Vortex-enhanced bone regeneration: gyroid gradient scaffolds tune permeability for hemodynamic-accelerated osseointegration.

Bone defects, prevalent in orthopaedic practice due to trauma or disease, present apparent clinical repair challenges. This study innovatively designed vortex-enhanced gyroid gradient scaffolds through finite element hydrodynamic simulation and selective laser melting (SLM) 3D printing, systematically evaluating their permeability and osteogenic efficacy. Homogeneous triply periodic minimal surface (TPMS) gyroid structures (50%, 60%, 70% porosity) and a gradient porous scaffold (average 60% porosity) were modeled. ANSYS-based hydrodynamic analysis revealed that the gradient scaffold maximized specific surface area for cell adhesion/proliferation. Crucially, at equivalent porosity (60%), it achieved 21% higher permeability (3.44 × 10-9 m2vs. homogeneous 2.85 × 10-9 m2), meeting skeletal implant requirements. The gradient structure exhibited vortex-driven flow characteristics - elevated central velocity and reduced wall velocity - mimicking natural bone hemodynamics to enhance nutrient transport. Scaffolds fabricated via SLM were implanted into rat tibial defects. Radiographic and histological analyses demonstrated 35% greater new bone area in the gradient group, with histological sections revealing uniform osteoblast distribution and mature bone matrix deposition, confirming hemodynamic-accelerated osseointegration. This work establishes a "simulation-design-fabrication-validation" pipeline, providing a paradigm for personalized bone scaffolds with tunable permeability to optimize clinical outcomes.