[Lesions of the collateral ligaments of the ankle: diagnosis and follow-up with magnetic resonance and ultrasonography].

Acute sprains are one of the most frequent ankle conditions; the lateral collateral ligaments are often involved. Currently, plain radiography and clinical examination are the methods of choice in the management of these injuries. This study was aimed at describing the MR findings of acute ankle sprains, to assess which ligaments are involved, to study the repair process during conservative treatment and, finally, to compare MR and US findings in acute and chronic injuries. We divided our study into a prospective and a retrospective parts. In the prospective study, MRI was performed in 20 consecutive patients with acute ankle sprain diagnosed at the emergency care unit of our institute and treated conservatively with braces. The patients with fractures were excluded. Follow-up was based on a series of MR exams performed every 30 days for 6 months. We diagnosed 18 injuries of the lateral collateral ligaments, 5 of the anterior talofibular ligament (ATFL) (2 partial and 3 complete tears) and 13 of both the ATFL and the calcaneofibular (CFL) (6 partial and 7 complete tears). The follow-up showed complete edema resorption at 30 days in 2 patients with no ligament injuries; the persistence of a medium-large amount of fluid in partial tears at 30 days and its complete resorption at 60 days; and, finally, the persistence of a medium-large amount of fluid at 180 days in 2 complete tears. No scar could be identified in all the patients with ligament injuries. The retrospective study was based on the comparison of MR (gold standard) and US findings in 78 patients with ankle sprain, 28 in the acute and 50 in the chronic phase. In the first group we found 9 ATFL injuries (6 partial and 3 complete tears), 5 ATFL and CFL injuries (3 partial and 2 complete tears), 2 complete tears of lateral collateral ligaments, 3 deltoid ligament (DL) injuries, 2 ATFL and DL injuries and 2 injuries of both lateral and medial collateral ligaments. US was in agreement with MRI in 85% of ATFL, 67% of CFL and 28% of DL injuries; US also yielded 2 false positives in PAA. In the second group of 50 patients, MRI showed 11 ATFL and 8 ATFL and CFL injuries, 3 injuries of lateral collateral ligaments, 6 DL and 8 ATFL, CFL and DL injuries and 5 complete tears of both internal and external collateral ligaments; 10 exams were negative. US had 58% agreement with MRI in ATFL, 46% in CFL and 21% in DL injuries. In this series, US yielded 3 false positives in PAA injuries.