Ultrasound of the tibia--precision error, left versus right sides and correlation with bone mineral density

Ultrasound of the tibia measures the speed of sound through cortical bone and is a measure of bone density and strength. Ten subjects were measured twice each on the same side by a single operator using the Myriad Soundscan 2000. Intra-operator precision error expressed as CV% was 0.3%. Inter-operator precision error was also found to be 0.3% when results on the same ten subjects by two operators were analysed. Seventy-four subjects had their speed of sound (SOS) measured on both the left and right tibiae by a single operator. The Pearson correlation co-efficient was 0.83. Fifty subjects had their SOS measured as well as their bone mineral density (BMD) determined by dual energy X-ray absorptiometry (DEXA) using the Hologic QDR 2000. BMD measurements were made at the lumbar spine AP view, neck of femur, trochanter, Ward's triangle and total hip. Pearson correlations between these various sites and SOS were as follows: SOS versus BMD AP spine r = 0.61, P < 0.0001; SOS versus neck of femur r = 0.68, P < 0.0001; SOS versus trochanter r = 0.71, P < 0.0001; SOS versus Ward's triangle r = 0.7, P < 0.0001; SOS versus total hip r = 0.67, P < 0.0001. In conclusion, ultrasound of the tibia is a precise and promising tool in the assessment of osteoporosis. Further studies are needed to document its clinical usefulness.