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Diagnostic strategies in spinal trauma
European Journal of Radiology 58 (2006) 76–88
Diagnostic strategies in spinal trauma Uwe Heinemann, Michael Freund ∗ Institut f¨ur Radiologie und Neuroradiologie, Klinikum Aschaffenburg, Am Hasenkopf 1, 63739 Aschaffenburg, Germany Received 25 November 2005; received in revised form 28 November 2005; accepted 1 December 2005
Abstract Spinal injuries may result in severe neurological deficits, especially if nerve roots or even the spinal cord are affected. Besides presenting the important anatomical and technical basis underlying the imaging findings of spinal injuries, the trauma mechanisms and the resulting injuries are discussed. Based on the current literature and recommendations of scientific organizations, an approach is provided to the radiologic work up of spinal trauma. The different imaging modalities are presented. Advantages and disadvantages of the methods are discussed. © 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Spinal trauma; Radiology; Spine; Computed tomography; Magnetic resonance imaging
1. Introduction Injuries to the axial skeleton such as fracture, dislocation, and soft tissue injury can affect the entire spine. The range of consequences of such injuries extend from minor pain without neurological deficit to severe paralysis and even death. Spinal fractures, mainly of the thoracic and lumbar spine, represent 3–6% of all skeletal injuries. They occur most frequently in individuals between the ages of 20 and 50 years [1]. The risk of damage to the spinal cord is greatest in cervical spine injuries as the spine is narrower there and movement is less restricted in the cervical spine than in the thoracic and lumbar portions. The most common causes of these injuries are traffic and sport accidents (e.g., scuba diving and skying) and falls from considerable heights. The results of an English study showed that: • Patients presenting after a motorcycle or automobile accident are most often men (motorcycle: 88.9%; automobile; 60.6%) of a young age (average age 30.2 and 37.8 years, respectively).
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Corresponding author. Tel.: +49 6021 323100; fax: +49 6021 323105. E-mail address: [email protected] (M. Freund). 0720-048X/$ – see front matter © 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrad.2005.12.007
• Among motorcyclists, the thoracic spine was affected most often (54.8%), among automobile drivers, the cervical spine (50.7%). • In general, motorcyclists sustain more serious injuries than automobile drivers, mortality is higher, and they present primarily with injuries to the extremities and mainly with flexion injuries of the thoracic spine. • Automobile drivers more frequently present with injuries to the cervical spine and show a higher rate of neck and face injuries. This is associated with the fixation of the chest and abdomen by a safety belt [2]. For injuries of the axial skeleton, the tasks of the radiologist include: • Confirming the diagnosis of an injury using appropriate diagnostic methods. • Diagnosing bony, chondral, ligamentous, articular, and any possible neural injuries as well as associated injuries to the neighboring soft tissues. • Establishing whether an injury has affected the stability of the spine. • Discussing diagnosis and further treatment with all physicians involved. • Documenting the results of treatment and assessing the course of the healing process.
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1.1. Traumatic injury to the cranial articulations 1.1.1. Special structural features There are no vertebrae between the occiput, atlas and axis, enabling greater and very complex movement in this spinal segment. The atlanto-occipital articulation is mainly stabilized by the articular capsule and the anterior and posterior atlantooccipital ligaments but also by the cruciform ligament of atlas (transverse ligament and apical dental ligament). The alar ligaments also prevent excessive movement between the atlas and the axis [3]. 1.2. Fractures of the atlas The most common cause of burst fractures of the atlas is collision injury (traffic accidents, swimming and diving accidents). The vertebral body is missing in the atlas, rendering the ring of the atlas susceptible for typical burst fractures after axial trauma (Jefferson fracture). Here, the most important stabilizing element for atlanto-axial articulation, the transverse ligament, can rupture. However, osteoligamentous ruptures of the transverse ligament at the point of attachment to the lateral mass of atlas occur more frequently than purely ligamentous ruptures. As a consequence, the tooth of axis no longer proceeds dorsally and due to ventral slippage from C1 to C2 can deviate dorsally into the spinal column and compress the spinal cord. The atlantodental articulation is then instable and through anteflexion causes ventral atlas dislocation. The normal distance between the dens and the atlas is <3 mm in adults and <4 mm in children. The key sign of a burst fracture of the atlas is lateral displacement of the lateral mass of atlas towards the dens axis on images taken with the mouth open. A lateral deviation of >7 mm indicates a ligamentous rupture and instability. Lateral X-rays of the cervical spine, including the skull base, are particularly important for evaluating a vertical subluxation involving the atlantooccipital articulation and displacement of the dens axis into the posterior cranial cavity because of the threat of injury to the medulla oblongata and the spinal cord. Atlanto-dental compression in the skull base in the presence of cranial displacement of the dens can be assessed according to characteristic orientation lines.
