title: Positive Culture During Reimplantation Increases the Risk of Subsequent Failure in Two-Stage Exchange Arthroplasty.
abstract: BACKGROUND
  It is strongly recommended that tissue and synovial fluid culture samples be obtained during reimplantation performed as part of a 2-stage exchange arthroplasty. The rate of positive cultures during reimplantation and the influence of positive cultures on subsequent outcomes, to our knowledge, are unknown. This study was designed to determine the rate of positive cultures during reimplantation and to investigate the association between positive cultures at reimplantation and subsequent outcomes.
  
  
  METHODS
  We retrospectively reviewed the data of 259 patients who met the Musculoskeletal Infection Society criteria for periprosthetic joint infection (PJI) and who underwent both stages of 2-stage exchange arthroplasty at our institution from 1999 to 2013. Among these patients were 267 PJIs (186 knees and 81 hips); 33 (12.4%) had ≥1 positive culture result at reimplantation. Treatment failure was assessed according to the Delphi-based consensus definition. Logistic regression analysis was performed to assess the predictors of positive culture and risk factors for failure of 2-stage exchange arthroplasty.
  
  
  RESULTS
  Of the 33 cases with PJI, 15 (45.5%) had a subsequent failure of the 2-stage exchange arthroplasty compared with 49 (20.9%) of the cases that were culture-negative at reimplantation. When controlling for other variables using multivariate analyses, the risk of treatment failure was higher (odds ratio = 2.53; 95% confidence interval [CI] = 1.13 to 5.64) and reinfection occurred earlier (hazard ratio = 2.00; 95% CI = 1.05 to 3.82) for the cases with a positive culture during reimplantation. The treatment failure rate did not differ (p = 0.73) between cases with ≥2 positive cultures (36.4%) and 1 positive culture (50%).
  
  
  CONCLUSIONS
  Positive intraoperative culture at the time of reimplantation, regardless of the number of positive samples, was independently associated with >2 times the risk of subsequent treatment failure and earlier reinfection. Surgeons should be aware that a positive culture at the time of reimplantation independently increases the risk of subsequent failure.
  
  
  METHODS
  Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Rothman Institute, Philadelphia, Pennsylvania.
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Tan
authors.affiliation: Rothman Institute, Philadelphia, Pennsylvania.
authors.forename: Miguel M
authors.initials: MM
authors.lastname: Gomez
authors.affiliation: Rothman Institute, Philadelphia, Pennsylvania.
authors.forename: Jorge
authors.initials: J
authors.lastname: Manrique
authors.affiliation: Rothman Institute, Philadelphia, Pennsylvania parvj@aol.com.
authors.forename: Javad
authors.initials: J
authors.lastname: Parvizi
authors.affiliation: Rothman Institute, Philadelphia, Pennsylvania.
authors.forename: Antonia F
authors.initials: AF
authors.lastname: Chen
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000379:methods; D005260:Female; D006801:Humans; D007720:Knee Prosthesis / Q000009:adverse effects*; D008297:Male; D008875:Middle Aged; D016459:Prosthesis-Related Infections / Q000209:etiology*; D012086:Reoperation; D012092:Replantation; D012307:Risk Factors; D017211:Treatment Failure