Comparison of 3D scanning versus traditional methods of capturing foot and ankle morphology for the fabrication of orthoses: a systematic review

Abstract

Background In the production of ankle-foot orthoses and in-shoe foot orthoses, lower leg morphology is traditionally captured using a plaster cast or foam impression box. Plaster-based processes are a time-consuming and labour-intensive fabrication method. 3D scanning is a promising alternative, however how these new technologies compare with traditional methods is unclear. The aim of this systematic review was to compare the speed, accuracy and reliability of 3D scanning with traditional methods of capturing foot and ankle morphology for fabricating orthoses. Methods PRISMA guidelines were followed and electronic databases were searched to March 2020 using keywords related to 3D scanning technologies and traditional foot and ankle morphology capture methods. Studies of any design from healthy or clinical populations of any age and gender were eligible for inclusion. Studies must have compared 3D scanning to another form of capturing morphology of the foot and/or ankle. Data relating to speed, accuracy and reliability as well as study design, 3D scanner specifications and comparative capture techniques were extracted by two authors (M.F. and Z.W.). Study quality was assessed using the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) and Consensus-Based Standards for the Selection of Health Measurement Instruments (COSMIN). Results Six articles met the inclusion criteria, whereby 3D scanning was compared to five traditional methods (plaster cast, foam impression box, ink footprint, digital footprint and clinical assessment). The quality of study outcomes was rated low to moderate (GRADE) and doubtful to adequate (COSMIN). Compared to traditional methods, 3D scanning appeared to be faster than casting (2 to 11 min vs 11 to 16 min). Inter-rater reliability (ICC 0.18–0.99) and intra-rater reliability (ICCs 0.25–0.99) were highly variable for both 3D scanning and traditional techniques, with higher agreement generally dependent on the foot parameter measured. Conclusions The quality and quantity of literature comparing the speed, accuracy and reliability of 3D scanning with traditional methods of capturing foot and ankle morphology is low. 3D scanning appears to be faster especially for experienced users, however accuracy and reliability between methods is variable.

3D shape measurement techniques for human body reconstruction

“…The plaster mould accuracy, acceptable for medical applications is above 15 mm [9], [10]. The uncertainty of the reconstruction for this multimodal non-contact measurement methodology is within this limit in fact the maximum uncertainty is 8.2 mm.…”

“…In the past, customization has often been sacrificed in favour of manufacturability, however, with the advent of 3D printing [1], this shortcoming is being overcome [2], [3], and more and more emphasis is being given to the necessity of providing fast and accurate systems to obtain the geometry of the whole body [4], [5], [6] or of specific body segments [7]. Traditional techniques are based on plaster moulds and are affected by some major limitations such as: the invasiveness, the need to keep the patient still for the curing time [8], a limited accuracy (over 15 mm, according to [9], [10]), and the impossibility of acquiring undercut geometries. More recently, and as a viable alternative, various non-contact instruments have been developed in order to perform digital scanning [11], [12], [13] and the respective performances have been extensively reported in literature [14], [15].…”

Animal orthosis fabrication with additive manufacturing – a case study of custom orthosis for chicken

“…Nevertheless, as reported in another paper, there are some difficulties in performing a limb scan. Even in humans, it is difficult to maintain the required posture during 3D scanning, and even slight uncontrolled shaking of the limb can cause partial deformities or distortions to appear on the final scan (Farhan et al , 2021). Therefore, in the case of an animal, it would probably be necessary to prepare an instrument to immobilize the limb.…”

Experimental Analysis of Commercial Optical Methods for Foot Measurement

“…Another often used method for digitizing and measuring feet is 3D cameras [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. There are different technologies, such as passive stereo, active stereo (e.g., structured light) and time of flight (ToF).…”