Completion of the DFG project on the design of passive, structurally optimized orthoses for the treatment or compensation of pathophysiological movement patterns
The ability to perform coordinated movements is a central factor in people’s everyday lives. However, various events, such as trauma, strokes, etc., can damage the nerve structures and thus cause motor disorders. The lower leg muscles are frequently affected, resulting in a pathophysiological movement pattern known as “foot drop syndrome”. The preferred treatment for this are ankle-foot orthoses. With the aid of appropriate actuators, active orthoses enable support for both directions of joint rotation. However, the necessary actuators and control units are associated with an increase in weight, which, coupled with a non-trivial energy supply, is disadvantageous for users. Passive orthoses are lightweight and integral, but usually only stabilize or support the ankle joint and have not yet been able to support both joint rotational directions.
The DFG-funded project (450307023) therefore aimed to research a methodology for designing passive, structurally optimized orthoses to support both directions of joint rotation. The research project was a cooperation between the “User-centered design” and “Lightweight design” groups of the KTmfk. The project focuses on a method that allows the lightweight structures on the orthosis to be designed in such a way that their structural response is in symbiosis with the required support in human gait. To this end, the FE model of the orthosis was coupled with musculoskeletal human models to represent the patients to be treated. Using this coupling, the existing movement behavior can be transferred to the ankle-foot orthosis, the resulting stresses in the support structures of the orthosis can be calculated (which results in a support force) and then the effects of this support on the human musculature can be simulated. This makes it possible to identify the appropriate setting or design of the ankle-foot orthosis for patients with certain degrees of muscular weakness and depending on their gait speed to provide optimum support (and therefore the best possible treatment). In addition, a new type of passive ankle-foot orthosis for possible support of both joint rotational directions (PCT/EP2023/083782) was designed during the course of the project, which was then used to evaluate the method.