A team of researchers set out a to develop a 3D-printed brace protocol for juvenile idiopathic scoliosis with respect to its design, biomechanical properties, procedures, and brace adjustment and fitting; they found a method that provided better fit and function of the device.
For initial testing, the patient stood still and was positioned with manipulation techniques directed by the physician, with the help of a torso measurement frame. A hand-held scanner registered the 3D torso, and then the brace was designed using a computer-aided design model.
The researchers used finite element analysis to determine the minimum required thickness of the brace. Acrylonitrile butadiene styrene (ABS) material (thermoplastic polymers) and DuraForm PA plastic (nylon) material were used to 3D print devices by two different systems and were tested using standard tensile test procedures.
From the data, the researchers concluded that the minimum thickness of the brace should be 2mm 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 percent versus 14 percent), and the tensile strength was reduced more for ABS as compared to nylon (42 percent versus 14 percent).
According to the study’s authors, 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, which improved ease of adjustments in trimming, drilling, and heat modifications for better fit and function.
The study, “Development of 3D-printed braces protocol for juvenile idiopathic scoliosis: From the torso measurement and mechanical properties to preliminary experience on fitting,” was published in Prosthetics and Orthotics International.
