Radiographic Evaluation of Ankle Joint Stability

Abstract

Ankle joint stability was evaluated in 120 patients with functional instability (FI) of the ankle and in a control group with functionally stable (FS) ankle joints. It was also compared in patients with unilateral ankle joint instability. The radiographic investigation was standardized using the same method, instruments, and calculations. The anterior talar translation (ATT) for men was 10.5 mm (range 8–15 mm) in functionally unstable ankle joints and 7.3 mm (range 4–11 mm) in the control group (p < 0.001). The corresponding values for women were 11.3 mm (range 6–24 mm) and 7.2 mm (range 3–12 mm) (p < 0.001). The talar tilt (TT) was significantly (p < 0.001) higher in the functionally unstable ankle joints than in the control group: 10° (range 3°-27°) and 3.2° (range 0°-8°) for men and 11° (range 2°-23°) and 4.3° (range 0°-8°) for women. ATT in patients with unilateral functional instability was 11.1 mm (range 7–20 mm) as compared with 7.9 mm (range 4–11 mm) in the stable group (p < 0.001). TT was 9.5° (range 3°-23°) degrees in the functionally unstable ankles as compared with 4.4° (range 2°-8°) in the stable ankles (p < 0.001). The mean difference between functionally stable and unstable ankle joints was 3.2 mm (ATT) and 5.1° (TT). Mechanical instability (MI) can be defined as an ATT ≥ 10 mm and a TT ≥ 9°, or a difference in ATT and TT between stable and unstable ankle joints >3 mm and 3°, respectively. Mechanical instability is an important factor in development of functional instability of the ankle. Standardized stress radiographs are of definite value in diagnostic evaluation of ankle joint stability.