Characterization of Ankle Kinematics and Constraint Following Ligament Rupture in a Cadaveric Model

Abstract

Ankle sprains are a common injury that may need reconstruction and extensive physical therapy. The purpose of this study was to provide a description of the biomechanics of the ankle joint complex (AJC) after anterior talofibular (ATFL) and calcaneofibular (CFL) ligament rupture to better understand severe ankle injuries. The envelope of motion of ten cadaveric ankles was examined by manual manipulations that served as training data for a radial basis function used to interpolate ankle mobility at flexion angles under load and torque combinations. Moreover, ankle kinematics were examined, while tendons were loaded to identify how their performance is altered by ligament rupture. The increased force required to plantarflex the ankle following ligament rupture was measured by calculating the load through the Achilles. Following ATFL injury, the largest changes were internal rotation (5 deg) in deep plantarflexion and anterior translation (1.5 mm) in early plantarflexion. The combined ATFL and CFL rupture changed the internal/external rotation (3 deg), anterior/posterior translation (1 mm), and inversion (5 deg) throughout flexion relative to the isolated ATFL rupture. Moreover, the Achilles' load increased by 24% after the rupture of ligaments indicating a reduction in its efficiency. This study suggests that if patients demonstrate primarily an increased laxity in internal rotation, the damage has solely occurred to the ATFL; however, if the constraint is reduced across multiple motions, there is likely damage to both ligaments. Higher loads in the Achilles suggest that it is overloaded after the injury; hence, targeting the calf muscles in rehabilitation exercises may reduce patients' pain.