INTRODUCTION: The plaster bandage technique is a common conventional method for spinal orthosis molding. However, this technique requires a body contact and close distance to patients. To reduce potential risks of unexpected sexual harassment, personal space violation, environmental pollution by plastic waste, and COVID-19 pandemic, the development of non-contact spinal orthosis-molding techniques is highly demanded. Thus, to clarify the usefulness of a recently developed 3D digital scanning technology, we investigated the difference in the adaptability of thoraco–lumbo–sacral orthosis designed by a conventional contact casting technique with a plaster bandage versus by a new non-contact 3D digital scanning technique.

METHODS: We purchased commercially available Japanese mannequins individually simulating an adult man, adult woman, obese adult woman, and child (height 113 cm) (total 4 models), molded and actually made thoraco–lumbo–sacral orthoses based on the plaster bandage technique and on the 3D digital scanning technique (total 8 groups), and compared the fitting adaptability. (1) Corseted mannequins were scanned with a high-precision scanner, the data of which were superimposed to analyze the accuracy of the body shape reproduction. (2) Corseted mannequins were further scanned with computed tomography (CT), in which the gap between the mannequin’s body and orthosis was evaluated by using ImageJ (https://imagej.nih.gov/ij/). The area of the gap was measured and summed up on respectively four consecutive axial CT slices at four different segments (bust, underbust, torso, and waist) for each model (total 16 slices). Then, the percentage of the gap area relative to the mannequin’s body area on each axial slice was calculated. Two-way ANOVA with Tukey post-hoc test was used.

RESULTS: (1) The reproducibility of the mannequin’s shape was higher for the orthosis using the 3D digital scanner (Fig. 1). The difference in the shape reproducibility was distinct particularly in the areas with uneven, curvy surfaces, e.g. the mid-back, protruding ilium, and around the bust. (2) In CT comparison between techniques (Fig. 2), the mean gap in models for an adult man, woman, plus-sized woman, and kid was 12.0%, 17.2%, 9.5%, and 12.0% in the plaster bandage-based orthosis but 8.4% (p = 0.0004), 10.9% (p < 0.00001), 5.4% (p = 0.00003), and 7.8% (p = 0.00001) in the 3D digital scanner-based orthosis, consistently indicating the decreased gap area by the 3D digital scanning technique. Between models, adult woman had the biggest gap by both techniques with significance to all other models by the plaster bandage (all p < 0.00001) but only to obese woman (p < 0.00001) and kid models (p = 0.004) by the 3D scanning.

DISCUSSION: In addition to known advantages of using the non-contact 3D digital scanner including a reduced working time and skill bias in orthotists, capability of molding in the supine position, and no need for patient contact, this pilot study presents an improved accuracy of the thoraco–lumbo–sacral orthosis adaptability. As the next step, we will further collect the data on the 3D digital scanning technology from comparative studies of healthy volunteers and then patients with lumbar deformity.