Chance Fracture

The usual location for Chance fractures is at the thoracolumbar junction (T10-L2) in adults or the midlumbar spine in the pediatric age group. The fracture lines are found to propagate from the spinous process posteriorly through the lamina, pedicles, and vertebral body anteriorly.

Conceptually, the thoracolumbar spine may be visualized as comprising three columns, as described by Denis.[13] The anterior column is represented by the anterior half of the vertebral body, disk, and anterior longitudinal ligament. The middle column consists of the posterior half of the vertebral body, its associated disk, and posterior longitudinal ligament. The posterior column includes the pedicles, facet joints, lamina, and spinous and transverse processes, as well as the ligamentous complex, including the ligamentum flavum.

The anterior and middle columns both are primarily involved in resisting axial loading of the spine. The added importance of the middle column relates to its proximity to the spinal canal and neural elements. Displacement of the middle column can result in neurologic compression and deficits. The posterior column primarily resists tensile forces, such as those encountered in flexion-distraction injuries. In Chance fractures, the bony elements involved fail, with the ligamentous components remaining intact. (See the image below.)

The thoracolumbar spinal junction represents a transitional area from the rigid thoracic spine to the more mobile lumbar region. The thoracic spine's intrinsic stability is a result of the ribs and their articulation with the spine, the smaller disk spaces, and the frontal orientation of its facet joints. As the lower two thoracic vertebrae (T11-12) lose the anterior rib articulations (floating ribs), the facet joints also change orientation to become more oblique or sagittal, allowing an increase in mobility.[14]

Flexion-distraction forces are responsible for the Chance fracture. Usually related to lap seatbelt wear, this mechanism can result in complete ligamentous injury or a combination of bony, ligament, and disk involvement. (See the image below.)

The most common history is that of a back-seat passenger who was involved in a motor vehicle accident while restrained by a lap seatbelt[4] or that of a person who fell from a height. Lumbar Chance fracture from lap seatbelt injury sustained during an airplane landing incident has been reported.[15]

Hu and Lieberman reported a case in which a 67-year-old woman with osteoporosis and thoracic kyphosis experienced a proximal vertebral body Chance fracture after pedicle screw instrumentation and fusion.[16]  Pitta et al described a case in which a patient with ankylosing spondylitis experienced a lumbar Chance fracture after undergoing total hip arthroplasty via the direct anterior approach.[17]

Fewer than 10% of fractures involving the lumbar spine are a result of flexion-distraction forces. These injuries tend to occur between T12 and L4, with the highest incidence at L2.

With proper recognition and early management of a Chance fracture, near-anatomic reduction and healing can be expected. After 3 months of immobilization in a cast or thoracolumbosacral orthosis (TLSO), a rehabilitation exercise program with emphasis on the extensor muscles of the thoracolumbar spine can assist the return to preinjury activity levels. The ultimate result may not be determined for a year after the injury, with long-term back pain being the major complaint.[18]

The patient has back pain and, on clinical examination, may have a lap seatbelt abrasion across the abdomen. It is vital to be mindful of the high incidence of associated intra-abdominal injuries, such as liver or spleen lacerations, bowel rupture, or pancreatic injury. Therefore, a thorough examination of the abdomen at the initial evaluation is of the utmost importance.

It is wise to ask for a general surgical consultation at this time to ensure that an occult bowel or other viscus injury is not overlooked. Although neurologic findings are uncommon with this injury, it is nonetheless important to perform a thorough neurologic examination that includes motor, sensory, and reflex evaluation. A rectal and bladder examination should also be performed, including evaluation of the residual urine after the patient has voided. Palpation of the thoracolumbar spine is performed to assess points of maximum tenderness and palpable defects.

Radiographic assessment should begin with anteroposterior (AP) and lateral radiographs of the thoracolumbar spine. A demonstrable fracture line may be detected extending through the spinous process, pedicles, and vertebral body. In general, the diagnosis may be determined on the basis of plain radiographs, but occasionally, computed tomography (CT) scans with frontal and sagittal reconstructions are beneficial.

If a Chance fracture goes unrecognized, it may result in progressive kyphosis with ensuing pain and deformity.[19] Associated intra-abdominal injuries can result in increased morbidity and mortality; children with traumatic Chance fractures are more likely to have these associated injuries than adults with such fractures are.[20] Ureteropelvic junction disruption associated with Chance fracture has been reported.[21] Chance fracture leading to traumatic hemothorax has been described.[22]

The laboratory workup, in general, is the same as it would be for any trauma patient. It should include a baseline complete blood count (CBC), a urinalysis, and an appropriate chemistry profile as indicated. Because of the high incidence of associated intra-abdominal pathology, close attention should be paid to liver function test (LFT) results.

The radiographic workup[23] initially should include anteroposterior (AP) and lateral views of the thoracolumbar junction. The posterior elements should be observed clearly to identify the fracture line and its propagation. (See the image below.)

