Accuracy of image-free robotic-assisted total knee arthroplasty: A computed tomography-based three-dimensional validation study

Purpose The aim of this study was to evaluate the three-dimensional (3D) accuracy of component positioning in image-free robotic-assisted total knee arthroplasty (ra-TKA) by comparing intra-operative robotic plans with post-operative computed tomography (CT)-based measurements and to clinically validate the accuracy of posterior femoral condylar reproduction. Methods Seventy-three consecutive varus knees (mean patient age 73 ± 6 years) underwent ra-TKA using NAVIO or CORI system with the JOURNEY II implant. Posterior femoral condylar accuracy was assessed by comparing planned and achieved resection thickness using a caliper. Post-operative component positions were evaluated using CT-based 3D–3D matching in an anatomical coordinate system, and direction-specific differences from the intra-operative plan were analyzed. Results Posterior femoral condylar resection showed small errors (0.9 ± 1.0 mm medial, 0.8 ± 0.7 mm lateral). Directional component position differences for the femur were −0.2 ± 1.6° (coronal), −2.2 ± 1.8° (sagittal), and 0.6 ± 1.9° (rotational). For the tibia, directional differences were −0.3 ± 1.0° (coronal), −1.3 ± 1.5° (sagittal), and −7.9 ± 6.3° (rotational). Absolute differences were 1.2 ± 1.0°, 2.2 ± 1.6°, and 1.6 ± 1.3° for femoral components and 0.7 ± 0.7°, 1.6 ± 1.2°, and 8.6 ± 5.1° for tibial components in the coronal, sagittal, and rotational planes. Conclusions Image-free ra-TKA demonstrated clinically acceptable posterior condylar accuracy and direction-specific positional differences between intra-operative planning and post-operative measurements. These differences may reflect surgical accuracy, coordinate system discrepancies, and variability in intra-operative surgical procedures, rather than surgical error alone.