Evaluation of cartilage repair in the distal femur after autologous chondrocyte transplantation using T2 relaxation time and dGEMRIC

Summary Objectives To investigate the potential of combining T2 relaxation time and delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) measurements after autologous chondrocyte transplantation (ACT). Materials and methods T2 and dGEMRIC maps were measured in the sagittal and coronal directions in 12 patients 10–15 months after ACT surgery. Grafts were assessed for bulk full thickness, superficial and deep tissue T2 and dGEMRIC values, and were compared to control cartilage. Results All ACT grafts showed filling of the repair area to the level of or above the articular surface. Matrix of the grafts lacked the classical laminar structure and appeared more heterogenous on T2 maps than control cartilage. As compared to control cartilage, ACT grafts showed significantly longer T2 values for bulk tissue as well as for the superficial 50% and deep 50% of tissue except for superficial cartilage in the coronal direction. dGEMRIC assessment in the sagittal and coronal directions did not show a significant difference between bulk, superficial or deep tissue as compared to the control cartilage. Superficial and deep ACT tissue did not differ statistically in terms of their T2 or dGEMRIC values. Conclusions These preliminary results suggest that, according to T2 measurements, ACT repair tissue at 10–15 months differs from normal cartilage and probably lacks the preferential collagen arrangement of normal cartilage, while according to dGEMRIC a varying degree of proteoglycan replenishment takes place. Combining these two quantitative magnetic resonance imaging techniques enables a more comprehensive characterization of cartilage repair than before.