Mechanical Properties of 3D-Printed Porous Poly-ether-ether-ketone (PEEK) Orthopedic Scaffolds

Poly-ether-ether-ketone (PEEK) has evolved to be the preferred biomaterial for orthopedic implants; however, its bioinert nature significantly limits its osseointegration property. Porous PEEK implants can effectively promote osseointegration, yet pores also decrease the scaffold's load-bearing capacity. Hence, it is critical to developing an optimum pore-sized scaffold with favorable mechanical properties. In this study, we used 3D printing to develop PEEK scaffolds with precise pores ranging from 100 mu m to 600 mu m. We first experimentally determined the scaffolds' compressive properties and then used finite element analysis (FEA) to investigate the scaffolds' stress distribution and failure modes. Results indicate that 3D-printed PEEK with 300-mu m pore size exhibits the highest yield compressive strength, and increasing the pore size beyond that would decrease the specimen's yield strength. Furthermore, FEA denoted that the stress distribution is the maximum in the scaffold core along the longitudinal axis under compressive load and less on the scaffold's outer shell. Finally, buckling simulation results confirmed that the specimens fail according to the second buckling mode with two curvatures, similar to the real-time experimental results. Our studies suggest that 3D-printed PEEK specimens with 300-mu m pore sizes exhibit the best compressive yield strength suitable for orthopedic applications.