Chronic Ankle Instability Influences Laxity and Stiffness during Anterior Drawer But Not Inversion Talar Tilt

Abstract

PURPOSE: To assess ankle laxity and stiffness during the anterior drawer and talar tilt tests with an instrumented arthrometer in individuals with and without chronic ankle instability (CAI). METHODS: Twenty-seven subjects with CAI (20 females, 7 males) and 20 healthy control subjects (14 females, 6 males) participated. The CAI subjects had an average of 5.5 +/− 3.7 previous ankle sprains, and scores of 89.0 +/− 7.5 percent and 74.9 +/− 14.0 percent on the Foot and Ankle Disability Index Main and Sport scales, respectively. An ankle arthrometer was used to perform an anterior drawer test to a load of 125 N and an inversion talar tilt test to 4000 N-mm. For both tests, laxity was quantified as the amount of maximal displacement and stiffness was estimated by calculating the slope of the force displacement curve. RESULTS: The CAI group had significantly greater anterior drawer laxity on their involved ankles (11.1 +/− 4.3 mm) than the control group had on their side-matched ankles (7.6 +/− 3.8 mm) (p=.006). The CAI group (14.3 +/− 10.3) also demonstrated significantly less stiffness during the anterior drawer test than the control group (18.4 +/− 8.9 mm) on the involved ankles (p=.028). There were no significant differences between the anterior drawer measures on the uninvolved ankles in the CAI group and the side-matched limbs in the control group. For the inversion talar tilt measures, there were no significant differences in laxity or stiffness between groups on either the involved or uninvolved ankles. CONCLUSIONS: Laxity and stiffness deficits were found in the CAI group with the anterior drawer test, but not the inversion talar tilt test. These results indicate residual mechanical insufficiency of the anterior talofibular ligament, but not the calcaneofibular ligament, in those with CAI. Mechanical deficiency of the anterior talofibular ligament alone, without concurrent involvement of the calcaneofibular ligament, may be sufficient to contribute to the development of CAI.