Three-dimensional kinematics of ankle instability following serial sectioning of lateral collateral ligaments.

Triaxial kinematics of ankle instability were studied in vitro by applying an inversion force to seven nonaxially loaded cadaveric ankle-foot specimens. In intact specimens, mean maximal adduction of the tibia with respect to the calcaneus was 38 degrees and mean maximal external rotation was 24 degrees; maximal displacement occurred near full plantar flexion. Increases after release of ligaments were as follows: calcaneofibular, maximal adduction 10%, external rotation 3% near 15 degrees of plantar flexion; anterior talofibular, adduction 30%, external rotation 8% at 30 degrees of plantar flexion; both, adduction 41%, external rotation 65% near 0 degree of flexion; all three lateral collateral, adduction 42%, external rotation 240% in slight dorsiflexion. Regardless of the status of the lateral collateral ligaments, the talus adducted and externally rotated 18 degrees +/- 1 degree with respect to the calcaneus. Hence, collateral ligament release had no effect on subtalar motion.