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Assessment of Bone Growth Stimulator Is Mixed

TUESDAY June 30, 2009 -- A relatively new agent that stimulates the creation of new bone as part of spinal fusion surgery is being increasingly used in the United States, although costs and some complication rates also appear to be higher with its use, a new study reports.

The therapeutic agent, known as bone-morphogenic protein, or BMP, is now used in at least 25 percent of spinal fusion surgeries.

"The use of BMP is rapidly increasing every year," said the study's lead author, Dr. Kevin Cahill, a neurosurgeon at Brigham and Women's Hospital in Boston. The study found that more complications occurred in procedures involving the front part of the neck -- anterior cervical fusions -- when BMP was used.

"In the neck, there's not a lot of extra room, and there seems to be some swelling associated with the use of this product," Cahill said. The most common complications from BMP in neck procedures were difficulty swallowing and hoarseness, according to the study, which is in the July 1 issue of the Journal of the American Medical Association.

The study did not find an increase in complications in other fusion procedures.

Nonetheless, other surgical experts expressed the need for caution.

"This is a very potent substance, and I don't think anyone doubts that it works, but we don't know what dosages are right in each area, and we don't know if it's the right thing to do economically," said Dr. Douglas Burton, an orthopedic surgeon at the University of Kansas Hospital in Kansas City.

And Dr. Richard Fessler, chief of surgery and a neurosurgeon at St. John Hospital and Medical Center in Detroit, said that the study's finding "underscores why off-label use shouldn't be performed indiscriminately."

"We've increased the cost of this procedure, but we're unsure of the effect of BMP in the long term," Fessler said.

BMP -- a protein that the body naturally makes that tells stem cells to form bone -- was approved in 2002 by the U.S. Food and Drug Administration for use in spinal fusion surgeries in the lower back area. Because it promotes bone growth, BMP appears to be helpful in fusion surgeries because it may speed the process and possibly reduce the need for a second operation.

"When you do a fusion, you take out the disc and then you put in a graft so the bones fuse together," Cahill explained. "BMP accelerates this fusion. This is particularly important in some people -- such as smokers or people with diabetes -- who tend to heal slower to begin with. If it takes too long for the bones to fuse, it can be very painful and sometimes may make a second operation necessary."

For the study, Cahill and his colleagues reviewed data from more than 328,000 spinal fusion procedures that took place between 2002 and 2006 in hospitals across the country. They found that the use of BMP in fusion procedures went from less than 1 percent in 2002 to almost 25 percent by 2006.

In most procedures, its use was not associated with an increased risk of complications. However, in procedures done on the front part of the neck, the risk of complications increased by 43 percent when BMP was used -- from about 5 to 7 percent.

The study also found that costs for spinal fusions were higher when BMP was used. Inpatient hospital charges ranged from 11 percent to 41 percent higher for procedures with BMP than for those in which the agent was not used, the study found.

"You need to have a reason to use BMP," said Dr. Frank P. Cammisa Jr., chief of spinal surgery at the Hospital for Special Surgery in New York City. "If there are risk factors or it's a revision surgery, then use it. But, you really need to have a good reason to use it."

Cammisa also pointed out that the study did not find shorter lengths of stay for procedures with BMP and did not look at outpatient complications, which he said might be increased.

"I think [this study] serves as an impetus for surgeons to look for less expensive, but efficacious, bone growth factors other than BMP," he said. Also, Cammisa said, he'd like to see specific guidelines developed for the use of BMP.

Burton, who said the study "highlights the trend that many of us would have guessed, that the use of BMP is skyrocketing," added that more recent data might show something different.

If the study looked at data from 2007, he said, he believes the rates of anterior cervical complications would be reduced because many surgeons aren't using BMP for fusions in that area or are using smaller doses of the biological agent.

The surgeons agreed that more research is needed to determine who is an ideal candidate for BMP use and to assess the costs and benefits of the therapy.

More information

The U.S. National Library of Medicine has more on spinal fusion surgery.

Posted: June 2009


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