DEBUNKING THE MYTH THAT CERAMICS ARE BIOINERT: COMPARISON OF ALUMINA VERSUS SILICON NITRIDE

IntroductionOxide-based alumina (Al2O3) is used to manufacture femoral heads for total hip arthroplasty (THA). Silicon nitride (Si3N4) is a non-oxide ceramic used to make spinal implants. Ceramic materials are believed to be bioinert, (i.e., stable under hydrothermal conditions). Indeed, clinical data have shown 15–20 year longevity of Al2O3 bearings in THA. In this work, we examined the surfaces of Al2O3 and Si3N4 after exposure to physiologic conditions to see if these ceramics are truly inert.Materials and MethodsFour self-mated O28 mm diameter Al2O3 femoral heads (n=2 each of BIOLOX®forte, CeramTec, Plochingen, Germany; and BIOCERAM®, Kyocera Co., Kyoto, Japan), were retrieved during revision THA, between 7.7–10.7 years post-implantation. To simulate in vivo material aging, comparable, new Al2O3 and Si3N4 femoral heads (AMEDICA Corporation, Salt Lake City, UT, USA) were exposed to autoclave conditions (100°C-121°C; 300 hrs; n=3 heads, per material). Advanced Raman and cathodoluminescence spectroscopy,...