Intraoperative patellar tracking assessment during image-based robotic-assisted total knee arthroplasty: technical note and reliability study

Introduction: Restoration of the anterior knee compartment is increasingly studied with the development of personalized surgery. However, evaluating the patellar tracking during the surgery is still subjective and at the surgeon's discretion. This study aimed 1) to describe the assessment of the patellar tracking during robotic-assisted total knee arthroplasty (TKA), 2) to describe a new measurement technique for evaluating the evolution of this patellar tracking, and 3) to assess its reliability and repeatability. Method: This monocentric study assessed the evolution of patellar tracking for 20 robotic-assisted TKA. The sharp probe was used to perform patellar tracking in all the arcs of knee flexion before and after the bone cuts. The patella positioning was recorded every 10 degrees of flexion between the full extension and 90 degrees knee flexion and was assessed in the coronal and sagittal planes. For the measurements of the patellar tracking, we used a sagittal view and a coronal view of the knee on the MAKO software. From these two views, the difference between the patellar tracking before and after the bone cuts with the definitive implants was measured. Two independent reviewers performed the measurements to assess their reliability. To determine intraobserver variability, the first observer performed the measurements twice. Results: The mean age was 68.7 years old +/- 5.2 [61; 75], the mean body mass index was 28.8 kg/m2 +/- 4.2 [21.4; 36.2], the mean HKA angle was 176.3 degrees +/- 3.7 degrees [174.1.4; 179.7]. The radiographic measurements showed very good to excellent intra-observer and inter-observer agreements (0.60 to 1.0). Conclusion: This new measurement technique assessed the evolution of patellar tracking after TKA with good inter and intra-observer reliability.