[15 years experience with the Ti-6Al-7Nb alloy for joint prostheses]

The Ti-6Al-7Nb alpha-beta alloy, Protasul-100 was developed between 1978 and 1982, and proved to be highly biocompatible. In 1985 the TiAlNb material was approved for clinical use. Over the last ten years, more than 200 tons of semi-finished bar material has been processed, mainly for the production of cementless femoral stem systems and elastically deformable cup shells. For uncemented femoral components of knee prostheses made of TiAlNb, a special oxygen diffusion hardening process was developed that enables a surface hardness of up to 1200 HV and 600 HV at a depth of 20 microns, as compared with 350 HV in the case of the TiAlNb base material. This ODH-treated, polished surface is extremely scratch and wear resistant, and forms a good articulating surface with UHMW polyethylene. This surface-hardened TiAlNb, Tribosul, has been in clinical use in femoral knee components since 1990, and a multicentric clinical study involving femoral heads for hip prostheses has been ongoing since 1992. These different applications in hip and knee joint prostheses may suffice to demonstrate that the custom-made Ti-6Al-7Nb alpha-beta alloy is a real alternative to the well-known Ti-6Al-4V alloy, which has been used for decades as an implant material. Both national and international standards are available, and the alloy was already approved by the FDA in 1987.