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Session: Poster session I
Session starts: Thursday 24 January, 15:00

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Eline Flux (Amsterdam UMC, Vrije Universiteit Amsterdam, Department of Rehabilitation Medicine, Amsterdam Movement Sciences, de Boelelaan 1117, Amsterdam, the Netherlands)
Jaap Harlaar (Amsterdam UMC, Vrije Universiteit Amsterdam, Department of Rehabilitation Medicine, Amsterdam Movement Sciences, de Boelelaan 1117, Amsterdam, the Netherlands & Delft University of Technology, Dept. Biomechanical Engineering)
Marjolein van der Krogt (Amsterdam UMC, Vrije Universiteit Amsterdam, Department of Rehabilitation Medicine, Amsterdam Movement Sciences, de Boelelaan 1117, Amsterdam, the Netherlands)

Abstract:
Multiple models exist to assess gait kinematics, with different underlying marker sets and biomechanical models. This study assessed differences between two conventional and one more recently developed model for gait analysis in children with cerebral palsy. Furthermore, effects of different measurement sites were analyzed and reliability in knee axis alignment was determined. Twenty-five children with cerebral palsy participated. 3D instrumented gait analysis was performed in three laboratories across Europe, using a comprehensive retroreflective marker set including three models: the Newington Model [1], known as Plug-in-Gait (PiG), the calibrated anatomical system technique (CAST)[2] and the Human Body Model (HBM)[3]. Kinematic outcomes from the models were compared using statistical parametric mapping (SPM) and RMSE values were used to quantify differences. Sagittal plane outcomes were comparable (discrepancies between models were less than 5°) for most comparisons, whereas for frontal and transversal planes, differences for almost all segment and joint angles exceeded the threshold for possible influence on clinical decision-making (i.e. >5°). Furthermore, an interaction effect between model and measurement site was found, which suggests a possible influence of specific marker placement experience of researchers, although this should be further studies in future researches, for example by analyzing the same patients in multiple laboratories. CAST and PiG knee adduction angles showed low reliability, with data collected using an online optimization method showing higher reliability, while HBM constrains frontal and transversal knee movements. It can be concluded that studies using different models cannot be compared, especially with respect to the frontal and transverse plane kinematics. A translation algorithm needs to be developed for comparing output from different marker models, taking into account the offsets, relative errors and error band. [1] Davis, Hum Mov Sci 10 (1991) 575-587 [2] Cappozzo, Clin Biomech 10 (1995) 171-178 [3] Van den Bogert, Med Biol Eng Comput 51 (2013) 1069-1077