The SpineTrauma
Spinal trauma is a disease of the young, and covers a wide range from minor injury, not needing radiological evaluation, to the quadriplegic patient, in whom an extensive radiological evaluation is required. The radiological evaluation is extremely important for correct treatment. It is not only necessary to describe the various fractures and dislocations, but also to evaluate the stability. It is also important to avoid false positive diagnosis, since this might lead to unnecessary painful traction and stabilization of the spine. False positive diagnosis is more often seen in the upper cervical spine because of anatomical variants, whereas false negative interpretation is more common in the lower cervical spine because of the problems with good visualization of this part, due to overprojection of the shoulders. New modalities, such as MRI, have allowed a better visualization of the soft tissues, which is important for prognosis and in some cases also for treatment.
Plain films
The most important examination is plain film radiography in most cases of spinal trauma, for several reasons. This modality is available in any hospital and can be performed easily even without moving the patient from his stretcher or bed. It is also the modality giving best information about dislocations, which sometimes might be difficult to appreciate on axial CT -slices. Important structures, such as the facets in the cervical spine, are shown well on plain films, while the findings on axial CTslices can be confusing because of unfavourable slice direction for visualization of these structures. Another advantage of plain films is that
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Figure 1.
Flexion injury with rupture of ligaments. In acute stage, examination in extension (a) and ftexion (b) reveals an almost normal finding. Five months later sliding with gibbus formation has occurred (c). This case illustrates that examination in provocation should not be performed too early, because muscle spasm will prevent sliding.
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examination can easily be performed in provocation, which allows evaluation of stability. Without provocation instability might be overlooked if there is an isolated rupture of the ligaments and no dislocation in neutral position. Plain films in flexion and extension should be obtained approximately two weeks after the
trauma. If the examination is performed too early, it might be a false negative because the pain causing protective muscle
spasm will prevent sliding (Fig. l). Examination in flexion and extension should always be obtained in patients with severe
trauma to the
cervical spine, in whom conventional examination without provocation has not shown instability. In flexion there is normally a sliding amounting to a couple of millimetres of the superior vertebral body in relation to the inferior. This sliding occurs in the normal case in a staircase pattern in the whole
cervical spine and disappears in extension. This can be rather marked, especially in young girls with weak muscles (Fig. 2). In
pathological cases there is a local displacement which is more pronounced than at normal levels and the distance between the spinous processes is wider at the level of
trauma than at others. A situation which might cause problems is local displacement secondary to
degenerative a
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Figure 2.
Normal mobility of cervical spine. Note staircase sliding at several levels in flexion (a). In extension sliding disappears (b). |
disease. If these patients are examined without old films available their displacement might be misinterpreted as caused by a ligamentous tear. A careful evaluation of the intervertebral joints and the disks, and examination in provocation, should, however, disclose the correct etiology (Fig. 3). Plain films also visualize the prevertebral soft tissues. Prevertebral hematoma, causing increased soft tissues, is a sign of rupture of the anterior longitudinal
ligament. As a rule, unstable injuries have a prevertebral hematoma, whereas it is unusual for this to be found in stable lesions.
The minimum requirement for a plain film examination in the acute stage is frontal, lateral, and oblique views with 45° tube angulation. A good rule is to start with the
 | Figure 3.
Anterior subluxation of C4, caused by intervertebral arthrosis. No trauma. |
lateral view, which usually gives information about the degree of injury and dislocations. This view should cover the area down to at least the level of
T1, which sometimes can be difficult, but can be achieved by gently pulling the arms downwards during exposure to avoid overprojection of the shoulders. Sometimes it is impossible to visualize the lower
cervical spine on lateral views, but in almost all cases important dislocations can be seen on oblique views, in which it is easy to image the lower
cervical spine and upper
thoracic spine (Fig. 4). In patients with marked kyphosis in the
thoracic spine and lordosis in the
cervical spine, it is an advantage to angulate the
x-ray tube approximately 10° in the caudal direction for best visualization of the lower cervical- upper
thoracic area. It is also valuable to obtain a frontal
view of the odontoid process in the open-mouth-projection. These views will almost always give enough information for the acute treatment of
patients with
cervical spine trauma. Later there might be a need for
special views. Conventional tomography, especially for evaluation of odontoid fractures and fractures of the facets are often valuable. In the evaluation of
thoracic and lumbar
spine injury it is usually sufficient to take only frontal and lateral views.
