Tailoring Ankle-Foot Orthoses Stiffness to End-Users' Needs: Which Performance Variables Matter?

Ankle Foot Orthoses (AFOs) are devices designed to assist or rehabilitate gait. The stiffness of the AFO is an important parameter that needs to be tailored to the enduser's characteristics. However, the lack of clinical guidelines for optimizing AFO stiffness has led to inconsistent outcomes and low user satisfaction in existing experimental approaches. This inconsistency may stem from two reasons: (1) the limited number of variables considered by these methods, which may fail to capture the full complexity of gait; and (2) the variability in the relationship between stiffness and gait variables among users. To address these challenges, we propose a user-tailored optimization framework that identifies and incorporates relevant gait variables based on individual needs and preferences. In this pilot study, we explore key performance variables in two participants with cerebral palsy (CP), analyzing the results using XGBoost and SHAP values. Our findings highlight the importance of multiple performance variables in capturing gait complexity and reveal that the most relevant variables differ between participants. This study underscores the potential of personalized approaches to improve AFO optimization and user outcomes.