Corrosion-Driven Degradation of Mg WE43 Plates for Mandibular Fracture Fixation: An In-Silico Study

Biodegradable Mg WE43 alloys offer bone-matched stiffness and osteogenic degradation products for mandibular fracture fixation but undergo unpredictable uniform and pitting corrosion that may compromise early stability. Integrating corrosion kinetics into finite element analysis (FEA) could inform implant design and degradation scheduling. To evaluate mechanical stability and degradation of a Mg WE43 mini-plate for mandibular fractures via finite element analysis (FEA), incorporating uniform corrosion and Weibull-distributed pitting corrosion to model stochastic defect formation and growth. A subject-specific mandibular model with a 1 mm angle fracture gap was reconstructed from CT images and combined with detailed SolidWorks designs of a 1 mm-thick WE43 mini-plate and screws. The assembly was discretized with linear tetrahedral elements in ABAQUS/Explicit. A custom VUMAT subroutine implemented continuum damage mechanics-based uniform corrosion and Weibull-distributed pitting corrosion. Boundary conditions fixed the temporal region and applied 150-600 N anterior loads. Validation against experimental mass loss and stress-strain data assessed model accuracy. Over 24 days, simulated corrosion decreased plate stiffness by > 60%, aligning with typical cortical bridging at ~35% residual stiffness. Ultimate tensile strength dropped from 279 to 123 MPa (56% loss) and strain at failure halved. von Mises stress redistribution shifted peak stresses toward corroded fillets, increasing by > 40% under 600 N by day 24. Simulated mass-loss trajectories and stress-strain curves closely matched published experimental benchmarks. The CDM-based FEA framework reliably predicts the time-dependent mechanical degradation of WE43 Mg fixation plates, allowing for the synchronization of implant weakening with bone healing. This predictive tool enables researchers and manufacturers to enhance the implant geometry and corrosion profiles for better safety and effectiveness of biodegradable maxillofacial fixation devices.