Computed Tomography-Based Analysis of Implant Positioning after Total Knee Arthroplasty: A Randomized Controlled...

The aim of this study was to evaluate the deviation from the surgical plan of femoral and tibial components positioning after robotic total knee arthroplasty (R-TKA) compared with conventional TKA (C-TKA) based on postoperative three-dimensional computed tomography (3D-CT). This prospective randomized trial included 60 patients: 29 in the C-TKA group and 31 in the R-TKA one. Early postoperative 3D-CT-based analysis of implants positioning was performed. Measurements were performed twice by two observers, showing good to excellent intra- and interobserver reproducibility (interclass coefficient ranging from 0.71 to 0.96). Absolute deviations from the surgical plan (mechanical alignment in the C-TKA group and personalized alignment in the R-TKA group) were compared between groups. Primary endpoint was coronal lower limb frontal alignment: hip-knee-ankle (HKA) angle. Secondary endpoints were frontal, sagittal, and rotational positioning of both tibial and femoral components. Planned frontal lower limb alignment was similarly achieved in both group: HKA angle mean difference was 2.28 ± 1.81 degrees in the C-TKA group and 1.84 ± 1.46 degrees in the R-TKA group (p = 0.379). Deviations from the surgical plan were lower in the R-TKA group compared with the C-TKA group for all parameters, except tibial rotation (9.02 ± 4.51 vs. 7.42 ± 3.96 degrees, respectively). These differences turned out to be statistically significant only for sagittal alignment of both femoral (1.71 ± 1.34 vs. 3.61 ± 2.05 degrees, p < 0.001) and tibial (3.78 ± 1.15 vs. 4.94 ± 1.99 degrees, p = 0.018) components. Accuracy in achieving planned coronal lower limb alignment is not higher using R-TKA compared with C-TKA. Regarding component positioning, R-TKA appears superior in the sagittal plane while no significant differences were identified in terms of frontal alignment and rotation. LEVEL OF EVIDENCE:  I.