AL2O3 AGAINST AL2O3 COMBINATION IN HIP ENDOPROSTHESES - HISTOLOGIC INVESTIGATIONS WITH SEMIQUANTITATIVE GRADING OF REVISION AND AUTOPSY CASES AND ABRASION MEASURES

For comparison of hip endoprostheses with Al2O3 combinations of the gl iding surfaces with other material combinations, pseudocapsules and so ft tissue membranes around hip endoprostheses retrieved at revision su rgery or at autopsy were histologically investigated. In all tissue sp ecimens around loosened prostheses, ceramic wear particles were found, in 50% of cases high-grade ceramic wear was seen. In contrast, only h alf of the autopsy cases revealed ceramic wear. Cases with Al2O3-Al2O3 combinations showed less villdus transformation of the synovial tissu e, a thinner synovial layer and reduced necroses in comparison to Al2O 3-polyethylene and metal-polyethylene combinations. These differences appeared more pronounced in the autopsy cases. The result of this stud y confirm the hypothesis, that a high ceramic wear rate in loosened pr ostheses develops mainly as a consequence of loosening. For that reaso n, biologically fixation of implants with spongious structured surface s and without bone cement fixation seems a logical consequence. Modula r systems are necessary not only for stem and ball, but also for the a cetabular component of the hip endoprostheses.