Bone morphogenetic protein known as BMP-2 or BMP for short is a growth factor (protein) that helps bone heal and promotes bone fusion. BMP reportedly helps speed up the recovery rate after spinal fusion. BMP is designed to promote bone formation by setting up an inflammatory reaction. This type of enhancer was developed to avoid problems that occur with traditional bone grafting.
In this study, complications from the use of BMP with spinal fusion are explored. The neurosurgeons who conducted the study were interested to know how often and what type of problems occur. They compared complications of spinal fusions done with and without BMP.
This study is unique because of its size and when it was done. Almost 12,000 patients were included from a database of information collected by neurosurgeons around the country. The data was collected between 2004 and 2007, which makes the results very current. The group collecting the information was the Scoliosis Research Society.
Most of the studies reporting results of bone morphogenetic protein (BMP) with spinal fusions have been small. Only one other similar-size study has been published (Cahill, 2009). Results of this new study by the Scoliosis Research Society were compared with the results of the earlier Cahill study.
Neurosurgeons performing spinal fusions (with or without BMP) expect some complications. It goes with the territory, so-to-speak. The studies published up until now have reported problems such as infections, graft failure, and hematomas (pockets of blood). In rare cases, blood clots can cause death after surgery.
A less serious complication reported with the use of BMP in spinal fusions is the formation of too much bone growth. This is called ectopic bone. Ectopic bone can be a problem if the extra bone material presses on nearby nerves.
The Scoliosis Research Society's database is set up to collect information on patent age, diagnosis, type of surgery, type of complications, and need for additional surgery later on. They also found by looking at all spinal fusions (with and without BMP) that about one-fifth (21 per cent) of the all spinal fusions in the database were done with this bone enhancer.
After analyzing information related to complications, they found that problems occurred most often when BMP was used for anterior cervical spinal fusions. Anterior cervical refers to the fact that the surgeon performed a fusion of the neck from a frontal approach (rather than from behind the neck, which would be a posterior approach). Wound infection and hematoma formation were the two most common problems associated with anterior cervical spinal fusion using BMP.
All other spinal fusions with and without BMP had an equal number of complications (around eight per cent for both groups). This is an important finding because if the risk of using BMP during spinal fusions is greater than the benefit, then the surgeon may not want to use BMP. Factors of this type must be taken into consideration when planning spinal fusion procedures.
The authors also took a closer look at the patients in both groups to see if a particular characteristic might be important to study in future research. Age, diagnosis, and location of fusion were three areas of special interest.
The effect of age was difficult to really gauge accurately. In general, patients in the BMP fusion group were older than patients in the group who had spinal fusion without using BMP. The reason for this may have to do with the underlying problem requiring fusion.
Surgeons were more likely to use BMP with older patients who have degenerative spine conditions. Younger (pediatric) patients who had spinal fusion for scoliosis (curvature of the spine) were more likely to be able to generate their own growth factors and form bone without the need for a bone enhancer.
There was no difference in mortality (death) as a complication of spinal fusion between the two groups (with BMP and without BMP). Each group had one death related to stroke, blood clot, or other heart or lung problems.
The only other major finding was that patients who had spinal fusion with BMP were twice as likely to need revision surgery as those who did not have BMP. But even among those patients who required a second surgery, the use of BMP did not increase the number of complications that occurred.
The authors concluded from this study that using BMP as a bone enhancer to foster bone fusion does not increase the patient's risk of complications. This is true EXCEPT when the procedure is an anterior cervical spine (neck) fusion.
Most complications occur as a result of the surgery (with or without BMP) or in relation to other problems that come with age (e.g., heart disease, diabetes). Degenerative diseases of the spine associated with aging is another factor that affects the incidence of complications with spinal surgery.
The authors suggest more studies are needed to look at the amount of BMP used as a potential factor. Long-term results should also be measured and compared with and without BMP. The use of BMP with anterior neck fusions must be studied more closely, too.
Reference: Brian J. Williams, MD, et al. Does Bone Morphogenetic Protein Increase the Incidence of Perioperative Complications in Spinal Fusion? In Spine. September 15, 2011. Vol. 36. No. 2. Pp. 1685-1691.