Flow channel performance in 3D printed hydroxyapatite scaffolds to improve metabolism and tissue ingrowth in flat bone repair

The regeneration of flat bone present great challenges owing to the unique metabolic orientation and the great demand for nutrient transport. Reasonable structural design can effectively improve the performance of tissue regeneration of the scaffolds. In this study, bioactive hydroxyapatite scaffolds with various flow channel designs were precisely produced by 3D printing. The mechanical properties, permeability, substance transport and tissue ingrowth capacity brought by flow channel were investigated. Theoretical simulations and experimental results showed that the mechanical properties were highly correlated with the porosity of the scaffolds rather than the flow channel configurations. Curved channel showed a higher permeability for its better ability of omnidirec-tional diffusion, enhancing the substance transport and cell settlement by forming vortex flow. The flow channel scaffolds had better tissue ingrowth capability due to the abundant blood supply and cells/nutrients enrichment. Especially, the curved flow channel coupling with the annular one showed the best comprehensive performance in all the configurations designed, leading to the efficiency improvement of tissue ingrowth and bone regener-ation. This study proposed preliminary principles for the design of planar two-dimensional flow channel based on the characteristics of flat bone, which provided a potential feasible strategy for large-scale flat bone regeneration and repair.