Age and Sex Dependency of Cartilage T2 Relaxation Time Mapping in MRI of Children and Adolescents

Abstract

T2 relaxation times on MRI are sensitive to the configuration of cartilage collagen and continually increase during aging in adults. In children, T2 relaxation times increase as a result of cartilage microstructure changes in early inflammatory arthritis. The purpose of this study was to determine age- and sex-related differences in T2 mapping of the patellar cartilage in children and adolescents during normal skeletal maturation. Ninety-seven subjects (age range, 5-22 years; 51 females and 46 males; mean age, 14.3 and 13.7 years, respectively) without patellofemoral instability or inflammatory arthritis were included. All subjects underwent 1.5-T knee MRI with T2 mapping. The mean T2 relaxation time and thickness of the patellar cartilage were documented for each MRI examination. Skeletal maturation was determined by physeal patency (open; or closed or closing) on MRI. The associations between T2 relaxation times, cartilage thickness, sex, age, and physeal patency were assessed using Wilcoxon rank sum test and least-squares means regression models. T2 relaxation times and thickness of the patellar cartilage significantly decreased (p<0.0001) with increasing chronologic age. T2 relaxation times and cartilage thickness in the open physis group were found to be greater than in the closed or closing physis group (p<0.0001). T2 relaxation times and cartilage thickness were greater in males than in females (p<0.05). In contrast to senescent changes in adults, skeletal maturation in children results in a sequential decrease in T2 relaxation times that are age- and sex-dependent. Similar to cartilage in adults, cartilage in children gets progressively thinner during skeletal maturation.