Biodegradable Mg–Zn–Mn alloys for orbital bone fixation: Balancing corrosion resistance and mechanical integrity

The clinical application of biodegradable magnesium alloys in orthopedic implants requires a balance between mechanical strength, corrosion resistance, and biocompatibility. This work investigates the effects of Mn addition (0, 0.5, and 1 wt%) on the microstructure, strength, degradation behavior, and biocompatibility of Mg–1Zn alloy for its possible application in orbital bone fixation. Mn addition resulted in significant grain refinement, linked to nucleation induced by coarse second phases and suppression of grain boundary migration by fine precipitates. This grain refinement contributed to a considerable increase in yield strength, from 146 MPa to 225 MPa, with increasing Mn content. Among the tested alloys, 0.5 wt% Mn showed the lowest corrosion rate (0.27 mm/y in vitro). All the tested alloys showed excellent cytocompatibility in vitro. Furthermore, in vivo implantation into rabbit zygomatic bones confirmed that Mg–1Zn-0.5Mn improved effective tissue integration and controlled degradation behavior. This alloy achieved a favorable balance between mechanical performance and biodegradability, with a stable in vivo corrosion rate of 0.34 mm/y during the three-month implantation period. These findings suggest that Mg–1Zn-0.5Mn is a promising material for orbital bone fixation.