Trends in hip and knee replacement length of stay and patient demographics in England: a population-based study of 1,455,842 primary procedures

Background
Length of stay (LOS) after hip and knee replacement has decreased steadily in the modern era with enhanced recovery protocols, enabling healthcare systems to address rising surgical demand in an ageing, comorbid population. This study examines trends in LOS, patient characteristics, and their associations for NHS-funded procedures in England, covering a period that includes the COVID-19 pandemic.

Methods
Data from the National Joint Registry and Hospital Episode Statistics were linked to identify patients who underwent primary total hip replacement (THR) and total or unicompartmental (partial) knee replacement (TKR/UKR) in England between January 2010 and March 2022. LOS was analysed using flexible parametric models to estimate median values over time, with subsequent adjustment to examine associations between changing patient characteristics. Trends in 30-day readmission rates were also analysed.

Results
From 2010 to 2022, median LOS decreased from 4.26 days (95% CI 4.22 to 4.30) to 2.75 days (95% CI 2.74 to 2.77) for THR, from 4.35 days (95% CI 4.32 to 4.39) to 2.91 days (95% CI 2.90 to 2.92) for TKR, and from 3.2 days (95% CI 3.16 to 3.25) to 1.91 days (95% CI 1.89 to 1.95) for UKR. Variability also decreased. There were no increases in crude 30-day readmission rates. Trends in patient demographics showed increasing comorbidity, obesity, male sex, affluence, and use of the independent sector, all of which were associated with LOS and had the overall effect of slightly attenuating its reduction. Significant changes in patient characteristics occurred around the time of the COVID-19 pandemic but have since resumed previous trends.

Conclusions
Patients in England now typically stay fewer than three days for total hip or knee replacement and under two days for partial knee replacement. Despite demographic trends towards characteristics associated with longer LOS, reductions have occurred independently of these changes, suggesting potential for further shortening. However, as these diverging trends continue, ensuring equitable access to surgery will be increasingly important.