Using Photogrammetry to Obtain 3D-Printed Positive Foot Casts Suitable for Fitting Thermoconformed Plantar Orthoses

Abstract

The use of photogrammetry provides an inexpensive, alternative method that can simplify the processes traditionally carried out in the orthotics workshop. The objectives of this study are to develop a method based on photogrammetry to obtain 3D-printed positive foot casts for fabricating thermoconformed orthoses from a negative cast in phenolic foam. Using a basic Smartphone, a photo capture protocol for feet, free software and a 3D printer, we tested the suitability of the positive cast obtained to fabricate custom foot orthoses using thermoconformed 3 mm polypropylene in the orthotics laboratory. The results show that digitally fabricated casts provide a very close replicate of the positive casts obtained traditionally through plaster casting (maximum dimension discrepancy between casts of 2 mm in length and 0.4 mm in forefoot, midfoot and rearfoot measurements). They are also suitable for the process of fabricating 2- and 3-mm polypropylene thermoconformed plantar orthoses. Photogrammetry can be used as a new method to obtain a positive 3D foot cast suitable for fabricating custom orthoses, in a valid, safe, cleaner and more lasting procedure that removes the process of plaster casting.