Bone fractures: treatment and risks.

For the millions of people each year who suffer a broken bone, scientists report a new treatment that could hasten healing.

To repair a fracture using the proposed technique, a physician would place a thin tube into the damaged area, mix up a special paste, then inject it into the wound, says Brent R. Constantz, a specialist in biomineralization at the Norian Corp. in Cupertino, Calif. The paste, a new biomaterial described by Constantz and his colleagues in the March 24 Science, hardens in place and accelerates bone replacement.

After realigning a damaged bone and injecting the soft paste, the physician would wait 10 minutes for it to solidify, Constantz says. The paste crystallizes largely as carbonated apatite, or dahllite, a mineral that occurs naturally in the human skeleton. Within 12 hours, the biomaterial is as hard as normal bone, reports Constantz. In fact, he says, the body treats the new material as if it were bone, growing blood vessels into it and "remodeling" the crystals to match natural bone structure more closely.

The researchers believe this biomaterial will prove most useful for treating fractures of the hip, wrist, and shin and for repairing joints and vertebrae.

An average hospital stay for a hip fracture lasts 12 days. The new treatment could shorten that to 7 days, the scientists say. Given an average cost of $29,000 to mend a hip fracture, $20,000 of it for hospitalization, Constantz contends that speedier recoveries could amount to considerable savings.

In Holland, physicians already use the new material to treat fractures, the team reports. In the United States, the Food and Drug Administration has approved a multicenter trial for 324 patients in 12 hospitals. Half of the patients will get standard care and half will try the biomaterial. Physicians will evaluate all patients for 1 year.

The report by Constantz and his colleagues appeared the day after a study identifying risk factors for hip fractures came out in the March 23 New England Journal of Medicine.

To identify what factors predispose some people to hip fractures, Steven R. Cummings, a physician at the University of California, San Francisco, and his colleagues studied 9,515 white women age 65 or older who had never previously broken a hip. In the course of the study, they found that women whose mothers had suffered hip fractures ran twice the average risk of having the same injury.

Also at higher risk were tall women, women who had broken any other bone after age 50, and women with an overactive thyroid gland. Elevated risks showed up for women who took benzodiazepine, used to control anxiety, and anticonvulsants, for avoiding seizures. Consuming too much caffeine and getting too little exercise also correlated with more hip fractures. Gaining weight after age 25 reduced the fracture risk; losing weight increased it.

"There are things people can do to lower their risk," says Cummings. Stay active and quit smoking for starters, he says. Women can cut their caffeine intake, avoid medicines that raise their risk, and take steps, such as estrogen replacement therapy, to increase bone density.

As many as one in six North American white women age 50 or older will suffer a hip fracture in the remainder of their life, as will 6 percent of comparable men. Of the more than 250,000 elderly people who break a hip each year, 20 percent may not survive more than a year, according to the National Institutes of Health. -- R. Lipkin