Patient-Centered Discharge Criteria and Costs of Total Knee Arthroplasty: A Japanese Study

Background The increasing prevalence of total knee arthroplasty (TKA) owing to population aging imposes a considerable financial burden on healthcare systems. In this study, we analyzed the cost structure of TKA in Japan, where comprehensive cost data beyond hospital length of stay (LOS) are limited. Methods We retrospectively analyzed 100 consecutive TKAs (89 patients) for primary osteoarthritis performed by a single surgeon between April 2017 and December 2024. LOS was determined based on patient satisfaction and confidence in daily life, without premature discharge owing to medical reasons. The primary outcome measures were total hospital cost (THC) and its components: admission management (AM), surgery, surgery-related expenses, and rehabilitation. We also evaluated the impact of age, sex, body mass index, operation time, American Society of Anesthesiologists grade, clinical scores, and LOS on these costs. Results The median LOS was 31 days, with a median THC of JPY 2,268,700 (approximately USD 15,125, based on an exchange rate of USD 1 to JPY 150). The four components of THC accounted for nearly equal proportions between 24.0 % (585,194/2,268,670) and 25.7 % (582,970/2,268,670). THC was strongly correlated with LOS (r=0.751, p<0.001) and weakly correlated with age (r=0.364, p<0.001). After adjusting for multiple comparisons, LOS, AM, and rehabilitation remained significantly and positively associated with THC. Conclusions We observed that in the Japanese fee-for-service healthcare system, where surgical fees are typically fixed, prolonged LOS greatly increased hospital administrative and rehabilitation expenses. Conversely, under patient-centered discharge criteria, the near-equivalent cost structure also suggested the requirement for a certain period of comprehensive inpatient care. These findings underscore the need for novel strategies to optimize LOS and control THC.