The presence of a Segond fracture in ACL-injured patients is associated with increased internal tibial rotation on preoperative MRIs

Background Segond fracture is considered a component of the anterolateral complex (ALC) injury, yet the underlying cause and clinical outcomes of this bony avulsion remain subjects of debate. Additionally, MRI measurements of altered tibiofemoral position in anterior cruciate ligament (ACL)-injured patients with a Segond fracture have not been reported. The purpose of this study is to measure the rotational tibiofemoral position on MRI in ACL-injured patients with a Segond fracture. Methods A total of 44 patients with a primary ACL injury and a concomitant Segond fracture were included in the Segond fracture group, with the time from injury to MRI within 3 months. Avulsion was confirmed via preoperative computed tomography (CT) scans. The control group comprised 44 matched patients with primary ACL injury and an MRI-determined ALC injury but without a Segond fracture, also with the time from injury to MRI within 3 months. The MRI-determined ALC injury included injuries to the anterolateral ligament, Kaplan fibers, and anterolateral joint capsule, as identified based on previous studies. Sex, age, and BMI were matched between the two groups using propensity score matching (PSM). Arthroscopic findings, concomitant collateral ligament injuries, and preoperative MRI measurements were compared between the two groups. Results The Segond fracture group demonstrated a higher frequency of concomitant patellar and femoral trochlear injuries (p = 0.0110) and lateral collateral ligament injuries (p = 0.0121) compared to the control group. Additionally, significantly increased internal rotational tibial subluxation (IRTS) (p = 0.0095) and axial internal tibial rotation (ITR.sub.a) (p = 0.0306) were observed in the Segond fracture group. A strong positive correlation was found between IRTS and ITR.sub.a (r.sub.p = 0.8201), indicating that these two tibial rotation measurement methods were correlated. No significant differences were observed in the measurements of anteroposterior tibiofemoral position and posterior tibial slope (PTS) between the two groups. Conclusion The presence of a Segond fracture was associated with significantly increased internal tibial rotation measured on MRIs, suggesting that this bony avulsion may represent a more severe form of ALC injury in ACL-injured patients and should be managed with caution. Keywords: Anterior cruciate ligament, Segond fracture, Anterolateral complex, Internal rotational tibial subluxation, Internal rotation, Tibiofemor