A Randomized Controlled Trial to Evaluate the Clinical Effectiveness of 3D-Printed Orthosis in the Management of Adolescent Idiopathic Scoliosis

Yangmin Lin, PhD; Jason Pui Yin Cheung, MBBS, MMedSc, MS, PDipMDPath, FHKCOS, FHKAM, FRCSEd; Chi Kwan Chan, MSc; Sidney Wing Fai Wong, MSc; Kenneth Man Chee Cheung, MBBS, MD, FRCS, FHKCOS, FHKAM; Martin Wong, PhD; Wun Ching Wong, BSc; Prudence Wing Hang Cheung, BDSc (Hons); Man Sang Wong, CPO PhD, FHKSCPO, FISPO


Spine. 2022;47(1):13-20. 

In This Article

Abstract and Introduction


Study Design: Prospective randomized controlled trial.

Objective: To compare clinical effectiveness and quality of life (QoL) of the 3D-printed orthosis (3O) and conventional orthosis (CO) for adolescent idiopathic scoliosis (AIS).

Summary of Background Data: Using 3D printing technology to design and fabricate orthoses to manage AIS aiming to improve in-orthosis correction and patients' compliance that are considered essential factors of effective treatment. Clinical evaluation was conducted to study the effectiveness of this innovative method.

Methods: Thirty females with AIS who met the criteria (age 10–14, Cobb 20–40°, Risser sign 0–2, ≤12 months after menarche) were recruited. Subjects were randomly allocated to the 3O group (n = 15, age 12.4, Cobb 31.8°) and CO group (n = 15, age 12.0, Cobb 29.3°). All patients were prescribed for full-time wearing (23 hours/d) and follow-up every 4 to 6 months until bone maturity. Compliance was monitored by thermosensors, while QoL was assessed using three validated questionnaires.

Results: Comparable immediate in-orthosis correction was observed between 3O (−11.6°, P < 0.001) and CO groups (−12.9°, P < 0.001). In the QoL study via SRS-22r, the 3O group got worse results after 3 months in aspects of function, self-image, and mental health (−0.5, −0.6, −0.7, P < 0.05) while the CO group had worse results in aspects of self-image and mental health (−0.3, −0.3, P < 0.05). No significant difference was found in QoL assessments between groups. After 2 years of follow-up, 22 patients were analyzed with 4 dropouts in each group. Comparable angle reduction was observed in both groups (3O: −2.2°, P = 0.364; CO: −3.5°, P = 0.193). There was one subject (9.1%) in the 3O group while two subjects (18.2%) in the CO group had curve progression >5°. Daily wearing hours were 1.9 hours longer in the 3O group than the CO group (17.1 vs. 15.2 hours, P = 0.934).

Conclusion: The 3O group could provide comparable clinical effects as compared with the CO group while patients with 3O showed similar compliance and QoL compared to those with CO.

Level of Evidence 1


Adolescent idiopathic scoliosis (AIS) is a three-dimensional (3D) spinal deformity diagnosed with coronal Cobb angle >10°,[1] affecting approximately 1% to 4% of adolescents.[2] Though orthotic treatment has been reported effective to prevent curve progression for moderate AIS (Cobb 20–40°),[3] its treatment effectiveness can be influenced by various factors, such as the orthotic design[4] and patient's compliance.[5]

With the rapid development of computer-aided design and computer-aided manufacture (CAD/CAM), 3D printing technology embraces the advancements of direct prototyping and more flexibility of design, and it could be one of the outstanding technologies of CAD/CAM for spinal orthosis.[6] Direct prototyping can avoid accumulated errors during the manual fabrication procedures, which could reduce deviations from the original biomechanical design. Furthermore, the orthosis thickness and weight could be reduced to enhance the patient's comfort level. In a pilot test, one 3D-printed orthosis (3O) (via Fused Deposition Modelling, FDM with Nylon-12), as well as one conventional orthosis (CO) (via Manual Method with polyethylene, PE), were fabricated for a normal female subject. The thickness was 3 mm (50% thinner), and the weight was 0.4 kg (31% lighter) when compared between the 3O and CO. These may improve the patient's compliance with the orthotic treatment and subsequent treatment outcomes. Besides, the involved orthotist could save 4.8 man-hours in the design and fabrication of orthosis in the 3D printing method as compared with the conventional method.

3D-printed spinal orthoses have been proposed to be used in AIS by some commercial companies.[7] With variations in the material and fabrication method applied in 3D printing, the biomechanical effect, and treatment outcome of spinal orthosis in AIS may be affected. Although extensive researches have been conducted in 3D-printing for foot and hand orthoses,[6] no single study has gathered enough clinical evidence of the application of 3D printing to spinal orthosis for AIS. Hence, the primary objective of this prospective randomized controlled trial (RCT) study is to investigate if the 3O is as effective as CO in the management of patients with AIS. The secondary objective is to study the patient's compliance and quality of life (QoL).