title: Inpatient pulmonary embolism after elective primary total hip and knee arthroplasty in the United States.
abstract: BACKGROUND
  The incidence of inpatient pulmonary embolism in patients who have elective primary hip and knee arthroplasty in the United States is unknown. Prior studies have included patients with cancer, trauma, or revisions. The goal of this study was to determine the incidence and risks of inpatient pulmonary embolism after elective arthroplasty by type of procedure.
  
  
  METHODS
  We used the 1998 to 2009 Healthcare Cost and Utilization Project Nationwide Inpatient Sample for this retrospective cohort study. Patients who were sixty years of age or older and underwent elective primary total hip or knee arthroplasty were included. The study variable was the type of arthroplasty: total hip, total knee, or two joints. Inpatient pulmonary embolism was the primary outcome; mortality was secondary. Logistic regression determined the adjusted odds ratios of inpatient pulmonary embolism by procedure, adjusting for age, sex, Charlson Comorbidity Index, atrial fibrillation, and surgical indication.
  
  
  RESULTS
  Records represented 5,044,403 hospital discharges after primary total hip or knee arthroplasty. Total knee arthroplasty comprised 66% of the admissions. Less than 5% of patients had two joint procedures. The overall incidence of pulmonary embolism was 0.358% (95% confidence interval [CI], 0.338, 0.378). The incidence of pulmonary embolism differed by procedure and was highest among patients who had two-joint arthroplasty (0.777%; 95% CI, 0.677, 0.876), was lowest in recipients of total hip arthroplasty (0.201%; 95% CI, 0.179, 0.223), and was intermediate in patients who had total knee arthroplasty (0.400%; 95% CI, 0.377, 0.423). The adjusted odds ratios of pulmonary embolism in patients who had two joint procedures were 3.89 times higher than among patients who had total hip arthroplasty, controlling for other factors.
  
  
  CONCLUSIONS
  Elective total knee arthroplasty is associated with a higher incidence and odds of inpatient pulmonary embolism than is total hip arthroplasty; multiple procedures pose the highest risk for pulmonary embolism and associated mortality.
authors.affiliation: Department of Orthopaedics, University of Maryland Medical Center, 11SB, 22 South Greene Street, Baltimore, MD 21201. E-mail address for U. Zahir: Uzahir1980@gmail.com. E-mail address for R.S. Sterling: rsterling@umoa.umm.edu. E-mail address for V.D. Pellegrini: pellegvd@musc.edu.
authors.forename: Usman
authors.initials: U
authors.lastname: Zahir
authors.forename: Robert S
authors.initials: RS
authors.lastname: Sterling
authors.forename: Vincent D
authors.initials: VD
authors.lastname: Pellegrini
authors.forename: Mary L
authors.initials: ML
authors.lastname: Forte
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000706:statistics & numerical data; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000706:statistics & numerical data; D015331:Cohort Studies; D017558:Elective Surgical Procedures / Q000706:statistics & numerical data; D005260:Female; D006760:Hospitalization; D006801:Humans; D015994:Incidence; D008297:Male; D011655:Pulmonary Embolism / Q000453:epidemiology* / Q000209:etiology; D012189:Retrospective Studies; D012307:Risk Factors; D014481:United States / Q000453:epidemiology