Abstract: Objective To investigate the degradation mechanism at the bone-implant interface of degrading magnesium alloys in bone and to determine their effect on the surrounding bone. Methods Sample rods of magnesium alloys were implanted intramedullary into the femora of rats received a subcutaneous injection of gentamycin as an antibiotic prophylaxis and weekly subcutaneous injections of calcein green. After 6, 9, 15, 26 and 80 weeks, decalcified sections were maken for histomorphologic analysis. The bone-implant interface was characterized in calcified sections by optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Results The metallic implants made of magnesium alloys were degraded entirly in vivo with the elapse of time.The corrosion layer was indirectly contact with the surrounding bone through basement membrane containing C, N and O elements. Besides,the results further showed an increased bone mass around the magnesium rods, while no bone was induced in the surrounding soft tissue.Conclusion The results of this study suggest that high magnesium ion concentration with Zn and Mn could lead to bone cell activation, and might be a suitable material for bone-implanting.

Key words: Magnesium alloy, Degradation, Basement membrane, Bone, Energy dispersive spectroscopy, Rat