Biomechanical Study Of Compensation Strategy For The Stroke Survivors With Knee Extensor Spasticity For Obstacle Crossing

Purpose:Obstacle crossing is a common task in community ambulation.The healthy people can effectively complete the task of obstacle crossing by using simple knee flexor or hip flexor strategy.However,The stroke survivors with motor impairments need to adopt adjustment and movement compensatory strategies for safe and successful obstacle crossing.Spasticity,as a common clinical manifestation of sequelae of stroke,will affect the input of proprioception,inter-segmental coordination and balance control,and may further affect the choice of strategies for stroke patients to obstacle crossing.However,there are few researches on strategies for the stroke survivors with knee extensor spasticity for obstacle crossing.This study will use biomechanical research methods to explore the changes of joint kinematics,dynamics and muscle activation mode of lower limbs when the patients with knee extensor spasticity obstacle crossing,and explore the compensatory strategies,motor control mechanism.To provide theoretical reference and data support for the rehabilitation treatment of stroke patients with knee extensor spasticity.Methods:Twenty-four stroke patients were recruited and divided into a spasticity group(MAS≥1)and a non-spasticity group(MAS=0),based on the MAS score of the knee extensor.Subjects were instructed to walk at a self-selected speed on a 10-m walkway and step over a 15 cm obstacle without touching or losing balance.Visual 3D v6 was used to calculate the joint Angle,joint moment,muscle integral EMG and knee,ankle muscle co-contraction index during obstacle crossing.The independent sample t-test was used to compare the differences in each indicator of stroke patients with two functional levels,The significance level was set at 0.05.Results:1)Compared with the non-spasticity group,the spasticity group had lower step speed and shorter step length when obstacle crossing,longer initial and terminal double support phases,and shorter single support phases on the affected side.2)The mediolateral directions COM velocity of stroke patients in the spastic group was higher than that in the non-spastic group when the affected leading foot clearance during obstacle crossing;The COM-COP distance in the mediolateral directions of stroke patients in the spastic group was higher than that in the nonspastic group when the healthy side trailing foot clearance during obstacle crossing.3)In the spasticity group,leading toe-obstacle distance,leading heel-obstacle distance,and trailing heel-obstacle distance were all smaller than those of the non-spasticity group.4)When the affected leading limb obstacle crossing,the rotation of the trunk and pelvis and the abduction of the lower limbs were increased in the spasticity group compared with the non-spasticity group.The healthy side supporting limb reduced the extension of the hip joint and increased the knee flexion.The contralateral swinging limb showed greater hip flexion in the spasticity group than in the nonspasticity group when the trailing limb obstacle crossing.5)When the affected leading limb obstacle crossing,the flexion moment of the hip and ankle joints in the swing leg of the spasticity group was larger than that in the non-spasticity group,and the flexion moment of the supporting leg was also larger.The flexion moment of the hip joint of the swinging leg of the healthy side in the spasticity group was smaller than that in the non-spasticity group when the healthy side trail limb obstacle crossing6)During the initial double support period,the integral EMG of rectus femoris in the spasticity group was larger than that in the non-spasticity group;At the terminal double support period,the integral EMG of tibialis anterior muscle,lateral gastrocnemius muscle and biceps femoris in the spasticity group was larger than that in the non-spasticity group.During the single support period of the affected side,the integral EMG of tibialis anterior muscle and rectus femoris in the spasticity group was larger than that in the non-spasticity group.7)Compared with the non-spasticity group,the muscle co-contraction index of the knee joint and ankle joint of the terminal double support phased and the knee joint of the affected side of the single support phase were greater in the spasticity group.Conclusions:1)In the spasticity group,the decrease of leading heel-obstacle distance and trailing heel-obstacle may increase the risk of falling,which can be used as a reference indicator to predict the risk of falling in motion.2)The tilt and rotation of the pelvis and trunk in the spasticity group impair the stability of mediolateral directions to some extent.It is suggested that it is necessary to pay attention to the strength training of the trunk and pelvis in the rehabilitation training,strengthen the control capacity of the trunk and pelvis,and enhance the stability during exercise.3)When obstacle crossing,the affected side spasticity will also have a certain influence on the lower limb torque of the healthy side.This phenomenon suggests that in the process of rehabilitation training,not only attention should be paid to the training of the affected side,but also effective control training should be carried out on the healthy side,so as to avoid the formation of abnormal gait with problems on both the healthy and the affected side.4)In the spasticity group,the stability of the affected side was compensated for by the abnormal agonist-antagonist co-contraction of the affected side.Although energy consumption may be increased and fatigue may be caused,it is helpful to promote the body support,maintain the stability of the lower limb joints,and help to successfully cross the obstacle.