title: Factors influencing regional variability in the rate of total knee arthroplasty.
abstract: OBJECTIVE
  Geographic variations in knee arthroplasty have been detected through international surveys. We aim to investigate in this study the influence of aging index, health budget, and number of orthopedic surgeons in the regional variations of the primary and revision TKA rate in a single European country, Spain.
  
  
  METHODS
  Inpatient database of knee arthroplasty procedures for years 1997 to 2010 was obtained from the Spanish Ministry of Health, including 393,714 primaries and 37,037 revisions, segregated for each of the 17 regional health services in Spain. Crude and adjusted rates (direct method with total Spanish population per year) were calculated and used as dependent variables. Aging index, regional health budget, and number of orthopedic surgeons per region were used as independent variables in a Kruskal-Wallis test and a negative binomial regression analysis model.
  
  
  CONCLUSIONS
  With a mean crude rate for Spain of 76 primary TKA and 7 revision surgeries per 10(5) population and year, the mean adjusted rate per region oscillated between 702 and 27 primary TKA and 87 and 3 revisions per 10(5). A model was adjusted confirming the influence of aging index, health budget, and number of surgeons, but regional variations remained partly unexplained by these factors.
authors.affiliation: Department of Orthopaedic Surgery, Hospital La Paz, Autónoma University of Madrid, Madrid, Spain; IDIPAZ, Research Institute at Hospital La Paz and Autónoma University of Madrid, Madrid, Spain. Electronic address: enrique.gomezbarrena@uam.es.
authors.forename: E
authors.initials: E
authors.lastname: Gómez-Barrena
authors.affiliation: IDIPAZ, Research Institute at Hospital La Paz and Autónoma University of Madrid, Madrid, Spain.
authors.forename: N G
authors.initials: NG
authors.lastname: Padilla-Eguiluz
authors.affiliation: Department of Orthopaedic Surgery, Hospital La Paz, Autónoma University of Madrid, Madrid, Spain; IDIPAZ, Research Institute at Hospital La Paz and Autónoma University of Madrid, Madrid, Spain.
authors.forename: E
authors.initials: E
authors.lastname: García-Rey
authors.affiliation: Department of Orthopaedic Surgery, Hospital La Princesa, Autónoma University of Madrid, Madrid, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Cordero-Ampuero
authors.affiliation: Department of Orthopaedic Surgery, Hospital La Paz, Autónoma University of Madrid, Madrid, Spain; IDIPAZ, Research Institute at Hospital La Paz and Autónoma University of Madrid, Madrid, Spain.
authors.forename: E
authors.initials: E
authors.lastname: García-Cimbrelo
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000367:Age Factors; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000706:statistics & numerical data*; D002017:Budgets; D016208:Databases, Factual; D005260:Female; D005102:Health Expenditures; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D010820:Physicians / Q000600:supply & distribution; D012041:Regional Medical Programs / Q000191:economics; D012086:Reoperation / Q000706:statistics & numerical data; D017678:Sex Distribution; D013030:Spain / Q000453:epidemiology; D055815:Young Adult
keywords: Epidemiology; Knee arthroplasty rate; Regional variations; TKA