Logo image
Back
Parametric simulation study of generalized brace-like corrective forces using an AIS patient-specific FE template model of the spine, rib cage, pelvis, torso external soft tissue, and abdomen
Thesis

Parametric simulation study of generalized brace-like corrective forces using an AIS patient-specific FE template model of the spine, rib cage, pelvis, torso external soft tissue, and abdomen

Adrian-Christophe Vogler Bullard
Master of Science (M.S.), Drexel University
Jun 2026
DOI:
https://doi.org/10.17918/00011469
pdf
Bullard_Adrian-Christophe_20264.57 MB
PDF Embargoed Access, Embargo ends: 30 Jun 2028

Abstract

Adolescent idiopathic scoliosis Corrective force simulation Intervertebral disc stress Patient-specific modeling Scoliosis bracing Finite Element Analysis
Adolescent idiopathic scoliosis (AIS) is a three-dimensional spinal deformity that can progress during skeletal growth due to asymmetric mechanical loading of the spine. Non-surgical bracing is commonly used to limit curve progression in skeletally immature patients, but treatment success depends on both the magnitude of immediate in-brace correction and patient compliance over the prescribed wear period. Rigid braces can generate corrective forces but may reduce comfort and compliance, while soft-bracing concepts may improve tolerability but require further biomechanical evaluation. Patient-specific finite element (FE) modeling provides a computational approach for quantifying how external forces are transferred through the osteoligamentous thoracic and lumbar spine, rib cage, and pelvis with the torso's external soft tissue (TEST) and abdomen. However, many existing AIS patient-specific FE models simplify the external torso using shell elements or do not include a representative torso external soft tissue and abdominal components. Therefore, the objective of this thesis was to develop an AIS patient-specific FE modeling framework capable of quantifying effects on spinal curve correction and apical intervertebral disc (IVD) stress from generalized brace-like corrective forces in a parametric simulation study. In Specific Aim 1, an AIS patient-specific FE template model was developed by morphing a normative pediatric osteoligamentous thoracic and lumbar spine-rib cage-pelvis FE model to an AIS patient-specific spinal and rib cage geometry and integrating a solid hexahedral torso external soft tissue (TEST) FE model and a simplified solid hexahedral abdominal FE component using connector beams to transmit corrective forces from the external surface of the torso to the osteoligamentous thoracic and lumbar spine-rib cage-pelvis FE model. A mesh convergence study as well as various quality assessments supported the selected element sizes, and frontal-plane geometric comparison showed less than 5% error for the evaluated anatomical dimensions. In Specific Aim 2, the AIS patient-specific FE template model was used in a parametric simulation study to evaluate generalized three-point brace-like corrective forces applied to the axillary, apical, and lumbar regions on the external surface of the TEST FE model. Corrective force magnitude, force-vector angle, and apical force location were varied using apical forces of 40 N, 60 N, and 80 N, force-vector angles of 10°, 25°, and 40° with respect to the transverse plane (XY-plane), and lateral, posterolateral, and anterolateral apical force locations. The simulations demonstrated that increasing force magnitude generally reduced Cobb angle, increased apical vertebral (T9) axial orientation, decreased average von Mises stress on the concave half of the T9-T10 IVD, and increased stress on the convex half of the T9-T10 IVD. Increasing the force-vector angle reduced Cobb angle and concave-side T9-T10 IVD stress, but was also associated with decreased T9 axial orientation. Among the apical force locations, posterolateral and lateral loading were more effective than anterolateral loading for Cobb angle correction and for producing lower concave-side T9-T10 IVD stress relative to the convex side, while anterolateral loading produced the greatest change in T9 axial orientation. The clinical significance of this work is that it provides a patient-specific computational framework for evaluating how corrective force magnitude, direction, apical force location, and interface stress influence immediate spinal correction, internal disc loading, and patient compliance. By quantifying changes from the baseline model state, this approach may help identify loading combinations that maximize initial in-brace correction while limiting undesirable stress distributions on the vertebrae and IVD. Although long-term growth modulation was not directly simulated, the T9-T10 IVD stress response provides a mechanical indicator of how brace-like loading may redistribute apical stresses in a manner relevant to growth modulation principles, such as the Hueter-Volkman law. More broadly, this framework can be adapted to investigate additional brace concepts, loading configurations, curve classifications, and spinal deformities beyond AIS. With appropriate patient-specific geometry, material properties, and loading definitions, the model provides a foundation for future computational studies of non-surgical spinal correction, load transfer, and patient-specific brace optimization.

Metrics

1 Record Views

Details

Logo image