An Orthotic Joint Design for Enhancing Ankle Mobility With Ankle Foot Orthoses Use

Abstract

Articulated ankle foot orthoses (AFOs) are prescribed to treat drop-foot, a common neuromuscular weakness observed after a stroke. These assistive devices prevent the toe from dragging during swing (drop-foot) by providing a resistive moment at the ankle. However, existing ankle joint designs for articulated AFOs introduce additional gait pathologies as they also constrain ankle mobility during stance. A novel ankle joint for AFOs to prevent drop-foot during swing and improve ankle mobility during stance was developed, thereby reducing compensatory knee motion during stance. The design intent was to mimic the unconstrained kinematic response of a nonpathologic ankle at initial contact while preventing drop-foot during swing. The design incorporated two modes of operation: locked during swing for support and unlocked during stance for enhanced range of motion. Proof of concept testing with able-bodied subjects was conducted to test walking ability over level ground based on kinetic and kinematic parameters. The comparative tests confirmed the ability of the novel design to prevent drop-foot and its potential for enhanced ankle mobility during stance. Preliminary results indicate that the novel ankle joint should be refined to facilitate smooth and consistent unlocking but can be safely used in its current form with mobility impaired individuals.