An in vitro multi-parametric approach to measuring the effect of implant surface characteristics on cell behaviour

Orthopaedic implants are designed to promote biocompatibility and hence their integration with surrounding tissue. This involves influencing cell-implant interactions through changes in both surface topography and surface roughness. However, the large range of machining techniques used in implant manufacture and inconsistencies in the measurement techniques used for surface characterization make it difficult to measure the impact of surface characteristics on cell-implant interactions. Here, we describe a new in vitro multi-parametric approach that uses commercially available arrays of engineered surfaces that linearly increase in roughness, as measured by Ra, and that can be used to obtain quantitative measurements of cell attachment, differentiation and bone formation. Using this model, we demonstrate that cell attachment above 50% confluency occurs over a narrow range of roughness (Ra from 0.0125 microm to 6.3 microm) and that promotion of cell differentiation and bone development, while significantly influenced by surface topography, does not correlate directly with initial levels of cell attachment. These results compare well with published in vivo implant biocompatibility data indicating that this approach has the potential to offer a rapid, reliable and reproducible in vitro prediction of in vivo implant biocompatibility.