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 gliding surfaces with other material combinations, pseudocapsules and soft tissue membranes around hip endoprostheses retrieved at revision surgery or at autopsy were histologically investigated. In all tissue specimens around loosened prostheses, ceramic wear particles were found, in 50% of cases high-grade ceramic wear was seen. In contrast, only half of the autopsy cases revealed ceramic wear. Cases with Al2O3-Al2O3 combinations showed less villdus transformation of the synovial tissue, a thinner synovial layer and reduced necroses in comparison to Al2O3-polyethylene and metal-polyethylene combinations. These differences appeared more pronounced in the autopsy cases. The result of this study confirm the hypothesis, that a high ceramic wear rate in loosened prostheses develops mainly as a consequence of loosening. For that reason, biologically fixation of implants with spongious structured surfaces and without bone cement fixation seems a logical consequence. Modular systems are necessary not only for stem and ball, but also for the acetabular component of the hip endoprostheses.