The Effects of rhBMP-2 Injection at Distraction Osteogenesis of Rats' Tibia

Abstract

Distraction osteogenesis is the popular method of bone-lengthening procedure. Delayed consolidation of bone after distraction osteogenesis makes complications related to external fixator and refractures after removal of external frame. We hypothesized that only rhBMP-2(recombinant human bone morphogenetic protein-2) could accelerate the long bone healing. 18 Sprague-Dawley rats were divided into two groups after 5 mm lengthening by distraction osteogenesis. The control group was none-injected group and the experimental group was injected 0.5 cc of 0.05 mg/ml rhBMP-2. We evaluated the 6 samples respectively at different time point (2, 4, 8 weeks) using simple radiographs, micro-CT and histological stains. According to the simple radiographs, bone consolidation of percentage pixel count was higher in the experimental group at 2, 4, 8 week, and statistically significant higher than the control group at 8 weeks (p < 0.05). Percentage bone Volume, trabecular thickness in the experimental group was higher than the control group by evaluation with micro-CT. According to the histological examinations, neovascularization and new stromal cells were observed in the control group at 2 week- speciemen but intramembranous ossification was seen at 2 week- specimens in the experimental group. Intramembranous and enchondral ossification was seen in the experimental group but not seen in the control group at the 4 week-specimens. Trabeculae thickness in the experimental group was thicker than the control group at 8-week specimens. Only local injection of rhBMP-2 at the distraction site could accelerate the bone healing during distraction osteogenesis.