Enhancing bone ingrowth and mechanical bonding in 3D-printed titanium alloy implants via lattice design and growth factors

Abstract

Patient-specific three-dimensional (3D)-printed titanium alloy implants often face challenges such as stress shielding and inadequate 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 large-scale bone defects at the distal femur condyle in a New Zealand rabbit model. Hollow cylindrical implants (length: 12 mm; diameter: 6 mm [outer], 2 mm [inner]) 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-computed tomography (CT) imaging assessed bone ingrowth volume across zones, while mechanical testing evaluated shear bond strength. The results demonstrated that growth factors are 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 demonstrated 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.

Keywords

3D printing / Bone defect / Growth factor / Lattice / Platelet-rich fibrin