In daily life, when we swing the whip, we often throw it backward first, and then swing it forward. The mechanism of whiplash injury is similar, and it is usually seen when a vehicle is traveling at high speeds when braking sharply or crashing. At this time, due to the action of inertial force, the head and neck are first flexed forward, and the frontal face is hit from the front (mostly the windshield or the backrest of the seat in front), which causes the head and neck to be overextended backwards, resulting in cervical hyperextension injury. In addition, the same can be said for falling from a height in the neck position and being violently pulled backward and upward.
Cervical spinal cord injury caused by cervical hyperextension violence, usually with mild or insidious bone injury, X-ray is often without abnormal signs, easy to be missed and delayed**. However, this kind of injury is not uncommon, accounting for 29% to 50% of all types of cervical spine injuries, often combined with spinal cord ** syndrome, more common in middle-aged and elderly people.
Depending on the point of focus, in addition to various injuries such as posterior cervical dislocation, Hangman fracture, and odontoid fracture with posterior atlantoaxial dislocation, the most serious consequence is spinal cord injury. In normal cervical extension, the spinal cord and dural sac in the spinal canal are folded (accordion-style) and compressed and shortened; However, if the anterior longitudinal ligament is ruptured and the intervertebral space is separated, the spinal cord is elongated, and the dural sac has a certain restraining effect. In this case, if the cervical spinal canal is narrow, the spinal cord is embedded between the abrupt lordosis and inverted ligamentum flavum and the bony spinal canal wall in front of it, especially when there is a posterior process of the nucleus pulposus or bone spur formation in front of the spinal canal, this hedged pressure is easy to concentrate on the spinal canal, causing congestion, edema or bleeding around the place. In addition to spinal cord syndrome, cervical hyperextension injury can also cause anterior spinal cord syndrome, which is distinguished as follows
Clinical presentation: Neck symptoms In addition to posterior neck pain, anterior longitudinal ligament involvement is also accompanied by anterior neck pain. Neck movement is markedly limited, especially in the form of supine extension. It is often accompanied by significant tenderness around the neck. Symptoms of spinal cord injury Because the pathological changes are located around the **duct, the lesion becomes more severe the closer to the **duct, so the deep pyramidal tract is first affected. Upper limb paralysis is heavier than lower limb paralysis, and hand dysfunction is heavier than shoulder and elbow. The main manifestations of sensory function involvement are the loss of temperature sensation and pain sensation, while the presence of positional sensation and deep sensation is called sensory dissociation. In severe cases, fecal incontinence and urinary retention may be present.
widening of the anterior vertebral shadow on lateral x-ray in the early post-traumatic period, and in higher levels of injury (rarely), the main manifestation is a widening of the retropharyngeal soft tissue shadow (normal 4 mm); In contrast, when the level of injury is below neck 4, the posterior laryngeal soft tissue shadow is significantly widened (normal 13 mm), but a normal prevertebral soft tissue shadow does not rule out hyperextension injury, and physical examination and MRI must be combined. The anterior edge of the intervertebral space of the injured vertebral segment is usually wider than that of other vertebral segments, and there may be avulsion of small bone fragments at the anterior and inferior edge of the previous vertebral body (15% to 20%). The majority of cases show sagittal stenosis of the spinal canal, and approximately half of cases are accompanied by bone spur formation at the posterior edge of the vertebral body. MRI shows the extent of disc herniation, soft-tissue injury, and spinal cord involvement. CT scan is helpful in identifying bone injury and noting signs of laminologic fracture.
Due to the easy missed diagnosis, it is necessary to pay attention to the following when clinically treating patients with head and neck trauma
1. Detailed medical history collection can often provide the mechanism of injury; People with head injuries should also try to understand the posture and type of violence at the time of the injury.
2. Cervical spine X-rays should be taken for cranial and facial injuries, and for any patient with suspicion, cervical spine X-rays should be listed as routine to avoid covering up cervical spine injuries due to other parts.
3. When the upper cervical spine is injured and the nerve symptoms are low, it is necessary to pay attention to the low cervical spine, and the dynamic position X-ray is helpful.
4. Typical spinal cord ** syndrome often indicates cervical hyperextension injury, but it should be noted that vertical compression fracture of the vertebral body can also be caused.
Cervical cord hyperextension injury is often combined with cervical degeneration and hyperplasia, ossification of the posterior longitudinal ligament of the cervical spine, etc., which are induced by trauma, and non-surgical ** often has little effect, and surgical decompression creates good conditions for functional recovery. The surgical method is based on the location and extent of the spinal cord compressor, and the appropriate approach and decompression method are selected. Front-based compression, such as a single or a few segments, should be decompressed by the front; Posterior predominant compression or anterior compression with extensive ossification of the posterior longitudinal ligament may be an option for posterior decompression. Postoperative upper limb recovery is the slowest and hand function recovery is the worst, often due to spinal cord injury affecting the anterior horn cells, resulting in atrophy of the intrinsic muscles of the hand, and residual dysfunction.