Surface characterization and fatigue performance of a chemical-etched Ti-6Al-4V femoral stem for cementless hip arthroplasty

Abstract This work investigated the influence of a two-step chemical etching (H 3 PO 4  + NaOH) on the surface characteristics, coating properties and fatigue performance of a finished Ti-6Al-4V femoral stem early coated with Ti powder by thermal plasma spraying (namely TPS). Two further groups of stems were used as control: coated with TPS itself and coated with TPS followed by electrochemical deposition of CaP. The surface roughness and the coating properties based on ASTM F1854-15 were respectively evaluated by confocal laser scanning microscopy and scanning electron microscopy, whereas the fatigue performance was assessed according to the protocols given in ISO 7206-4:2010 standard and subsequent penetrant liquid testing. The two-step chemical etching produced a coral-like nanotopography and a finer, flatter and less porous surface, with an outward projected surface, in comparison to the CaP coating. All stems survived the fatigue tests (no fracture after 5 × 10 6 loading cycles) and no cracks were identified. The results indicated that two-step chemical etching may be suitable for modifying the surface of femoral stems used in cementless hip arthroplasty.