Gas plasma precision cleaning, sterilization and surface activation of orthopedic implants promotes biocompatibility in a single, highly reproducible process step.
Materials used for orthopedic implants are typically inert metals/alloys, ceramics and polymers. Their surface properties are engineered to encourage osteo-integration, while surface cleanliness and sterility are critical for avoiding inflammatory responses. Indeed, for implanted medical devices, achieving and maintaining surface cleanliness at the molecular level demands careful attention and exhaustive procedures.
Plasma processing is capable of removing organic contamination at the molecular level subsequent to machining, tooling and wet chemical processing steps. Plasma cleaning acts on surfaces in a conformal fashion, not only for substrates of complex geometries but also on textured surfaces with “rough” topographies. Plasma has also been shown to increase surface bioactivity, particularly on organic tissue scaffolds.
The method used to sterilize orthopaedic materials has been shown to have an effect on their long term wear properties. For example, wear characteristics of ultra-high molecular weight polyethylene (UHMWPE), used in the manufacture of acetabular liners, are adversely altered by gamma irradiation in presence of oxygen. In low O2 atmospheres gamma irradiated UHMWPE avoids immediate oxidation and even crosslinks the surface resulting in increased wear resistance. However long-term oxidation of free radicals markedly reduces wear resistance. Plasma sterilization avoids immediate and long term oxidative degradation wear characteristic.
