant difference in the talar angle nor the talar radius between the groups. Plantarflexion-Supination did not lead to a significant change in tibiotalar configuration associated with the two parameters. CONCLUSION: Three-dimensional talar shape is not significantly different between patients suffering from CAI and healthy controls. This supports the interpretation that the dynamic congruency of the joint, which is influenced by ligamentous integrity remains the main anatomical component in mechanical ankle instability. TRIAL REGISTRATION: The study protocol was prospectively registered at the German Clinical Trials Register (#DRKS00016356) on 05/11/2019.