Development of 3D-printed braces protocol for juvenile idiopathic scoliosis: From the torso measurement and mechanical properties to preliminary experience on fitting.

BACKGROUND

There has been no standard for a rapid prototyping process in manufacturing of the 3D-printed brace with respect to its design, biomechanical properties, procedures, and brace adjustment and fitting.

Objective

Objective of this study was to develop the 3D-printed brace protocol for juvenile idiopathic scoliosis.

METHODS

With the help of the Torso Measurement Frame, the child stands still and is positioned with 1 of 2 manipulation techniques by the physician. Although the patient is in the corrected position, a hand-held scanner registers the three-dimentional (3D) torso, and then the brace is designed using computer aided design (CAD) model. Finite element analysis is used to determine the minimum required thickness of the brace. Acrylonitrile Butadiene Styrene (ABS) material (thermoplastic polymers) and DuraForm PA plastic (Nylon) material were printed by 2 different systems, respectively, and were tested using standard tensile test procedures.

RESULTS

The minimum thickness of the brace should be 2 mm to maintain a standard structural factor of safety twice that of the material failure strength. The strain in elongation was less for the ABS compared to the 3D-printed Nylon (6% vs. 14%), and the tensile strength was reduced more for ABS as compared to Nylon (42% vs. 14%). The ABS brace could not withstand changes in tension and cracked when drilled into, heat flared, or donned tightly. However, the Nylon brace improved strength and eliminated the vulnerable aspects.

CONCLUSIONS

The Nylon material for the 3D-printed brace improved ease of adjustments in trimming, drilling, and heat modifications for better fit and function.