The role of ultrasound in the assessment of osteoporosis.

There is increasing interest in assessing the role of ultrasound in the identification and management of osteoporosis. Using ultrasound, we may measure the velocity of sound through bone, or the increase in attenuation with frequency, generally referred as Broadband Ultrasonic Attenuation BUA. Although velocity measurements have previously been reported in the patella, current interest is concentrated on the calcaneum. The advantages of ultrasound technology include portability and ease of use of equipment. Measurements are typically performed within a few minutes with a minimal requirement for operator intervention. When comparing ultrasound data with that obtained from established techniques, care must be taken in the interpretation. Simple linear regression assumes that the two parameters measured are directly related. Although ultrasound measurements of the calcaneum significantly correlate with DXA measurements of the spine and hip, these relationships are too weak to permit accurate prediction of BMD by BUA with less than 50% of the variance is explained by density, with the additional dependence of BUA upon trabecular structure being a contributing factor. A more reliable assessment of the value of ultrasound measurements to identify osteoporosis may be obtained using statistical techniques such as diagnostic accuracy defined by ROC analysis and dynamic range. Since the ROC analysis is comparable for calcaneal BUA and lumbar BMD, these tests are of similar value in evaluating fracture risk. The prediction of fracture risk for the hip is greater than for the wrist and vertebrae, suggesting that the future perspectives for the ultrasonic assessment of osteoporosis will primarily be the measurement of elderly women.