Computed tomography, histological and ultrasonic measurements of adolescent scoliotic rib hump geometrical and material properties

In Adolescent Idiopathic Scoliosis (AIS), numerical models can enhance orthopaedic or surgical treatments and provide reliable insights into the mechanism of progression. Computational methods require knowledge of relevant parameters, such as the specific geometrical or material properties of the AIS rib, about which there is currently a lack of information. The aim of our study was to determine the geometrical and material properties (Young's modulus [E] and Poisson's ratio [ν]) for AIS rib bones. Twelve ribs extracted during gibbectomy on 15 and 17 year old girls were tested using computed tomography (CT) scanner, histology and ultrasonic scanner. The mean porosity (± standard deviation (SD)) is 1.35 (±0.52)% and the mean (±SD) bone mineral density is 2188 (±19) mmHA/cc. The cortical part of the AIS rib hump is found to be thicker than physiological values in the literature. To mimic the rib hump for an AIS girl, our results suggest that ribs should be modeled as hollow circular cylinders with a 10.40 (±1.02) mm external radius and 7.56 mm (±0.75) internal radius, and material properties with a mean E of 14.9 GPa (±2.6) and a mean ν of 0.26 (±0.08).