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

Summary Aim To examine the effectiveness of administering recombinant human bone morphogenetic protein-2 (rhBMP-2) in distraction osteogenesis. Material and methods Twenty-one mature male Japanese white rabbits underwent unilateral mandibular osteotomy. After 5 days, the osteotomized mandibles were distracted 1mm/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 [ n = 5 ]) of distraction, rhBMP-2 mixed with collagen gel was injected into the distraction zone. In control groups (groups C-1 [ 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.