March 2022


Foot orthoses (FOs) have been prescribed for an array of lower limb issues as their geometrical design and material properties have been shown to influence their impact on foot biomechanics. 3D-printing offers the potential to customize the shape of FOs, as well as add new functionalities with add-on components. The potential impact of newly designed 3D-printed FOs was examined by researchers based at the University of Montreal in Canada, first in healthy people,1 then in people with flexible flatfoot.2

In the first study,1 the researchers sought to understand the effect of stiffness and new postings on foot kinematics and plantar pressures in 15 healthy people with normal foot posture. They created 2 pairs of ¾-length FOs with different stiffness levels and innovative flat postings that could be added at the rear. They recorded multi-segment kinematics and plantar pressures while participants walked on a treadmill.

They found that increasing the stiffness altered foot kinematics (by reducing rearfoot eversion and increasing abduction) and that the rearfoot postings enhanced the FOs impact on frontal rearfoot kinematics. Greater plantar pressures were observed in the midfoot as the new FOs appeared to have shifted the pressures from the rearfoot. Higher peak pressures—up to 31.7%–under both the rear- and mid-foot were also observed.

The group concluded that 3D printing offers a host of new possibilities in terms of material properties and design, allowing for more customized FOs and they called for studies in special populations to better understand the full potential.

In the second study,2 a related group turned its attention to patients with flexible flatfoot. This study sought to examine the effect of 3D-printed FOs’ stiffness and the newly designed post on muscle activity, plantar pressures, and center of pressure displacement in people with flatfeet. This group looked at 19 patients, again designing 2 pairs of FOs 3D printed with different stiffness levels with the potential to add the rear post. Muscle activity, plantar pressures, and center of pressure displacement were recorded during walking.

They found no alteration in muscle activity time. The most notable changes in plantar pressures were observed in the midfoot area where both peak and mean pressures and contact area increased significantly in the 3D-printed FOs. Increasing FO stiffness altered plantar pressure distribution. The FOs had little effect on center of pressure displacements during walking.

This group concluded that stiffness in the FOs mainly altered the plantar pressures in the midfoot region, while the new post design affected the pressures under the rearfoot.

Source: 1. Desmyttere G, Leteneur S, Hajizadeh M, Bleau J, Begon M. Effect of 3D printed foot orthoses stiffness and design on foot kinematics and plantar pressures in healthy people. Gait Posture. 2020;81:247-253. 2. Cherni, Y, Desmyttere G, Hajizadeh M, Bleau J, Mercier C, Begon M. Effect of 3D printed foot orthoses stiffness on muscle activity and plantar pressures in individuals with flexible flatfeet: A statistical non-parametric mapping study. Clin Biomechanics. 2022;92:105553.

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