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but sagittal and coronal secondary reformatted images are needed as horizonal fractures can be easily missed on axial sections. Fractures of the dens axis are classified according to the Classification of Anderson and D’Alonzo. However, individual authors have called this classification system, which is still widely used, into question: Daffner believes that the type I and II fractures presented in the work of Anderson and D’Alonzo are pseudofractures caused by known normal variations in ossiculum terminale and seen as bright lines at the base of the dens due to the “Mach” effect. He justifies this with the observation that in the further course these fractures were considered “healed” and therefore recommends classifying the type III fractures as axial body fractures. In his experience, true fractures of the dens axis can be divided into injuries deeply situated and close to the base and those high above the base, whereby the fragment may be ventrally or dorsally displaced. The key sign of a dens axis fracture is identification of a fracture line on special anteroposterior dens images and lateral images, possibly with a dorsally displaced dens fragment and a clear increase in the prevertebral soft tissue shadow. To verify the findings, thin-slice (1 mm) axial computed tomography scans reconstructed from raw data in the bone window at the sagittal and coronal level are important. 1.4. Fractures of the arch Fractures of the vertebral arch of the axis (hangman’s fracture, traumatic spondylolisthesis) represent hyperextension distraction fractures (Fig. 1). The classic case of hanging a person with a rope knotted submentally completely ruptures the vertebral disk and ligaments between C2 and C3, with the medulla oblongata and the brainstem tearing suddenly as a result of hyperextension and distraction. In contrast, neurological complications seldom occur as a result of traumatic spondylolisthesis because the spinal column is wide at this point and the fracture itself actually causes decompression (rescuing vertebral arch fracture). The key sign of a hangman’s fracture is a nearly vertical course of the fracture line projecting towards the vertebral arch or the interarticular part of the axis. More rarely this line runs in a coronal plane through the posterior third of the vertebral body, with or without ventral spondylothesis of the second cervical vertebra.
1.3. Fractures of the axis 2. Mechanisms of injury and classification We distinguish between fractures of the arch and the dens axis. The most common causes of fractures of the dens axis are hyperflexion injuries. Only seldom are hyperextension mechanisms responsible for this. Conventional anteroposterior X-rays with the mouth open are usually sufficient for diagnosis. Computed tomography can also be used
Injury to the spine is usually caused indirectly by trauma. Under such circumstances the force to the affected vertebra is exerted from a certain distance. Severity and extent of the damage depend on the degree of force, the position of the body, and the speed of the patient at the time the injury is sustained.
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Fig. 1. (a–c) CT shows anterior arch fracture with rupture of the atlantis transversum ligament of C1. Congenital cleft of the posterior arch due to the sclerotic rim. No fracture of the posterior arch.
2.1. Patterns of injury Numerous different classifications are available for defining spinal injuries. According to Daffner, most spinal fractures occur according to predictable patterns [4]. The radiological changes seen after certain kinds of injuries are similar; these may range, however, from minor soft tissue injuries to severe skeletal injury and ligament ruptures with and without involvement of neural structures. Bony injury possibly only represents the “tip of the iceberg” and may be relatively insignificant in comparison to spinal cord damage. Daffner calls these injury patterns “fingerprints”. Knowledge of the individual kinds of injuries, therefore, facilitates analysis and diagnostic interpretation of the actual and the anticipated damage. Essentially there are four injury patterns: • Flexion injury. • Extension injury.