Computed tomography (CT)
CT gives valuable additional information to plain films and is of special value for identification of fractures, particularly of the neural arch, and in patients with burst fractures in whom there is a suspicion of bone fragments in the spinal canal. In patients with suspected Jefferson fracture of C1, CT gives the best information about the degree of injury including ligamentous tears and fracture dislocations (Fig. 5). CT-slices should be thin and parallel to the neural arch for best the information. A slice direction parallel to the disk sometimes results in slightly oblique views through the neural arches which are difficult to interpret. If thin slices have been obtained, reformatting gives valuable information about dislocations.
Magnetic resonance imaging (MRI)
In patients with spinal trauma and neurological deficit which cannot be explained by the findings on plain films, MRI gives valuable additional information about the soft tissues. In the majority of patients with
neurological symptoms a cord
contusion can be disclosed by
MRI (Fig. 6), but more importantly it rules out a traumatic
disk herniation (Fig. 7) or epidural hematoma (Fig. 8) which requires an operation. The degree of cord
contusion might also be helpful for establishing prognosis. This is, however, not yet fully evaluated. Significant traumatic
disk herniation and epidural hematomas as the main causes of neurological symptoms are rare but extremely important to rule out since they can be treated and the presence of these lesions might also change the surgical approach.
MRI is also valuable in the post-traumatic stag e, especially for evaluation of possible
cyst formation in patients with increasing neurological symptoms. Although fixation material might disturb imaging, a proper selection of sequence- and frequency-encoding direction usually allows visualization of most or all the cord.
 a
| Figure 7.Traumatic disk herniation. Plain films show signs of ligamental tear shown as sliding in the intervertebral joint (arrow) and widening of the disk space (a). Posterior fixation is planned. However, MRI reveals a traumatic disk herniation (arrow) with compression of the cord (b). The surgical approach is therefore changed to an anterior approach with removal of the disk herniation followed by fixation later. |
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 | Figure 8.
Whiplash trauma in patients with anchylosing spondylitis. Displacement is seen at C6-C7 level and there is a posterior epidural hematoma compressing the cord. |
Pathology
Anatomical considerations
The construction of the spine is very specialized to allow both mobility and stability, which reduces the risk of trauma to the nervous soft tissues. The stability is achieved by the bony elements, intervertebral disks, ligaments and muscles. The stability is better in the thoracic and lumbar spine than in the cervical spine, which has more mobility. In the thoracic region, the ribs also make the spine more stable. It is unusual to see significant dislocations in this area, which are sustained only in major trauma. In the lumbar spine traumatic dislocations causing neurological deficits are similarly unusual. In the cervical spine, on the other hand, weaker construction and greater mobility allow compression injury of the card and nerves, following relatively moderate trauma. The width of the spinal canal is very important with regard to the potential consequences of dislocation. The ratio between the sagittal measurement of the spinal canal and the vertebral body is usually approximately l in the middle cervical spine. This ratio should not be lower than 0.8. The width of the canal is much larger in the C1-C2-area than lower down in the cervical spine. A rather pronounced dislocation can therefore be seen in the C1-C2-area without neurological symptoms. There is a considerable individual variation in the width of the cervical spinal canal.
Important for correct diagnosis in spinal trauma is knowledge of the common anomalies which are often found in the upper cervical spine. A frequent variant is a defect in the arch of C1, which should not be misinterpreted as a fracture. In congenital variants the bone edges are usually rounded and cortical bone is seen in all areas, which is not the case in patients with fractures. Another area in which anomalies are frequent is the odontoid process. The odontoid process is formed from several dermatomes and sometimes there will be a non-union and a formation of an osodontoideum. This might be misinterpreted as a fracture but, as in other anomalies, the margins are rounded and sclerotic.
