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Hyperextension Fracture-Dislocation of the Thoracic Spine Roy E. Erb, M.D.,* Steven B. Glassman, M.D.,* John R. Edwards, M.D., ~ and E. Paul Nance, Jr., M.D.*

Departments of *Radiology & Radiological Sciencesand f Orthopaedics and Rehabilitation, Vanderbilt University Medical Center, Nashville, Tennessee

Extension injuries of the thoracolumbar spine are rare and often are not included in classifications of thoracolumbar trauma. Hyperextension fracture-dislocation of the thoracolumbar spine is characterized radiographically by widening of the interverlebral disc space anteriorly. Additional features may include retrolisthesis, impaction fractures of the middle and posterior columns, and anterior inferior endplate corner fractures. Magnetic resonance imaging typically reveals rupture of the anterior longitudinal ligament and hemorrhage into the disc space, and it may demonstrate associated soft tissue or spinal cord injury. We present a case of hyperextension fracture-dislocation of the thoracic spine in a middle-aged female involved in a motor vehicle collision and discuss the salient features of this injury.

yperextension injuries of the tlmracolumbar spine are considered rare (1, 2). Most injuries o f the thoracolumbar spine occur secondary to hyperflexion or compression, often in combination with other forces, illcluding rotation, distraction, or translation. Among the reported series of twperextension fracture-dislocation of the thoracohmlbar spine, also known as "lmnberjack paraplegia" there has been considerable variability in the location of injury, neurologic complications, and treatment (1-4). In this report, we present a case o f a 1Wperextension fracture-dislocation in the lower thoracic spine in a middle-aged female secondary to a nmtor vehicle collision and discuss the incidence, mechanism of injury, radiographic manifestations, complications, and treatment of this injury.

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CASE REPORT A 43-year-old obese (90 kg) female involved in a motor vehicle collision as an unrestrained driver was transported to our Emergency Department after a prolonged extrication. Initially found unconscious at the s c e n e of" the acciCe Word~ Thoracic spine; Extension; Fracture-dislocation; Lumberjack paraplegia Address correspondence and reprint requests to: Roy E. Erb, M.I)., Departmerit of Radiology and Radiolo~cal Sciences, Vanderbilt University Medical Center, 21st Avenue South and Garland, Nashville, TN 37232-2675. 1070-3004/95/237-240/$3.00 Volume 2, Number 4 American Society of Emergency Radiology © 1995 Emergency Radiology .July/August 1995

dent, she arrived at our Emergency Department hypotensive but moving all four extremities. Endotracheal intubadon was performed for airway maintenance, and aggressive volmne resuscitation was institnted. The neurologic examination was linfited owing to severe right lower extremity injuries; however, she had normal strength in the upper extremities and left lower extrenfity and no evidence of sensory deficit. After a positive peritoneal lavage, the patient underwent emergent exploratory laparotomy. At snrgery, multiple splenic lacerations and hemoperitoneum were found, and splenectomy was performed. Radiographs of the thoracic spine obtained after emergent laparotomy demonstrated widening of the intervertebral disc space at T10/T11, greater anteriorly than posteriorly, impaction fractures of the inferior endplate o f T10 and superior endplate of T11 posteriorly, and avuMon of the anterior portion of the superior endplate of T11 (Fig. 1A and B). A computed tomographic (CT) scan of the lower thoracic spine, using a S o m a t o m Plus scanner (Siemens Medical Systems, Iselin, NJ) and 3-ram collimation at 3-ram intervals with sagittal reformation, revealed impaction fractures of the posterior half of the inferior endplate o f T 1 0 and superior endplate ofT11 (Fig. 2), and distraction of the intervertebral disc space at the same level. A magnetic resonance imaging (MILl) examination using a Somatom 1.5 T scanner (Siemens Medical Systems), and standard sagittal T1-weighted (TI'Z = 550 msec, TE = 15 msec), proton density; and T2-weighted (TFZ = 5000 msec, TE = 19 msec; TR. = 5000 msec, TE = 93 msec) Hyperextension Injury o f Thoracic Spine • 237

:igure 1~ :igure It

Figure 1. Plain radiographs of thoracic extension injury. Anteroposterior (A) and lateral (B) radiographs of the lower thoracic spine demonstrate anterior widening of the T1 O/T11 intervertebral disc space (arrows), endplate fractures with avulsion of the superior endplate of T11 {arrowheads), and no retrolisthesis.

