Recombinant Human Bone Morphogenetic Protein-2 on an Absorbable Collagen Sponge with an Osteoconductive Bulking Agent in Posterolateral Arthrodesis with Instrumentation A Prospective Randomized Trial

Background: Recombinant human bone morphogenetic protein-2 (rhBMP-2) on an absorbable collagen sponge has been shown to be a safe and effective replacement for iliac crest bone graft when used with a threaded fusion device in anterior lumbar interbody arthrodesis. Use of rhBMP-2 on an absorbable collagen sponge in posterolateral lumbar arthrodesis requires the addition of a bulking agent to provide resistance against compression and to serve as an osteoconductive scaffold for new bone formation. Methods: We performed a prospective, randomized, multicenter pilot study to investigate the use of rhBMP-2 on an absorbable collagen sponge combined with a ceramic-granule bulking agent as a replacement for autogenous iliac crest bone graft in single level posterolateral lumbar arthrodesis with instrumentation. The investigational group (twenty-five patients) was treated with a 1.5 mg/mL solution of rhBMP-2 on two strips of absorbable collagen sponge (total dose of rhBMP-2, 12 mg) combined with 10 cm(3) of ceramic granules. The control group (twenty-one patients) received iliac crest bone graft. Clinical outcomes were assessed with use of well-established instruments. Radiographs were reviewed to assess consolidation of fusion. Results: Eighty-eight percent (twenty-two) of the twenty-five patients in the investigational group and 86% (eighteen) of the twenty-one patients in the control group were considered to have completed the twenty-four-month follow-up. At all follow-up intervals, there were significant improvements in the clinical outcome measures, including the Oswestry Disability Index (ODI) scores, Short Form-36 scores, and back and leg pain scores, in both groups. At twenty-four months, the improvement in the mean ODI score, as compared with the preoperative score, was 28.2 points in the investigational group and 23.0 points in the control group. By twenty-four months, 95% (eighteen) of nineteen patients in the investigational group compared with 70% (fourteen) of twenty in the control group had a radiographically documented fusion. The overall success rate was 81% (seventeen of twenty-one) in the investigational group and 55% (eleven of twenty) in the control group (p = 0.345). Conclusions: Compared with an iliac crest bone graft, the combination of an absorbable collagen sponge soaked with rhBMP-2 and ceramic granules resulted in trends toward improvements in clinical outcomes and toward a higher rate of radiographic fusion. This combination of an osteoinductive agent with an osteoconductive matrix may be an effective replacement for autograft in single-level posterolateral lumbar arthrodeses with instrumentation.