title: Massachusetts health reform and disparities in joint replacement use: difference in differences study.
abstract: OBJECTIVE
  To estimate the impact of the insurance expansion in 2006 on use of knee and hip replacement procedures by race/ethnicity, area income, and the use of hospitals that predominantly serve poor people ("safety net hospitals").
  
  
  METHODS
  Quasi-experimental difference in differences study examining change after reform in the share of procedures performed in safety net hospitals by race/ethnicity and area income, with adjustment for patients' residence, demographics, and comorbidity.
  
  
  METHODS
  State of Massachusetts, United States.
  
  
  METHODS
  Massachusetts residents aged 40-64 as the target beneficiaries of reform and similarly aged residents of New Jersey, New York, and Pennsylvania as the comparison (control) population.
  
  
  METHODS
  Number of knee and hip replacement procedures per 10 000 population and use of safety net hospitals. Procedure counts from state discharge data for 2.5 years before and after reform, and multivariate difference in differences. Poisson regression was used to adjust for demographics, economic conditions, secular time, and geographic factors to estimate the change in procedure rate associated with health reform by race/ethnicity and area income.
  
  
  RESULTS
  Before reform, the number of procedures (/10 000) in Massachusetts was lower among Hispanic people (12.9, P<0.001) than black people (28.1) and white people (30.1). Overall, procedure use increased 22.4% during the 2.5 years after insurance expansion; reform in Massachusetts was associated with a 4.7% increase. The increase associated with reform was significantly higher among Hispanic people (37.9%, P<0.001) and black people (11.4%, P<0.05) than among white people (2.8%). Lower income was not associated with larger increases in procedure use. The share of knee and hip replacement procedures performed in safety net hospitals in Massachusetts decreased by 1.0% from a level of 12.7% before reform. The reduction was larger among Hispanic people (-6.4%, P<0.001) than white people (-1.0%), and among low income residents (-3.9%, p<0.001) than high income residents (0%).
  
  
  CONCLUSIONS
  Insurance expansion can help reduce disparities by race/ethnicity but not by income in access to elective surgical care and could shift some elective surgical care away from safety net hospitals.
authors.affiliation: VA Boston Healthcare System and Boston University School of Medicine, Boston, MA, USA hanchate@bu.edu.
authors.forename: Amresh D
authors.initials: AD
authors.lastname: Hanchate
authors.affiliation: University of Massachusetts Medical School, Worcester, MA, USA.
authors.forename: Alok
authors.initials: A
authors.lastname: Kapoor
authors.affiliation: Brigham and Women's Hospital and Harvard Medical School, Boston, MA USA.
authors.forename: Jeffrey N
authors.initials: JN
authors.lastname: Katz
authors.affiliation: Cambridge Health Alliance and Harvard Medical School, Cambridge, MA, USA.
authors.forename: Danny
authors.initials: D
authors.lastname: McCormick
authors.affiliation: Boston Medical Center and Boston University School of Medicine, Boston, MA, USA.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Lasser
authors.affiliation: Boston Medical Center, Boston, MA, USA.
authors.forename: Chen
authors.initials: C
authors.lastname: Feng
authors.affiliation: City University of New York, School of Public Health, New York, NY, USA.
authors.forename: Meredith G
authors.initials: MG
authors.lastname: Manze
authors.affiliation: VA Boston Healthcare System and Boston University School of Medicine, Boston, MA, USA.
authors.forename: Nancy R
authors.initials: NR
authors.lastname: Kressin
mesh_terms: D000293:Adolescent; D000328:Adult; D019643:Arthroplasty, Replacement / Q000706:statistics & numerical data*; D005006:Ethnicity / Q000706:statistics & numerical data; D005260:Female; D018166:Health Care Reform; D006297:Health Services Accessibility / Q000592:standards / Q000706:statistics & numerical data; D006801:Humans; D019458:Insurance Coverage / Q000458:organization & administration*; D008297:Male; D008404:Massachusetts; D008875:Middle Aged; D012044:Regression Analysis; D064876:Safety-net Providers / Q000706:statistics & numerical data; D012959:Socioeconomic Factors; D055815:Young Adult