How does mechanical stimulus affect the coupling process of the scaffold degradation and bone formation: An in silico approach

Background: Implantation of biodegradable bone scaffold is regarded as a promising way to repair bone defects, and the coupling process of scaffold degradation and bone formation is influenced by the physical-exercise-induced mechanical stimulus. Methods: The scaffold degradation was modeled by a mechanical-stress-regulated degradation algorithm, and the bone formation was modeled by a strain-energy-density-based formation algorithm. Then, the two models were coupled together by considering the transformation of three material states. Employing the finite element method, the effect of the mechanical stimulus represented by exercise duration (ED) and exercise intensity (EI) on the coupling scaffold degradation and bone formation was numerically studied. Results: Both the final and minimum bone volume fraction and Young's modulus of the coupling scaffold-bone system were generally increased with improved EDs and EIs. The bone volume fractions of the formed bone in all cases were comparable to selected natural cancellous bones, but the Young's moduli were greater than the natural cancellous bones. Conclusions: This work sheds light on the regulation of mechanical stimulus on the coupling process of the scaffold degradation and bone formation, and provides a potential in silico way to pre-evaluate the performance of degradable scaffold for bone repair.