Clinical Outcomes and Fusion Success at 2 Years of Single-Level Instrumented Posterolateral Fusions With Recombinant Human Bone Morphogenetic Protein-2/Compression Resistant Matrix Versus Iliac Crest Bone Graft

Abstract

This is a prospective, randomized study comparing iliac crest bone graft to bone morphogenetic protein (BMP)/compression resistant matrix in instrumented posterolateral fusions for single-level lumbar degenerative disease. A higher recombinant human bone morphogenetic protein (rhBMP)-2 dose and a carrier specific for posterior spine applications were used. As part of a Food and Drug Administration IDE study, clinical outcomes and fusion rates of single-level instrumented posterolateral fusions using iliac crest bone graft or BMP/compression resistant matrix were evaluated. Although iliac crest graft is the gold standard for lumbar fusion, alternatives to obviate the morbidity of graft harvest have become available. Randomized clinical trials have demonstrated equivalent fusion rates and clinical outcomes with rhBMP-2 and a collagen sponge versus autograft in anterior lumbar fusions. A human pilot study using rhBMP-2 with biphasic calcium phosphate demonstrated similar results for posterolateral fusions. Demographic and perioperative data, Short Form 36, Oswestry Low Back Pain Disability Index, and leg and back pain scores were determined before surgery, and 1.5, 3, 6, 12, and 24 months after surgery. Independent neuroradiologists' evaluation of fine-cut computerized tomography scans with reconstructions were obtained at 6, 12, and 24 months. There were 98 subjects, 45 in the iliac crest bone graft group and 53 in the BMP/compression resistant matrix group. There were no significant differences for age, weight, sex, smoking, or previous surgery between the groups. The average operative time (2.9 hours) and blood loss (465 cc) in the iliac crest bone graft group was greater than in the BMP/compression resistant matrix group (2.4 hours and 273 cc). There were no significant differences in any outcome measure at all time intervals. The fusion rate was lower in the iliac crest bone graft group (73%) than in the BMP/compression resistant matrix group (88%) at P = 0.051. There was significant improvement of Short Form 36 (physical component score and pain), Oswestry Low Back Pain Disability Index, and leg and back pain scores in both groups over all time intervals. Surgical time and blood loss were significantly less in the BMP/compression resistant matrix group. The fusion rate in the BMP/compression resistant matrix group was significantly higher than the iliac crest bone graft group.