Understanding user practices when drawing up requirements : The case of designing assistive devices for mobility

Patients with orthopedic problems often use assistive devices, e.g., ankle-foot orthoses and therapeutic footwear, to support their mobility. However, many users are not satisfied with their devices or do not use them at all, resulting in a decrease of quality of life. It has been shown that a main cause for dissatisfaction and non-use lies in the process of drawing up requirements. It appears that orthopedic engineers have too little insight in the different areas of life of patients leading to deficient design requirements. In this article a general approach—the so-called Triple I model—is presented to understand the different areas of life of patients. This model offers, in line with and directed by the intention of the International Classification of Functioning, Disability and Health (ICF) model three perspectives or ‘pairs of lenses’ to analyze these areas of life: the identity, the interests of key stakeholders or social actors, and the underlying societal ideals. The Triple I model is elaborated for assistive devices and offers an associated methodology to orthopedic engineers to systematically map the different areas of life of patients, to understand the requirements for every area, and to explore the conditions. In case of assistive devices five different areas of life have to be investigated: daily living at home, work, transport, social and spiritual activities, sport and leisure.