Design of a Hinge-Mechanism for an Ankle-Foot Orthosis that Increases Versatility and Ease of Use among AFO-Users

Design of a Hinge-Mechanism for an Ankle-Foot Orthosis that Increases Versatility and Ease of Use among AFO-Users

Deken, Jeffrey (TU Delft Mechanical, Maritime and Materials Engineering)

Harlaar, J. (mentor)
Smit, G. (mentor)
Breedveld, P. (graduation committee)

Delft University of Technology

Mechanical Engineering | BioMechanical Design

2021-05-10

Background: The development of ankle-foot orthoses (AFOs) have come a long way over the past decade. However, most improvements are mainly focused on gait performance. Hereby, other tasks are overlooked. This is also stated by AFO- users. AFO-users want an AFO that can be adjusted to suit dierent tasks. An adjustable AFO should allow adjustments for dierent shoes, and improve performance of tasks such as walking slopes, standing up/sitting down. Furthermore, a small, lightweight and durable solution is desired. Aim: The aim of this study is to design and develop a hinge-mechanism for an ankle-foot orthosis that increases versatility and ease of use among AFO-users. Problem Analysis: By talking to an AFO specialist and an AFO-user, insights are gathered that help establish the functional requirements and design specifications. This led to two main functional requirements. The first one is being able to easily adjust the alignment angle of the AFO. The second requirement is being able to lock and unlock the mechanism. This will allow the user to have more angular freedom in the ankle joint. Conceptual Design: To come to a proper design, an overview was made of mechanisms that could fit in the design of the hinge. Using criteria, each mechanism was evaluated and a final design had been chosen. The push-out gear mechanism was chosen to adjust the alignment. For the locking mechanism the locking pin was chosen. Concept Development: During the design process, the mechanism was iteratively improved. The locking mechanism was replaced by a rotating wedge, and the geometry of the mechanism was adjusted to be able to handle the loads. In the end, the mechanism was fabricated which demanded further changes in the design. The housing was 3D-printed, while other parts where laser-cut or turned on a lathe. Evaluation: The final product was evaluated by the same AFO-user and specialist who gave advice at the beginning of this study. Furthermore the design was experimentally tested on holding torque using a load test. Lastly the design specifications were compared to the actual design. Conclusion: In this study, an AFO hinge mechanism was designed and built that increases versatility and easy of use among AFO-users. This was achieved by two mechanisms. A pull-out gear allows to quickly adjust the alignment angle. This allows easy adjustment for wearing different shoes. A rotating wedge mechanism accommodates the (un)locking of the mechanism. Although there are still some improvements to be made, the prototype worked as expected. Also, the prototype was able to bear the load which was set at the beginning of the research. To see its true potential, the mechanism should be fitted inside an AFO. Although this mechanism looks promising, hands-on experience will really tell the added value of an adjustable hinge mechanism.

ankle-foot
orthosis
AFO
hinge
mechanism
alignment
unlocking

http://resolver.tudelft.nl/uuid:117a7486-dddf-4038-88ee-a43141632466

Student theses

master thesis

© 2021 Jeffrey Deken