“Improving the accuracy of implant positioning and limb alignment continues to be an important goal in total knee arthroplasty.” TKA using conventional instruments has been shown to yield a high incidence of coronal, sagittal and HKA outliers (> 3° from the target). Robotic-assisted TKA “has been introduced to increase the accuracy of bone resections and reduce the number of alignment outliers in TKA.” (1)

This was a comparative cadaveric study of 20 knees (10 specimens) in the conventional group and 14 knees (7 specimens) in the robotic group. There were no significant differences in specimen characteristics between the groups. Surgeons were asked to create an intra-operative plan (targets) while aiming for neutral alignment in both groups. The conventional surgeries were performed according to the current surgical technique and followed the surgeon’s normal workflow. (1)

Only 1 of the 4 surgeons had previous experience with robotic TKA surgery. All surgeons underwent a standardised training programme before starting the study. This included theoretical training, 3 saw-bone procedures, and 2 cadaveric surgeries. This robotic system uses optical tracking technology to position and hold a robotic arm with a cut and pin guide in the desired location to achieve the intra-operative plan. The surgeon then uses a ‘traditional’ saw to make all the bone cuts. The robot was used to perform the distal femoral resection and the proximal tibial resection through the cut guide, and to position the conventional 4-in-1 cut guide on the distal femur via the pin guide. (1)

The study found that the hip-knee-ankle angle (HKA) was more accurate, with fewer outliers in the robotic group than the conventional instrumentation group. When compared to the target HKA, 100% of the robotic-assisted cases were within 3° of the target, while 93% were within 2°. By comparison in the conventional group 75% were within 3° and just 60% of cases were within 2° of the target. (1)

The accuracy of all bone resection angles were significantly (p < 0.05) better in the robotic group than the conventional group. The variance from the target was also lower for many parameters in the robotic group, reducing the chances of an outlier. When it came to the bone resection levels, the accuracy in the robotic group was significantly (p < 0.05) better than the conventional group for the proximal tibial and posterior femoral cuts. When reviewing between surgeon differences, no differences were observed in the robotic group. By contrast, a significant difference was observed between surgeons for the posterior femoral resection level in the conventional group. This suggests that the anteroposterior position of the 4-in-1 femoral cut block is more reproducible with robotics than conventional instruments. (1)

The authors concluded that robotic TKA “produces more accurate and more reproducible bone resections than conventional instrumentation” and that their in-vitro study “supports the clinical use of this new robotic system.” Further studies are needed to examine how these in-vitro findings translate to a clinical setting and patient outcomes. (1)