Introduction:
The backbone, which is also known as the spine or vertebrae, is the central support system of the body. Usually, there are 33 vertebrae stacked one over the other in a tubular fashion forming the vertebral column.
The vertebral column can be divided into five regions from top to bottom, namely the cervical spine (neck region), thoracic spine (upper and middle back region), lumbar spine (lower back region), sacrum, and coccyx (both lying in the center of the hip bone).
What Is a Chance Fracture?
A Chance fracture means the fracture of the vertebra at the junction of the thoracic and lumbar spine. It is a bone injury with a through and through horizontal bone fracture that involves the entire vertebral body.
The condition was first identified by a radiologist, G. Q. Chance, in the year 1948 and described as the horizontal splitting fracture of the spine. Chance fracture is common in a person wearing a lap seat belt during a car collision. Hence it is also known as a seat belt injury. Children and young adults are more prone to Chance fractures with male predominance.
What Are the Causes of a Chance Fracture?
A Chance fracture occurs as a consequence of flexion-distraction injury. Sudden forcible bending of the spine against a restrained object results in splitting of the bone and thus leading to distraction on the back surface and compression over the front surface area. The fulcrum line is in the middle of the abdomen.
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The most common cause of a Chance fracture is car crashes.
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Less commonly, it can occur during a fall or a blow.
What Are the Signs and Symptoms of a Chance Fracture?
The Chance fracture causes an unstable spinal column. Based on the biomechanical function, Francis Denis divided the spine into three vertical columns.
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Anterior Column: Involves the front two-thirds of the vertebral body and the intervertebral disc (a dense connective tissue between each vertebra) along with the corresponding longitudinal ligaments.
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Middle Column: Involves the back one-third of the vertebral body and the intervertebral discs with the associated longitudinal ligaments.
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Posterior Column: Involves the vertebral projections, associated joints, and the major and minor ligaments.
The spine becomes unstable when two of the three columns are involved in the injury. A Chance fracture is a major spinal injury with the distraction of the middle and the posterior column. The compression of the anterior column is either absent or only minimally present.
The clinical findings are:
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Bowel trauma (injury to the spleen, small intestine, pancreas, and the mesentery) due to squeezing of the bowel structures between the spine and the object.
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Deformity of the spine.
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Damage to the nerves and blood vessels.
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Brain injury.
Patients may have,
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Bruising in the tummy area.
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Severe lower back pain.
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Loss of bowel and bladder control.
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Generalized weakness and numbness in the lower part of the body.
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Loss of function and sensation in the legs.
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Unconsciousness.
How to Diagnose a Chance Fracture?
1. Physical Assessment:
The physician may inspect and palpate to check for,
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Seat Belt Sign: A horizontal area of abrasion in the tummy skin that was in contact with the lap seat belt during injury. Usually, the involved area is discolored (darker) due to internal bleeding.
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Neurological Functions: Involuntary reactions, movements, and sensations in the lower part of the body are examined. Perception and memory skills are tested.
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Local Signs: Back pain and midline tenderness are present. The injured area and the neighboring parts are highly sensitive to pain and soreness.
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Others: Injury to other parts of the body, loss of blood, and alcohol or drug content in the blood are also assessed.
2. Imaging Modalities:
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X-Rays: The spinal malalignment and displaced fracture fragments can be identified in plain X-rays.
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CT (Computed Tomography): An appropriate choice of imaging for a Chance fracture is a CT scan. The horizontal line of the fracture, compression, and distractions in the body of the vertebra is clearly visualized in CT images.
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MRI (Magnetic Resonance Imaging): Soft tissue injuries like the involvement of intervertebral discs, ligaments, muscles, and spinal cord can be detected accurately through MRI scanning.
How to Treat a Chance Fracture?
Depending on the clinical findings, a Chance fracture can be treated either conservatively or surgically;
1. Conservative Management:
When only the bone is involved in the injury, conservative treatment like immobilization, stabilization, and rest is sufficient.
Immobilization can be achieved using a cast or TLSO (thoracolumbosacral orthosis - premade supporting device to stabilize the spinal column). For casting, the patient is laid facing upward over the Risser table (a specially designed table for spinal casting procedures). A custom-made plaster or fiberglass material is used for casting. Immobilization is continued for eight to twelve weeks with periodic check-ups.
Conservative management may not help patients who are obese.
2. Surgical Management:
Surgery is considered when the patient exhibits neurological problems and ligament injuries. Surgery involves opening the injured site under anesthesia, realigning the bone, and fixing them with screws or pins. Spinal decompression may be needed in managing the compressed nerves to relieve pain, numbness, and other associated symptoms.
Post-treatment, an enhanced rehabilitation program should be planned to gain muscle strength and range of motion. Dietary changes and bowel and bladder function are the other factors to be considered.
What Are the Complications of Chance Fracture?
- Persisting lower back pain - one of the significant complaint the patients faces in the future after sustaining a Chance fracture.
- Kyphosis - a forward bending of the spine. The degree of residual bend depends on the severity of injury acquired through a Chance fracture.
- Development of pressure sores.
Conclusion:
Most cases of a Chance fracture are treated successfully, and the patients are free from symptoms. The treatment outcome largely depends on the extent of abnormality in the spinal curvature. Some patients will have persistent lower back pain in the future. Early assessment and treatment of this injury are important as they are associated with serious gut injuries.
Hence, people should be aware of the traumas caused by motor vehicle collisions and adhere to proper safety protocols while traveling.
