Bioabsorbable & Magnesium (Biodegradable Metal) Implants

Magnesium-based biodegradable implants are designed to provide initial fixation and then resorb, so they combine some of the strength of a metal with biodegradation, and they differ from the bioabsorbable polymers such as PLLA. Their advantages over titanium begin with stiffness: magnesium's elastic modulus is much closer to that of bone, which reduces stress shielding, whereas titanium and steel are far stiffer. Magnesium is biocompatible and osteoconductive, and has favourable biological effects - it is pro-osteogenic, anti-osteoclastic and anti-inflammatory, activating signalling pathways in mesenchymal stem cells and enhancing bone regeneration. Because it resorbs, there is no need for a removal operation, and it produces less imaging artefact than permanent metals. The main limitation is controlling the corrosion or degradation rate: magnesium can degrade too quickly, losing mechanical strength before the fracture has united, and its degradation is variable and site-dependent; in addition, corrosion liberates hydrogen gas, which can form gas pockets. These engineering challenges, managed by alloying and coatings, along with the regulatory complexity of a device that is also a biological agent, have slowed widespread adoption. A practical clinical point is that the expected degradation produces imaging findings - progressive lucency, resorption and gas - that can be mistaken for infection or loosening, so it is important to recognise the normal evolution and correlate with the clinical picture. In current practice, the MAGNEZIX magnesium compression screw was the first approved for humans and is used mainly in foot and ankle and small-fragment fixation, with more approvals in Europe and Asia than the USA.