title: Medical comorbidities are independent preoperative risk factors for surgical infection after total joint arthroplasty.
abstract: BACKGROUND
  Surgical site infection (SSI) after total joint arthroplasty (TJA) is a major cause of morbidity. Multiple patient comorbidities have been identified as SSI risk factors including obesity, tobacco use, diabetes, immunosuppression, malnutrition, and coagulopathy. However, the independent effect of multiple individual patient factors on risk of subsequent periprosthetic infection is unclear.
  
  
  OBJECTIVE
  The purposes of this study are (1) to collect data on several preestablished infection risk factors in addition to SSI-related data on a large TJA cohort; and (2) to use multivariate modeling on previously established patient risk factors to determine independent preoperative predictors of SSI.
  
  
  METHODS
  We reviewed records of patients undergoing TJA from January 1, 2010, to July 30, 2012. Confirmation of SSI followed published guidelines for superficial, deep, and periprosthetic. A total of 29 culture-positive SSIs (1.5% total) and 1846 controls were identified. The prevalence of known patient-specific infection risk factors was determined for both infected cases and healthy control subjects followed by multiple regression analysis to determine independent risk.
  
  
  RESULTS
  Isolated organisms consisted of methicillin-resistant Staphylococcus aureus (MRSA; 34.5%) followed by gram-negative rods (31.0%). After adjusting for anatomic site, independent risk factors for infection include: revision surgery (odds ratio [OR], 2.28; confidence interval [CI], 1.26-3.98), super obesity (body mass index>50 kg/m2; OR, 5.28; CI, 1.38-17.1), diabetes mellitus (OR, 1.83; CI, 1.02-3.27), tobacco abuse (OR, 2.96; CI, 1.65-5.11), MRSA colonization or infection (OR, 4.17; CI, 1.63-9.66), and current or prior bone cancer (OR, 3.86; CI, 1.21-12.79).
  
  
  CONCLUSIONS
  Multiple patient comorbidities independently contribute to infection risk after TJA. Preoperative TJA infection risk stratification may be feasible and should be investigated further.
  
  
  METHODS
  Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedics, The Ohio State University Wexner Medical Center, 725 Prior Hall 376 West 10th Avenue, Columbus, OH, 43210, USA.
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Everhart
authors.forename: Eric
authors.initials: E
authors.lastname: Altneu
authors.forename: Jason H
authors.initials: JH
authors.lastname: Calhoun
mesh_terms: D019643:Arthroplasty, Replacement / Q000009:adverse effects*; D003924:Diabetes Mellitus, Type 2 / Q000150:complications; D005260:Female; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification; D009765:Obesity / Q000150:complications; D011379:Prognosis; D012086:Reoperation; D012307:Risk Factors; D013530:Surgical Wound Infection / Q000150:complications / Q000209:etiology*