Medical Utilization and Expenditures Before and After Total Knee and Hip Arthroplasty in Osteoarthritis in Seoul, South Korea: A Retrospective Matched Cohort Study

Background: Osteoarthritis (OA) is a chronic disease requiring long-term management, and its burden is expected to grow with population aging, including in South Korea’s rapidly aging population. Although total knee arthroplasty (TKA) and total hip arthroplasty (THA) are common interventions for OA, their long-term association with healthcare utilization and expenditures across benefit classifications remains unclear. This study examined differences in medical utilization and expenditures, disaggregated by benefit classification, between patients who underwent TKA/THA and matched non-surgical controls, before and after surgery. Methods: This retrospective cohort study used 1:3 direct matching on sex, calendar date, and OA duration to compare patients who underwent TKA/THA (2012–2019) with matched non-surgical controls at a tertiary hospital in Seoul, South Korea. Outcomes were inpatient and outpatient medical utilization and expenditures over 30-day intervals, disaggregated by benefit classification (covered, uncovered, and out-of-pocket payments (OOPs)). Generalized estimating equation models with an autoregressive correlation structure estimated associations before and after surgery. Poisson regression was used for inpatient and outpatient visits, and Negative Binomial regression was used for LOS given evidence of overdispersion and excess zeros. Medical expenditures were log-transformed and analyzed using normal distribution models. Results: A total of 351 surgical patients and 984 matched controls were included. Before surgery, the surgical cohort had lower inpatient utilization and expenditures than matched controls. Inpatient visits were 27% fewer (95% CI: 0.62–0.87). Covered, uncovered, and OOP expenditures were 25% (95% CI: 0.65–0.86), 24% (95% CI: 0.67–0.87), and 25% (95% CI: 0.65–0.86) lower, respectively. Outpatient OOPs were 46% higher (95% CI: 1.30–1.64). After surgery, this pattern reversed for inpatient services. Visits (exp(β) = 2.09, 95% CI: 1.64–2.67), average length of stay (exp(β) = 2.51, 95% CI: 1.78–3.54), covered expenditures (exp(β) = 3.12, 95% CI: 2.51–3.89), uncovered expenditures (exp(β) = 2.93, 95% CI: 2.41–3.58), and OOPs (exp(β) = 2.99, 95% CI: 2.42–3.71) were all higher than matched controls. Outpatient visits (exp(β) = 0.74, 95% CI: 0.65–0.84), covered expenditures (exp(β) = 0.52, 95% CI: 0.38–0.70), uncovered expenditures (exp(β) = 0.37, 95% CI: 0.24–0.58), and OOPs (exp(β) = 0.57, 95% CI: 0.48–0.68) were all lower. These results were consistent after Bonferroni correction for multiple comparisons (α = 0.0028). Conclusions: The association between arthroplasty and healthcare utilization differed markedly by period. Inpatient burden concentrated around surgery, while outpatient utilization at this institution declined thereafter. This may be partly explained by post-surgical care being dispersed toward non-tertiary institutions. These findings are hypothesis-generating and should be examined further using multi-institutional data. If substantiated, resource planning may need to prioritize the perioperative period while strengthening community-level coverage during recovery.