A staggered computational framework for the degradation and fatigue life assessment of bioabsorbable bone implants

This paper presents a computational approach for simulating the degradation dynamics of bioabsorbable orthopedic screws and evaluating the evolution of their fatigue resistance over time. A thermodynamically consistent phase-field model, numerically implemented through a custom finite element formulation, is developed to describe the degradation process of Mg-based screws immersed in a liquid phase mimicking the bone biological environment. The numerical results, validated against in vitro experimental data, demonstrate the accuracy and flexibility of the implemented formulation. The degradation model is complemented by a weakly-coupled fatigue analysis performed at selected time instants during the simulated corrosion process. As a result, a measure of fatigue resistance and mechanical failure risk is provided as a function of the implant degradation evolution. An application to a representative case study highlights the potential of the proposed computational framework to be a first step towards more advanced formulations aimed at providing clinical decision-making insight for the optimization of bone implant performance and therefore for personalized therapeutic strategies.