Radiographic accuracy in TKA with a CT-based patient-specific cutting block technique

Patient-specific instrumentation (PSI) technology for the implantation of total knee arthroplasty (TKA) has a rising interest in the orthopaedic community. Data of PSI are controversially discussed. The hypothesis of this paper is that the radiological accuracy of CT-based PSI is similar to the one of navigated TKA published in the literature. Since 2010, all 301 consecutively performed PSI TKAs (GMK MyKneeA (c)) were included in this study. The radiological assessment consisted in a preoperative and postoperative standard X-ray and long-standing X-ray. Changes from the planned to the definitively implanted component size were documented. Postoperative analysis included limb alignment and position of femoral and tibial components (for varus/valgus and flexion or tibial slope). The postoperative average hip-knee-ankle angle was 180.1A degrees A A +/- A 2.0A degrees. In the frontal plane a total of 12.4 % of outliers > 3A degrees, for the tibial components 4.1 % of outliers > 3A degrees and for the femoral components 4.8 % of outliers > 3A degrees were measured. A total of 12.3 % of outliers for posterior tibial slope and 9 % of outliers > 3A degrees for the femoral flexion were noted. 10.8 % of the 602 planned size components were adapted intraoperatively. Although it is still unknown which limb axis is the correct one for the best clinical result, a technology providing the aimed axis in a most precise way should be chosen. Comparing the outcome of the current study with the data from the literature, there does not seem to be any difference compared to computer-assisted surgery. IV.