A design strategy for long-term stability of porous PEEK implants by regulation of porous structure and in vivo mechanical stimulation

The bioinert nature of polyether ether ketone (PEEK) material limits the widespread clinical application of PEEK implants. Although the porous structure is considered to improve osseointegration of PEEK implants, it is hardly used due to its mechanical properties. This study investigated the combined influence of the porous structure and in vivo mechanical stimulation on implantation safety and bone growth based on finite element analysis of the biomechanical behavior of the implantation system. The combined control of pore size and screw preloads allows the porous PEEK implant to achieve good osseointegration while maintaining a relatively high safety level. A pore size of 600 µm and a preload of 0.05 N·m are the optimal combination for the long-term stability of the implant, with which the safety factor of the implant is >2, and the predicted percentage of effective bone growth area of the bone-implant interface reaches 97%. For further clinical application, PEEK implants were fabricated with fused filament fabrication (FFF) three-dimensional (3D) printing, and clinical outcomes demonstrated better bone repair efficacy and long-term stability of porous PEEK implants compared to solid PEEK implants. Moreover, good osteointegration performance of 3D-printed porous PEEK implants was observed, with an average bone volume fraction >40% three months after implantation. In conclusion, 3D-printed porous PEEK implants have great potential for clinical application, with validated implantation safety and good osseointegration.