Association between household income and the outcome of arthroplasty: a register-based study of total hip and knee replacements.
BACKGROUND
Previous research findings regarding the association between the outcomes of total hip and knee arthroplasty and patients' socioeconomic status have been contradictory. Consequently, we wanted to analyse whether individual-level household income was associated with the risk of revision arthroplasty and whether the time span in days from the primary arthroplasty to the revision operation varied according to income quintile.


METHODS
All first total hip and knee arthroplasties performed due to primary osteoarthritis in Finland from 1998 to 2007 were included in the study. Cox proportional hazard regression modelling was applied in the analysis regarding the risk of revision after the primary operation, while Poisson regression modelling was applied in the analysis regarding differences in the time from the primary to the revision operation between income quintiles.


RESULTS
The relationship between household income and the risk of revision arthroplasty was not statistically significant. The relationship remained insignificant, even when age, sex, and other confounding factors were adjusted for or analyses concerned revision in short or long term. In both the total hip arthroplasty and knee arthroplasty populations, patients in the lowest income quintiles underwent revision surgery earlier than patients in the highest income groups, but this difference was not statistically significant.


CONCLUSIONS
The quality of arthroplasty as measured by the risk of revision does not seem to depend on patients' income quintile.
Centre for Health and Social Economics CHESS, National Institute for Health and Welfare, Mannerheimintie 166, 00270, Helsinki, Finland, mikko.peltola@thl.fi.
Mikko
M
Peltola
Jutta
J
Järvelin
D000368:Aged; D019644:Arthroplasty, Replacement, Hip / Q000191:economics*; D019645:Arthroplasty, Replacement, Knee / Q000191:economics*; D005260:Female; D005387:Finland; D006801:Humans; D007182:Income; D008297:Male; D008875:Middle Aged; D017063:Outcome Assessment, Health Care; D016016:Proportional Hazards Models; D012042:Registries; D012086:Reoperation; D012306:Risk; D012923:Social Class