Biomechanical and Mechanobiological Modelling of Functionally Graded Scaffolds for Large Bone Defects

Abstract

Critical sized bone defects remain a major clinical challenge, requiring scaffolds that combine mechanical stability with regenerative capacity. Functionally graded (FG) scaffolds, inspired by the graded architecture of native bone, offer a promising solution by spatially varying porosity to optimise both load transfer and tissue ingrowth. Here, we present an integrated finite element agent based modelling (FEA ABM) framework to simultaneously evaluate the biomechanics and regenerative potential of FG scaffolds under physiologically relevant conditions. Cylindrical scaffolds with axial or radial pore size gradients were compared with uniform controls. The finite element model incorporated poroelastic tissue mechanics and gait related loading to compute local shear strain and fluid velocity, which guided cellular behaviours in the agent based model, including progenitor migration, proliferation, differentiation, and apoptosis. Simulations over 150 days revealed that axial gradients with larger pores at the host bone interface promoted greater bone ingrowth, while radial gradients with denser peripheral struts substantially reduced peak von Mises stresses. These findings highlight a fundamental design trade off between maximising regenerative performance and enhancing structural competence. The coupled FEA ABM framework establishes a mechanistic platform for the rational design of next-generation FG scaffolds, offering a pathway toward preclinical optimisation of implants tailored to defect location and loading environment.