Association between number of replacements and readmissions following total knee and total hip replacements in New South Wales' public hospitals

BACKGROUND: Total knee and total hip replacement are common and resource-intensive procedures. Complications are associated with worse outcomes and can add to the health care costs, particularly if associated with readmission. The aims of this study were to inform quality improvement by reporting on the extent of variation in readmissions across public hospitals and investigating the association between hospital volume and readmissions. METHODS: This retrospective population-based cohort study used linked, admitted patient data for a census of all admissions to public and private hospitals. Adults who had an acute hospitalization for total knee or total hip replacement elective surgery and were discharged alive between 1 July 2015 and 30 June 2018 were included. Hospital volumes and risk standardized readmission ratios were calculated, and readmissions included acute hospitalizations following discharge and returns to acute care from non-acute settings within 60 days. RESULTS: In 2015-2018, one in 10 patients were readmitted following total knee or total hip replacement (11.9 and 10.6 per 100 hospitalizations) an increase of 4.9% and 13.1% respectively, compared to 2012-2015. The majority of hospitals had risk standardized readmission ratios no different than expected. The median annual hospital volume was 170 total knee (interquartile range 116-247) and 93 total hip (interquartile range 61-141) procedures with no evidence of a meaningful association between hospital volume and readmissions. CONCLUSION: Readmissions rates for total knee and total hip replacements are increasing. While hospital volume varies, it was not associated with readmission after adjusting for risk factors and any non-linear association.