| Objective: To observe the local response to the NiTi alloy implanted in rabbits and the repairness of bone defect , to evaluate the histocompatibility of the NiTi shape memory alloy with bone. Methods: The NiTi shape memory alloys were made a cylindroid body with 0.5mm in diameter and 4mm in length. The 12 rabbits were divided randomly into experimental group and control group, 6 rabbits in each group. The NiTi shape memory alloys were implanted respectively into the distal aspect of left femur of 6 rabbits in the experimental group, while holes without alloy implantation were performed in the control group. All of the animals were killed respectively by the 4th, 8th, 16th week after implantation, and 2 rabbits in every group were killed every time. After removed, prepared by fixation and staining, the tissue samples were analyzed by the light and the electron microscopy to evaluate the histocompatibility of the material. The HE staining sections were analyzed by computer multi-function image analysis system in the experimental group and the control group at the 4th, 8th, 16th week postoperation. Results:The X-ray films showed that the NiTi shape memory alloy implanted in rabbits fixed well with bone and no displacement; no lower density shadows were found in alloy-bone interface area.Under the light microscope, at the 4th week after implantation, the periosteal proliferation was found in the control group and the experimental group, and it was more serious in the experimental group, there were no inflammation reaction in the two groups. The damaged trabeculae and newborn capillaries infiltration were found around theimplanted area, a layer of osteoblasts lined in the newborn trabeculae. At 8th week after implantation, the periosteal reactions were disappeared in the control group and the experimental group, the trabeculae in the control group consisted of a varying number of parallel-packed lamellae and osteocytes, while the trabeculae were disorder, the lacunae and osteocytes were found in the newborn osteoid with a layer of osteoblasts and capillaries in the experimental group. At 16th week after implantation, the regular bone lamellae and mature newborn osseous tissue were found in the control group, while a mass of osteoid, regular bone lamellae and newborn osseous tissue in the experimental group. The HE staining sections were analyzed by computer multi-function image analysis system, the results showed that the area of newly formed osseous tissue in measure area were gradually increased with time after operation. P>0.05, the statistics results showed no statistical significancy between the two groups. In the Masson staining sections, the collageous fibers appeared red with green in the control group and the experimental group matrix, the red-stained area gradually increased with time after operation, the red-stained area in the control group was more than the experimental group at the 4th, 8th, 16th week.Under the transmission electron microscope, at 4th week after implantation, lots of osteoblasts were found around implant area in the control group and experimental group. The osteoblasts arranged as an layer, were cuboidal in shape, with short and slender processes, well-developed rough endoplasmic reticula, mitochondria and a prominent Golgi apparatus. The degenerate and necrosis osteocytes with fragmentative nuclei and vacuolated cytoplasm were found around the implant area by the operative damage. The osteocytes were lysis and atrophy, whose lacunae compartment enlarged around the implant areaalso by the operative damage. The osteoprogenitor were arranged as an layer in endosteum around the implant area, the cells were rather small and spindle-shaped, with short microvilli. The nuclei were ovoid with homogeneous chromatin. In the cytoplasm, rough endoplasmic reticula, glycogen granules, mitochondria and a prominent Golgi apparatus were found. At 8th week after implantation, lots of osteoblasts appeared around trabeculae, newborn lamellae were regular. At 16th week after implant...
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