Correlation between the values of bone measurements using DXA, QCT and USD methods and the bone strength in calcanei in vitro.

In this study we used the calcanei from 32 female and 29 male cadavers, ages 58 to 100. The bone mineral density (BMD) and average bone density (ABD) were measured using dual energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) respectively, while speed of sound (SOS), broadband ultrasound attenuation (BUA) and stiffness index (SI) were measured using ultrasound densitometry (USD). Thereafter, the bone strength was measured using a compressor to cause bone fracture, and evaluated in comparison with the values of the three measurement methods. The scatter diagrams of the values of the three different methods versus age displayed a negative linear regression in both sexes. Values for BMD and ABD were generally about 20% higher in males than in females, while SOS, BUA and SI were a few percents higher in males than in females. A significantly high correlation existed between BMD and ABD (r = 0.95), and a moderate correlation between BMD and either SOS, BUA or SI (r = 0.65; r = 0.39; r = 0.57, respectively). Thus, among the values measured using USD, SOS most closely corresponded to BMD of the calcanei. The bone strength of the calcanei indicated a moderate correlation with BMD, ABD and SOS (r = 0.38, P < 0.01; r = 0.43, P < 0.001; r = 0.45, P < 0.001, respectively). However, 42 calcanei fractured under pressures of less than 40 kgf, although the other 19 calcanei endured pressure of 40 kgf or more. Two calcanei with high BMD over 0.7 g/cm2 by DXA were very fragile, whereas a few with low BMD less than 0.4 g/cm2 were not very fragile. Similarly, high SOS, BUA and SI values by USD did not always correspond to high bone strength. Thus, some discrepancies among the bone strength and measurement values remained to be solved in the future.