Learning curves of robotic assisted versus conventional unicompartmental knee arthroplasty

Abstract

Introduction: Robotic assisted unicompartmental knee arthroplasty(UKA) can improve component alignment compared to conventional technique, yet the outcomes of both techniques are directly related to surgeon’s operative volume. We aimed to compare the results of the initial few UKA operations using both techniques by one surgeon within the learning curve. Methodology: We retrospectively reviewed the first 25 fixed bearing medial UKA performed using conventional spacer block technique(n=15) and imagefree robotic assisted UKA(n=10) by a single arthroplasty surgeon. Radiological outcomes including mechanical axis, tibial component coronal alignment and posterior slope were measured on lower limb long films. Clinical outcomes including Knee Society Knee Score(KSKS) and Functional Scores(KSFA) at 6 months were compared. Results and Analysis: Tibial component was significantly more varus for conventional compared to robotic UKA(3.46˚ varus vs 0.99˚ varus, p=0.027). Posterior tibial slope was larger in the conventional group(10.1˚ vs 7˚) but was not statistically significant(p=0.13). No differences were observed in mean postoperative limb mechanical alignment(conventional 5.7˚ varus vs robotic 4.2˚varus, p=0.995). KSKS and KSFA at 6 months showed no significant differences between the two groups. 1 robotic UKA was revised for tibial collapse and 1 conventional UKA was revised for femoral component undersizing. Tourniquet times and operative times were significantly longer for robotic UKA compared with conventional(86 min vs 126 min, p=0.000086; 124min vs 160min, p=0.015, respectively). Discussion and Conclusion: Unicompartmental knee arthroplasty is a technically demanding procedure with a small margin of error. Accurate component placement is vital and can be achieved by robotic assistance, especially for the less experienced surgeon.