# Design of a Modular Plantar Orthosis System through the Application of TRIZ Methodology Tools
## 1 Introduction  
The scientific-technological development allows us to increase productivity and efficiency in industries with dynamic and competitive markets [1], such as the medical industry. The application of engineering knowledge to various fields of medicine has contributed to the improvement of medical products, equipment, and services that safeguard the quality of people's lives [2]. The medical devices sector has benefited from the incorporation of engineering principles in its product development and production process optimization to achieve competitiveness in the market through innovative and quality solutions [3]. Innovations in this field refer to the creation of new devices or the improvement of existing ones, through the development of a series of stages that start with the generation of an idea, continuing with the establishment of specifications, and ending with the commercialization of the device [4]. The demand for medical devices has increased in recent years, with demographic aging being one of the factors contributing tothis increase. Orthopedic devices, in particular plantar orthoses, have followed this trend by being considered functional aids to improve people' mobility conditions. In 2015, the global market for plantar orthoses alone reached revenues of 2.6 billion dollars, and it is estimated that by 2021 these will increase by 45% [5]. Plantar orthoses are used in medical practice to treat various conditions of the feet and lower extremities. The safety and efficacy of orthoses are duly supported by various technical and scientific studies. For this reason, there are clinical protocols that prescribe them to achieve correct posture of the feet and reduce pain during standing and walking [6]. Any device that is placed inside a shoe and is in contact with the sole of the foot, can be considered a plantar orthosis. According to their manufacturing process, they can be classified as \"custom-made\" or \"prefabricated\" [7]. The challenge, in both cases, is to make the design of the plantar orthosis consistent with the anatomical features of the foot and the treatment needs based on the condition. Customized insoles achieve a greater approach to that requirement [8]. The complexity of designing a prefabricated plantar orthosis lies in the fact of considering all the possible morphological and pathological variations of a patient's foot. For instance, the height of the medial longitudinal arch of the foot is a very important aspect to consider because the shorter it is, the greater the possibility that the patient will present a foot in pronation, whereas the longer it is, the greater the possibility that a foot in supination is latent [7]. In view of the above, there is an area of opportunity for a prefabricated plantar orthosis design to solve the design challenge that lies in determining the position and height of medial longitudinal arch and heel supports in accordance with the plantar arch and lateral heel deflections [9], as well as the incorporation of transverse arch support to reduce plantar pressure under the metatarsal heads [10] in cases of metatarsalgia that are or are not associated with the height of the longitudinal arch of the foot. There is a wide variety of prefabricated plantar orthoses on the market, the majority of the designs of which have the characteristic of being one-piece systems, cushioned in a specific area and with predetermined fixed supports. The disadvantage of the prefabricated systems is presented in the area of the orthosis where the support has been predetermined, due to the fact that, in many cases, it does not coincide with the plantar region that the patient requires to be attended to. Therefore, clinical professionals believe that a custom-made orthosis has a greater chance of performing the desired function, provided that it is manufactured based on individualized requirements according to the morphology of the foot and the condition to be treated [11].