title: Early postoperative mortality after simultaneous or staged bilateral primary total hip arthroplasty: an observational register study from the Swedish Hip Arthroplasty Register.
abstract: BACKGROUND
  Approximately a fifth of all total hip arthroplasty (THA) patients suffers from bilateral osteoarthritis of the hip. It is unclear whether mortality risks differ between simultaneous bilateral THA and staged bilateral THA. We investigated mortality after simultaneous THA compared with staged bilateral THA in the largest cohort hitherto reported.
  
  
  METHODS
  The 42,238 patients reported to have received bilateral primary THA from 1992 to 2012 in the Swedish Hip Arthroplasty Register were included. Tumours and fractures as underlying diagnoses were excluded. The time interval between the first and second THA was divided into four categories or treated as a continuous variable. Unadjusted survival was calculated according to Kaplan-Meier and adjusted Cox regression models were fitted in order to calculate crude and adjusted hazard ratios (HR) for the risk of death within different time frames.
  
  
  RESULTS
  Patients selected for simultaneous bilateral surgery were younger, more often male, and had lower ASA (American Society of Anesthesiologists) class than patients receiving staged procedures. The adjusted 90-day mortality after the second procedure did not differ between the four investigated groups (simultaneous bilateral [HR 1.3, CI 0.5-3.3], surgeries within 6 months [HR 1.1, CI 0.6-2.0], surgeries between 7 and 12 months [HR 0.7, CI 0.4-1.2], with second surgery after >12 months as the reference group). For patients older than 75 years, men, patients with ASA class 3 or above, and for patients with rheumatoid arthritis (RA) the 90-day mortality was increased. The unadjusted risk of implant revision of any hip was slightly higher for patients with simultaneous bilateral THA compared to those with staged procedure within one year, but after adjustment for age, gender, diagnosis and implant fixation these differences were no longer statistically significant.
  
  
  CONCLUSIONS
  There were no clinically relevant differences in early postoperative mortality between simultaneous and staged bilateral surgery in healthy patients. Advanced age, RA, a high ASA class and male sex increased the risk of death within 90 days. There may be an issue with enhanced risk of implant revision in patients with simultaneous bilateral THA that needs to be explored further.
authors.affiliation: Department of Orthopaedics, Visby Hospital, Visby, Sweden. anne.garland@gotland.se.|Swedish Hip Arthroplasty Register, Gothenburg, Sweden. anne.garland@gotland.se.|Department of Orthopaedics, Institute of Surgical Sciences, Uppsala University Hospital, Uppsala, Sweden. anne.garland@gotland.se.
authors.forename: Anne
authors.initials: A
authors.lastname: Garland
authors.affiliation: Swedish Hip Arthroplasty Register, Gothenburg, Sweden. ola.rolfson@vgregion.se.|Department of Orthopaedics, Institute of Clinical Sciences, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. ola.rolfson@vgregion.se.|Harris Orthopaedic Laboratory, Massachusetts General Hospital, Harvard Medical School, Boston, USA. ola.rolfson@vgregion.se.
authors.forename: Ola
authors.initials: O
authors.lastname: Rolfson
authors.affiliation: Swedish Hip Arthroplasty Register, Gothenburg, Sweden. goran.garellick@registercentrum.se.|Department of Orthopaedics, Institute of Clinical Sciences, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. goran.garellick@registercentrum.se.
authors.forename: Göran
authors.initials: G
authors.lastname: Garellick
authors.affiliation: Swedish Hip Arthroplasty Register, Gothenburg, Sweden. johan.karrholm@vgregion.se.|Department of Orthopaedics, Institute of Clinical Sciences, The Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden. johan.karrholm@vgregion.se.
authors.forename: Johan
authors.initials: J
authors.lastname: Kärrholm
authors.affiliation: Swedish Hip Arthroplasty Register, Gothenburg, Sweden. nils.hailer@surgsci.uu.se.|Department of Orthopaedics, Institute of Surgical Sciences, Uppsala University Hospital, Uppsala, Sweden. nils.hailer@surgsci.uu.se.
authors.forename: Nils P
authors.initials: NP
authors.lastname: Hailer
mesh_terms: D000367:Age Factors; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000379:methods* / Q000401:mortality* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D015207:Osteoarthritis, Hip / Q000453:epidemiology* / Q000601:surgery*; D011184:Postoperative Period; D012042:Registries; D012044:Regression Analysis; D012189:Retrospective Studies; D012307:Risk Factors; D012737:Sex Factors; D015996:Survival Rate; D013548:Sweden / Q000453:epidemiology; D013997:Time Factors