Cervical spine
Trauma in the cervical spine can be divided according to the type of trauma in flexion injuries, extension injuries and injuries caused by axial or vertical force. There is also a group in which the force is unclear or varied.
Flexion injuries
Subluxation
This injury is most often seen in the lower cervical spine where there is a rupture of the posterior ligaments, causing the vertebra above the trauma to slide in the forward direction. The distance between the spinous processes is increased and there is a dislocation in the intervertebral joints of varying degree. In this type of injury the radiological finding is sometimes very subtle and the situation seems to be stable. After some time, when the muscle defence diminishes, a sliding above the lesion might be seen, causing an angulation (Fig. l). In uncertain cases examination in flexion and extension is mandatory to rule out a tear of the ligaments. This examination should be performed approximately two weeks after the trauma.
Bilateral interfacetal dislocation
This type of injury is caused by stronger force than in anterior subluxation but is otherwise of the same type. In the worst situation there is a locked position between the facets at the injured level (Fig. 4). Sometimes there is a fracture of the facet in this type of trauma, which is important to disclose because it influences the stability after the initial treatment. This injury is unstable because there is a tear of all ligaments and the disk. Many of the patients are tetraplegic if they have a narrow canal. In some cases the locked position is only seen on one side.
Wedge fracture
The wedge fracture is seen in the lower cervical spine and is stable. Usually there is a compression of the upper endplate of the vertebra with preserved posterior border. It is important that a burst fracture, which might have a fragment in the canal, is not misinterpreted as a wedge fracture. In uncertain cases CT should be performed.
Fracture of the spinous process
Another example of a flexion fracture which is stable is the isolated fracture of the spinous process.
Flexion tear-drop fracture
In this type of fracture the force has been vertical with the spine in flexion. This leads to an avulsion of a triangular fragment from the ventral lower border of the vertebra. This is actually the only part of the vertebra which remains in normal position. During the trauma the posterior part is pushed backwards, creating a severe gibbus and severe trauma to the cord. Thereafter the posterior elements return to almost normal position (Fig. 6). In 50% of the patients there is a tetraplegia after such a trauma. The spine is totally unstable.
Extension injuries
Hyperextension injury without fracture
In these cases the injury is caused by a forceful extension of the cervical spine, causing a rupture of the anterior longitudinal ligament and the distance between the vertebral bodies is increased anteriorly. When the injury occurs the dislocation is pronounced, causing a severe compression of the spinal cord, causing tetraplegia. After the trauma the bony component returns to essentially normal position, and the only thing found at examination is a somewhat wide disk space anteriorly. Typical for this injury is a very pronounced prevertebral hematoma. The situation is unstable in extension. Accompanying facial trauma is also typical.
Hyperextension fracture
In this injury the force also causes a hyperextension, but there is also a vertical component. The injury causes fracture in the base of the pedicle and posterior elements on one side, causing the facet to rotate forwards. This leads to a horizontal position of the facet, which is typically seen on the frontal vie w (Fig. 9). The vertebral body is dislocated in the anterior direction. On the other side, which is usually without fracture, a subluxation is found in the intervertebral joint. There is also an injury to the anterior longitudinal ligament and therefore a prevertebral hematoma. The injury is unstable.
Hang-man fracture
In this fracture there is a strong extension of the cervical spine, causing fractures on the pars interarticularis on C2 (Fig. 10). Occasionally, there are fractures in the massa lateralis or further posterior in the lamina. The fractures affect both sides, but are not necessarily symmetrical. The degree of instability varies. The injury is often without neurological deficits, depending on the width of this part of the cervical spine.
Extension tear-drop fracture
In this type of injury, a
fracture with avulsion of a small triangular fragment from the anterior lower part of C2 is found. This
fracture is unstable in extension, because the anterior longitudinal
ligament is tom but stable in flexion, because the posterior ligaments are intact, as well as the facets. Frequently, a prevertebral hematoma is found. Usually there are no neurological symptoms.
