Concurrent validation of a novel intraoperative navigation platform for total knee arthroplasty

This cadaveric study aimed to assess the accuracy of the Next-AR navigation platform in terms of implant alignment, kinematics, and collateral ligament elongations in comparison to gold standard measurement tools. Computed tomography of 7 fresh-frozen legs were acquired for patient-specific guide design, identification of bony landmarks and collateral ligaments to acquire real-time feedback for bone resection, alignment and collateral ligament elongations using Next-AR system. The specimens underwent medially-stabilized TKA (Medacta) based on the mechanical alignment technique. The difference between target and achieved implant alignment parameters was assessed. The relative change in tibiofemoral kinematics, medial collateral ligament- (MCL), and lateral collateral ligament (LCL) elongations acquired with the Next-AR system were compared to reference values acquired with bone-pin mounted motion trackers (Vicon, UK) while performing quasistatic squatting in an ex vivo knee simulator. The mean differences between achieved and target hip-knee-ankle angle, femoral varus, femoral flexion, femoral rotation, tibial varus, and tibial slope measured -1.5°, 0.5°, 0.07°, -0.14°, 0.79° and -0.36°, respectively, with no statistically significant differences found (p ≥ 0.12). Knee flexion (p=0.32) and valgus orientation (p=0.63), obtained from Next-AR and Vicon systems were comparable. Collateral ligament elongations derived from Next-AR exhibited similar values for the anterior bundle of MCL (p=0.18) and LCL in the anterior and middle bundles (p>0.3) obtained from the Vicon system. Our findings showed that the Next-AR system achieved postoperative implant alignment close to the planned targets, with small systematic deviation (mean bias ≤ 1.5°), limited total error (RMSE ≤ 2.3°), and variability of paired differences ≤ 1.87°, while additionally providing quantitative real-time assessment of tibiofemoral kinematics and collateral ligament elongations.