Stiffness modification of two ankle‐foot orthosis types to optimize gait in individuals with non‐spastic calf muscle weakness – a proof‐of‐concept study

Source abstract

Abstract Background To reduce gait problems in individuals with non‐spastic calf muscle weakness, spring‐like ankle‐foot orthoses (AFOs) are often applied, but they are not individually optimized to treatment outcome. The aim of this proof‐of‐concept study was to evaluate the effects of modifying the stiffness for two spring‐like AFO types with shoes‐only as reference on gait outcomes in three individuals with calf muscle weakness due to polio. Methods We assessed 3D gait biomechanics, walking speed and walking energy cost for shoes‐only and five stiffness conditions of a dorsal‐leaf‐spring AFO and a spring‐hinged AFO. Outcomes were compared between stiffness conditions in the two AFOs and three subjects. Results Maximum ankle dorsiflexion angle decreased with increasing stiffness in both AFOs (up to 6–8°) and all subjects. Maximum knee extension angle changed little between stiffness conditions, however different responses between the AFOs and subjects were observed compared to shoes‐only. Walking speed remained unchanged across conditions. For walking energy cost, we found fairly large differences across stiffness conditions with both AFOs and between subjects (range 3–15%). Conclusions Modifying AFO stiffness in individuals with non‐spastic calf muscle weakness resulted in substantial differences in ankle biomechanics and walking energy cost with no effect on speed. Our results provide proof‐of‐concept that individually optimizing AFO stiffness can clinically beneficially improve gait performance.