Wedge Compression Fractures
This is the most common fracture in the thoracic and lumbar spine. These fractures are due to flexion and distraction, causing failure of the anterior column of the spine (Fig. 10–2). Because the middle and posterior columns remain intact, this is a stable injury without risk of causing spinal cord injury. It is classified here with unstable fractures because other mechanically unstable injuries (i.e., burst fractures) may mimic the wedge compression fracture.10
An anterior wedge compression fracture is a stable fracture because it involves only the anterior column.
In awake patients, pain and tenderness are present at the site of the fracture, most commonly the midthoracic or upper lumbar region. The injury may occur after any type of trauma but is especially common in patients with osteoporosis, who may sustain a wedge compression fracture after an injury as trivial as a sneeze. They are also associated with the muscle contraction that comes with an epileptic seizure and have been reported in patients riding in vehicles that have gone over a speed bump.19,20 Neurologic injury is not associated with this fracture because the middle and posterior columns of the spine remain intact.
This fracture is best seen on the lateral radiograph, where the vertebral body takes on a wedge shape (Fig. 10–3). The vertebral body is compressed anteriorly and the posterior cortex of the vertebral body is normal. CT scan is recommended whenever the integrity of the posterior vertebral body and posterior column structures are questionable, as plain radiographs do not adequately evaluate the posterior vertebral body cortex.21 The patient should be considered to have an unstable fracture until it is clear that the anterior vertebral body is all that is involved.
Anterior wedge compression fracture of T12.
The treatment of a simple wedge compression fracture is pain relief and early mobilization with increasing activity as the pain subsides. Physical therapy may be appropriate and activity is rarely restricted by 3 to 4 months following the injury.
Long-term instability of the spine can occur with severe compression fractures (>50% loss of the body height) or when multiple adjacent wedge fractures are present.
A burst fracture is a comminuted fracture of the vertebral body due to axial compression (Fig. 10–4). It is an unstable fracture because the anterior and middle spinal columns fail. In some cases, the posterior column is disrupted as well. Burst fracture is distinguished from the wedge compression fracture because the posterior vertebral body cortex is fractured. Posterior vertebral body fractures provide an additional risk to the spinal cord because frequently there is retropulsion of bony fragments into the spinal canal (Fig. 10–5).
Sagittal view of a burst fracture. This comminuted fracture is due to axial compression.
Transverse view of a burst fracture. There is retropulsion of bony fragments into the spinal canal.
Burst fractures are most common from a fall, but motor vehicle collisions also account for a high number of these injuries. They have been reported after an atraumatic seizure.22 The majority of burst fractures occur in the T12 or L3 region. In 10% of cases, there is more than one burst fracture.23 They account for approximately 15% of vertebral fractures.24 Examination of the spine reveals tenderness at the level of the fracture, but the interspinous distance is unchanged. Neurologic deficits are present in approximately half of patients. Complete loss of motor function is present in one-third of patients.
On plain radiographs, there is loss of height of both the anterior and posterior cortex of the vertebral body. These findings are most apparent on the lateral radiographic view. The spine remains well aligned. Posterior element fractures are present in two-thirds of cases, although they are difficult to visualize on plain films.
The loss of height of the posterior cortex of the vertebral body is often difficult to appreciate on plain films, causing this injury to be misdiagnosed as a wedge fracture. In one study, plain films improperly misdiagnosed burst fractures 25% of the time.10
CT details the degree of retropulsion and the presence of fractures in the posterior column. CT also impacts the treatment plan.25 Patients with a 50% reduction in the midsagittal diameter of the spinal canal are at an increased risk of progressive neurologic dysfunction.
The patient should be managed with strict spinal immobilization, and consultation with an orthopedic or neurosurgical spine specialist should be obtained. Frequent neurologic reevaluations are warranted to detect changes in status.
The Chance fracture, first described by GQ Chance in 1948, occurs after flexion of the spinal column about an axis that is anterior to the anterior longitudinal ligament. It involves a horizontal splitting of the vertebra through all three columns and is therefore an unstable injury (Fig. 10–6). Injury starts in the posterior elements of the spinous process or lamina and extends anteriorly to the pedicles and vertebral body. Because there are little translational or rotational forces, displacement is unusual.
This injury was most common in the era of the lap-only seatbelt, where sudden deceleration forces caused severe hyperflexion and distraction of the spine. Today, most Chance fractures occur after falls or crush injuries. Tenderness is present over the involved vertebrae, most commonly T12, L1, or L2. Chance fractures are associated with significant intra-abdominal injuries, with an incidence approaching 50%.
On the anteroposterior view, disruption of the pedicles, loss of vertebral height, or a transverse process fracture may be noted. The lateral view demonstrates fractures through the spinous process, laminae, or pedicles. More subtle findings include an increase in the distance of adjacent spinous processes or an increase in the height of the posterior vertebral body.
A CT scan should be ordered to determine the extent of injury, the involvement of the spinal canal, and to diagnose intra-abdominal injury. Because the disruption is oriented on a horizontal plane, this injury could be missed on CT if axial images are not supplemented by sagittal reformatted images.
These injuries are unstable. The spine should be kept immobilized and consultation with an orthopedic or neurosurgical spine specialist should be obtained.
This injury has a similar mechanism to the Chance fracture, but the axis of flexion is posterior to the anterior longitudinal ligament. The anterior column fails due to a compressive mechanism and the middle and posterior columns are disrupted by a distraction force (Fig. 10–7). Radiographic findings include anterior impaction of the vertebral body and posterior distraction with fanning of the spinous processes. Like the Chance fracture, these are unstable injuries and require the maintenance of spinal immobilization. Consultation with a spine specialist should be obtained.
Translational injuries are fracture dislocations that occur after a shearing mechanism. They are rare, accounting for less than 2% of thoracic-lumbar-sacral (TLS) spine fractures. All three columns fail and the alignment of the spinal canal is affected in the transverse plane (Fig. 10–8). This is an unstable injury and there is almost always an associated neurologic injury. Most commonly, the shear force is directed in a posterior to anterior direction and is the result of direct trauma to the back.
Translational injury due to a shearing force.
Plain radiographs demonstrate this injury. Several variations may be seen. When translational injuries occur in the thoracic region, the lateral radiograph will demonstrate displacement of the superior vertebral body anteriorly. The vertebral bodies remain essentially intact, but the spinous process of the superior vertebra and the articular processes of the inferior segment are fractured. In the lumbar region, the direction of displacement is opposite, with the superior vertebra displaced in a more posterior direction. The dislocation is somewhat more subtle with no more than one-third of the width of the vertebral body displaced. The inferior portion of the superior vertebral body may be avulsed and, frequently, there is facet joint or pedicle fracture. CT scan is useful for giving more detailed information on the extent of bony injury.
These injuries are unstable. The spine should be kept immobilized and consultation with an orthopedic or neurosurgical spine specialist should be obtained. Because of the almost universal occurrence of spinal cord injury, an early decision about the use of steroids should be made. Refer to Chapter 9 for a further discussion of steroids in acute traumatic spinal cord injury.