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Wuttke V.,Mathys Orthopaedie GmbH | Witte H.,TU Ilmenau | Kempf K.,Mathys Orthopaedie GmbH | Oberbach T.,Mathys Orthopaedie GmbH | Delfosse D.,Mathys Ltd. Bettlach
Biomedizinische Technik | Year: 2011

Ceramic-on-ceramic articulations are a frequently used bearing for total hip replacements. This success mainly is due to their excellent tribological properties. Ceramics can withstand high pressure loads due to its brittleness but only low bending stresses. A ceramic ball head fracture is the result of subcritical crack growth. This kind of fracture in vivo can abet by damage or contamination of the stem cone. The main goal of this work is to provide a risk assessment of different possible damage mechanisms and contaminations that may result in lower fracture strength of a ceramic ball head. To simulate potential causes, different types and dimensions of metal wire, foils, hair, and lubricants were inserted between the ceramic ball head and the metal cone of the stem. The test results clearly show that fracture strength is negatively influenced by most of the inhomogeneities between the cone and the head because they increase the peak stresses acting on a part of the ceramic ball head. The results of this article clearly confirm the demand for an undamaged taper fit "free of contamination" between the ceramic head and the metal cone during implantation. © 2011 by Walter de Gruyter Berlin Boston 2011. Source

Ortmann C.,Mathys Orthopaedie GmbH | Oberbach T.,Mathys Orthopaedie GmbH | Richter H.,Fraunhofer Institute for Ceramic Technologies and Systems | Puhlfurss P.,Fraunhofer Institute for Ceramic Technologies and Systems
Journal of the European Ceramic Society | Year: 2012

Properties and proof of suitability of homogeneously and graded ZTA bioceramics with various Y 2O 3 stabilized zirconia contents were investigated. Therefore porous alumina was infiltrated with different amounts of Y 2O 3 doped ZrO 2 precursors. At homogeneously infiltrated samples biaxial flexural strength and wear behavior were investigated (ISO 6474). Subsequently, at hip joint heads the static fracture strength was determined (ISO 7206-10). Materials ranging from approx. 4 to 20wt% Y 2O 3 stabilized zirconia were characterized relative to the sinter density, the microstructure, the phase composition and the dispersion of the stabilized zirconia phase. Bioceramics showed high sinter density, fine microstructures, excellent wear property and significantly increased biaxial flexural strength. A 41% increase in strength through the formation of Y 2O 3 stabilized zirconia gradient in the conical bore of the heads was reached. Low compressive stresses in cone of this heads were found. ZTA bioceramics are potentially suitable for use as hip replacement components. © 2011 Elsevier Ltd. Source

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