Tibial fracture healing accelerated by rap-style bone stress simulator in goats

Objective To observe the effects of axial stress of different magnitudes and vibrations on tibial fracture healing in goats. Methods Models of tibial fracture internally fixated by plate were built in 72 healthy goats. The models were then randomly divided into 4 groups which were subjected to axial stress of 4 sets of parameters implemented by a rap-style bone stress simulator: 350 N and 1.5 Hz (experimental group 1), 200 N and 1.0 Hz (experimental group 2), 50 N and 0.5 Hz (experimental group 3) and zero stress simulation (control group). The treatments started 7 days after operation, followed by twice per day for 30 minutes per time, and lasted for 6 weeks altogether. Tibial radiographs were taken for each goat on the first day, and at 3, 6 and 9 weeks after operation. Six goats out of each group were killed every 3 weeks for biomechanical and histological analyses to evaluate fracture healing. Results X-ray examinations showed the Lane-Sandhu X-ray score in experimental group 2 was significantly higher than in the other 3 groups on the first day, and at 3, 6 and 9 weeks after operation (P 0.05). Histochemical staining (HE and Masson) showed the osteotylus quantity was greater and the healing process faster in experimental group 2 than in the other 3 groups. The density of new trabecular bone and content of collagenous fiber in osteotylus were significantly higher in experimental group 2 than in the other 3 groups at 3, 6 and 9 weeks after operation (P< 0.05); the differences between experimental groups and control group were significant (P< 0.05); there was also a significant difference between experimental groups 3 and 1 (P< 0.05). Conclusions Tibial fracture healing can be accelerated by stimulation of axial stress implemented by a rap-style bone stress simulator in goats. The best parameters of axial stress may be 200 N and 1.0 Hz. Key words: Tibial fracture; Fracture healing; Stress, mechanical; Models, animal