Background
The unique anatomy of the thoracolumbar junction predisposes this level of the spinal column to dislocation fractures. As the thoracic spine loses its structural rigidity with floating ribs at T11 and T12, the orientation of the facet joints also changes from a more frontal projection to oblique and then sagittal in the upper lumbar spine. These spinal dislocation fractures result from violent traumatic injuries and are associated with a very high incidence of neurologic deficit resulting from the translation of the spine.
Approximately 90% of dislocations above T10 result in complete paraplegia, and 60% of dislocations below T10 result in complete neurologic deficit. The spinal cord ends at the L1-2 level in most adults; the cauda equina represents the terminal nerve roots of the lumbosacral spine present below this site. The prognosis for a pure nerve-root injury is much better than for an actual spinal-cord injury. In some of these injuries, spinal-cord injury and nerve-root damage are combined.
Of the injuries affecting the thoracolumbar spine, dislocation fractures are the most unstable, secondary to the soft-tissue and bony disruption resulting from the high-energy mechanics of injury. This injury is associated with the highest incidence of neurologic deficits and chest and abdominal trauma. Involvement of all three spinal columns (see Pathophysiology) generally necessitates operative intervention to stabilize the spine and optimize neurologic recovery and patient rehabilitation.
Spinal injuries with resulting paralysis have been recognized since the writings of the Edwin Smith papyrus as "an ailment not to be treated." [1, 2] Various authors proposed postural reduction on frames with prolonged bedrest as a means of achieving spinal stability. Nicoll favored early return of function regardless of nonanatomic alignment of the spine. [3]
None of these early series provided techniques for reducing and stabilizing the thoracolumbar spine; however, such techniques are available to contemporary surgeons. With the advent and use of Harrington rod instrumentation, a debate arose about nonoperative versus operative care for these highly unstable injuries. Fixation devices have been devised that allow fewer segments to be incorporated in the surgical construct. Whereas the posterior approach is used most often, anterior procedures also may be important in reconstruction after these devastating injuries. The surgical approach allows earlier mobilization, minimizing medical complications and preventing progressive deformity.
Anatomy
The thoracolumbar junction represents a region of the spine in which the relatively rigid thoracic area transitions to the more mobile lumbar spine, on the basis of anatomic changes in the vertebral body, facet joints, and adjacent ribs.
The anterior column of the spine in this area consists of the following:
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Vertebral bodies
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Superior and inferior disks
The vertebral bodies increase in size in both anteroposterior (AP) and medial and lateral planes. The disk heights also increase, allowing more motion.
The posterior column, which acts as a tension band, consists of the following:
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Pedicles
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Facet joints
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Lamina
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Transverse and spinous processes
Ligamentous structures add stability and are most effective in resisting loads in the planes in which the fibers run. They tighten under tension and buckle under compression. These include the following:
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Anteriorly - Anterior and posterior longitudinal ligaments (which attach to the vertebral bodies and disks)
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Posteriorly - Intertransverse, capsular, interspinous, and supraspinous ligaments
The ligamentum flavum attaches to the anterior-inferior border of the laminae above and the posterior-superior border of the laminae below. These ligaments tend to be thicker in the thoracic region and have a midline cleavage plane throughout. Because of the large amount of elastin present, this tissue is the most elastic tissue in the spine.
The orientation of the facet joints changes from the frontal plane in the thoracic spine to the more oblique plane at the thoracolumbar junction.
Pathophysiology
Dislocation fractures of the thoracolumbar junction involve disruption of all three spinal columns resulting from a combination of mechanisms, including the following:
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Compression
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Tension
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Rotation
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Shear injury
Although the shear component may occur from anterior to posterior, it more frequently occurs from posterior to anterior with sequential failure of the posterior ligamentous complex, fracture of the lamina, buttressing of the facet joints, and, finally, anterior vertebral body compression. The rotational insults are recognized by the fractures of the transverse processes and adjacent lower ribs. The fracture through the lamina frequently results in dural tears and entrapped nerve roots. This may have a bearing on the initial surgical approach to reconstruction of the spine. [4, 5, 6]
Etiology
The most frequent causes of spinal-column injuries are motor vehicle accidents (45%), falls from heights (20%), sports-related injuries (15%), [7] and acts of violence (15%). [8] A large-scale study of spinal trauma in China that included more than 82,000 patients identified a specific cause in more than 64,000 patients. Motor vehicle accidents were the leading cause (33.51%), followed by high falls (31.25%) and trivial falls (23.23%). [9]
Epidemiology
Spinal-cord injury continues to be a significant source of morbidity and mortality among the young adult population in this country. Each year, approximately 10,000 new patients with spinal-cord injuries are added to the 180,000-200,000 individuals already living with spinal-cord injuries.
Prognosis
Incomplete injuries at the level of the cauda equina tend to have a more favorable recovery rate than mixed conus and cauda equina lesions or lower spinal-cord injury. According to a multicenter study reported by Gertzbein, the prognosis for bowel and bladder recovery appears to be improved with anterior decompression. [10] Complete neurologic deficits continue to have a grim prospect for recovery, and emphasis on rehabilitation and incorporation of the individual with paraplegia into society is aided by regional spinal-cord injury centers.
Long-term management of bowel and bladder dysfunction should include the use of stool softeners, suppositories, a high-fiber diet, and intermittent urinary catheterizations to decrease the residual urine volume. Despite these efforts, chronic urinary tract infections continue to plague patients with paraplegia.
The ultimate functional outcome may be affected significantly by the patient's age, body habitus, general medical condition, and cognitive and motivational factors. Depression is quite frequent in this patient population and can adversely affect the recovery and rehabilitative process. A multidisciplinary approach, including physical and occupational therapists as well as psychological support, is desirable.
With motor grade strength improvement greater than 3 (antigravity level), ambulation may be possible with the use of adjunctive orthoses. This may result in extreme energy requirements and may interfere with the performance of upper-extremity activities while standing. Simplification of daily routines can help in conserving energy and improving the lifestyles of patients with spinal injuries.
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Flexion distraction injury with facet dislocation.
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Fracture dislocation.
