A study of micro-arc oxidized Mg-Zn-Ca alloy for craniofacial fracture fixation: A comparison with Ti-6Al-4 V alloy in a minipig model

• Mg-Zn-Ca alloy demonstrates potent pro-osteogenic and pro-angiogenic effects in vitro . • Micro-arc oxidation (MAO) ensures early mechanical stability. • MAO-modified Mg-Zn-Ca alloy demonstrates equivalent healing efficacy to the TC4 gold standard. • MAO-modified Mg-Zn-Ca alloy overcomes stress shielding, enhancing long-term osteointegration. • MAO-modified Mg-Zn-Ca alloy proves to be systemically safe in a large animal model. Magnesium (Mg) alloys are promising biodegradable materials for fracture fixation in non-load-bearing skeletal sites, but their rapid early degradation limits sustained mechanical support. This study developed a screw-plate system made of a novel Mg-Zn-Ca alloy with micro-arc oxidation (MAO) surface modification and evaluated its performance against the clinical control, Ti-6Al-4V (TC4), for craniomaxillofacial fracture fixation in a Yucatan miniature pig model. Multi-scale imaging, histology, biomechanical testing, and systemic biosafety assessments were conducted to investigate fracture healing, implant degradation, and biocompatibility. Quantitative micro-CT analysis revealed no significant differences in maximum gap, bone volume fraction (BV/TV), or bone mineral density (BMD) at fracture sites between the Mg-Zn-Ca and TC4 groups (P > 0.05). The average screw volume retention in three-hole plates was 78.7 %, 58.4 %, and 47.9 % at 1, 3, and 6 months, respectively, and 79.9 %, 57.2 %, and 46.5 % for four-hole plates. Notably, the BV/TV and BMD of bone surrounding Mg-Zn-Ca screws were significantly higher than those around TC4 screws (P < 0.05). Overall, the MAO-modified Mg-Zn-Ca alloy provided healing outcomes comparable to TC4 while offering controlled degradation, favorable biosafety, and improved long-term osseointegration, highlighting its clinical potential for craniomaxillofacial applications.