The efficacy of rhBMP-2 for posterolateral lumbar fusion in smokers

Retrospective review of prospectively collected data, as part of an IRB-approved, FDA-regulated, randomized, nonblinded IDE trial of rhBMP-2 matrix for lumbar spinal fusion. The purpose of this study is to examine the influence of smoking on fusion rate and outcome in a large series of patients treated with an rhBMP-2 matrix (AMPLIFY) or iliac crest bone graft as part of a randomized IDE trial for single-level lumbar fusion. Preclinical studies suggest that bone morphogenetic proteins (BMPs) are able to reverse the negative influence of nicotine on fusion healing in animal models. It remains unclear if a similar benefit will be seen in humans, and if so, what formulation and amount of BMP will be required to achieve that improvement. We reviewed the clinical and radiographic records of 148 patients who underwent single-level instrumented lumbar fusion at three spine centers as part of an ongoing FDA-regulated IDE trial. Clinical outcome measures included Oswestry Disability Index, SF-36, back, and leg pain scores. Radiographic measures were plain radiographs with flexion-extension views and fine cut computed tomography scans with sagittal and coronal reconstruction. Fusion success was determined by independent radiologist readings. At 2 years postoperatively, solid fusion was demonstrated in all 55 nonsmokers in the rhBMP-2 group (100%). Successful fusion was seen in 20 of 21 smokers in the rhBMP-2 group (95.2%). Fusion was achieved in 48 of 51 nonsmokers in the iliac crest bone graft (ICBG) group (94.1%), but only 16 of 21 smokers (76.2%) in the ICBG group. The results of this study suggest that rhBMP-2 may enhance fusion rate in cigarette smokers undergoing single-level instrumented posterolateral lumbar fusion. Despite the improvement in fusion rate with rhBMP-2, clinical outcomes measures were still adversely affected in smokers.