MAGNETIC-RESONANCE-IMAGING OF MENISCAL AND ANTERIOR CRUCIATE LIGAMENTINJURIES OF THE KNEE

Purpose: To categorise discrepancies in findings of the menisci and an terior cruciate ligament (ACL) between arthroscopy and MRI. Materials and methods: The MRIs of 236 patients were retrospectively analysed by an experienced radiologist without knowledge of clinical and/or opera tive findings. Discrepancies in arthroscopic findings were reevaluated together with the arthroscopist to determine their cause of error. Re sults: The diagnostic accuracies for injuries of the medial and latera l meniscus and the ACL were 92.4%, 92.4%, and 94.1 %, respectively. Fo r the menisci, causes for discrepancies in findings (n=31) were: overi nterpretation of central signal intensities with contact to the menisc al surface but without disturbance of the meniscal contour as a tear ( n = 12), insufficient arthroscopie evaluation of the knee joint (n=11) , overlooked tears on MR imaging (n=6), misinterpretation of normal an atomic structures (n=1), ''magic angle'' phenomenon (n=1), and missed tears at MRI (n = 1). Causes for discrepancies for the ACL (n=18) were : nearly complete versus complete rupture either at MRI or arthroscopy and vice versa (n = 9), insufficient arthroscopic evaluation (n=6), i nsufficient MRI technique (n=2), and overlooked tear on MR imaging (n= 1). Conclusions: Discrepant findings between MRI and arthroscopy may b e also due to an insufficient arthroscopic evaluation in clinical rout ine. The close cooperation between surgeons and radiologists improves the understanding of the methods of each other.