For orthopaedic implants the adhesive strength of bone cells on implant surfaces is of high interest. In some cases the adherence of cells is desirable, e.g. on endoprosthetic implants, in others, mainly temporarily used implants, e.g. intramedullary nails, it is not favourable for the cells to attach to the implant. Therefore, besides cell spreading and proliferation on surfaces the adhesion strength with which cells bond to the substrate is of high interest. There are different approaches to determine bone cell adhesion, but no easy to operate quantitative methods are available. For this purpose, based on the spinning disc principle, we have developed a new adhesion device in conjunction with an inverse confocal laser scanning microscope (LSM).

Polished disc-shaped test samples made of Ti6Al4V were seeded with bone cells (MG-63), stained with a fluorescent dye, at defined radial positions and were incubated for 18 h with cell medium. After incubation the test samples were placed into the adhesion chamber filled with 250 ml cell medium (DMEM). The test samples were rotated at various velocities until a minimum detachment of 50% was achieved. Using the LSM the detachment of the bone cells at the defined radial positions was determined and the cell count was recorded before and after rotation by means of imaging software.

An average shear stress of 50 N/m2 was determined for polished Ti6Al4V surfaces. To calculate the adhesion force, the cross-sectional cell area has to be measured by the xz-scan of the LSM.

Our results are reproducible and comparable to the data found in literature. The advantage of our new approach is that the same cells can be observed before and after rotation as well as different rotational speeds can be applied to the same cell population. Further investigations e.g. using different surfaces are carried out.