Influence of the magnitude and orientation of forces on the odontoid fracture: A finite element model analyses.

Background: Fractures of the odontoid, prevalent among the elderly but affecting diverse demographics, pose significant risks ranging from mild discomfort to severe disability or fatality. These fractures, often stemming from trauma, are particularly frequent in the cervical spine. While commonly attributed to high-impact events like traffic accidents in adults, even low-energy incidents such as falls can precipitate these fractures in the elderly. Previous studies have explored loading conditions and treatment effects; however, a comprehensive investigation into the influence of the magnitude and direction of the force involved in the trauma, and the influence of the sex and age of the patient remains scarce so we want to delve deeper into this topic.

Methods: This study uses a finite element (FE) model to analyze the response of 3D models of the second cervical vertebra (extracted from computed tomography images) exposed to different loads of magnitude and force. 52 patients were analyzed in this study. The patients were divided into 4 groups: male <70, female <70, male >70, female >70) under different force conditions. Von Mises stress values were obtained when loads of 200 N and 1500 N were applied to the anterior surface of the odontoid with different angles of incidence in the sagittal and axial plane.

Results: Odontoid fractures in subjects over 70 years of age are more frequent in female, the maximum stresses produced in the odontoid are 181 MPa and are considerably higher compared to male, which is 131 MPa. In young subjects (<70 years), the differences between sex are less marked, 113 MPa for female and 114 MPa for male.

Conclusions: Load direction is one of the main factors affecting odontoid fracture, especially in subjects >70 years of age; by understanding this, the mechanisms that cause different types of fractures can be understood and better strategies can be proposed to apply different treatment approaches to them, both from a medical and surgical point of view.