Spatial variation of T2 relaxation times of patellar cartilage and physeal patency: an in vivo study in children and young adults.

Abstract

The purpose of this study was to determine whether the T2 spatial variation of patellar cartilage is different between children and young adults with open and closed physes. Fifty-two subjects in two age ranges were included; 13 girls and 13 boys from 5 to 11 years old, and 13 female young adults and 13 male young adults from 17 to 22 years old. T2 maps of patellar cartilage were generated at 1.5 T. Physeal patency and mean T2 relaxation times as a function of normalized distance (T2 spatial variation) were evaluated in each group and sex. All the subjects from 5 to 11 years old had open physes and all the subjects from 17 to 22 years old had closed physes. Mean T2 relaxation times of patellar cartilage in the open physis group were significantly longer than in the closed physis group throughout all normalized distances across patellar cartilage (p<0.05). There were significant differences in T2 spatial variation between the two groups (p<0.05). The open physis group had longer mean T2 relaxation times at the osteochondral area and articular cartilage than in the central portion. The closed physis group had shorter mean T2 relaxation times in the osteochondral area, with a gradual increase to longer values at the articular surface. Differences in T2 spatial variation were greatest at the osteochondral junction (p<0.05). There was no statistically significant sex difference in T2 spatial variation in either group. T2 spatial variation is different between skeletally immature and mature patellar cartilage. This difference is most prominent at the osteochondral junction and likely relates to the presence or absence of ongoing endochondral ossification.