Results of Osteogenic Putty Used for Single-Level Spinal Fusion
Patients who need a spinal fusion often donate bone graft material from their own iliac (pelvic) crest. This is called an autograft. It takes quite a while for the fusion to occur. Often there are complications at the donor site.
To help with these problems, scientists have developed a special bone graft substitute called OP-1 (rhBMP-7). OP stands for osteogenic protein. Osteogenic means it stimulates bone growth. OP-1 comes in putty form and is now available for use in humans.
In this study, two groups of spinal fusion patients were compared. The first group had a fusion using an iliac crest bone autograft. The second group received the OP-1 putty. All fusions were done at a single spinal level following a decompressive laminectomy (removal of bone pressing on the nerve). The fusions were done without additional instrumentation (use of metal plates or screws).
Results were measured using dynamic X-rays of the moving spine. Fusion status can be assessed by looking at how much bone has developed to bridge the gap from the laminectomy. The X-ray also shows if there is any movement at the fusion site.
Patient function can also be measured using a variety of survey tools. The Oswestry Disability Index and the SF-36 questionnaire are two of the more commonly used tools to compare before and after results. Using these tools, success rates in this study were higher for the Putty patients.
The authors note that at least for the first two years after surgery, the OP-1 Putty provided an equally acceptable alternative to autografts for spinal fusion. There were good rates of fusion seen on X-rays. Patients reported overall improvement in function. There were some problems such as wound infection and pseudoarthrosis (false joint) in the putty group. There were no tumors, toxicity, or neurologic problems with the use of OP-1 putty.
Patients in this study will continue to be followed to assess the long-term results of OP-1 Putty as an alternative to bone autograft material. There is a concern that the putty might deteriorate over time. So far, there's no sign of that happening in the medium- or intermediate-term outcomes.
Alexander R. Vaccaro, et al. The Safety and Efficacy of OP-1 (rhBMP-7) as a Replacement for Iliac Crest Autograft for Posterolateral Lumbar Arthrodesis: Minimum 4-Year Follow-Up of a Pilot Study. In The Spine Journal. May 2008. Vol. 8. No. 3. Pp. 457-465.