Objectives: Sonography during externally applied stress has the potential to identify ligamentous instability, but diagnostic parameters for the most commonly sprained ankle ligament, the anterior talofibular ligament (ATFL), have not yet been established. The purpose of this study was to determine normative values of the change in the length of the ATFL in an asymptomatic population during manual stress sonography and to compare these values to those in patients with clinical findings of anterolateral ankle instability.
Methods: Sonography of the ATFL at rest and with maximally applied manual stress was performed bilaterally in 20 asymptomatic volunteers from each of three 10-year age groups from 20 to 50 years. Data were compared to those for 34 patients retrospectively identified who underwent stress sonography of the ATFL for clinical signs and symptoms of chronic anterolateral ankle instability.
Results: In the asymptomatic population (10 men and 10 women), for men, the mean change in ATFL length between stress and neutral positions was 0.44 mm (95% confidence interval [CI], 0.32-0.57 mm). For women, it was 0.43 mm (95% CI, 0.31-0.55 mm). The difference in laxity between sexes was not significant (P = .85). In the symptomatic population, the mean ATFL length difference between stress and neutral positions was 1.26 mm (95% CI, 0.97-1.55 mm). A t test comparing the mean change in ATFL length showed a statistically significant increase in laxity in the symptomatic group (P < .0001).
Conclusions: The normal ATFL shows minimal laxity in both men and women on stress sonography, with significantly greater laxity among patients with ankle instability. Given these findings, stress sonography may have an important role in the imaging diagnosis of anterolateral ankle instability.
Keywords: ankle instability; anterior talofibular ligament; extremities; musculoskeletal (diagnostic); normal ligamentous length; sonography.
© 2018 by the American Institute of Ultrasound in Medicine.