A Novel 3D Printed Brace Manufacturing Process for the Treatment of Adolescent Idiopathic Scoliosis

• Author / Creator

  Ng, Kenwick

• Adolescent Idiopathic Scoliosis (AIS) is a three-dimensional spinal deformity with lateral curvature and axial vertebral rotation affecting 1-3% of adolescents. Bracing is a proven non-surgical treatment aiming to stop curve progression. Literature has shown that brace wear time affects brace effectiveness. However, the current structure of a brace can be bulky, lack ventilation, and cumbersome to manufacture which affects patients’ compliance. The motivation of this research is that a more comfortable, and effective brace can be manufactured with 3D printing and scanning technologies at reduced cost and labour effort. The objectives of this research are to investigate appropriate 3D printing parameters, to design and evaluate dynamic brace pads and brace casting frame, to investigate the 3D scanned torso accuracy and precision, to design a new brace manufacturing process and to evaluate the 3D printed brace effectiveness and manufacturing process.To determine the appropriate parameters for printing a brace, experiments were conducted to compare the mechanical properties of 31 test specimens that were 2.5 mm, 3.25 mm, and 4 mm thick with ULTEM1010, Nylon12, and polypropylene material. Fused deposition modelling (FDM) method, Nylon12 material, and 2.5-3.25 mm thickness were found to be the appropriate printing parameters with high flexibility, as well as adequate strength and ductility. To validate durability of a brace with the recommended printing parameters, manual simulation of prototype brace wear with donning and doffing was conducted. The FDM, Nylon12, 2.5 mm thick, and upright printed prototype brace showed retention of structural integrity with 2 years brace wear simulation. To understand the pressures applied by orthotists to obtain the satisfactory simulated in-brace body contour, airtight dynamic brace pads were designed. The dynamic brace pads were integrated with a brace casting frame so that 3D corrective forces could be applied to patients’ torso during brace design clinic. The completed system was evaluated with a healthy volunteer to ensure both the dynamic brace pads and the brace casting frame met design specifications before using it at the clinic.Patient’s torso was captured while standing in the casting frame. As a specific 3D scanner was chosen, its accuracy and precision in capturing torso contour were investigated prior to application in clinics. Experiments were conducted by scanning different body mold dimensions at different scan ranges. Furthermore, the 3D reconstruction accuracy at pad covered torso regions were evaluated based on deviation between scan without pads applied and scan with reconstructed pad regions. The results showed that the scanned torso accuracy and precision were within 1 cm clinical accepted range, but the reconstruction accuracy slightly exceeded 1 cm. A subjective modification on the pad covered regions might be needed by the orthotist. To construct a 3D printed spinal brace based on the results described above, a new 3D printed brace manufacturing process was developed. This process began with the orthotist adjusting the brace frame pad placement and applied pressure on patient torso to obtain satisfactory in-brace pad configuration based on real-time ultrasound and pressure measurements. Patient’s torso was then scanned, modified and sent for 3D printing. Lastly, to investigate the 3D printed brace effectiveness, a randomized controlled trial (RCT) was conducted to compare the immediate in-brace corrections at the first follow-up clinic of patients with the traditional and 3D printed brace. Currently, four patients were recruited with two patients at each study arm. For the 3D printed brace group, the in-brace Cobb angle correction of 3/4 treated curves reached clinical aimed threshold of 50% correction. The 3D printed brace was also 30% thinner, 26% lighter, and requiring 4.5 times less labour time than the traditional brace. However, it is 27% more expensive in cost because the 3D printed brace was printed from external source while the traditional brace was built in-house. In conclusion, this thesis reports a new design of dynamic brace pads which were implemented into a novel 3D printed brace manufacturing process to create thinner, lighter, lower labor cost and at least similar in-brace effectiveness 3D printed braces for the future generation of brace treatment for children with AIS.

• Subjects / Keywords

  • 3D scan
  • 3D print
  • CAD/CAM
  • Randomized contolled trial
  • Mechanical properties
  • Dynamic brace pad
  • Brace manufacturing process
  • Brace casting frame
  • Scoliosis
  • Brace

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-9edw-8b18

• License

  Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.