Volume 6, Case 13
Abu N.G.A. Khan, MD
Maimonides Medical Center
Peter S. Dayan, MD
Columbia Presbyterian and Babies Hospital
Columbia College of Physicians and Surgeons
A 16 year old athletic female walked into the pediatric emergency department with a history of falling down 14 stairs, landing on her back. She complained solely of pain in the lower back. She denied any head trauma, loss of consciousness, vomiting, abdominal pain, or difficulty on urination. She had no past history of trauma to the back and had never been hospitalized.
Exam: She is alert and active but uncomfortable secondary to back pain. She is able to ambulate without any support. No neurologic deficit is noted on neurological examination.
Back examination: No focal tenderness over the lumbo-sacral spine noted. Mild to moderate tenderness over the right paraspinal region. No CVA tenderness, no abdominal tenderness. No bruises or echymoses.
She is felt to have a soft tissue injury of her back. Although there is a low suspicion for fracture, lumbo-sacral radiographs are ordered.
View radiographs.
Interpretation: The L2 vertebra shows some loss of height of the anterior vertebral body. The posterior vertebral line is intact. A compression deformity of L2 is suspected. A CT scan is ordered to examine the extent of injury.
View CT scan.
CT Scan: Multiple 5-mm continuous axial sections of the lumbo-sacral spine were obtained from the upper border of L1 to the level of S3 without intravenous contrast. Serial cuts of L2 are shown here (cuts 7, 8 and 9 shown left, right and bottom, respectively) There is a wedge compression deformity of L2 vertebral body with preservation of the disc spaces above and below this level. There is minimal retropulsion of the L2 body not causing any significant compression of the thecal sac. The superior end plate and part of the body appear fragmented as seen on image cuts 7, 8 and 9. There is minimal prevertebral soft tissue prominence. The bony spinal canal is normal in size and configuration. No significant posterior bulging or herniation of the disc is present.
Hospital Course: She was hospitalized under the neurosurgery service for observation and discharged home in two days with a brace.
Discussion
Thoraco-lumbar fractures are a major cause of disability (1). Ninety percent of all spinal fractures are in the thoraco-lumbar region. Fractures at the thoraco-lumbar junction have a significant incidence of neurologic deficit of up to 40% in one series (2).
Several factors contribute to thoraco-lumbar vulnerability.
a. In the lumbar spine , there are no ribs to provide additional stability as in the thoracic region (3).
b. The alignment of the spine changes from a kyphotic curvature in the thorax to a lordotic alignment in the lumbar spine (4).
c. Lumbar spinal segments are more mobile than thoracic segments. The mobility is due in part to the changing orientation of the facet joints. The coronal orientation of the facets in thoracic region is more stable then the oblique orientation of the lumbar region.
The Three Column Concept
The management and outcome of lumbosacral spine injuries largely depend upon the stability of the spinal column. There are different models to describe the stability following an injury. The three-column concept described by Denis (5,6) in 1983 is the most accepted.
View three-column diagram: Fig1
Fig.1: Lateral View of Lumbo-sacral Vertebrae
1. The anterior column consists of the anterior longitudinal ligament and the anterior part of the vertebral body.
2. The middle column extends from the middle portion of the vertebral body to the posterior aspect of the vertebral body and includes the posterior longitudinal ligament.
3. The posterior column includes all bony and ligamentous structures posterior to the posterior longitudinal ligament and includes the pedicles, facets, spinous processes and all associated ligaments.
Fractures involving only the anterior columns are considered stable, while fractures that involve the middle or all three columns are considered unstable.
Types of Thoraco-lumbar Fractures
Thoraco-lumbar fractures and dislocations have been classified by different investigators (1,4). However, no one classification system is inclusive of all injury patterns. Currently the classification described by McAfee, et al. (7), is the most widely recognized. Their TLS injury scheme consists of five distinctive injury patterns: wedge compression fractures, burst fractures, Chance fractures, flexion-distraction injuries and translational injuries (see Fig 2). In recent years, the increased use of magnetic resonance imaging (MRI) and helical CT scanning has led to improvements in classifying TLS injuries.
