Thoracolumbar trauma

Introduction

Trauma to the lumbar or thoracic spine remains a clinical challenge from a diagnostic and management perspective. In general, trauma to this region can be subdivided into low-energy and high-energy.

• Low-energy trauma is fairly typically seen in older patients with poor bone quality and will manifest as compression fractures.
• High-energy trauma can be seen in all age groups and is associated with motor vehicle accidents (MVAs) and polytrauma.¹

Anatomy

The bony structure of the thoracic and lumbar spine involves the 12 vertebral bodies of the thoracic spine and 5 vertebral bodies of the lumbar spine. The lumbar spine has normal lordotic curvature, with a corresponding kyphotic curvature of the thoracic spine. The thoracic vertebrae are unique in that the bodies have a superior and inferior costal facet, allowing articulation with the ribs. This connection to the rib cage provides significant stability and rigidity to the thoracic spine, in contrast to the lumbar vertebrae, which do not articulate with the ribs and therefore have significant range of motion.

A thoracic or lumbar vertebra consists of a body, which forms the structural support for the axial skeleton, and a vertebral arch, which encloses and protects the spinal cord. The arch consists of the pedicle, which projects posteriorly from the body, the lamina, which projects toward midline from the pedicle and completes the arch. The transverse process projects laterally from the transition of the pedicle to the lamina, and the spinous process projects posteriorly from the meeting of the two laminae. Additionally, there are superior and inferior articular facets projecting from the junction of lamina and pedicle that prevent each body from translating over one another. In between each vertebra is an intervertebral disc that functions as a shock absorber as the spine compresses.

Biomechanics

In addition to the bony structures, there are two important ligaments: the anterior longitudinal ligament (ALL) and the posterior longitudinal ligament (PLL). These ligaments act to tether each spinal segment together and prevent dislocation from one another.

The more stout and important to stability is the PLL, which has been described as a tension band to the bony column of the vertebrae. The PLL is an element of the important posterior ligamentous complex (PCL), which also consists of the ligamentum flavum, interspinous ligament, and facet joint capsule. The integrity of these posterior ligamentous structures has become the focus of much of the debate with regard to management of spine trauma.

The relative rigidity of the thoracic spine compared to the flexibility of the lumbar spine allows for a significant amount of stress across the thoraco-lumbar junction and predisposes these vertebrae to fracture and dislocation.²

Clinical Presentation

Patients typically present to the emergency department following a significant mechanism of injury. These patients may present with back pain or neurologic symptoms; however, in the polytrauma patient, thoracolumbar trauma may be masked by other injuries.

Certain injury patterns should make the clinician suspicious of lumbar spine trauma, such as calcaneus fractures following a fall. The association of these injuries is well described, and they have been termed lover’s fracture or Don Juan fractures.³

Regardless of the mechanism, recognition of a fracture or dislocation in the thorax or lumbar spine warrants a full neurologic exam. When neurologic injury is detected, a rectal exam is mandatory, which not only allows evaluation of perianal sensation and tone, but also the presence of the bulbocavernosus reflex. Presence or absence of this reflex determines if the body is in spinal shock and can help guide prognosis of neurologic recovery.¹

In the case of the osteoporotic patient, a low-energy mechanism may be reported, and this patient may present not to an emergency room, but to the primary care setting complaining of back pain. Spine fractures with a low-energy mechanism in young patients or patients with good bone stock should raise concern for spinal malignancy.

Imaging and Diagnostic Studies

Initial imaging should start with plain radiographs; many thoracic spine injuries can be detected from chest x-rays. Dedicated AP and lateral views of the lumbar spine are warranted for any patient with spine tenderness or deformity noted on physical exam. Assessment of vertebral height, alignment, and orientation can be determined from plain films.

In today’s modern level 1 trauma centers, computed tomography (CT) scan is readily available and can provide additional information regarding morphology of fracture and extent of injury. When neurologic injury is evident or suspected, magnetic resonance imaging (MRI) is the tool of choice for determining where the nerve root or spinal cord is being compressed.

Classification

Several classification systems have been developed to evaluate injury to the thoracolumbar spine. The classic is the Denis classification proposed in the early 1980s. This classification divides the spinal column into three separate columns:

• The anterior column involves the anterior two thirds of the vertebral body.
• The middle column is the posterior one third of the body and the posterior longitudinal ligament.
• The posterior column consists of the neural arch, facet joints, and muscular insertions.

