The use of augmented reality for limb and component alignment in total knee arthroplasty: systematic review of the literature and clinical pilot study

Purpose: A systematic review of the literature has been carried out to assess the actual evidence of the use of augmented reality in total knee arthroplasty (TKA). We then conducted a pilot clinical study to examine the accuracy of the Knee + augmented reality navigation in performing TKA. The present augmented reality (AR) system allows the surgeon to view the tibial and femur axis superimposed on the surgical field through the smart glasses. It provides real-time information during surgery and intraoperative feedback. Methods: A systematic review of the PubMed, MEDLINE, and Embase databases up to May 2021 using the keywords “augmented reality”, “knee arthroplasty”, “computer assisted surgery”, “navigation knee arthroplasty” was performed by two independent reviewers. We performed five TKAs using the Knee + system. Patients were 4 females, with mean age of 76.4 years old (range 73–79) and mean Body Max Index (BMI) of 31.9 kg/m2 (range 27–35). The axial alignment of the limb and the orientation of the components were evaluated on standardized pre and postoperative full leg length weight-bearing radiographs, anteroposterior radiographs, and lateral radiographs of the knee. The time of tourniquet was recorded. The perception of motion sickness was assessed by Virtual Reality Sickness Questionnaire (VRSQ) subjected to surgeon immediately after surgery. Results: After duplicate removal, a total of 31 abstracts were found. However, only two studies concerned knee arthroplasty. Unfortunately, both were preclinical studies. Knee + system is able to perform a cutting error of less than 1° of difference about coronal alignment of femur and tibia and less than 2° about flexion/extension of femur and posterior tibial slope. The absolute differences between the values obtained during surgery and the measurement of varus femur, varus tibia, posterior slope, and femur flexion angle on post-operative radiographs were 0.6° ± 1.34°, 0.8° ± 0.84°, 0.8° ± 1.79°, and 0.4 mm ± 0.55 mm, respectively. Conclusions: On light of our preliminary results, the Knee + system is accurate and effective to perform TKA. The translation from pilot study to high-level prospective studies is warranted to assess accuracy and cost-effective analysis compared to conventional techniques. Level of evidence: IV