Rh-BMP-2 in distraction osteogenesis: Dose effect and premature consolidation

Abstract 

We asked whether locally applied recombinant-bone morphogenic protein-2 (rh-BMP-2) with a type I collagen carrier could enhance the consolidation phase in distraction osteogenesis and whether a dose effect could be reported. We performed unilateral transverse osteotomy of the tibia in 15 immature male rabbits. In Group I (five rabbits), 750μg of rh-BMP-2 on the type I collagen sponge (Inductos^®, Medtronic) was locally applied on the day of osteotomy; the Group II animals (five rabbits) received 375μg of the drug and the Group III (control group, five rabbits) had no local application. After 7 days, 3 weeks of distraction was begun at a rate of 0.5mm/12h. Starting week 2 of distraction, we assessed radiographic, ultrasonographic, and densitometric parameters once per week. Animals were sacrificed after a 3-week consolidation period. Radiographic evaluation revealed increased regenerate ossification in the rh-BMP-2 groups compared with the control group. The bone mineral content was significantly higher in the rh-BMP-2 treated groups at each time point. A dose effect is shown as densitometric parameters were significantly higher between Groups I and II. 3/5 of the Group I treated animals developed a premature bony union in the regenerate resulting in premature fusion and incomplete distraction.

Keywords: BMP, Distraction osteogenesis, Premature fusion, Bone healing