Evaluation of lateral ankle instability with weight-bearing MRI. Preliminary Experience

PURPOSE/INTRODUCTION: To assess the usefulness of weight-bearing examination of the ankle performed with a dedicated MRI scanner in the evaluation of patients with clinical evidence of lateral ankle instability. MATERIALS AND METHODS: We retrospectively evaluated ankle MR examinations of 18 patients, performed between September 2008 and January 2009. Spin echo T1W, Turbo Spine Echo T2W, 3D Steady-State (SSE) and Short Tau Inversion Recovery (STIR) images were acquired with a 0.2 T scanner (G-Scan, Esaote Spa, Genoa, Italy) in both weight-bearing position and normal conventional supine position. A dedicated extremities receiver coil was used. If present, signs of instability and ligament signal intensity changes were evaluated in consensus by three musculoskeletal experienced radiologists. RESULTS: The conventional supine position showed a partial tear of anterior talo-fibular (ATF) ligament in 12/18 patients, a complete tear of ATF ligament and a partial tear of the calcaneo-fibular (CF) ligament in 3/18 patients, while in the remaining 3 patients there was presence of post-traumatic bone oedema without ligament disruption. The weight-bearing position showed that in 5/12 patients with a partial tear of ATF ligament seen in normal conventional supine position there was instead a complete tear of ATF ligament along with a partial tear of CF ligament. Moreover, only in the weight-bearing position a subtle plantar fascia partial tear was detected in one case, while in the conventional supine position there was evidence only of high-grade plantar fasciitis. In the remaining patients, conventional supine position and weight-bearing position demonstrated the same lesions without lesion grading changes. DISCUSSION/CONCLUSION: Imaging the ankle in weight-bearing position with a new developed MRI scanner is useful in demonstrating complete tears of the ATF ligament that are doubtful or defined as “partial tear” in normal conventional supine position. Moreover, in one case the weight-bearing position showed occasionally a subtle plantar fascia tear, which can be overlooked when imaging the ankle only in supine position. 1. Alparslan L, Chiodo CP. Lateral ankle instability: MR imaging of associated injuries and surgical treatment procedures. Semin Musculoskelet Radiol. 2008 Dec;12(4):346-58. 2. Campbell SE, Warner M. MR imaging of ankle inversion injuries. Magn Reson Imaging Clin N Am. 2008 Feb;16(1):1-18. 3. Kirby AB, Beall DP, Murphy MP, Ly JQ, Fish JR. Magnetic resonance imaging findings of chronic lateral ankle instability. Curr Probl Diagn Radiol. 2005 Sep-Oct;34(5):196-203. 4. Chandnani VP, Harper MT, Ficke JR, Gagliardi JA, Rolling L, Christensen KP, Hansen MF. Chronic ankle instability: evaluation with MR arthrography, MR imaging, and stress radiography. Radiology. 1994 Jul;192(1):189-94. 5. Rijke AM, Goitz HT, McCue FC 3rd, Dee PM. Magnetic resonance imaging of injury to the lateral ankle ligaments.Am J Sports Med. 1993 Jul-Aug;21(4):528-34.