• Rotation injury. • Shear injury. These injury patterns can present individually or in combination and the various sections of the spine are affected at varying frequencies. As already mentioned, as a result of their varying spatial orientation and structure within the three sections of the spine, the small vertebral articulations represent important stabilizing structures and are involved in: • Extension injuries, which occur mainly in the upper segments of the cervical spine, usually C2. • Flexion injuries, which occur more often in the lower segments of the cervical spine, usually C5 and below. • Burst fractures caused by flexion, rotation, or shear forces, which occur mainly in the thoracic and lumbar portions of the spine, particularly at the thoracolumbar junction. Compression, flexion, and burst injuries occur more frequently in young people. Older individuals, in contrast, often
U. Heinemann, M. Freund / European Journal of Radiology 58 (2006) 76–88 Table 1 Flexion injury “fingerprints”
Table 3 Rotation injury “fingerprints”
Compression, fragmentation, and burst fractures of the vertebral bodies Teardrop-shaped fragments at the ventral edge of the vertebral bodies Ventral slippage of the vertebrae Disruption in the line of the posterior vertebral bodies Luxated or blocked facet joints
Severe vertebral fragmentation and rotation and dislocation of the fragments (rotation grinding injury) Fractures of the transverse process and/or ribs Fracture or luxation of facet joints and joint laminae Interruption in the line of the dorsal vertebral bodies Circular arrangement of fragments on CT
sustain extension and luxation injury. The authors believe this is a result of the decrease in flexibility, mobility remaining the greatest at the C2 level [4,5]. 2.1.1. Flexion injuries Flexion injuries can be caused at any level of the spine by forward bending force, for example, as a result of indirect dorsal or ventral force to the trunk upon impact to a fixed or solid object. A fall from a considerable height or a swimming accident such as diving into flat water would represent such an injury (Fig. 2). The typical “fingerprints” of flexion injuries are summarized in Table 1. A teardrop fracture represents an instable and therefore very dangerous injury. Typically, a teardrop-shaped fragment of bone breaks off the front edge of the vertebral body, pushing the affected vertebra in a dorsal direction and fracturing the posterior part of the vertebra. 2.1.2. Extension injuries Extension injuries are caused by bending the spine in a dorsal direction as a result of frontal impact of a propelled object or a sudden break in movement by a fixed or solid object, for example, the back colliding against a motorway railing or a tree after being thrown out of a moving vehicle. The typical “fingerprints” of extension injuries are summarized in Table 2. These injuries include fractures of the axis with dorsal displacement of the odontoid process of axis or spondyolysis of C2 caused by cervical hyperextension. Fewer extension injuries occur in the thoracic and lumbar spine than in the cervical spine as movement in those areas is limited by physiologic thoracic kyphosis and the differing orientation of the facet joints there [11].
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occur primarily at the thoracolumbar junction. Strong tearing forces are in play and the vertebra is literally crushed. A heavy blow to the shoulders that compresses the spine while the lower trunk is bent sideways and is twisted laterally represents a typical mechanism, for example, when a person is thrown out of a motor vehicle and crashes against a fixed or solid object (note any bruises or cuts and skin lacerations on the shoulders!). In particular, the thoracolumbar junction is affected and severe neurological damage is usually found. The radiological fingerprints are summarized in Table 3. 2.1.4. Shear injuries Shear injuries are the result of horizontal or diagonal force when axial force does not play a role. These injuries can occur in combination with flexion or extension injuries. Typically they occur in forest workers who have been hit by a falling tree or if a person is pinned between two solid objects, such as truck and loading ramp. The typical “fingerprints” for shear injuries are summarized in Table 4. Table 4 Shear injury “fingerprints” Distraction and luxation in a lateral direction “Tilted” appearance Fractures of the transverse process or ribs Diagonal, “tilted” arrangement of the fragments on CT Table 5 Signs of instability on the front, middle, and back parts of the spine as indications for injury of another part Column
Sign of instability
Front
2.1.3. Rotation injuries Rotation injuries are sustained by an abnormal force of torsion to the spine, where rotational movement is more restricted than extension or flexion. Because of the form and changing orientation of the small vertebral joints, torsional rigidity increases at Th7/8 in a caudal direction. Torsion rigidity is greatest at the Th12/L1 segment. Thus, rotation injuries
Teardrop break of the posterior longitudinal ligament Compression >50% Tilt of the vertebral bodies >11◦ with respect to neighboring segments
Middle
Irregular conture along the dorsal edge of the vertebrae (“instability line”) Translation of the dorsal edge >3.5 mm Decrease in height of the posterior wall of the vertebral bodies Displacement of the vertebral arch pedicles, or laminae on anteroposterior images
Table 2 Extension injury “fingerprints”
Back
Displacement and divergence of the spinous process Fracture of posterior elements Lateral displacement of the articular process Facet displacement >5 mm Facet articulation <50% Facet luxation or lock
Enlarged disk space below the injury Triangular break off the upper ventral corner of the vertebral body Dorsal spondyloisthesis Fracture of the vertebral arch
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Fig. 2. (a–c) The lateral plain film demonstrates a flexion-compression fracture of L1. The lesion looks unstable therefore CT is mandatory. CT shows a intraspinal fragment with severe compression of the dural sac. The lateral plain film demonstrates, that the height loss of L1 is nearly diminished after surgery.
