title: Failure mechanisms and closed reduction of a constrained tripolar acetabular liner.
abstract: 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.
authors.affiliation: Hospital for Special Surgery, New York, New York 10021, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Robertson
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Mattern
authors.forename: John
authors.initials: J
authors.lastname: Hur
authors.forename: Edwin P
authors.initials: EP
authors.lastname: Su
authors.forename: Paul M
authors.initials: PM
authors.lastname: Pellicci
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D011475:Prosthesis Failure