Effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) on bone consolidation on distraction osteogenesis: a preliminary study in rabbit mandibles

Aim: To examine the effectiveness of administering recombinant human bone morphogenetic protein-2 (rhBMP-2) in distraction osteogenesis. Material and methods: Twenty-one mature mate Japanese white rabbits underwent unilateral mandibular osteotomy. After 5 days, the osteotomized mandibles were distracted 1 mm/day for 10 days. On the first day (groups A-1 [n = 4] and A-2 [n = 4]) or on the last day (group B in = 5]) of distraction, rhBMP-2 mixed with collagen gel was injected into the distraction zone. In control groups (groups C-I [n = 4] and C-2 [n = 4]), the mandibles were distracted without rhBMP-2 injection. At the end of the distraction period (groups A-1 and C-1) and after 2 weeks of consolidation (groups A-2, B, and C-2), the distracted mandibles were harvested and examined with soft radiographs, peripheral quantitative computed tomography (pQCT), and microscopy. Results: Radioopacity was more marked in the distraction zone of the groups with rhBMP-2 than in control groups. The mineral density of the cortical bone (BMD) was higher in groups B and A-2 than in group C-2. Histologically, bone formation was more advanced in groups A-2 and B than in group C-2. The cortical BMD was higher in group A-1 than in group C-1. Histologically, bone formation was more advanced in groups A-2 and B than in group C-2. Conclusion: These results suggest that rhBMP-2 promotes bone formation in distraction osteogenesis. (C) 2006 European Association for Cranio-Maxillofacial Surgery.