Comparison of CT with intra-operative navigation reported implant position utilising a robotic assisted technique in total knee arthroplasty.

Background: Validation of navigated total knee arthroplasty (TKA) systems assists clinicians in making treatment decisions. The aim of this study was to independently review a navigation assisted robotic system for use in TKA.

Methods: We evaluated 87 patients (92 knees) undergoing robotic assisted TKA. Position estimated by the navigation software and postoperative CT scan were compared. Post-operative CT scans were interpreted by a senior radiologist blinded to intra-operative component position. Recorded were femoral varus/valgus, tibial varus/valgus and overall limb alignment in the coronal plane. In the sagittal plane tibial slope and femoral flexion/extension. Femoral component rotation was assessed in relation to the transepicondylar axis (TEA).

Results: Mean difference between software estimation and postoperative CT scan of the femoral component position in the coronal plane was 1.02° (0.86-1.18, 95%CI). Tibial coronal position was 1.19° (0.97-1.41). Sagittal plane component position for the femur was 1.64° (1.41-1.87). Tibial slope was 1.44° (1.21-1.68). Mean femoral component rotation was 1.27° (1.01-1.53). Overall 94.57% of intraoperative measures were within 3° of the component position measured on CT.

Conclusion: Robotic assisted navigation used in combination with a novel balancing system can result in very accurate component positioning during total knee arthroplasty.