Colloquia

Summary

Ankle-foot orthoses (AFOs) greatly improve gait in patients with Cerebral Palsy (CP) by restoring ankle-foot biomechanics and minimizing contractures. However, there are certain barriers that hinder their prescription and use as a mobility device in daily-life activities, e.g. they restrict ankle ROM and poorly adapt to different terrains. This thesis thus aimed to develop an adaptable passive push-off mechanism to improve walking in children with CP.
A survey was conducted among the main stakeholders of CP, health care professionals and patients, to discover the points of improvement of current AFO technology. With these results in mind a TRIZ analysis was performed to determine the most promising push-off design for the target group. Subsequently four prototypes of body weight controlled clutches (BWCs) were created. These consist of an assistance spring that is connected to a slider underneath the foot. When body weight is applied to the slider during stance, the slider locks, allowing energy to be saved in the assistance spring, while leaving the ankle free to move during swing. For the BWC to function, proper clutching of the slider is required. The prototypes' friction coefficient, an indication for clutching capacity, was thus determined during technical validation, and mathematical validation was done to determine if the required ankle torque be provided by the system.
Too conclude, a body weight controlled clutch that can provide passive push-off assistance for children with CP was designed. The prototypes generated sufficient friction force for the target group to save energy in the assistance spring, and should theoretically be able to generate sufficient assistance torque around the ankle. For future research, however, the BWC should be tested on real subjects to verify this, and to investigate its benefits for the target group.