Burst Fractures: Defined and Diagnosed
A burst fracture is a descriptive term for an injury to the spine in which the vertebral body is severely compressed. They typically occur from severe trauma, such as a motor vehicle accident or a fall from a height. With a great deal of force vertically onto the spine, a vertebra may be crushed.
If it is only crushed in the front part of the spine, it becomes wedge shaped and is called a compression fracture. However, if the vertebral body is crushed in all directions it is called a burst fracture. The term burst implies that the margins of the vertebral body spread out in all directions. This is a much more severe injury than a compression fracture for two reasons. With the bony margins spreading out in all directions the spinal cord is liable to be injured. The bony fragment that is spread out toward the spinal cord can bruise the spinal cord causing paralysis or partial neurologic injury.
Also, by crushing the entire margin of the vertebral body the spine is much less stable than a compression fracture.
Neurologic injury from a burst fracture ranges from no injury at all to complete paralysis. The degree of neurologic injury is usually due to the amount of force that is present at the time of the injury and the amount of compromise of the spinal canal. With a greater amount of force, more bony fragments can be forced into the spinal canal causing greater loss of spinal cord function. This may cause loss of strength, sensation or reflexes below the level of the injury.
Typically, in a burst fracture that occurs at the junction of the thoracic and lumbar spines paralysis of the legs and loss of control of the bowel and bladder may result. In an incomplete spinal cord injury only partial paralysis or reflex loss is seen. With mild burst fractures only transient symptoms may be present or no neurologic injury may be present.
Burst fractures cause severe pain. Typically, this is pain at the level of the fracture, that is, in the back. However, pain may also be present in the legs following the distribution of the affected nerves. Many patients complain of an electric shock type sensation into their legs when there is spinal cord compression. Most patients with a burst fracture are unable to walk immediately after the injury. Seldom, the patient may walk away from an accident and still have a burst fracture. However, often the amount of pain that is present is severe enough that patients know it is a good idea not to walk.
At the scene of the accident, patients complaining of severe back pain should not be placed into a seated for flexed position. They should be kept lying flat and transported in the flat position. A patient who stands or sits with a burst fracture may increase their neurologic injury. Burst fractures require immediate medical care by an orthopedic or neurosurgeon trained in spinal surgery. The patient should be transported to an emergency room and x-rays obtained.
The diagnosis of a burst fracture is usually made by x-rays and a CAT scan. Occasionally, an MRI scan may be ordered as well, in order to assess the amount of soft tissue trauma, bleeding or ligament disruption. The review of the CAT scan and x-rays allows the treating physician to make a determination as to the level of the fracture, whether it is a compression fracture, burst fracture or fracture dislocation, and to determine the amount of spinal canal compromise and spinal angulation. All of these factors enter into the treatment decision process.
The physical exam should be performed to document both spinal deformity, that is, angulation of the spine or tenderness of the spine at the level of fracture, as well as, a neurologic exam.
Neurologic exam should include testing of the muscle strength, sensation and reflexes of the lower extremities, as well as, testing of bowel and bladder sphincter control.