Summary

Imageless Robotics-assisted UKA shows better radiological accuracy and consistency with fewer outliers, compared with conventional UKA

Abstract

The aim of this study was to compare the short term clinical and radiological outcomes of imageless robotics-assisted and conventional unicompartmental knee arthroplasty (UKA) and to estimate the accuracy of the two techniques by analysing the outliers after UKA. We have evaluated 200 consecutive knees (171 patients), 100 knees undergoing imageless, robotics assisted UKA (CORI, Smith+Nephew, UK) and 100 knees treated with conventional UKA. Demographic parameters like age, gender, body mass index, diagnosis and range of motion were obtained. Knee society score (KSS) and Knee society functional score (KSS-F) were used for clinical evaluation. Long leg alignment (hip-knee-ankle angle), medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA) and tibial slope were analysed for radiological results and outliers were compared between both groups. Outliers were defined when the measured pre-operative hip-knee-ankle angle, LDFA or tibial slope exceeded ± 3° from the hip-knee-ankle angle, LDFA or tibial slope on the final follow-up radiograph.The minimum follow-up was 6 months (range, 6 to 26 months). The preoperative mean HKA angle was 171.7 ± 9.3° in robotic group and 170.3 ± 8.5° in conventional group. The number of HKA, LDFA and tibial slope outliers were 42, 67 and 23 respectively, in the conventional group compared to 21, 11 and 34 in the robotic group (p < 0.01). There was a significant improvement in the KSS and KSS-F functional scores postoperatively in both groups (p < 0.01). However, there was no significant difference in the functional scores between the groups postoperatively (p = 0.09). This study showed excellent improvement with both imageless robotic and conventional UKA, with similar clinical outcomes between both groups. However, radiologically robotic UKA showed better accuracy and consistency with fewer outliers compared with conventional UKA.