Guiding acute repair decisions of MCL injuries with a novel MRI classification system: a retrospective study of 226 cases with MRI and intraoperative findings.

Objective: This study aimed to investigate the relationship between magnetic resonance imaging (MRI) findings and intraoperative findings of Grade III medial collateral ligament (MCL) injuries to validating the diagnostic accuracy of MRI in localizing the tear and exploring the distribution of tear locations in these injuries. Methods: We reviewed 226 patients with MCL repair surgery and introduced a novel MRI-based classification system. MCL tears were classified into types 1a, 1b, 2a, 2b, 3, 4a, and 4b based on their location relative to the seven attachments. We then recorded tear locations and calculated the incidence of each type. The Kappa statistic was used to assess both the agreement between MRI and intraoperative classifications and inter-observer reliability. The sensitivity, specificity and accuracy (95% CIs) of MRI for localizing tears were calculated against intraoperative findings. Results: There was good inter-observer ( Conclusion: The MRI classification system provides high diagnostic accuracy in locating MCL tears, particularly POL tears, for which the adductor tubercle serves as a reliable reference. Thus, this system confirms that the presence of a POL tear is a key factor guiding acute MCL repair.