Development of a single porous material 3D-printed plantar orthosis to improve recycling and preserve the health of podiatrists

The aim of this study was to develop a 3D-printed plantar orthosis composed of a single, recyclable material without a covering layer. This study had two objectives: the protection of the podiatrist's health during the creation of the orthosis and the reduction of the orthosis's environmental impact. Indeed, currently podiatrist realize thermoformed orthotics using many manual and arduous operations, as well as the handling of numerous glues and toxic substances. In this paper, the developed orthosis mimics the geometrical and mechanical properties of a thermoformed orthosis including specific pores in the orthosis. Firstly, the materials composing the thermoformed orthosis were characterized from a mechanical point of view. Secondly, specific isotropic pores were applied to a solid TPU block. The size of these pores was calculated using finite element analysis to reproduce the behavior of each material of the thermoformed orthosis. Thereafter, a 3D-printed orthosis was produced and an initial trial with one patient yielded promising outcomes; however, further research involving a larger group of patients is required to confirm these findings. Finally, a fatigue test was conducted on a representative sample, showing that the defined solution appears to withstand one year of use. In the future, the goal is to no longer use thermoformed orthosis but to directly design the orthoses using computer-aided design software. This research opens new possibilities for designing personalized plantar orthosis, enabling the adjustments of local mechanical characteristics to address specific pathological requirements.