title: Double mobility cup total hip arthroplasty in patients at high risk for dislocation: a single-center analysis.
abstract: BACKGROUND
  Double mobility cup systems (DMCS) have gained increasing acceptance, especially in patients at high risk for dislocation. The aim of this investigation was to analyze the frequency and indications of the DMCS use in our praxis and to evaluate dislocation and cup revision rates after a minimum follow-up of 2 years.
  
  
  METHODS
  All patients implanted with a DMCS from May 2008 to August 2011 were identified from our institutional database of primary and revision THA procedures. Patient demographics, including ASA score, were recorded, along with details of the surgical procedures, indications for DMCS use, and post-operative clinical course and any complications. Radiographs were analyzed for implant positioning and radiological signs of loosening.
  
  
  RESULTS
  1046 primary THA were implanted, of these 39 (4 %) primary DMCS. Indications were severe neuromuscular disease (SND) (14), hip abductor degeneration (HAD) (9), cognitive dysfunction (CD) (8) and others. 345 revision THA were performed, of these 50 (14 %) revision DMCS. Indications were recurrent dislocations (27), multiple prior hip surgeries (13), HAD (5), CD (3) and others. Overall dislocation rate was 2/89 (2 %); both in revision THA. Overall cup revision rate was 5/89 (6 %): 3 septic, 1 periprosthetic acetabular fracture, 1 "intraprosthetic dissociation". 67 patients were available for the standardized questionnaire at a median follow-up of 43 months (range 25-78). 19 patients were not available for two-year follow-up: 17 died and two were lost to follow-up.
  
  
  CONCLUSIONS
  This study supports the use of DMCS constructs in primary and revision hip arthroplasty for specific high-risk patients. We continue to indicate DMCS in this patient group. We do caution against extending indications for DMCS to lower risk patient groups due to unknown issues surrounding wear and component longevity.
authors.affiliation: Uniklinik Balgrist, Forchstrasse 340, 8008, Zurich, Switzerland. dominik14k@gmail.com.
authors.forename: Dominik
authors.initials: D
authors.lastname: Kaiser
authors.affiliation: Uniklinik Balgrist, Forchstrasse 340, 8008, Zurich, Switzerland.
authors.forename: Atul F
authors.initials: AF
authors.lastname: Kamath
authors.affiliation: Uniklinik Balgrist, Forchstrasse 340, 8008, Zurich, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Zingg
authors.affiliation: Uniklinik Balgrist, Forchstrasse 340, 8008, Zurich, Switzerland.
authors.forename: Claudio
authors.initials: C
authors.lastname: Dora
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006617:Hip Dislocation / Q000209:etiology / Q000517:prevention & control*; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D057068:Periprosthetic Fractures / Q000150:complications / Q000517:prevention & control*; D011474:Prosthesis Design; D012086:Reoperation; D012189:Retrospective Studies; D012307:Risk Factors; D055815:Young Adult
keywords: Complications; Dislocation; Double cup mobility system; Primary; Revision; Total hip arthroplasty