Background: The ability of ultrasonographic measurements to discriminate between patients with hip fracture and age-matched controls has until now been tested mainly through cross-sectional studies. We report the results of a prospective study to assess the value of measurements with ultrasound in predicting the risk of hip fracture.
Methods: 5662 elderly women (mean age 80.4 years) had both baseline calcaneal ultrasonography measurements and femoral radiography (dual-photon X-ray absorptiometry, DPXA) to assess their bone quality. Follow-up every 4 months enabled us to identify incident fractures. 115 hip fractures were recorded during a mean follow-up duration of 2 years.
Findings: Low calcaneal ultrasonographic variables (obtained from measurements of broadband ultrasound attenuation by, and speed of sound through the bone) were able to predict an increased risk of hip fracture, with similar accuracy to low femoral bone mineral density (BMD) obtained by DPXA. The relative risk of hip fracture for 1 SD reduction was 2.0 (95% CI 1.6-2.4) for ultrasound attenuation and 1.7 (1.4-2.1) for speed of sound, compared with 1.9 (1.6-2.4) for BMD. After control for the femoral neck BMD, ultrasonographic variables remained predictive of hip fracture. The incidence of hip fracture among women with values above the median for both calcaneal ultrasound attenuation and femoral neck BMD was 2.7 per 1000 woman-years, compared with 19.6 per 1000 woman-years for those with values below the median for both measures.
Interpretation: Ultrasonographic measurements of the os calcis predict the risk of hip fracture in elderly women living at home as well as DPXA of the hip does, and the combination of both methods makes possible the identification of women at very high or very low risk of fracture.