The use of dense alumina-alumina ceramic combination in total hip replacement

The purpose of this article was to review the laboratory and clinical performances since 1970 of a total hip prosthesis using alumina-alumina combination. The chemical and physical properties of dense alumina ceramic were studied in relation to biocompatibility, mechanical strength, and surface properties. Through the examination of 35 retrieved implants, it was found that the long-term success of alumina-alumina total hip replacement depends on both the ceramic microstructure (small grain size with uniform distribution, minimum porosity, absence of inclusions) and implant geometry (sphericity deviation +/- 1 micron, radius tolerance between components 7-10 microns). Alumina component wear and fractures have disappeared with the use of high-performance materials and severe manufacturing quality control. Examination of human biopsies from well-fixed prostheses showed that alumina particles deposits increase with time with only a low-grade macrophagic reaction. When loosening occurred, an inflammatory reaction appeared; this reaction was less striking than with loose metal-polyethylene prostheses, however. The long-term behavior of cementless alumina cup fixation depends upon initial positioning and stability; survivorship analysis of the cemented ceramic cups showed an 88% survival probability after 8 years with a 1.6% average annual probability of revision. The percentage of surviving was 100% after 8 years in patients who were less than 50 years old. Aseptic loosenings occurring at the cup-cement interface were assumed to be related to stress protection secondary to the high rigidity of the ceramic leading to a weakening of the spongious bone supporting the cement mantle. Good bone stock quality as well as high-quality ceramic appear to be the prerequisites for durable fixation of alumina sockets.