Dual-energy digital radiography in the assessment of bone mechanical properties

At present, bone fragility and fracture risk are estimated with bone mineral density (BMD), measured by dual-energy x-ray absorptiometry (DXA). It is known that DXA-based BMD (BMD(DXA)) has a relationship with mechanical characteristics of bone. Dual-energy digital radiography (DEDR) has also been shown to be a potential method to determine BMD, but the ability of DEDR-based BMD (BMD(DEDR)) to predict bone mechanical properties is not yet known. In this study, we investigated the ability of BMD(DEDR) to predict the mechanical characteristics of bone. Reindeer femora (N = 50) were imaged at two different energies (79 and 100 kV(p)) using a clinical digital radiography system. BMD was determined in four regions from these images using the DXA calculation principle. Femora were mechanically tested using axial loading configuration. Mechanical parameters were correlated with the BMD(DEDR) and BMD(DXA) of the femoral neck (FNBMD(DEDR) and FNBMD(DXA)). FNBMD(DEDR) and FNBMD(DXA) both correlated moderately with mechanical parameters. The highest correlations were found with maximal load (r = 0.53 and r = 0.65, p < 0.01, respectively). No statistically significant differences were found between the correlation coefficients when comparing the FNBMD(DEDR) or FNBMD(DXA) values and mechanical parameters. The correlation coefficient between BMD(DEDR) and BMD(DXA) varied between r = 0.56 and 0.86 (p < 0.01) in different regions of the upper femur. In conclusion, BMD(DEDR) predicts the mechanical parameters of reindeer bone with similar accuracy as BMD(DXA).