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Injuries to the thoracolumbar spine are usually the result of high-energy blunt trauma; 65% of thoracolumbar fractures occur in motor vehicle accidents or in falls from a height. Hu et al1 in their epidemiological study observed that the incidence of spinal injuries was 64/100,000 population per year. Among the thoracolumbar injuries, 50 to 60% affected the T11–L2 region, 25 to 40% affected the thoracic spine, and 10 to 14% involved the lower lumbar spine and sacrum. Thoracolumbar fractures are commonly observed in men and the peak incidence is observed in adults between 20 and 40 years of age. In a multicenter study by Knop et al,² the incidence of neurologic deficit ranged from 22 to 51% depending on the fracture type (22% in type A, 28% in type B, and 51% in type C fractures, according to the AO classification).

Because these are high-velocity injuries, thoracolumbar fractures are commonly associated with other injuries, such as rib fractures, pneumohemothorax, abdominal visceral injury, and even diaphragmatic rupture. Although thoracic spine fractures are associated with fractures of the rib and intrathoracic damage, seat-belt injuries and flexion-distraction injuries are often associated with intra-abdominal visceral injuries. Long-bone fractures and head injuries often coexist and can distract clinical attention, leading to missed injuries of the thoracolumbar spine. This has been reported in as many as 20% of patients with high-energy blunt trauma and altered mental status. Saboe et al3 reviewed 508 consecutive spinal injury patients and identified associated injuries in 47%, including head injuries (26%), chest injuries (24%), and long-bone injuries (23%). Although most patients with missed injuries suffer no adverse effects, some may have severe complications, including quadriplegia and chronic disability, and some may die.

Plain Radiographs

Plain radiographs are the first line of investigation for any patient with spinal trauma. They are universally available, portable, fast and inexpensive, and are performed as part of the trauma survey. Good-quality anteroposterior (AP) and lateral views in the supine position are the minimum requirement. The quality of the radiograph is of importance, as subtle fractures and instabilities may be easily missed in poor-quality films. The standard radiographs prescribed are the thoracic (T1 to T10), thoracolumbar (T10 to L3), and lumbosacral (L1 to sacrum). The appropriate radiograph is ordered based on the patient’s level of neurologic deficit (in cases of neurologic injury) and the presence of any local tenderness or deformity. In trauma situations, it is not always possible to get the best radiograph. If the radiographs are not satisfactory or inconclusive, a CT scan must be performed.

Table 2.1 Anteroposterior Radiography Features in Spinal Trauma

Careful study of the AP and lateral films will give valuable clues regarding the nature of the injury, the presence of instability, the type of injury based on classification systems, and the need for further investigations. (Tables 2.1 and 2.2). In the AP view, the following anatomic structures should be clearly appreciated: both pedicles, the vertebral body (in outline), the lamina, the spinous process, and both transverse processes. Fractures involve a spectrum of injuries ranging from simple fractures to dislocations. Simple fractures of one or two transverse processes or of the isolated spinous process can be seen, and are stable injuries. Loss of vertebral height as compared with adjacent vertebrae indicates a compression type of fracture (Fig. 2.1a). This can be evaluated by drawing vertical lines along the middle of the fractured and adjacent vertebra and then comparing their length. In burst fractures, the interpedicular distance is observed to be increased as compared with the adjacent pedicles (Fig. 2.1b). In the presence of rotational unstable injuries such as dislocation, loss of coronal alignment can be present, which can be appreciated by assessing the alignment of the pedicles and spinous process (Fig. 2.1c). Widening of the interspinous distance can be observed in flexion-distraction injuries, although this is better observed in the lateral view (Fig. 2.2).

Table 2.2 Lateral Radiography Features in Spinal Trauma

Fig. 2.1a–c (a) Vertebral body height is measured in the middle of the fractured vertebral body (vertical dashed line) and compared with the adjacent normal vertebra (vertical solid line). (b) Increase in the interpedicular distance indicates a burst fracture. A horizontal line drawn between the two pedicles at the level of the fractured vertebra (solid line) is longer than the lines drawn at the level of pedicles of adjacent normal vertebrae (dashed lines), indicating a widened interpedicular distance. (c) The presence of vertebral translation can be identified by drawing straight line along the lateral vertebral borders (two vertical arrows). Subtle translation or rotational instability can be identified by aligning the spinous processes of all vertebrae.

