Burst fracture is vertebral fracture that involves the anterior and middle column. Burst fracture is unstable unlike compression fracture because both anterior and middle columns are involved and can compromise canal often caused by retropulsion of bone.
In Denis three column classification anterior column consists of anterior longitudinal ligament, anterior 2/3 of vertebral body and annulus; middle column consists of posterior longitudinal ligament and posterior 1/3 of vertebral body and annulus; posterior column consists of pedicles, lamina, facets, ligamentum flavum, spinous process and posterior ligament complex consisting of supraspinous ligament, interspinous ligament, ligamentum flavum and facet capsule.
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 fracture 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.
Neurologic injury from a burst fracture ranges from no injury at all to complete paralysis and generally correlates with severity of injury. Neurologic deficit s may cause loss of strength, sensation or reflexes below the level of the injury and may even cause
paralysis of the legs and loss of control of the bowel and bladder.
Mechanism of Injury
They typically occur from severe trauma, such as a motor vehicle accident or a fall from a height.
The anterior cortex fails in compression, either or both the end plates get fractured The middle column also fractures, and a portion of the body gets retropulsed backward into the canal. The posterior elements may also get fractured.
Burst fractures may be subdivided by fracture pattern as follows
This type of injury occurs with axial loading and it results in fractures of both upper and lower end-plates
This is the most common type of burst fractures and accounts for almost 50% of the burst fractures. In this injury only upper end-plate is fractured
It is a very uncommon injury and results in disruption of only the lower end-plate
In this injury, rotational displacement of one body relative to the other occurs
It is a lateral compression injury and occurs with traumatic scoliosis
Presentation of Burst Fracture
Burst fracture cause severe pain at the level of the fracture and may radiate to lower limbs too. 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.
Imaging of Burst Fracture
Xrays are basic investigation and it is recommended to view entire spine as concomitant spine fractures may be present.
AP view hows widening of pedicles. Lateral view shows retropulsion of bone into canal and kyphotic deformity
CT defines the fracture better.
It is useful to evaluate spinal cord or thecal sac compression and provides insight to amount of injury to cord.
Treatment of Burst Fracture
Nonoperative Treatment of Burst Fracture
A stable burst fracture may be treated without surgery. In general, a stable burst fracture is one in which there is no neurologic injury, in which the angulation of the spine is less than 20 degrees and in which the amount of spinal canal compromise is less than 50 percent. In these patients, treatment with a brace may lead to an excellent result.
Bracing can be used to immobilize stable burst fractures. It can be in form of Thoraco lumbar sacral orthses or extension cast. The usual period of immobilization is for 3 months.
After brace is applied, the patient is radiographed to check stability, loss of height or increase in kyphosis [All these indicate underlying posterior ligamentous insufficiency].
If everything is satisfactory, patient is mobilized with physical therapy. Frequent x-ray for follow up are done.
Occasionally, a fracture that was thought to be stable and treated in a brace may begin to angulate while in the brace. This may necessitate a later decision to perform surgery. All burst fractures require some type of treatment.
Operative Treatment of Burst Fracture
Surgical treatment of the burst fractures involves decompression and stabilization. The spine can be approached through anterior and posterior approach.
Unstable burst fractures usually do better with early surgery.
A burst fracture is considered unstable if neurologic injury is present, angulation of the spine is greater than 20 degrees, there is subluxation or dislocation of the spine, or there is greater than 50 percent spinal canal compromise.