No benefit of robotic assisted over computer assisted surgery for achieving neutral coronal alignment in total knee arthroplasty.

The use of robotic assisted surgery (RAS) in total knee arthroplasty (TKA) is becoming increasingly popular due to better precision, potentially superior outcomes and the ability to achieve alternative alignment strategies. The most commonly used alignment strategy with RAS is a modification of mechanical alignment (MA), labelled adjusted MA (aMA). This strategy allows slight joint line obliquity of the tibial component in order to achieve superior balancing. In the present study, we compared coronal alignment after TKA using RAS with aMA and computer assisted surgery (CAS) with MA, that has been the standard in the center for more than 10 years. We analyzed a prospectively collected database of patients undergoing TKA in a single center. Lateral distal femoral angle (LDFA) and medial proximal tibial angle (MPTA) were compared for both techniques. In 140 patients, 68 CAS and 72 RAS, we observed no difference in postoperative measurements (median 90° for all, LDFA p=0.676, MPTA p=0.947) and no difference in outliers <2° (LDFA p=0.540, MPTA p=0.250). The present study demonstrates no benefit in eliminating outliers or achieving neutral alignment of both the femoral and the tibial component in robotic-assisted versus computer assisted TKA if mechanical alignment is the target. In order to utilize the precision of robotic assisted surgery, it is recommended to aim for more personalized alignment strategies.