In vitro serum levels of metal ions released from orthopaedic implants

Metallic materials in orthopaedic implants must bear mechanical loads with resultant surface damage. In addition to mechanical load, the surface damage on the implants occurs due to electrochemical corrosion from the physiological environment in-vivo. This research investigates in vitro experimental test bodies (surface area: 4.71 cm²) of four different ISO (International Organization for Standardization) standardised, frequently used, artificial implant alloys (TiAl₆V₄, Ti, CoCr₂₉Mo, FeCrNiMoMnNbN). The test materials were immersed in inert polystyrene test tubes filled with 1 ml of serum (pH 7.4) by avoidance of any friction and mechanical load. Here, they were subject to electrochemical corrosion independently of mechanical influences when in contact with body liquids. It was found that up to 80% of the entire dissolution of each ion occurred within the first 24 h of immersion. Additionally, the dissolution of the metal ions depended on the proportional mix of the individual elements in respective alloys. Therefore, the highest percent of ion concentration was found for Co (CoCr₂₉Mo) followed by Fe (FeCrNiMoMnNbN) and Mo (FeCrNiMoMnNbN). The lowest percent of ion concentrations were evident for Ti (Ti), Cr (CoCr₂₉Mo) and Cr (FeCrNiMoMnNbN).