Fractures that involve purely the anterior columns are compression fractures, while fractures that involve the anterior and middle column are burst fractures.⁴ Retropulsion into the canal indicates disruption of the PLL and instability. Injury to the posterior column is indicative of a flexion-distraction injury.

The Denis classification has limitations when it comes to which fractures need surgical fixation, as multiple studies have demonstrated successful treatment of burst fractures nonoperativly.⁵

The Spine Trauma Study Group devised the Thoracolumbar Injury Classification System (TLICS) to improve interobserver reliability, guide treatment, and incorporate neurologic injury into the system, utilizes three categories to classify the injury and guide treatment. In general, a TLICS score over 4 needs to be surgically managed (Table 1).⁶

Table 1. Thoracolumbar Injury Classification System

The TLICS system demonstrates better interobserver reliability when compared to the Denis classification for thoracolumbar trauma.⁷ The inclusion of neurologic injury in the classification allows injuries that normally would be managed conservatively to meet operative criteria if presenting with neurologic deficit.

Treatment

Conservative Treatment

The decision to treat a fracture of the thoracolumbar spine conservatively is based on stability of the fracture and neurologic status. Compression or burst fractures without neurologic compromise may be managed using bracing, activity modification, and serial radiograph evaluation.

As mentioned above, injuries with a TLICS score less than 4 can be managed conservatively. However in a multiply-injured patient, surgical fixation may be warranted, as patients tend to have shorter ICU stays, less time on the ventilator and earlier discharge from the hospital when they are surgically managed within 3 days of injury.⁸

Bracing is accomplished through extension bracing or, more commonly, the use of a Thoracolumbosacral Orthosis (TLSO). This removable brace is worn for 10-12 weeks on average, with frequent radiographs to monitor progression of fracture healing and detect the development of progressive deformity or instability.

Operative Treatment

Surgical management of spine fractures in the lumbar and thoracic region is focused on correction of neurologic injury and stabilization of the spine. Decompression of the canal can be accomplished directly by removal of the lamina posteriorly or retropulsed bone posteriorly or anteriorly in conjunction with subtotal corpectomy. There is an increase in mortality with an anterior approach, thus making the posterior approach preferable for most injuries. Indirect reduction can be accomplished through a posterior approach with postural reduction and traction. This is typically reserved for patients with an intact PLC.⁹

The current workhorse of spinal stabilization in the thoracolumbar spine is pedicle screw and rod fixation. Fixation of two levels above and below the injury is generally accepted, however, more limited constructs may be acceptable if the fracture pattern permits.^10,11 Occasionally, when the anterior column is compromised, a corpectomy with cage placement may be necessary to restore the structural support of the spine. In these instances, an anterior/posterior approach must be used and can be done as a staged or one time procedure.

Low-energy compression fractures are one of the most common insufficiency fractures in older adults. The majority of these fractures can be managed conservatively with pain control, bracing, and activity modification. However, there are cases where pain persists and is lifestyle-limiting. Surgical management for these fractures involves either an open procedure or the use of kyphoplasty or vertebroplasty, although recently the American Academy of Orthopaedic Surgeons has provided a strong recommendation against the use of vertebroplasty in acute symptomatic vertebral compression fractures.¹²

Vertebroplasty and kyphoplasty are minimally invasive procedures involving the injection of polymethylmethacrylate cement into the fracture, the difference being that kyphoplasty uses a balloon to restore vertebral height and create a cavity for the cement. Kyphoplasty has resulted in significant post-procedural pain relief, and may be considered an option for patients presenting with an osteoporotic compression fracture.^13-15

Cases

Case 1

Figure 1. Lumbar spine axial computed tomography images, L1 burst fracture with intra-canal compromise and posterior osseous element involvement with fracture of the lamina.

Figure 2. Lumbar spine sagittal T2 weighted magnetic resonance images, L1 burst fracture with intra-canal compromise, with an intact posterior ligamentous complex.

Case 2

Figure 1. Lumbar spine sagittal computed tomography images, T12 flexion-distraction injury, disruption of posterior osseous elements, and focal kyphotic deformity and anterior translation of superior segment (T11).

Figure 2. Lumbar spine sagittal computed tomography images, following decompression and posterior instrumentation.

References

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10. Kim, N.H., et al., Morphometric study of the pedicles of thoracic and lumbar vertebrae in Koreans. Spine (Phila Pa 1976), 1994. 19(12): p. 1390-4.
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13. Zhang, J.D., et al., Comparison of vertebroplasty and kyphoplasty for complications. Orthop Surg, 2011. 3(3): p. 158-60.
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