Quantification of bone remodeling in the proximal femur following uncemented total hip arthroplasty: A methodological study using dual energy x-ray absorptiometry

The aim of this study was to evaluate the feasibility of using measurements of bone mineral content (BMC) and bone mineral density (BMD) by dual energy X-ray absorptiometry (DEXA) for quantitative measurements of adaptive bone remodeling after implantation of an uncemented femoral component in total hip arthroplasty (THA). The in vitro study showed a lower detection limit of 0.85 g and 0.16 g/cm² for BMC and BMD, respectively. The phantom study on the influence of rotation on the precision error showed that the best average precision was obtained if BMD was used as a measure of bone mineral around the femoral stem in the Gruen regions. Thus rotation along the longitudinal axis of the femoral shaft from 0degree to 45degree yielded an average coefficient of variation (CV) of 7.5% for BMD. The CV was reduced to 3.4% when the range of rotation was reduced to 20degree to 25degree. Triple BMD measurements gave a CV of 0.9%. In the in vivo study 10 patients with uncemented THA were scanned twice with full reposition between the scans. The average in vivo CV was 1.8% and 4.1% for BMD and BMC, respectively. The results show that the method is well suited for longitudinal studies of adaptive bone remodeling in the proximal femur after THA.