# Design of a Modular Plantar Orthosis System through the Application of TRIZ Methodology Tools
## 1 Introduction
In addition, custom-made systems can satisfy the great variability of design specifications required by health professionals in the absence of guidelines regarding the prescription of plantar orthoses [5]. However, custom-made orthoses also have disadvantages. Firstly, its manual manufacturing process long and laborious, and the skill and experience of the orthotisti is the influential factor in ensuring that the orthosis has the prescribed technical characteristics [12]. Secondly, there is the competitive disadvantage in relation to its cost compared to prefabricated orthoses, whose standardized manufacturing processes allow time and cost optimization [13]. In view of the dilemma of choice between the two types of orthosis for the treatment of certain pathologies, studies have been conducted that conclude that no significant difference is found between custom-made and prefabricated orthoses [14]. The aforementioned issues validate the functionality of prefabricated orthoses for the treatment of certain conditions, implying access to an alternative solution at a lower cost. This paper introduces a plantar orthosis design to be manufactured in a standardized way and with the ability to be customized based on the pathology that the patient exhibits. These characteristics unify the benefits, advantages, and qualities of prefabricated and custom-made systems. The system is intended to reduce the time and cost of manufacturing custom plantar orthoses. The main feature of the design is its modularity. It is divided into four independent components (modules) that are related to each other: plantar base, arch support, metatarsal button, and rearfoot wedge. The plantar base is the central module, while the other three are movable and attachable to it. The coupling is made by means of a bolt-hole assembly mechanism that allows the mobile modules to be positioned in the area required by the patient according to his or her condition. Thus, the proposed system can be configured to avoid pronation or supination movements of the foot, using the arch support and rearfoot wedge, and overloading the metatarsal region, by using the metatarsal button. On the other hand, the design can satisfy the variability of technical specifications that clinical professionals prescribe, due to the autonomy it would give them to configure the system based on their criteria and adapt it to their clinical treatment protocol. The characteristics of the proposed plantar orthosis design were obtained through the application of Theory of Inventive Problem Solving (TRIZ) methodology. This methodology has a set of techniques and/or tools that guide the product development processes from the generation of creative ideas to find innovative solutions [1]. The premises that support the TRIZ philosophy can be summarized as follows: a system is any object that performs a useful function and can contain several subsystems; systems and subsystems are improved and perfected through the elimination of conflicts; an inventive problem represents a conflict between the parameters of a system that cannot satisfy a certain requirement; resolving the conflict without compromising the functionality of the parameters is to find a solution with inventive activity; the principles proposed for the elimination of conflicts are applicable to all fields of knowledge [15]. TRIZ methodology has been applied to the design of new or improved medical devices, such as wheelchairs [16,17], medical care beds [18], joint orthoses [19], and knee rehabilitation devices [20], among others. The authors chose the TRIZ methodology for the following reasons:  
1. They consider it one of the most effective methodologies to generate innovative solutions. 2. There are very few works on its application in the technical field of plantar orthoses. 3. They identified technical contradictions in the design requirements to be developed.