title: Association between hospital and surgeon procedure volume and outcomes of total hip replacement in the United States medicare population.
abstract: BACKGROUND
  The mortality and complication rates of many surgical procedures are inversely related to hospital procedure volume. The objective of this study was to determine whether the volumes of primary and revision total hip replacements performed at hospitals and by surgeons are associated with rates of mortality and complications.
  
  
  METHODS
  We analyzed claims data of Medicare recipients who underwent elective primary total hip replacement (58,521 procedures) or revision total hip replacement (12,956 procedures) between July 1995 and June 1996. We assessed the relationship between surgeon and hospital procedure volume and mortality, dislocation, deep infection, and pulmonary embolus in the first ninety days postoperatively. Analyses were adjusted for age, gender, arthritis diagnosis, comorbid conditions, and income. Analyses of hospital volume were adjusted for surgeon volume, and analyses of surgeon volume were adjusted for hospital volume.
  
  
  RESULTS
  Twelve percent of all primary total hip replacements and 49% of all revisions were performed in centers in which ten or fewer of these procedures were carried out in the Medicare population annually. In addition, 52% of the primary total hip replacements and 77% of the revisions were performed by surgeons who carried out ten or fewer of these procedures annually. Patients treated with primary total hip replacement in hospitals in which more than 100 of the procedures were performed per year had a lower risk of death than those treated with primary replacement in hospitals in which ten or fewer procedures were performed per year (mortality rate, 0.7% compared with 1.3%; adjusted odds ratio, 0.58; 95% confidence interval, 0.38, 0.89). Patients treated with primary total hip replacement by surgeons who performed more than fifty of those procedures in Medicare beneficiaries per year had a lower risk of dislocation than those who were treated by surgeons who performed five or fewer of the procedures per year (dislocation rate, 1.5% compared with 4.2%; adjusted odds ratio, 0.49; 95% confidence interval, 0.34, 0.69). Patients who had revision total hip replacement done by surgeons who performed more than ten such procedures per year had a lower rate of mortality than patients who were treated by surgeons who performed three or fewer of the procedures per year (mortality rate, 1.5% compared with 3.1%; adjusted odds ratio, 0.65; 95% confidence interval, 0.44, 0.96).
  
  
  CONCLUSIONS
  Patients treated at hospitals and by surgeons with higher annual caseloads of primary and revision total hip replacement had lower rates of mortality and of selected complications. These analyses of Medicare claims are limited by a lack of key clinical information such as operative details and preoperative functional status.
authors.affiliation: Robert B Brigham Multipurpose Arthritis and Musculoskeletal Diseases Center, Brigham and Women's Hospital, Bostn, MA 02115, USA. jnkatz@partners.org
authors.forename: J N
authors.initials: JN
authors.lastname: Katz
authors.forename: E
authors.initials: E
authors.lastname: Losina
authors.forename: J
authors.initials: J
authors.lastname: Barrett
authors.forename: C B
authors.initials: CB
authors.lastname: Phillips
authors.forename: N N
authors.initials: NN
authors.lastname: Mahomed
authors.forename: R A
authors.initials: RA
authors.lastname: Lew
authors.forename: E
authors.initials: E
authors.lastname: Guadagnoli
authors.forename: W H
authors.initials: WH
authors.lastname: Harris
authors.forename: R
authors.initials: R
authors.lastname: Poss
authors.forename: J A
authors.initials: JA
authors.lastname: Baron
mesh_terms: D019644:Arthroplasty, Replacement, Hip / Q000401:mortality* / Q000706:statistics & numerical data; D002983:Clinical Competence; D015897:Comorbidity; D006302:Health Services Research; D017052:Hospital Mortality; D006801:Humans; D016015:Logistic Models; D006278:Medicare; D010043:Outcome and Process Assessment, Health Care; D011183:Postoperative Complications / Q000401:mortality*; D010818:Practice Patterns, Physicians' / Q000706:statistics & numerical data*; D019984:Quality Indicators, Health Care; D014481:United States / Q000453:epidemiology