title: Dual Mobility Acetabular Cups in Primary Total Hip Arthroplasty in Patients at High Risk for Dislocation.
abstract: BACKGROUND
  Postoperative dislocation occurs in approximately 2% of primary total hip arthroplasties (THAs). Risk factors associated with dislocation include: age of 70 years or older, body mass index (BMI) of 30 kg/m2 or greater, alcohol abuse, and neuro-degenerative diseases such as multiple sclerosis or Parkinson's disease. As a result, dual-mobility articulations, which have been typically used for revision procedures, have become an increasingly popular option for these "at risk" primary THAs. Few studies have assessed their use in this complex patient population. Therefore, the purpose of this study was to assess: 1) survivorship; 2) radiographic outcomes (cup migration, progressive radiolucencies, and changes in component position); 3) Harris Hip Scores; and 4) complications of the dual-mobility articulation in the setting of primary THA for patients at high risk for dislocation.
  
  
  METHODS
  Five participating surgeons performed 495 primary cementless THAs between January 2011 and December 2013. During this time, four of the five surgeons used dual-mobility articulations whenever the acetabular cup size was 52 mm or greater to allow for a 28 mm head, while one surgeon used it when the cup size was less than 52 mm to allow for an effective head size of 38 mm. The remaining surgeon used it for all THAs. Of the 495 patients, 453 (92%) received dual-mobility articulations, of which, 43 patients (10%) were lost to follow-up before the two year minimum. The remaining 410 patients were further assessed to determine those who were considered high risk for dislocation (age = 70 years, BMI =30 kg/m2, had a diagnosis of alcohol abuse, or had a neuro-degenerative disorder). Two hundred forty-nine patients were included in the analysis (103 men, 146 women) who had a mean age of 66 years (range, 24 to 90 years). The mean follow-up was 3.3 years (range, 2 to 5 years). Kaplan-Meier analysis was performed to assess aseptic and all-cause acetabular cup survivorship. Radiographs were evaluated for cup migration, progressive radiolucencies, and any changes in component position. Clinical outcomes were assessed using the Harris Hip Score (HHS), and any surgery-related complications were recorded.
  
  
  RESULTS
  The survivorship to aseptic failure (n= 1) and all-cause (aseptic, n= 1; septic, n= 1) Kaplan-Meier acetabular component survivorships were 99.6% (95% confidence interval [CI], 99.1% to 99.9%) and 99.2% (95% CI, 98.5% to 99.9%), respectively. One hip had impingement of an anteverted cup, resulting in trunnion notching, and required revision of the cup and stem. Another hip had a deep infection, which was treated with a two-stage revision procedure. There were no dislocations in this cohort. No progressive radiolucencies or component positional changes were seen on radiographic assessment. Patients reported a mean HHS of 92.5 (range, 47 to 100 points) at final follow-up. Surgical complications included one polyethylene liner that was incompletely seated, and one loose femoral stem, which required revision of only the femoral component.
  
  
  CONCLUSIONS
  At short-term follow-up, dual-mobility articulations in primary THA offer survivorship, outcomes, and complications comparable to conventional THA designs in patients who are at increased risk for postoperative dislocation. Serious complications, such as polyethylene wear and intraprosthetic dislocations, have occasionally been reported with the use of these components. Therefore, future studies should be prospective, multi-center, and have longer-term follow-up to determine the true benefit of modular dual-mobility articulations in patients who are at high risk for dislocation.
authors.affiliation: Center for Reconstructive Joint Surgery, Mount Sinai Beth Israel Medical Center, New York, New York.
authors.forename: Steven F
authors.initials: SF
authors.lastname: Harwin
authors.affiliation: Rubin Institute for Advanced Orthopedics, Center for Joint Preservation and Replacement, Sinai Hospital of Baltimore, Baltimore, Maryland.
authors.forename: Jaydev B
authors.initials: JB
authors.lastname: Mistry
authors.affiliation: Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Morad
authors.initials: M
authors.lastname: Chughtai
authors.affiliation: Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Anton
authors.initials: A
authors.lastname: Khlopas
authors.affiliation: Rubin Institute for Advanced Orthopedics, Center for Joint Preservation and Replacement, Sinai Hospital of Baltimore, Baltimore, Maryland.
authors.forename: Chukwuweike
authors.initials: C
authors.lastname: Gwam
authors.affiliation: Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Jared M
authors.initials: JM
authors.lastname: Newman
authors.affiliation: Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Carlos A
authors.initials: CA
authors.lastname: Higuera
authors.affiliation: Bonutti Clinic, Effingham, Illinois.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Bonutti
authors.affiliation: Orthopaedic Surgery Department, University of Louisville, Louisville, Kentucky.
authors.forename: Arthur L
authors.initials: AL
authors.lastname: Malkani
authors.affiliation: OrthoIndy, Greenwood, Indiana.
authors.forename: Frank R
authors.initials: FR
authors.lastname: Kolisek
authors.affiliation: Rubin Institute for Advanced Orthopedics, Center for Joint Preservation and Replacement, Sinai Hospital of Baltimore, Baltimore, Maryland.
authors.forename: Ronald E
authors.initials: RE
authors.lastname: Delanois
authors.affiliation: Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Mont
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000295:instrumentation / Q000706:statistics & numerical data; D005260:Female; D006622:Hip Prosthesis / Q000009:adverse effects / Q000706:statistics & numerical data; D006801:Humans; D053208:Kaplan-Meier Estimate; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000453:epidemiology*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012307:Risk Factors; D055815:Young Adult