Enhancing Mechanical Stimuli in Functionally Graded Bone Scaffolds Through Porosity Gradients: A Finite Element Analysis Study

TL;DR

This study uses finite element analysis to show that porosity gradients in functionally graded bone scaffolds improve mechanical stimuli distribution, especially with higher gradient magnitudes and stiffer materials, aiding tissue regeneration.

Contribution

It systematically investigates how porosity gradients, material properties, and fixation rigidity affect mechanical stimuli in FG scaffolds, providing design insights for improved bone regeneration.

Findings

Porosity gradients enhance shear strain near fixation sites.

Higher gradient magnitudes improve mechanical stimuli.

Stiffer materials show more pronounced benefits.

Abstract

Achieving an optimal biomechanical environment within bone scaffolds is critical for promoting tissue regeneration, particularly in load-bearing anatomical sites where rigid fixation can induce stress shielding and compromise healing. Functionally graded (FG) scaffolds, which incorporate controlled variations in porosity or material properties, have attracted significant attention as a strategy to mitigate stress shielding by promoting more favourable load transfer. In this study, the effects of porosity gradient magnitude (i.e., max-to-min ratio of porosity), gradient resolution, scaffold material properties, and fixation plate rigidity on the distribution of mechanical stimuli within FG scaffolds were systematically investigated. Finite element analyses (FEA) were conducted on a femoral segmental defect model stabilised with a bone plate, and multiple porosity gradient strategies were compared against a corresponding uniform scaffold composed of body-centred cubic (BCC) unit cells. Scaffolds composed of titanium alloy (Ti-6Al-4V), bioactive glass (45S5 Bio-glass), and polylactic acid (PLA) were evaluated to capture a range of material stiffnesses. Introducing porosity gradients consistently enhanced the mean octahedral shear strain within the scaffold, particularly in regions adjacent to the fixation plate affected by stress shielding. The magnitude of mechanical stimulus improvement increased with both greater porosity gradient magnitudes and higher gradient resolution. These improvements were more pronounced in stiffer materials, such as Ti-6Al-4V, emphasising the critical interplay between scaffold material properties and architectural design. These findings highlight the importance of tailoring both porosity profiles and material selection to optimise scaffold mechanics for bone regeneration.