A Finite Element Approach to Brace Treatment for the Scoliotic Spine

Scoliosis is a three-dimensional deformity of the spine most prevalent in adolescent females. As the etiology is often unknown, treatment focusses on preventing curve progression and ranges from observation for mild cases to brace treatment and eventually surgery for the worst cases. This report consists of three different studies, which are aimed to develop a patient specific method to improve the efficacy of brace treatment for scoliosis patients. The first study consists of a literature review of applications of the Finite Element Method (FEM) in scoliosis research, with a focus on brace treatment. It is concluded that the finite element method has great potential to improve both surgical and brace treatment. However, it has only been applied in a few commercially available braces. Current methods are still quite inaccurate, and thus recommendations are made to improve the quality of FEM models. The second study aims to establish the forces experienced by spinal implant rods during intra-operative scoliosis correction, in order to validate and improve an existing FEM model of the scoliotic spine. The forces that were found were inconclusive, due to various measurement uncertainties. Therefore, validation of the FEM model based on this data was not possible. However, recommendations were made to improve the study, such that conclusive results should be found. In the final study a patient-specific FEM model of the scoliotic spine is developed and simulated to establish the location, magnitude and direction of force application for optimal curve correction. By varying the angle of the thoracic force vector over a 180° range in the transverse plane, the curve correction was established for these angles for four patients. The influence of the lumbar force on curve correction was found to be minimal. An optimization algorithm was subsequently employed to more establish the optimal force direction. The algorithm allowed more variables to be evaluated on a smaller scale, while maintaining a low computational cost. From the three studies it is concluded that FEM models of the spine can be a valuable addition to scoliosis studies. However, spinal behaviour is complex, and many elements such as material properties and interpersonal variation in stiffness remain unknown.

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Master Thesis - Ruurd Kuiper.pdf

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