| Objective:Establish rabbit vertebral burst fracture by surgery and Observe the histomorphologic changes and study the dynamic expression of TGF-β and BMP-2in bone tissue around bone cement after augmentation of rabbit vertebral fracture with PMMA.Methods:New Zealand white rabbits were established vertebral fracture through anterior retroperitoneal approach by surgery.25rabbits were successfully established vertebral burst facture and then divided into two groups:Experimental group and control group and each group had15rabbits and10rabbits respectively. Augmented vertebral fractures with PMMA in experimental group and gave no treatment to control group. Before the rabbit death, radiological study and CT of the pieces were obtained to evaluate for leakage, cement diffusion and fracture healing. The animals of the two groups were killed at1day,3days,7days,2weeks and4weeks after intervention. Obtained the pathological sections of the experimental vertebrae to observed histomorphological changes and detect, with immunohistochemical methods, TGF-(3and BMP-2dynamic expression levels of tissues surrounding PMMA.Result: There was one intraoperative death in the process of establishing fracture model, and another death at1st day of postoperation. Vertebral fracture of experimental group were injected PMMA about0.1-0.3ml.No obvious complications were observed in each rabbit before its death. Postoperative CT confirmed the presence of rabbit vertebral fractures, but the morphology of fracture was different.The defluvium defluxion, loosening were not observed from postoperative X-ray and CT, and the volume of bone cement were not significant variation.HE staining, the PMMA group existed slight bone necrosis at1day,3days,7days, but no obvious bone necrotic observed2-4weeks late, but the control group had such things. At24hour, inflammatory cell significantly aggregate. At3day, it’s reach to the peak. At7day, it’s decreased gradually. And at the4week, it’s almost no inflammatory cell insight. At the3day, there were mesenchymal cell aggregation in bone tissue. At the7day, there were some macrophages surrounding bone tissue, suggesting presence of a foreign body reaction. At the2week, there were a small number of fibroblast fibers around the bone cement in the experimental group and a slight increased aggregation of osteoblasts over the previous. At the4week, a mount of fibrous tissue and a group of chondrocytes was visible, and Cartilage differentiated into new bone and callus. Compared with normal bone tissue, after1d, the TGF-β and BMP-2expression had no significant increase in both group (P>0.05).At the3day, the TGF-β expression of control group increased significantly, the experimental group had no significant change, the TGF-β expression of two groups had statistical difference (P<0.05). At the7day, the TGF-P and BMP-2expression of control group increased significantly, the experimental group had no significant change of all, but the TGF-β and BMP-2expression of two groups had statistical difference (P<0.05).At the2week, the TGF-β and BMP-2expression continual increased in both group, but the control group was more significant than the experimental group, and the TGF-P and BMP-2expression of two groups had statistical difference (P<0.05). At the4week, the TGF-β and BMP-2expression reached each peak. The peak of experimental group was slightly lower than the control group,but there was no statistical difference (P>0.05).Conclusion:PMMA can cause mild inflammation and bone necrosis, but no sustained inflammatory response and bone necrosis, indicating that the exothermic reaction and toxicity of PMMA have no continual adverse effect to the tissue surrounding bone cement. During the fracture healing, the peak of TGF-P and BMP-2expression arose in both group, but appeared to be delayed in experimental group. Suggesting PMMA may affect GFs synthesis and release, but ultimately does not affect fracture healing. |
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