Assessment of tissue repair in full thickness chondral defects in the rabbit using magnetic resonance imaging transverse relaxation measurements.

The purpose of this study was to determine if the noninvasive and nondestructive technique of magnetic resonance imaging could be used to quantify the amount of repair tissue that fills surgically-induced chondral defects in the rabbit. Sixteen 4-mm diameter full-thickness chondral defects were created. A photopolymerizable hydrogel was used to seal the defects as a treatment modality. At 5 weeks, the animals were sacrificed and the distal femur was subjected to MRI analyses at high field (9.4 T). The transverse relaxation time (T(2)) in each defect was measured. Histology and histomorphometric analysis were used to quantify the amount of repair tissue that filled each defect. The relationship between T(2) and percent tissue fill was found to fit well to a negatively sloped, linear model. The linear (Pearson's product-moment) correlation coefficient was found to be r = -0.82 and the associated coefficient of determination was r(2) = 0.67. This correlation suggests that the MRI parameter T(2) can be used to track changes in the amount of repair tissue that fills cartilage defects. This would be especially useful in in vivo cartilage tissue engineering studies that attempt to determine optimal biomaterials for scaffold design.