Update on the research and development of magnesium-based biodegradable implants and their clinical translation in orthopaedics

Biodegradable magnesium (Mg) or its alloys are desirable materials for development into new-generation internal fixation devices or implants with high biocompatibility, adequate mechanical modulus, and osteopromotive properties, which may overcome some of the drawbacks of the existing permanent orthopaedic implants with regard to stress-shielding of bone and beam-hardening effects on radiographic images. This review summarises the current research status of Mg-based orthopaedic implants in animals and clinical trials. First, detailed information of animal studies including bone fracture repair and anterior cruciate ligament reconstruction with the use of Mg-based orthopaedic devices is introduced. Second, the repair mechanisms of the Mg-based orthopaedic implants are also reviewed. Afterwards, reports of recent clinical cases treated using Mg-based implants in orthopaedics are summarised. Finally, the challenges and the strategies of the use of Mg-based orthopaedic implants are discussed. Taken together, the collected efforts in basic research, translational work, and clinical applications of Mg-based orthopaedic implants over the last decades greatly contribute to the development of a new generation of biodegradable metals used for the design of innovative implants for better treatment of orthopaedic conditions in patients with challenging skeletal disorders or injuries.