Synovialisation of the torn anterior cruciate ligament of the knee: comparison between magnetic resonance and arthroscopy

The aim of this study was to assess the accuracy of MR in the diagnosis of synovialisation of the anterior cruciate ligament (ACL) compared with arthr oscopy. One hundred and forty-nine patients were examined with MR imaging a nd arthroscopy of the knee. The MR sign used to consider a synovialised ACL consisted of hypointense fibrillar tracts, disrupted and wavily, in its ex pected course. Sensitivity, specificity, positive predictive value (PPV) an d negative predictive value (NPV), comparison of proportions (McNemar test) and Kappa values for agreement between MR imaging and arthroscopy were cal culated. Of the 133 (89.3%) ligaments without synovialisation at arthroscop y, 130 accorded with the MR results. Of the 16 (10.7%) synovialised ligamen ts, 13 accorded with the MR results. Three false-positive and three false-n egative MR diagnoses were identified. The agreement between both techniques was excellent (Kappa = 0.79; p = 0.000), without differences (McNemar test ; p = 1). Sensitivity was 0.81, specificity 0.98, PPV 0.98 and NPV 0.81, Ma gnetic resonance imaging is highly reliability for synovialisation diagnosi s. The imaging sign used to diagnose synovialised ACL (hypointense comma-li ke tracts in its expected course) is reliable. As this reparative process c an simulate an intact ligament, knowledge of this sign is important in diag nosing synovialisation of ACL tears so as not to confuse it with normal ACL .