Case Report: Unusual Mechanism of Chance Fracture in an Adult Male

Manoj Todkar, MS, DNB, MRCS


April 25, 2005


Transverse fractures of the vertebral arch are also known as Chance fractures. In 1948, Chance[1] first described a transverse fracture of the vertebral arch that was produced by a hyperflexion injury of the spine. Since that time, the Chance fracture has proven to be an unusual lesion in adults, and is also very rarely described in pediatric patients.[2] This fracture is most frequently associated with injuries that are sustained while wearing lap-type seat belts.[3,4,5] This case reports a 30-year-old man who sustained a lumbar Chance fracture in a fall that resulted in sudden severe hyperflexion of the lumbar spine.

The Chance fracture consists of a horizontal splitting of the spine and the neural arch of vertebra, ending in an upward curve that usually reaches the upper surface of the vertebral body and produces no lateral displacement or rotation of the fracture fragments.[2,3] This fracture has been reported in children and can involve the first, second, third, and fourth lumbar vertebrae.[2,6,7] The mechanism of injury is hyperflexion of the spine over a fulcrum. Howland and colleagues[6] and Hubbard and coworkers[7] described a Chance-type fracture of the lumbar vertebrae that was produced by a lap-type seat belt acting as a fulcrum across the spine at the time of injury.

Smith and Kaufer[5] reported on a series of 20 patients with transverse fractures of the lumbar spine following injury incurred while wearing lap-type seat belts. They hypothesized that the mechanism of injury is one of sudden deceleration, which can occur as a result of an automobile crash or fall.

When hyperflexion of the spine occurs over a fulcrum such as a seat belt, the force is displaced anteriorly and lies at the point of contact between the fulcrum and the abdominal wall. This subjects all of the components of the spine to tension stress. The result is a disruption of the ligaments and posterior elements of spine or a transverse fracture of the posterior elements of the spine.

The same type of injury may occur as a result of a fall when the anterior abdominal wall comes into contact with some object, such as a tree limb or fence, which acts as a fulcrum and forces the body into acute flexion.[3] The development of a Chance fracture in a fall over an object that acts as a fulcrum has been theorized but not commonly reported in adults or children.[5]

In this instance, our patient fell from a height of 20 feet. There was no history of an object acting as a fulcrum involved in the fall. The mechanism of injury appears to have been the acute flexion of the spine, which occurred on impact with the ground, with the fracture as a failure of the bone in tension. The recognition of Chance fracture relies on a high index of suspicion when the history of injury and the clinical examination suggest a hyperflexion injury of the spine. Lateral radiographs of the spine will confirm the diagnosis. Treatment of the Chance fracture involves fusion for areas of the spine that are considered unstable as well as immobilization for stable injuries. Our patient did well after fusion of the spine.


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