Types

There are several important points to understand about the spine and fractures:

• The vertebral bodies take most of the weight. If they are broken it was probably caused by an over-load.
• The facet joints restrict rotation. If they are broken the spine was probably over-rotated.
• The arch protects the nerves and spinal cord. If it is broken the risk of injury to the nerves is greater. The nerves are very close to the vertebral body and the intervertebral disc.
• A ring breaks in two places. If the ring of bone around the nerves is broken in one place there is usually another break. Such injuries are unstable. The pieces are likely to drift further apart.
• The transverse processes and the spinous processes are attachments for muscle. If they are broken (and nothing else), it is most likely because of over-pull by muscles (avulsion fracture).
• The stability of a fracture is a critical concern. If the displacement is likely to get worse the risk of progressive nerve injury is higher.
• The soft tissue component of the injury is important.

When considering the anatomy of the injured spine it is helpful to think of it as having three columns:

• anterior (front)
• middle
• posterior (back)

The anterior column consists of the front half of the vertebral body, the nucleus of the intervertebral disc and the anterior longitudinal ligament.

The middle column includes the back of the vertebral body and the posterior longitudinal ligament.

The posterior column is the ring of bone surrounding the nerves and the facet joints.

Damage to more than one of the columns makes for an unstable injury which is likely to displace further. This means that damage to the middle column is critical and is more serious. It is very unlikely that a fracture would affect the middle column alone. If this region is broken, it is very likely that there is damage in front or behind and the whole spine is unstable.

Wedge Compression Fractures: Forward flexion. Common in osteoporosis.

Transverse Process fracture: Avulsion by excessive contraction of psoas (the muscle that flexes the hip). Occasionally by direct impact.

Spinous Process Fracture: Forward flexion, avulsion fracture; direct trauma (blow).

Fractures of the Pedicle: (pars, hyperextension mechanism).

Chance Fracture: Flexion/distraction forces cause pull apart the bone. The fracture line passes through the spinous process, pedicles (ring) and the vertebral body. A head-on collision while wearing a lap seat belt is a common cause. This is an unstable fracture pattern but usually there is no major neurological injury.

Burst Fracture: This is caused by axial loading of the vertebral column. The center of the vertebral body is overloaded and it bursts sending fragments in every direction. This is an unstable injury as both anterior and middle columns are disrupted. The middle column fragments may be pushed back into the space available for the nerves. Neurological injury is common with this pattern of fracture.

Fracture Dislocation: This results from high energy trauma like a motor vehicle accident. Forcible rotation breaks the facet joints and the vertebral bodies. Then side-to-side bending shifts the fragments apart. The entire spine is disrupted with major displacement. Neurological injury is common with this pattern of injury.