Comparative assessment of bone mineral measurements obtained by use of dual-energy x-ray absorptiometry, peripheral quantitative computed tomography, and chemical-physical analyses in femurs of juvenile and adult dogs.

Abstract

To compare bone mineral measurements obtained by use of dual-energy x-ray absorptiometry (DEXA), peripheral quantitative computed tomography (pQCT), and chemical-physical analyses and determine effects of age and femur size on values obtained for the various techniques. Femurs obtained from 15 juvenile and 15 adult large-breed dogs. n each femur, 7 regions of interest were examined by use of DEXA to measure the bone mineral content (BMC) and bone mineral density (BMD), and 5 were examined by use of pQCT to measure BMD. Among these, 1 region was examined by both noninvasive methods and an invasive method. Volume of the femur was determined by water displacement. Volumetric bone density (VBD) was calculated. Calcium (Ca), phosphorus (P), total Ca, and total P contents were determined. DEXA- and pQCT-derived results revealed that all values increased with age in juvenile dogs. In adults, VBD and pQCT-derived BMD decreased significantly and DEXA-derived BMD increased with increasing femur length. The pQCT-derived BMD correlated well with VBD and Ca content, whereas DEXA-derived BMC was strongly correlated with Ca content. In juveniles, values correlated regardless of the technique used, whereas in adult dogs, DEXA-derived BMD did not correlate with pQCT-derived BMD, Ca concentration, or VBD unless data were adjusted on the basis of femur length. DEXA-derived BMD adjusted for femur length yields approximately the same percentage variability in VBD as for pQCT-derived BMD. However, pQCT-derived BMD is still more sensitive for determining variability BMD in Ca concentration, compared with DEXA-derived BMD adjusted for femur length.