Dr. Philippe Moewis (Berlin), Dr- Rainald Ehrig (Berlin), Prof. Dr. Hagen Hommel (Wriezen), Dr. Adam Trepczynski (Berlin), Leonie Krahl (Berlin), Prof. Dr.-Ing. Georg N. Duda (Berlin)
Abstract-Text (inkl. Referenzen und Bildunterschriften)
Introduction
Total knee arthroplasty (TKA) is an established procedure with 95% survivorship but 14-39% dissatisfaction. One of the reported causes is anterior knee pain due to paradoxical anterior sliding or insufficient rollback [1]. The aim of this study was to analyze whether TKA geometry impacts the in-vivo rolling/sliding ratio and thus modulates the kinematic.
Methods
Four cohorts (10 each) of patients were analyzed: gradually changing radius PS and CR (G-CurvePS, G-CurveCR), asymmetric bicruciate stabilized and CR (A-BCS, A-CR). Fluoroscopy was conducted in loaded lunge and unloaded flexion-extension [2]. 3D CAD models were registered to the fluoroscopic images. Medial/lateral points (anterior posterior translation) and femoral condyles path were determined (Fig 1). The Sliding/ Rolling ratio was defined as the quotient of the AP-translation and the femoral path length.
Results
During unloaded flexion-extension and loaded lunge the G-Curve designs showed a behavior near a hinge joint until mid-flexion followed by an increase in rolling/sliding towards posterior until maximal flexion.
Both asymmetric designs slid spontaneously to anterior during early flexion but then rolled/slided posterior. This pattern was still present but also reduced during loaded lunge (Fig 2).
Discussion
Combination of changing radius and posterior cruciate ligament strategy in the G-Curve PS/CR seems to stabilize the kinematic across flexion while the asymmetry in the A-BCS and A-CR designs showed initial instability followed by sudden posterior movement. These patterns were however reduced by loading with unloaded settings allowing to better identify kinematic differences between designs. However, these changes as well as the influence of factors such as tibial posterior slope need to be analyzed in larger cohorts.
References
1. Maratt et al., JoA. 2015
2. Pfitzner et al., KSSTA. 2017
Acknowledgements
DFG (EH 422-2-1/MO 3865-1-1).