Abstract Purpose Residual anterolateral rotatory instability after anterior cruciate ligament reconstruction (ACLR) remains incompletely explained by graft‐related parameters alone. The purpose of this study was to define and validate the Tibial Slope–Meniscal Coupling Index (TMSI), a quantitative magnetic resonance imaging (MRI) parameter integrating tibial slope and meniscal geometry, as a predictor of residual anterolateral rotatory instability after ACLR. Methods A retrospective cohort of 140 patients ≥12 months after primary ACLR underwent standardized 1.5‐ or 3‐T MRI evaluation. Medial and lateral posterior tibial slope (PTS) and posterior horn displacement (PHd) of the lateral meniscus were measured to calculate the TMSI = (mean PTS × PHd)/tibial width. Clinical outcomes included pivot‐shift grade, KT‐1000 side‐to‐side difference and patient‐reported outcome scores. Receiver operating characteristic (ROC) analysis and multivariable logistic regression assessed predictive performance. Results Patients with residual pivot ( n = 59, 42%) demonstrated higher PTS, greater PHd and significantly higher TMSI (0.7 ± 0.1 vs. 0.4 ± 0.1; p 0.6 predicted residual pivot with an AUC of 0.8 (95% confidence interval CI, 0.8–0.9), sensitivity 86% and specificity 82%. In multivariable analysis, TMSI was the only variable that remained independently associated with residual pivot instability (odds ratio OR, 5.6; p < 0.001). Interobserver intraclass correlation coefficient was 0.92. Conclusion Clinically, the TMSI may assist in identifying patients at increased risk of persistent rotational instability and support decision‐making regarding adjunctive stabilization procedures. Level of Evidence Level III.
Rivarola et al. (Thu,) studied this question.