Navigation of the tibial plateau alone appears to be sufficient in computer-assisted unicompartmental knee arthroplasty

Purpose The aim of this study was to present our technique to implant unicompartmental knee arthroplasty (UKA) using navigation and to give our first results regarding the accuracy of the device. Methods A total of 33 patients with medial femorotibial osteoarthritis (31) or avascular necrosis (2) were included in this study. The mean preoperative hip-knee-ankle (HKA) angle was 172.7 +/- 2.2A degrees (range 167-177A degrees) and the preoperative planning aimed to reach an HKA angle between 175 and 179A degrees (177 A +/- 2A degrees), a tibial varus at 3 A +/- 1A degrees, which means a tibial mechanical angle (TMA) close to 87 A +/- 1A degrees, and posterior tibial slope at 3 A +/- 2A degrees. In all cases, we used the OrthoPilotA (R) device with dedicated software allowing us to navigate only the tibial plateau. Results The preoperative plan was reached in 93.9 % of cases for HKA angle, 84.8 % for TMA and 100 % for the posterior slope. Conclusions Unicompartmental knee navigation is reliable. The navigation of only the tibial bone cut is a reasonable option as has been shown in this study. Its role is invaluable in the positioning of mobile-bearing UKA, where the risk of overcorrection should not be underestimated.