Precision and intersite correlation of bone densitometry at the radius, tibia and femur with peripheral quantitative CT

Objective. To compare the in situ precision of peripheral quantitative CT ( pQCT) at the radius, tibia and femur, and to analyze the intersite correlat ion, in order to determine whether measurements at the lower extremity repr oduce results at the radius or are of additional informative value. Design and material. pQCT measurements were performed in 86 elderly cadaver s (mean age 80.5 years) at trabecular and cortical locations in the radius, tibia and femur, determining densitometric (bone mineral content and densi ty) as well as geometric parameters (cross-sectional area, cortical thickne ss, polar moment of inertia and others). In 14 cadavers, repeated measureme nts were obtained at all sites on four different days. Results and conclusions. At cortical sites, the precision for the densitome tric and geometric variables ranged from 0.4% to 4.3%, and was similar for the radius, tibia and femur. At trabecular locations, the reproducibility o f the density measurements ranged from 1.8% to 2.5% at the radius, and from 3.2% to 5.9% at the femur and tibia. The intersite correlation of the tota l bone mineral content ranged from 0.87 and 0.97 at cortical sites, and fro m 0.63 to 0.85 at trabecular locations. The trabecular density showed a hig her similarity between the tibia and femur (r=0.68-0.78) than between the r adius and the lower extremity (r=0.41-0.45). The results demonstrate a subs tantial heterogeneity of trabecular bone in elderly individuals and advocat e measurements directly at the site of clinical or scientific interest.