Anterolateral impingement of the ankle: Effectiveness of MR imaging

PURPOSE: To determine the effectiveness of magnetic resonance (MR) imaging in the diagnosis of anterolateral impingement of the ankle. MATERIALS AND METHODS: MR images were reviewed in 12 patients (12 ankles) with arthroscopically proved anterolateral impingement and in 19 control subjects (20 ankles) with diagnoses other than impingement. MR images were scored by means of consensus of two musculoskeletal radiologists and independently by a third radiologist. Patients underwent imaging at 1.5 T, with use of standard imaging sequences and a dedicated extremity coil. RESULTS: For the consensus reading, the sensitivity, specificity, and accuracy of MR imaging for the diagnosis of impingement were 42%, 85%, and 69%, respectively. The frequency of lateral gutter fullness and anterior talofibular ligament thickening on MR images was higher in the 12 ankles with impingement (seven [58%] and seven [58%] ankles, respectively) than in the 20 control ankles (seven [35%] and five [25%] ankles, respectively), but these trends did not reach statistical significance. Interobserver agreement for anterior talofibular ligament thickening was high, whereas that for lateral gutter fullness was fair. CONCLUSION: Conventional MR imaging of the ankle is insensitive for anterolateral impingement. Anterior talofibular ligament thickening and soft-tissue fullness in the lateral gutter may be suggestive of the diagnosis, but the reliability of the latter finding is questionable.