Analysis of the material properties and microstructure of degenerated spinal bone tissue

Project’s context 

The Canadian public health agency estimates that 10% of the population over 40 has osteoporosis. Osteoporosis causes many changes in the human body, including the development of osteophytes, which are bone spurs that develop between joints. According to previous studies conducted at the international iLab Spine laboratory, osteophytes may have an impact on traumatic spinal injuries. In fact, older people are more vulnerable to spinal fractures in low-energy accidents such as falls. However, the process of spinal osteophytes development, their mechanical behavior, and their role in spinal injuries are misknown. Numerical simulation could help to understand the injury mechanisms of the spine in older people. However, the lack of data in the literature on the composition and properties of spinal osteophytes prevents a biofidelic modeling of degenerated vertebral columns.

A preliminary study of the macroscopic morphology of spinal osteophytes and preliminary compression tests of osteophyte samples have been carried out. First micro-tomodensitometry images have been obtained and showed that osteophytes have a non-uniform structure. We hypothesize that this structure is variable depending on the level of degeneration and the individual. Osteophytes are therefore complex structures and it is necessary to understand their microstructure and composition in order to correctly characterize their biomechanical behavior.
This project aims to link the level of degeneration of the vertebral column to the microstructure and material properties of osteophytes. This characterization of osteophytic tissue will help to better understand the traumatic behavior of degenerated bone tissue.

PhD’s description 

This project can be divided into four parts: 
1)    Characterization of the osteophytes’ material properties using compression test and nano-indentation
2)    Analysis of the osteophytes’ composition by histology
3)    Characterization of the osteophytes’ microstructure by micro-tomodensitometry
4)    Numerical modeling of spinal osteophytes to understand the relationship between their microstructure and mechanical behavior

The student will develop an experimental protocol to isolate samples of spinal osteophyte from human in vitro specimens and to perform compression and nano-indentation tests. These tests will serve to identify the macroscopic and microscopic mechanical properties of the samples. Trabecular and cortical vertebral bone samples will also be collected to compare the material properties of the osteophytes with the rest of the vertebra. Histological sections (hematoxylin and eosin staining) will be produced and analyzed to identify the nature of the tissues present (bone, cartilage, fibrous tissue, etc.) and to investigate the process of osteophyte formation. The samples will also be imaged by micro-tomodensitometry to evaluate various microstructural properties: porosity, bone thickness, and sample anisotropy, among others. Finally, a numerical model of spinal osteophytes will be developed. The compression tests will be numerically replicated to propose a mechanical behavior law and to investigate the influence of the microstructure and tissue composition of the osteophyte on the mechanical behavior.

The phD candidate will have the opportunity to collaborate with other students working on the numerical modeling of the aging spine and on head and spine trauma within the Imaging and Orthopedics Laboratory (LIO). The research project will take place in Montreal at the Imaging and Orthopedics Laboratory of the Sacré-Cœur Hospital in Montreal.