Behavior of Commercially Pure Titanium and Ti-318 (Ti-6Al-4V) in Orthopedic Implants

At the Royal National Orthopaedic Hospital major replacement of long bones began in 1949, and the first titanium-containing endoprosthesis was inserted in 1964. By now over 250 titanium-containing endoprostheses of various kinds have been inserted. Most of these components were made on a modular basis and included sections of cast cobalt-chromium-molybdenum alloy. In 1972 titanium alloy 318 (Ti-318)(Ti-6Al-4V) was introduced, and this alloy largely replaced the previously used commercially pure titanium.

This paper presents our experiences with these endoprostheses, with titanium total hip replacements, and with other titanium devices. Using standard statistical methods, survival curves for the nonremoval of the component were obtained. These curves demonstrated that the performance of upper femoral, lower femoral, and upper tibial endoprostheses was slightly worse than that of standard total hip replacements. This worse performance was a result of five intramedullary stem fractures, but we now think that this problem has been overcome by the introduction of Ti-318. These and other fractures emphasize the importance of good design, good surface finish, and optimum stem or section size. There was no evidence that the combination within a single implant of cobalt-chromium-molybdenum and titanium, commercially pure or alloy, caused corrosion or clinically significant problems. Although blackening of adjacent tissue has been observed, there was no evidence that this was associated with an undesirable tissue response.