Foot orthoses from a 3D printer

Pressure-sensitive feet are a common and serious problem for diabetics, as well as for people with foot deformities. Customised foot orthoses are the solution, but manufacturing them is resource-intensive and dusty work. What benefits will further developments in the production procedure bring?

Picture: Daniel Seiler, FHNW

Today, customised foot orthoses are made using 3D printers, among other things. As only one material can be processed though, the indispensable different hardnesses within the orthosis are achieved via the structure. In 2021, Daniel Seiler from FHNW in Muttenz was already convinced that advances in 3D printing would give birth to alternatives.

One printer – multiple materials

From the idea to the project: Existing 3D printing procedures either melt a plastic in powder form or harden it as a resin using UV light, and are always limited to one material. Seiler looked into the approach of pushing molten plastic through a nozzle and thus depositing layers of something like plastic spaghetti. The procedure itself is not new and is known as fused filament fabrication (FFF). This allows different materials to be applied in separate layers – in strips. The small team at FHNW developed a printer that has multiple independent print heads, which it autonomously changes during the printing process according to the specified 3D model. It thus deposits plastics of different hardnesses within a single layer: The customised foot orthosis with support structures and soft zones for pressure relief has become reality. A medical technician and a medical computer scientist developed the printer at the FHNW Institute for Medical Engineering and Medical Informatics within a very short time. Daniel Seiler praises the team’s performance and team spirit: “We are proud,” he says, “that a professional triathlete is using a prototype of the foot orthosis and is satisfied with it.” The advantages are obvious: Such orthoses can be manufactured using fewer resources, without toxic resin and, as there is no need for subsequent finishing, without generating any dust. Furthermore, variation in the orthoses’ hardness and elasticity is not only provided by the structure, but also by the material. This brings further possibilities for individualisation and applications, along with increased comfort.

Point-of-care manufacturing as a vision

Foot-data acquisition, diagnosis, design and finally production: The process leading to the finished orthosis involves multiple steps and is manual at the design stage, so it depends on the orthopaedic technician’s interpretation and experience. In future research projects, the diagnosis and design process will be aided by artificial intelligence and partially automated, in order to eliminate this bottleneck for the purpose of scaling up. At the same time, in cooperation with experts from orthopaedic technology company Orthopodo Malgaroli, the possibility of decentralised direct operation of multiple printers at different locations is being evaluated. Diagnosis, measurement, design and production of the orthosis could then take place during a single consultation, which the patient would leave with the finished orthoses in their shoes. Or as Daniel Seiler puts it: “That would be genuine point-of-care manufacturing, production right by the patient’s side.”

The teams at FHNW and Orthopodo Malgaroli already have other applications in mind: Customised foot orthoses can be used not only for therapeutic applications, but also for preventive ones. This opens up the sports market. They also envisage working with other partners, so as to develop the printing of objects for surgeons to practise on, such as bone models with tendons and muscles.

Comprehensive and further information on the subject can be found in the article 3D printing of composites and multi-materials.

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