So-called "off-label" use of medical therapies is legal, but has triggered concerns because its risks and benefits are not well understood. Yet the new study shows the orthopedic products add more than $4,000 in hospital charges for the surgery.

"It is expensive, we don't know if it's effective, and we don't know what the long-term implications are," said Dr. Emily Dodwell, a surgeon at the Hospital for Special Surgery in New York, who led the research.

Bone-growth proteins speed up bone formation and have been approved by the U.S. Food and Drug Administration for limited use in adults. But they have a troubled history.

Last year, a medical journal determined that doctors paid millions of dollars by Minneapolis-based Medtronic had failed to report serious complications linked to the company's product Infuse, also known as bone morphogenetic protein-2 or BMP-2.

Those complications include increased cancer risk, sterility in men, infections, bone dissolution and worsened back and leg pain, among others.

While it's unclear whether children would experience similar side effects, a particular concern is how BMPs would interact with a still-growing skeleton, Dodwell told Reuters Health.

What's more, there are no good data on whether or not the products help youngsters, who are less likely to have healing problems than adults after spine surgeries, according to the new report, published in the Journal of the American Medical Association.

At about 4,100 hospitals that are part of the national registry studied by the researchers, 9.2 percent of more than 8,000 spine fusions in people 18 years and younger involved BMPs.

"I think most people would feel this is a high number," Dodwell noted, although she stopped short of saying BMP should never be used in minors.

In cases where BMP was used, patients racked up hospital bills of $47,136 on average, compared to $43,126 when surgeons didn't use the product.

There was no difference in the number of complications seen during the hospital stay in the two groups, although Dodwell and her colleagues cautioned that long-term complications are the main concern. She said her team is currently analyzing data from another registry to see how kids fare after they leave the hospital.

The researchers also found that doctors more frequently used BMP in the Midwest, which is home to both Medtronic and Stryker, another manufacturer. Medtronic could not be immediately reached for comment.

Dodwell said this finding is "quite possibly related to industry relationships and the training of the surgeons."

SOURCE: bit.ly/MvXYT6 Journal of the American Medical Association, online October 9, 2012.

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