The value of secondary MRI signs of an ACL lesion: comparison with arthroscopy

Primary MRI signs are sometimes insufficient for the diagnosis of anterior cruciate ligament (ACL) tears and the observation of secondary signs (impingement of the tibial plateau, augmented PCL curvature, anterior tibia] dislocation) may be of great assistance. This paper assesses the sensitivity and specificity of the primary and secondary MRI signs in the light of the arthroscopic findings in 50 patients with suspected ACL damage. MR imaging was conducted with specific surface coils and weighted T1 and T2 spin echo and gradient echo sequences. Sensitivity and specificity for the primary signs were 94% and 92%. The corresponding values for the secondary signs were: impingement 88% and 100%; augmented PCL curvature 70% and 89%; anterior dislocation 31% and 98%. These results indicate that MRI diagnosis of ACL tears based on primary signs (morphology and signal intensity) is more sensitive and specific. Diagnostic accuracy can be considerably improved in doubtful cases by resorting to the highly specific secondary signs. (C) 2001, Editrice Kurtis.