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

## TL;DR

This study found that the 3D shape of the talus bone is not a factor in chronic ankle instability, suggesting ligament health is more important.

## Contribution

The study introduces a three-dimensional analysis of talar shape in chronic ankle instability using MRI.

## Key findings

- No significant difference in talar angle or radius between CAI patients and controls.
- Plantarflexion-supination did not alter tibiotalar configuration significantly.
- Dynamic joint congruency, not talar shape, is likely key in mechanical ankle instability.

## Abstract

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.

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.

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.

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.

The study protocol was prospectively registered at the German Clinical Trials Register (#DRKS00016356) on 05/11/2019.