Abstract
INTRODUCTION
While multiple factors contribute to the variability of prosthesis placement during total knee arthroplasty (TKA), the accuracy of the surgeon's resection planning (positioning of the cutting block) is arguably the most critical. One may postulate that proper training, including enabling the surgeon to passively receive quantitative feedback on the cutting block position, may help him/her improve resection accuracy. The purpose of this study was to test the hypothesis that passive reception of feedback on cutting block position improves the accuracy of the successive TKA resection planning.
Materials and Methods
Five cadaveric knees (tibia and foot only) were studied. After arthrotomy, the tracker of an imageless navigation system (ExactechGPS®, Blue-Ortho, Grenoble, FR) was attached to the tibia. A navigated TKA procedure was initiated starting with registration of anatomical landmarks. Four surgeons then positioned the tibial cutting block (without pinning) on each knee using standard extramedullary mechanical instruments. The planned target resection was neutral varus/valgus, 3° posterior slope, and 10mm resection depth referencing the lateral plateau. Each surgeon performed 3 planning trials on each of the 5 knees, removing the cutting block between attempts. The planned resections were measured using an instrumented checker provided with the navigation system, referencing the cutting block. Surgeons were informed of the resection parameters measured by the navigation system after each planning trial. The deviations in resection parameters between the resection target and the cutting block position were calculated for each planning trial. The effect of receiving passive feedback on the accuracy of successive placement of the cutting block was assessed by comparing the deviations between each surgeon's 3 trials on the same cadaver (paired-t test). Statistical significance was defined as p<0.05.
Results
For all 3 trials in each of the 5 knees, the planned resections tended to be more valgus, and had more posterior slope and a larger resection depth compared to the resection target (Fig. 1). The average magnitudes of the deviations ranged from 0.8° to 1.3° for alignment parameters, and 0.8 to 1.2 mm for resection depth (Fig. 2). No significant differences were observed across the 3 planning trials for any of the resection parameters (N.S.).
Discussion
This study rejected the hypothesis that passive feedback improves the accuracy of successive tibial resection planning during TKA. This may be due to disconnect between feedback reception and subsequent resection planning. A possible solution to inaccuracies in resection planning may be intraoperative information exchange between the surgeon and the measurement tool, such as a navigated surgery, which has been proven to offer excellent resection accuracy [1].
In addition, compared to previous studies on resection variability based on the actual bony resection [1,2], which reflects the accumulated errors from all the potential sources, this study improved the understanding of surgical variability specifically during the planning phase of the tibial resection. The data from this study may benefit the improvement of instrument design or surgical techniques to assist more accurate TKA resections.
