Design and Additive Manufacturing of a Passive Ankle–Foot Orthosis Incorporating Material Characterization for Fiber-Reinforced PETG-CF15

Abstract

The individualization of patient-specific ankle joint orthoses is becoming increasingly important and can be ideally realized by means of additive manufacturing. However, currently, there are no functional additively manufactured fiber-reinforced products that are used in the field of orthopedic treatment. In this paper, an approach as to how additively manufactured orthopedic products can be designed and produced quickly and flexibly in the future is presented. This is demonstrated using the example of a solid ankle–foot orthosis. For this purpose, test results on PETG-CF15, which were determined in a previous work, were integrated into a material map for an FEA simulation. Therewith, the question can be answered as to whether production parameters that were determined at the test specimen level can also be adapted to real, usable components. Furthermore, gait recordings were used as loading conditions to obtain exact results for the final product. In order to perfectly adapt the design of the splint to the user, a 3D scan of a foot was performed to obtain a perfect design space for topology optimization. This resulted in a patient-specific and stiffness-optimized product. Subsequently, it was demonstrated that the orthosis could be manufactured using fused layer modelling. Finally, a comparison between the conventional design and the consideration of AM-specific properties was made. On this basis, it can be stated that the wearing comfort of the patient-specific design is very good, but the tightening of the splint still needs to be improved.

Experimental characterization, theoretical modeling and failure analysis of the mechanical behavior of acrylonitrile butadiene styrene parts by fused filament fabrication

“…Figure 11 displays the plot of force vs displacement in the foot end, the experimental and numerical results are compared with good agreement. The result of the Figure 11 differs from most similar investigations on orthoses and foot prostheses (Ali et al , 2021; Rochlitz et al , 2018; Steck et al , 2023; Avila et al , 2021; Vijayan et al , 2020). These investigations often use FEM analysis to calculate deformation and equivalent Von Mises stress, which is erroneous when applied to brittle and anisotropic materials, as demonstrated in the present research.…”

The Determination of Assistance-as-Needed Support by an Ankle–Foot Orthosis for Patients with Foot Drop

“…In order to identify this assistance, an approach is required to calculate the optimal support for patients. Therefore, a variety of subjects, gait speeds and pathological situations (different severities of foot drop) are studied to acquire a potential broad representative group of patients as a data basis for the design of a passive AFO which shall be capable of an optimized treatment for foot drop patients [40,41]. Thus, the research question is, how can an approach be realized for determining the optimal AAN support by an AFO for different patients, gait speeds and foot drop severities?…”