Bone stress stimulation to promote bone formation and scaffold degradation in rabbit tibial defects

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Objective To explore if postoperative rapping by a bone stress stimulator can accelerate bone formation and degradation of deproteinization bone (DPB) scaffolds in rabbit tibial defects. Methods A segmental bone defect of 5 mm long was created in the middle of the right tibial shaft in 30 New Zealand rabbits which were randomly divided into 3 groups. The defects were stabilized with a plate and screws. In group A (n=12), the bone defect was filled with a DPB matrix scaffold and stimulated by rapping by a bone stress stimulator. In group B (n=12), the defect was just filled with a DPB scaffold. In group C (n=6), the defect was left untreated. The right lower limbs of all the rabbits were fixated with a plaster slab after operation. Lane-Sandhu X-ray evaluation system was used to evaluate the bone healing process by X-ray ex-aminations at 2, 4, 8 and 12 weeks. The osteogenesis and biodegradation speed of the scaffold were evaluated using histological quantitative analysis at 4 and 12 weeks. Results The mean Lane-Sandhu X-ray scores in group A were significantly higher than in groups B and C at all the time points (P< 0.05). At 12 weeks, the bone defects in group C were not repaired, showing successful modeling of bone defects. HE staining showed that at 4 and 12 weeks postoperation the rates of new bone formation area in group A (25.4±4.2% and 38.6%±6.3%) were significantly greater than in group B (7.6%±2.2% and 20.4%±4.2%) (P< 0.05), and the rates of residual DPB area in group A (15.1%±3.7% and 1.3%±0.9%) were signifi-cantly lower than in group B (27.5%±2.4% and 19.7%±4.2%) (P < 0.05). Conclusion Rapping by a bone stress stimulator is effective on promoting callus formation and DPB degradation in the rabbit tibial defects. Key words: Animal experimentation; Osteogenesis; Physical stimulation; Stress, mechani-cal; Scaffolds