| objective: To explore the correlation between different stress sti- mulus and dog tibial fracture healing. Melthods: Using the same healthy mature male dogs 27,Kg weight(15-18). All samples underwent x-rays of extremities inspection confirmed that the limbs of the dogs were no malforma- tions and fracture. A mid-diaphyseal osteotomy is distracted to form a 3-mm gap of the left tibia and stabilized with a unilateral external fixator to all dogs with general anaesthesia and aseptic conditions. All dogs were randomly divid- ed into three groups based on different stress condition.Low-stress group(group A,n=9): strict immobilization to left knee with a cast that lead to no load bearing on left limb. Medium-stress group(group B n=9): no limb immobilization. High-stress group(group C n=9): immobilized right forelimb carpometacarpal joint with a cast to enhance the stress stimulus of the left hindlimbs in activities. All animals are strictly immobilized for 2 weeks postoperatively, 2 weeks later start daily activities for half an hour per-day. 2、6、10 weeks after the operation, each experimental animals, tibia take AP X-ray to observe and calculate the IOD values of callus by Image- Pro Plus 6.0 software. Ten weeks after operation kill all experimental animals, and take the bilateral tibias completely from the dogs to observe, using GE Prodigy double-energy X-ray bone densitometry machine to measure bone mineral density of the bilateral tibia callus at the same parts surrounding the fracture site. Then using the specimen to make callus tissues biopsies, which will be stained with HE and Masson., then obverse the biopsieses under Optical microscope. Results:1. All the operative incision of the animals are Primary healing, and no infection occurred.2. X-ray observation: Two weeks after the operation x-ray notes: Fracture lines were bright and clear, on the contrary the margin of fracture lines were slightly fuzzy. The gap after osteotomy was clear, and no obvious shift occurred. Six weeks after the operation X-rar notes: The group B and group C demonstrate more callus than the group A. And the gap after osteotomy of group B is most fuzzy in the all groups. Ten weeks after the operation X-ray notes: The Group A formate more callus than before, and the fracture lines blurred, but did not disappear. The callus of the group B was more compact, the fracture line nearly disappeared, part of the canal reformed, and the trabeculae of bone arrange regularly. The callus area of group C is biggest, but less dense. The bone trabeculae arranged irregularly, and we can find bone sclerosis around the gap.3. IOD values measured:The callus IOD values of the three groups were no statistical difference 2 weeks after the surgery; At 6 weeks the callus IOD value of group A and group B is higher than the callus IOD values of group C, and this is statistically significant. And the IOD values of callus is no statistically difference between group A and group B; At 10 weeks, the callus IOD values of group C is lower than the callus IOD values of group B, which is statistically significant. And the callus IOD value of group B is higher than the callus IOD value of group A, which is no statistically significant.4. General examination of callus: The callus amount of group A is less than the other groups,and its quality of material is solid,the surface of callus is smooth;The group B generates many dense calluses,and its quality of material is solid,the surface of callus is smooth too;On the contrary, the group C generate many loose calluses and its texture is crunchy, the surface of callus has many pores5. BMD measurement results:Three groups of BMD compared after 10 weeks, there are significant differences. After 10 weeks the BMD of group B is higher than group C, which is statistically significant. By the contrast, the BMD of A and B was no significant difference.6. Histological examination of callus: The number of collagen and bone callus formation in Group A are less than the number of group B, and its maturity are poor compared with the group B. The group C of a large number of callus formation, see many collagen and fibrous connective tissue mixed together, bone trabecular disordered arrangement; Compared with group A and group C, Group B showed more collagen and callus formation, and the trabecular of bone arrangement more regular. Conclusion:1. In the healing process of dog tibial fracture, appropriate weight can obviously promote the callus formation of quantity and quality2. Too high or too low weight are not very good to promote the healing of dog tibial fracture Too high stimulus may be inhibition of the bone callus remodel and mature, which is not conducive to bone healing.3. Under the condition of natural stress stimulus can promote healing of dog tibial fracture, which may be an appropriate stimulus to tibial fracture... |
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