Summary of Key Points
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Spinal fractures are relatively common injuries that are more likely to occur at the thoracolumbar junction, are associated with neurologic injury in up to 20% of cases, and have outcomes impacted by neurologic examination at admission as well as the level of injury.
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Evaluation of a patient with suspected thoracolumbar fracture should include a neurologic examination, assessment for areas of spinal tenderness or step-off, and imaging studies (computed tomography and possibly magnetic resonance imaging).
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There are three major classification systems for thoracolumbar injuries: the Denis three-column system, the Magerl AO system, and most recently the Thoracolumbar Injury Classification System (TLICS).
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The Denis three-column system is based on the injury pattern to the anterior (anterior longitudinal ligament to midvertebral body), middle (midvertebral body to posterior longitudinal ligament), and posterior (pedicle to ligamentous complex) columns.
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Major categories of the Denis system include compression, burst, and seatbelt-type fractures, as well as fracture dislocations.
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The Magerl AO classification is based on mechanism of injury and includes types A, B, and C injuries, listed in the order of worsening instability and increased likelihood for the presence of neurologic deficit.
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The TLICS was developed to guide conservative versus surgical management of fractures.
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TLICS utilizes three main factors including injury morphology, neurologic status, and integrity of the posterior ligamentous complex to create a numeric score.
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The TLICS score is used to determine whether to treat a thoracolumbar fracture operatively (TLICS score ≥ 5) or conservatively (TLICS score ≤ 3). A score of 4 is indeterminate, meaning either conservative or surgical treatment can be considered.
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If surgery is deemed necessary to stabilize a fracture, the literature supports early intervention in the hemodynamically stable patient without significant medical comorbidities.
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Bracing, even though not shown to be beneficial for improving patient outcomes, can be used in the treatment of less morphologically severe fractures, such as compression and burst fractures, in the neurologically intact patient.
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If surgery is recommended, there is no consensus on optimal surgical management of unstable thoracolumbar fractures.
Traumatic spinal fractures involving the thoracic and lumbar spine represent 54% to 90% of all spinal fractures, and have an estimated incidence of 700,000 fractures per year worldwide. In cases of polytraumatic injuries, 6% to 30% of patients have an associated thoracolumbar fracture. Fifty-two percent of these injuries occur at the T10-L2 level, 32% occur at L3-5, and 16% occur at T1-9, highlighting the thoracolumbar region as an area prone to traumatic injury. Neurologic injury is seen in up to 20% of thoracolumbar fractures. When evaluating lumbar and thoracic fractures separately, complete neurologic injury is more frequently seen in thoracic fractures. This is likely attributable to the narrowing of the spinal canal in the thoracic spine. The elderly are particularly predisposed to suffering from thoracolumbar fractures, primarily due to osteoporosis. Management of osteoporotic vertebral fractures is discussed in another chapter, as is the management of pediatric thoracolumbar fractures.
The patient’s neurologic examination at admission and the level of injury are important factors in determining long-term functional outcome after thoracolumbar fracture. Patients with an American Spinal Injury Association (ASIA) A score (complete loss of motor and sensory function below level of injury) have only a 7.7% likelihood of improvement, followed by ASIA B (some sensation distal to injury) at 66.7%, ASIA C (at least 50% of muscles cannot move against gravity) at 84.5%, and ASIA D (more than 50% of muscles can move against gravity) with a 95.2% likelihood of improvement. With regard to the level of injury, patients with conus impairment caused by upper lumbar vertebral injuries have up to 90% of chance for improvement of one or more ASIA levels in comparison to 22.4% for those with thoracic injuries.
Evaluation and Workup
The evaluation of a patient with a thoracolumbar injury should initially consist of assessment and management of the patient’s airway, breathing, and hemodynamic status, as performed in association with the trauma team. After the airway is deemed secure and the patient is hemodynamically stable, a comprehensive neurologic examination is performed, dependent on the patient’s ability to participate due to altered mentation or intubation. A complete neurologic examination includes evaluation of mental status, cranial nerves, testing of strength/sensation/reflexes in the upper and lower extremities, perianal sensation, catheter tug reflex, bulbocavernosus reflex, anocutaneous reflex, and rectal tone. Areas of spinal tenderness or step-offs should be evaluated utilizing proper logroll technique.
