What is a Chance fracture?
A Chance fracture is a type of spinal injury. Chance fractures are also known as seat belt fractures. This is because they’re commonly caused by lap belt-style seat belts during car accidents. Since the addition of the shoulder belt, these injuries are much less common.
First described by G. Q. Chance in 1948, a Chance fracture is caused by flexion-distraction forces upon the spine. This is when the spine flexes, and then extends with too much force. A Chance fracture is one of three types of injuries resulting from these forces, which can injure the bone, ligaments, and discs of the spine.
Chance fractures most commonly occur in an area of the spine called the thoracolumbar junction (where the thoracic spine joins the lumbar spine). They typically involve the 12th thoracic vertebra and first or second lumbar vertebra.
The thoracolumbar spine has three columns. The first column is known as the anterior column. It consists of the anterior half of the vertebral body, disc, and anterior longitudinal ligament. The middle column contains the posterior half of the vertebral body, its associated disc, and posterior longitudinal ligament. The posterior column is represented by the pedicles, facet joints, lamina, spinous and transverse processes, and ligamentous complex. In the case of a Chance fracture, all three columns are involved, and the fracture line runs through the spine, injuring the lamina, pedicles, and vertebral body.
In children, this injury usually happens lower on the spine, in the area known as the mid-lumbar region.
In a Chance fracture, the bony elements of the spine are fractured but the ligaments remain intact. These injuries are highly unstable and often involve other abdominal injuries.
The main symptom of a Chance fracture is severe back pain that is worse when you move. Depending on the type of injury, other symptoms may occur. For example, if you sustain a Chance fracture due to a high-energy crash, you may also sustain a brain injury or lose consciousness.
Flexion-distraction forces are responsible for Chance fractures. When the weight of the upper body moves forward, while the waist and upper body remaining fixed, a flexion-distraction injury can occur.
A flexion injury typically will occur in the vertebral body while a distraction injury affects the posterior elements of the spine. For example, if you’re wearing a seat belt that only goes across your lap when you’re in a car accident, your upper body will bend forward — or flex — causing the front of the vertebra to be compressed or squashed while also being pulled away from the seat, or distracting. This causes the posterior column to pull apart and fracture due to the force of momentum.
See a doctor if you are experiencing back pain, especially if you were recently in a car accident or had a significant fall. If your doctor suspects you have a spinal injury, an X-ray is usually the first step in determining the type and severity of your injury.
However, if you’ve been involved in a high-energy trauma, it’s more likely that you’ll be taken directly to get a CAT scan in the emergency room. It’s also more than likely that your doctor will order an MRI as well to determine if there’s damage to the ligaments and spinal cord itself.
People with Chance fractures often also experience injuries to their internal organs. The pancreas and the duodenum are the organs most likely to be injured if you have a Chance fracture. In children, this is even more common.
If untreated, Chance injuries can result in progressive kyphosis, or excessive curvature of the thoracic spine. This can result in pain and spine deformity.
The treatment plan for the Chance fracture depends on the extent of the injury. If the CT or MRI scan shows damage to the spinal cord, or if there’s involvement of the posterior ligaments, it’s more likely that surgery will be required. During surgery, the spine will be stabilized with rods and screws.
If there is no damage done to the spinal cord, and surgery is not necessary, fractures can generally be reduced. Treatment will involve placing you on a Risser table with hyperextension applied to the thoracolumbar junction prior to applying a fiberglass or plaster cast, or a brace (thoracolumbosacral orthosis, aka TLSO) placed in extension.
Spinal injuries normally take quite a long time to heal. How fast your spinal injury heals will depend on the nature of the injury and other complications. If surgery is needed for part of your treatment, following your doctor’s postsurgical instructions exactly.
After your injury, your doctor may recommend physical therapy to help you get your full range of movement back.
Cold and hot therapy can also help manage the pain caused by your injury.