Orthopaedic Knowledge Update
- Updated on: 2018-04-12
- Read original article here
A. Jay Khanna, MD, MBA Brian K. Kwon, MD, PhD, FRCSC
Introduction
Subaxial cervical spine injuries include fractures, dislo-
cations, and ligamentous injuries between C3 and T1.
Subaxial cervical spine injury most frequently occurs in
young men in association with a motor vehicle crash, a
fall from a height, or a sports injury. This injury also is
likely to occur in patients who are elderly, particularly
those with an underlying degenerative condition, spinal
stenosis, or osteoporosis.
The protocols for clearance of the cervical spine in
patients with blunt trauma were recently described.1
Along with a careful history and physical examination,
the evaluation of a patient with a known or suspected
cervical spine injury begins with imaging. The imaging
studies typically include conventional radiographs, CT,
and MRI. Conventional radiography is widely and
quickly available and therefore has been the first-used
modality. However, conventional radiographic studies
have low sensitivity, ranging from 52% to 85%.1-3
Flexion-extension cervical spine radiographs occasion-
ally are used to evaluate patients with suspected cervi-
cal spine instability, typically in a subacute setting, but
they are not cost-effective or efficacious in the acute
setting, especially given the risk associated with their
acquisition.1,4-7
With the widespread availability of multidetector
imaging, CT increasingly is accepted as a first-line im-
aging modality for patients with a known or suspected
cervical spine injury. Only 0.7% of cervical, thoracic,
and lumbar fractures in 3,537 patients were missed on
CT, and these were fractures requiring minimal or no
treatment.8 The disadvantages of CT include the rela-
tively high cost and radiation exposure.9
Although CT provides excellent anatomic detail and
spatial resolution, MRI provides optimal visualization of
soft-tissue structures, allowing identification of any lig-
amentous injury and the type and extent of a neural com-
pression or spinal cord injury. The primary indication for
MRI of the cervical spine after trauma is the presence of
a neurologic deficit. MRI can effectively be used to eval-
uate compression of the neural elements by osseous frag-
ments, disk material, or epidural hematomas. The excel-
lent visualization of the spinal cord on MRI reveals the
presence and extent of any cord signal changes. Ligamen-
tous injury is best evaluated on short tau inversion re-
covery or fat-suppressed T2-weighted MRI.10,11 MRI is
most sensitive for detecting ligamentous injury within the
first 24 to 72 hours after injury.12-14
Five level I studies enrolled a total of 464 patients
with cervical spine trauma who were evaluated with
MRI, CT, or conventional radiography. Meta-analysis
found an overall sensitivity of 97.2%, an overall speci-
ficity of 98.5%, and a negative predictive value of
100%.15 The incidence of abnormalities detected on
MRI but not on conventional radiographs or CT was
20.9%. MRI and CT allow optimal evaluation of the
occipitocervical and cervicothoracic junctions, which
are not well visualized on conventional radiographs.
It is important to keep in mind that MRI cannot al-
ways be obtained in the acute trauma setting because of
specific limitations relating to the treatment of patients
with severe multisystem trauma, such as potential he-
modynamic instability; the presence of traction, other
stabilizing devices, and ventilators; difficulty of access
to an unstable patient during imaging studies; and lack
of 24-hour MRI availability.
The Allen-Ferguson classification originally was de-
scribed in 1982 based on static radiographs of 165 pa-
tients.16 The categories of fractures refer to the postu-
lated position of the spine at the time of injury and the
presumed dominant mechanism of spine failure: com-
pressive flexion, vertical compression, distractive flex-
ion, compressive extension, distractive extension, or
lateral flexion. Each category is subclassified into stages
based on the extent of anatomic disruption.
Dr. Khanna or an immediate family member serves as a board
member, owner, officer, or committee member of the North
American Spine Society and the American Academy of Ortho-
paedic Surgeons; is a member of a speakers’ bureau or has
made paid presentations on behalf of AO Spine North America;
serves as a paid consultant to or is an employee of Orthofix,
Inc.; has received research or institutional support from Zimmer
and Orthofix, Inc; and owns stock or stock options in New Era
Orthopaedics, LLC. Dr. Kwon or an immediate family member
serves as a paid consultant to or is an employee of Medtronic
Sofamor Danek and has received research or institutional sup-
port from Medtronic Sofamor Danek.
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