The axis (from the Latin axis, “axle, axis”) is the second cervical vertebral, it participates in the mobility of the head.

Behind the neck, the nape is made up of seven cervical vertebrae, numbered C1 to C7. They provide strength and mobility to the neck. The axis is the second cervical vertebra (C2), it presents a morphology different from the other vertebrae which gives it an important role in the mobility of the neck.

It has a voluminous vertical process on its upper surface, the tooth of the axis or odontoid process. This process articulates at the top with the first cervical vertebra, the atlas (C1), which maintains it by its transverse ligament. It is also linked by its apical ligament to the occipital bone of the head. The upper articular surfaces of the axis receive the lower articular surfaces of the atlas; this joint allows you to turn your head.

On each side, the transverse process of the axis is pierced with its transverse foramen, which leaves the passage to a vertebral artery.

The axis has an important role in the mobility of the neck. Its odontoid process plays a pivotal role which allows the rotation of the atlas, and therefore of the head.

The articulation between C1 and C2 allows rotation of the head 90 ° C to the right and to the left. The axis also participates, but to a limited extent, in the lateral tilting movements of the head.

The fracture of the axis most often affects the odontoid process, up to 60%. The most frequent cervical trauma (7 to 14%), it generally occurs either in young subjects during multiple trauma, or in elderly subjects during a fall. The mechanism of the trauma is mainly a hyperextension movement. The fracture line can affect the odontoid process at different levels: tip, neck and base of the odontoid. Depending on the case, the fracture is treated by immobilization using a plaster neck brace or by surgical intervention (lacing C1 and C2 for immobilization of the odontoid, screwing or strapping). More rarely, the fracture affects the body of the axis.

X-ray : medical imaging technique that uses X-rays. The lateral and open-mouth radiography makes it possible to detect the site of the fracture and to see if a dislocation of the atlas is added to the trauma.

Scanner : diagnostic imaging technique which consists of “scanning” a given region of the body in order to create cross-sectional images, thanks to the use of an X-ray beam. The term “scanner” is actually the name of the medical device, but it is commonly used to refer to the exam. We also speak of computed tomography or computed tomography. In the case of an odontoid fracture, the scanner makes it possible to visualize the bone anatomy of the invoice (type of fracture, precision of the extension of the fracture line, etc.).

MRI (magnetic resonance imaging) : medical examination for diagnostic purposes carried out using a large cylindrical device in which a magnetic field and radio waves are produced. Where radiography does not allow it, it reproduces very precise images. In the case of fractures, it is used in particular to check the integrity of the transverse ligament or damage to nerve structures.