Until the year 2010 the most important medical implants are assumed to be the total hip prosthesis (THP), the total knee prosthesis (TKP) and the vascular stent according to the WHO. Metals are the major constituents of the hip and knee implants and so far of vascular stents. Metallic implants also play an important role in the reconstructive surgery in the fields of tumour and trauma therapy.
The high strength and fatigue resistance as well as availability, easy processing and moderate prices explain the important roles gained by metals in implantology. A particular importance is given to titanium and its alloys, because these metals may be integrated into surrounding tissues, and especially hard tissues, and exhibit chemical and mechanical bonding, indicative of good biocompatibility/histocompatibility and biofunctionality.
A well engineered coating of implants with very thin calcium-(phosphate)layers seems to be further advantageous.
The use of metallic implants is not without problems. Different and high rates of corrosion influence the choice of an implant material, since fretting corrosion among others may contribute strongly to the production of wear particles which might lead to a particle disease and to implant loosening consecutively. The corrosive behaviour is influenced by the industrial processing and the surface structure of the implant.
Important, too, is the affinity of metallic surfaces to microbial contaminants and biofilms. The rate of implant infection, necessitating the riskful exchange of the implant, even in good clinics, can reach 2 %-3 %, as taken from literature.
The careful design for first time implants and for exchange implants has to face the problems of stress shielding and loss of bone stock.
The major influence of surgical training is demonstrated by the Scandinavian implant register study.