Mechanical Instability After an Acute Lateral Ankle Sprain

Abstract

Hubbard TJ, Cordova M. Mechanical instability after an acute lateral ankle sprain. Objective To examine the natural recovery of mechanical laxity after an ankle sprain over an 8-week period. Design Prospective cohort study. Setting Biodynamics research laboratory. Participants Subjects with an acute lateral ankle sprain (n=16; 7 men, 9 women; age, 19.5±0.7y; mass, 64.6±8.1kg; height, 171.9±9.6cm) and healthy controls (n=16; 7 men, 9 women; age, 20.4±1.7y; mass, 76.9±11.1kg; height, 176.5±11.1cm) participated. Interventions Not applicable. Main Outcome Measures Subjects with acute ankle sprains were tested 3 days after injury and again 8 weeks later. Anterior and posterior displacement (mm) and inversion and eversion rotation (°) were measured with an instrumented arthrometer. For each dependent variable, a 2 × 2 × 2 repeated-measures multivariate analysis of variance was performed. Results A significant interaction was found between group, time, and side for anterior translation (F=4.24, P=.05). There were also significant main effects for group. There was significantly more anterior displacement at day 3 (F=19.52, P=.001) and at week 8 (F=8.45, P=.010) in the injured group compared with the healthy group. There was also significantly more inversion rotation at day 3 (F=2.70, P=.002) and at week 8 (F=5.4, P=.033) in the injured group compared with the healthy group. Conclusions The lack of significant differences in mechanical laxity over an 8-week period suggests that natural recovery of laxity takes longer than 8 weeks. Further research needs to be conducted to examine how long this laxity persists and the role ankle rehabilitation plays in mechanical stability restoration.