View TLS injury types: Fig2
Fig. 2: Types of thoraco-lumbar fractures
1. Wedge compression fractures are the most common type of lumbar fracture (4). They occur during hyperflexion and axial loading (as was likely in our case). The vertebral body fails under a compressive load and its anterior portion becomes compressed while the middle column remains intact. This fracture is rarely associated with neural injury unless multiple adjacent vertebral bodies are compressed. Radiographically, the wedge deformity is best appreciated on the lateral view. A CT scan is used to confirm that the posterior vertebral body, pedicles and lamina are intact.
2. A burst fracture of the spine was first described by Holdsworth (8) in 1963 and redefined by Denis (6) in 1983 as being a fracture of the anterior and middle columns of the spine with or without an associated posterior column fracture. Both a compression fracture and burst fracture occur during hyperflexion and axial loading of a vertebra. With a burst fracture, however, there is compression of the vertebra and intervertebral disk in such a fashion that the compressed disk adjacent to the affected vertebra herniates into the vertebral body. As a result, the vertebra fractures outward with retropulsion of bone fragment into the spinal canal and an increase in interpeduncular distance (distance between the pedicles). Because all burst fractures have the potential for severe neurologic sequelae, they should be considered unstable during the initial emergency department evaluation. Unstable burst fractures are treated with surgical stabilization to improve long-term alignment. For stable fractures, the neurologic outcome may be similar for surgically and non-surgically treated patients (1,4).
3. A Chance fracture is commonly associated with lap seat belt use in high-speed motor vehicle crashes (9). A Chance fracture is a horizontal vertebral injury that results from flexion about an axis that is anterior to the anterior spinal longitudinal ligament. This vector of force results in the horizontal disruption of the spinous process, lamina, transverse processes, pedicles and the vertebral body. A lateral radiograph best illustrates the split in the posterior arch and vertebral body. More subtle signs include an increase in adjacent spinous process distancec above and below the injury and an increase in the height of the posterior vertebral body. An anterior-posterior radiograph may demonstrate the split in the transverse processes. Since the fracture runs in an axial plane, a routine axial CT scan may miss a Chance fracture. It is important to perform the reconstruction in the sagital plane to detect the fracture and any malalignment due to ligamentous injury.
4. A flexion distraction injury is one in which the axis of flexion is posterior to the anterior spinal longitudinal ligament. There is compressive failure of the anterior column and destructive forces placed on the middle and posterior columns lead to a tear of the posterior longitudinal ligament. Typically, these injuries involve both ligamentous and bony structures and can extend over more than one vertebral level. These injuries are considered unstable because the middle column and often the posterior column are disrupted. Radiographic findings include anterior impaction with compression fracture of the vertebral body and posterior distraction with fanning of the spinous processes.
5. Translational injuries are associated with shearing forces that disrupt all three columns. The shearing forces are most often directed posteriorly to anteriorly but may also be directed anteriorly to posteriorly. Since the ligament of the spinal canal is affected, these injuries are always unstable and are associated with a very high incidence of neurologic deficit (6). Lateral radiographs demonstrate anterior translation of the upper vertebrae with respect to the lower vertebrae. On the AP radiograph, the interspinous distance at the affected level is widened and there may or may not be a rotational malalingment of the vertebra. CT scan may show "naked facets" or a double vertebra, if the dislocation is severe.
Thoraco-lumbar spine injuries are common and often result in serous morbidity. Forty-seven percent of patients with spine trauma and 64% with spinal cord injuries have concomitant injuries elsewhere (10). In the setting of multiple trauma, in which most TLS injuries occur, strict spinal cord injury precautions must be observed until injury has been ruled out. A working knowledge of spinal column anatomy is crucial to evaluate and manage these injuries. Application of Denis' three-column model to assess spinal stability and McAfee's classification of fracture/dislocation facilitate management decisions.
References