Last Updated on December 8, 2023
A Chance fracture is an unstable horizontal spine fracture that extends from posterior to anterior through the spinous process, pedicles, and vertebral body. It is considered to be a flexion-distraction injury where the anterior column fails under compression while the middle and posterior columns fail under tension.
It was typically seen with users of lap seat belts that were initially used in vehicles. Therefore, it is also called a seat belt fracture.
Chance fractures are associated with a high rate of intrabdominal injuries, as high as in 50% of the cases.
distraction of the middle and posterior elements of the spine. Other less common mechanisms of injury include falls and assaults.
The injury is mostly seen in young adults, though the age ranges from 10 to 55 years. Chance fracture is reported to be 3 times more common in males than females.
Chance fracture is named after George Quentin Chance who described the fracture in 1948.
In adults, the Chance fracture most commonly is found in the upper lumbar spine, but it may be observed in the mid-lumbar region in children.
Unrecognized, Chance injuries may result in progressive kyphosis with ensuing pain and deformity.
Relevant Anatomy
Chance fractures are mostly seen at the thoracolumbar junction (T10-L2) in adults. It affects the midlumbar spine in children.
Denis proposed a three-column theory of the spine that is still used to explain the mechanism of injury. These are
- Anterior column
- Anterior two-thirds of the vertebral body
- Anterior two-thirds of the disc
- Anterior longitudinal ligament.
- Middle column consists
- Posterior one-third of the vertebral body
- Posterior one-third of disc
- Posterior posterior longitudinal ligament.
- Posterior column
- Pedicles
- Facet joints
- Lamina
- Spinous process
- Transverse processes
- Ligamentum flavum
The anterior and middle columns primarily resist axial loading of the spine and the posterior column resists tensile forces.
An injury that involves at least two of the three columns is considered unstable.
The thoracolumbar junction of the spine is the transition from a rigid thoracic spine to a more mobile lumbar region. The thoracic spine is inherently stable due to being attached to ribs. T11 and T12 don’t have this rigid connection as the ribs are floating in nature.
Moreover, a change in the orientation of facet joints also allows for an increase in mobility.
Mechanism of Injury and Pathophysiology
The earlier Chance fracture was treated as a separate entity but modern textbooks describe it under flexion distraction injuries.
Mcfee et al in their mechanism of injury listed both the injuries and their mechanisms
- Chance fractures are horizontal avulsion injuries of the vertebral bodies caused by flexion around an axis anterior to the anterior longitudinal ligament. The entire vertebra is pulled apart by a strong tensile force due to a failure of bony elements.
- In flexion-distraction injuries, the flexion axis is posterior to the anterior longitudinal ligament. The anterior column fails in compression, whereas the middle and posterior columns fail in tension. This injury is unstable because the ligamentum flavum, interspinous ligaments, and supraspinous ligaments usually are disrupted.
The characteristic feature of a flexion-distraction injury is primarily a tensile failure [failing under tensio] of the posterior column. Injuries rarely occur through bone alone and are most commonly the result of bony and ligamentous failure.
Classically, hance fracture represents a pure bony injury extending from posterior to anterior, is a 3-column injury and in its true original sense, it is quite rare now.
Spine in flexion distraction injuries fail by compression of the anterior column due to flexion movement and failure of the middle and posterior column under tension due to destructive forces. Flexion-distraction injuries can be due to bony injuries [as in Chance fracture], ligamentous injuries, and a combination of both.
Bones often fracture before the ligaments because the ligaments have higher tensile force.
it was not until 1960 that an association was recognized between Chance fractures and lap seat belts. When the vehicle was stopped suddenly as in a collision, the lap seatbelt acted as restraint and became fulcrum at which the body moved forward resulting in Chance fracture, or seat belt fracture as it came to be known. Replacement of the lap belts with 3-point restrain belts as we see in modern vehicles has greatly reduced the occurrence of Chance fractures.
Most Chance fractures now result from falls or crush-type injuries where the thorax is acutely hyperflexed.
Cases of lumbar Chance fractures have been reported during plane landing and in a snowboarding accident.
Differential Diagnoses
- Burst fracture
- Compression fracture
- Distraction injury
- Causes distraction of vertebral bodies
- Shear injury
- Results in listhesis
Presentation of Chance Fracture
The patient presents with back pain after a significant trauma. There would be a history of flexion injury, typically the accidents where the one was wearing a belt.
There could be skin injuries on the abdomen where lap belt held the person. In case these injuries are present, person would require a surgical evaluation to rule out/confirm intraabdoinal injuries.
Neurological deficit is often not present. The presence of neurological deficit may be there when there is a retropulsion of fracture fragments of the posterior vertebral body cortex.
However, complete neurological examination should be done in every case of spine injury.
Imaging
X-rays
X-rays on lateral view typically show a wedge fracture of the vertebral body with a horizontal fracture through posterior elements. There might be a distraction of facet joints and spinous processes.
Other findings are
- Empty vertebral body sign
- AP view
- Due to fracture and displacement of posterior elements (the usual overlap shadows of posterior elements are not seen)
- Horizontal fractures of posterior elements
- Transverse processes, laminae, and articular processes
- Widening of
- interedicular distance – when there is a burst component
- Facet joints
- Intercostal spacing
- Interspinous spaces
CT
CT defines the fracture better than the x-ray and more accurately delineates it. In adults with thoracolumbar spine trauma, many physicians recommend CT scans instead of X-rays as initial imaging. CT also is the study of choice to assess intra-abdominal injuries.
MRI
It is better than CT for detecting soft tissue injuries like the ligaments, spinal cord, and intervertebral discs. It should be done if the patient has a neurological deficit.
Treatment of Chance Fracture
Conservative Treatment
Chance fractures may generally be managed by closed reduction and immobilization. For immobilization, a thoracolumbosacral orthosis (TLSO) or hyperextension cast may be used.
A rehabilitation program consisting of extension exercises can be instituted, and most individuals return to work within 6 months. A residual backache may be a problem for the first year postinjury.
Surgical Treatment
Surgery may be indicated in polytrauma patients or where the closed reduction is difficult. The surgery aims at alignment of the spine is of the utmost importance, followed by stabilization and arthrodesis. A rod-hook, hook-pedicle screw-rod, or pedicle screw-rod construct may be used for the fixation.
Complications
- Morbidity to abdominal injuries
- Progressive kyphotic deformity (esp in missed fracture)
- Residual low back pain
- Pressure sores from cast or brace
- Post-traumatic syringomyelia (fluid-filled cyst within the spinal cord)
- Nonunion of fracture
Prognosis
Residual low back pain is a significant issue in many patients though near anatomical reduction and healing is expected. It may occur a year after the injury, with long-term back pain being the major complaint.
References
- Bernstein MP, Mirvis SE, Shanmuganathan K. Chance-type fractures of the thoracolumbar spine: imaging analysis in 53 patients. AJR Am J Roentgenol. 2006 Oct. 187 (4):859-68. [Link].
- Tyroch AH, McGuire EL, McLean SF, Kozar RA, Gates KA, Kaups KL, et al. The association between Chance fractures and intra-abdominal injuries revisited: a multicenter review. Am Surg. 2005 May. 71 (5):434-8. [Link].
- Arkader A, Warner WC Jr, Tolo VT, Sponseller PD, Skaggs DL. Pediatric Chance fractures: a multicenter perspective. J Pediatr Orthop. 2011 Oct-Nov. 31 (7):741-4. [Link]
Image credit:http://www.e-radiography.net/radpath/f/chance_fracture.htm
