Comparison between spinal and radial bone mineral density in children measured by X-ray absorptiometry

Several studies have analyzed the correlation between axial bone mineral density (BMD) measured by dual X-ray absorptiometry (DXA) and growth parameters. However, little is known about the growth-related changes in appendicular BMD measured by this technique. We used DXA to measure BMD in the lumbar spine (L1-L4) and distal radius in 121 normal growing children (69 boys, 52 girls), aged 3 to 18 yr. Both lumbar and radius BMD showed a steady increase with age and a steeper increment during puberty. There was a good correlation between spinal and radial BMD (r = 0.83; p < 0.001) and both were highly correlated with growth parameters; their respective correlation coefficients did not differ significantly for chronological age (r = 0.70 vs 0.80), weight (r = 0.77 vs 0.76), height (r = 0.73 vs 0.79), body surface (r = 0.78 vs 0.80), body mass index (r = 0.54 vs 0.49) and bone age (r = 0.77 vs 0.79). By multiple regression analysis the best predictors for spinal BMD were bone age, pubertal stage and weight, while for radial BMD the best predictors were chronological age and weight. We have shown that the measurement of BMD by DXA at distal radius, an easily accessible bone, has a correlation with growth parameters as good as lumbar spine BMD measurements in children.