Anterior Talar Displacement Differs Among Controls, Copers, and Individuals with Chronic Ankle Instability

Abstract

Chronic ankle instability (CAI) develops in 40-75% of people after an ankle sprain. Yet, some people (copers) maintain dynamic activities and are thought to possess a mechanism that limits the impairments seen in CAI. Understanding the differences between joint structural alignment measures in copers and CAI patients may elucidate the coping mechanisms present in copers but absent in CAI patients. PURPOSE: To determine if anterior talar displacement differs among controls, copers, and CAI patients. METHODS: 72 subjects (21.4±2.4 yrs), 24 in each group, were assessed for the magnitude (mm) of sagittal plane talar displacement in each leg. Copers and CAI subjects had at least one previous moderate ankle sprain but copers resumed all pre-injury activity without limitation or recurrent injury while CAI patients had recurrent sprains and giving way episodes. Talar position was calculated by measuring the distance between the anterior margin of the talus and the anterior margin of the tibia from a lateral radiographic image. The average of three measurements was recorded and used for further analysis. One-way ANOVA and paired sample t-tests were calculated to determine group and side-to-side differences within each group respectively. Intra-class correlation coefficients were calculated to determine the intra- and inter-tester reliability of the measurement technique and a priori alpha level of P ≤0.05 was used for all statistical analyses. RESULTS: A significant group main effect [F(2,71)=4.89, p=0.01] indicated that the talus of subjects with CAI (3.69±1.36mm) was significantly more anterior than the talus of controls (2.34±1.32mm) and copers (3.12±1.62mm). Copers did not differ from controls (p=0.17) or CAI subjects (p=0.42). Side-to-side differences were also noted with the CAI group (injured: 3.70±1.34mm, uninjured: 2.98±161mm) but not the coper (p=0.22) or control (p=0.11) group. Further, the measurement technique was found to have good intra- (r =0.83) and inter-tester (r =0.82) reliability. CONCLUSION: Those with CAI displayed an anteriorly displaced talus relative to controls while copers did not. This finding suggests that anterior talar displacement provides insight into the coping mechanism absent in those with CAI. Supported by the University of Florida, CHHP Opportunity Fund.