Abstract
Introduction: The failure of total hip endoprosthesis is usually caused by aseptic implant loosening which can be a result of inflammatory reactions of the periprosthetic tissue on released metallic and bone cement wear particles. The objective of the study was to analyse the abrasive interfacial wear behaviour of cemented stems depending on the composition of the bone cement. Material and methods: With a test device cemented anatomical hip stems with different surface topography and material composition were investigated. Following bone cements were used: high viscosity PMMA cement with ZrO2 (Palacos R), high viscosity PMMA cement with BaSO4 (CMW 2000) as radiopaque material, low viscosity PMMA cement with ZrO2 (Sulcem 3) and an experimental high viscosity cement without ZrO2.
Results and Discussion: The abrasive wear behaviour in the interface between the implant and the bone cement is clearly affected by the surface topography of the stem. Moreover, the composition of the bone cement had a substantial impact on the abrasive wear behaviour in the interface. The tests revealed that the commercial bone cements with ZrO2 particles caused a higher polishing effect on rough stems and increased release of metallic particles. The Ti6Al7Nb and Co28Cr6Mo stems, which were tested against the bone cement without ZrO2 and the bone cement with BaSO4, showed no surface damage in the macroscopic analysis, whereas in the SEM analysis abrasive wear on the stem surface could be detected. However, in case of the Palocos R cement the added ZrO2 particles led to an increased wear resistance of the cement mantle and therefore to a reduced release of cement wear particles compared to the other cements tested. Whether this result is based on a ball bearing effect of the hard ZrO2 particles, which may reduce the friction in the interface, or a reinforcement of the bone cement matrix, is still unclear. If the use of high viscosity bone cements with ZrO2 particles (Palacos R) leading to a reduced release of cement particles may compensate the increased accumulation of abraded metallic particles, has to be examined by subsequent cellbiological studies, whereas in clinical studies the Palacos R cement showed superior survial rate of cemented hip stems. The low-viscosity cement tested seems to be less wear resistant than the high-viscosity cements. However, the quantity of metallic particles released has still to be analysed with atomic absorption spectrometry.
Theses abstracts were prepared by Professor Roger Lemaire. Correspondence should be addressed to EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
