title: Rates and outcomes of primary and revision total hip replacement in the United States medicare population.
abstract: BACKGROUND
  Information on the epidemiology of primary total hip replacement is limited, and we are not aware of any reports on the epidemiology of revision total hip replacement. The objective of this study was to characterize the rates and immediate postoperative outcomes of primary and revision total hip replacement in persons sixty-five years of age and older residing in the United States.
  
  
  METHODS
  We used Medicare claims submitted by hospitals, physicians, and outpatient facilities between July 1, 1995, and June 30, 1996, to identify individuals who had undergone elective primary total hip replacement for a reason other than a fracture (61,568 patients) or had had revision total hip replacement (13,483 patients). Annual incidence rates of primary and revision total hip replacement were calculated, and multivariate modeling was used to evaluate the association between patient characteristics and surgical rates. The rates of occurrence of five complications within ninety days postoperatively were also evaluated, and relationships between those outcomes and patient characteristics were assessed with use of multivariate models adjusted for hospital and surgeon volume.
  
  
  RESULTS
  The rates of primary total hip replacement were three to six times higher than the rates of revision total hip replacement. Women had higher rates than men, and whites had higher rates than blacks. The rates of primary and revision total hip replacement increased with age until the age of seventy-five to seventy-nine years and then declined. The rates of complications occurring within ninety days after primary total hip replacement were 1.0% for mortality, 0.9% for pulmonary embolus, 0.2% for wound infection, 4.6% for hospital readmission, and 3.1% for hip dislocation. The rates after revision total hip replacement were 2.6%, 0.8%, 0.95%, 10.0%, and 8.4%, respectively. Factors associated with an increased risk of an adverse outcome included increased age, gender (men were at higher risk than women), race (blacks were at higher risk than whites), a medical comorbidity, and a low income.
  
  
  CONCLUSIONS
  Analysis of United States Medicare population data showed that the rates of total hip replacement increased with age up to the age of seventy-five to seventy-nine years and that blacks had a significantly lower rate of total hip replacement than whites. The overall rates of adverse outcomes were relatively low, but they were significantly higher after revision than after primary total hip replacement.
  
  
  METHODS
  Prognostic study, Level II-1 (retrospective study). See p. 2 for complete description of levels of evidence.
authors.affiliation: Toronto Western Hospital, ON, Canada. nizar.mahomed@utoronto.ca
authors.forename: Nizar N
authors.initials: NN
authors.lastname: Mahomed
authors.forename: Jane A
authors.initials: JA
authors.lastname: Barrett
authors.forename: Jeffrey N
authors.initials: JN
authors.lastname: Katz
authors.forename: Charlotte B
authors.initials: CB
authors.lastname: Phillips
authors.forename: Elena
authors.initials: E
authors.lastname: Losina
authors.forename: Robert A
authors.initials: RA
authors.lastname: Lew
authors.forename: Edward
authors.initials: E
authors.lastname: Guadagnoli
authors.forename: William H
authors.initials: WH
authors.lastname: Harris
authors.forename: Robert
authors.initials: R
authors.lastname: Poss
authors.forename: John A
authors.initials: JA
authors.lastname: Baron
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects* / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D015994:Incidence; D007592:Joint Diseases / Q000453:epidemiology* / Q000601:surgery*; D008297:Male; D006278:Medicare / Q000706:statistics & numerical data*; D015999:Multivariate Analysis; D017063:Outcome Assessment, Health Care / Q000706:statistics & numerical data*; D011183:Postoperative Complications / Q000453:epidemiology; D012086:Reoperation / Q000009:adverse effects* / Q000706:statistics & numerical data*; D013997:Time Factors; D014481:United States / Q000453:epidemiology