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WP11: Modelling and simulation for NNDThomas Geijtenbeek, Frans van der HelmDelft University of TechnologyAmsterdam 23-24 February 2015Status of the WPT11.1 Construction of a scalable mass distribution modelLiterature study on sensitivity of scaling methodsProcess results from joint center calibrationAmsterdam 23-24 February 2015Status of the WPT11.2 Development of a personalized disease specific skeletal modelFunctional calibrationFind joint rotation centers and axesScale segment lengthsScale segment weightsMRI recordingsMuscle volume Physiological Cross-Sectional AreaMuscle optimum length from cadaver studies & scaledVia points muscle attachmentsFinally through Statistical State Model

Amsterdam 23-24 February 2015Scaled musculoskeletal modelsConstructing a scaled modelBrussels 6-7 May 2014

Functional joint center calibration

Status of the WPT11.3 Construction of a disease specific muscle modelPlan to include spasticity model from VUMC (Van der Krogt et al.)Muscle constraints:Contractures: Passive constraintsAberrant reflexes: low threshold on muscle contraction velocity reflex

Amsterdam 23-24 February 2015 Spastic controller: increased stretch reflex (vdKrogt et al., 2015)If: Stretch velocity of muscle fibers > Threshold

Then: Spastic excitation ( t + Delay ) = Gain * stretch velocity

lead to efferent impulses causing contractionAfferent impulses from spinal cord Threshold: extracted from data Delay: fixed to 30 ms Gain: individually tuned (0-4)METHODS Force-length curves - with optimal stiffness parametersCerebral Palsy (CP) vs Typically Developing (TD) vdKrogt et al. (2015)0.511.500.511.5Relative fiber lengthRelative fiber force ActiveDefault passiveTD hamstringsCP hamstringsTD vastiCP vastiRESULTSStatus of the WPT11.4 Design of models driven by the dynamics of gait perturbationsOpenSim model (available)Gait2392 model23 DOF92 musculotendon actuators representing 76 musclesTo be adapted by available gait and morphological dataOptimization toolbox (connected) Covariance matrix adaptation (CMA)Neural control signal, feedback parametersUnknown model parametersPredictive simulations (in progress)OptimizationSimulate optimal neural control model in pathological stateMimick pathological gaitPredict optimal neural control after therapeutic interventionPrediction of outcome after intervention and rehabilitation practiceUse gait data + EMG for validationAmsterdam 23-24 February 2015Predictive SimulationsFind optimal gait pattern for any given musculoskeletal modelUse high-level optimization criteriaTarget speedMetabolic energy expenditureMethod does not require motion capture dataCan be used for validationCan incorporate neuromuscular deficiencies

Amsterdam 23-24 February 2015Adapt to Model ScalingAmsterdam 23-24 February 2015

The Optimization Process

Amsterdam 23-24 February 2015Adapt to Target SpeedAmsterdam 23-24 February 2015

Find Optimized Muscle AttachmentsAmsterdam 23-24 February 2015

What we are going to present to the EC (Annual review)Significant resultsUse cases Amsterdam 23-24 February 2015Current open issuesIssues/criticalitiesCorrective actionsAmsterdam 23-24 February 2015