Degraded and osteogenic properties of coated magnesium alloy AZ31; an experimental study

Background: Degraded and osteogenic property of coated magnesium alloy was evaluated for the fracture fixation in rabbits. Methods: Magnesium alloy AZ31 with a different coating thickness by microarc oxidation was used, and the bilateral radial fracture model was created by the bite bone clamp. Thirty-six New Zealand white rabbits in weight of 2.5 similar to 3.0 kg were randomly divided into A, B, and C groups at four time points and other 3 rabbits as the control group without magnesium alloy. Coated magnesium alloy AZ31 was implanted on the fracture and fixed with silk thread. Indexes such as general observation, histology, X-ray, hematology, and mechanical properties were observed and detected at 2nd, 4th, 8th, and 12th week after implantation. Results: Fracture in each rabbit was healed at 12th week after implantation. Among the three groups, the best results of general observation, histology, and X-ray appeared in A group without coating. However, A group showed the worst results from the perspective of mechanical properties about tensile strength and flexural strength, which failed to reach that of the natural bone at the 12th week. Comprehensive results displayed that C group with 20-mu m coating was better than others in mechanical properties, while there is no difference between B and C groups in hematology. Conclusions: Degradation rate is inversely proportional to the coating thickness. And magnesium alloy with a 20-mu m coating is more suitable for the fracture fixation.