title: Total knee arthroplasty volume, utilization, and outcomes among Medicare beneficiaries, 1991-2010.
abstract: BACKGROUND
  Total knee arthroplasty (TKA) is one of the most common and costly surgical procedures performed in the United States.
  
  
  OBJECTIVE
  To examine longitudinal trends in volume, utilization, and outcomes for primary and revision TKA between 1991 and 2010 in the US Medicare population.
  
  
  METHODS
  Observational cohort of 3,271,851 patients (aged ≥65 years) who underwent primary TKA and 318 563 who underwent revision TKA identified in Medicare Part A data files.
  
  
  METHODS
  We examined changes in primary and revision TKA volume, per capita utilization, hospital length of stay (LOS), readmission rates, and adverse outcomes.
  
  
  RESULTS
  Between 1991 and 2010 annual primary TKA volume increased 161.5% from 93,230 to 243,802 while per capita utilization increased 99.2% (from 31.2 procedures per 10,000 Medicare enrollees in 1991 to 62.1 procedures per 10,000 in 2010). Revision TKA volume increased 105.9% from 9650 to 19,871 while per capita utilization increased 59.4% (from 3.2 procedures per 10,000 Medicare enrollees in 1991 to 5.1 procedures per 10,000 in 2010). For primary TKA, LOS decreased from 7.9 days (95% CI, 7.8-7.9) in 1991-1994 to 3.5 days (95% CI, 3.5-3.5) in 2007-2010 (P < .001). For primary TKA, rates of adverse outcomes resulting in readmission remained stable between 1991-2010, but rates of all-cause 30-day readmission increased from 4.2% (95% CI, 4.1%-4.2%) to 5.0% (95% CI, 4.9%-5.0%) (P < .001). For revision TKA, the decrease in hospital LOS was accompanied by an increase in all-cause 30-day readmission from 6.1% (95% CI, 5.9%-6.4%) to 8.9% (95% CI, 8.7%-9.2%) (P < .001) and an increase in readmission for wound infection from 1.4% (95% CI, 1.3%-1.5%) to 3.0% (95% CI, 2.9%-3.1%) (P < .001).
  
  
  CONCLUSIONS
  Increases in TKA volume have been driven by both increases in the number of Medicare enrollees and in per capita utilization. We also observed decreases in hospital LOS that were accompanied by increases in hospital readmission rates.
authors.affiliation: Division of General Internal Medicine, Department of Internal Medicine, University of Iowa Carver College of Medicine, 200 Hawkins Dr, 6GH SE, Iowa City, IA 52242, USA. peter-cram@uiowa.edu
authors.forename: Peter
authors.initials: P
authors.lastname: Cram
authors.forename: Xin
authors.initials: X
authors.lastname: Lu
authors.forename: Stephen L
authors.initials: SL
authors.lastname: Kates
authors.forename: Jasvinder A
authors.initials: JA
authors.lastname: Singh
authors.forename: Yue
authors.initials: Y
authors.lastname: Li
authors.forename: Brian R
authors.initials: BR
authors.lastname: Wolf
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data*; D008137:Longitudinal Studies; D008297:Male; D006278:Medicare / Q000706:statistics & numerical data*; D010359:Patient Readmission / Q000706:statistics & numerical data*; D011183:Postoperative Complications / Q000453:epidemiology; D012086:Reoperation / Q000706:statistics & numerical data; D016896:Treatment Outcome; D014481:United States