Further workup of a trauma patient suspected of having a spine injury should include a total spine computed tomography (CT) as opposed to a radiograph, as multiple studies have shown CT to be more accurate. In the setting of a patient with a mild neurologic deficit including radiculopathy, paresthesias, or in a patient with a neurologic deficit not attributable to a lesion on CT, magnetic resonance imaging (MRI) should be performed to investigate possible disruption of neural elements, disc, or posterior ligamentous complex (PLC). An MRI is important in these instances, as several studies have shown that MRI identified additional fractures not seen on the original CT scan, thus changing the classification of the fracture and at times changing the proposed treatment from nonoperative to operative management.
Classification of Thoracolumbar Fractures
After evaluation of the patient’s CT and MRI scans, treatment plans are made. Treatment choice will depend on multiple factors including the biomechanical stability of the fracture, neurologic status of the patient, and presence of any complicating injuries or chronic comorbidities. To help determine the optimal course of action, the fracture type should be classified. The primary goal of a classification system is to establish a precise, comprehensive, and reproducible methodology for categorizing thoracolumbar injuries to guide therapy and determine outcomes. The three most commonly used classification systems include the Denis three-column system, the Magerl AO system, and, more recently, the Thoracolumbar Injury Classification System (TLICS).
Denis Three-Column System
The Denis three-column system is a classification system based on the injury pattern to specific anatomic structures, with the added concept of a middle column to the traditional anterior and posterior columns ( Fig. 131-1 ). The anterior column is composed of the anterior longitudinal ligament, anterior annulus fibrosus, and the anterior half of the vertebral body. The middle column comprises the posterior half of the vertebral body and includes the posterior annulus and posterior longitudinal ligament. The posterior column encompasses the region beginning at the pedicle and ending at the PLC. Based on this system, a fracture is considered unstable if two of the three columns are affected in some way. Even though simple to use, the Denis system has been criticized for its relative lack of inclusivity and reproducibility for unusual fractures.
Utilizing this classification system, thoracolumbar spinal injuries are split into minor and major categories. Minor injuries include transverse process fractures, facet fractures, pars interarticularis fractures, and spinous process fractures. The most common minor spinal injury is the transverse process fracture. According to the three-column system, major fractures are classified into compression fractures, burst fractures, seatbelt-type injuries, and fracture dislocations. A compression fracture ( Fig. 131-2 ) is a lesion that occurs when the anterior column is compressed, and in severe cases the posterior column distracted.
In contrast to compression fractures, burst fractures result from failure of the vertebral body under axial load. Even though burst fractures occurred in only 14% of patients in the analysis by Denis, more recent data demonstrate that thoracolumbar burst fractures account for up to 60% of thoracolumbar injuries. The mechanism of injury that results in a burst fracture involves compression of both the anterior and middle columns, with no change in height of the posterior column ( Fig. 131-3 ).
Seatbelt-type injuries involve distraction of both the middle and posterior columns caused by flexion and at times distraction. The anterior column may become compressed or remain untouched, but regardless acts as a hinge in these injuries. The fact that the anterior column is not completely disrupted in these injuries differentiates them from fracture dislocation injuries. An example of a Chance fracture, a seatbelt-type injury characterized by a one-level bony injury, is shown in Figure 131-4 . Patients with this type of injury, as severe as they appear on imaging studies, usually present with no neurologic deficit.
Fracture dislocations describe failure of all three columns under any mechanism ( Fig. 131-5 ). These devastating injuries at times reduce on their own when in the supine position, and high index of suspicion is needed in the setting of a neurologically impaired patient with only subtle findings on CT. These clues include multiple rib fractures, multiple transverse process fractures, unilateral articular process fractures, laminar fractures, or spinous process fractures at the level of injury. These injuries most commonly occur at the thoracolumbar junction and are associated with neurologic injury in 75% of cases; 39% of these patients present with complete paraplegia.
Magerl AO System
This classification system is much more comprehensive than the Denis system and groups injuries into one of three types based on injury mechanism. It lists fractures in terms of worsening instability as the scale progresses from A to C. The basis behind this model is a two-column system (unlike the Denis three-column system). In the two-column system, the anterior column is composed of both the anterior and middle columns seen in the Denis three-column system. The posterior column is the same as it is in the Denis three-column system. Another important point to consider in the Magerl AO system is that injuries to a column should be evaluated as to whether they disrupt the column or do not cause significant instability. This detail will be highlighted later as the different types of fractures are described.