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2.2. Concomitant injuries Spinal injuries may be accompanied by other severe injuries. 2.2.1. Vascular injuries in the neck A study group in Germany investigated by Doppler ultrasound the blood vessels in the necks of 60 patients who had suffered head and brain trauma and/or fracture of the cervical spine. Concomitant injury to the blood vessels in the neck could only be excluded in two patients by this modality. Three patients developed severe cerebral ischemia: in one patient this was the result of left internal carotid artery dissection, which could only be identified in the early phase by ultrasound; in another patient, Doppler ultrasound demonstrated persisting internal carotid artery and vertebral artery occlusion; and in the third patient, outcome was fatal as a result of thrombosis and vertebral and basilar arteries after traumatic cervical spine injury. Of 57 patients without any clinical signs of vascular damage, Doppler ultrasound detected changes mainly in the vertebrobasilar arteries in three patients with head injuries (11%) and in six patients with cervical spine or combined head and neck injuries (20%). The authors conclude that injury to the vessels in the neck represents a neglected complication in diagnosing head injury or traumatic injury of the cervical spine [6]. 2.2.2. Intraabdominal injuries Rabinovici et al. [7] examined 258 patients who had suffered blunt spinal trauma and fractures to the lumbar spine. Most of the injuries had been sustained in motor vehicle accidents. Often fractures of the lumbar spine were observed at multiple levels. In 26 patients concomitant intraabdominal injuries were diagnosed. 2.2.3. Fractures of the cervical spine in traumatic head and brain injury Fractures of the cervical spine are present in 4–8% of patients who have suffered head and brain trauma [8]. Accident victims with head injuries and those who have a Glasgow Outcome Score of 8 or below are at greatest risk of having cervical spine fracture, too. An extraordinarily high number of these patients also present with a mechanically instable fracture of the upper cervical spine and spinal cord injury. 2.2.4. Plexus brachialis injuries In 12% of patients with spinal injury, injuries of the plexus brachialis are found as well [9]. Thus, for certain traumatic mechanisms and injury patterns an active search for accompanying signs is required and additional imaging methods should be implemented to exclude further complications. 2.3. Traumatic spinal injury in children Mistakes continue to be made in the assessment of the spine in children who have suffered trauma, and these mis-
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takes are often the result of two problems (Table 5). The consequence is that radiological findings are overinterpreted and, subsequently, treatment is inadequate [10]. 2.3.1. Frequency and localization of spinal injuries in children In general, spinal injuries occur less frequently in children than in adults because of the anatomical, biomechanical, and physiological differences in the skeleton during growth. Most often, the upper segments of the cervical spine are affected after head and brain trauma [10]. In the opinion of some authors, this has to do with the particular elasticity of the connective tissue, the flexibility of the axial skeleton and muscular system, the compressibility of the bones in children due to the lower mineral content, and the difference in the size relationship between body and head. According to these authors, only 2–5% of all spinal injuries occur in children [11,12]. 2.3.2. Practical procedures A neurosurgical study published in 2002 recommends the following procedure for diagnosing traumatic spinal and spinal cord injury in children: • In children who are awake, oriented, and not intoxicated, who do not demonstrate any neurological deficit, or do not present with torticollis or show painful distraction trauma, X-rays are not required to exclude cervical spinal injury. • In children who are not completely conscious or who are disoriented or intoxicated, who demonstrate neurological deficit, torticollis, or painful distraction trauma, conventional anteroposterior and lateral X-rays are required. In addition, the dens, specifically, should be X-rayed in children older than 9 years. • It is sensible to perform computed tomography to exclude occult fractures at the level of any anticipated injury to the nerves or to image those regions that cannot be adequately rendered by conventional imaging techniques. • Functional images are recommended to identify instable ligament injuries. • With MRI, spinal cord and nerve root injuries as well as damage to the capsular ligaments can be identified, and this technique plays an important role in SCIWORA (see next section). Furthermore, MRI can provide prognostic information. Some authors are of the opinion that a broader indication for conducting supplementary CT of the cervical spine after head injury in children would considerably reduce the number of conventional comprehensive X-ray studies needed to exclude cervical spine injury [13]. 2.3.3. Spinal cord injury without radiographic abnormalities (SCIWORA) 2.3.3.1. Pathogenesis. In up to 50% of children presenting with severe neurological symptoms after trauma, no abnormal findings are observed on X-ray. Orhun et al. [14] reported
