Aim: Computerized navigation of unicondylar knee arthroplasties (UKA) is not a widespread technique. The lifespan of a UKA depends on the quality of its implantation. We know that overcorrection leads to a rapid extension of the osteoarthritis to the opposite side of the knee and undercorrection to a rapid loosening or wear of the prosthesis. Because of these difficulties and following a long experience with navigation of total knee arthroplasties (TKA) and osteotomies around the knee, we began using navigation for revisions to TKA in 2003 and for UKAs in 2008. The aim of this work is to present, firstly, the axial alignment of 79 medial and 19 lateral computer-assisted UKAs and, secondly, the axial alignment of 23 computer-assisted UKA revisions to TKA.
Methods: In all the cases we used the Orthopilot® device (BBraun-Aesculap, Tuttlingen, Germany), which is a non image-based navigation system.
Results: For medial prostheses, the main objective was to obtain a post-operative HKA angle of 177° ± 2°, i.e. an under correction of 1-5°. This objective was met in 88.5 % of the cases. For lateral prostheses, the main objective was to achieve a post-operative HKA angle of 183° ± 2°, i.e. also an under correction of 1-5°. This objective was met in 84 % of the cases (3 cases at 186° and no cases of over correction). Regarding UKA revisions, the main objective was to ensure an HKA angle of 180° ± 3°. This was met in 92.4 % of the cases.
Conclusion: As for TKA and osteotomies, computerized navigation of UKAs and UKA revisions allows the pre-operative goal to be met easily.
Keywords: Computer; Knee; Navigation; UKR revision; Unicondylar prosthesis.