Revolutionizing Ankle Instability Diagnosis: Analyzing Talus Rotation through Weight-Bearing CT Scans

Research Type: Level 3 - Retrospective cohort study, Case-control study, Meta-analysis of Level 3 studies Introduction/Purpose: Lateral ankle instability diagnosis traditionally relies on clinical evaluation and MRI findings. However, assessing dynamic changes in ankle instability has remained a challenge. Weight-bearing CT offers a promising method to dynamically evaluate ankle instability and providing more reliable insights into talus rotation. This study aims to compare talus rotation, as measured by the Malleolar Talar Index (MTI) on weight bearing CT, in patients with and without lateral ankle instability. Methods: We compared the MTI values from weight-bearing CT scans between two groups: patients with lateral ankle instability and those without. The MTI is a reproducible measurement reflecting talar rotation, with a larger MTI indicating increased internal rotation of the talus. Ankle instability diagnosis was confirmed by clinical evaluation (history of inversion injury and a positive anterior drawer test) and/or MRI findings. Patients with hindfoot deformities, previous surgeries, prior ankle or hindfoot fractures, or degenerative joint changes were excluded from the study. Results: The study included 16 patients in the ankle instability group and 16 patients in the non-instability group. The mean MTI was 89.3° in the ankle instability group, significantly higher than the 85.6° in the non-instability group (p = 0.00058). The mean age was 39.2 years in the instability group, compared to 45.7 years in the non-instability group. The ankle instability group consisted of 14 males and 2 females, while the non-instability group included 10 males and 6 females. Five patients in the ankle instability group had undergone surgery to stabilize lateral ligaments. Conclusion: This study highlights the utility of weight-bearing CT in dynamically assessing and diagnosing lateral ankle instability. The increased internal rotation of the talus, as indicated by the MTI, provides a reliable method to evaluate dynamic ankle instability. These findings support the use of weight bearing CT as a valuable tool in the clinical assessment of lateral ankle instability, offering insights beyond traditional imaging techniques.