title: Have bilateral total knee arthroplasties become safer? A population-based trend analysis.
abstract: BACKGROUND
  Studies suggest a trend in the selection of younger and healthier individuals to undergo bilateral TKAs in an attempt to diminish the incidence of complications. It remains unclear whether this development has reduced overall perioperative morbidity and mortality.
  
  
  OBJECTIVE
  We investigated whether changes in demographics and comorbidity patterns of patients undergoing bilateral TKAs are detectable and coincide with changes in length and cost of hospitalization, incidence of perioperative complications, morbidity, and mortality.
  
  
  METHODS
  We accessed Nationwide Inpatient Survey data files between 1999 and 2008. One-year periods were created and changes in demographics, length of in-hospital stay, and perioperative morbidity and mortality were analyzed.
  
  
  RESULTS
  An estimated 258,524 bilateral TKAs were performed between 1999 and 2008 in the United States. The number of annual procedures increased from 19,288 to 33,679 (75%). Length of hospital stay decreased from 4.98 to 4.01 days. Absolute in-hospital mortality rates decreased at an average rate of 10% per year. The unadjusted percent and adjusted incidence per 1000 inpatient days decreased from 0.42% and 0.85 to 0.16% and 0.39. Although the unadjusted incidence of pneumonia, pulmonary embolism, and nonmyocardial infarction cardiac complications did not change, an increase with time was detectible after adjustment for length of stay. No changes in adjusted incidence were seen for other complications.
  
  
  CONCLUSIONS
  Although a decreased incidence was seen for some major complications, others either remained unchanged or had an increased incidence when adjusted for length of stay. Future interventions should focus on reducing perioperative risk to improve patient safety.
authors.affiliation: Department of Anesthesiology, Hospital for Special Surgery, Weill Medical College of Cornell University, 535 East 70th Street, New York, NY 10021, USA. memtsoudiss@hss.edu
authors.forename: Stavros G
authors.initials: SG
authors.lastname: Memtsoudis
authors.forename: Carlos B
authors.initials: CB
authors.lastname: Mantilla
authors.forename: Javad
authors.initials: J
authors.lastname: Parvizi
authors.forename: Ottokar
authors.initials: O
authors.lastname: Stundner
authors.forename: Madhu
authors.initials: M
authors.lastname: Mazumdar
mesh_terms: D000367:Age Factors; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000401:mortality / Q000639:trends*; D005260:Female; D017052:Hospital Mortality / Q000639:trends; D006801:Humans; D015994:Incidence; D007902:Length of Stay / Q000706:statistics & numerical data / Q000639:trends; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000453:epidemiology*; D015995:Prevalence; D012189:Retrospective Studies; D012307:Risk Factors; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology