ACL partial tears: Is it possible to define which bundle is compromised using magnetic resonance?

OBJECTIVE: Anterior Cruciate Ligament (ACL) tears are diagnosed through a clinical examination and imaging confirmation. Magnetic Resonance Imaging (MRI) is the diagnostic image method of choice; however the sensitivity is variable for the different kind of partial injuries. The objective of this study is to evaluate the effectiveness of the MRI in the diagnosis of clinically unstable partial ACL tears that already underwent surgical treatment and define which bundle was compromised. METHODS: A retrospective review of the preoperative MRI of 40 patients who were surgically operated because of ACL tears was executed. In all cases, arthroscopic findings defined one bundle was intact. All MRI were reviewed by a single osteo-articular specialist staff of the Image Department. All injuries were classified according to which bundle was involved (anteromedial (AM) or posterolateral (PL)). Results were compared with the surgical findings. RESULTS: Concordance between MRI and arthroscopic findings was 42.5% (17/40 patients). If we analyze AM and PL tears separately we found that the concordance was 51.5% for AM bundle tears (17/33) and 0% for PL bundle tears (0/7). CONCLUSION: Definitive diagnosis and surgical indication for ACL tears requires both, clinical examination and image diagnosis. Over 65% of partial tears are misdiagnosed by MRI only.