Experimental Study of Ankle Joint Pushing Mechanism Concerning About the Horizontal Movement of Talus

Abstract

An ankle joint pushing system that absorbs the horizontal movement of the talus is proposed, and the effects of the horizontal movement absorbing mechanism in the system are examined. The bending of the ankle joint is an important medical treatment that physical therapists (PTs) utilize to help their patients recover their ability to walk and to prevent contracture. However, since the ankle treatment requires a large amount of force (nearly equal to the subject’s weight) plus precise angle and power control, manual treatment by PTs has not been replaced by mechanical treatment systems. In order to realize the mechanization of the ankle joint pushing treatment, the system developed here uses two features. (1) The proposed device fixes the ankle joint position correctly by making contact with the Achilles tendon, the back of the calf, and the hip. (2) The bucket rotation center shifts its position horizontally with the movement of the talus when the foot is pushed back. This mechanism can push the toes or any part of the foot strongly and stably without causing the patient any pain. It can also stretch the biceps femoris and gastrocnemius muscles simultaneously, which could previously only be done by a physical therapist. During 73 N stretching treatment tests done on four subjects, 22.2 mm (S.D. 6.4 mm) horizontal (ventral direction) movements of the ankle joint were observed due to the movement of the talus, and our proposed device mechanism successfully suppressed the movement to a 1.8 mm (S.D. 1.3 mm) horizontal (ventral) movement in the same 73 N stretching treatment.