Bench testing of a tunable ankle-foot orthosis with adjustable stiffness and neutral angle

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.