DIFFERENTIAL EFFECT OF GENDER ON THE SIZES OF THE BONES IN THE AXIAL AND APPENDICULAR SKELETONS

Recent observations suggest that throughout life the size of the verte bral bodies in females is smaller than that in males even after accoun ting for differences in body size. To confirm these reports and to det ermine whether similar differences exist in the appendicular skeleton, detailed measurements of the sizes of the vertebrae and the femur wer e obtained using computed tomography in 30 pairs of prepubertal bays a nd girls matched for age, height, and weight. Anthropometric parameter s as well as gender influenced the cross-sectional area of the vertebr ae. Heavier children had greater vertebral cross-sectional area than s lender children regardless of gender, and the vertebral bodies were fo und to be significantly smaller in girls than in matched boys (similar to 11%), both using Student's t test (P < 0.0001) and its multivariat e analog, the Hotelling's T-2 test (P < 0.0001). In contrast to these findings in the axial skeleton, gender status did not influence the si ze of the bones in the appendicular skeleton, and neither the cross-se ctional area (3.28 +/- 0.84 vs. 3.10 +/- 0.56 cm(2)) nor the cortical bone area (1.80 +/- 0.37 us. 1.85 +/- 0.36 cm(2)) at the midshaft of t he femur differed between boys and girls. These values, however, corre lated strongly with all anthropometric indexes, and multiple regressio n analyses indicated that both measurements were primarily related to weight. The results suggest that although increases in mechanical load ing associated with growth are the main determinant of the cross-secti onal properties of the appendicular skeleton in children, factors othe r than body mass and related to gender have a significant role in the regulation of the sizes of the bones in the axial skeleton.