Experimental Study On Bone Formation Mechanisms Of Hyperthermic Aseptic Water Bath Devitalized Bone In Bone Defect Reconstruction Of Tumor

Objective: To investigate the bone formation mechanisms of tumor bone devitalized by hyperthermic aseptic water bath in reconstruction of bone defect in limb salvage treatment.Material and Methods: 32 New Zealand Rabbits were randomly grouped into 4 groups with 8 ones for each group;an absolutely periosteum—osseous defect model was eatablished by truncation of a 1. 5 cm segment of bilateral middle part of tibia. The experiment segment was devitalized by hyperthermic aseptic water bath (60°C for 30 mins) while the opposite segment of the same Rabbit was marinated by NS. Both were re—planted with internal fixation. The indexes observed included: mac-rogrophy, X — ray, histological observation, tetracycline fluorescent marker, SPECT bone scan, quantitative analysis of devitalized bone, electron microscope and EDAX.Results: 8 weeks after the reconstruction, osseous healing was observed in the interface of devitalized bone and host bone. New bone formation could be clearly seen in 12 weeks. At 24 weeks, the devitalized bone and host bone were almost the same morphologically and consecutive medullary canal could be seen. Histologically;Distribute of Trabecular fibrous bone with a lot of infantile osteoblasts could be seen in deep part of the devitalized bone in 8 weeks, after 12 weeks, the experiment bonesegment had more intensive appearance and some longitudinally arranged Havo's canal could be seen microscopically. Besides these changes, the control group also had clear medullary canal. After 24 weeks, ratio of fibrous and laminar bone increased significantly, they aggregated in the interface of two ends of devitalized bone and host bone, and the medullary canal could be seen in the new—born bone. Tetracy-cline fluorescent marker, SPECT bone scan: Time to revascularization was about 8 ~12 weeks, and at week 24, the blood supply of devitalized bone is close to normal. Quantitative analysis of devitalized bone: The area percentage of new bone was increasing with the time, but at 4, 8 and 12 weeks, markedly difference could be seen in devitalized bone and control bone segment. The Calcium/Phosphorous ratio in devitalized bone was similar to that of host bone.Conclusions: The bone formation period is longer in devitalized bone than that in fresh bone, but a consecutive observation detected the two groups have almost the same results in 24 weeks and same bone formation processes with satisfactory restoration. The mechanisms of bone formation include bone induction, bone conduction, bone regeneration, and known neurological factor and unknown factors. The following 3 conditions should be met for bone formation in devitalized bone-. ? existence of osteoblasts, ? sufficient blood supply, ?appropriate inductive factors such as BMP in the matrix. Devitalization of the tumor bone with hyperthermic a-septic water bath in reconstruction of bone defect is rational and cost —effective in limb salvage treatment.