Critics of Unicompartmental knee replacement (UKR) highlight poor survivorship in national joint registries and argue that revision to Total Knee Replacement (TKR) is technically difficult with inferior function and survivorship compared to primary TKR.

We prospectively reviewed outcomes of UKRs in our institution undergoing early revision to a TKR, comparing conventional revisions to those performed using computer navigation. 20 cases were identified, 7 conventional and 13 navigated. 13 were male and 7 female, mean age at primary UKR was 63.6 years (range: 47–81).

Mean follow up time after revision was 5.2 years (2–9.5). Mean surgical time was 152 mins in conventional revisions and 163 mins for navigated. 43% of conventional cases required revision stems or augments, compared to 15% of conventional cases. Mean Oxford Knee Scores for revised knees were 32.8 in the conventional group and 34.64 in the navigated group, compared to 30.02 in the national joint registry. This compares to a mean Oxford score of 37.16 for primary TKRs in the registry. One of the conventional revisions required a further revision of the tibial component for loosening. This equates to a 95% suvivorship at mean 5 year follow up, or 1.10 revisions per 100 component years. Joint registry data had 1.97 revisions per 100 component years for UKR to TKR revisions, and 0.48 for primary TKRs.

Our results are significantly improved compared to other published series of UKR revisions to TKRs. Only one other series has reported outcomes of these revisions using navigation. Despite small numbers, our results suggest that navigation makes revisions of UKRs more straightforward with similar surgical times. Fewer revision components were required with navigation and functional scores were marginally improved.