The 'functional muscle-cartilage unit': a reasonable approach to describe a putative relationship between muscle force and longitudinal growth at the forearm in children and adolescents?

BACKGROUND: Several reports give evidence that the perichondral ossificiation of bone tubes (modeling) strongly depends on muscular forces in children and adolescents. The present analyses intend to investigate the hypothesis that muscular forces also partly determine enchondral ossification and, therefore, longitudinal growth of bone tubes. SUBJECTS AND METHODS: Analyses were based on a single cross-sectional investigation with peripheral quantitative computed tomography in 296 individuals (age 5-19 years) participating in the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study. RESULTS: Forearm length (FL) was correlated with body height in gender-related subgroups of prepubertal and pubertal individuals (rs between 0.76 and 0.86). Cross-sectional muscle area (MA) increased faster than FL and faster than cross-sectional bone area (BA) close to the distal growth plate in puberty. Close to the growth plate, longitudinal growth was faster than perichondral ossification in females. The ratio MA/BA (surrogate of pressure on the distal growth plate) was correlated with FL in prepubertal boys (r = -0.249, p = 0.043) and pubertal individuals (r = 0.153, p = 0.051). CONCLUSIONS: Results support the hypothesis that longitudinal growth precedes modeling at the distal forearm. Confounding variables such as puberty may modify the relationship between muscle forces and longitudinal growth at the forearm in boys.