# Safety and efficacy of day-case hip and knee arthroplasty in the NHS: a nationwide UK cohort study

## TL;DR

This study examines the safety and outcomes of day-case hip and knee surgeries in the UK NHS, finding they are feasible but associated with higher readmission rates.

## Contribution

The study provides the first nationwide analysis of day-case hip and knee arthroplasty outcomes in the UK NHS using a 20-year dataset.

## Key findings

- Day-case arthroplasty had higher A&E attendance and readmission rates but lower infection and DVT rates compared to inpatient procedures.
- Survival probabilities were significantly higher for day-case arthroplasty patients over 20 years.
- Appropriate patient selection and post-discharge support are critical for expanding day-case arthroplasty in the NHS.

## Abstract

In recent years, day-case hip and knee arthroplasty has emerged as a potential solution to the elective backlog within the NHS. While international literature on this topic is extensive, only a handful of single-centre studies have been conducted in the United Kingdom. This study aimed to examine the safety and efficacy of day-case hip and knee arthroplasty in the UK using a 20-year linked national NHS dataset.

A cohort study was conducted using the Clinical Practice Research Datalink (CPRD), linked to Hospital Episode Statistics (HES) and the Office for National Statistics death registry. Adults undergoing primary hip or knee arthroplasty between 1998 and 2021 were included. Procedures were classified as day-case or inpatient, using two distinct approaches: patient classification and length of stay. Day-case is defined as discharge on the same day of the procedure, while inpatient procedures involve undergo at least one overnight stay in hospital. The primary outcomes assessed were A&E attendance, readmission, and critical care admission within 90-days post-operatively. Secondary outcomes included 90-day complication rates and survival analysis. Propensity score matching was implemented to adjust outcomes for age, gender, comorbidity burden, deprivation index, and ethnicity.

In total, 1,822 (0.16%) procedures were classified as day-case, while 4,355 (0.37%) had a recorded length of stay of 0 days. On average, patients undergoing day-case arthroplasty were younger, more often male, and had fewer comorbidities than their inpatient counterparts. Higher rates of A&E attendance (12% vs 9.1%; P = 0.001) and readmission (5.7% vs 3.7%; P < 0.001) were observed in the day-case cohort. In contrast, deep vein thrombosis (0.5% vs 0.9%; P = 0.010) and infection rates (1.0% vs 1.9%; P = 0.014) were lower in this patient group. Survival analyses demonstrated significantly higher adjusted survival probabilities associated with day-case arthroplasty (HR: 0.84; [95% CI: 0.72–0.99]; P = 0.034) over a 20-year follow-up period.

Day-case hip and knee arthroplasty has been demonstrated to be  safe and feasible, with comparable complication rates to the traditional inpatient setting. However, within the context of the NHS, it is currently associated with higher rates of 90-day A&E attendance and readmission. While increasing day-case volumes may help address elective backlogs, it is important to ensure that the appropriate patient selection criteria, optimised peri-operative care, and post-discharge support are in place before this approach is expanded in the UK.

The online version contains supplementary material available at 10.1186/s42836-026-00377-8.