images and axial Tl-weighted (TP. = 800 msec, TE = 15 msec) images revealed disruption of the anterior longitudinal ligament, widened anterior intervertebral disc space, hemorrhage in the intervertebral disc, and an intact posterior longitudinal ligament (Fig. 3). During hospitalization, the patient's nenrologic examination remained unremarkable. Follow-up radiographs o f the thoracic spine demonstrated normalization o f the T10/T11 disc space and no gross malalignment. Because of complications from the lower extremity injuries, the patient had a lengthy hospitalization requiring bed rest. Conservative therapy of the thoracic spine injury was elected, and the patient was discharged in a brace. The patient has no neurologic sequelae 7 months after the initial injury.

DISCUSSION Extension fracture-dislocation o f the thoracohmlbar spine is considered rare. Known as "lumberjack paraplegia" for its occurrence in timber workers struck by falling trees, extension fracture-dislocation is reported to account for less than 3% of all injuries to the thoracolumbar spine (1, 2). Owing to the rarity of this injurs; it often is not included 238 • H y p e r e x t e n s i o n Injury o f T h o r a c i c Spine

in classifications of thoracolumbar trauma. Mechanically, less flexion and extension occur in the thoracic spine than in the cervical and lumbar spine. Thoracic spine stability is aided by the support of the ribs and sternmn. Therefore, fractures of the ribs or sternum may render the thoracic spine more vulnerable to injury. In addition, patients with ankylosis of the spine from either ankylosing spondylitis or diffuse idiopathic skeletal hyperostosis are prone to extension injuries from relatively minor tramna (5-7). Two mechanisms are most likely responsible for hyperextension injuries of the thoracic spine. First, hyperextension may occur from direct impact anteriorly on tile upper thorax or neck, with the lower thoracic and lumbar spine fixed. In our patient, the mechanism for hyperextension may be related to the force of the steering colunm on the upper thorax, leading to extension rather than flexion, owing to the patient's large body habitus. The fact that the patient was found at the scene of the accident with one anHe resting on the dashboard before extrication supports the theory of hyperextension. Second, direct impact posteriorly on the thoracic spine may also cause hyperextension. Since this report, we have encountered one other extension fracture-dislocation occurring in the thoracic spine. In that Emergency Radiology • July/Augalst 1995

:igure

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Figure 2. CT scan of extension injury of the thoracic spine. CT scan of the injured level reveals a fracture through the anterior and middle columns (arrows) of the superior endplate of ]-11.

case, the patient was a pedestrian struck from behind by an automobile. In both of these cases, the fulcrum of the force is centered in the middle column of the spine (8). Tension forces on the anterior column result in disruption of the anterior longitudinal ligament and annulus fibrosus with resultant anterior disc space widening. Avulsion of the anterior inferior corner of the superior vertebral body or avulsion o f tile superior endplate o f the lower vertebral body may also occur. Compression forces centered posteriorly may result in fractures of the middle or posterior cohunns. Finally, retrolisthesis may accompany these findings and is a halhnark for extension injury. Plain radiographs of the thoracic spine in our patient demonstrated widening of the disc space anteriorly without retrolisthesis, as well as impaction fractures of the posterior half of the vertebral bodies above and below the injured disc level (Fig. 1A and B). In the patient reported here and in the patie,at with hyperextension fracture-dislocation of the thoracic spine that we encountered after the initial case report, the anterior superior endplate of the vertebral body below the level o f injury was avulsed. MILl typically demonstrates rupture of the anterior longitudinal ligament Emergency Radiology .July/August 1995

Figure 3. MR scan of a thoracic extension injury. T2-weighted sagittal MR scan of the thoracic spine demonstrates anterior widening of the T10/1-11 intervertebral disc space, rupture of the anterior longitudinal ligament, and hemorrhage in the intervertebral disc space (arrow).

