Finite element modeling and experimental validation of wedge fractures in the thoracic spine

Vertebral compression fractures (VCFs) are the most common fractures in patients with osteoporosis, contributing to approximately 700,000 spinal fractures annually. Wedge fractures, characterized by anterior vertebral body collapse, are the most prevalent type of VCFs and a significant cause of spinal deformity, such as thoracic kyphosis. This study aimed to develop and validate a finite element model (FEM) of wedge fractures to understand their biomechanics and clinical implications, and help future studies to elucidate spine fractures in osteoporotic patients.

CT-based finite element models of T9-T12 vertebral bodies were developed using scans from four cadaveric spines. Axial compression tests were performed on the corresponding vertebrae using a Materials Test Systems (MTS) machine to induce wedge fractures. Key biomechanical parameters, including stiffness and strength, were measured and compared to FEM predictions for validation.

The FEM demonstrated strong agreement with the experimental data, achieving coefficients of determination (R²) of 0.71 (p < 0.01) for stiffness and 0.88 (p < 0.01) for strength. The FEM predicted a stiffness of 5.9 ± 0.6 kN/mm and a strength of 3.2 ± 0.4 kN, which closely matched the experimental values of 5.83 ± 1.2 kN/mm and 3.54 ± 0.6 kN, respectively. The FEM also qualitatively reproduced fracture patterns, including mid-fracture lines and delamination of the anterior cortical shell.

This study validates FEM as a robust tool for modeling wedge fractures and understanding their role in spinal deformity. The model offers insight into vertebral compression fractures and can be further developed for use in other clinical applications, to provide the volume needed to restore the height of the vertebrae.