Robotic total knee arthroplastyThe accuracy of CT-based component placement

Abstract

Background Accurate alignment of the components in total knee arthroplasty is important. By use of postoperative CT controls, we studied the ability of a robotic effector to accurately place and align total knee arthroplasty (TKA) components according to a purely CT-based preoperative plan.Patients and methods Robotic TKA was performed in 13 patients (6 men) with primary gonarthrosis. Locator screws were placed into femur and tibia under spinal anesthesia. A CT-scan including the femoral head, knee and ankle was performed. In the preoperative planning software, virtual components were positioned into the CT volume. In a second operation, the robot milled femur and tibia with a high-speed milling tool according to the preoperative plan. On the 10th day, CT controls were performed following the same protocol as preoperatively.Results The mean deviation of the postoperative from the preoperatively planned mechanical axis was 0.2° (95% CI: -0.1° to 0.5°). The accuracy of angular component placement in frontal, sagittal and transverse planes was within ± 1.2°, and the accuracy of linear component placement in mediolateral, dorsoventral and caudocranial directions was within ± 1.1 mm.Interpretation Robotic TKA allows placement of components with unparalleled accuracy, but further development is mandatory to integrate soft-tissue balancing into the procedure and make it faster, easier and cheaper.

Robotic-assisted TKA Reduces Postoperative Alignment Outliers and Improves Gap Balance Compared to Conventional TKA

“…Overall, our results supported previous work [8,16,34,51] demonstrating robotic-assisted TKA can result in fewer outliers in radiographic alignment and an improved ability to achieve flexion-extension gap balance with similar complication rates, reduced postoperative drainage, and increased operative time when compared to conventional TKA at a minimum followup of 3 years. …”

“…Robotic-assisted TKA has been implemented to improve alignment, reduce outliers, and allow more accurate preoperative planning and execution than conventional TKA [8,16,19,34]. However, no studies thus far have looked at an intermediate-term (minimum 3-year) comparison of clinical and radiographic results for robotic-assisted TKA and conventional TKA.…”

“…Robotic systems have been developed to improve the accuracy of implant selection and placement, alignment, and bone resection during TKA [16,19,50]. In these computer-controlled cutting systems, the surgeon provides the surgical exposure and then supervises as the robot precisely machines the bone according to the plan.…”

“…Several observational studies have shown low rates of alignment error. Two studies showed no cases in which the postoperative alignment error was in excess of 1°in all three planes [8,16] and one reported all cases had implant placement within 1°of the preoperative planning in both the frontal and sagittal planes [16]. In comparison to conventional TKA, several studies have reported roboticassisted TKA improved placement of the femoral component in the AP plane when compared to the preoperative plan [34,51] and a more neutral postoperative coronal plane knee alignment [51].…”

“…The majority of previous studies [16,34,51] comparing postoperative results have been short term, with a maximum followup period of 3 months. While the 5-year mean followup study by Bellemans et al [8] found few alignment errors, they did not report function as compared with patients having conventional TKA.…”