Development of a 3D printed patient specific Ankle Foot Orthosis

Abstract

Patients diagnosed with drop foot syndrome experience difficulties creating enough clearance during walking, resulting in stumbling over very small obstacles. An Ankle Foot Orthosis is an orthopaedic aid which limits the plantar flexion of the foot, providing a safe walking gait for the patient. Currently, these AFOs are vacuum formed over a machined foam reproduction of the patients leg. The patient specific geometry requirements make it ideal for the one-off production freedom of 3D printing. This master thesis investigated the feasibility of 3D printing a patient specific Ankle Foot Orthosis and explored the possible improvements compared to the current vacuum formed AFOs. The current vacuum formed AFOs provides suboptimal support and increases the energy cost of walking, this was taken into account when deciding the approach for this project. The approach was divided in the creation of an improved walking support and the investigation to other possible improvements of 3D printing.
A new spring system was developed which provided the minimal required support during walking: free dorsiflexion and a constant counter moment during plantar flexion for every ankle. Rigged bending tests which simulated the ankle range of motion showed near perfect support results. However, the improved effect on the patient’s gait could not yet be proven. This was due to an imperfect testing prototype, the required low tolerances of the spring system which could not be met and the fact that the springs were not strong enough.
Several design improvements have been proposed and can be found in the last chapter For COR, the best continuation of this project would be to use the gathered requirements and design improvements to develop a simple ‘plantar flexion stop AFO’. If an orthosis with sufficient support is developed, gradual dynamic improvements can be implemented to allow for more freedom of movement.