Purpose

In acute supposedly isolated anterior cruciate ligament (ACL) injury, concomitant damage to the medial soft tissues may occur. The purpose of this study was to investigate the incidence, injury patterns and risk factors of medial collateral ligament complex (MCL) injuries and ramp lesions in patients with acute ‘isolated’ ACL ruptures.

Methods

Patients who underwent ACL reconstruction for MRI and arthroscopically confirmed acute complete ‘isolated’ ACL rupture between September 2015 and April 2019 were retrospectively included in this study. Patients’ characteristics, clinical findings, concomitant injuries on MRI and tibial slope were evaluated. Preoperative MRIs were evaluated for ramp lesions, and the grade and location of injuries to the superficial MCL (sMCL), deep MCL (dMCL), the posterior oblique ligament (POL). All patients were examined under anaesthesia and isolated ACL lesions confirmed. Binomial logistic regression was used to analyse risk factors for exhibiting a dMCL injury or ramp lesion.

Results

There were 100 patients (80 male, 20 female) with mean age 22.3 ± 4.9 years. 16% had ramp lesions. The overall incidence of concomitant MCL complex injuries was 67%: sMCL in 62%, dMCL in 31% (93.4% meniscofemoral) and POL in 11% in various combinations. A dMCL injury was highly associated with MRI grade II sMCL injuries and bone edema at the medial femoral condyle (MFC) adjacent to the dMCL attachment site (both, p<0.01) but also occurred in isolation (4%). Meniscus ramp lesions were associated with injuries to the sMCL (p<0.01) and dMCL (p<0.01), as well as bone edema in the posterior medial tibia plateau (MTP) (p<0.05). Logistic regression analysis identified younger age (OR 1.2, p<0.05), simultaneous sMCL injury (OR 6.75, p<0.01) and the presence of bone edema at the MFC adjacent to the dMCL attachment site (OR 5.54, p<0.01) as predictive factors for a dMCL injury. A dMCL injury, a flatter lateral tibial slope and the identification of a ramp lesion on MRI increases the likelihood of finding a ramp lesion at surgery.

Conclusion

The incidence of MCL injury on MRI in clinically isolated ACL is high. dMCL lesions were associated with ramp lesions, MFC bone edema at the dMCL attachment, and sMCL injury. Bone edema in the MFC, posterior MTP, sMCL, and dMCL lesions and are highly associated with ramp lesions. The high correlation between dMCL and ramp lesions suggests that some ACLs are injured involving tibial external rotation stretching fibres of the dMCL and meniscal ramp and causing anteromedial rotatory instability, which, if overlooked, leads to ACL graft failure. This knowledge facilitates precise diagnosis of instability patterns in patients with ACL tears.