PRINTHOTICS SCAN: OPTIMISING 3D SCANNING FOR THE FABRICATION OF ANKLE-FOOT ORTHOSES

Abstract

Children with neuromuscular diseases and movement disorders are often prescribed ankle-foot orthoses (AFOs) to manage postural and gait impairments. Traditionally, the first step of AFO fabrication is a plaster cast of the foot, ankle and lower leg, which is dependent on clinician expertise and purpose-built workspaces, can be time consuming and generates significant waste material. 3D scanning technologies have the potential to replace plaster casting and contribute to a digital manufacturing workflow, involving 3D printing. Many different types of 3D scanners are commercially available, and Chapter One highlights that there is evidence that some 3D scanners perform better than others when scanning different body regions. However, an extensive evaluation of the role of 3D scanning for the fabrication of AFOs, particularly for children and adolescents, is missing from the literature. Therefore, the aim of this thesis was to develop a comprehensive understanding of the accuracy, speed and feasibility of the 3D scanning process as well as a standardised 3D scanning protocol to advance digital AFO workflows. Chapter Two provides a systematic review comparing the speed, accuracy and reliability of 3D scanning with traditional methods for fabricating orthoses. From the six included studies, 3D scanning appears to be faster especially for experienced users, however accuracy and reliability between methods is variable. Furthermore, there was no clinical evidence of how 3D scanners perform in comparison with traditional methods of fabricating AFOs. Therefore, a series of studies were conducted. In Chapter Three, the development and refinement of the 3D scanning protocol for multiple high-cost and low-cost 3D scanners to capture foot, ankle and lower leg morphology, including preliminary accuracy and reliability testing, was conducted. The 3D scanners tested using a bespoke scanning jig (‘the Scan Stand’) were: Artec Eva (Eva), Structure Sensor (SSI) Structure Sensor Mark II (SSII), Sense 3D Scanner 2nd Gen (Sense), Spectra, Trnio 3D Scanner App for iPhone 11 (Trnio 11), Trnio 3D Scanner App for iPhone 12 Pro Max (Trnio 12). In Chapter Four, the accuracy and speed of the seven 3D scanners to capture foot, ankle and lower leg morphology in 10 healthy participants was evaluated. The Eva, SSI and SSII demonstrated acceptable accuracy. All 3D scanners required less than 5:30 minutes to complete the scan. Overall, the high-cost Eva and low-cost SSII were identified as the best performing 3D scanners and progressed to the next study to evaluate their accuracy and speed against traditional plaster casting in a clinical population. In Chapter Five, 10 children and adolescents prescribed AFOs attending the Sydney Children’s Hospitals Network were 3D scanned with the Eva and SSII using a novel one-person (1p) and two-person (2p) protocol incorporating the Scan Stand. The high-cost Eva and low-cost SSII 3D scanners using the 1p and 2p protocols produced comparable measures of key clinical landmarks compared with plaster cast measures, and were considerably faster, for the fabrication of AFOs in children and adolescents with a neuromuscular or movement disorder affecting gait. In Chapter Six the clinical and research implications of identifying two suitable 3D scanners and scanning protocols for capturing foot, ankle and lower leg morphology of children who require AFOs are discussed.