Abstract
Background
Uncemented implants are an important part of the arthroplasty armamentarium. Risk of aseptic loosening and failure of these components is related to initial osseointegration - the formation of a seamless bone-implant interface without interposition of fibrous tissue.
Aim
Modification of the surface properties of titanium alloy, to enhance suitability for early osseointegration.
Methods and Results
Samples of Ti6Al4V were prepared with different surface finishes: machined; polished with grit papers to a mirror finish or treated in an electrochemical cell with sulphuric acid/methanol electrolyte using 3, 5 or 9V for 60, 120 or 180 seconds . Electrochemical modification produced average roughness (Ra) values, which differed significantly between the 3 different voltages applied (p<0.05) with those treated at 3V being the roughest and those at 9V the smoothest.
Rat osteoblasts and human mesenchymal cells were cultured on the samples for 24 hours and 48 hours respectively. Immunofluorescence was performed to localise vinculin, elucidating cell morphology and identifying focal adhesion complexes.
Surface modification created quantifiable differences in morphology of rat osteoblasts. Rat cells on Ti6Al4V treated with 3V and 5V were significantly more polarised than those on 9V, glass and polished control surfaces (p=<0.05). This behaviour can, in part, be explained by differences in size and distribution of focal adhesions, which act as anchor points for cell adhesion. There is a trend for lower density of focal adhesions on the surfaces treated with 3V and 5V compared to those treated with 9V and the control surfaces, with some comparisons reaching statistical significance (3V180s, 5V60s and 5V120s vs 9V120s p=<0.05).
These differences were also seen with human cells. Those on the 3V and 5V surfaces were significantly more polarised (p<0.05) than those on the 9V and control surfaces. Focal adhesion area was also significantly lower on 3V and 5V surfaces compared with glass and 9V surfaces.
Preliminary results from long term culture of rat osteoblasts show greater areas of bone nodule formation on surfaces modified with higher voltages for longer time periods.
Conclusion
Electrochemical modification of titanium alloy alters morphology and adhesion-related behaviour of rat and human osteoblasts, which influences differentiation and osteogenesis.
