title: Fixation failures of dual mobility cups: a mid-term study of 2601 hip replacements.
abstract: BACKGROUND
  The use of dual-mobility cups has increased because of a low rate of dislocations combined with a 96% 15-year survival rate. However, late cup migrations have been attributed to their fixation (tripod - exact fit with two pegs and one extraacetabular screw) and the absence of porous coating. In a second-generation device, the designs were modified to achieve press-fit fixation and a layer of titanium beads was sintered on stainless steel cups.
  
  
  OBJECTIVE
  We therefore (1) determined the midterm survival of press-fit, grit-blasted, second-generation cups with or without additional screws, compared with original tripod and (2) compared survival of grit-blasted dual-mobility cups with bimetallic porous-coated cups.
  
  
  METHODS
  From a multiinstitutional trial, we reviewed 2408 patients with osteoarthritis implanted with 2601 prostheses of seven designs of a second-generation dual-mobility cup. The criteria for failure were migration, widening radiolucencies in any zone of the interface, or revision for cup loosening. The minimum followup was 5 years (mean, 7.7 years; range, 5-11 years).
  
  
  RESULTS
  The 8-year survival rate of press-fit, grit-blasted cups was lower than that for press-fit, grit-blasted cups fixed with screws (91% versus 100%) and for tripod fixation (98%). The 8-year survival rate of press-fit, grit-blasted cups was less than that for press-fit, porous-coated cups made of the same alloy (91% versus 95%).
  
  
  CONCLUSIONS
  The data suggested primary fixation of grit-blasted dual-mobility cups should be secured with screws. Porous coating sintered on the convex side improved midterm survivorship. No deleterious effect of metallosis resulted from sintered titanium beads on stainless steel. Long-term followup is required to confirm these findings.
authors.affiliation: Department of Orthopaedic Surgery, Bichat Claude Bernard Hospital, Paris Diderot University, 46 rue Henri Huchard, 75877, Paris Cedex 18, France. philippe.massin@bch.aphp.fr
authors.forename: Philippe
authors.initials: P
authors.lastname: Massin
authors.forename: Vincent
authors.initials: V
authors.lastname: Orain
authors.forename: Rémi
authors.initials: R
authors.lastname: Philippot
authors.forename: Frederic
authors.initials: F
authors.lastname: Farizon
authors.forename: Michel Henry
authors.initials: MH
authors.lastname: Fessy
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation*; D001863:Bone Screws; D002858:Chromium Alloys; D019544:Equipment Failure Analysis; D005260:Female; D005548:Foreign-Body Migration / Q000000981:diagnostic imaging / Q000209:etiology* / Q000601:surgery; D005602:France; D006622:Hip Prosthesis; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000175:diagnosis / Q000601:surgery*; D016062:Porosity; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D012086:Reoperation; D012189:Retrospective Studies; D013193:Stainless Steel; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium; D017211:Treatment Failure
chemical_list: D002858:Chromium Alloys; D013193:Stainless Steel; D014025:Titanium