Precision of measurement by dual-energy X-ray absorptiometry of bone mineral density and content in rat hindlimb in vitro

Dual-energy x-ray absorptiometry (DXA) is a precise and effective method for measuring bone mineral density (BMD) and content (BMC) at various skeletal sites in the human, but its precision for measuring low BMD and BMC in tiny rat bones has scarcely been evaluated. The short-term precision of DXA (Norland XR-26) for eight regions of interest (ROI) was determined by measuring dissected, not totally defleshed hindlimbs from four rats of differently weights 10 times consecutively. The accuracy of the BMD (area) measurement was also evaluated. The following average precision values (coefficients of variation) with negligible reanalysis error were obtained for BMD and BMC measurements: 0.7 and 1.2% (total); 0.9 and 1.2% (femur); 1.3 and 2.8% (tibia); 1.3 and 2.1% (foot); 2.1 and 4.7% (proximal femur); 1.4 and 2.9% (femoral shaft); 1.8 and 5.6% (distal femur); and 2.7 and 7.6% (proximal tibia). As for the accuracy, BMD measured in tiny bones is likely to be markedly underestimated. We conclude that the standard DXA technique without additional modification for small animal measurements is a precise method for BMD and BMC measurements at multiple sites in rat hindlimb in vitro.