Outcomes improved with rhBMP-2 vs. iliac crest bone graft for fusion

Trends in operative time, hospital stay and other key measures indicate that rhBMP-2 is a viable alternative.

Issue: January 2005

Using recombinant human bone morphogenetic protein-2 on an absorbable collagen sponge proved better in several ways than iliac crest bone graft for lumbar spine fusion.

An earlier study with a small series of patients showed that rhBMP-2/ACS promotes new bone formation and incorporation of the allograft device in patients undergoing anterior lumbar interbody fusion, said J. Kenneth Burkus, MD, of the Hughston Clinic in Columbus, Ga. Burkus presented the study results at the North American Spine Society 19th Annual Meeting in Chicago.

A total of 85 patients were randomized at 13 centers to either iliac crest bone graft (30 patients) or rhBMP-2/ACS (Infuse Bone Graft, Medtronic Sofamor Danek) at a concentration of 1.5 mg/mL (55 patients), according to the abstract. To be included patients needed to have symptomatic, one level lumbar degenerative disc disease with less than grade I spondylosis. All patients underwent anterior lumbar interbody fusions with threaded cortical allografts (MD II Bone Dowels).

Researchers measured outcomes using the Oswestry Disability Index, SF-36, work status, and questionnaires regarding back and leg pain. Radiographic assessment was done preoperatively and at 1.5, three, six, 12 and 24 months after surgery, while CT scans were examined for fusion assessment at six, 12 and 24 months.

Several improvements

Researchers found improvements in the rhBMP-2 group in average operative time (1.2 hours vs. 1.7 hours, P<.001) and blood loss (71.4 mL vs. 140.5 mL, P=.001). The average hospital stay was improved as well, but this was not statistically significant (2.7 days for the rhBMP-2 group, 3.1 days for the control group).

Oswestry scores improved 33.1 points in the rhBMP-2 group vs. 31.5 points for the control group, and there were also greater improvements in SF-36 evaluations. The major difference in pain between the two groups: donor site pain for those receiving the iliac crest autograft.

Of the rhBMP-2 patients, 70.8% returned to work by 24 months compared with 65.5% who were working prior to surgery. For the control group these numbers were 63.6% and 53.3%, respectively.

Fusion rates for rhBMP-2 were excellent, with 98% achieving fusion at 12 and 24 months. For the control group, 89% achieved fusion at 12 months and 82% at 24 months.

“In both groups, pain was dramatically reduced from preoperative levels, and improved results were maintained through 24 months’ follow-up,” Burkus said. “Clinical outcomes comparing rhBMP-2 to autograft demonstrate that the use of rhBMP-2 can eliminate the need for harvesting iliac crest bone graft. For successful lumbar fusions, these improvements remained evident through two years of postoperative follow up.”

Matthew Gornet, MD, of the Orthopedic Center of St. Louis and a coauthor of the study, agreed that the study shows the viability of rhBMP-2 with bone dowels vs. autograft. “There tends to be a push back and forth from either using titanium or different types of manufactured implants vs. more natural implants,” he told Orthopedics Today. “In this study we showed that we can get very good reproducible results with bone and some of these newer proteins.”

Gornet said that a secondary effect is that imaging is much easier with rhBMP-2 because it is a natural substance. This also could lead to the improved fusion rates vs. autograft. “Sure, it’s donor bone, but your body will ultimately rework it, remake it into its own,” he said in a phone interview. “It heals extremely well, and the fusion rates were 98%.”

Dr. Burkus is a paid consultant for a company mentioned in this article.
For more information:
Burkus JK, Gornet M, Longley M. A large randomized clinical evaluation of rhBMP-2 versus iliac crest bone graft combined with cortical allograft in lumbar spine fusion. # 67. Presented at the North American Spine Society 19th Annual Meeting. Chicago.