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.