Resorbable Metallic Implant: Findings from an Animal Model

Resorbable metallic implant of magnesium and its alloys had been studied since the 1900s. However, the excessive gas production resulted in its unpopularity after CoCr alloys and stainless steel were developed. With the advancement of alloying technologies, its use as a resorbable implant has re-emerged recently. Foreign researchers focused on the use of AZ-series and magnesium-rare earth metal alloys. However, the corrosion property of AZ-series alloys is unsatisfactory, and the effect of rare-earth metals on human is poorly studied. Therefore, we have investigated on the feasibility of using commercially available AM-series magnesium alloys. Previous researchers avoided this alloy series presumably because of the potential health effect of manganese, however our toxicological risk assessment revealed that the exposure level would be lower than the NOAEL (No Observable Adverse Effect Level), thus it is unlikely to cause any observable health effect on healthy individuals. Subcutaneous implantation of AM-series magnesium alloys into a mouse model for six months confirmed that, while all alloys tested showed slow corrosion and no observable in vivo toxicity, pitting corrosion did not occur for AM-series alloys but was frequent for AZ91D. This suggests that AM-series magnesium alloys are good candidates of resorbable metallic implants.