Spine surgery product prompts need for new data review process

Sep 29 2011
Controversy surrounding government agency approval of a product that uses a synthetic bone protein in spine surgery is leading lawmakers and academics to cry foul over the approval process, according to the Journal of the American Medical Association (JAMA).

A manufactured bone graft used in spine fusion includes bone morphogenetic protein-2 (BMP-2), a synthetic substance to promote fusion of the surrounding bones in order to stabilize movement. The Food and Drug Administration (FDA) approved the product for fusion surgery to treat degenerative disc disease of the lower spine in 2002. However, several studies have since called into question BMP-2's safety as well as the ethics behind the data collection used to get FDA approval.

The spinal column consists of the vertebrae, the facet joints and the intervertebral discs that cushion the spaces between the bones. These gel-like discs are vulnerable to both injury and age-related degeneration resulting from the constant physical demands of absorbing shock and stabilizing movement for the spine. If a disc ruptures or bulges out, it can put pressure on the surrounding nerves, causing back pain. This condition can be corrected through surgical removal of part or all of the disc, a procedure known as a discectomy. This surgery is usually followed by another operation known as spinal fusion, which connects the two vertebrae on either side of the excised disc in order to stabilize movement. Fusion can be done through the use of bone grafts from a cadaver, rods, screws or with the help of proteins such as BMP-2.

Medtronic's Infuse Bone Graft received FDA approval in 2002 for anterior lumbar fusion. However, as the product became more popular, even through off-label usage, several studies, including the entire June 2011 issue of The Spine Journal, noted that BMP-2 could have adverse effects, such as infection, sexual dysfunction and nerve inflammation. Furthermore, questions arose regarding Medtronic's payment to clinical investigators of the device, and how their results differed from those of scientists studying BMP-2 without any financial stake in Medtronic, according to JAMA.

Questions about Medtronic's credibility prompted a new collaboration between the manufacturer and Harlan M. Krumholz, M.D., of the Yale University School of Medicine. Krumholz had experience with cases involving drug companies that had not published negative data from clinical trials, which he felt gave him the clout needed to approach Medtronic. The manufacturer responded by giving Krumholz access to all published and unpublished clinical data on their product, as well as a graft to convene an independent panel of experts to review the materials.

If this plan of action works, the collaboration may create a new model for medical device manufacturers to evaluate their products in a way that is more balanced and transparent.

There are several things people can do to help keep their intervertebral discs healthy for as long as possible. Low-impact aerobic exercise can be helpful, according to the National Institute of Arthritis and Musculoskeletal and Skin Diseases, a division of the National Institutes of Health. The agency adds that smoking cessation could also help because smoking can interfere with the body's ability to bring nutrients to the discs.