Effects of Strap Options on Scoliosis Bracing Mechanics: An Application of the Scoliosis Analog Model

Abstract

Summary form only given. Thoracolumbar braces are commonly used to treat Adolescent Idiopathic Scoliosis (AIS). Braces serve to reduce and prevent progression of the spinal curve by applying corrective forces, which are affected by alterations made during the brace fitting process. The Scoliosis Analog Model (SAM), a mechanical equivalent of the AIS condition capable of simulating up to 40 degrees of spinal correction, enables analysis of corrective forces applied by the brace to the spine and structural properties of the brace. This model was used to investigate the effects of strap-related brace alterations. A Boston brace was tested using the SAM and biorobotic testing platform. Various configurations of Velcro and buckle straps used to fasten the brace were tested and compared to unconstrained and rigidly-constrained configurations. Measurements of the force components applied to the model and SAM angular displacement were used to calculate brace structural stiffness properties. Addition of either strap type significantly increased the stiffness values relative to the unconstrained brace configuration. An optimal brace radial stiffness was achieved with three Velcro straps, i.e., there was no significant stiffness gained by adding a fourth strap. For the case of the buckle straps, no significant stiffness gain occurred when more buckle straps were added. Structural properties provide a means to compare bracing technology and better understand design alterations. A measurable difference exists in brace force response and structural properties between each configuration. Interpretation of the measured force components revealed that the brace applied inward and upward forces to the spine.