Computed tomography (CT) may be necessary to clearly delineate the entire bony nature of this injury; sagittal and coronal reconstructions are helpful.[24]

As a rule, magnetic resonance imaging (MRI) is unhelpful, except in individuals with unexplained neurologic deficits, which are uncommon with this injury. The scan may demonstrate a contusion of the conus or compression of the cauda equina, which may correlate with the clinical examination.[25]

Although Chance fractures may generally be managed by means of closed reduction and immobilization in a thoracolumbosacral orthosis (TLSO) or hyperextension cast, surgery may be indicated in some cases. Exogenous obesity may be a relative contraindication for the usual nonoperative management of Chance fractures because it may render bracing difficult. In these instances, as well as in cases of multiple trauma, an operative approach may be indicated to stabilize these injuries.

Chance fractures can generally be reduced by placing the patient on a Risser table with hyperextension applied to the thoracolumbar junction. A fiberglass or plaster cast is then applied. Alternatively, a mold may be taken and a TLSO made for stabilization. Patient selection is important to ensure compliance with orthosis use.

Once the flexion-distraction injury through the bony elements is approximated and the kyphosis is reduced through extension of the thoracolumbar spine, the patient is maintained in the TLSO or hyperextension cast for 2-3 months. After immobilization, an upright lateral radiograph should be obtained to assess any residual deformity. The union rate is high and the results are good with closed management.

A case report by Park et al described successful treatment of an unstable bony Chance fracture with teriparatide and an orthosis in a patient with diffuse idiopathic skeletal hyperostosis.[26]

A rehabilitation program consisting of extension exercises can be instituted, and most individuals return to work within 6 months. Residual backache may be a problem for the first year after the injury.

If immobilization is impractical (eg, because of a large body habitus) or the patient has polytrauma, surgical management may be indicated.

A posterior approach to reconstruct the posterior tension band is preferred. This may be accomplished with either a rod-hook, a hook–pedicle screw–rod, or a pedicle screw–rod construct, depending on the individual patient's anatomy and the location of the injury. A similar operative approach may be used with ligamentous variants. Decompression usually is not a result of residual compression in this injury; realignment of the spine is of the utmost importance, followed by stabilization and arthrodesis.

With the advent of percutaneous and minimally invasive techniques for pedicle-screw insertion, these devices may be applied more easily in multiple-trauma patients and others in whom closed management would be impractical.[27, 28]  In a meta-analysis focused on open versus minimally invasive fixation for traumatic thoracolumbar fractures, McAnany et al found minimally invasive fixation to have advantages with respect to blood loss and operating time, though there were no significant differences between the two approaches with regard to vertebral body height, kyphosis angle, or visual analogue scale (VAS) score.[29]

Le et al emphasized the importance of defining the pattern of injury in the pediatric population to determine appropriate treatment.[30] Arkader et al concluded that surgical treatment in children provides the best results.[31]

Operative details

If operative intervention is selected, computed tomography (CT) detailing the pedicle anatomy is helpful in selecting the appropriate fixation device. If a neurologic injury is present, magnetic resonance imaging (MRI) may be helpful as well.

Because a Chance fracture involves a flexion-distraction mechanism, placing the patient on rolls providing an extension moment or on the Jackson table prone frame aids in the reduction of this injury.

In a midline approach to the thoracolumbar junction, a level above and a level below the affected area should be dissected. Once the dissection has extended down to the tip of the spinous processes, subperiosteal dissection with Cobb elevators is carried out to the facet joints bilaterally. Further dissection around the facet joints to the transverse processes is performed to complete the exposure necessary for instrumentation.

Surgical gauze for packing the lateral gutters is invaluable in assisting with hemostasis. At each level, troublesome bleeding can be encountered from segmental vessels around the facets and pars interarticularis.

Instrumentation may involve as little as one level above and below the injured site, if pedicle-screw fixation is possible. However, standard hook fixation may be used to incorporate two levels above and one or two levels below the zone of injury. A hybrid construct consisting of hooks above and pedicle screws below is also an option.

Closure in layers is performed after a standard posterior lateral arthrodesis is performed. Meticulous decortication of the transverse processes, pars, and lateral aspect of the facet joints should be completed before application of autologous bone grafting.

With optimal surgical fixation, early mobilization should be possible. The usual postoperative concerns of bowel and bladder function and advancing diet should be addressed carefully and individually. Deep vein thrombosis prophylaxis can usually be provided by using compression hose and intermittent dynamic compressive devices, such as a foot pump or Venodyne boot. Other means of anticoagulation may be employed on a case-by-case basis, with care taken to weigh the risks of such therapy against its benefits.

The most common complications are residual kyphosis and chronic mechanical back pain. Pressure injuries under a cast can be avoided with proper padding and cast application and with frequent turning of the patient. Such injuries can also be avoided by fostering early mobilization.[32]

Arthrodesis usually is complete by 6 months, if not sooner, in younger patients. A rehabilitation program can be instituted as healing progresses and should include a walking routine and back exercises for mobilization and strengthening.

Follow-up radiographs should be obtained at monthly intervals to ensure progressive healing and maintenance of spinal alignment.