Tortuosity influence on the trabecular bone elasticity and mechanical competence

Abstract

Osteoporosis is a disease characterized by a remarkable bone mass loss and trabecular bone degradation, which leads to an increase in bone fragility and a higher fracture risk. There are strong evidences that the trabecular microarchitecture degradation impacts the fracture risk. The trabecular bone structure resembles a network composed of tortuous struts and their tortuosity influences the structural stiffness. This work investigates how the trabecular volume fraction, network connectivity, trabecular tortuosity andYoung modulus of elasticity can be aggregated in a unique variable to provide information about the trabecular bone fragility. The parameters are estimated for three cohorts, two from ex vivo microtomographic (μCT) images and the other one from in vivo magnetic resonance imaging (MRI); the μCT image samples are from distal radius and vertebrae, while the MRI samples are also from distal radius. The principal component analysis shows that the principal component, defined as mechanical competence parameter (MCP), can be used to grade the quality of the samples and a visual color spectrum is generated to provide a quality distribution of the samples. The results point out a prevalent direction of the tortuosity along the z direction in all cohorts, which correspond to the most frequent direction of stress and high values of MCP indicating better structured samples. In addition, a remarkable result is the strong correlation between the tortuosity in both x and y horizontal directions and the elasticity in the z vertical direction, evidencing the role that the horizontal trabecular connectivity plays to the mechanical competence of the trabecular bone structure.