The Experimental Study On Revascularization Of Hyperthermic Water Bath Induced Devitalized Bone With Bone Mineral Density And Biomechanical Study

Objective: To explore the bone healing and revascularization process and the mechanism of Hyperthermic water bath induced Devitalized Bone segment by bone mineral density and the change of biomechanical properties. Method: To establish the New Zealand rabbits models of 1.5cm tibia segments. The bone segments of test side were devitalized by Hyperthermic water bath (60 ℃, 30min) and then re-implanted. The contrast side was bathed by nature salt of normal temperature (fresh one) . The specimens were taken for examination of radiography,histomorphology, serum detection, energy dispersion analysis X-Ray (EDAX), bone scintigraphy, scanning electron microscope(SEM), bone mineral density (BMD) detection and biomechanical properties measurement at 4, 8, 12, 24 weeks postoperatively. The results of test side and contrast side were compared on the same condition.Result: The bone mineral density decreased slowly at 0-4 weeks, and obviously at 8 week, the most obviously at the 12 week. AT the 24 week, the bone mineral density of both side all increased but the difference dose exist(p<0.05). The biomechanical properties of contrast side decreased obviously at 12 week, and the test side was lower, and had the tendency of increase at 24 week. It could be observed the accumulated radioisotope reached its peak at 4 week and be stable at 12 week. The histomorphology showed the devitalized bone appeared almost 100% empty lacunae and Haversian Canal broke up in early stage. Osteoblastssecreted osteoid and then calcifed;devitalized bone healed after 24 weeks and collagen fibers arranged coincidence, but the resorption still existed. Maximal breaking load of devitalized bone increased lightly at forth week, then decreased gradually. Breaking load of contrast side was higher than test side(p<0.05).The test side had the evidence of radiographic union at 24 week. Conclusion: bone mineral density and biomechanical properties measurement are good ways to evaluate the clinic healing of devitalized bone. Hyperthermic water bath induced devitalized bone can heal with internal repair but slower than way of the fresh one;the biomechanical strength of devitalized bone decreased gradually and the amelioration will take a long time. The changes of the bone mineral density and biomechanical properties were same with the histomorphologic changes.