Osteoporosis Int (1993) 3:249-254 © t993 European Foundationfor Osteoporosis Osteoporosis International Original Article Ultrasound Measurements on Os Calcis: Precision and Age-Related Changes in a Normal Female Population A. M. Schott, D. Hans, E. Sornay-Rendu, P. D. Delmas and P. J. Meunier INSERM Unit 234, H6pital Edouard tterriot, Lyon,France Abstract. We performed ultrasound measurements in the calcaneus of 512 healthy women. Broadband ultrasonic attenuation (BUA) and speed of sound (SOS) were obtained with a Lunar Achilles ultrasonic instrument. Subjects studied were one group of 67 women working in our hospital (group A) and two groups which are part of two large prospective cohort studies (groups B and C). Group B consisted of 244 women aged 31-79 years randomly selected from a large insurance company, and group C consisted of 201 women aged 74-91 years randomly selected from the electoral rolls. Dual-energy X-ray absorptiometry (DXA) measurements of femoral neck and total body were performed with a Hologic QDR 2000 for group B and with a Lunar DPX Plus for group C. The in vitro precision of the Achilles, estimated by measuring a phantom daily for 45 days, was 0.84% for BUA and 0.12% for SOS. We assessed the in vivo short-term precision in 20 healthy volunteers working at the hospi- tal, measured three times each. The coefficients of variation were 0.93% (+0.21) for BUA and 0.15% (+0.03) for SOS. The precision error was compared with the true variation, to obtain a standardized coeffi- cient of variation. We analysed the three groups pooled together (n=512) and found for BUA an average 20% decrease and for SOS a 5% decrease between the ages of 20 and 90 years. We also performed separate analyses of subjects younger than 50 and older than 50 years, and within each 10-year age group we found that BUA was stable or slightly increased from 20 to 50 years and then decreased after 50. In contrast, SOS did not increase but decreased from the age of 20. We compared DXA Correspondence and offprint requests to: A. M. Schott,INSERM Unit 234, EpidemiologySection, Pavillon F, H6pital Edouard Herriot, 69437 Lyon Cedex03, France. measurements of the femoral neck and the total body with ultrasound measurements in groups B and C. In both groups the correlations were better with total body DXA than with femoral neck and spine DXA. Keywords: Bone mineral density; Broadband ultrasound attenuation; Speed of sound; Ultrasound Introduction The most commonly used technique for assessing bone mass is dual-energy X-ray absorptiometry (DXA). DXA is a precise method for the determination of bone mineral density but it gives little information on bone strength, which is also dependent on bone microarchi- tecture and elasticity. For a similar bone density, the risk of hip fracture increases with age, and there is a large overlap between women with and without fracture [1]. This supports the theory that bone strength does not rely on bone mass alone, and that an ideal screening tool should detect fragility and not just decreased bone mass. In 1984, Langton published the first paper showing that when the frequency of ultrasound waves varies between 200 and 600 kHz the gradient of attenuation provides information on the bone density [2]. Ultrasound measurements are the speed of sound (SOS) and the broadband ultrasound attentuation (BUA). SOS represents the velocity of ultrasound transmission through the bone and is expressed in metres per second (m/s). This is influenced by the elasticity and the density of the bone measured [3].