# Persistence of the midline septum of the odontoid process: anatomical and radiological study

## TL;DR

This study found that a bony septum in the odontoid process persists in about 22.6% of cases, which could affect surgical and biomechanical considerations.

## Contribution

This is the first study to investigate the persistence of the midline septum of the odontoid process and report its prevalence.

## Key findings

- The overall prevalence of the midline septum was 22.6% (7 out of 31 samples).
- Midline septa were consistently located within the anterior two-thirds in axial and superior two-thirds in coronal views.
- The shape of the midline septum varied among samples.

## Abstract

During our screening of the computed tomography (CT) images of the craniocervical junction, we noticed that the odontoid process occasionally contains a highly ossified region in the midline consistent with a bony septum. Given its potential significance, this study aimed to investigate the highly ossified region in the midline of the odontoid process and to discuss its clinical relevance.

Eleven C2 vertebrae from formalin-embalmed cadaveric heads were assigned to micro-CT examination. When the midline septum was confirmed, gross anatomical and histological observations were performed. Another 20 dry adult C2 vertebrae were randomly chosen, and the midline septum was investigated using gross anatomical and histological observations.

Overall prevalence of the midline septum was 22.6% (7/31) (36.7% with cadaveric C2 using micro-CT and 15% in dry C2). The midline septa were found within the anterior two-thirds in the axial view and superior two-thirds in the coronal view. The midline septum in each sample varied in its shape.

To our knowledge, this is the first study of the persistence of the midline septum of the odontoid process. We found the overall prevalence of this septum was 22.6%. All of the midline septa were found within the anterior two-thirds in the axial view and superior two-thirds in the coronal view. Future clinical studies are necessary to further explore its potential biomechanical and surgical significance, particularly in influencing odontoid fracture patterns.