Factors associated with rotational alignment on preoperative magnetic resonance imaging in patients with anterior cruciate ligament injury.
PURPOSE Greater internal tibial rotation on magnetic resonance imaging (MRI) in patients with anterior cruciate ligament (ACL) injury is a risk factor for graft failure after ACL reconstruction. However, the factors influencing rotational alignment on MRI remain unclear. This study aimed to examine the factors associated with tibial rotation on preoperative MRI in patients with ACL injury. METHODS Preoperative MRI images of 214 patients with ACL injuries were retrospectively analyzed to quantify the tibiofemoral rotation angle (TFA). Injuries to the medial collateral ligament, lateral collateral ligament, anterolateral ligament, Kaplan fibers, and meniscal tears were assessed. The lateral and medial posterior tibial slopes were measured. Patients were classified into an internal rotation group (TFA ≥ 4.5°; n = 81) and an external rotation group (TFA < 4.5°; n = 133). Factors associated with increased tibial internal rotation were evaluated using logistic regression analysis. RESULTS The mean TFA was 8.3 ± 2.5° in the internal rotation group and 0.3 ± 3.1° in the external rotation group. Lateral posterior tibial slope was significantly greater in the internal rotation group than in the external rotation group (8.3 ± 3.2° vs. 7.0 ± 2.9°, P < 0.01). Multivariable analysis identified male sex (odds ratio 1.93, P = 0.047) and greater lateral posterior tibial slope (odds ratio 1.20, P < 0.001) as independent factors associated with tibial internal rotation. CONCLUSION In patients with ACL injury, increased tibial internal rotation on preoperative MRI was independently associated with male sex and a greater lateral posterior tibial slope.