Standard and additional projections
A comprehensive approach involving several positioning options is used for a full assessment of the cervical bone structures. This is necessary for spatial reconstruction of the anatomical region and ruling out occult pathologies.
The classic series of radiographs includes:
- Anteroposterior projection (anteroposterior) — a basic overview radiograph.
- Lateral projection (lateral) — allows for the assessment of physiological curves. When the patient is in a standing position during imaging, a straightened cervical lordosis (decreased cervical lordosis) is frequently observed. A key criterion for a correctly performed radiograph is clear visualization of the upper part of the first thoracic vertebra (Th1 or T1).
- Right oblique projection (right oblique) — optimal for examining the intervertebral foramina. Normally, the left intervertebral foramina (intervertebral neuroforamina) should appear open on such a radiograph, with no signs of obliteration or narrowing.
- Dynamic flexion radiography (dynamic flexion) — a functional test. When performed, a physiological decrease in mobility of the lower cervical segments may be detected. It is extremely important to remember that detecting minimal displacement of a vertebral body anteriorly — anterolisthesis (anterolisthesis) — at the C3–C4 level during maximum neck flexion is considered a normal variant rather than a sign of traumatic injury.
Visualization of the craniocervical junction
Imaging the junction between the skull and the spine is a technically challenging task, especially in patients following acute trauma, where achieving ideal positioning is extremely difficult due to pain or a forced head position.
The primary goal of craniocervical junction radiography is to obtain a fully unobstructed view of the dens of the second cervical vertebra (dens), free from overlying bone structures. Two main projections are used for this: the anteroposterior (anteroposterior) projection, performed through the patient's open mouth, and the standard lateral (lateral) projection.
Assessment of positioning accuracy and rotational artifacts: Even a slight head turn during the open-mouth view leads to projection distortions. For example, if the patient's head is slightly turned to the right, the radiograph will show an asymmetric position of the C2 dens within the bone ring of the first cervical vertebra — the atlas (atlas). A reliable radiographic landmark is used to confirm the rotational nature of such asymmetry. An imaginary plumb line must be drawn precisely between the upper central incisors (teeth 11 and 21). If this line does not pass strictly through the anatomical center of the odontoid process, the asymmetry is caused by head rotation rather than true displacement of bone structures.
Diagnosis of spinal segment instability
Radiography plays a leading role in the initial diagnosis of spinal instability. This syndrome is characterized by pathological excessive mobility between adjacent vertebrae.
The main radiographic signs of instability include:
- Vertebral body displacement: displacement of an overlying vertebra anteriorly is called anterolisthesis (anterolisthesis), and posteriorly — retrolisthesis (retrolisthesis).
- Complex changes: an increased displacement of vertebral bodies accompanied by a significant widening of the distance between their spinous processes (spinous processes) is considered pathological.
Functional radiographs (dynamic radiography) are widely used not only in the cervical spine but in other spinal regions as well. Specifically, in the lumbar spine, they are regularly performed in patients diagnosed with spondylolisthesis (spondylolisthesis), as well as for routine stability control of operated segments in the postoperative period.
Evolution of imaging methods: myelography and MRI
Historically, detailed assessment of the spinal canal, spinal cord, and nerve roots involved myelography (myelography) followed by post-myelography computed tomography (post-myelography CT).
Currently, these techniques have almost completely lost their relevance and have been replaced by magnetic resonance imaging (MRI / MR imaging).
The rapid transition to MRI is driven by a number of undeniable advantages:
- Absolute non-invasiveness (non-invasive).
- Painless procedure (painless).
- Absence of radiation exposure (ionizing radiation) and the need for puncture injection of contrast agents into the subarachnoid space, which eliminates the risk of complications specific to myelography.
Class and exam questions
Why might the cervical lordosis appear straightened on a lateral radiograph?
Straightening of the cervical lordosis is often a consequence of the patient's upright position at the time of the scan and, in the absence of other symptoms, can be considered a physiological variant.
How to distinguish true C2 dens displacement from improper positioning on an open-mouth view?
It is necessary to assess the plumb line between the upper central incisors. If the head was rotated, this line will not project strictly through the center of the odontoid process, creating the appearance of dens asymmetry within the atlas ring.
Is C3–C4 anterolisthesis during flexion considered a sign of trauma?
No, minimal displacement (anterolisthesis) at the C3–C4 level detected during a dynamic functional test at maximum flexion is a normal variant.
What else to study on this topic
- Quality criteria for the lateral view and visualization of the Th1 vertebra
- Anatomy of the intervertebral foramina and their projection assessment
- Biomechanics of the craniocervical junction (relationship between C1 and C2)
- Radiographic differential diagnosis of types of spondylolisthesis
- Method for measuring the distance between spinous processes
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