High Tibial Osteotomy (HTO) Versus Unicompartmental Knee Arthroplasty (UKA) in Medial-Compartment Knee Osteoarthritis (KOA): A Critical Narrative Review of Comparative Costs and Cost-Effectiveness

Background: Medial-compartment knee osteoarthritis (KOA) carries substantial disability and long-term cost. High tibial osteotomy (HTO) and unicompartmental knee arthroplasty (UKA) are key joint-preserving or joint-replacing options for selected patients, but their comparative economic ranking remains uncertain. Methods: This critical narrative review synthesized comparative economic evidence on HTO versus UKA for isolated medial-compartment KOA. PubMed and Web of Science were searched as primary sources for English-language studies published from 1 January 2000 to 15 January 2026, while Google Scholar and citation tracking were used supplementarily to identify potentially missed records. Eligible studies were direct economic evaluations or comparative cost/resource studies with clear decision relevance to the HTO–UKA choice. Burden and cost-of-illness studies were used for contextual framing only and were not included in the core comparative synthesis. Results: The direct evidence base was small and methodologically heterogeneous and was dominated by decision-analytic models that differed in perspective, time horizon, utility metric, and assumptions regarding reoperation, revision, and conversion to total knee arthroplasty (TKA). These structural differences largely explain why a U.S. lifetime societal model favored HTO, a UK age-stratified 10-year model produced age-dependent findings, and a recent Canadian public-payer model favored UKA. Observational studies suggest that UKA episode costs can fall substantially in outpatient or ambulatory pathways, whereas HTO costs may rise when reoperations and technique-specific resource use are explicitly captured. Conclusions: Current evidence does not support a context-free economic ranking of HTO and UKA. Because the available studies are heterogeneous and incremental utility differences are often small, the findings should be interpreted cautiously and as scenario-dependent rather than definitive. Future comparative analyses should use contemporary pathway data, transparent and standardized costing, and explicit downstream event definitions for both procedures.