Cost-effectiveness of patellofemoral arthroplasty compared with total knee arthroplasty: a cohort study using data from the National Joint Registry for England

Purpose

Total knee replacement (TKR) and patellofemoral joint replacement (PFR) are both surgical options for patellofemoral joint osteoarthritis. This study aimed to determine which procedure is more cost-effective.

Methods

A Markov model was constructed to evaluate the cost-effectiveness of PFR compared with TKR, using revision risk and age-specific mortality derived from UK life tables. A model-based economic evaluation was conducted from an NHS healthcare perspective, with costs derived from NHS reference costs. The model used a 60-year time horizon with annual cycles. Utility values were derived from patient-reported outcome measures collected between 6 and 18 months postoperatively and linked to 900 PFR and 287 777 TKR cases from the National Joint Registry.

To ensure comparability between groups, inverse probability of treatment weighting was used to adjust for age, sex, American Society of Anaesthesiologists classification, social deprivation indices, anaesthesia type, healthcare provider, surgeon experience, Charlson Comorbidity Index and preoperative EQ-5D-3L and Oxford Knee Scores.

Results

PFR was associated with lower costs than TKR, with an initial per-patient saving of approximately £4000. In younger patients, PFR was associated with slightly lower quality-adjusted life years (QALYs) compared with TKR, whereas in older patients it was associated with marginally higher QALYs. These differences resulted in variation in incremental cost-effectiveness ratios (ICERs) across age groups, with a trend towards greater cost-effectiveness of PFR in older populations. Cost savings decreased with age due to lower revision rates in older populations. Similar trends were observed across both sexes, although males experienced greater QALY gains, while PFR was more cost-effective overall in females. In younger patients, TKR was linked to higher costs and marginally lower effectiveness, though the difference in cost-effectiveness between PFR and TKR in this group was minimal.

One-way sensitivity analysis demonstrated that the model was highly sensitive to assumptions regarding postoperative utility following both PFR and TKR, with variation sufficient to alter the direction of the ICER. In contrast, revision utility and discount rate had relatively minor effects.

Conclusion

PFR may be a cost-effective alternative to TKR under certain assumptions, particularly in older patients; however, substantial decision uncertainty remains, driven primarily by variation in postoperative utility.