Relative contribution of vertebral body and posterior arch in female and male lumbar spine peak bone mass.

Peak bone mass (PBM) is an important reference value in the diagnosis of osteoporosis. It is usually established by determining the areal bone mineral density (BMD in g/cm2) for a given site of the skeleton in young healthy adults. This measurement takes into account both the thickness and the integrated mineral density of the bone scanned. It should therefore be a major determinant of the resistance to mechanical stress. However, in lumbar spine the mean BMD as determined by dual-energy either isotopic or X-ray (DXA) absorptiometry in antero-posterior (ap) view was repeatedly found not to be different between male and female young healthy adults despite the greater volume of lumbar vertebral bodies in males. A greater contribution of the posterior vertebral arch to areal BMD-ap in females than in males could account for such an apparent discrepancy. In order to clarify this issue we have determined in 65 (32 male and 33 female) young healthy adults aged 20-35 years the relative contribution of the vertebral body (VB) and posterior vertebral arch (VA) to BMD and bone mineral content (BMC) of L2-3 measured by both antero-posterior and lateral (lat) scanning using DXA. In young healthy adults mean BMC in antero-posterior view was found not to be significantly different from the total BMC determined by lateral scanning including both VB and VA. This allowed us then to calculate the VA BMC by substracting VB BMC-lat from BMC-ap.(ABSTRACT TRUNCATED AT 250 WORDS)