TEARS OF THE ANTERIOR CRUCIATE LIGAMENT - PRIMARY AND SECONDARY SIGNSAT MR-IMAGING

To investigate primary and secondary signs of anterior cruciate ligame nt (ACL) tear at magnetic resonance (MR) imaging, the authors retrospe ctively reviewed 103 MR imaging examinations obtained in 99 patients, the original interpretations of these examinations, clinical records, and arthroscopy reports. Fifty cases of arthroscopy-documented complet e ACL tear were included. The primary signs of ACL tear (ie, abnormal ACL morphologic features or signal intensity) had respective sensitivi ty and specificity values of 96% (48 of 50 examinations) and 94% (50 o f 53) on sagittal images and 92% (46 of 50) and 83% (43 of 52) on coro nal images. As a secondary sign of ACL tear, bone bruise involving the lateral compartment of the knee was found in 40% (20 of 50) of cases of ACL tear and in 4% (2 of 53) of cases of normal ACL. The mean curva ture of the posterior cruciate ligament was increased (0.40 vs 0.27; P < .0001) in cases of ACL tear. An abnormal appearance of the ACL on s agittal images remains the single most sensitive and specific sign of ACL tear.