Injuries of the spinal cord and cauda equina can be also classified according to the 'Rule of 3' into injuries of the cervical spine, thoracic spine and lumbar spine. Each can produce special problems and specific symptoms and signs.

In the thoracic spine the spinal cord is a very tight fit in the spinal canal, and minimal displacement as will usually result in a complete paraplegia.

In the cervical and lumbar spines the spinal canal is much larger, and displacement may occur without paralysis.

The stability of the spine is largely dependent on the supraspinous and interspinous ligaments. If these are intact, and there is no gap between the spinous processes, the spine is usually stable, and damage to the cord is unlikely.

It is important to note that injuries of the cervical and thoracic cord will cause a spastic paraplegia after the first 1 to 3 weeks of spinal shock have worn off.

Injuries at the thoraco lumbar region may damage both the cord and cauda equina and lead to a combined upper and motor type of paralysis.

Injuries of the cauda equina will cause a lower motor neurone paralysis as well as autonomic nerve damage.