Anterolateral fibrous impingement of the ankle. Report of 14 cases

PURPOSE: Anterolateral fibrous impingement of the ankle is one of the causes of post-traumatic pain in the foot. We investigated the comparative accuracy of US and MRI in this condition. MATERIAL AND METHODS: Fourteen patients were submitted to arthroscopy, plain radiography, US and MRI of the foot. The patients, all sportsmen, had a clinical history of sprains; the major symptoms were pain, swelling and clicking on foot dorsiflexion. RESULTS: US showed anterior talofibular ligament changes in all patients and mid-low-echogenicity synovial tissue filling the lateral malleolar gutter. MRI demonstrated a small mass of synovial tissue in the gutter in 8 patients, with mid-low signal intensity before Gd-DTPA and mid-low contrast enhancement after contrast administration and no abnormal findings in 6 patients. Arthroscopy showed a small firm mass of proliferative synovium in the lateral malleolar gutter in all patients. CONCLUSIONS: Fibrous impingement must be suspected in the sportsmen presenting typical symptoms after ankle trauma. US is poorly accurate in diagnosing this condition. MRI shows a small synovial mass in the lateral malleolar gutter in more than half the patients, but aspecific MR findings do not rule impingement our MR images must be acquired along the proper planes and with Gd-DTPA administration.