Age stratified, matched comparison of unicompartmental and total knee replacement.

BACKGROUND: Unicompartmental knee replacement (UKR) tends to provide better function but has a higher revision rate than total knee replacement (TKR). The aim was to determine if this occurred in all age groups. METHODS: Two large, non-registry, prospective cohorts with median 10-year follow-up (2252 TKR, 1000 medial UKR) were identified. All UKR met recommended indications. TKR with an inappropriate disease pattern for medial UKR were excluded. Knees were propensity score-matched within age-strata (<60 years at operation, 60 to <75, 75+) and compared using Oxford Knee Score (OKS), Kaplan-Meier revision rates and a composite failure, defined as any of revision, reoperation or no improvement in OKS. RESULTS: One thousand five hundred and eighty-two TKR and UKR were matched. Results are reported TKR vs UKR for ages <60, 60 to <75 and 75+. Median 10-year OKS were 33 vs 45 (p < 0.001), 36 vs 42 (p < 0.001) and 36 vs 38 (p = 0.25). Ten-year revision rates were 11% vs 7%, 5% vs 5%, and 5% vs 10%, (none significant). The composite failures occurred 8%, 5% and 5% more frequently with TKR than UKR (none significant). CONCLUSIONS: In this matched study UKR provided better functional outcomes in all age groups, particularly the young, and provided substantially more excellent outcomes. Although in older groups TKR tended to have a lower revision rate, in the young UKR had a lower revision rate. This was surprising and was perhaps because in this study UKR was, as recommended, only used for bone-on-bone arthritis, whereas in young patients it is widely used for early arthritis, which is associated with a high failure rate. This study supports the use of UKR with recommended indications, in all age groups.