Heel ultrasound predicts osteoporotic fracture risk

Medical Tribune August 2008 P5
David Brill

A simple formula combining clinical information with quantitative ultrasound data from the heel can be used to predict whether a woman is at risk for osteoporotic fractures, a study has shown.

The prediction rule, which assigns patients a risk score from 0 to 14, was tested in 6,174 Swiss women aged 70 to 85 who were followed up for 2.8 years.

Rates of osteoporotic fracture were 6.1 percent among women defined as high-risk and 1.8 for those defined as low-risk, when using a cut-off score of 4.5. The sensitivity of the formula using this score was 90 percent.

“The whole idea of this study was to end up with a tool that can be used by primary care physicians on a daily basis,” said Dr. Idris Guessous, lead author of the study which was published in Radiology.

Ultrasound is inexpensive and portable, he added, and could be used as a diagnostic screening tool in countries where costly bone mineral density (BMD) scans are not available. Resource-permitting, the two modalities could be used in combination for select high-risk women he said.

Dr. Lau Tang Ching – consultant rheumatologist at Tan Tock Seng Hospital, Singapore – said that ultrasound could be useful for assessing nursing home patients who would have difficulty visiting hospital for a BMD scan.

He added, however, that he would like to have seen the authors report the continuous score spectrum for fracture risk prediction, rather than using the single cut-off point of 4.5.

“It would also be good if the test characteristics of the ultrasound machine were compared with dual X-ray absorptiometry BMD or with other well established predictors of low BMD such as the Osteoporosis Self-Assessment Test,” said Lau.

The researchers used a quantitative ultrasound device which requires an operator to position the subject’s foot in a water bath. The measurement procedure is otherwise automatic.

“What is really specific to this study is the way that clinical risk factors – history of fractures or recent fall – are combined with this ultrasound technique, so there are two domains that are included in the score,” said Guessous, who is a senior research fellow at Lausanne University Hospital in Switzerland.

“I stress this point because this score may not only highlight the quality of the bone itself, which is a major risk factor for fractures, but it also highlights the risk of fall for a woman.

“Depending on which factors the woman is at risk for you may better target your intervention, so eventually women who are at more risk of falling than having a bad quality of bone may end up having other interventions like hip protectors or rebalancing techniques, than just receiving bisphosphonate drugs,” he said.