Roboterassistierte Knieendoprothetik

Restoration of a neutral lower limb alignment was considered the gold standard in total knee arthroplasty (TKA); however, as 10–20% of the patients are dissatisfied following TKA, alternative alignment philosophies were proposed in order to improve clinical and functional outcomes. Indeed, previously published studies report a wide variability of coronal lower limb alignment, suggesting that a correction to neutral inevitably changes the patients’ natural alignment to an unphysiological state associated with altered ligament balance and overall joint kinematics in a relevant proportion of cases. As a consequence, personalized alignment strategies, which aim to restore the patient’s constitutional alignment, have gained popularity in TKA. Preoperative analysis of the patient’s individual knee phenotype is crucial for a personalized arthroplasty approach. Coronal Plane Alignment of the Knee (CPAK) classification defines 9 distinct knee phenotypes by the combination of coronal leg alignment and joint line orientation and allows for the assessment of the prearthritic lower limb alignment. With the implementation of robotic technologies (rTKA), these highly individualized alignment strategies can be precisely applied. Intraoperative virtual component placement allows for real-time simulation of postoperative alignment and gap balance. Using rTKA, the intraoperative plan is executed with high precision, thus targeted component alignment is achieved accurately and alignment outliers are significantly reduced compared to conventional TKA. This article summarizes current evidence on constitutional knee phenotypes and alternative alignment strategies. Finally, we propose an approach for the application of CPAK classification in total knee arthroplasty using robotic technology.