BENCH TESTING OF A TUNABLE ANKLE-FOOT ORTHOSIS WITH ADJUSTABLE STIFFNESS AND NEUTRAL ANGLE

Abstract

Cerebral palsy is the most common childhood motor disability that effects 0.3% of children in the US and two-thirds of them have gait impairment. An ankle-foot orthosis (AFO) is commonly prescribed as a gait assistance. The function of an AFO is maximized when its stiffness and neutral angle are optimally prescribed to address each user’s issue. However, the prescription process is not standardized and is subjective to the prescribing clinician. Only one-third of AFOs improved the user’s gait while another one-third negatively affected the gait. A tunable AFO is developed to allow clinicians to test a range of stiffness and neutral angle of a passive AFO, making the prescription more likely to have a positive effect. The design of tunable AFO has a weight of about a typical plastic AFO and a dimension designed for children. It covers 90% range of stiffness and neutral angle of prescribed AFOs. It can withstand the torque applied during walking. Mechanisms of adjusting both parameters operate fast and are controlled by a microprocessor. A benchtop prototype was built to test the adjustment mechanisms. Both mechanisms were validated.