Scoliosis Brace Finite Element Model and Preliminary Experimental Testing Using Electronic Speckle Pattern Interferometry

Abstract

This article presents the results of numerical finite element method (FEM) simulations in the Ansys environment of a Boston orthopaedic brace. The geometric model was developed based on the results of digitisation performed by means of a three-dimensional (3D) optical scanner. A test stand for measurement of the brace’s field of displacements, utilising a laser electronic speckle pattern interferometer (ESPI), was used to experimentally verify the FEM model. During experimental testing, special attention was given to applying the loads and boundary conditions used in the numerical simulations. As a result, the relative difference between the experimentally and numerically determined displacements in the central part of orthoses amounted to approximately 0.6%. The experimentally verified FEM model was used to determine the force flow lines characteristic of the brace, indicating the general working method of the brace’s structure. The primary parts of the orthoses, carrying loads correcting the spine and the position of sites exerting little effort from the perspective of their participation in the orthoses’ essential therapeutic application were identified. The results obtained allow for the proposal of methods for mechanical optimisation of the brace’s design. The analysis conducted is universal in nature and can be adapted to other types of orthopaedic braces.

Keywords

• FEM
• ESPI
• out-of-plane displacement
• orthoses
• principal stress trajectories
• principal stress vector