Vertebral cross-sectional growth: A predictor of vertebral wedging in the immature skeleton.

The degree of vertebral wedging, a key structural characteristic of spinal curvatures, has recently been found to be negatively related to vertebral cross-sectional area (CSA). The purpose of this longitudinal study was to examine the relation between vertebral cross-sectional growth and vertebral wedging progression within the immature lumbar spine. Using magnetic resonance imaging (MRI), we analyzed the potential association between increases in lumbar vertebral CSA and changes in L5 vertebral wedging in 27 healthy adolescent girls (ages 9-13 years) twice within a two-year period. Vertebral CSA growth was negatively associated with changes in posteroanterior vertebral wedging (r = -0.61; p = 0.001). Multiple regression analysis showed that this relation was independent of gains in age, height, and weight. When compared to the 14 girls whose vertebral wedging progressed, the 13 subjects whose vertebral wedging decreased had significantly greater vertebral cross-sectional growth (0.39 ± 0.25 vs. 0.75 ± 0.23 cm2; p = 0.001); in contrast, there were no significant differences in increases in age, height, or weight between the two groups. Changes in posteroanterior vertebral wedging and the degree of lumbar lordosis (LL) positively correlated (r = 0.56, p = 0.002)-an association that persisted even after adjusting for gains in age, height, and weight. We concluded that in the immature skeleton, vertebral cross-sectional growth is an important determinant of the plasticity of the vertebral body; regression of L5 vertebral wedging is associated with greater lumbar vertebral cross-sectional growth, while progression is the consequence of lesser cross-sectional growth

Multiple linear regression model relating gains in age, height, weight, and vertebral CSA to changes in vertebral wedging.

<p>Multiple linear regression model relating gains in age, height, weight, and vertebral CSA to changes in vertebral wedging.</p

Age, anthropometric, and MRI measurements of lumbar spine morphology in 27 healthy girls at baseline and follow-up.

<p>Age, anthropometric, and MRI measurements of lumbar spine morphology in 27 healthy girls at baseline and follow-up.</p

Changes in age, anthropometric measures, and lumbar spine morphology of girls with increased and deceased vertebral wedging.

<p>Changes in age, anthropometric measures, and lumbar spine morphology of girls with increased and deceased vertebral wedging.</p

Multiple linear regression model on the effect of changes in vertebral wedging, after adjusting for gains in age, height, and weight, on lumbar lordosis progression.

<p>Multiple linear regression model on the effect of changes in vertebral wedging, after adjusting for gains in age, height, and weight, on lumbar lordosis progression.</p

Boxplot showing differences in vertebral cross-sectional growth between girls with increased (<i>n</i> = 14) and decreased vertebral body wedging (<i>n</i> = 13); <i>p</i> = 0.001.

<p>Boxplot showing differences in vertebral cross-sectional growth between girls with increased (<i>n</i> = 14) and decreased vertebral body wedging (<i>n</i> = 13); <i>p</i> = 0.001.</p

Simple linear regression between changes in vertebral CSA and vertebral wedging (<i>r</i> = -0.611; <i>p</i> = 0.001).

<p>Simple linear regression between changes in vertebral CSA and vertebral wedging (<i>r</i> = -0.611; <i>p</i> = 0.001).</p

Association between vertebral cross-sectional area and lumbar lordosis angle in adolescents

<div><p>Lumbar lordosis (LL) is more prominent in women than in men, but the mechanisms responsible for this discrepancy are poorly defined. A recent study indicates that newborn girls have smaller vertebral cross-sectional area (CSA) when compared to boys—a difference that persists throughout life and is independent of body size. We determined the relations between vertebral cross-sectional area (CSA) and LL angle and whether sex differences in lumbar lordosis are related to sex differences in vertebral CSA. Using multi-planar magnetic resonance imaging (MRI), we measured vertebral cross-sectional area (CSA) and vertebral height of the spine of 40 healthy boys and 40 girls, ages 9–13 years. Measures of the CSA of the lumbar vertebrae significantly differed between sexes (9.38 ± 1.46 vs. 7.93 ± 0.69 in boys and girls, respectively; P < 0.0001), while the degree of LL was significantly greater in girls than in boys (23.7 ± 6.1 vs. 27.6 ± 8.0 in boys and girls, respectively; P = 0.02). When all subjects were analyzed together, values for LL angle were negatively correlated to vertebral CSA (r = -0.47; P < 0.0001); this was also true when boys and girls were analyzed separately. Multivariate regression analysis indicated that vertebral CSA was independently associated with LL, even after accounting for sex, age, height or vertebral height, and weight. Similar negative relations were present when thoracic vertebrae were analyzed (Model P < 0.0001, R² = 0.37, thoracic vertebral CSA slope P < 0.0001), suggesting that deficient vertebral cross-sectional dimensions are not merely the consequence of the anterior lumbar curvature. We conclude that vertebral CSA is negatively associated with LL, and that the greater degree of LL in females could, at least in part, be due to smaller vertebral cross-sectional dimensions. Studies are needed to examine the potential relations between vertebral CSA and spinal conditions known to be associated with increased LL, such as spondylolysis and spondylolisthesis.</p></div

MRI images of the lumbar spine in a 13-year-old girl.

<p>(A) Coned-down sagittal image of the lumbar spine showing the degree of lumbar lordosis measured as the angle between the superior endplate of L1 and the inferior endplate of L5. (B) Axial image outlining the measurement of vertebral CSA at the third lumbar vertebra.</p

Multivariate regression models for the prediction of lumbar lordosis without (A) and with (B) the inclusion of vertebral CSA.

<p>Multivariate regression models for the prediction of lumbar lordosis without (A) and with (B) the inclusion of vertebral CSA.</p