title: Outcomes following large joint arthroplasty: does socio-economic status matter?
abstract: BACKGROUND
  We sought to determine whether socio-economic status (SES) is an independent predictor of outcome following total knee (TKR) and hip (THR) replacement in Australians.
  
  
  METHODS
  In this prospective cohort study, we included patients undergoing TKR and THR in a public hospital in whom baseline and 12-month follow-up data were available. SES was determined using the Australian Bureau of Statistics 'Index of Relative Advantage and Disadvantage'. Other independent variables included patients' demographics, comorbidities and procedure-related variables. Outcome measures were the International Knee Society Score and Harris Hip Score pain and function subscales, and the Short Form Health Survey (SF-12) physical and mental component scores.
  
  
  RESULTS
  Among 1,016 patients undergoing TKR and 835 patients undergoing THR, in multiple regression analysis, SES score was not independently associated with pain and functional outcomes. Female sex, older age, being a non-English speaker, higher body mass index and presence of comorbidities were associated with greater post-operative pain and poorer functional outcomes following arthroplasty. Better baseline function, physical and mental health, and lower baseline level of pain were associated with better outcomes at 12 months. In univariate analysis, for TKR, the improvement in SF-12 mental health score post arthroplasty was greater in patients of lower SES (3.8 ± 12.9 versus 1.5 ± 12.2, p=0.008), with a statistically significant inverse association between SES score and post-operative SF-12 mental health score in linear regression analysis (coefficient-0.28, 95% CI: -0.52 to -0.04, p=0.02).
  
  
  CONCLUSIONS
  When adjustments are made for other covariates, SES is not an independent predictor of pain and functional outcome following large joint arthroplasty in Australian patients. However, relative to baseline, patients in lower socioeconomic groups are likely to have greater mental health benefits with TKR than more privileged patients. Large joint arthroplasty should be made accessible to patients of all SES.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Dowsey
authors.forename: Mandana
authors.initials: M
authors.lastname: Nikpour
authors.affiliation: Department of Orthopaedics and The University of Melbourne Department of Surgery, St, Vincent's Hospital Melbourne, 41 Victoria Parade Fitzroy, Victoria 3065, Australia. pchoong@unimelb.edu.au.
authors.forename: Peter F M
authors.initials: PF
authors.lastname: Choong
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000191:economics* / Q000639:trends; D019645:Arthroplasty, Replacement, Knee / Q000191:economics* / Q000639:trends; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006306:Health Surveys / Q000191:economics / Q000639:trends; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012923:Social Class; D016896:Treatment Outcome