Computer-aided design & 3D printing of adolescent idiopathic scoliosis brace

• Main Author: Yeo, Guoli
• Other Authors: Chou Siaw Meng
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2022
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/159072
• Institution: Nanyang Technological University

Adolescent idiopathic scoliosis (AIS) is a three-dimensional curvature of the spine. It is the most common form of scoliosis, affecting children aged 10 to 18. Scoliosis can be categorized into three groups – idiopathic, congenital, and neuromuscular. To prevent surgery, bracing is conducted to prevent the curves from progressing. The traditional method uses plaster-casting to manufacture the brace. However, this method requires more time and labour than the recent method, computer-aided design and computer-aided manufacturing (CAD/CAM). With technological advancements, 3D printing is gaining prominence for orthosis. Thus, the objective of this project is to analyse the behaviour of the 3D scoliosis brace model with Finite Element Analysis (FEA). The scope of the study included the analysis of opening of brace, as well as the study of brace behaviours through the inclusion of torso pressure and tightening of brace through the usage of tightening straps. The torso pressure includes the body contact pressure exerted upon the protruding areas of the brace. The strap’s tension force after the tightening of the brace were also analysed in this study. FEA was used to analyse the behaviour of the brace using ANSYS. The material properties for the main material of study, PA2200 (Polyamide/Nylon 12), were inputted into the software before further analysis was made and mesh convergence was carried out to improve the accuracy of results. Displacements were applied to the brace to mimic patients opening the brace. Results showed that plastic deformation would occur with 37.5 mm displacement. Later, strap tensions were applied through displacement of strap holes to simulate the tightening of brace, and human torso pressure was applied through the inclusion of contact pressure between the human body and the protruding areas of the brace, with the region with the highest pressure at 10.2 MPa and region with lowest pressure at 8.0 MPa. The analysis resulted with a maximum stress of 12.827 MPa with no exceeding values beyond the material’s yield strength. The simulations showed that the force required to tighten the brace whilst stacking onto the effects of torso pressure on the brace were measured and taken at 106.66 N for the left strap holes, and 51.861 N for the right strap holes. The brace requires further research to effectively simulate the body pressure acting on the brace model with the breathing motion of a human body, ensuring there are sufficient pores for ventilation, and to determine the fatigue life of the brace.