Volumetric bone mineral density — a potential role in paediatrics

Abstract

The use of areal bone mineral density (aBMD) in paediatric populations has aroused some concern, as it fails to take the age‐related increase in bone thickness into account. We have developed a measure of true bone density, volumetric bone mineral density (vBMD), which is independent of age and height. In order to examine the relationship between growth parameters, aBMD and vBMD, we studied patients with phenylketonuria (PKU, n = 40), chronic renal failure (CRF, n = 27) and chronic asthma (n = 19). aBMD of the femoral neck and the mid‐femoral shaft was measured using dual energy X‐ray absorptiometry (DXA), vBMD was calculated on the basis of values of bone mineral content and bone dimension provided by DXA, with the assumption that both sites are cylinders. aBMD and vBMD were then compared with the normal reference, expressed as a standard deviation score (SDS). aBMD and vBMD were normal in the femoral neck region of the PKU group, but aBMD, either standardized for age or for height, was low in the femoral shaft region (p < 0.01). In the CRF group, profound growth retardation was seen (mean height SDS, −3.2) and aBMD and vBMD were both low in the femoral shaft region but not in the femoral neck. In the asthma group, aBMD for age was low at both sites, but vBMD did not differ from that seen in normal individuals. We conclude that the true vBMD provides a different interpretation of bone density compared with aBMD and requires further evaluation in paediatrics because of its age and height independence.

Bone mineral density in adolescent females with recently diagnosed anorexia nervosa

“…The purported advantage of volumetric BMD in children is its lack of variation with age (Cowell et al, 1995;Lu et al, 1996). However, it requires certain assumptions about the geometry of the region evaluated.…”

Daily Physical Education in the School Curriculum in Prepubertal Girls during 1 Year is Followed by an Increase in Bone Mineral Accrual and Bone Width—Data from the Prospective Controlled Malmö Pediatric Osteoporosis Prevention Study

“…Volumetric bone mineral density (vBMD, g/cm 3 ) was calculated for L3 using the algorithm introduced by Carter (40), and for the FN using the formula vBMD = BMC/estimated FN volume (π x r 2 x FN length) where r = FN mid-diameter/2, assuming the FN to be cylindrical (41)(42)(43). During the measurement of the lumbar spine, the child was supine, and the physiological lumbar lordosis was flattened by elevation of the knees.…”

Bone Density and Metabolism in Children and Adolescents With Moderate to Severe Cerebral Palsy

“…Areal bone density may be diminished relative to age-matched normal subjects because of a true decrease in volumetric density or because of differences in the 3-dimensional structure of the bone. 40,41 A diminished outer diameter and thinning of the cortex both will result in diminished areal BMD as measured with DXA, regardless of whether true volumetric density is diminished. The diameter of a cylindrical bone and the thickness of the cortex, however, are important mechanical parameters that have a significant impact on the ability of a bone to withstand loads without fracture.…”