Study on the Fatigue Mechanical Behavior of Selective-Laser-Melted Ti6Al4V Gradient Porous Scaffold for Repairing Tibial Bone Defect

Large segmental tibial defect is a disease that cannot heal spontaneously. For its repairing, this study develops a Ti6Al4V(TC4) gradient porous filled scaffold, and corresponding mechanical behavior needs to be studied. Finite element models of the uniform/gradient porous filled scaffolds combined with the plate-screw fixation system for tibial defects were established. The static and fatigue biomechanical behavior of the porous filled scaffold at different gaits were analyzed. Then the TC4 gradient porous filled scaffold was prepared by 3D printing and assembled in the bovine tibia, and its fatigue safety was verified by in vitro fatigue service test. The addition of the porous filled scaffold decreased the axial displacement of the tibial defect model and the deformation of the plate. Compared with the uniform scaffold, the gradient scaffold with the same porosity revealed higher mechanical properties, reduced the stress of the plate-screw fixation system. In addition, the fatigue simulation results and in vitro fatigue tests showed that the gradient scaffold had ability to cope with the high-cycle fatigue of the tibial defect compared with uniform scaffold. The 3D-printed TC4 gradient porous filled scaffold can provide good stability and fatigue performance for the repair of tibial segmental defects.