Shaofeng Yang

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 ( k = 0.63, P < 0.001) and substantial intraoperative ( k = 0.92, P < 0.001) agreement for the MRI classifications. MRI demonstrated high diagnostic performance across all locations. Sensitivity ranged from 81.8% (95% CI: 47.8%–96.8%) for location S2 to 100% for locations P1 (95% CI: 97.0%–100.0%) and P2 (95% CI: 75.9%–100.0%). Specificity was consistently high, ranging from 90.8% (95% CI: 80.3%–96.2%) for D1 to 100.0% (95% CI: 97.8%–100%) for S2. Accuracy ranged from 95.6% (95% CI: 92.1%–97.6%) for D1 to 99.6% (95% CI: 97.5%–99.9%) for P1 and P2. Type 1b tears were the most common (63.3%), followed by types 4b and 3. The posterior oblique ligament (POL) tears were present in 77.0% of the cohort. 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.