The relation between micromotion and screw fixation in acetabular cup

Jui Ting Hsu, Kuo An Lai, Qingshan Chen, Mark E. Zobitz, Heng Li Huang, Kai Nan An, Chih Han Chang

Research output: Contribution to journalArticlepeer-review

35 Scopus citations


One of the major causes inducing loosening in the cementless acetabular cup implanting is its insufficient initial stability. In this study, three-dimensional finite element models of the pelvis and acetabular components were developed to investigate the relationship between relative micromotion, initial stability, and screw fixation under six daily activity loadings. A commercial available hemispheric cup with five screw holes was used as the target acetabular cup. The simulation results showed that if screws were placed closed together, when the screw number increased from 1 to 5, the peak micromotion decreased less than 14%, from 126.5 to 108.8 μm, while the stable region, micromotion less than 28 μm, enlarged only by 40%, from 46.1% to 64.7%. However, if the screw could be placed near the cup rim, a single rim screw, 202.1 μm micromotion, could provide better stability than that of four dome screws, 209.6 μm micromotion, placed closed together. To conclude, multiple cup screws should be placed near cup rim and as separate as possible to enlarge the stable region and reduce the peak micromotion between cup and acetabulum.

Original languageEnglish (US)
Pages (from-to)34-41
Number of pages8
JournalComputer Methods and Programs in Biomedicine
Issue number1
StatePublished - Oct 2006


  • Acetabular cup
  • Finite element methods
  • Initial stability
  • Screw fixation

ASJC Scopus subject areas

  • Software
  • Computer Science Applications
  • Health Informatics


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