Aims and Objectives: In recent decades, knee arthroplasty (KA) succeeded to improve patients’ clinical scores and gait patterns [1]. However, to date, studies primary focused on biomechanical analysis of level walking with total knee arthroplasty (TKA) patients. The investigation of neuromuscular more challenging activities of daily living (ADL) like stair climbing and especially ramp negotiation was partly neglected [2]. Furthermore, non-sagittal plane parameters have mostly not been considered, whereby the evaluation of e.g. transverse plane kinematics and kinetics may reveal potential differences between various endoprosthetic designs. Additionally, frictional forces transmit appreciable shear between the femoral component and the tibial polyethylene insert, potentially contributing to axial knee rotational constraints and implant loosening [3]. The aim of this study was to investigate transverse plane kinematics and kinetics in connection with the force of friction (FOF) during ADL in patients after TKA and unicondylar knee arthroplasty (UKA) surgery. Materials and Methods: - Motion analysis was performed using a ten-camera 3D- motion capture system (100 Hz, Vicon). - Ground reaction forces were measured utilizing in a total five force plates (1000 Hz, Kistler) - Kinematics and inverse dynamics were calculated with AnyBody Modeling SystemTM (AnyBody Technology). - FOF was estimated of the two articulating artificial surfaces (#CHR: mu_LOWER# =0.12) compared with the cartilage on cartilage friction (#CHR: mu_LOWER# =0.01). The Coulomb model of friction was applied to calculate FOF (Ff=Fn* #CHR: mu_LOWER#). - Completed ADL: level and decline walking, stair descent. - Participants: TKA (n=11), UKA (n=13), controls (CG, n=13). - Statistics: Statistical non-Parametric Mapping (SnPM). Results: No statistically significant differences were detected between the TKA and UKA group, regardless of the locomotion task. Each motor task revealed impaired knee internal rotation angles in the TKA group compared with the CG (Fig. 1, a-c). Fig. 1 (d) clarifies the determining role of the coefficient of friction regarding FOF which showed the highest values during stair ascent and decline walking in all groups. Interestingly, the mentioned tasks exposed lower knee internal moment time series compared with level walking. Lower internal rotation moments might contribute in connection with high friction to the constraint knee internal rotation motion, particularly during ADL including greater normal force values, such as stair climbing and ramp negotiation. Conclusion: Apart from implant congruency in the TKA group, FOF could represent a mechanical resistance, which contributes to the impaired knee motion in the transverse plane. References Smith A, et al., J Orthop Res. 22:260-266, 2004. Komnik I, et al., Gait Posture. 41:370-377, 2015. Wolterbeek N, et al., Gait Posture. 36:394-398, 2012
Influence of friction on knee internal rotation in patients with knee arthroplasties during activities of daily living
