Experimental Study Of The Treatment Of The Rap-style Bone Stress Stimulator On Accelerating Fracture Healing Of The Goats, Tibia Shaft

Background: Fracture healing is regulated by the local mechanical environment, and could be significantly promoted by proper axial stress. A rap-style bone stress stimulator had been developed based on this principle by our group, and had obtained the national invention patent.Objective: To investigate the effect of the rap-style bone stress stimulator on accelerating fracture healing the goats, tibia shaft, and to afford an animal experiment base for its clinical application.Methods: Twenty goats of the same species,about 2 years old, and the weight range from 30 to 35 kg, were randomly collected. All the goats were performed with bilateral tibial transverse osteotomy and external fixation with common external fixator, the achillotenotomy was done. And they were randomly divided into two groups postoperation, the one which undewent stress stimulation as the experimental group, and the other was the control group. The treatment was started 1week after the operation and persevered for 9 weeks. The stress stimulated parameter was: axial stress, 1Hz, 200N, 20min every time, 2 times every day, the interval time was 8h. At the first day and the follow-up time was 4,6 and 9 weeks after the operation, radiographs were taken for each tibia. The animals were all killed 9 weeks after the surgery, histological, image and biomechanics analysis were done to obtain the investigation barometer which contained: the grey value in the fracture site, the axial stiffness ,the bending static rigidity and the torsional stiffness of the callus, the level of maturity of the callus.Results:All the operative incision of the animals animals had healed, and no infection had been seen.X-ray examination: the first 4 weeks note: the osteotomy gap of experimental group wsa a little fuzzy, we could see more callus than the control group, a clear gap osteotomy and less external callus in the control group; the fracture lines had both still existed. The first 6 weeks note: the experimental group had dense callus, the fracture line was fuzzy, and the osteotomy gap nearly disappeared; the control group fracture callus less than the experimental group, but had dense callus, the fracture line was fuzzy, osteotomy gap was still obvious. The ninth week note: the callus of the experimental group was more compact, the fracture line nearly disappeared, part of the canal reformed; the control group had more dense fracture callus, the fracture line was fuzzy. Dispalcement was seen in 2 animals of the experimental group and 1of the control group, screw extration appeared in 1animals in the both groups, when taking the X-ray image. General examination of callus: In the experimental group, the callus was hard,larger in quantity, the inner and outside callus nearly connected, and the canal had been a marked reperfusion; the control group, callus was still soft, less in quantity, part of the internal and external callus connected, the canal had not yet completely re-passed.Histological examination of callus: Compared with the control groups,the experimental groups got more collagen and callus formed, bone trabeculae were thicker, lamellar bone was more regular at 9 weeks.Biomechanics test: The biomechanical analysis revealed that the mechanical characteristics contain the stiffness to resist axial compress,bend and tear of experimental groups were superior to the control groups at 9 weeks.Conclusion: Fracture healing of the goats, tibia shaft should be promoted significantly by the rap-style bone stress stimulator, and the steady basis for the next clinical application could be provided by this study.