Researchers in Wednesday's Journal of the American Medical Association, said spinal fusion surgery using bone growth products resulted in higher rates of complications than conventional spinal fusion procedures, and increased total hospital charges by 11 to 41%.

Dr. Kevin Cahill of Harvard-affiliated Brigham and Women's Hospital in Boston and lead researcher of the study said, "Some of these complications are life-threatening because the neck is such a sensitive area."

The protein product, BMP was approved by the Food and Drug Administration in 2002 for back surgeries and became a favorite with surgeons as this product makes it unnecessary to surgically harvest the patient's own bone from the shin or hip for a graft. The researchers found doctors used it in 17,623 spinal fusions in 2006, which were nearly 1 in 4 cases.

Previous smaller studies showed BMP to promote better healing of the bone and fewer repeat surgeries to fix failed spinal fusions. However question on the products safety arose last year when used in fusion surgeries in the neck region, a use not approved by federal regulators.

Last July, the FDA warned doctors of unapproved or off-label use of bone growth products had been linked with about 38 reports of complications when the treatment was used in the neck region of the spine as some patients had swelling after surgery that caused problems with breathing and swallowing.

Minneapolis-based Medtronic and Kalamazoo, Mich.-based Stryker are two companies who produce BMP. Marybeth Thorsgaard, Medtronic spokeswoman said the company added a label warning about neck complications in 2005. She added that the JAMA study only looked at hospital-related costs and complications. "Other studies have demonstrated reduced complication rates and reduced associated costs with the use of BMP long term."

Stryker in an e-mailed statement said BMP products should only be used by doctors in approved uses which do not include spinal fusions in the neck.

Spinal fusion is one option considered for people with back and neck pain, in which a surgeon removes the shock-absorbing disc between two vertebrae and replaces it with the patient's own bone, BMP or another product. Ideally, new bone grows and fuses the vertebrae into one piece, stabilizing the spine.

Of the two companies Medtronic's BMP InFuse is in a liquid solution, which is implanted on a collagen sponge in a titanium cage while Stryker's product OP-1 Implant and OP-1 Putty has the consistency of wet sand. They both contain recombinant, or genetically engineered human bone morphogenetic protein or BMP, an artificial protein used to promote bone growth.

Researchers in the new study looked at records of 328,468 spinal fusions from 2002 to 2006, including more than 17,000 performed with BMP in 2006. They found complications in 7 % of patients before they left the hospital when BMP was used in the front of the neck region of the spine, which was a 50 % higher rate compared to when the product wasn't used. However they found no differences in rates of overall complications based on BMP use for fusions of the lower back or lumbar spine, or the upper back or thoracic spine.

They also found no increased complications in neck surgery in which the incision was done in the back of the neck. In the case of anterior cervical fusion or spinal fusion surgery in which the incision was done through the front of the neck was however found to be associated with higher complication rates. Complication rates in these procedures were about 7.09 % in BMP-treated patients, compared with 4.68 % in those who got spinal fusion without BMP.

The team reported that spinal fusion surgery was also linked with longer hospital stays, and higher costs across all kinds of fusion surgery with anterior cervical fusion accounting for the highest increases.

The study was funded by the Brain Science Foundation.