Method: We developed a Markov, state-transition model to determine the CE of UKA vs. TKA in hypothetical younger (age 45) and older (age 65) patients. Patients transition to either a full- or limited-function state postoperatively based on their Western Ontario and McMaster Universities Osteoarthritis Index score. The limited-function state is associated with lower quality-of-life (QOL) and increased costs compared to full-function. Patients in either state may experience an implant failure. We assumed that limited-function state patients fail at a higher rate than full-function state and UKA patients only have home health rehabilitation while TKA patients could also have either inpatient rehabilitation or skilled nursing facilities options. Failure rates were calculated from 20-year follow-up data in the Swedish national registry. Procedure and complication costs were based on DRG and ICD-9 codes. Inpatient rehabilitation, outpatient healthcare utilization and return to work costs were derived from the literature. QOL data and transition probability to limited-function state were also from the literature. We report costs, quality-adjusted life years (QALYs), and ICERs over the lifetime of the patient from a societal perspective in US dollars (discounted at 3% annually).
Result: UKA dominated TKA in both younger and older patients in the base case In the younger patients only, TKA has an ICER <$100,000/QALY when the annual revision rate for UKA increased from 1.0% in the base case to 2.45% beginning at age 66 . Results were not sensitive to lowering TKA rehab costs. Increasing UKA’s transition probability to the limited-function state to equal that of TKA produced an ICER >$100,000/QALY.
Conclusion: Unlike previous studies, we found UKA had substantial economic value in older and younger patients. Our results indicate that UKA should be recommended for eligible patients regardless of age.