Summary

Increased UKA usage decreases TKA outcomes.

Abstract

Background

Surgeons with higher unicompartmental knee arthroplasty (UKA) usage have lower UKA revision rates. However, in order to increase UKA usage in arthroplasty patients, surgeons will decrease their usage of total knee arthroplasty (TKA). The purpose of this study was to investigate the influence of UKA usage on survivorship and patient reported outcomes (PROMs) of UKA, TKA, and UKA/TKA results.

Methods

Using the New Zealand Registry Database, surgeons were divided into 6 cluster groups, based on their UKA usage:<1%, 1-5%, 5-10%, 10-20%, 20-30% and >30%. A comparison of UKA, TKA and UKA/TKA revision rates as well as PROMs using the Oxford Knee Score (OKS) between the groups was performed.

Results

We identified 91,895 knee arthroplasties, of which 8,271 were UKA. Surgeons with higher UKA usage had lower UKA revision rates, but higher TKA revision rates. The lowest TKA and UKA/TKA revision rates were observed in the 1-5% UKA cluster, compared to highest TKA and UKA/TKA in the >30% UKA cluster (Log Rank p<0.001 TKA; p<0.001 UKA/TKA). No clinically important differences in combined OKS scores were seen between UKA usage groups at 6 months, 5 years, or 10 years.

Conclusions

Surgeons with higher UKA usage have lower UKA revision rates, however, their UKA/TKA revision rate is the highest. An increase in TKA revision rate was observed for highest volume UKA users (>30%). Increased UKA usage did not result in higher PROMs. Surgeons need to be aware of the impact of increasing UKA usage on the UKA/TKA revision rate and clinical outcomes.