Accuracy of direct signs of tears of the anterior cruciate ligament

OBJECTIVE: To evaluate the accuracy of direct magnetic resonance imaging (MRI) signs of tears of the anterior cruciate ligament. PATIENTS AND METHODS: Over the period April 1991 to February 1994, 92 consecutive MRI studies of the knee were obtained for which arthroscopic data were also available. The MRI studies were retrospectively evaluated for course, continuity, signal intensity, morphologic features, contour and visualization of the anterior cruciate ligament. Arthroscopic findings were correlated with individual primary signs and the overall MRI diagnosis. RESULTS: Among the cases studied were 4 partial and 32 complete tears of the anterior cruciate ligament (as determined by arthroscopy). Because of the low number of partial tears, it was not possible to draw any meaningful conclusions about the MRI diagnosis of this type of tear. For complete tears, the criteria with the highest accuracy were abnormal course of the ligament (96.0%) and high signal intensity (89.3%). The overall diagnostic accuracy of MRI was 98.8%. CONCLUSIONS: The most accurate direct MRI finding in patients with a complete tear of the anterior cruciate ligament was abnormal course of the ligament, followed by abnormally high signal intensity.