Unicompartmental knee arthroplasty: all-poly versus metal-backed tibial component-a long-term follow-up study

While considered a satisfactory solution, unicompartmental knee arthroplasty (UKA) still raises concerns in regard to its durability. These concerns particularly focus on the tibial component. This study aims to compare two different cemented tibial components belonging to the same UKA design: all polyethylene (AP) versus metal backed (MB), at a long-term follow-up.

We retrospectively reviewed 143 successive patients, 83 of which underwent surgery with AP tibial component UKA (37 males, 46 females), and 67 with MB ones (17 males, 50 females). All implants had the same prosthetic design (Accuris UKA, Smith e Nephew) with identical femoral oxinium component but different tibial component, AP or MB. The KSS and KOOS were assessed at a mean of 11.5-year follow-up and compared to pre-operative, post-operative, and one year evaluation. Statistical analysis was performed with SPSS for Mac (version 17.0). To assess potential statistically significant differences, t test was used and significance was set at P < 0.05.

Final KSS at a mean of 11.5-year follow-up was 94.27 for the AP group and 96.12 for the MB ones. The final KOOS was 87 for AP components and 89.67 for the MB group. These results demonstrated, in all cases, statistically significant better results for MB tibial components compared to AP regarding KSS (P = 0.048), KOOS (P = 0.000), and pain (P = 0.014) at the 11.5-year follow-up. Survivorship for AP tibial component implants was 97.6%, while it was 89.5% for MB ones.

While the survivorship rate has been found to be greater for AP implants compared to MB tibial components, this study reveals statistically better functional results according to KSS and KOOS, and pain, at a long-term follow-up for MB implants.