KSSTA - 2026-04-16 - Journal Article
The Tibial Slope-Meniscal Coupling Index (TMSI): A novel geometric MRI parameter predicting rotational stability after ACL reconstruction.
Rivarola H, Collazo C, Palanconi M, Meninato M, Endara Urresta F, Peñaherrera-Carrillo C, Barros Castro A, Rivarola B
Topics
Key Takeaway
A novel MRI index combining tibial slope and lateral meniscal posterior horn displacement (TMSI >0.6) predicted residual pivot-shift instability after ACLR with AUC 0.80, sensitivity 86%, and specificity 82%.
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Summary
This study asked whether a composite MRI parameter—TMSI = (mean posterior tibial slope × lateral meniscal posterior horn displacement) / tibial width—predicts residual anterolateral rotatory instability after primary ACLR. In 140 patients, 59 (42%) had residual pivot-shift; this group had significantly higher TMSI (0.7 ± 0.1 vs. 0.4 ± 0.1, p<0.001). On multivariable logistic regression, TMSI was the only independent predictor of residual pivot (OR 5.6, p<0.001), with excellent interobserver reliability (ICC 0.92).
Key Limitation
The retrospective design cannot confirm that TMSI-guided surgical decision-making (e.g., adding LET) actually reduces residual instability rates, as no intervention arm was tested.
Original 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 < 0.001). A TMSI > 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.