Posterior dislocation of the cervical spine is rare and is one of the severe types of hyperextension injuries, with hyperextension force being the primary cause of injury, commonly seen in the elderly. The most frequently injured segments are concentrated at C4 to C6.

bubble_chart Pathogenesis

Violence acting on the face, forehead, and cheeks can cause hyperextension of the cervical spine. When the force exceeds the tension of the anterior cervical muscles and the anterior longitudinal ligament, the cervical spine becomes extremely hyperextended. Since the human body is relatively stable, the vertebrae below _C7 do not shift with neck movement, generating a horizontal shear force at the cervical lordosis. The combined action of this horizontal shear force and hyperextension violence can tear the anterior ligament. As the violence continues, it may lead to intervertebral disc rupture, posterior facet joint hyperextension, capsular ligament tear, and even the lower edge of the upper vertebral body sliding backward over the upper edge of the lower vertebral body, resulting in a typical posterior cervical {|###|}dislocation{|###|}. The spinal canal becomes deformed at the dislocation segment, and the spinal cord can be {|###|}injury{|###|} due to compression between the posteriorly displaced posterior edge of the vertebral body and the upper edge of the lamina of the lower vertebral segment. Additionally, ruptured posterior longitudinal ligaments, herniated intervertebral disc tissue, and infolded ligamentum flavum can all contribute to spinal cord {|###|}injury{|###|}. After the violence ceases, reduction may sometimes occur immediately.

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1. Mostly hyperextension injuries, such as a history of violent impact to the forehead or face.

2. The face and forehead may exhibit skin abrasions, contusions, and subcutaneous hematomas.

3. Neck pain, restricted neck movement, and muscular rigidity or spasms in the neck.

4. Approximately over 80% of cases are accompanied by clinical manifestations of central cord syndrome, including limb paralysis (more severe in the upper limbs than the lower limbs), sensory dissociation, and abnormal reflexes.

bubble_chart Auxiliary Examination

Plain X-ray films When cervical spine violence disappears, due to the contraction of neck muscles, the dislocated cervical spine may return to normal alignment. Therefore, ordinary plain X-ray films may show normal signs. However, small fracture fragments may appear in the posterior structures. The prevertebral soft tissue may show swelling and thickening. The anterior opening of the intervertebral space increases, and avulsion fractures may occur at the anterior edge of the vertebral body.

On flexion-extension dynamic lateral radiographs, the injured segment shows significant instability, especially in the extension position, where the upper vertebral body shifts backward. This is exactly antagonistic to flexion injuries, which mainly manifest as forward displacement of the upper vertebral body in the flexion position.

Magnetic resonance imaging Due to the high rate of spinal cord injury, magnetic resonance images can show spinal cord edema, signal changes, and enhancement at the injured level. Cross-sectional images may reveal blurred boundaries between gray and white matter in the spinal cord. Additionally, damage to the posterior facet joint capsules can also be visualized.

1. Non-surgical treatment is the primary approach in the early stage of injury: Generally, occipitomandibular traction is employed, maintaining a neutral position with a traction weight of 2-3 kg for 2-3 weeks, followed by cervicomandibular fixation for 2-3 months. If instability is evident, head-neck-thorax gypsum fixation is preferable.

2. Surgical treatment: In the early stage of injury, surgery is indicated for cases with confirmed spinal cord compression at a specific segment level that do not respond to non-surgical treatment, as well as for late-stage [third stage] cases presenting with cervical instability and spinal cord compression.

Anterior cervical decompression is the preferred method, as spinal cord compression caused by hyperextension cervical injuries often occurs at the anterior wall of the spinal canal. Autologous iliac bone grafts or banked allografts can be used for fixation during surgery. The selection of surgical segments is based on dynamic radiographs and MRI images, with myelography used when necessary.