Ankle-Foot Orthosis and Footwear Interactions in Adult Healthy and Patient Populations: Systematic Review of Biomechanical Outcomes

BACKGROUND Both ankle-foot orthoses (AFOs) and footwear adaptations are used to improve gait across a broad range of neuromuscular disorders. AFOs and footwear can each independently influence gait through the manipulation of certain design parameters, such as AFO footplate stiffness or the use of a forefoot rocker. While the effects of design parameters from AFOs and footwear on gait have been investigated independently, how these parameters interact to influence walking biomechanics remains poorly understood. OBJECTIVE This systematic literature review aims to provide an overview of the interacting effects between AFOs and footwear on gait biomechanics from both a theoretical standpoint and through the synthesis of existing literature. METHODS A search of existing literature was conducted across 4 major databases. Studies were eligible if they included adult participants from healthy or patient populations. Studies included should have investigated biomechanical gait outcomes recorded during walking with an AFO and at least two different footwear conditions. Quality assessment was performed using the Downs and Black checklist and AFO reporting guidelines. RESULTS A total of 14 studies were included in this review. Across these 14 studies, a total of 204 participants (108 healthy, 84 patients after stroke, and 12 unilateral ankle weakness or pain) were included. The majority of these studies were within-subjects designs. Footwear adaptations were primarily changes to the heel-sole differential (HSD; 7/14), followed by forefoot rockers (5/14), with some studies on changes to heel shape and hardness (3/14), and a study on mediolateral wedging. These adaptations were used in combination with primarily rigid AFOs (10/14), with studies also using dorsiflexion-free and frontal plane restrictive AFOs. CONCLUSIONS Increasing the HSD can be used to increase knee flexion across the stance phase in rigid AFO users, including in the third rocker when HSD is manipulated between the shoe and AFO. Beyond changing the HSD, there is a lack of well-designed experimental studies exploring footwear adaptations. Detailed reporting of both AFO and footwear design choices is necessary for future work in order to make informed statements on biomechanics.