Application of High-Speed Dual Fluoroscopy to Study In Vivo Tibiotalar and Subtalar Kinematics in Patients With Chronic Ankle Instability and Asymptomatic Control Subjects During Dynamic Activities

Abnormal angular and translational (ie, kinematic) motion at the tibiotalar and subtalar joints is believed to cause osteoarthritis in patients with chronic ankle instability (CAI).In this preliminary study the investigators quantified and compared in vivo tibiotalar and subtalar kinematics in 4 patients with CAI (3 women) and 10 control subjects (5 men) using dual fluoroscopy during a balanced, single-leg heel-rise and treadmill walking at 0.5 and 1.0 m/s.During balanced heel-rise, 69%, 54%, and 66% of mean CAI tibiotalar internal rotation/external rotation (IR/ER), subtalar inversion/eversion, and subtalar IR/ER angles, respectively, were outside the 95% confidence intervals of control subjects. During 0.5-m/s gait, 50% and 60% of mean CAI tibiotalar dorsi/plantarflexion and subtalar IR/ER angles, respectively, were outside the 95% confidence intervals of control subjects. During 1.0-m/s gait, 62%, 65%, and 73% of mean CAI subtalar dorsi/plantarflexion, inversion/eversion, and IR/ER, respectively, were outside the 95% confidence intervals of control subjects. Patients with CAI exhibited less tibiotalar and subtalar translational motion during gait; no clear differences in translations were noted during balanced heel-rise.Overall, the balanced heel-rise activity exposed more tibiotalar and subtalar kinematic variation between patients with CAI and control subjects. Therefore, weight-bearing activities involving large range of motion, balance, and stability may be best for studying kinematic adaptations in patients with CAI.These preliminary results suggest that patients with CAI require more tibiotalar external rotation, subtalar eversion, and subtalar external rotation during weight-bearing stability exercises, all with less overall joint translation.