Production Of A Closed Femur Fracture Model In Rats Accompanied With Ionizing Radiation And Research On The Relationship Between Radiation Doses And Fracture Healing

Objective the goal of this study was to develop a closed femoral fracture model of rats with radiation of different doses and to analyze the relationship between radiation doses and fracture healing. Methods 150 male Sprague-Dawley rats used in this study were divided into 5 groups randomly. They are 1 simple fracture group (SG), 1 control group (CG), 3 experimental groups irradiated with 1Gy X-ray(EG1), 3Gy X-ray(EG3) and 5Gy X-ray(EG5). Each group contained 30 rats. The experimental groups of rats were irradiated with different doses of X-ray before medullary cavity internal fixation with Kirschner wires and middle femur fracture were performed; while the simple fracture group was intervened with the same surgery treatment without irradiation. The rats were killed at preset time intervals of 2, 4, 8 and 12 weeks postoperatively and heart chamber blood samples were harvested. Alkaline phosphatase(ALP) activity of the samples was measured. Fracture healing was assessed by radiographs at each time point. Results Of the 150 rats used in this study, 135 rats survived the experiment. Only 7 rats were excluded due to serious smashing fracture of the 120 intervened rats , similar seriousness degrees of traverse fractures at the middle of right femur occurred in the other 113 rats as designed in advance. No Kirschner wires angulation was observed. The reproducible ratio was 94%. After 2 weeks, significant difference of ALP activity was detected in SG and EG1 compared to CG.; no significant difference of ALP activity was detected in EG3 and EG5 compared to CG. After 4 weeks, in contrast with CG, the ALP activity of EG1 increased significantly, while the ALP activity of the other groups decreased reversely. After 8 weeks, in contrast with CG, the ALP activity of SG, EG3, EG5 decreased significantly; while there were no statistically significant differences between EG1 and CG. After 12 weeks, the ALP activity of SG, EG1, EG3 and EG5 decreased significantly compare to CG (P<0.001). But no significant differences were detected among the groups with surgery treatment. Radiography: Fracture healing in EG1 was better than that in CG, EG3 and EG5; while fracture healing in EG5 was the worst. Conclusions⑴The designed fracture model in the rats simulates the progress of fractures in nuclear accidents successfully. The achievement ratio of this kind of model (94%), which can be used in the study of fractures accompanied with radiation lesion, is similar with those in foreign literatures.⑵1Gy irradiation can stimulate the activity of osteoblasts to accelerate the progress of fracture healing; while 5Gy irradiation retards the progress.⑶The range of ALP activity can manifest the activity of osteoblasts directly and can be used as the sign of the capacity of bone formation as well as the capacity of bone tissue reparation. Accordingly, ALP activity can be used in the research of radiation bone lesion.