Hard–Soft Dual-State Coatings Regulate Degradation Rate and Biocompatibility of Orthopedic Magnesium Implants

The biomechanical similarity of magnesium to cortical bone, along with its biocompatibility and biodegradability, makes it promising for orthopedic implants. However, rapid degradation compromises the structural integrity and fixation, causing failure. To address this issue, we developed a hard-soft dual-state coating to regulate degradation and improve performance. A dense magnesium hydroxide hard coating was formed by sodium hydroxide treatment, and the hydrogel soft coating formed by freeze-drying was 44.5 μm thick. The dual coating significantly improved the corrosion resistance and mechanical properties. Mg-OH-Hy implants exhibited a reduced corrosion rate of 0.61 mm/year (±0.02), an ultimate fracture force of 750 N (±10), and a pullout force of 350 N (±10). Electrochemical testing revealed an E_corr of -1.08 V and an I_corr of 10^-3·8 mA/cm². This dual coating approach improves mechanical stability, controls degradation, and promotes bone integration, providing personalized solutions for diverse clinical applications.