Ankle-Foot Orthosis Made by 3D Printing Technique and Automated Design Software

Abstract

We described 3D printing technique and automated design software and clinical results after the application of this AFO to a patient with a foot drop. After acquiring a 3D modelling file of a patient's lower leg with peroneal neuropathy by a 3D scanner, we loaded this file on the automated orthosis software and created the "STL" file. The designed AFO was printed using a fused filament fabrication type 3D printer, and a mechanical stress test was performed. The patient alternated between the 3D-printed and conventional AFOs for 2 months. There was no crack or damage, and the shape and stiffness of the AFO did not change after the durability test. The gait speed increased after wearing the conventional AFO (56.5 cm/sec) and 3D-printed AFO (56.5 cm/sec) compared to that without an AFO (42.2 cm/sec). The patient was more satisfied with the 3D-printed AFO than the conventional AFO in terms of the weight and ease of use. The 3D-printed AFO exhibited similar functionality as the conventional AFO and considerably satisfied the patient in terms of the weight and ease of use. We suggest the possibility of the individualized AFO with 3D printing techniques and automated design software.

Figure 1

The line between the second metatarsal head (MH) and the midpoint (C_T) of the lateral (LM) and medial malleoli (MM) was assumed to be the axis of the foot, and the line between the midpoint (C_T) of the lateral (LM) and medial malleoli (MM) and the midpoint (C_K) of the lateral (LT) and medial tibial condyles (MT) was assumed to be the axis of the lower leg (a). The preprogrammed orthotic template design which size was modified according to the marked points was overlapped (red dots and lines), the circles were drawn around the lateral and medial malleoli, and the oblique line was drawn (blue dots and lines (b)).

Figure 2

In the sagittal view, based on the axes of the foot and lower leg, the ankle joint was adjusted to a neutral position by dorsiflexion (b) and the templates were adjusted according to the meshes (c).

Figure 3

In the coronal view, based on the axes of the foot and lower leg, the ankle joint was adjusted to a neutral position by eversion (b) and the templates were adjusted according to the meshes (c).

Figure 4

Using the adjustment of the joint axis, the 3D modelling of individualized AFO with correction of the axis was designed.

Figure 5

The ankle-foot orthosis made by automated software program was applied to the patient. Shoe laces were used to wear the 3D-printed AFO (b). A conventional AFO without a joint that was made from polypropylene was used for the control (a).

Figure 6

To evaluate the durability of the 3D-printed AFO, a mechanical stress test was performed. At both ends of the AFO orthosis made for the test, round-shaped plastic dummies were inserted and affixed to the machine.

Figure 7

The conventional AFO (blue line) caused the ankle to be in a more dorsiflexed state in the swing phase, compared to the 3D-printed AFO (black line) and without AFO (red line), which caused the least dorsiflexed state. The foot rotation in the transverse plane was corrected the most with the conventional AFO, followed by the 3D-printed AFO, and it was least corrected without an AFO. The ankle eversion was corrected the same with the conventional and 3D-printed AFO.