Biomechanical and Hydrodynamic Characterization of Gradient-Porosity Triply Periodic Minimal Surfaces Polyether Ether Ketone Scaffolds for Craniofacial Bone Defect Repair

Large segmental craniofacial bone defects remain a major clinical challenge, and scaffold-based bone tissue engineering offers a promising regenerative strategy. This study comprehensively evaluated the biomechanical and hydrodynamic properties of gradient-porosity triply periodic minimal surface polyether ether ketone scaffolds across 5 geometries (Diamond, Gyroid, Schwarz, Split P, and Lidinoid) for bone defect repair. The scaffolds were designed as cylindrical gradient-porosity constructs (10 mm in diameter and 10 mm in height). A low porosity (50%) was maintained within the 2-mm peripheral zone to provide mechanical support, whereas the central region (3-mm radius) featured higher porosities (50%, 60%, 70%, and 80%) to enhance mass transport. Mechanical behavior was evaluated by uniaxial compression testing and finite element analysis under compressive and rotational loads, and hydrodynamic behavior was assessed by computational fluid dynamics. The Lidinoid and Diamond scaffolds exhibited the highest construct stiffness. Increasing the central porosity reduced both compressive and rotational stiffness and amplified stress concentrations at the porosity transition zones. The highest peak von Mises stresses were observed in the Schwarz scaffolds under compressive loading and in the Diamond scaffolds under rotational loading. Higher central porosity increased permeability and reduced the inlet-to-outlet pressure differential. The Schwarz and Split P scaffolds showed the highest permeability, whereas the Gyroid and Split P scaffolds maintained the most uniform velocity distributions. In conclusion, both the geometry and the gradient-porosity significantly influenced scaffold behavior. The Split P scaffolds offered the best balance between biomechanical and hydrodynamic performance, highlighting their potential for clinical translation in craniofacial bone defect repair.