Abnormal tibiofemoral kinematics following ACL reconstruction are associated with early cartilage matrix degeneration measured by MRI T1rho.

PURPOSE: Altered kinematics following ACL-reconstruction may be a cause of post-traumatic osteoarthritis. T(1ρ) MRI is a technique that detects early cartilage matrix degeneration. Our study aimed to evaluate kinematics following ACL-reconstruction, cartilage health (using T(1ρ) MRI), and assess whether altered kinematics following ACL-reconstruction are associated with early cartilage degeneration.

METHODS: Eleven patients (average age: 33 ± 9 years) underwent 3T MRI 18 ± 5 months following ACL-reconstruction. Images were obtained at extension and 30° flexion under simulated loading (125 N). Tibial rotation (TR) and anterior tibial translation (ATT) between flexion and extension, and T(1ρ) relaxation times of the knee cartilage were analyzed. Cartilage was divided into five compartments: medial and lateral femoral condyles (MFC/LFC), medial and lateral tibias (MT/LT), and patella. A sub-analysis of the femoral weight-bearing (wb) regions was also performed. Patients were categorized as having "abnormal" or "restored" ATT and TR, and T(1ρ) percentage increase was compared between these two groups of patients.

RESULTS: As a group, there were no significant differences between ACL-reconstructed and contralateral knee kinematics, however, there were individual variations. T(1ρ) relaxation times of the MFC and MFC-wb region were elevated (p ≤ 0.05) in the ACL-reconstructed knees compared to the uninjured contralateral knees. There were increases (p ≤ 0.05) in the MFC-wb, MT, patella and overall average cartilage T(1ρ) values of the "abnormal" ATT group compared to "restored" ATT group. The percentage increase in the T(1ρ) relaxation time in the MFC-wb cartilage approached significance (p=0.08) in the "abnormal" versus "restored" TR patients.

CONCLUSIONS: Abnormal kinematics following ACL-reconstruction appear to lead to cartilage degeneration, particularly in the medial compartment.