Summary

The patients with ankle instability were more likely to have an internally rotated talus

Abstract

Purpose

and Hypothesis: Specific anatomic variations of the ankle mortise may be found in people with ankle instability. The purpose of this study was to evaluate the fibular and talus position in subjects with ankle instability. It was hypothesized that the patients with ankle instability were more likely to have an internally rotated talus rather than a displaced fibular.

Methods

MR Images of 50 patients with chronic ankle instability and 50 patients from the author’s institution for reasons unrelated to ankle instability were reviewed. The position of the fibular in relation to the talus (axial malleolar index, AMI) and medial malleolus (intermalleolar index, IMI) were evaluated at the axial plane. Meanwhile, the rotation of the talus was measured and calculated by a new index, Malleolar Talus Index (MTI), which was in relation to the medial malleolar.

Results

As a index reference to the talus, the AMI in the instability patients showed significantly increased in instability patients when compared that in the control group (11.0°±5.7° VS 7.7°±5.4°, P <0.01). However, as an index reference to the medial malleolar, there was no statistically significant difference in the IMI between instability and control groups (7.2°±3.4° VS 7.9°±3.6°, P =0.3). The MTI increased significantly in the instability patients when compared that in the control group (89.5°±2.64° VS 86.0°±2.2°, P <0.01).

Conclusion

The patients with ankle instability were more likely to have an internally rotated talus. However, no significant variation in fibular position was found in patients with chronic ankle instability.