Cost-effectiveness of unicompartmental compared with total knee replacement: a population-based study using data from the National Joint Registry for England and Wales

Objectives: To assess the value for money of unicompartmental knee replacement (UKR) compared with total knee replacement (TKR).

Design: A lifetime Markov model provided the framework for the analysis.

Setting: Data from the National Joint Registry (NJR) for England and Wales primarily informed the analysis.

Participants: Propensity score matched patients in the NJR who received either a UKR or TKR.

Interventions: UKR is a less invasive alternative to TKR, where only the compartment affected by osteoarthritis is replaced.

Primary outcome measures: Incremental quality-adjusted life years (QALYs) and healthcare system costs.

Results: The provision of UKR is expected to lead to a gain in QALYs compared with TKR for all age and gender subgroups (male: <60 years: 0.12, 60-75 years: 0.20, 75+ years: 0.19; female: <60 years: 0.10, 60-75 years: 0.28, 75+ years: 0.44) and a reduction in costs (male: <60: £-1223, 60-75 years: £-1355, 75+ years: £-2005; female: <60 years: £-601, 60-75 years: £-935, 75+ years: £-1102 per patient over the lifetime). UKR is expected to lead to a reduction in QALYs compared with TKR when performed by surgeons with low UKR utilisation but an increase among those with high utilisation (<10%, median 6%: -0.04, ≥10%, median 27%: 0.26). Regardless of surgeon usage, costs associated with UKR are expected to be lower than those of TKR (<10%: £-127, ≥10%: £-758).

Conclusions: UKR can be expected to generate better health outcomes and lower lifetime costs than TKR. Surgeon usage of UKR does, however, have a significant impact on the cost-effectiveness of the procedure. To achieve the best results, surgeons need to perform a sufficient proportion of knee replacements as UKR. Low usage surgeons may therefore need to broaden their indications for UKR.