Purpose
C1, C2, and soft tissues are observed.
Observations of Jefferson fracture and odontoid process fracture.
Preliminary Confirmation
Always observe lateral images and obtain a physician’s permission before taking radiograph with the mouth open.
In case of trauma, avoid hyperextentional view.
If an open mouth is not possible, consider the Fuchs or Judd technique.
Remove any obstructive shadows.
(If hair is tied up, bundle it or remove necklaces, hairpins, etc.)
Positioning
Rect or supine.
The patient head should be viewed from the cephalic side to avoid head torsion, and the sagittal plane should be perpendicular to the imaging detector.
At maximum aperture, the angle of head should be such that the line connecting the inferior margin of the maxillary incisors with the mastoid process (or the line connecting the nasal root with the external auditory meatus) is perpendicular to the imaging detector. If this is not possible, the angle of incidence should be adjusted.
The tongue should be lowered toward the mandible to avoid obstructive shadows.
The vertical center of the cassette should be aligned with the height of the mastoid process.
CR, distance, field size
CR : Vertical incidence toward the center of the open mouth.
Distance : Nearest approach ~ 100 cm.
Irradiation : The head side should be narrowed so as not to include the eyes. The left and right sides should be extended to the skin surface.
Since the open mouth often moves, observe the patient carefully and press the exposure switch when the patient is not moving.
To minimize the time between opening the mouth and exposure, set the imaging conditions in advance.
Exposure condition
Suspend respiration.
55kV / 5mAs
grid ( – ）
Image, check-point
Normal (Radiopaedia)
Jefferson fracture (Radiopaedia)
The lateral mass and transverse process (C1) should be observable.
The odontoid process (C2) should not be overexposed and the vertebral body should be observable.
The gap of the atlantoaxial joint should be symmetrical and wide.
The upper incisors and occipital bone should not overlap C1/C2.
Since overlap of the obstruction to the target area may be unavoidable depending on the skeletal structure, other imaging methods (Fuchs or Judd method) or CT should be considered.
Movie
Related materials
Close mouth view
Fracture Classification : Anderson’s Classification
Type 1: Oblique fracture of the tip of the dental process
Type 2: Fracture up to the base of the odontoid process
Type 3: Fracture extending to the C2 vertebral body
Type 2 is prone to pseudoarthrosis and requires surgical intervention.
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