title: The epidemiology of revision total hip arthroplasty in the United States.
abstract: BACKGROUND
  Understanding the causes of failure and the types of revision total hip arthroplasty performed is essential for guiding research, implant design, clinical decision-making, and health-care policy. The purpose of the present study was to evaluate the mechanisms of failure and the types of revision total hip arthroplasty procedures performed in the United States with use of newly implemented ICD-9-CM (International Classification of Diseases, Ninth Revision, Clinical Modification) diagnosis and procedure codes related specifically to revision total hip arthroplasty in a large, nationally representative population.
  
  
  METHODS
  The Healthcare Cost and Utilization Project Nationwide Inpatient Sample database was used to analyze clinical, demographic, and economic data from 51,345 revision total hip arthroplasty procedures performed between October 1, 2005, and December 31, 2006. The prevalence of revision procedures was calculated for population subgroups in the United States that were stratified according to age, sex, diagnosis, census region, primary payer class, and type of hospital. The cause of failure, the average length of stay, and total charges were also determined for each type of revision arthroplasty procedure.
  
  
  RESULTS
  The most common type of revision total hip arthroplasty procedure performed was all-component revision (41.1%), and the most common causes of revision were instability/dislocation (22.5%), mechanical loosening (19.7%), and infection (14.8%). Revision total hip arthroplasty procedures were most commonly performed in large, urban, nonteaching hospitals for Medicare patients seventy-five to eighty-four years of age. The average length of hospital stay for all types of revision arthroplasties was 6.2 days, and the average total charges were $54,553. However, the average length of stay, average charges, and procedure frequencies varied considerably according to census region, hospital type, and type of revision total hip arthroplasty procedure performed.
  
  
  CONCLUSIONS
  Hip instability and mechanical loosening are the most common indications for revision total hip arthroplasty in the United States. As further experience is gained with the new diagnosis and procedure codes specifically related to revision total hip arthroplasty, this information will be valuable in directing future research, implant design, and clinical decision-making.
authors.affiliation: Department of Orthopaedic Surgery and Philip R. Lee Institute for Health Policy Studies, University of California, San Francisco, 500 Parnassus Avenue, MU 320W, San Francisco, CA 94143-0278, USA. bozick@orthosurg.ucsf.edu
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Bozic
authors.forename: Steven M
authors.initials: SM
authors.lastname: Kurtz
authors.forename: Edmund
authors.initials: E
authors.lastname: Lau
authors.forename: Kevin
authors.initials: K
authors.lastname: Ong
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Vail
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Berry
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007902:Length of Stay / Q000706:statistics & numerical data; D008297:Male; D015995:Prevalence; D012086:Reoperation; D016896:Treatment Outcome; D014481:United States / Q000453:epidemiology