Application of Vanadium-Free Titanium Alloys to Artificial Hip Joints
Katsuhiko Maehara, Kenji Doi, Tomiharu Matsushita, Yoshio Sasaki
The application of titanium and its alloys to surgical implants has created much interest recently. Ti–6Al–4V has been used for numerous applications that require high mechanical properties, however this alloy contains vanadium, which has been proven to be cytotoxic. Two types of vanadium-free titanium alloys were developed and applied to artificial hip joints. As for the cemented type, Ti–15Mo–5Zr–3Al alloy was adopted because of its high fatigue strength, and its low elastic modulus, which approaches bone elasticity. As for the non-cemented type, Ti–6Al–2Nb–1Ta–0.8Mo alloy was adopted because of its less decrease of fatigue strength through heat treatments up to 1270 K, which is necessary to create the porous surface to activate the reaction between the implant and the bone. In addition, new coatings and bioactive methods were applied to the newly developed non-cemented type of prostheses. These hip joints are now successfully being used with excellent clinical results.