Ultrasound weighs fracture risks for elderly women

An Achilles' heel may not be such a bad thing after all. Data from a prospective study performed in Switzerland on more than 6000 women showed that an ultrasound scan of the heel, combined with other clinical parameters, may predict the risk of fractures in elderly women afflicted by osteoporosis.

Osteoporosis and the incidence of fractures associated with the condition may become one of the most pressing public healthcare issues of the 21st century, according to several independent studies. Albeit effective, the dual x-ray absorptiometry exam used to determine bone mineral density may fall short of satisfying worldwide demand.

"The incidence of osteoporosis will outpace economic resources," said principal investigator Dr. Idris Guessous, a senior research fellow in the internal medicine department at Lausanne University Hospital.

Safe and cost-effective methods identifying the best candidates for DXA measurements will be crucial to managing the condition successfully, Guessous said. With this premise in mind, Guessous' team proposed a quantitative sonography exam of the heel that incorporates clinical factors to predict the risk of osteoporosis-related fractures.

For three years, Guessous and colleagues prospectively enrolled 6174 women aged 70 and older at 10 major Swiss osteoporosis centers. Patients underwent a quantitative ultrasound exam that calculates bone strength at the heel, or the stiffness index. Investigators developed a predictive rule for osteoporotic fracture using the ultrasound stiffness index plus four other factors: age, history of fracture, a failed osteoporosis chair test, and a recent fall. A low stiffness index value was considered a high-risk indicator for fractures.

The combined predictive rule helped classify 1464 women as low-risk subjects and 4710 at higher risk. After a mean follow-up of 2.8 years, researchers found that 290 women (6.1%) in the high-risk group developed fractures compared with only 27 (1.8%) in the lower risk group. Ninety percent of women with hip fractures were in the high-risk group. Investigators published their findings in the July issue of Radiology.

Study participants filled out questionnaires every six months to record changes in medical conditions or medications as well as fractures. When a fracture occurred, subjects had to specify its location and trauma level and include a medical report from their physicians.

In addition to being portable and relatively inexpensive, quantitative sonography poses other advantages over DXA, according to researchers. Besides density, it can be used to assess bone architecture and elasticity. Previous studies have also established low quantitative stiffness values as an independent risk factor in peri- and postmenopausal women.

The test is not perfect, however, with a specificity of about 23%. But just as with other screening tests, physicians who consider using this approach should privilege its high sensitivity (90%) to assess osteoporotic fracture risk, Guessous said.

Study results suggest the test is not only effective at determining which women are the best candidates for further testing, it may also be helpful in identifying subjects who can safely do without them, she said.

"It can be used to identify a population at a very low fracture probability in which no further diagnostic evaluation may be necessary," Guessous said.

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