Half of all hip and knee arthroplasty patients may be potential day-case candidates: a nationwide register study of 166,730 procedures

Background and purpose - The overall potential pool of day -case candidates on a national level in hip and knee arthroplasty is unknown. We aimed to estimate the proportion of hip and knee arthroplasty patients eligible for day -case surgery based on contemporary widely used criteria and determine whether there has been a change in the proportion of eligible patients over time and, secondarily, to investigate the proportion of eligible patients discharged on the day of surgery. Methods - Based on data from the Danish National Patient Register, we identified all patients undergoing primary unilateral hip or knee arthroplasty from January 2010 to March 2020. Using a modification of day -case eligibility criteria proposed by a national multicenter collaboration, we sorted patients into either day -case eligible or ineligible. A day -case procedure was defined as discharge on the day of surgery. Results - We included patients comprising a total of 166,730 primary total hip (THA), total knee (TKA), and unicompartmental knee arthroplasty (UKA). 48% (95% confidence interval [CI] 48-49) were eligible for day -case surgery, with a decline from 50% (CI 49-51) in 2010 to 46% (CI 46-47) eligible in 2019. More UKA patients were daycase eligible (55%, CI 54-56) than THA (47%, CI 47-48) and TKA patients (49%, CI 48-49). A maximum of 8.0% (CI 7.4-8.5) of eligible patients were discharged on the day of surgery in 2019. Conclusion - 48% of the Danish hip and knee arthroplasty patients were potential day -case candidates, with a small decline in eligibility from 50% in 2010 to 46% in 2019. Day of surgery discharge among day -case eligible patients peaked at 8% in 2019. Thus, the potential for more day -case surgery seems large.