Knochendichtemessungen an Oberschenkelknochen juveniler und adulter Hunde mittels Dual Enegy X-Ray Absorptiometry (DXA) und peripherer Quantitativer Computertomographie (pQCT) im Vergleich mit chemischer und physikalischer Analyse.
Dissertation, Vet. Med. Univ. Wien, pp. 69.
Objectives: To validate bone mineral measurements by Dual-Energy X-Ray Absorptiometry (DXA) and peripheral Quantitative Computed Tomography (pQCT) in comparison with results of chemical/physical analyses and to determine the effects of age and femur size on BMM relative to the technique used.
Material and Methods: Paired femurs of 15 juvenile (mean SD = 21.0 7.7 weeks) and 15 adult large dogs (mean SD = 8.3 4.2 years) were examined. Seven regions were examined by DXA to measure the bone mineral content (BMC, g) and bone mineral density (BMD, g/cm²) and five by pQCT to measure BMD (mg/cm³). A defined region of the left femur was additionally examined for calcium concentration by atomic absorption spectro-photometry and for phosphorus concentration by the vandate-molybdate method. The femur's volume was determined by water displacement and the volumetric bone density (VBD, g/ml) was calculated.
Results: In juveniles, bone mineral density and bone mineral content increased with age (P;0.05), whereas in adults, these values tendentiously decreased with age. Similarly, these values increased with increasing femoral length in juveniles, whereas in adults, BMD obtained by pQCT (r = -0.588 to 0.715) and VBD (r = -0.615) significantly decreased, the calcium concentration (r = -0.414) tendentiously decreased, but BMD obtained by DXA (r = 0.478 to 0.629) increased with increasing femoral length. BMD determined by pQCT correlated well with VBD (r = 0.953, P;0.001 in adults; r = 0.758, P;0.01 in juveniles) and the calcium concentration examined chemically (r = 0.805, P;0.001 in adults; r = 0.916, P;0.001 in juveniles). BMC determined by DXA correlated well with the calcium content (in g) examined chemically (r = 0.992, P;0.001). In juvenile dogs, any values correlated regardless of their unit and method used. However, in adult dogs BMD obtained by DXA did only correlate with (1) BMD obtained by pQCT, (2) calcium concentration and (3) VBD when data were adjusted to femur length (r = 0.827 to 0.890, P;0.001).
In adult dogs, left-to-right variability was generally low, highest in the distal metaphyseal region. Conclusions: BMD measurements using DXA may not be compared to pQCT measurements or chemical/physical results unless these are obtained in dogs of identical femur sizes or corrected for different femur sizes.