title: Should national standards for reporting surgical site infections distinguish between primary and revision orthopedic surgeries?
abstract: OBJECTIVE
  To compare the surgical site infection (SSI) rate after primary total hip arthroplasty with the SSI rate after revision total hip arthroplasty.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  Mayo Clinic in Rochester, Minnesota, a referral orthopedic center.
  
  
  METHODS
  All patients undergoing primary total hip arthroplasty or revision total hip arthroplasty during the period from January 1, 2002, through December 31, 2006.
  
  
  METHODS
  We obtained data on total hip arthroplasties from a prospectively maintained institutional surgical database. We reviewed data on SSIs collected prospectively as part of routine infection control surveillance, using the criteria of the Centers for Disease Control and Prevention for the definition of an SSI. We used logistic regression analyses to evaluate differences between the SSI rate after primary total hip arthroplasty and the SSI rate after revision total hip arthroplasty.
  
  
  RESULTS
  A total of 5,696 total hip arthroplasties (with type 1 wound classification) were analyzed, of which 1,381 (24%) were revisions. A total of 61 SSIs occurred, resulting in an overall SSI rate of 1.1% for all total hip arthroplasties. When stratified by the National Nosocomial Infection Surveillance (NNIS) risk index, SSI rates were 0.5%, 1.2%, and 1.6% in risk categories 0, 1, and 2, respectively. After controlling for the NNIS risk index, the risk of SSI after revision total hip arthroplasty was twice as high as that after primary total hip arthroplasty (odds ratio, 2.2 [95% confidence interval, 1.3-3.7]). In the analysis restricted to the development of deep incisional or organ space infections, the risk of SSI after revision total hip arthroplasty was nearly 4 times that after primary total hip arthroplasty (odds ratio, 3.9 [95% confidence interval, 2.0-7.6]).
  
  
  CONCLUSIONS
  Including revision surgeries in the calculation of SSI rates can result in higher infection rates for institutions that perform a larger number of revisions. Taking NNIS risk indices into account does not eliminate this effect. Differences between primary and revision surgeries should be considered in national standards for the reporting of SSIs.
authors.affiliation: Division of Infectious Diseases, College of Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA. leekha.surbhi@mayo.edu
authors.forename: Surbhi
authors.initials: S
authors.lastname: Leekha
authors.forename: Priya
authors.initials: P
authors.lastname: Sampathkumar
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Berry
authors.forename: Rodney L
authors.initials: RL
authors.lastname: Thompson
mesh_terms: D000046:Academic Medical Centers / Q000706:statistics & numerical data; D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects / Q000592:standards / Q000706:statistics & numerical data; D002487:Centers for Disease Control and Prevention, U.S. / Q000592:standards*; D015331:Cohort Studies; D016208:Databases, Factual; D005260:Female; D006801:Humans; D017053:Infection Control / Q000379:methods; D008297:Male; D019221:Mandatory Reporting; D008875:Middle Aged; D008910:Minnesota; D012086:Reoperation / Q000009:adverse effects / Q000592:standards / Q000706:statistics & numerical data; D012189:Retrospective Studies; D018571:Sentinel Surveillance; D013530:Surgical Wound Infection / Q000453:epidemiology* / Q000517:prevention & control; D014481:United States