Longitudinal analysis of tibiofemoral cartilage contact area and position in ACL reconstructed patients

Patients who have suffered ACL injury are more likely to develop early onset post‐traumatic osteoarthritis despite reconstruction. The purpose of our study was to evaluate the longitudinal changes in the tibiofemoral cartilage contact area size and location after ACL injury and reconstruction. Thirty‐one patients with isolated unilateral ACL injury were followed with T2 weighted Fast Spin Echo, T1ρ and T2 MRI at baseline prior to reconstruction, and 6 months, 1 year, and 2 years after surgery. Areas were delineated in FSE images with an in‐house Matlab program using a spline‐based semi‐automated segmentation algorithm. Tibiofemoral contact area and centroid position along the anterior‐posterior axis were calculated along with T1ρ and T2 relaxation times on both the injured and non‐injured knees. At baseline, the injured knees had significantly smaller and more posteriorly positioned contact areas on the medial tibial surface compared to corresponding healthy knees. These differences persisted 6 months after reconstruction. Moreover, subjects with more anterior medial centroid positions at 6 months had elevated T1ρ and T2 measures in the posterior medial tibial plateau at 1 year. Changes in contact area and centroid position after ACL injury and reconstruction may characterize some of the mechanical factors contributing to post‐traumatic osteoarthritis.