High coronal alignment accuracy and satisfactory early outcomes using augmented reality assisted kinematic alignment in total knee arthroplasty.

Purpose: Accurate component positioning in total knee arthroplasty (TKA) is critical for implant longevity and patient satisfaction. Augmented reality (AR)-based navigation systems offer enhanced precision and intraoperative versatility. This study evaluated the accuracy of component positioning, implant sizing and short-term clinical outcomes of a novel AR-assisted navigation system (NextAR, Medacta International) in TKA using a modified kinematic alignment (KA) technique. Methods: Forty-one consecutive patients underwent primary TKA using AR-assisted navigation with ≥12-month follow-up. Preoperative CT-based 3D planning optimised cut orientation and component placement. All received a cemented medial pivot prosthesis (GMK Sphere) with full femoral resurfacing following a KA protocol. Tibial cuts were guided intraoperatively by real-time ligament balancing. Planned versus achieved positions were compared on radiographs. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), forgotten joint score (FJS) and range of motion (ROM) were recorded pre- and postoperatively and analysed using paired t-tests (p < 0.05). Results: The average difference between planned and postoperative alignment was 0.05° ± 0.76° for LDFA, 0.1° ± 0.6° for MPTA, -0.5 ± 1.7° for femoral component flexion, and 0.3° ± 1.3° for PTS. Root mean square errors were 0.75°, 1.23°, 1.73° and 1.34°, respectively. Postoperative HKA improved from 174.3° ± 3.4° to 177.8° ± 2.1° (p < 0.001). Component size prediction was accurate in 100% of femurs and 95.1% of tibias. At final follow-up (14.2 ± 2.3 months), WOMAC improved from 51.5 ± 16.7 to 13.6 ± 5.3, FJS from 26.2 ± 9.6 to 82.2 ± 7.4, flexion from 103.3° ± 17.4° to 129.4° ± 7.2° and extension from 3.3° ± 0.43° to 0.1° ± 0.28° (all p < 0.001). Conclusions: AR-based navigation in modified KA-TKA ensured accurate LDFA restoration and femoral sizing, with good short-term outcomes. Variability remained in MPTA, femoral flexion and PTS. Although no coronal recuts were needed, two tibial recuts for tight extension gaps highlight areas for system refinement. Level of Evidence: Level IV.