Tear Location of Superficial Medial Collateral Ligament Tears: Validation of a Magnetic Resonance Imaging-Based Classification System.

Abstract

BACKGROUND The superficial medial collateral ligament (sMCL) is commonly injured, with treatment varying based on associated injuries, tear grade, and location. However, the prevalence of different tear locations and the predictors of tear types have not been studied. PURPOSE To evaluate the interrater and intrarater reliability for a magnetic resonance imaging (MRI)-based sMCL classification system and assess the incidence of different tear types with its predictors. STUDY DESIGN Cohort study; Level of evidence, 3. METHODS A retrospective search in a single institution's MRI database identified patients with acute, complete sMCL tears (≤30 days between injury and MRI) between January 2018 and December 2022. Exclusion criteria included previous ligamentous knee trauma/surgery, >30 days between injury and MRI, and partial sMCL tears. MRI scans were assessed by 3 independent raters using a predefined sMCL tear location system: type I (proximal 25%), type Ib (proximal femoral bony avulsion), type II (midsubstance, 25%-75%), type III (distal 25%), type IIIb (distal tibial bony avulsion), and type IIIs (Stener-like lesion). The intraclass correlation coefficient (ICC) was used to assess interobserver and intraobserver reliability for continuous data, whereas Fleiss and Cohen kappas were used for categorical data. Univariate and multivariate logistic regression assessed predictors of tear location. RESULTS The study included 239 patients (49% female; mean age, 38 ± 14 years; range, 13-75 years). The MRI-based sMCL classification system showed excellent interobserver reliability (0.960; 95% CI, 0.951-0.969) and excellent intraobserver reliability (evaluator 1: 0.969 (95% CI, 0.960-0.976); evaluator 2: 0.952 (95% CI, 0.915-0.973)). Type I sMCL tears were most common (65.4%), followed by type III (14.6%), type II (14.5%), type Ib (3.4%), and type IIIs (1.7%). Binary logistic regression identified medial meniscal tears (odds ratio [OR] 7.987; P = .034) and younger age (OR 0.916; P = .0001) as predictors for distal sMCL tears and older age as a predictor for proximal tears (OR 1.048; P = .001). CONCLUSION This study validates an MRI-based sMCL classification system for locating high-grade sMCL tears with excellent reliability. Proximal tears were the most common (69%) and were significantly more prevalent with increasing age, whereas distal tears were more commonly seen with younger age and midbody medial meniscal tears. These findings may guide individualized treatment strategies and refine diagnostic protocols for patients with acute sMCL tears.