Quantitative ultrasound of os calcis in postmenopausal women with spine and hip fractures

Quantitative ultrasound (QUS) of the os calcis has been shown to predict hip fracture in late post-menopausal women, and vertebral and forearm fracture in early postmenopausal women. Speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness index (SI) of the os calcis were measured using the Achilles ultrasonometer (Lunar, Madison, WI). Osteoporosis risk factors were assessed by a detailed questionnaire. We examined 1314 normal women from age 48 to 79 yr, with a mean age of 60 +/- 7.5 yr. In addition, we examined women of similar age, of whom 80 had suffered a hip fracture and 40 a spine fracture. The short-term precision in vivo expressed as the coefficient of variation was 1.2% for BUA, 0.2% for SOS, and 1.3% for SI. A total of 813 women were measured at both the right and left heel. There was a high correlation between the two sides (r = 0.80-0.93) (p < 0.001), with no systematic offset. The ultrasound variables decreased significantly (p < 0.001) with age in healthy women; the annual decrease was -0.4% for BUA, -0.07% for SOS, and -0.7% for SI. BUA, SOS, and SI discriminated (p < 0.001) between fracture and non-fracture subjects, but the fracture groups were 2 to 4 yr older. The T-score in the controls averaged -2.1 whereas that in the fracture patients averaged about -3.0. After control for age, years since menopause, and body size, BUA, SOS, as well as the SI remained significantly lower (11 to 12% for SI) in women with fracture. The Z-score was -0.8 (p < 0.01) in spine fracture cases, and -0.9 (p < 0.001) in hip fracture patients. QUS provides a gradient of fracture risk comparable to X-ray densitometry of the axial skeleton, and gives comparable Z- and T-scores in younger postmenopausal women. It provides a precise, radiation-free, low-cost, and rapid method for fracture risk assessment in clinical practice.