A Review on Designs of Various Ankle Foot Orthosis (AFO) Used to Treat Drop Foot Disease

Compared to the last few decades, there is an increase in prevalence of neuromuscular diseases like stroke, multiple sclerosis, and cerebral palsy. These diseases cause lower limb disability like drop foot. The main reason for drop foot is weakness in dorsiflexor muscles. Drop foot results in ‘toe drag during swing phase’ and ‘foot slap during heel contact’. Ankle foot orthosis (AFO) is a mechanical device, which is used to treat drop foot. Based on usage of sensors, actuators, and control systems, there are three types of AFOs: Semi active, Active, and Passive AFOs. Semi active and Active AFOs contain sensors, actuators, control systems, and onboard power source. Passive AFOs do not contain electrical boards but contain mechanical elements to control relative motion between foot part and shank part of the AFOs. Based on relative motion between foot and shank parts of AFOs, AFOs are also classified into two types: Non-articulated (or Fixed) and Articulated AFOs. Non-articulated AFOs are single piece devices having no relative motion between foot part and shank part of the device. Articulated AFOs are two-piece devices, having relative motion between foot part and shank part of the device, and the relative motion is controlled by passive and active actuators. In this paper, different working principles, advantages, and disadvantages of the existing AFOs are presented.