Protein may be risky in one spine surgery, safe in another

Oct 7 2011
Several studies have questioned the safety of a protein used to promote spinal fusion. However, new evidence suggests that the protein's value in spine surgery may depend on the site and procedure in which it is used.

Spinal fusion is a surgical procedure that stabilizes motion of the spine by melding consecutive bones. This can be done with bone grafts, which may be taken from another part of the patient's body or from a donor cadaver. The operation may also use cages made with rods and screws, as well as special bone proteins such as rhBMP-2.

There are a variety of conditions that may benefit from spinal fusion. The facet joints that connect the vertebrae are vulnerable to injury or age-related degeneration, which can lead to spondylolisthesis, when a vertebra slips and slides out of place.

Pressure on the spinal cord may be the result of herniated discs or spinal stenosis, in which parts of the spinal canal narrow due to thickening ligaments or bone spurs that grow as a reaction to osteoarthritis. These conditions may be corrected by surgical procedures such as discectomy, laminectomy to remove bone or foraminotomy to widen the opening in the back, according to the National Library of Medicine. These operations are often followed by spinal fusion.

RhBMP-2 in spinal fusion has caused some recent controversy in light of studies suggesting it may cause certain health complications, including nerve inflammation and sexual dysfunction. However, a team of researchers noted many of these reports dealt with anterior cervical fusion, during which surgeons approach the spine from the front of the body. The scientists wanted to see if complications could arise from the use of rhBMP-2 in posterolateral surgeries, which are done from behind and toward the side of the spine.

The team reviewed the medical records of more than 1,000 patients who underwent posterolateral spinal fusion that used rhBMP-2 between 2003 and 2006. The records monitored complications from both surgical procedures, which the review included if they occurred within three months of the operation, and adverse effects from the protein factor by itself, which were included regardless of when they happened.

Results, published in the Oct. 15 issue of Spine, confirmed that at least one patient experienced complications related to rhBMP-2, but suggested that as many as six patients may have been affected. This amounts to less than one percent of patients negatively affected by rhBMP-2, suggesting that the effectiveness and safety of certain treatments depend on the location of the surgical site as well as the type of surgery, the researchers said.