Verification of ankle dorsiflexion assist effect by pneumatic artificial muscle for post-stroke patients

Abstract

【Introduction】Many patients with motor dysfunction of the ankle joint after a cerebrovascular accident use an ankle foot orthosis to support the ankle joint. An ankle foot orthosis that supports ankle dorsiflexion torque by a pneumatic artificial muscle has been developed, but its effects have not yet been studied. 【Methods】This study investigated the kinetic and electromyographic effects of orthosis use with or without ankle dorsi‐flexion torque support in two chronic post‐stroke patients. The artificial muscles was set to co‐activate when the foot of the paralyzed lower leg left the ground and flaccid when the foot touched the ground. We calculated the joint angles of the paretic lower limb using attached markers and a video camera. Hip, knee, and ankle flexion‐extension angles during the gait cycle were compared between assisted and non‐assisted gait. Electromyography of the tibialis anterior, gastrocne‐mius, and soleus muscles were measured using surface electromyography. 【Results】The results show the ratio of the stance phase and swing phase in the gait cycle did not change significantly un‐der the assist conditions. Hip and knee flexion motion from the terminal stance to the initial swing were delayed at 5‐10% of the gait cycle with assistance and the activity of the tibialis anterior increased significantly with assistance in one partici‐pant. 【Conclusion】These results implied that the supporting ankle dorsiflexion torque and preventing foot drop in the swing phase alters the movement pattern in the terminal stance and enhances tibialis anterior muscle activity in chronic stroke patients.