The second cervical vertebra (known as the "axis")
has a bony protrusion in the front (known as "odontoid process"),
which is raised until it forms a joint with the first cervical vertebra
( or "atlas").
The atlantoaxial dislocation is a fracture of the
odontoid process, in such a way that the end which forms a joint
with the atlas is separated from its base and kept in position only
by the ligaments, which are not strong, joining it to the atlas.
As a result, an atlantoaxial dislocation is not really a form
of common back pain, as it is due to a bone fracture caused
by direct trauma.
How it happens
An atlantoaxial dislocation is a result of significant
trauma, and is most frequently caused by traffic accidents.
Pain in the cervical area, sometimes with pain
in the back of the neck or painful restriction of mobility.
Given that one end of the odontoid process is left
free and is only joined by several ligaments which are not very
strong, it may become displaced and thus compress the spinal cord.
The compression of the spinal cord in this first cervical segment
may produce severe neurological injuries or even death.
Hence, it is essential to avoid the possibility
In cases of atlantoaxial dislocation, medical
history and physical
examination provide very vague information and are not sufficient
to arrive at a diagnosis. If the existence of an odontoid fracture
and an atlantoaxial dislocation are suspected, physical examination
must be performed with great care to avoid movement of the neck.
might be the method of choice, since it allows observation of the
odontoid fracture, usually with a radiography performed with the
If the fracture is very recent, it may not be revealed by radiography
and may require a bone
gammagraphy. Radiographical images which appear suspicious but
not conclusive may require a Computerized
Axial Tomography (CT Scan ) in order to confirm the diagnosis.
Given that this is a fracture with a risk of displacement,
it requires immobilization and, in light of the risk of possible
displacement, its progress should be closely monitored.
may be given for the pain. Vertebral manipulation is absolutely