Cost‐Effectiveness Analysis of Surgical Treatment of Varus Knee Osteoarthritis for Middle‐Aged Patients: A Multicenter Retrospective Cohort Study With Over 10‐Year Follow‐Up

Background Knee osteoarthritis with medial‐compartment varus deformity is common in middle‐aged adults, and the optimal surgical strategy for this group remains debated, with open‐wedge high tibial osteotomy (OWHTO) and total knee arthroplasty (TKA) representing joint‐preserving and joint‐replacing options whose comparative long‐term value is uncertain. Objective To compare the cost‐effectiveness and long‐term outcomes of open‐wedge high tibial osteotomy (OWHTO) versus total knee arthroplasty (TKA) in middle‐aged patients with varus knee osteoarthritis: Methods This multicenter retrospective cohort study analyzed registry data from three Chinese university affiliated hospitals. A total of 825 patients aged 45–65 who underwent OWHTO or TKA between 2005 and 2015 were included, with follow‐up through 2025. Outcomes included Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores, EQ‐5D‐5L utilities, range of motion (ROM), mechanical axis deviation (MAD), muscle strength, and total healthcare costs. Costs were assessed from a societal perspective (direct medical, direct non‐medical, and indirect productivity costs), and both costs and health outcomes were discounted at 3% annually. The EQ‐5D‐5L–based quality‐adjusted life year (QALY) was the primary outcome; clinical and functional measures were secondary. Multivariate regression models were used to compare outcomes between groups, and 1000‐bootstrap simulations were used to estimate incremental cost‐effectiveness ratios (ICERs). ICERs were interpreted against a willingness‐to‐pay threshold of one to three times China's 2024 gross domestic product per capita (CNY 95,749–287,247 per QALY). Robustness was assessed with inverse‐probability‐of‐treatment‐weighting (IPTW) and age‐stratified (45–54 vs. 55–65 years) sensitivity analyses. Results Clinical outcomes at final follow‐up did not differ significantly between OWHTO and TKA groups. OWHTO was associated with a lower cumulative cost (mean CNY 121,784) than TKA (CNY 160,075; p < 0.001). In cost‐effectiveness analyses, OWHTO was associated with better outcomes in WOMAC pain, mechanical alignment (MAD), ROM, and dynamic strength at a lower cost than TKA. Quality‐adjusted life year outcomes (EQ‐5D‐5L utility) slightly favored TKA (71.9% of bootstrap samples), yielding an ICER of CNY 5,441,410.25 per QALY for TKA relative to OWHTO, approximately 19 times the upper willingness‐to‐pay threshold (3× GDP per capita, CNY 287,247 per QALY), indicating that the marginal utility gain with TKA was not cost‐effective. The reoperation/revision rate did not differ between groups (OWHTO 0.95% [3/316] vs. TKA 0.59% [3/509]; p = 0.687), and findings were consistent in IPTW‐weighted and age‐stratified sensitivity analyses. Other ICERs were 146,719.91 CNY (WOMAC function), 53,934.07 CNY (WOMAC stiffness), 115,812.43 CNY (isometric strength), and 167,518.20 CNY (sit‐to‐stand power). Results were robust to sensitivity analyses. Conclusion Over more than 10 years of follow‐up, OWHTO provided outcomes equivalent to TKA while substantially reducing costs. These findings support OWHTO as a cost‐effective option for selected middle‐aged patients with varus knee osteoarthritis. Level of Evidence Level III, retrospective cohort study.