Sex differences in bone mass and size are thought to contribute to the greater
incidence of vertebral fractures in women. While these sex differences are widely
recognized, the relative contributions of bone mass, bone density, and bone size to the
differences in vertebral strength and fracture risk between men and women have not
been fully delineated. Furthermore, it is unknown whether the roles of each of these
factors in determining vertebral strength change differently with age in men and
women. We studied the bone content, density and geometry as well as vertebral
loading and the factor of risk of the L3 vertebra in a sample of prepubertal males and
females. Our first aim was to assess differences in vertebral bone dimensions, bone
density, vertebral loading patterns and fracture risk, as measured by the factor of risk,
in prepubertal children. Our second aim was to determine whether pre-pubertal
growth affects the geometry and density of L3 differently in boys and girls. We
measured vertebral dimensions, cross-sectional area and volumetric BMD of the third
lumbar vertebral body in 93 prepubertal children (54 boys and 39 girls), using dual-energy
X-ray absorptiometry scans obtained in the posterior-anterior and lateral
projections. We also employed basic biomechanics to estimate vertebral loading
during upright standing and forward bending. Bone strength and loading data were
used to assess sex differences in the factor of risk in prepubertal children. Twenty
children (11 boys and 9 girls) were assessed at baseline and seven months later to
examine the effects of growth on bone size and vBMD. At baseline, boys and girls
were similar for age, height, weight and calcium intake. L3 width and depth were
6.7% and 5.8% greater in boys than girls, respectively (P<0.001 and P=0.01,
respectively). In contrast, vertebral height was 3.5% greater in girls than boys (P=
0.04). While vertebral loading was similar between sexes, stresses on the spine were
12.2% lower in boys during upright standing and 12.0% lower in boys during forward
bending at both 50° and 90°, as compared to girls (P<0.001, P<0.01 and P<0.01,
respectively). The factor of risk was similar between boys and girls under each
loading condition. During growth, changes in vertebral size and density were not
different between boys and girls. Our results indicate that even prior to puberty, sex
differences in vertebral size contribute to differences in vertebral stress during
standing and forward bending. Furthermore, before the onset of puberty, growth does
not result in disparate changes between sexes. / Graduation date: 2004
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28914 |
| Date | 09 March 2004 |
| Creators | Fuller, Arwen A. |
| Contributors | Snow, Christine M. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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