The authors retrospectively studied 200 subjects that underwent anterior cervical discectomy, ACDF, and fusion with the use of recombinant human bone morphogenetic protein-2 (rhBMP-2). This is an osteoinductive protein that is placed at the fusion site in a sponge. The Federal Drug Administration has approved rhBMP-2 for use in lumbar spine fusion. It has been found to reduce time in surgery, blood loss, and shorten hospital stay. It also avoids the need to harvest bone from the iliac crest, or use bone from cadaver. The authors used this protein off-label in the cervical spine. Complications, particularly hematoma and cervical swelling have been as high as 27.5 percent in reports using rhBMP-2 in the cervical spine.
Of the 200 subjects studied, 193 were included in the study. Ninety six of the subjects had single level ACDF, 62 had two level fusions, 36 had three level fusions, and six had four level fusions. The authors rated outcomes as good to excellent in 85 percent of the subjects, fair in 12.4 percent, and poor in two percent of the subjects. All of the subjects had solid fusions, verified with dynamic X-rays and computed tomography, CT, scans.
These subjects were divided into three groups, those with a total dose of 21 mg of rhBMP-2 per level, those with 1.05mg per level, and those with 0.7 mg per level. Sponges were soaked in the rhBMP-2. In all the subjects the rhBMP-2 soaked sponge was placed within a polyetheretherketone (PEEK) spacer. No sponges were placed outside the PEEK spacer.The authors did not feel that there was a significant difference in complication rate between the three groups. Other surgeons have opted to place the rhBMP-2 on the exterior of the graft or use cages for grafts, rather than PEEK spacers. The authors concluded that rhBMP-2 in the anterior spine is likely related to an increased rate of significant swelling when used in the cervical spine.
The authors reported complications in seven percent of their patients. This is significantly fewer than previous reports. Only two percent required repeat surgery due to hematoma or seroma. Eleven percent of subjects experienced dysphagia. Multi-level ACDF tended to be a risk factor for greater incidence of dysphagia, and more severe dysphagia. The authors noted that the rate of clinically significant dysphagia in one and two level ACDF with low dose rhBMP-2 is similar to the rate of dysphagia seen in ACDF without rhBMP-2. However, with three and four level fusions, the total amount of rhBMP-2 exceeded 3mg, and the dysphagia rate was increased.
The addition of rhBMP-2 may raise the cost of operation significantly. However, it appears to reduce the risk of pseudoarthrosis compared to allograft fusion, particularly in smokers and those with osteoporosis. Complication rate when using fhBMP-2 was similar to other surgical procedures when it is placed within a PEEK spacer.