Effects of screw eccentricity on the initial stability of the acetabular cup

Jui Ting Hsu, Chih Han Chang, Kai Nan An, Mark E. Zobitz, Rapin Phimolsarnti, Ronald R. Hugate, Kuo An Lai

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


One of the major failure modes of cementless acetabular components is the loosening of the acetabular cup, which is mostly attributable to insufficient initial stability. A hemispherical cup with a porous coating which is inserted with press-fit fixation and secured with several screws is one of the most widely used approaches. Many studies have found that bone screws are very helpful aids for cup fixation, but the optimal surgical technique for inserting screws has not been clearly reported. In this study, hemispherical cups were fixed into blocks of foam bone with zero to three screws. The effects of three types of screw eccentricity (a 1-mm offset and angular eccentricities of 15° and 25°) on the initial stability of the acetabular cup were evaluated. The experimental results indicate that increasing the number of screws enhances the cup stability in the case of ideal screwing (i.e., with no eccentricity). An angular eccentricity of 15° did not affect the cup stability for fixation with one or two screws. However, the presence of 25° of angular eccentricity significantly reduced the stability of the cup, while 1 mm of offset eccentricity produced an even greater impact.

Original languageEnglish
Pages (from-to)451-455
Number of pages5
JournalInternational Orthopaedics
Issue number4
Publication statusPublished - 2007 Aug

All Science Journal Classification (ASJC) codes

  • Surgery
  • Orthopedics and Sports Medicine

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