[The Value of Ultrasonography Compared with Magnetic Resonance Imaging in the Diagnosis of Deltoid Ligament Injuries--Is there a Difference?].

Background: Ruptures of the deltoid ligament can lead to ankle instability which may cause arthrosis. Aim of this comparative clinical trial was to assess the value of ultrasonography (US) compared to magnetic resonance imaging (MRI) in the diagnosis of medial collateral (deltoid) ligament ruptures associated with Weber type B and C fractures. Patients and Methods: All four components of the deltoid ligament of the ankles of 28 patients with Weber type B and 14 patients with Weber type C fractures were preoperatively evaluated by US and MRI for partial or complete ruptures. Results: Deltoid ligament injuries were detected in 10 of 28 patients (35.7%) with Weber type B and in 12 of 14 patients (85.7%) with Weber type C fractures with MRI. US reliably identified all 17 patients with complete rupture of the deltoid ligament (sensitivity 100%, specifity 92%). However only half of the 6 patients who sustained a partial rupture were correctly identified (sensitivity 50%, specifity 97.2%). 26 of 30 ruptures (sensitivity 86.6%, specifity 96.3%) and 13 of 27 partial ruptures (sensitivity 48.1%, specifity 97.8%) of the four components of the deltoid ligament were correctly identified with US. Conclusion: US is a reliable procedure for detection of clinically relevant ruptures and uninjured components of the deltoid ligament after distal fibula fractures. However US is not suitable to reliably identify partial ruptures. The treatment decision for operation or conservative treatment of ankle fractures is based on the stability of the ankle. Patients with lateral malleolar fractures and intact medial malleolus but rupture of the deltoid ligament often show a spontaneous reduction of the talus in X-ray images and may therefore be falsely classified as stable (unrecognised medial instability). However, unstable malleolar fractures should be treated with open reduction and internal fixation in order to improve outcome. Hence US is able to influence therapeutic decisions by detecting medial ankle instability, which cannot be detected clinically or radiologically.