Failure Mechanisms and Closed Reduction of a Constrained Tripolar Acetabular Liner

William J. Robertson, Christopher J. Mattern, John Hur, Edwin P. Su, Paul M. Pellicci

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


Unlike traditional bipolar constrained liners, the Osteonics Omnifit constrained acetabular insert is a tripolar device, consisting of an inner bipolar bearing articulating within an outer, true liner. Every reported failure of the Omnifit tripolar implant has been by failure at the shell-bone interface (Type I failure), failure at the shell-liner interface (Type II failure), or failure of the locking mechanism resulting in dislocation of the bipolar-liner interface (Type III failure). In this report we present two cases of failure of the Omnifit tripolar at the bipolar-femoral head interface. To our knowledge, these are the first reported cases of failure at the bipolar-femoral head interface (Type IV failure). In addition, we described the first successful closed reduction of a Type IV failure.

Original languageEnglish (US)
Pages (from-to)322.e5-322.e11
JournalJournal of Arthroplasty
Issue number2
StatePublished - Feb 2009


  • constrained liner
  • dislocation
  • failure
  • hip arthroplasty

ASJC Scopus subject areas

  • Orthopedics and Sports Medicine


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