ANTERIOR CRUCIATE LIGAMENT TEAR - INDIRECT SIGNS AT MR-IMAGING

PURPOSE: To establish the sensitivity and specificity of indirect sign s at magnetic resonance (MR) imaging of anterior cruciate ligament (AC L) tear. MATERIALS AND METHODS: MR images of the knees of 89 consecuti ve patients (54 with torn and 35 with normal ACLs) were reviewed. RESU LTS: The indirect signs were as follows (first percentage is sensitivi ty; the second, specificity): angle between lateral tibial plateau and ACL less than 45 degrees (90%, 97%); angle between Blumenstaat line a nd ACL more than 15 degrees (89%, 100%); bone contusions in lateral co mpartment (54%, 100%); position of posterior cruciate ligament (PCL) l ine (52%, 91%); PCL angle less than 107 degrees (52%, 94%); PCL bowing ratio more than 0.39 (34%, 100%); posterior displacement of lateral m eniscus more than 3.5 mm (44%, 94%); anterior displacement of tibia mo re than 7 mm (41%, 91%); and lateral femoral sulcus deeper than 1.5 mm (19%, 100%). CONCLUSION: Because the specificity is high, the presenc e of indirect signs corroborates the diagnosis of ACL tear. Because th e sensitivity is low, the absence of these signs does not exclude the diagnosis of ACL tear.