Foramen Magnum Orientation and Its Association with Cervical Lordosis: A Model for Reconstructing Cervical Curvature in Archeological and Extinct Hominin Specimens

Abstract

The cranial base is located at a critical intersection between the vertebral spine, the brain, the respiratory system and the mastication apparatus. Therefore it can provide an insight into the evolution of the head and neck in functional and phylogenetic contexts. However, the relationship between cranial base anatomy and cervical spine alignment has not been explored deeply. Therefore the aim of this research is to study the relationship between the orientation of the foramen magnum and the degree of cervical lordosis. Based on this relationship we developed six models which enable reconstruction of the cervical lordosis angle in archeological material and in extinct hominins. 74 adult lateral cervical radiographs were examined. The orientation of the foramen magnum and the angle of the cervical lordosis were measured on each radiograph. Foramen magnum orientation positively correlates with cervical lordosis angles: moderate to high correlation was found between foramen magnum orientation and the total cervical lordosis (0.716 < r < 0.612); moderate correlation was also found between foramen magnum orientation and the upper cervical lordosis (0.626 < r < 0.562); and only weak correlation was found with the lower cervical lordosis (0.306 < r < 0.101). Assuming that the positive correlation between foramen magnum orientation and cervical lordosis can be applied to all bipedal hominins, cranial base morphology can provide an insight to the degree of the cervical lordosis of archeological material and of extinct hominin.