The Experimental Study Of Boiled Autogenous Bone Graft

Objective: Segmental mandibular bone defection due to a resection of tumour can not only lead to maxillofacial deformity but also reduce the buccal function of the patient badly. How to restore the mandibular defection was one of the important problems at present. Because of the shortages of autogenous bone graft, some one brought forward the method of boiled autogenous bone graft and got a certain clinical effect. Up to now, there has been little study on boiled autogenous bone graft, especially in the manner of healing and the biologic reaction following boiled autogenous bone graft. The reports about the biomechanical changes of the bone during the process of healing were difficultly found. The purpose of this study was to offer an experimental support on boiled autogenous bone graft through analyzing and evalucating the substituting process and effect of boiled bone, in which changes on morphology and biomechanical during the healing process of the boiled bone, were used as the mainly observed subjects.Methods: Thirty-six adult New Zealand Rabbits were used as study objects, the tibia was chose as graft place, freshautogenous bone graft was used as control. To evaluate the healing process and the healing effect, we observed the histology changes of grafted bone dynamically by microscope at 2 4 6 8 10 12 weeks respectively. And by scanning electricmicroscopy(SEM) at 12 weeks. To analyze the biomechanical changes, we examined maximum bending strength of the tibia at 4 and 12 weeks separately, and the strength of the boiled bone side was compared with the strength of fresh bone side at the same time together with the strength of the bone before and after operation.Results: ㎝orphologic comparison test: The wounds of the animals were up to heal of stage I, and no infection was happened. When sacrifice, we can see that the boiled bone was not joined with the tibia tightly at 2 weeks after operation; at 4 weeks, the grafted bone was covered by thick callus, and it joined with tibia by fibrous callus on the transect; at 6 weeks, the boiled bone was united with tibia ostealy; the boiled bone inosculate with tibia at 8 weeks. The fresh bone was joined with the tibia tightly at 2 weeks, ostealy united with tibia at 4 weeks, and we can not tell its place at 6 weeks. In histological observation at 2 weeks the boiled autogenous bone grafted, we can find some fibre and a little new bone in the clearance and some lymph cells in the tissue around the grafted bone. At 4 weeks, the boiled bone was axenic defunct, covered with fibrous callus, a little cartilaginous callus and osteal callus with some lymph cellscan be seen aroundly. At 6 weeks, the boiled bone was covered by a lot of osteal callus, and was absorbed into little pieces, mixing in the new bone. A little dead bone still can be seen at 8 weeks. At 10 weeks, the boiled bone was almost replaced by new bone, and the structure of new bone was disorganized. The boiled bone was replaced by new bone completely, but there were still some chips of dead bone in it at 12 weeks. At 2 weeks after fresh autogenous bone grafted, there was some new callus in bone defection. The grafted bone was covered by osteal callus without dead bone formed at 4 weeks. At 6 weeks, disorganized new bone was found in the defection. Grafted bone was replaced by adult osteal tissue, and combined with tibia completely at 10 weeks. At 12 weeks, the substitution was finished. Under the scanning electricmicroscopy(SEM) we can see that new bone in boiled bone was immature, while there were adult Haversion systems and osteocytes in the fresh bone. (2) Mechanical strength comparison test: The maximum bending strength of each group: the control group37.23+2.27kg; the bone defect control group25.43 +1.97kg; in the 4 week text group, the boiled bone side 27.40+0.95kg, the fresh bone side 30.45 + 0.96kg; in the 12 week text group, the boiled bone side 36.79 +3.57kg, the fresh bone side 36.24 + 1.29kg. At 4 weeks, the mechancal strength of boiled bone side was lower than the fresh bone side (P<0.