Innovative surface modification of Ti–6Al–4V alloy with a positive effect on osteoblast proliferation and fatigue performance

• Surface modification combining EDM, chemical milling and shot-peening was developed.
• Fatigue endurance was improved when high Almen intensity and small shots were used.
• Chemical milling creates favourable surface morphology and increases oxygen content.
• The three-step surface modification has a positive effect on the osteoblast growth.
• EDM and EDM with shot peening supported early osteogenic cell differentiation.

A novel approach of surface treatment of orthopaedic implants combining electric discharge machining (EDM), chemical milling (etching) and shot peening is presented in this study. Each of the three techniques have been used or proposed to be used as a favourable surface treatment of biomedical titanium alloys. But to our knowledge, the three techniques have not yet been used in combination.Surface morphology and chemistry were studied by scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. Fatigue life of the material was determined and finally several in-vitro biocompatibility tests have been performed. EDM and subsequent chemical milling leads to a significant improvement of osteoblast proliferation and viability thanks to favourable surface morphology and increased oxygen content on the surface. Subsequent shot-peening significantly improves the fatigue endurance of the material. Material after proposed combined surface treatment possesses favourable mechanical properties and enhanced osteoblast proliferation. EDM treatment and EDM with shot peening also supported early osteogenic cell differentiation, manifested by a higher expression of collagen type I. The combined surface treatment is therefore promising for a range of applications in orthopaedics.