In-vivo degradation mechanism of Ti-6Al-4V hip joints

In-vivo exposed Ti-6Al-4V implants were investigated to determine the degradation mechanism occurring during the articulating movements of the hip joint in the human body. Failed implants were compared to Ti-6Al-4V samples, which were tested in the laboratory for their tribocorrosion performance. The results strongly indicate that degradation of Ti-6Al-4V has occurred with the same mechanism for both the implants and the laboratory tested samples and, hence, block-on-ring tribocorrosion testing was found to be a useful tool for mimicking the degradation occurring in the body.The degradation mechanism was concluded to be of combined mechanical and chemical nature. Wear debris is formed and accumulated in large flakes (>100μm). Upon further sliding the flakes are pressed into the surface and ultimately crushed into small, brittle particulate debris (