Artificial hip joints: The biomaterials challenge.

What is new and what comes next in artificial hip joints? These are the crucial questions we attempt to answer after accurately surveying the state of the art in the field of hip arthroplasty, especially related to non-metallic materials. Summarizing the present situation, one could safely state that the current generation of hard-on-soft and hard-on-hard hip bearings has become quite effective in exhibiting extremely low degrees of wear when compared to traditional implants made of cobalt-chromium alloys coupled with conventional polyethylene materials or to the primitive alumina materials used in the past. Moreover, at a stage of more than 10 years in the clinical follow-up of new generations of hard-on-hard bearings, and more than 10 years follow-up for highly cross-linked polyethylene materials, we should soon be expecting a new set of officially compiled statistics that show significant reductions in failures due to particle-mediated osteolysis as compared to past statistical compilations. However, further important issues (other than wear) remain unsolved, including structural reliability of advanced ceramic and polyethylene components. Severe challenges yet stand in optimizing the biomaterials choice for significantly extended lifetimes and reduced failure risks. Moreover, joint healing trends are expected to evolve more radically in the next few decades.