Variations in osteoblastic activity with age by the osteoid seam index

Sexual Dimorphism and the Origins of Human Spinal Health

Recent observations indicate that the cross-sectional area (CSA) of vertebral bodies is on average 10% smaller in healthy newborn girls than in newborn boys, a striking difference that increases during infancy and puberty and is greatest by the time of sexual and skeletal maturity. The smaller CSA of female vertebrae is associated with greater spinal flexibility and could represent the human adaptation to fetal load in bipedal posture. Unfortunately, it also imparts a mechanical disadvantage that increases stress within the vertebrae for all physical activities. This review summarizes the potential endocrine, genetic, and environmental determinants of vertebral cross-sectional growth and current knowledge of the association between the small female vertebrae and greater risk for a broad array of spinal conditions across the lifespan.

Timing of peak bone mass: discrepancies between CT and DXA

CONTEXT

The time of life in which peak bone mass in the axial skeleton is attained has been the subject of considerable controversy, with estimates ranging from the time of sexual and skeletal maturity to the fifth decade of life.

OBJECTIVE

The objective was to examine whether dual energy x-ray absorptiometry (DXA) and computed tomography (CT) values for bone mass and bone density (BD) in the axial skeleton increase after sexual and skeletal maturity.

DESIGN/PARTICIPANTS

Measurements of vertebral bone mineral density and bone mineral content (BMC) by DXA and vertebral BD and BMC by CT were obtained in 50 sexually and skeletally mature white females at baseline and 3 yr later. CT BMC values were calculated through analysis of vertebral volume in relation to density (BMC = vertebral volume x BD).

RESULTS

Although neither CT BD nor BMC measures changed with time, DXA bone mineral density and BMC values were significantly higher at follow-up (P < 0.0001). Despite strong correlations between DXA and CT bone measures, DXA yielded greater changes in bone values in 47 of 50 subjects.

CONCLUSIONS

Bone acquisition in the lumbar spine as measured by CT reaches its peak by sexual and skeletal maturity. In contrast, bone values by DXA continue to increase after puberty and cessation of longitudinal growth. Increases in DXA measures are likely a reflection of inhomogeneous changes in soft tissues around the spine or of disproportionate increases in the posterior elements of the vertebrae rather than of changes within the vertebral body.

Peak trabecular vertebral density: a comparison of adolescent and adult females

To determine when spinal bone density reaches its peak, the trabecular vertebral density was assessed, via quantitative computed tomography, among females from two age groups: (1) adolescents (aged 14-19 years; N = 24); and (2) young adults (aged 25-35 years; n =24). The adolescent girls had a higher mean trabecular vertebral density (P less than 0.01), suggesting that spinal density reaches its peak around the time of cessation of longitudinal growth and epiphyseal closure.

The costochondral junction during later stages of intrauterine life, and abnormal growth patterns found in association with perinatal death

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