Type A fractures are caused by vertebral body compression without transverse disruption of any of the columns and focus on injury patterns of the vertebral body. In these injuries, the anterior column is injured but not completely disrupted, with severity worsening from A1 to A3 classification, and the posterior column is only insignificantly injured, if at all ( Table 131-1 ). Type A fractures include compression (A1 and A2) and burst (A3) fractures. Regarding posterior column injury, the most severe burst fractures (A3.3) can have an associated vertical split fracture through the spinous process or lamina. However, these split fractures through the posterior elements have negligible contribution to instability and the PLC remains intact.
| Fracture | Subclassification |
|---|---|
| A1 impaction fractures | |
| A1.1 end plate impaction | |
| A1.2 wedge impaction | |
| A1.3 vertebral body collapse | |
| A2 split fractures | |
| A2.1 sagittal split | |
| A2.2 coronal split | |
| A2.3 pincer | |
| A3 burst fractures | |
| A3.1 incomplete burst | |
| A3.2 burst-split | |
| A3.3 complete burst |
In contrast to Magerl AO type A fractures, type B injuries involve transverse disruption of either one or both of the columns with distraction ( Table 131-2 ). In types B1 and B2 injuries, the posterior column is completely disrupted due to a flexion-distraction injury mechanism. In these injuries, elongation of the distance between the adjacent posterior vertebral elements can be present on imaging if the injury did not self-reduce due to positioning. The difference between B1 and B2 injuries is that the posterior disruption is mostly ligamentous in B1 injuries, whereas it is mostly bony in the B2 group. Subgroups are separated depending on the anterior column injury associated with the posterior column disruption. In type B3 injuries the opposite occurs, where the transverse disruption starts in the anterior column and may extend into the posterior column. B3 injuries occur due to hyperextension. Type C fractures are caused by anterior and posterior column injuries with rotation causing disruption off all longitudinal ligaments and discs ( Table 131-3 ).
| Fracture | Subclassification |
|---|---|
| B1 posterior disruption predominantly ligamentous (flexion-distraction injury) | |
| B1.1 with transverse disruption of disc | |
| B1.2 with type A fracture of vertebral body | |
| B2 posterior disruption predominantly osseous (flexion-distraction injury) | |
| B2.1 transverse bicolumn | |
| B2.2 with transverse disruption of disc | |
| B2.3 with type A fracture of vertebral body | |
| B3 anterior disruption through disc (hyperextension-shear injury) | |
| B3.1 hyperextension-subluxations | |
| B3.2 hyperextension-spondylolysis | |
| B3.3 posterior dislocation |
| Fracture | Subclassification |
|---|---|
| C1 type A injury (compression) with rotation | |
| C1.1 rotational wedge | |
| C1.2 rotational split | |
| C1.3 rotational burst | |
| C2 type B injury with rotation | |
| C2.1 B1 injury (ligamentous, flexion-distraction) with rotation | |
| C2.2 B2 injury (osseous, flexion-distraction) with rotation | |
| C2.3 B3 injury (hyperextension-shear) with rotation | |
| C3 rotational-shear injury | |
| C3.1 slice | |
| C3.2 oblique |
Type A fractures were found in 66.1% of the patients used to develop this classification system, followed by type C fractures in 19.4% and type B fractures in 14.5% of patients. Some aspect of neurologic deficit was found in 14%, 32%, and 55% of types A, B, and C fractures, respectively. Only 2% of the A1 and 4% of the A2 fractures showed any neurologic deficit. Type A injuries are more likely to occur cranially than caudally in the thoracolumbar spine. Type C injuries are more frequently located in the lumbar spine. Type B fractures are more often found at the thoracolumbar junction. The authors of the system hail its grouping based on mechanisms of injury and morphologic damage by which the degree of instability is determined. However, others see this system as cumbersome with only moderate reliability and reproducibility among surgeons.
Thoracolumbar Injury Classification System
Because other classification systems were viewed as being either excessively convoluted or too simple to be relevant in decision making, the TLICS was created in 2005 by the Spine Trauma Study Group and has proven to be useful clinically ( Table 131-4 ). This system takes into account any associated neurologic injury and also guides the surgeon on whether to pursue conservative or surgical management. The three main factors when determining a TLICS score are injury morphology, neurologic status, and integrity of the PLC. An injury morphology score of 1 is given to compression injuries, which are defined as vertebral body height loss or disruption through the vertebral end plate. Using this definition, compression injuries would comprise traditional compression fractures and burst fractures, with the latter given an extra point on the injury morphology scale. A translation/rotation injury is defined as any horizontal displacement of one vertebral body over the other in the coronal or sagittal plane and is given a score of 3. Distraction injuries, described as complete anatomic dissociation in the vertical axis, are given a score of 4. It should be noted that if a specific level of injury has components of multiple injury morphologies, the higher score is given.
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