title: Development and Validation of a Preoperative Surgical Site Infection Risk Score for Primary or Revision Knee and Hip Arthroplasty.
abstract: BACKGROUND
  Surgical site infection (SSI) is a major complication following total joint arthroplasty. Host susceptibility to infection has emerged as an important predictor of SSI. The purpose of this study was to develop and validate a preoperative SSI risk-assessment tool for primary or revision knee and hip arthroplasty.
  
  
  METHODS
  Data for 6,789 patients who underwent total joint arthroplasty (from the years 2000 to 2011) were obtained from a single hospital system. SSI was defined as a superficial infection within 30 days or deep infection within 1 year. Logistic regression modeling was utilized to create a risk scoring system for a derivation sample (n = 5,789; 199 SSIs), with validation performed on a hold-out sample (a subset of observations chosen randomly from the initial sample to form a testing set; n = 1,000; 41 SSIs).
  
  
  RESULTS
  On the basis of logistic regression modeling, we created a scoring system to assess SSI risk (range, 0 to 35 points) that is the point sum of the following: primary hip arthroplasty (0 points); primary knee (1); revision hip (3); revision knee (3); non-insulin-dependent diabetes (1); insulin-dependent diabetes (1.5); chronic obstructive pulmonary disease (COPD) (1); inflammatory arthropathy (1.5); tobacco use (1.5); lower-extremity osteomyelitis or pyogenic arthritis (2); pelvis, thigh, or leg traumatic fracture (2); lower-extremity pathologic fracture (2.5); morbid obesity (2.5); primary bone cancer (4); reaction to prosthesis in the last 3 years (4); and history of staphylococcal septicemia (4.5). The risk score had good discriminatory capability (area under the ROC [receiver operating characteristic] curve = 0.77) and calibration (Hosmer-Lemeshow chi-square test, p = 0.34) and was validated using the independent sample (area under the ROC curve = 0.72). A small subset of patients (5.9%) had a >10% estimated infection risk.
  
  
  CONCLUSIONS
  The patient comorbidities composing the risk score heavily influenced SSI risk for primary or revision knee and hip arthroplasty. We believe that infection risk can be objectively determined in a preoperative setting with the proposed SSI risk score.
authors.affiliation: Department of Orthopaedics, Wexner Medical Center, The Ohio State University, Columbus, Ohio.
authors.forename: Joshua S
authors.initials: JS
authors.lastname: Everhart
authors.affiliation: Division of Biostatistics, College of Public Health, The Ohio State University, Columbus, Ohio.
authors.forename: Rebecca R
authors.initials: RR
authors.lastname: Andridge
authors.affiliation: Department of Orthopaedics, Wexner Medical Center, The Ohio State University, Columbus, Ohio.
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Scharschmidt
authors.affiliation: Department of Orthopaedics, Wexner Medical Center, The Ohio State University, Columbus, Ohio.
authors.forename: Joel L
authors.initials: JL
authors.lastname: Mayerson
authors.affiliation: Department of Orthopaedics, Wexner Medical Center, The Ohio State University, Columbus, Ohio andrew.glassman@osumc.edu.
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Glassman
authors.affiliation: Division of Biostatistics, College of Public Health, The Ohio State University, Columbus, Ohio.
authors.forename: Stanley
authors.initials: S
authors.lastname: Lemeshow
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012086:Reoperation; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000209:etiology; D013290:Streptococcal Infections / Q000209:etiology; D013530:Surgical Wound Infection / Q000209:etiology*