title: Wear patterns of taper connections in retrieved large diameter metal-on-metal bearings.
abstract: Wear of the modular taper between head and shaft has been related to clinical failure resulting from adverse reactions to metallic debris. The problem has become pronounced in large metal-on-metal bearings, but the mechanism has not yet been fully understood. We analyzed retrieved components from five patients revised with various diagnoses. Two distinct wear patterns were observed for the head tapers. Three samples demonstrated "asymmetric" wear towards the inner end of the head taper. The other two showed "axisymmetric" radial wear (up to 65 µm) presenting the largest wear volumes (up to 20 mm(3)). Stem tapers demonstrated relatively little wear, and the fine thread on the stem taper surface was observed to be imprinted on the taper inside of the head. Our findings demonstrate that the cobalt-chrome head wears preferentially to the titanium stem taper. "asymmetric" wear suggests toggling due to the offset of the joint force vector from the taper. In contrast, samples with "axisymmetric" radial wear and a threaded imprint suggested that corrosion led to head subsidence onto the stem taper with gradual rotation.
authors: Instistute of Biomechanics, TUHH Hamburg University of Technology, Denickestrasse 15, 21073, Hamburg, Germany. bishop@tuhh.de
authors: Nicholas
authors: N
authors: Bishop
authors: Florian
authors: F
authors: Witt
authors: Robin
authors: R
authors: Pourzal
authors: Alfons
authors: A
authors: Fischer
authors: Marcel
authors: M
authors: Rütschi
authors: Markus
authors: M
authors: Michel
authors: Michael
authors: M
authors: Morlock
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D002858:Chromium Alloys; D004577:Electron Probe Microanalysis; D019544:Equipment Failure Analysis / Q000379:methods*; D006622:Hip Prosthesis; D006801:Humans; D008670:Metals; D008854:Microscopy, Electron; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D014025:Titanium
chemical_list: D002858:Chromium Alloys; D008670:Metals; D014025:Titanium