The lateral radiographic film reveals important features of injury to the spinal columns and compromise of the spinal canal. In patients with compression injury, there will be a vertebral body fracture that is observed as loss of anterior vertebral body height (Fig. 2.3a). Findings such as significant kyphosis > 30 degrees or collapse of > 50% of vertebral height may indicate concomitant injury to the PLC and may indicate instability (Fig. 2.3b). For further assessment of the status of the PLC, standing or sitting (weight-bearing) radiographs can be performed to look for further increase in the kyphosis. An increase of kyphosis by more than 10 degrees probably indicates PLC disruption, and spinal stabilization would be indicated. If both anterior and posterior vertebral body height is decreased, it indicates AO type A3 or A4 injury (Fig. 2.4a). Rotational unstable injuries can be detected by the loss of sagittal vertebral alignment or the presence of vertebral translation or facet-joint subluxation (Fig. 2.4b). A horizontal split in the spinous process may indicate a type B1 or B2 injury, if associated with a concomitant vertebral body fracture (Fig. 2.4c).

Fig. 2.2a,b (a) An increased interspinous distance (white arrow) when compared with the adjacent levels would indicate distraction injury with failure of the posterior tension band. (b) Horizontal fracture line in the vertebral body (yellow arrow) can sometimes be detected in the AP radiograph, if careful attention is paid.

Fig. 2.3a,b (a) The anterior vertebral body height is measured along the anterior vertebral border from the superior to the inferior end plate and compared with the adjacent normal vertebra. (b) Vertebral body collapse > 50% and or a kyphosis > 30 degrees would indicate potential instability of the vertebral column.

Fig. 2.4a–c (a) The posterior vertebral body height is measured along the posterior vertebral border from the superior to the inferior end plate and compared with the adjacent normal vertebra. Loss of posterior vertebral height can indicate instability and also possible retropulsion of fracture fragments into the spinal canal. It is an indication for further evaluation with computed tomography (CT) to assess the extent of bony injury. (b) The presence of vertebral translation can be identified by drawing straight lines along the anterior border of individual vertebrae. In these situations, also check the facet joints for subluxation or dislocation. (c) The presence of a spinous process fracture may indicate just a type A0 injury. However, in the presence of a type A1 to type A4 injury anteriorly, a coexistent spinous process fracture would indicate a type B1/B2 injury. Any such suspicion would mandate further CT evaluation.

In the lateral film, the presence of the findings listed in Table 2.2 should be determined.

Computed Tomography in Spinal Trauma

Computed tomography provides better spatial resolution than conventional radiography. The ability of CT to visualize the bone in axial, sagittal, and coronal planes enables better detection of fracture and delineation of fracture morphology. Acquisition is faster when compared with MRI. The field of view can be increased even after acquisition using the raw data to include the abdominal and thoracic organs in which coexistent injuries can be identified. Whole-body CT scan in polytrauma situations enables the identification of multi-organ injury and noncontiguous multilevel spinal injuries. Three-dimensional (3D) reconstruction of acquired images can be done, which helps in surgical planning. In spinal trauma patients, CT scans provide finer details of the bony involvement, the extent of canal compromise, and the presence of occult posterior element fractures. CT has been shown to be more accurate than plain radiography in distinguishing wedge compression fractures from burst fractures in the thoracolumbar spine. A study found that 25% of burst fractures are misdiagnosed as compression fractures if radiographs alone are evaluated.⁴ In postoperative situations, CT can be used to assess the adequacy of internal fixation and detect postoperative complications. Localization of foreign bodies in cases of penetrating injuries of the spinal column is best performed with CT. The only disadvantage of CT is exposure to ionizing radiation (see text box).

Many major trauma centers now use whole-body CT scans as the primary imaging modality for evaluating the spine, especially in the obtunded and polytraumatized patient or in high-velocity trauma patients. The sensitivity, specificity, and negative predictive value of CT are reported to be 98.1%, 98.8%, and 99.7%, respectively. Brown et al,5 in a study of 3,537 patients with blunt trauma evaluated with spiral CT, found that CT identified 99.3% of the spinal fractures. They recommended it as a standard screening test for spinal fractures. Similarly, screening of the thoracolumbar spine as a part of the thoracic-abdominal-pelvic CT survey excludes the need for routine spinal radiography in blunt trauma patients and identifies most injuries (Fig. 2.5).

Fig. 2.5a–c (a) Whole-body CT scan of the chest, abdomen, and pelvis is preferred in patients with blunt injuries with suspected visceral injuries of the thorax and abdomen. Thoracolumbar fractures can be identified in up to 99% of patients. This patient had a diaphragmatic rupture (a,b, white arrows) and a type B2 injury at L1 (a,c, black arrows).

