(1) The lower segment of the cervical spine is the most active and more mobile, with more chances of injury, but cervical 7 has more muscle protection and good stability because of the larger transverse processes, so it is not easy to be injured. (2) The spinal canal gradually becomes smaller from top to bottom, for example, the anterior and posterior diameter of the first cervical spine is 22.9 mm, while the sixth cervical spine is 17.5 mm. but the cervical spinal cord is the opposite of it. The lower segment is thickened by cervical expansion, so spinal cord compression is likely to occur. (3) The intervertebral foramen becomes progressively smaller from top to bottom, but the lower segment of the brachial plexus nerve root, which is generally thicker than the upper cervical segment of the cervical plexus, is therefore prone to injury. (4) The transverse foramina of cervical 5 and 6 are close to the vertebral body, and when there is bone redundancy formation on the vertebral body, it is easy to compress the vertebral artery and other tissues at cervical 5 or 6. (5) The lower cervical spinal cord has poor blood flow, which can easily cause ischemic disorders. (6) The spinal nerve roots of the upper cervical segment leave the spinal cord in a parallel manner and have less chance of injury, while the spinal nerve roots of the lower cervical segment travel obliquely downward in the spinal canal and have more chance of injury.