The Bright Rim Sign on MRI for Anterior Talofibular Ligament Injury With Arthroscopic Correlation

OBJECTIVE. The purpose of this article is to determine whether bright rim lesions on MRI are a marker for anterior talofibular ligament injury. MATERIALS AND METHODS. The study included 34 patients who had an ankle injury and underwent arthroscopic surgery. All patients underwent 3-T MRI for the diagnosis of anterior talofibular ligament injury. If MRI revealed nonvisualization of the ligament, ligament discontinuity, and unusual ligament thickening (criterion 1) or the bright rim sign (criterion 2), the injury was considered to be a ligament disruption. After MRI, ankle arthroscopy was performed in all patients for a definitive diagnosis. RESULTS. Arthroscopy showed anterior talofibular ligament disruption in 33 patients. When the MRI diagnosis was based on criterion 1, anterior talofibular ligament disruption was diagnosed with a sensitivity of 60.6-66.7% and an accuracy of 58.8-67.6%. When the MRI diagnosis was based on both criteria 1 and 2, anterior talofibular ligament disruption was diagnosed with a sensitivity of 90.9-97.0% and an accuracy of 88.2-94.1%. By adding criterion 2 to the diagnosis, the sensitivity for anterior talofibular ligament injury was increased significantly (p < 0.01), and 8-12 additional patients with anterior talofibular ligament injury were diagnosed, most of whom exhibited a partial tear of the anterior talofibular ligament on arthroscopy. The interobserver agreement rate for the presence of anterior talofibular ligament disruption using criterion 1, both criteria, and the bright rim sign was fair to excellent. CONCLUSION. A cortical defect with bright dotlike or curvilinear high-signal-intensity lesions on T2-weighted MRI may be an additional morphologic feature to increase the diagnostic performance of detecting anterior talofibular ligament injuries, including those with partial tears.