Age-related changes in cortical and cancellous vertebral bone density in girls: assessment with quantitative CT.

OBJECTIVE: Bone mass increases during growth, but little information is available about the changes in cortical and cancellous bone densities during skeletal development or their relative contributions to age-related increases in bone mass. Accordingly, separate measurements of cancellous and cortical bone density were done at each stage of sexual development in white girls during childhood and adolescence. SUBJECTS AND METHODS: Quantitative CT was used to measure the densities of cortical and cancellous bone of the lumbar spine in 96 healthy white girls 4-20 years old. The relationships among various anthropometric indexes, pubertal status, and corresponding densities of cortical and cancellous bone were then examined.
RESULTS: Cortical bone density increased with age, and values were significantly correlated with the anthropometric indexes of height (r = .61), weight (r = .62), body mass index (r = .61), and muscle volume (r = .58). In contrast, cancellous vertebral bone density increased only during the later stages of puberty. Moreover, cancellous bone density in prepubertal girls was inversely related to age (r = -.27) as well as to both the volume (r = -.20) and the height (r = -.15) of the vertebral body.
CONCLUSION: The results suggest that weight bearing and/or mechanical stresses are important determinants of cortical bone density in the lumbar spine throughout growth, whereas cancellous vertebral bone density is more strongly influenced by hormonal and/or metabolic factors associated with sexual development during late adolescence.