Insights into biodegradable Mn-incorporated Fe-based scaffolds in orthopedics: bridging manufacturing techniques, physicomechanical properties, and multifunctional bioapplications

Biodegradable metals (BMs) have shown significant potential for applications in the field of orthopedic implants. These materials gradually degrade after implantation, eventually disappear without residue, provide necessary mechanical support during degradation, and closely integrate with bone tissues. Fe-based BMs are particularly notable for their good mechanical properties and biocompatibility. However, their slow degradation rate is a limitation. The emergence of Mn-incorporated Fe-based alloys (Fe-Mn alloys) offers the possibilities for addressing issues of slow degradation rate and incompatibility of magnetic resonance imaging (MRI) for Fe alloys. This review summarizes the advantages of Fe-Mn alloys as orthopedic implants, and the cutting-edge advances in degradation, mechanical and magnetic properties, and osteogenic performance. The cytotoxicity issue is addressed for the porous structured Fe-Mn alloys caused by the enrichment of manganese ions, and thus the main challenge and the development are involved for the Fe-Mn alloys to achieve a balance among biocompatibility, structure, and degradation rate. Also the perspectives are proposed for Fe-Mn alloys as orthopedic implants.