Biodegradable orthopaedic implants: A systematic review of in vitro and in vivo evaluations of magnesium, iron, and zinc alloys

In the field of orthopaedics, biodegradable metallic implants have attracted substantial interest due to their potential to reduce the need for implant removal surgeries, facilitate the regeneration of native tissue, and reduce the risk of long-term complications. Although numerous literatures have been published that emphasise the successful results of biodegradable metallic implants, none of them have specifically addressed the advantages and disadvantages of the three superior metals: magnesium (Mg), iron (Fe), and zinc (Zn). Furthermore, before being implanted in the human body, these metallic implants must undergo in vitro and in vivo testing to ensure their compatibility. Therefore, this article reviewed the most recent in vitro and in vivo experiments conducted on biodegradable metallic implants, emphasising the degradation behaviour, biocompatibility, loading conditions, boundary conditions, advantages, and disadvantages of the materials. In summary, zinc-based alloys are superior to Mg and Fe in terms of strength and a favourable strength-to-weight ratio, despite the fact that they have demonstrated biocompatibility and mechanical properties that are appropriate for biomedical implants. Nevertheless, in order to guarantee the mechanical properties of materials are reliable, it is necessary to implement an alternative method, such as Computer-Aided Design (CAD) simulation.