and hemorrhage into the disc space, as seen in our case (Fig. 3). MRI may also reveal extra-axial fluid collections, soft tissite injury, or contusion/heulatoma of the spinal cord. O f the reported series of thoracolumbar extension fractures, there has been great variability in the site of injury and treatment (1-4). In Burke's (1) series o f four patients with thoracolumbar extension fractures, all i,ljuries occurred in the thoracic region and resulted in complete and irreversible paraplegia. DeOliveira (3) reported 10 cases of thoracolumbar spine injury secondary to lumbosacral shearing with secondary hyperextension--nine o f which occurred in the lumbar region. Seven of the eight survivors with lumbar injuries had complete recovery of neurologic function; the one patient with a thoracic injury and the other survivor with a hnnbar injury had residual neurologic deficit. Among the 12 patients reported by Denis and Hyperextension Injury of Thoracic Spine • 239

Burkus (2), 10 had fractures in the thoracic spine, and all except one o f the thoracic injuries resulted in complete and irreversible paraplegia. These series suggest that the severity and probability of irreversible neurologic sequelae are much greater with injuries in the thoracic spine than in the lumbar region, as would be expected with the location o f the spinal cord. Extension injuries in the lunlbar region generally have no clinically significant or reversible neurologic insult. Althougla the nettrologic examination o f the patient in our report was linfited by the presence o f severe lower extremity injuries, no neurologic deficit could be attributed to the level o f the thoracic injury. Likewise, the patient that we encountered after this report with an extension fractttre-dislocation of the spine at the T 9 / T I 0 level had n o nenrologic insult. It is likely that there is a spectrtnn o f extension injuries in the thoracolun~bar spine as seen in the cervical spine and that our patient suffered a less severe form o f tiffs injury. D o c u m e n t a t i o n o f injuries associated with extension fractures of the thoracolumbar spine has been poor, partly because several series were reported before the advent o f compttted tomography. Denis and Bttrkus (2) reported that associated injuries were rare, citing thoracic injuries in one patient and lower extrenfity fractures in another in their series of 12 patients. DeOliveira (3) noted initial signs o f abdonfinal injury in 40% of patients; however, the nature of these injuries was never deternfined. The patient in our report required laparotonty for splenic lacerations and suffered pelvic/hip fractures and lower extrenfity injuries. The splenic injury may have resuked from direct impaction or from shearing forces created by hyperextension. Treatment o f extension injuries o f the thoracoltutlbar spine varies (1, 2). In earlier series, patients without signifi-

240 • H y p e r e x t e n s i o n Inju D" o f Thoracic Spine

cant dislocation were treated conservatively with bed rest and plaster casting or bracing (1, 3, 4). M o r e recently, Denis and Burkus (2) performed posterior spinal fixation on 11 of 12 patients with extension injuries. Their experience suggests that best results are obtained with fixation utilizing Cotrel-Dubousset or Harrington rods combined with either a midline compression rod or interspinous wiring (2). Because o f the lack of significant retrolisthesis, normalization o f the injured level on plain radiographs, and the pauci W of symptoms related to the thoracic injury, our patient was treated conservatively with bed rest for 3 weeks and bracing for an additional 6 weeks.

~EFERENCE~

1. Burke DC. Hyperextension injuries of tile spine. J Bone Joint Surg Br 1971;53:3-12. 2. Denis F, Burkus JK. Shear fracture-dislocationsof the thoracic and lumbar spine associated with forceful hyperextension (lumberjack paraplegia). Spine 1992:17:156--61. 3. DeOliveira JC. A new t3"peof fracture-dislocation of the thoracolumbar spine.J Bone Joint Surg Am 1978;60:481-8. 4. Ferguson ILL, Allen BL Jr. A mechanisticclassificationof thoracolumbar spine fractures. Clin Orthop 1984;189:77-88. 5. Gehnan MI, Umber JS. Fractures of the thoracolumbar spine in ankylosingspondylitis.AJR Am J ILoentgenol 1978;130:485-91. 6. Hendrix R.W, Melany M, Miller F, Rogers LF. Fracture of the spine in patients with ankylosisdue to diffuseskeletal hyperostosis: clinical and imaging findings. AJR Am J l(oentgenol 1994; 162:899-904.

7. Young JWp,., Mirvis SE. Cervical spine trauma. In: Mirvis SE, Young JWl(, editors. Ima~ng in trauma and critical care. Baltimore: Williams& Wilkins, 1992;291-379. 8. Rogers LF. P,.adiologyof skeletal trauma. 2nd ed. New York: Churchill Livin~tone, 1992;439-592.

Emergency Radiology • July/August 1995