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R. Hainisch, M. Gföhler, MG Pandy:
"Computational Simulation of Muscle Function in Crouched Gait in Children with Spastic Cerebral Palsy";
Talk: 6th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2012), University of Vienna; 2012-09-10 - 2012-09-14; in: "CD-ROM Proceedings of the 6th European Congress on Computational Methods in Applied Sciences and Engineering (ECCOMAS 2012), September 10-14, 2012, Vienna, Austria", (2012), ISBN: 978-3-9502481-9-7; Paper ID 2809, 2 pages.

Muscle contributions during motion can be calculated by using individually customized biomechanical models [1], defining appropriate optimization criteria and solving the equations of motion [2-4]. If the movement of the investigated subject is influenced by a motor disorder like cerebral palsy the calculation of muscle function has to take into account effects like spastic muscle reactions or co-contractions.
We created subject specific biomechanical models of children with cerebral palsy and normally developed children of the same age group based on MRI data in a unified and comprehensible process [5]. These models were used to investigate the biomechanics of crouched gait in children with cerebral palsy (Figure 1). The optimization algorithms in the applied biomechanical simulation platform OpenSim [6] are not customized to solve problems with spastic muscle behavior. For solving the static optimization we simulated spastic muscle activation on selected muscles (gastrocnemius, soleus and hamstrings) of the lower limbs to investigate its effect on the function of not affected musculature during crouched gait. The simulated spastic behavior was based on several factors like pre-setting the muscle activations based on the muscle lengthening velocity of the selected muscles during gait, anatomical muscle properties, isometric joint moment measurements and EMG measurements during gait [7-9].
The results indicate that by applying velocity dependent activation on spastic muscles the not affected muscles have to compensate high joint torques while working in sub-optimal regions of their force-length curve. Especially in children the anatomical and mechanical properties of the still growing muscles are affected by this abnormal loading situation. ¬¬¬Further research shall be done to investigate if this method can also be used to simulate spastic behavior of deep lying muscles as iliopsoas.