Magnesium Alloys for Bone-Tendon Interface Regeneration: Biological Mechanisms, Alloying Strategies, and Self-Healing Coatings

Bone-tendon interface (BTI) injuries remain a major clinical challenge because current fixation materials often fail to achieve synchronized mechanical support and biological regeneration, resulting in fibrovascular scar formation and high rerupture rates. Biodegradable magnesium (Mg) alloys have emerged as promising candidates for BTI repair owing to their bone-matched elastic modulus, favorable biodegradability, and the multifunctional biological activities of released magnesium ions. In this review, we systematically summarize the stage-specific healing process of the BTI and integrate current evidence regarding the biological functions of Mg ions throughout inflammation, repair, and remodeling. We highlight how Mg ions regulate macrophage polarization, promote osteogenesis, angiogenesis, fibrocartilage regeneration, and biomechanical adaptation through coordinated modulation of multiple signaling pathways. We further discuss the major barriers limiting clinical translation, including rapid degradation, insufficient mechanical durability, uncontrolled corrosion, and degradation-associated microenvironmental changes. Recent advances in alloying strategies, surface engineering, and intelligent self-healing coatings are comprehensively evaluated, with particular emphasis on their synergistic roles in balancing mechanical stability, corrosion resistance, and biological functionality. Rather than considering alloy composition and coating design as independent optimization approaches, this review proposes a stage-oriented design framework in which degradation behavior, ion release, and interfacial bioactivity are coordinated with the dynamic healing requirements of the BTI. This comprehensive strategy offers new insights into the rational design of next-generation biodegradable magnesium implants, aiming to provide a framework for achieving programmable degradation, precise tissue regeneration, and successful clinical translation in BTI repair, while also offering new perspectives for future researchers.