A reliable method for measuring proximal tibia and distal femur bone mineral density using dual-energy X-ray absorptiometry.

PURPOSE To assess the intra- and inter-rater reliability of a standardized protocol for measuring proximal tibia and distal femur bone mineral density (BMD) using dual-energy X-ray absorptiometry (DXA). METHODS Ten able-bodied individuals (7 males) participated in this study. During one measurement session, the knee of each participant was scanned twice by rater 1 using DXA. Both scans were analyzed twice by rater 1 as well as once by a second rater. Intraclass correlation coefficients (ICCs), standard error of measurements (SEMs) and smallest detectable differences (SDDs) were calculated for the outcome measures proximal tibia and distal femur BMD. A decision study was performed to determine the effect of study protocol adjustments (i.e. increasing the number of scan repetitions, or scan analyses by the same rater) on SEM and SDD values. RESULTS High intra- and inter-rater ICCs (0.97-0.98) were found for both proximal tibia and distal femur BMD. Low SEMs (0.017-0.028 g/cm(2)) and SDDs (0.047-0.077 g/cm(2)) were found, with a slightly better result for proximal tibia BMD. Increasing the number of scan analyses by the same rater did not markedly reduce SEM and SDD values, while increasing the number of scan repetitions did. CONCLUSIONS Proximal tibia and distal femur BMD can be reliably assessed with this method.