Drop foot is caused by damage to the peroneal nerve or muscle weakness or paralysis. The forefoot is unable, or has difficulty performing dorsiflexion (moving the ankle and toes upwards / controlled by the tibialis anterior, extensor hallucis longus, and extensor digitorum longus muscles), so as the foot swings forward during walking the toes don’t lift and they drag on the ground. Tripping and instability are common. To overcome this lack of dorsiflexion a person will often bend their hips and knees so the foot can be lifted higher to prevent the toes dragging along the ground (this is known sometimes as steppage gait). Conventional foot and leg braces are quite bulky so a relatively new device called the ActiGait®, an implantable foot stimulator, to control ankle joint movement and life the toes during walking will be a welcome relief for some people.
The control unit: worn on a belt around the waist
The antenna: signals are sent through the skin to the implant
The receiver unit (implant): implanted into the thigh, receives a signal and converts it into a stimulation pattern.
The cuff electrode: surrounds the Common Peroneal Nerve which activates the muscles on the front of the lower leg which control the amount of inversion and eversion to allow balanced dorsiflexion.
The heel switch: worn in the shoe, registers heel lift and heel strike