Adjustable Stiffness AFO Enhances Gait Performance Compared To Traditional AFO In Individuals With Cerebral Palsy

Ankle foot orthoses (AFOs) are prescribed to individuals with cerebral palsy (CP) to improve walking performance. However, their rigid design restricts ankle range of motion and push-off power during walking and can interfere with other functional tasks of daily living. PURPOSE: To evaluate a novel adjustable stiffness AFO design while individuals with CP completed standing, walking, and sit-to-stand tasks. METHODS: 11 individuals, aged 11 to 40 years, completed a 6-minute treadmill walking task and three daily living tasks (stable standing, sit-to-stand, overground walking with cone navigation) while wearing the adjustable stiffness AFO (a-AFO), a traditional solid AFO (s-AFO), and with no assistive device (shod). Lower limb kinematics, kinetics, and EMG of the soleus and vastus lateralis (VL) were recorded during treadmill walking. Center of pressure (COP) data was collected during the stable standing task and participants’ device stiffness preferences were recorded for daily living tasks. RESULTS: While wearing the a-AFO at their preferred stiffness setting, participants walked with 24% greater ankle push-off power compared to the s-AFO (p = .003), and soleus and VL EMG activity was reduced by >12% compared to shod (p < .040). Further, ankle initial contact angle and joint excursion improved by 5° during the a-AFO compared to the s-AFO condition (p < .001) without affecting knee or hip kinematics. During stable standing, anterior-posterior COP profiles were affected by the stiffness setting with lower stiffness resulting in increased stability (p < .025). Of the nine participants who communicated a device stiffness preference (high, middle, and low stiffness), five preferred a different stiffness for at least one task, while four preferred the same stiffness for all tasks. CONCLUSION: The a-AFO improved walking performance, as evidenced by improved ankle push-off power and ankle kinematics without increasing muscle activity. The a-AFO design also has potential to improve participants' performance in other tasks of daily living. Designing an AFO that meets individual needs, task demands, and disability characteristics remains a critical goal that we will continue to contribute towards. Supported by: This project was supported in part by the Eunice Kennedy Shriver National Institute of Child Health & Human Development of the National Institutes of Health under Award Number R41HD113494