| Objective: To establish an animal model of bone graft; to simulate postoperative radiotherapy with surgical area as radiation target region; to observe the bone healing condition after irradiation; to try to analyze information and data in the graft bone healing process after radiotherapy, so as to provide scientific basis for clinics to better carry out postoperative radiotherapy and to reduce the incidence of complications.Methods: 36 healthy and mature New Zealand white rabbits were selected with the weight of 2 to 2.5kg and age of 12 to 15 months. A fan-shaped bone fragment with a radius of about 2 cm was cut with the left anterior superior iliac spine as a starting point through rotating inwards for 30 degrees, and the same operation was carried out on the right side.The obtained bone fragment was cross-transplanted into the contralateral postoperative bone defect zone, fixed and stitched. The left side surgery zones were taken as experimental observation regions, the rabbits were randomly divided into two groups: an experimental group and a control group with 18 rabbits in each group, 15Gy radiotherapy was given on the left side operation zones of the experimental group in one time in the second week after the surgery respectively, and the control group did not accept the operation. Six rabbits were randomly sampled in the experimental group and control group respectively in the 4th week, 8th week and 16th week after surgery, X ray detection was given to total 12 rabbits in one batch, then, experimental animals accepted X-ray examination were killed, and bone density, bio-mechanics, gross and histological comparison were respectively carried out.Results:1 X-ray observation: in the 4th week after surgery, X-ray images in the experimental group showed blurred edges, and connections were point-like callus, showed low-density, and partially showed transmission shadow. X-ray images of the control group showed unclear edges, connections were linear callus, and the surroundings had low-density shadow.In the 8th week after surgery, X-ray images of experimental animals in experimental group showed not clear enough edge, connections had the linear callus, and surroundings had low-density shadow, 2 images did not generate significant linear callus. New bone specimens of the control group had little vague and rough edges, and had a large number of callus formation, wherein five specimens showed worm-eaten-like changes in the connection.In the 16th week, X-ray images of experimental animals in the two groups showed clear edge, and did not have prominent boundaries with remote end bone tissue, and the two groups have no significant difference.2 Dual-energy X-ray bone density test results:bone density test result variance analysis showed that the bone density value of the experimental group in the 4th, 8th, 16th week after surgery was respectively 0.265±0.08,0.283±0.09,0.295±0.04, the data of the control group data for each time period was 0.287±0.04,0.296±0.06,0.301±0.05. The bone density value of the experimental group and control group had differences, P<0.05, and the difference had statistical significance.3 Bio-mechanics Observation Result:the healing surface of the bone specimen accepted shear stress test, the formula wasτ= Q / F. It was obtained that the shear strength standard deviation of the experimental group in the 4th week was 0.8462±0.235, the control group was 1.1083±0.00385, P <0.05, the difference between the two had statistical significance. The experimental group was 1.651±0.350 and the control group was 1.8403±0.398 in the 8th week, P <0.05, and the difference had statistical significance. The experimental group was 1.9434±0.0158 and the control group was 1.9985±0.202 in the 16th week, P> 0.05. 4. Gross and Histological Observation Results 4.1 Gross Observation Result:fibrous capsules were covered on the surface of transplanted bone specimens in the experimental group in the 4th week after surgery, and the surface of specimens in the control group was covered by a small amount of sclerotin.In the 8th week after surgery, it can be seen that 4 graft bone samples in experimental group were covered by a little sclerotin and the other two sample surfaces were covered by fibrous capsule, and no prominent sclerotin can be seen, the surfaces of graft bone specimen in the control group were covered by more sclerotin.In the 16th week after surgery, a layer of cortical bone was covered on the surface of graft bone of the experimental group and control group, and the appearance difference between the two groups was not great.4.2 Histological Observation Result:In the 4th and 8th week, the percentage results of mature bone cells in the experimental group were 42.46±8.37 and 50.25±6.63, the results of the control group were 50.35±5.79 and 52.57±4.47, the mature bone percentage difference between the experimental group and control group was significant, P<0.05, the difference had statistical significance; the value of experimental group in the 8th week was similar to that of the control group in the 4th week. In the 16th week, the result of the experimental group was 53.65±1.41, the result of the control group was 54.87±1.08, the difference was not significant, P> 0.05, the difference did not have statistical significance.Conclusion:1 Postoperative radiotherapy with conventional-dose has inhibition effect on different degrees in the early and middle stage of graft bone healing, but does not completely prevent bone healing, and specimens of the two groups in the experimental latter period did not reach the bone healing.2 Bone graft postoperative radiotherapy is feasible. Under the condition of standard-dose, the draft bone healing is lagging behind in the early and middle period after surgery, and the situation should be focused in clinical treatment.3 Radiotherapy is taken an important means of bone cancer treatment, and this experiment can provide reference for a part of clinical research. |
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