From rapid corrosion to clinical use: coating technologies for magnesium-based orthopedic implants

Abstract

Biodegradable magnesium (Mg) and alloys are widely used for orthopedic fixation due to their bone-like elastic modulus and gradual biodegradation, which can eliminate the need for secondary removal surgery; however, rapid and localized corrosion in physiological environments, initiated at defects and microcracks, leads to premature mechanical failure, hydrogen evolution, and alkaline conditions that disrupt protein adsorption and cell integration during early bone healing, making surface coatings essential for controlling interfacial reactions, regulating material transport, and improving biological compatibility. In this work, a comparative and mechanistic framework is presented to evaluate inorganic (Ca-P and oxide), organic (PCL, PLGA, chitosan, collagen), and hybrid coating systems, where representative studies are critically analyzed in terms of corrosion performance, biological response, and key limitations, thereby enabling the identification of consistent structure–property relationships across different coating strategies. The analysis shows that hybrid and multilayer coatings provide the most balanced performance by combining effective barrier protection with controlled Mg²⁺ release and enhanced bioactivity, whereas clinical translation remains limited due to insufficient long-term adhesion under physiological loading, lack of scalable fabrication methods, and the absence of standardized corrosion–biology evaluation protocols, thereby emphasizing the need for next-generation Mg coatings with multifunctionality, controlled degradation, and improved interfacial stability.