Fig. 2.6a,b The extent of vertebral body comminution and the displacement of fragments is clearly visualized in sagittal (a) and axial (b) CT images.

Table 2.3 Typical Radiological Observation in the Different Computed Tomography (CT) Views and Their Interpretation

While evaluating the CT images, it is a good practice to start with sagittal images. The sagittal sections are serially examined from one pedicle to the other pedicle. The axial images are evaluated next, moving from cranial to caudal with particular attention at the level of pedicles. The coronal sections are evaluated from anterior to posterior. The sagittal and axial CT images of the injured segment provide excellent detail regarding the extent of vertebral body comminution, the extent of separation of the broken fracture fragments, and the severity of retropulsion of bone fragments into the spinal canal (Fig. 2.6). This information is essential to determine the need for and to plan anterior decompression and reconstruction and to determine the prognosis of neurologic recovery (Table 2.3). In patients with burst-type fractures, the axial CT images are assessed for two important signs: the reverse cortical sign and the lamina split sign. The reverse cortical sign refers to the presence of a retropulsed bone fragment into the spinal canal that has rotated 180 degrees such that its cortical side is in approximation with the cancellous part of the vertebral body (Fig. 2.7). Such an injury cannot be reduced by indirect decompression techniques and will require a direct decompression. The lamina split sign refers to the presence of a linear split fracture in the lamina in a patient with burst fracture (Fig. 2.8). Its presence indicates possible entrapment of dura and nerve roots within the fracture and requires taking extra care while performing decompression. The identification of pedicle fracture helps in planning the levels of fixation, as a broken pedicle precludes screw fixation. Transverse process and spinous process fractures can be clearly seen on CT scan as compared with conventional radiographs (Fig. 2.8c). The presence of horizontal split and separation of spinous process, interspinous widening, fractured contiguous spinous processes, increased facet joint space, empty naked facet sign, perched or dislocated facet joints, or vertebral body translation or rotation are important CT scan findings that can predict PLC injury (Fig. 2.9).

Fig. 2.7a,b (a) The amount and severity of retropulsion of bone fragments into the spinal canal is clearly depicted in axial and sagittal CT images. This gives an idea about the need and extent of spinal decompression. (b) The presence of reverse cortical sign is shown clearly in the CT images. This retropulsed fragment has rotated more than 180 degrees, so that the cortical surface is apposed to the cancellous surface of the main vertebral body, which will not unite with the main vertebral body if treated by ligamentotaxis.

Fig. 2.8a–c (a) The presence of a lamina fracture is an important CT observation. It indicates possible entrapment of nerve roots in a patient with incomplete neurologic deficit. It also warns the surgeon to be careful during the exposure of posterior elements. (b) The presence of a pedicle fracture can cause a blowout of the pedicle if a pedicle screw is accidentally inserted. This can be identified on the CT scan. (c) The presence of a spinous process fracture may indicate just a type A0 injury. However, in the presence of a type A1 to A4 injury anteriorly, a coexistent spinous process fracture would indicate a type B1/B2 injury. This is clearly evident on the CT scan.

Fig. 2.9a–d Computed tomographic features of a posterior ligamentous complex (PLC) injury. (a) Multiple contiguous spinous process fractures. (b) Horizontal split of the spinous process with separation. (c) Facet fracture with or without translation. (d) Reverse hamburger sign refers to the axial CT appearance of an uncovered vertebral articular facet when the facet joint is dislocated.

With the advent of MRI, the evaluation of patients with spinal trauma has changed tremendously. MRI enables detailed and thorough assessment of the spinal cord, paraspinal soft tissues, intervertebral disks, and ligamentous complexes. MRI permits direct visualization of the morphology of the injured cord parenchyma and the presence of any extrinsic compression on the spinal cord. MRI is invaluable in searching for residual soft tissue compression of the spinal cord due to factors such as acute disk herniations and epidural hematomas. The presence of residual compression of the spinal cord in the presence of a neurologic deficit is an important indication for early surgical decompression. Further current management of spinal injuries recognizes the significance of associated soft tissue injuries, and thus MRI has become increasingly important in the evaluation of spinal injuries. But it should be understood that although MRI is a powerful diagnostic tool, plain radiography and CT remain the most appropriate, the fastest, and the most cost-effective methods to evaluate most cases of spinal trauma, especially in emergency situations.

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