Bench test validation of a dynamic posterior leaf spring ankle-foot orthosis

Introduction The posterior leaf spring ankle-foot orthosis (PLS AFO) is a unique lower-limb orthosis used to assist dorsiflexion during swing phase, to ensure toe clearance, and to limit falls. The design of the orthosis has changed over time with the use of different materials, fabrication techniques, and trimlines. Materials and Methods In this study, a new material consisting of a carbon-infused polypropylene prepregnated composite was tested against the standard homopolymer polypropylene for a PLS AFO. Nine orthoses were fabricated with three varied ply discontinuous carbon-fiber-infused polypropylene (three orthoses per carbon ply content), and three homopolymer polypropylene orthoses served as the control. Each orthosis was tested in a motorized testing device that measured resistance to torque as the orthosis was cycled through dorsiflexion and plantarflexion. Results and Conclusions The PLS AFOs fabricated with carbon-infused polypropylene composites demonstrated more dynamic mechanical properties, as indicated by increased stiffness and decreased index of hysteresis, than standard homopolymer polypropylene orthoses.