Passive Orthosis Linkage for Locomotor Rehabilitation

Foot drop is a condition which results from injury to the central nervous system (stroke and head injury) or injuries to the peroneal nerve and is characterized by insufficient dorsiflexion of the ankle during the swing phase of walking gaits, resulting in dragging or slapping of the forefoot or toe during walking. We propose a novel type of ankle-foot orthosis based on a passive four-bar linkage for the rehabilitation, prevention, and treatment of the foot-drop disorder. The linkage is attached to the calf and foot of the patient and passively couples together the motion of the knee and ankle during locomotion. As the knee is bent at the beginning of the stride phase of a walking gait, a curved bar contacts the back of the thigh and the linkage and spring mechanism produces a force to assist the flexion of the ankle at the initiation of the stride phase. An initial wearable prototype has been fabricated and is ready for testing on test subjects to demonstrate the feasibility of the concept and refine the design of the mechanism.