CONVENTIONAL AND ROBOTIC-ASSISTED TOTAL KNEE ARTHROPLASTY RESECTION DEPTH ACCURACY

The accurate execution of planned resections depths in total knee arthroplasty (TKA) directly affects the prosthesis alignment, press-fit and post-operative fixation stability [1], [2]. Advanced techniques, including robotic-assisted surgery, have been developed and employed to achieve greater accuracy. We hypothesized that robotic-assisted TKA (rTKA) would result in greater resection accuracy than conventional total knee arthroplasty (cTKA). Seventeen lower extremity cadaveric specimen (9 females, 8 males, aged 37–77) were utilized in this study. Each received pre-operative computed tomography (CT) scans of their entire length. The same surgeon performed bilateral TKAs using cTKA on one knee and rTKA on the contralateral knee. Mechanical alignment strategies were used. After all cuts and implant trialing, but prior to installation of the implant, all specimens were re-imaged with CT. Reconstructions of the femur and tibia-fibula bones were made for all specimens from both CT sets. Identification of anatomical landmarks allowed for construction of anatomic coordinate systems and registration of pre- and post-operative models. The true resection errors for the femoral distal resection (FDR), femoral posterior resection (FPR) and the tibial resection (TR) were computed, each considering the medial (−m) and lateral (−l) sides independently. Resection errors relative to the surgical plans were measured to assess accuracy. Exceptions were made for the FRD-l, TR-m, FPR-m and FRP-l of the cTKA cohort, where planned resection depths were not available due to the nature of the instrumentation. Resection errors of the two cohorts were compared via paired 2-sample t-tests the FDR-m and TR-l with a significance level of p<.05. Absolute mean error was not statistically different between the cTKA and rTKA cohorts for either the FDR-m (−1.0 mm ± 1.9 mm vs. −1.5 mm ± 1.0 mm, p = 0.24) or the TR-l (1.0 mm ± 1.6 mm vs. 0.2 mm ± 2.1 mm, p = 0.19). For all measured resections, femoral resections were generally under-cut, while tibial resections were generally undercut (Table 1). Regardless of surgical method, femoral resections were, on average, undercut whereas tibial resections were, on average, overcut. The results must be interpreted with the understanding that a bias exists due to the inclusion of articular cartilage in planned measurements that were not present in the bone models. Thereby, femoral accuracy may be greater than these results suggest, and tibial resection accuracy, worse. Additionally, the results are limited by cadaveric specimen thinner than the average TKA patient. These findings suggest that while rTKA systems may offer precision, there is still room for improvement of surgical accuracy and its clinical advantages need confirmation via other methods. For any figures or tables, please contact authors directly.