Analysis of the articular cartilage T_1ρ and T₂ relaxation times changes after ACL reconstruction in injured and contralateral knees and relationships with bone shape.

Abstract

The objectives of this study were twofold: (1) to evaluate the longitudinal change in cartilage T_1ρ and T₂ 6- and 12-months after ACL reconstruction (ACLR) in both reconstructed and intact contralateral knees with the aim of validating the role of the contralateral knee as an internal control in longitudinal studies; (2) to explore relationships between bone shape at the time of injury and the progression of T_1ρ and T₂ over 12-months after ACLR. T_1ρ and T₂ cartilage relaxation times and 3D MRI-based statistical shape modeling (SSM) of tibia and femur were computed for both knees of forty ACL-injured patients and 15 healthy controls. ACL subjects were scanned 8.4 ± 6.4 weeks after injury (2.4 ± 3.7 weeks prior to ACLR), 6- and 12-months after ACLR. Longitudinal changes in T_1ρ and T₂ values were assessed using linear mixed model, and partial correlation coefficients were calculated between bone shape and longitudinal changes in T_1ρ and T₂ values. Significant longitudinal increases in T_1ρ and T₂ values were observed in reconstructed and contralateral knees 6-months after ACLR. Tibial bone shape features, associated with the medial plateau height and width, were observed to be correlated with cartilage T_1ρ and T₂ progression in reconstructed knees. Our results suggest that caution should be used in considering contralateral knee as internal controls in longitudinal ACL studies and 3D MRI-based-SSM might serve as an imaging biomarker for the early stratification of patients at risk for developing post-traumatic accelerated cartilage degeneration and potentially osteoarthritis after ACL tear. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:707-717, 2017.