Ultrasound measurements in the calcaneus: precision and its relation with bone mineral density of the heel, hip, and lumbar spine.

Broadband ultrasound attenuation (BUA) and speed of sound (SOS) in the heel are suggested to measure bone density and structure and to predict fracture risk. Short-term precision (five consecutive measurements in 1 h) and long-term precision (six within 3 months) of ultrasound parameters were studied in 20 healthy subjects. The coefficient of variation (CV) did not change over a 3-month period for SOS (1.3%). Short-term precision of BUA was 3.4% (CV) and long-term precision was 4.9% (CV) (not significantly different: p = 0.09). Relationships between ultrasound parameters and BMD at various sites were examined in 42 subjects. BMD at the heel was assessed at the location corresponding to that of the ultrasound measurements (BMDheel). Correlation coefficients, corrected for imprecision in the measurements, for BUA and SOS vs. BMDheel, were 0.81 and 0.76, respectively. The correlation coefficients between heel measurements (BUA, SOS, and BMDheel) and BMD in the hip and lumbar spine ranged from 0.37 to 0.57. The relationships between BUA, SOS, and BMDheel vs. BMD of the hip were modified by physical activity and body weight. Higher physical activity and body weight were associated with higher BMD values at the hip. BUA values < 60 dB/MHz predicted BMD at the femoral neck < 0.70 g/cm2 with a sensitivity and specificity of 80% and 93%, respectively. After the age of 30, 11 participants had sustained vertebral fractures and 12 participants nonvertebral osteoporotic fractures. BUA and SOS values were significantly lower in fracture patients than in participants without fractures. It can be concluded that ultrasound measurements at the heel correlate well to BMD at the same site. BUA can predict BMD at the hip and is lower when the subject has sustained fractures.