Isolated fracture of the posterior atlas
In hyperextension, C1 is sometimes compressed between C2 and the occipital bone, causing an isolated fracture of the neural arch. This is a stable fracture without neurological symptoms. The injury must, however, be differentiated from the Jefferson fracture, which is most easily done by CT.
Injuries caused by vertical force
Burst fracture
Vertical force affecting the cervical spine in neutral position can cause burst fractures in the vertebral bodies of the lower cervical spine. The
vertebral body will burst in several fragments, and one or several of these can be pushed posteriorly into the canal (Fig. 11). The intervertebral joints and the ligaments are usually intact and the injury is thus stable. CT is often necessary to show the degree of encroachment upon the spinal canal. Traction can reduce the narrowing of the canal.
Jefferson fracture
Axial force sometimes causes a burst fracture of the atlas, caused by downward force from the occipital condyles towards the atlas. In the typical case there are fractures of the arch, both anteriorly and posteriorly. The lateral mass is displaced laterally on both sides and the transverse ligament is ruptured. Sometimes a small fragment is found, indicating rupture of the transverse ligament. The injury is unstable when the transverse ligament is ruptured. On plain films there is a typical finding with lateral displacement of the lateral mass on the atlas. However, all fractures might be difficult to visualize without tomography. CT is the best modality for evaluation of all fractures (Fig. 5).
Miscellaneous Odontoid fractures
Odontoid fractures can be caused both by flexion and extension. There are two main types - one in which the fracture affects the odontoid process, and another where the fracture runs through the base of the odontoid process downwards in the vertebral body of C2. The first type is more unstable and has a greater tendency to pseudarthrosis. Often the patient has moderate symptoms, and it is not unusual that the fractures are discovered a week after the trauma, when the patient is examined because of remaining pain.
Thoracic and lumbar spine injuries
Most injuries are found between the Tl2-- and L2-levels, which is explained by the fact that this is the area where the spine turns from a rigid upper part to a mobile lower part. This is also where the thoracic kyphosis turns into the lumbar lordosis. Isolated dislocations without fracture, which can be se en in the cervical spine, are extremely unusual in the thoracolumbar area. Fractures in this area can be divided into fractures affecting the vertebral body, fractures of the transverse process, posterior ligaments, transverse shear injuries and fracture dislocations.
Fractures of the vertebral body
The most common fracture is the compression fracture of the anterior part of the vertebral body. It is usually caused by a pure hyperflexion injury. The posterior elements of the vertebra are not injured and the fracture is thus stable. In some cases there is a rupture of the ligaments and anterior sliding of the vertebra above the compressed level. When the force is axial, a burst fracture can be found. In this situation a fragment is sometimes pushed backwards towards the spinal canal, causing compression of the cauda equina or conus. CT is extremely valuable in this situation, because it shows the degree of compression, which is sometimes difficult to evaluate on plain films (Fig. 12).
Fractures in the posterior elements and transverse processes
Fractures through pedicles, laminae and facets are unusual as isolated injuries, but are sometimes seen in connection with fractures to the
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| Figure 12.Compression fracture of L2 (a). CT reveals a fragment in the spinal canal with compression of the cauda equina (b). After stabilization with a Harrington device. the dislocation of the fragment has diminished considerably (c). |
vertebral body and are important in the evaluation of stability. Fractures of the transverse processes are more common as isolated injuries, but are usually associated with direct focal force.
Transverse shear injury
Transverse shear injuries are uncommon and are most commonly seen in the upper lumbar spine. A special type is the Chance fracture in which there is a horizontal fracture through the vertebral body, pedicles and laminae. This is an unusual injury which can be seen in traffic accidents in which a lap-seat-belt has been used (Fig. 13).
Fracture dislocations
Fractures with dislocations are usually caused by a combination of flexion and rotation forces. Often there are compression fractures as well as fractures through the posterior elements. These injuries are most often found in the lumbar spine.
Stig Holtås, Maximilian F. Reiser and Axel Stäbler