Influence of Electro Discharge Machining of Biodegradable Magnesium on the Biocompatibility

Biodegradable implants are in the focus of recent research approaches in the medical engineering sector for the treatment of many different defects. In comparison to permanent implants the risk of inflammatory reactions is significantly reduced and no foreign material is left in the body using degradable materials. Due to the extraordinary biocompatibility and initial structural stability, similar to the human bone, magnesium alloys are best suited for degradable orthopedic implants. But up until now the degradation of magnesium inside the human body is too fast and therefore the structural stability is lost too early. Newest research suggests that the degradation kinematic as well as the cell response of the implant can be improved by adjusting certain surface properties, e.g. complex micro- and macrostructures. Since these structures are very difficult to be machined with conventional processes, especially for complex and filigree 3D-structures, alternative manufacturing processes need to be developed. Electro Discharge Machining in combination with a Plasma Electrolytic Conversion of the surface is very well suited for the creation of geometries with high aspect ratios and microstructures. The focus of this paper lies on the investigation of the influence of the production processes on the biocompatibility of the machined part. The process chain for such implants will therefore be analyzed in regard to macro and micro surface properties using SEM and EDX-analysis. These results are then compared to biocompatibility testing concerning cell viability and toxicity.