We provide new evidence that girls and boys with adolescent idiopathic scoliosis have significantly smaller vertebral cross-sectional area and taller intervertebral disc heights - two major structural determinants that influence trunk flexibility. With appropriate validation, these findings may have implications for the identification of children at the highest risk for developing scoliosis.

Background The pediatric spina bifida population suffers from decreased mobility and recurrent fractures. This study aimed to develop a method for quantifying bone mass along the entire tibia in youth with spina bifida. This will provide information about all potential sites of bone deficiencies. Methods Computed tomography images of the tibia for 257 children (n=80 ambulatory spina bifida, n=10 non-ambulatory spina bifida, n=167 typically developing) were analyzed. Bone area was calculated at regular intervals along the entire tibia length and then weighted by calibrated pixel intensity for density weighted bone area. Integrals of density weighted bone area were used to quantify bone mass in the proximal and distal epiphyses and diaphysis. Group differences were evaluated using analysis of variance. Findings Non-ambulatory children suffer from decreased bone mass in the diaphysis and proximal and distal epiphyses compared to ambulatory and control children (P≤0.001). Ambulatory children with spina bifida showed statistically insignificant differences in bone mass in comparison to typically developing children at these sites (P>0.5). Interpretation This method provides insight into tibial bone mass distribution in the pediatric spina bifida population by incorporating information along the whole length of the bone, thereby providing more information than dual-energy x-ray absorptiometry and peripheral quantitative computed tomography. This method can be applied to any population to assess bone mass distribution across the length of any long bone.

Objective To examine whether the sex-related differences in vertebral cross-sectional area (CSA) found in children and at the timing of peak bone mass – a major determinant of osteoporosis and future fracture risk – are also present at birth. Study design Vertebral CSA, vertebral height, and intervertebral disc height were measured using magnetic resonance imaging (MRI) in 70 healthy full-term newborns (35 male and 35 female). Additionally, measures of the length and CSA of the humerus, musculature, and adiposity were obtained. Results Weight, body length, and head and waist circumferences did not significantly differ between sexes (all P’s ≥ 0.06). Compared with newborn boys, girls had significantly smaller vertebral cross-sectional dimensions; 1.47 ± 0.11 vs. 1.31 ± 0.12; P < 0.0001. Multiple linear regression analysis indicated that sex was a predictor of vertebral CSA independent of gestational age, birth weight, and body length. In contrast, sexes were monomorphic with regard to vertebral height, intervertebral disc height, and spinal length (all P’s ≥ 0.11). There were also no sex differences in the length or cross-sectional dimensions of the humerus or in measures of musculature and adiposity (all P’s ≥ 0.10). Conclusions Factors related to sex influence fetal development of the axial skeleton. The smaller vertebral CSA in females is associated with greater flexibility of the spine that could represent the human adaptation to fetal load. Unfortunately, it also imparts a mechanical disadvantage that increases stress within the vertebrae for all physical activities and the susceptibility for fragility fractures later in life.