Mechanical analysis of a PEEK titanium alloy macro-composite hip stem by finite element method

In this paper, numerical modeling and analysis of a HA-coated PEEK/Ti macro-composite hip stem is presented. The macro-composite hip stem consists of a titanium core in the center and a PEEK layer around it and a thin HA coating on the surface. The composite stem was designed and implanted in a standardized human femur bone model in SolidWorks software. The intact and postoperative femur bones were loaded like as in the single-leg stance of the walking gait and the effect of PEEK layer thickness on the internal stresses was analyzed in ANSYS software. Results were compared with an all-metallic stem model. Also, the fatigue strength of the stem and stresses occurring in the implant/coating interface were analyzed. With the composite stem, more homogeneous load distribution could be achieved, thus the stress-shielding effect was considerably reduced. Composite implants with 2 and 3 mm of PEEK layer provided sufficient fatigue strength in accordance with ASTM F2996-13 and ISO 7206-4:2010 standards. Maximum stresses at the coating/implant interface were well below the plasma-sprayed HA coatings strengths on PEEK implants. It is thought that the designed composite model may be an alternative to the standard HA-coated Ti alloy hip implants.