Enhancing bone ingrowth and mechanical bond strength at the titanium alloy 3D-printed implant-bone interface through advanced lattice designs and growth factor integration

Patient-specific titanium alloy 3D-printed implants often face challenges such as stress shielding and insufficient osseointegration. This study investigated the effects of lattice designs and growth factor-enriched sticky bone on bone ingrowth and mechanical bond strength at the implant-bone interface of the large-scale bone defect at distal femur condyle of New Zealand rabbit model. Hollow cylindrical implants (12 mm length, 6 mm outer, 2 mm inner diameters) with diamond (DU) and randomly deformed spherical (YMR) lattices were designed and implanted into rabbit femoral condyles. Platelet-rich fibrin (PRF) was prepared using a novel negative pressure centrifuge and mixed with synthetic bone graft material to form sticky bone, which was used to fill the implant cavities. Micro-CT imaging assessed bone ingrowth volume across zones, while mechanical testing evaluated shear bond strength. The results demonstrated that growth factors were the primary driver of bone ingrowth and mechanical strength. Bone growth volume increased significantly in Zone A (implant cavity), with sticky bone yielding a 6.9-fold increase for DU (6.66 mm³ vs. 45.89 mm³) and a 3.5-fold increase for YMR (14.68 mm³ vs. 51.95 mm³). Across Zones B and C (lattice layers), YMR lattices consistently outperformed DU in promoting bone growth and stability. Push-out tests showed shear bond strengths of 2.78 MPa for DU and 2.83 MPa for YMR with growth factors, compared to 1.71 MPa for controls. This study highlights the critical role of growth factors in enhancing bone integration and demonstrates the complementary benefits of optimized lattice designs, particularly YMR, in improving osseointegration and mechanical stability. The findings provide a promising strategy for using 3D-printed titanium alloy implants with sticky bone systems to address large bone defects in clinical applications.