4DCT evaluation of rotational instability and subtalar joint motion in ankle osteoarthritis: a stage-based comparative study.

OBJECTIVES

To dynamically evaluate tibiotalar rotational instability and subtalar joint mobility in patients with Ankle Osteoarthritis (AOA) across different disease stages using four-dimensional computed tomography (4DCT).

METHODS

Sixty ankles were assessed using 4DCT: 10 healthy controls and 50 AOA cases classified according to the Takakura-Tanaka classification (Stage 1-2: n = 10; Stage 3a: n = 13; Stage 3b: n = 13; Stage 4: n = 14). 4DCT was used to assess three Angular Parameters: Axial Tibiotalar Angle (ATTA), Axial Talocalcaneal Angle (ATCA), and Coronal Talocalcaneal Angle (CTCA). Changes in joint angles between neutral and extreme positions (ΔATTA, ΔATCA, ΔCTCA) were analyzed. Kruskal-Wallis and Dunn's post hoc tests were used for group comparisons (p < 0.05).

RESULTS

ΔATTA significantly differed among groups (p = 0.009), with values of 12.4°±3.6 (healthy), 15.9°±4.0 (Stage 1-2), 19.3°±8.0 (3a), 17.3°±7.1 (3b), and 8.8°±5.3 (4). Stage 4 showed significantly reduced ΔATTA compared to Stages 2-3b. ΔCTCA also differed significantly (p < 0.001): 30.8°±8.2 (healthy), 29.1°±9.2 (1-2), 25.9°±8.8 (3a), 14.6°±7.0 (3b), and 13.5°±7.3 (4). ΔATCA showed no significant group differences (p = 0.19). Static angles (ATTA, ATCA, CTCA) did not show consistent differences.

CONCLUSION

4DCT enabled the identification of stage-specific patterns in AOA. Tibiotalar rotational instability appeared early and peaked in stage 3a, then decreased in stage 4. In contrast, the subtalar rotational mobility did not significantly change across stages. Dynamic parameters were more sensitive than static angles in identifying functional joint changes, and 4DCT may be an option for evaluating the pathology of AOA.