Dynamic Modelling And Simulation On Hemiplegia Gait

Stroke,cerebral palsy,polio and other high incidence disease can easily lead to hemiplegia,the disease which cause damage to nerve makes contralateral motor dysfunction,and ultimately may lead to the hemiplegia limbs unable to move.From the perspective of dyskinesia,hemiplegic gait is caused by the disorder of muscle controlled by the nerve.As muscle activity is driving force of walking movement,so hemiplegia gait abnormalities and abnormal muscle activity are closely related.The problem that researchers concerned about are how to get hemiplegia gait patients' muscle strength diagnosis accurately,and make gait rehabilitation after suffering.At present,the study of mechanical properties on joints,muscle soft tissue and other structures is not sufficient due to the complexity of human structure and biological limitations.The domestic walking study also focus on gait analysis and lack of research about relationship between muscle activity and gait.Therefore,this paper analyse the dynamics of hemiplegic gait in the background.First,this paper started from the walking motion capture,using the easonable mechanical model to characterize the role of joint and muscle.The suitable dynamic model was established for gait motion research,and the validity of the calculation was verify.Secondly,the gait model of normal gait and hemiplegic gait were established.Through the research of normal gait characteristics to establish comparison criteria.Then,the comparison between hemiplegic gait and normal gait were discussed to explore the relationship between hemiplegia gait abnormalities and abnormal muscle activities,and investigate the effect of muscle strength adjustment to gait.Specifically,following are the main work and the results of the study accomplished in this paper.First of all,in order to analyze the kinematic and dynamic characteristic of gait motion,an effective gait dynamic model was established based on dynamic capture data.In the process of modelling,the Vicon dynamic capture system was used to get gait data collected.The bone was simplified with rigid body model,and using global trainable element to record the contraction patterns of muscles,so the simulation results can represent the body's muscle activity.After modelling,the effectiveness of the model was verified by comparing joint angle and ground reaction parameters between measured values and simulation results.The results show that the correlation coefficient between measured and simulated lower limb joint angle is 0.958,0.9779 and 0.987,and the maximum angle difference is about 5°,in terms of ground reaction force is 0.945 and 0.937.The measurement is highly correlated with the simulation curve and the difference is small at the particular time,the result prove that the model can be used in gait simulation.After the establishment of kinetic model suitable for gait simulation,in order to study the abnormal characteristics of hemiplegic gait.First,the normal gait model was analyzed as the reference sample.Through the research of gait characteristics,dynamic performance and muscle activity on normal gait,the results show that:In terms of gait motion,the step size and pace maintain normal values,stance phase is about 60%of the gait cycle and the parameters between both sides of the lower limbs have high symmetry.In terms of joint motion,the change of joint angle and moment in initial contact and pre swing have a great influence on gait motion.In terms of dynamic performance,the change of ground reaction force and joint force are bimodal type,and heel strike or toe off shows the maximum value.In terms of muscle activity,the tibial anterior control ankle dorsiflexion in initial contact,the gastrocnemius and soleus control ankle plantar flexion in pre swing.The swing acceleration in initial swing and swing deceleration in terminal swing are due to the effect of iliopsoas and hamstring.Then,the difference analysis between hemiplegic gait and normal gait parameters were made based on the understanding of the normal gait characteristics.Through the analysis of abnormal gait motion and kinetics of hemiplegic gait subjects to explore the association between hemiplegic gait abnormalities and abnormal muscle activity.The research show that:The gait motion abnormalities of hemiplegic are mainly manifested in the asymmetry of the contralateral and ipsilateral lower extremities,the contralateral and ipsilateral step size are smaller,and gait cycle,support time and step width turn larger.In terms of joint motion,the joint motion abnormalities are mainly manifested in sagittal,which ankle joint lack of dorsiflexion in initial contact and lack of plantar flexion in pre swing,and knee,hip joint motion is limited.Combined with joint movement and muscle activity abnormal appearance,the tibialis have no muscle strength in initial contact lead to lack of dorsiflexion which affect the strike phase gait.The gastrocnemius have less muscle strength in pre swing lead to lack of plantar flexion which affect the toe off phase gait.That tibialis anterior and gastrocnemius abnormal muscle strength are the reason for hemiplegic gait.In order to study the effect of abnormal muscle adjustment to gait performance.The tibialis anterior and gastrocnemius muscle strength were adjusted to simulate the effect of muscle training.Using the forward dynamic module of Lifemod to predict the gait motion,the result show that:Muscle strength of tibialis anterior and gastrocnemius have greatly improved after muscle training,and the activity phase show the same performance as normal gait.The improvement of joint motion shows in generation of plantar flexion during initial contact and acceleration of plantar flexion during the pre swing.In the terms of dynamic performance,after muscle training,the differences between contralateral and ipsilateral lower limbs are reduced,and the abnormal performance of ground reaction force have improved in initial contact and pre swing.For the hemiplegic patient,the tibialis anterior,gastrocnemius muscle training will help to improve the gait motion.