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Wear behaviour of cross-linked polyethylene assessed in vitro under severe conditions

Paper ID Volume ID Publish Year Pages File Format Full-Text
12275 786 2005 9 PDF Available
Title
Wear behaviour of cross-linked polyethylene assessed in vitro under severe conditions
Abstract

The polyethylene (PE) for hip implants presents serious clinical problems; the production of debris may induce adverse tissue reactions that may lead to extensive bone loss around the implant and consequently osteolysis and implant loosening. Several attempts have been made to improve the wear properties of ultra-high molecular weight polyethylene (UHMWPE). More recently the attention of various researchers has been focused on cross-linked polyethylene (XLPE), due to its improved wear resistance with respect to conventional UHMWPE.This study was aimed at comparing the wear performances of clinically available acetabular liners (Zimmer Inc.) made of electron beam XLPE and conventional UHMWPE. To evaluate the influence of the material properties on wear, conventional UHMWPE and XLPE acetabular cups were tested against deliberately scratched CoCrMo femoral heads (Ra=0.12–0.14 μm) in a hip joint wear simulator run for 3 million cycles with bovine calf serum as lubricant.Gravimetric measurements revealed significant differences between the wear behaviours of the two sets of acetabular cups: XLPE exhibited a wear rate about 40 times lower than conventional UHMWPE. Raman spectroscopy coupled to partial least-squares analysis was used to evaluate the possible crystallinity changes induced by mechanical stress (and thus the material wear resistance): only the UHMWPE cup which showed the highest weight loss displayed significant crystallinity changes. These results were correlated to the thickness of the plasticity-induced damage layer.The wear debris produced during the tests were isolated according to a validated protocol and imaged by scanning electron microscopy . The wear particles produced by XLPE were smaller than those produced by UHMWPE; the latter were observed as fibrillar and agglomerated particles. The mean equivalent circle diameter was 0.71 and 0.26 μm for UHMWPE and XLPE, respectively.

Keywords
Conventional ultra-high molecular weight polyethylene; Cross-linked polyethylene; Roughened CoCr femoral heads; Hip joint simulator; Wear debris characterisation; Micro-Raman spectroscopy
First Page Preview
Wear behaviour of cross-linked polyethylene assessed in vitro under severe conditions
Publisher
Database: Elsevier - ScienceDirect
Journal: Biomaterials - Volume 26, Issue 16, June 2005, Pages 3259–3267
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering