Abstract
Purpose
Patellofemoral arthroplasty (PFA) has experienced significant improvements in implant survivorship with second-generation designs. This has renewed interest in PFA as an alternative to total knee arthroplasty (TKA) for younger, active patients with isolated patellofemoral osteoarthritis (PF OA). The decision to select PFA over TKA balances the clinical benefits of sparing healthy knee compartments and ligaments against the risk of downstream conversion arthroplasty. We analyzed the cost-effectiveness of PFA versus TKA for the surgical management of isolated PF OA.
Methods
We used a Markov transition-state model (Figure 1) to compare cost-effectiveness between PFA and TKA. Cohorts were aged 60 (base case) and 50 years. Lifetime costs (2015 USD), quality-adjusted life year (QALY) gains and incremental cost-effectiveness ratio (ICER) were calculated from a healthcare payer perspective. Annual revision rates were derived from the United Kingdom National Joint Registry and validated against the highest quality literature available. Deterministic and probabilistic sensitivity analysis was performed for all parameters against a $50,000/QALY willingness-to-pay. Results for the 50 year-old cohort were similar to those of the base case simulation.
Results
PFA was more expensive ($49,811 versus $46,632) but more effective (14.3 QALYs versus 13.3 QALYs) over a lifetime horizon (Figures 2 and 3). The ICER associated with the additional effectiveness of PFA was $3,097. The model was mainly sensitive to utility values and implant survivorship, with PFA remaining cost-effective provided that its utility exceeds that of TKA by at least 1.0%. PFA achieved dominance (lower cost and higher utility) at an annual revision rate of 1.63%, representing a 24.5% decrease from baseline. The results were not sensitive to costs of rehabilitation, perioperative complications or inpatient hospitalization. Multivariate probabilistic sensitivity analysis showed PFA to be cost-effective from a healthcare payer perspective in 96.2% of simulations.
Conclusions
Recent improvements in implant survivorship rates makes PFA an economically beneficial joint-preserving procedure in younger patients, potentially delaying TKA until implant failure or tibiofemoral OA progression. The present study quantifies the minimum required marginal benefit for PFA to be cost-effective compared to TKA (1.0%) and identifies survivorship targets for PFA to become both less expensive and more effective. These cost-effectiveness benchmarks may be used to assess clinical outcomes of PFA from an economic standpoint within the United States healthcare system as updated clinical data becomes available.
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