Functional positioning principles for image‐based robotic‐assisted TKA achieved a higher Forgotten Joint Score at 1 year compared to conventional TKA with restricted kinematic alignment

Abstract Purpose Few comparative studies assessed the current concept of individualised alignment for total knee arthroplasty (TKA) and their outcomes at mid‐term. This study aimed to evaluate the functional outcomes at 1 year of primary TKA performed with a functional positioning technique based on an image‐based robotic‐assisted system, compared to conventional TKA performed with a restricted kinematic alignment technique. Methods This retrospective comparative study included 100 primary TKAs performed with functional positioning principles using an image‐based robotic‐assisted system. A control group included 100 primary TKAs with the same posterior‐stabilised implant as the robotic group but performed with manual instrumentation and restricted kinematic alignment technique. In the robotic group, the mean age was 69.2 years old ± 7.9; the mean body mass index was 29.7 kg/m 2 ± 4.6. The demographic characteristics were similar between both groups. Kujala score, Forgotten Joint Score (FJS), Knee Society Score (KSS) knee and KSS function were collected 12 months postoperatively. Normally distributed continuous variables were compared using the Student t test. For non‐normally distributed continuous variables, the Mann–Whitney test was used. Results FJS was significantly higher in the robotic group (76.3 ± 13 vs. 68.6 ± 16.9 in the conventional group; p = 0.026). At a 1‐year follow‐up, there was no significant difference in the KSS knee and KSS function scores and the Kujala score between both groups. The mean KSS knee score was 90.8 ± 11.4 in the robotic group versus 89.4 ± 9.6 in the conventional group ( p = 0.082). The mean KSS function score was 91.4 ± 12.3 versus 91.3 ± 12.6, respectively ( p = 0.778). Conclusion Functional positioning principles using an image‐based robotic‐assisted system achieved a higher Forgotten Joint Score 1 year after TKA compared to restricted kinematic alignment. Personalised alignment and implant positioning are interesting paths to improve the functional outcomes after TKA. Level of evidence III.