Characterizing Torso Stiffness in Female Adolescents With and Without Scoliosis

Abstract

Adolescent Idiopathic Scoliosis (AIS) is a spinal curvature that affects 3% of the population and disproportionately affects females. It is treated with bracing and many researchers are developing models of the torso to optimize the effectiveness of brace designs. Unfortunately, the data available to create these models is limited by the experimental methods employed. One method, in vitro spine cadaver stiffness measurements, is generally based on specimens from the elderly, which are not representative of the adolescent population. The other method, radiographic studies, can only provide a limited amount of information because of the radiation exposure that multiple images require. In this work, we present a Robotic Spine Exoskeleton (RoSE) tailored to the population in greatest need of AIS interventions-female adolescents. We use it to create a three-dimensional stiffness characterization of the torso in vivo for eight female adolescents with scoliosis and eight without this condition. The key findings include an interaction effect of DOF and torso segment on translational collinear stiffnesses, and an interaction effect of DOF and group on rotational collinear stiffnesses. We also found that the 3D coupling stiffness pattern is in line with that of the human spine, regardless of spinal deformity. Also, the magnitude of the torso stiffness for the tested population is less than that of the adult male population previously characterized. Our results provide quantitative data for torso stiffness and can be used to improve brace designs. Our methods could also be adapted as a way to customize subject-specific treatment methods, as there is a lot of variation among subjects.