Page 57 - Demo

ACL reconstruction is not the only factor controlling tibial rotation553All jump trials were performed with hands in free motion and with sports shoes on. To familiarize subjects with the procedure and to make sure the entire foot landed on the force plate, subjects were asked to perform a dry run of the SLHD consisting of three practice trials. The median of the three practice hops was used to determine the starting distance from the force plates. For the side jump, leg length (greater trochanter tip to lateral malleolus tip) was used to determine the starting distance. Three approved trials per task were recorded for each knee to minimize the chances of data loss. Trials were approved when tasks were performed correctly (i.e. stable landing for at least 3 seconds), the entire foot landed on the force plate, and all markers were left in place. Approximately 13 months after the first trial – 12 months after ACLR – the testing procedure was repeated.Data processingThe positions of the markers provided data to determine pelvic, femoral, tibial and foot segments. Using VICON Nexus software v2.8 and an additional custom MATLAB v9.7 script (The MathWorks Inc., Natick, MA, USA), threedimensional angular displacements and translations in the knee joint were calculated. Data processing and analysis started at initial contact and continued for 200ms. Initial contact was defined as the moment at which the vertical ground-reaction force (GRF) was >5% of the body weight. All data were smoothed using the cross-validated quintic spline. Raw 3D marker position data were filtered using a low-pass frequency convolution filter of 10Hz with zero lag. A maximum gap (temporary absence of marker identification) of ten frames was accepted to fill in using the software. If a trial contained gaps exceeding 2.5 ms smoothing of the data could not be performed and was therefore rejected. If at least two successful trials were available for a kinematic variable, the variable was included in the analysis. Kinematic variables quantified and included were: maximum knee flexion, maximum knee extension, maximum knee valgus, maximum knee varus, anterior tibial translation, range of tibial rotation and knee flexion moment. Knee flexion moment was calculated from the GRF vector and its lever arm to the centre of the knee of the stance leg. To quantify anterior tibial translation and knee angles, two coordinate systems were reconstructed in the tested knee using the customized MATLAB script based on the Mark Zee.indd 55 03-01-2024 08:56