Tibial Component Varus Alignment Does Not Affect Survivorship of Cementless Robotic-Assisted Total Knee Arthroplasty With Functional Knee Positioning

BACKGROUND: Cementless fixation is increasingly adopted in total knee arthroplasty (TKA). In parallel, robotic-assisted (RA) techniques have enabled personalized alignment strategies like functional knee positioning (FKP). However, evidence on survivorship for cementless robotic-assisted-TKA (RA-TKA) with FKP remains limited. This study evaluated revision risk and clinical outcomes after cementless RA-TKA with FKP at a minimum 2-year follow-up and explored whether tibial component varus alignment, age, sex, or body mass index (BMI) were associated with revisions. METHODS: This retrospective single-center study included all consecutive cementless cruciate-retaining or substituting RA-TKAs with FKP between November 2017 and September 2023. In total, 356 patients (381 RA-TKAs) who had a mean age of 70 years (range, 39.3 to 87.1) were analyzed at a minimum 2-year follow-up. The median follow-up was 3.5 years (95% confidence interval, CI: 3.3 to 3.8), and the follow-up rate was 94.9%. Survivorship was assessed using Kaplan-Meier analysis. Differences in survivorship stratified by tibial component coronal alignment (greater than 3 versus 3° or less varus), age greater than 75 years, sex, and BMI greater than 30 were evaluated using log-rank tests. The forgotten joint score-12 and a 5-level Likert satisfaction scale were collected at the last follow-up. RESULTS: Estimated survivorship at five years was 98.6% (95% CI: 97.4 to 99.8), with five revisions (four periprosthetic joint infections and one arthrofibrosis). There was no aseptic loosening that occurred. Tibial component varus greater than 3° was present in 35.6% of cases. Survivorship did not differ significantly between knees with and without tibial varus greater than 3°, nor for age greater than 75 years, sex, or BMI greater than 30 (P > 0.05). The mean forgotten joint score-12 and satisfaction were 85.2 (standard deviation 20.2) and 4.7 (standard deviation 0.7). CONCLUSIONS: Cementless RA-TKA with FKP demonstrated excellent survivorship and high patient satisfaction at a minimum 2-year follow-up, with no aseptic loosening that occurred. There was no association between tibial component varus, age, sex, or BMI and revision detected, supporting the safety of cementless fixation in personalized robotic alignment; however, the low number of revision events limits the ability to identify predictors of failure.