Through direct osseointegration, topographical surface biofunctionalisation of orthopaedic implants may enhance their integration and long term stability. In this respect, the controlled design of surface topography has been shown as a major modulator of osteogenic cell function thus, potentially, providing favourable peri-implant environment for bone deposition and maintenance. Within the framework of the VW-Foundation project NanoMIM our group in collaboration with the Fraunhofer Institute IFAM developed a micron-scale metal injection moulding process (µ-MIM) using hybrid nano/micro powder mixtures, to obtain a precise replicated surface topography with a defined submicrometer roughness.

The micrometer surface structure can be freely predefined. For instance, a surface exhibiting regular, defined, potentially bioactive surface arrays in the form of micrometer scale hemispheres with 5, 30 and 50 µm in diameter having a predefined submicrometer-sized surface roughness can be produced. In the bulk material, by using hybrid micro/nano powder mixtures, an ultra fine grain size (nanostructure) is obtained, providing enhanced mechanical strength and ductility (In case of stainless steel, the following parameters have been obtained: nearly 100% material density (standard: 97%), 530 MPa yield strength (standard 200 MPa) and 720 MPa tensile strength at room temperature (standard: <700 MPa).). The topographical micrometer sized structures as investigated in this study, induced considerable changes in FA plaque size of adult human bone marrow stromal cells (HBMCs) seeded on these surfaces. More importantly, we have quantitatively demonstrated that the seeded cells migrated at a higher velocity on these surfaces. The method is patented more...

(Ownership: Fraunhofer Institut für Fertigungstechnik und Angewandte Materialforschung, Empa. For licence please contact: Dr. Monica Kalbermatter Monica.Kalbermatter(at)empa.ch).

Currently, in addition other surfaces produced by various methods are under investigation