Ultrasonic assessment of bone: a review

In the last 25 years several non-invasive techniques based on the attenuation of ionizing radiation have been developed to quantify bone mineral density in the axial and peripheral skeleton. The use of ultrasounds is another technique which has recently been developed to provide information on the architecture and elasticity of bone. The basic principle of ultrasound measurements is that the speed (SOS = speed of sound) at which ultrasounds propagate in the bone, or the extent of their attenuation (BUA = broad-band ultrasound attenuation) through the bone is determined by bone density and by certain physical properties which are intimately correlated with bone strength. Theoretically, ultrasound bone measurements should provide more information about bone fragility and structure than densitometric techniques. As a result of preliminary studies, several ultrasound devices have been developed by manufacturers. Most of them measure the os calcis which consists almost exclusively of trabecular bone. Measurement precision varies with the instrument used and the site of measurement. The in vitro and in vivo precision for SOS and for BUA are reported in this review. The correlations between ultrasound and bone mineral density measurement suggest that these techniques measure different entities. A significant difference is constantly found between normal and osteoporotic women. Transversal studies have shown a negative correlation between ultrasound measurements and age. Age-related variations are much more significant with BUA than with SOS. Several studies suggest the potential of ultrasound measurements to assess the risk for individuals to develop osteoporosis and its usefulness in treatment follow-up. Further prospective studies are needed to better understand the effectiveness of ultrasounds.(ABSTRACT TRUNCATED AT 250 WORDS)