Magnetic Resonance Imaging and Stress Radiography in Chronic Lateral Ankle Instability.

BACKGROUND: Studies regarding magnetic resonance imaging (MRI) findings of the lateral ankle ligaments in chronic lateral ankle instability and their clinical relevance for surgery are lacking. This study classified the lateral ankle ligament MRI findings of the anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL) in chronic lateral ankle instability (CLAI) and correlated these findings with ankle stress radiographs.

METHODS: We included 132 ankles with CLAI that underwent ligament reconstructions from 2006 to 2013. The distributions of the ATFL and CFL morphologies were evaluated using the following categories: (1) the amount of thickness: normal/thickened/attenuated/non-visualized, (2) the presence of discontinuity, (3) wavy or irregular contour, and (4) increased signal intensity on T2-weighted images. The relationships between the ligament morphologies and stress radiographs were analyzed.

RESULTS: The ATFL was normal in 5 (4%) ankles, thickened in 35 (27%), attenuated in 76 (58%), and non-visualized in 16 (12%), while the CFL was normal in 39 (30%) ankles, thickened in 42 (32%), attenuated in 44 (33%), and non-visualized in 7 (5%). Discontinuity of the ATFL or CFL was observed in 46 (35%) ankles. Wavy or irregular contours were observed in 55 (42%) ATFLs and 37 (28%) CFLs, and signal intensity of both ligaments was increased in 19 (14%) ankles. ATFL ( P < .001) and CFL thickness ( P = .007) correlated with the talar tilt angle.

CONCLUSIONS: The MRI findings of CLAI showed several morphologies and specific incidences for each morphology. Attenuated, wavy appearance was the most frequent MRI pattern. Thickness was related to the degree of instability.

LEVEL OF EVIDENCE: Level IV, retrospective case series.