Early osteointegration evaluation of porous Ti6Al4V scaffolds designed based on triply periodic minimal surface models

Background: The graded porous structures were designed using triply periodic minimal surfaces models to mimic the biomechanical properties of bone. The mechanical properties and bone formation ability were evaluated to explore the feasibility of the design method in bone tissue engineering. Methods: The scaffolds were designed using a P-surface with different pore sizes. All materials were fabricated using 3D printing technology and the mechanical properties were tested by an electronic universal testing device. The biomechanical properties were then analyzed by finite element method, while the ontogenesis of the material in vivo was examined by implanting the scaffolds for five weeks in pigs. Results: According to the obtained results, the pore size ranged between 100 mu m to about 700 mu m and porosity were around 49.54%. The graded porous architectures can decrease the stiffness of implants and reduce the stress shielding effect. In addition, these porous structures can stimulate bone ingrowth and achieve a stable interface between implants and surrounding bone tissues after 5 weeks' implantation. The micro-CT results also demonstrated the obviously bone formation around all the porous structures. Conclusion: To sum up, the triply periodic minimal surfaces based graded porous structure is effective in decreasing the stress shielding effect, promoting early osteogenesis and osteointegration. This is the first research to explore the effect of this kind of porous structures on bone formation in vivo where the obtained results supported the previous theoretical research on the application potential in bone tissue engineering. The translational potential of this article: Porous architecture designed using triply periodic minimal surface models can achieve gradually changed pore size and appropriate porosity for bone regeneration. This kind of structure can mimic the Young's modulus of natural bone tissue, improve the stress transmission capability and dismiss the stress shielding effect. It also can stimulate the early bone integration in vivo and enhance the binding force between bone and implants, which may bring a new design method for orthopaedic implants and their surface structure. (C) 2019 The Authors. Published by Elsevier (Singapore) Pte Ltd on behalf of Chinese Speaking Orthopaedic Society.