Prediction of vertebral failure under general loadings of compression, flexion, extension, and side-bending

Bone pathologies such as osteoporosis and metastasis can significantly compromise the load-bearing capacity of the spinal column, increasing the risk of vertebral fractures, some of which may occur during routine physical activities. Currently, there is no clinical tool that accurately assesses the risk of vertebral fractures associated with these activities in osteoporotic and metastatic spines. In this paper, we develop and validate a quantitative computed tomography-based finite element analysis (QCT/FEA) method to predict vertebral fractures under general load conditions that simulate flexion, extension, and side-bending movements, reflecting the body's activities under various scenarios. Initially, QCT/FEA models of cadaveric spine cohorts were developed. The accuracy and verification of the methodology involved comparing the fracture force outcomes to those experimentally observed and measured under pure compression loading scenarios. The findings revealed a strong correlation between experimentally measured failure loads and those estimated computationally (R² = 0.96, p < 0.001). For the selected vertebral specimens, we examined the effects of four distinct boundary conditions that replicate flexion, extension, left side-bending, and right side-bending loads. The results showed that spine bending load conditions led to over a 62% reduction in failure force outcomes compared to pure compression loading conditions (p ≤ 0.0143). The study also demonstrated asymmetrical strain distribution patterns when the loading condition shifted from pure compression to spine bending, resulting in larger strain values on one side of the bone and consequently reducing the failure load. The results of this study suggest that QCT/FEA can be effectively used to analyze various boundary conditions resembling real-world physical activities, providing a valuable tool for assessing vertebral fracture risks.