Last Updated on October 20, 2023
An open mouth view x-ray is a special view to visualize upper cervical spine problems and is especially useful to assess C1 and C2 vertebrae integrity in acute injuries. It provides anteroposterior visualization of these vertebrae.
Open mouth x-ray is necessitated in cases one wants to visualize C1 and C2 as the routine anteroposterior cervical spine view shows the spine from C3 segment and is usually less helpful in diagnosing acute injuries.
Open mouth view x-ray is not done routinely and is ordered when a problem is suspected in the upper cervical spine.
Relevant Anatomy
The upper cervical spine is formed by the atlas (C1), the axis (C2), and adjoining structures. The first cervical vertebra is called the atlas. It articulates with the skull base above and the second vertebra of the cervical spine or axis below.
Image Courtesy: Musculoskeletal Key
Here is what C1 looks like.
[Read more about C1 vertebra or atlas]
Following is a diagrammatic representation of C2 vertebra.
[Read about details of axis vertebra]
Indications of Open Mouth View Xray
The open-mouth view is essential for excluding a C1 arch or odontoid process fracture. The odontoid process is part of the second cervical vertebra that projects upward to articulate with the C1 vertebra.
The open-mouth view x-ray is also called the Odontoid view or odontoid peg view.
It is a very useful view in traumatic injuries of the upper cervical spine and whiplash injury of the cervical spine.
The various cervical injuries where this x-ray can be used are
- Dens Fracture or C2 odontoid Fracture
- Jefferson’s Fracture or C1 burst Fracture
- Transverse Ligament Injury
- Basilar Invagination
Apart from injuries, infection, and other diseases that affect C1, C2 are the indications of getting this x-ray done.
How is Open Mouth View X-ray Done?
The position is the same as for an anteroposterior view. The patient lies in a supine position i.e. on his back and has to open her mouth widely. The x-ray beam is projected through the open mouth from the anterior to posterior direction.
The shoulders should be at equal distances from the image receptor. This will avoid rotation.
The patient is instructed to open their mouth.
The head is so positioned as to keep lower margin of the upper incisors and the base of the skull perpendicular to the image receptor.
For non-trauma patients, the erect position can be used for taking the view.
It is important that the patient opens the mouth as widely as possible to visualize the structures properly. If the patient does not open her mouth widely, the structures we intend to see may get obscured by jawbones and teeth.
What is Looked For in Open Mouth View X-ray?
- Anatomy of C1-C2 vertebrae
- Dens or Odontoid process
- Lateral masses of C1 vertebra
- Malalignment or fracture of the vertebra
It must be noted that the open-mouth x-ray is evaluated in conjunction with other projections of the cervical spine namely anteroposterior and lateral views.
How Does Normal Open Mouth View X-ray Look Like
Here is an example of an open mouth view x-ray showing C2 and C1 anatomy which includes C2 vertebra, odontoid process, the joint between C1 and C2 and facets.
For interpretation, the x-ray is read as follows.
For the x-ray to be normal’
- The lateral masses of C1 in symmetrical alignment with the lateral masses of C2
- No asymmetry of the articular spaces between the dens and the lateral masses of C1
- No asymmetry of the articular spaces between the lateral masses of C1 and the body of C2
Any asymmetry in the context of spinal injury should raise the suspicion of dens fracture, Jefferson fracture, or transverse ligament injury and be further evaluated accordingly.
Final Note
This x-ray requires a patient who is conscious and can cooperate. This may not occur in stressful and painful situations. Moreover, a further detailed investigation in form of a CT or MRI of the cervical spine is almost necessary if there is doubt over the diagnosis, the view is not satisfactory, or does not match the clinical evaluation.
As CT and MRI have become commonly available, these are better primary investigations for the purpose.
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