The effects of irradiation and EtO-treatment on ultrahigh molecular weight polyethylene acetabular cups following accelerated aging: Degradation of mechanical properties and morphology changes during hip simulator tests

Paola Taddei, Saverio Affatato, Mirko Rocchi, Concezio Fagnano, Marco Viceconti

Research output: Contribution to journalArticle

Abstract

The present study was aimed at investigating the effects of the sterilization method and accelerated aging on the wear and morphology of ultrahigh molecular weight polyethylene. In a first test, gamma- and EtO-sterilized acetabular cups were tested in a hip joint simulator for two million cycles. After the test, the cups underwent an accelerated aging treatment (80 °C, 4 weeks in air furnace) and were newly tested for another three million cycles. Wear was evaluated by gravimetric measurements, morphology by micro-Raman spectroscopy. During the first test, the EtO-sterilized cups underwent a significantly higher wear than the gamma-sterilized ones (62 and 30 mg/million cycles, respectively). No significant crystallinity changes were observed. Upon accelerated aging, the crystallinity increase of the gamma-sterilized cups was more pronounced than for the EtO-sterilized cups, due to chain scission and oxygen incorporation. In the second test, the wear rate of EtO-sterilized cups decreased to 38 mg/million cycles, while for gamma-irradiated cups it increased to 84 mg/million cycles. At the same time, the latter cups underwent significant increases in temperature and crystallinity, due to the higher friction. For the EtO-sterilized cups a significant decrease in crystallinity was observed, due to the occurrence of an orthorhombic → monoclinic phase transformation.

Original languageEnglish
Pages (from-to)254-263
Number of pages10
JournalJournal of Molecular Structure
Volume875
Issue number1-3
DOIs
Publication statusPublished - Mar 17 2008

Keywords

  • Accelerated aging
  • Acetabular cups
  • Hip joint simulator
  • Micro-Raman spectroscopy
  • Polyethylene
  • Sterilization

ASJC Scopus subject areas

  • Structural Biology
  • Organic Chemistry
  • Physical and Theoretical Chemistry
  • Spectroscopy
  • Atomic and Molecular Physics, and Optics
  • Materials Science (miscellaneous)

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