spine fracture

Burst Fractures: Axial Loading Leading to Ouch!

virtualmedstudent

Burst fractures are a specific type of spine fracture in which the body of a given vertebrae “bursts” into pieces. By definition a burst fracture involves the entire vertebral body. The image below is an example of a normal lumbar spine with the vertebral bodies outlined.

Burst fractures most commonly occur at the junction between the thoracic and lumbar spine. This junction is an area where the rigid thoracic spine transitions to the more mobile lumbar spine, and hence is an intrinsic point of weakness. This is why most burst fractures occur between the T10 through L2 vertebrae.

CT vertebral body

Axial loading of the spine is what causes burst fractures. They typically occur after a traumatic events like car accidents or falls from significant heights. Elderly individuals, and those with poor bone quality, may suffer burst fractures after minor trauma such as falling from a chair.

Signs and Symptoms

Burst fractures invariably present with back pain at the site of the fracture. Depending on the exact location signs and symptoms of nerve root compression or lower spinal cord injury may occur.

If the nerves that dangle in the lumbar spine (aka: the cauda equina) get compressed by the fragments of bone then weakness, numbness, tingling, and even bowel and bladder problems may occur.

Burst fractures between T10 and L1 can cause damage to the end of the spinal cord (the spinal cord ends at L1 or L2 in most individuals), which can lead to lower extremity weakness, or even paralysis, as well as bowel and bladder dysfunction.

Diagnosis

Diagnosis of a burst fracture is made using a combination of x-rays, CT scans, and MRIs. These three imaging modalities serve different functions when evaluating the severity of a burst fracture.

X-rays are usually the first imaging ordered in patients with suspected spine fractures. If the plain x-rays show a burst fracture then CT scanning is usually done to further assess the degree of bony injury (see image below for an example of an L2 burst fracture).

MRI is used to detect ligamentous injury. The degree of ligamentous injury indicates a higher degree of instability; information about ligament integrity helps determine treatment options.

Burst Fracture Lumbar Spine

Treatment

Treatment of burst fractures is highly dependent on the severity of the burst fracture. Treatment is either conservative with immobilization in a brace (ie: a "TLSO" or thoracolumbar sacral orthotic brace) or surgical fixation.

Burst fracture after instrumentation
As a rough rule of thumb patients with any of the following criteria should be strongly considered for surgical correction:

  • Greater than 50% vertebral body height loss.
  • Greater than 25 to 40 degrees of kyphosis.
  • Greater than 50% spinal canal compromise.
  • Significant posterior ligamentous injury.
  • Any neurological signs or symptoms referable to the injury.
  • If the patient fails conservative therapy with a brace.

Surgical correction can be achieved in a variety of ways and is often related to surgeon preference. Some surgeons will remove a significant portion of the fractured vertebral body and place a “cage” in the area, a procedure known as a “corpectomy”. This, combined with rods and screws from posteriorly provides the greatest stability, but has a higher risk of nerve injury. Not uncommonly, the fractured vertebral body is left alone and rods and screws are placed from behind only. This is especially true if the fractured level shows minimal spinal canal compromise.

Overview

Burst fractures of the thoracolumbar spine typically occur after high impact axial loading. They usually occur between T10 and L2, but can be seen anywhere in the spine. Patients will almost invariably have pain at the fracture site and may or may not have neurological signs and symptoms depending on the severity of the fracture. Diagnosis is made with CT, plain x-rays, and MRI. Treatment is highly dependent on the individual fracture and ranges from bracing to surgical fixation.

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Latin for Toothlike: Fractures of the Odontoid Process

virtualmedstudent

The odontoid process (also know as the "dens") is the finger of bone that sticks up from the second cervical vertebrae (ie: the axis).

It articulates via numerous ligaments to the anterior arch/ring of the first cervical vertebrae (ie: the atlas) to form a joint. This joint is what allows you to rotate your head from side to side as if you were nodding “no”.

Axis (C2)

Fractures of the odontoid typically occur after traumatic events. In younger, otherwise healthy individuals tremendous force is necessary to fracture the odontoid. Breaks are typically seen after car, motorcycle, or sporting accidents. In older, osteoporotic people simple ground level falls can result in a fracture. Less commonly, fractures of the odontoid may be caused by tumor chipping away at the underlying bone (a so called “pathologic” fracture).

Since the odontoid is a relatively long piece of bone it can fracture at one of several distinct sites. The most commonly used system (Anderson and D’Alonzo) categorizes fractures into one of three types:

  • Type 1 – a fracture at the tip of the odontoid.
  • Type 2 – a fracture at the base of the odontoid.
  • Type 3 – a fracture involving the body of the C2 vertebrae, which includes the odontoid within it.

Odontoid fractures

This grading system is important because it helps predict both stability of the C1-C2 (ie: atlanto-axial) joint and guides potential treatment options.

Signs and Symptoms

Roughly 80% of patients with odontoid fractures do not have any neurological injury to their spinal cord. The remaining patients can exhibit anything from quadriplegia to mild sensory disturbances. Patients with severe cervical spinal cord injury usually are unable to breath (secondary to diaphragm paralysis) and frequently die at the scene of the accident.

Many patients with odontoid fractures will have significant neck pain that radiates up into the scalp. This is usually caused by neck muscles spasming secondary to the injury.

Diagnosis

CT of odontoid fracture

CT scans, x-rays, and MRIs are all useful in diagnosing and properly treating odontoid fractures.

CT scans of the cervical spine provide excellent bony detail, and also help illustrate any additional fractures that may be present.

MRI of the cervical spine is useful for assessing any co-existent ligamentous injury. If ligamentous injury is present it drastically alters treatment decisions.

Treatment

Treatment of odontoid fractures is based on both bony and ligamentous injury. The goal of treatment is to stabilize the spine either by allowing the bone to heal on its own, or by fusing the spine artificially using rods, screws, and/or wires.

Placement of an odontoid screw is one method of fixing non-displaced type II fractures. However there are numerous contraindications for odontoid screw placement. For example severe angulation of the fractured segment precludes placement of a screw; barrel chested anatomy prevents an adequate angle for screw trajectory in the operating room. In addition, if the transverse ligament is disrupted, bony fixation with an odontoid screw alone will not stabilize the joint.

On the other hand, odontoid screws are beneficial because they typically stabilize the fracture with minimal restriction of neck motion.

Approaching the spine from behind is another option to stabilize odontoid fractures. Fusing the atlas (C1) to C2 or C3 is sometimes used if odontoid screw placement cannot be performed and the injury is deemed unstable. It is important to note that posterior approaches can restrict motion, especially in the high cervical spine.

Non-surgical options must ensure that the patient has minimal to no movement of the neck in order to give the bone an adequate chance to heal on its own. Rigid collars or halos are used to prevent neck motion.

Overview

Odontoid fractures come in three flavors depending on the location of the fracture. Symptoms can be anything from mild neck discomfort to quadriplegia, although neurological injury is surprisingly uncommon. Diagnosis is based on CT and MRI. Treatment is with cervical immobilization for an extended period of time, or surgical fusion. Treatment decisions are based on the degree of both bony and ligamentous injury, as well as the patient’s overall health status.

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