Biofunctionalisation of porous additively manufactured magnesium-based alloys for Orthopaedic applications: A review

Magnesium (Mg) alloys have gained significant attention as a desirable choice of biodegradable implant for use in bone repair applications, largely owing to their unique material properties. More recently, Mg and Mg-based alloys have been used as load-bearing metallic scaffolds for bone tissue engineering applications, offering promising opportunities in the field. The mechanical properties and relative density of Mg-based alloys closely approximate those of natural human bone tissue, thereby mitigating the risk of stress-shielding effects. Furthermore, the inherent biodegradability of Mg-based alloys eliminates the necessity for a second surgical procedure for the removal of the implant, a frequent requirement with conventional non-degradable implants. However, a notable challenge remains in managing the high corrosion rate of Mg and Mg-based alloys within physiological environments to ensure that they meet the necessary functional requirements. Consequently, a comprehensive analysis and understanding of the corrosion behaviour of Mg and Mg-based alloys, coupled with optimisation of their surface properties, assume pivotal significance to ensure successful clinical application. The personalized 3D printing of Mg and Mg-based alloy implants represents a paradigm shift, offering a plethora of advantages, foremost among them being the enhancement of the bone healing process facilitated by the degradable porous structure conducive to bone ingrowth. Also, the emergence of surface functionalisation techniques for Mg-based implants amalgamates the mechanical and degradation properties inherent to metals with the enhanced biofunctionality offered by these coatings. This synergy presents a highly promising avenue for using Mg-based implants as temporary orthopaedic and dental solutions. This comprehensive review provides a detailed analysis of recent advancements encompassing alloying elements, additive manufacturing processes, lattice structures and biofunctionalised coatings to tailor the corrosion resistance, mechanical properties and biocompatibility of Mg-based orthopaedic implants.