Anterolateral ligament MRI of the knee in ACL injuries: MRI abnormalities association with instability.

Objective: To evaluate anterolateral ligament abnormalities (ALL) at MRI scans and correlate with data from clinical instability tests (Lachman and pivot shift) performed under anesthesia in patients with acute anterior cruciate ligament (ACL) tears. Furthermore, perform multivariate analysis with other variables to isolate the ALL contribution to instability from other abnormalities.

Methods: Retrospective analysis of MRI and instability tests of 95 patients with ACL tears. The ALL was classified as no abnormality, abnormality without discontinuity, and discontinuity. Injuries in other knee ligament structures and menisci were also assessed. Results of instability tests (pivot shift and Lachman) with the patient anesthetized for arthroscopic ACL reconstruction were obtained from the patient database. Statistical analysis was performed using the IBM SPSS 22.

Results: ALL abnormalities and iliotibial band (ITB), lateral (LCL), and medial (MCL) collateral ligament injuries showed a statistically significant correlation with the pivot shift test. The ALL MRI abnormalities were associated with the high-grade pivot shift results (p < 0.0005), with an odds ratio of 55.9 for high degrees of pivot shift in patients with abnormal ALL. The logistic model for all variables analyzed with the results of the pivot shift test demonstrated that the ALL was the only variable with a statistically significant correlation in the model (p < 0.0005).

Conclusion: MRI ALL abnormalities in patients with ACL injuries have a significant association with pivot shift test results in patients under anesthesia. The logistic model for high - grade pivot shift test results demonstrated that ALL abnormalities were the only variable with significant correlation.

Key Points: • Evaluating the anterolateral ligament with MRI in acute anterior cruciate ligament injuries is useful to predict higher grades of pivot shift test in the moment of the arthroscopic reconstruction. • An abnormal anterolateral ligament presented an odds ratio of 55 for high degrees of pivot shift. • ALL MRI abnormalities association with knee instability is independent from other internal knee injuries.