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the case of a 4-year-old polytraumatized girl whose neurological condition worsened in the course of treatment although findings were normal according to conventional radiographic studies. Using MRI, the authors found intramedullary signal changes at the Th11-L3 level. Thus, they maintain that for careful neurological diagnosis, an MRI study should definitely be carried out to rule out any uncertainty and to identify any spinal cord injuries as early as possible. In the authors’ opinion the cause of such injuries is the considerable flexibility of the spine and the expansibility of the capsular ligament structures in children, in contrast to spinal cord, nerve roots, and blood vessels, which are, relatively speaking, more fixed and which can thus be distended and more easily injured. In some cases, however, neurological deficit may persist, with consequences as severe as paraplegia. 2.4. Imaging procedures 2.4.1. Conventional X-rays In most hospitals conventional X-rays are still the first radiological diagnostic procedure to be conducted. X-rays quickly provide information about whether an injury is present, give a comprehensive representation of a large section of the axial skeleton, and – although to a limited degree – help assess the extent of injury (Fig. 3, Table 6). To examine sections of the spine that for anatomical reasons cannot be viewed without also visualizing the overlying structures, CT should be performed to exclude fracture. Relatively frequently, other injuries have been sustained in the axial skeleton although only one is initially apparent. Thus, the examiner should always search for multi-level injury [19]. On lateral images of the cervical spine, the distance between the posterior wall of the pharynx to the lower anterior edge of the axis is about 7 mm (retropharyngeal space). The distance between the back of the trachea and the lower anterior edge of C6 (retrotracheal space) is about 22 mm in adults and 14 mm in children. On lateral images of the cervical spine usually only the intervertebral joint space C2/3 is not visible. If any of the small intervertebral joint spaces C3/4 to C6/7 is not freely projected or if the joint at C2/3 is visible (imaging in standard position!), it must be assumed that the joint is displaced or deformed and a further CT or MRI study must be conducted. Lateral images of the cervical spine are also suitable for identifying blocked small intervertebral joints, which can be present on only one or on both sides (Fig. 4). This is caused by flexion movements. Malfunction of the ligament–bone complex is the result of a force over time: if the rate of the force is slow, bone function usually fails; in the case of a short, strong force, the ligament is more likely to rupture [17]. If the articulation is not intact, physiological function of the ligaments cannot be maintained.
Fig. 3. (a and b) The a.-p. plain film demonstrates a multi-fragment flexioncompression fracture. CT clearly demonstrates the dislocation of the fragments.
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Table 6 Problems in the assessment of spinal injuries in children Problem
To be observed for correct diagnosis
Lack of familiarity with the special anatomical features (articulation spaces during growth) of the axial skeleton in children
Articulation spaces during growth are automatically found at expected places, marked by sclerotic margins. Fractures, in contrast, occur at unexpected sites. The margins are irregular and not sclerotic Vertebral displacement of up to 3 mm is normal (step phenomenon along the line of the dorsal vertebral bodies in adolescents on images of the cervical spine) and should not be considered luxation; the distance between the atlas and the dens can be up to 4 mm in children
Danger of overlooking injuries that could possibly cause considerable neurologic damage
Fig. 4. (a and b) The lateral plain film demonstrates subluxation of the small articula facets after distraction and rotation injury. Disturbance of the dorsal alignment. Edema and hematoma of the dorsal cervical soft tissues (T2-weighted sequences).
Table 7 Conventional X-rays in spinal injury Projection
Assessment
Lateral projection
Assessment of the dorsal edge, decreases in height of the vertebral bodies, spinal laminar line, joint process line Indications for injury by assessing deviations of the dorsal/spinous process after rotation injury, increased distance between the peduncles after burst injury Visualization of joint process fractures or unilateral luxation fractures, particularly in the cervical spine Image of the cervicothoracic junction from C7-Th2, which is nearly impossible to assess on lateral projections Diagnosis of articulation disorders
Anteroposterior projection Transverse projection Special projections (“Swimmer” projection) Functional images in positions of ante- and retroflexion
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Stress/strain images (functional images of the cervical and lumbar spine) are taken in a lateral projection at maximal flexion and/or extension. A clear indication for radiological diagnosis is given when the physician suspects that the articulation of the vertebral segments has loosened. This applies in particular for instable dorsal ligament injuries such as hyperflexion–subluxation distorsion. We perform these imaging studies when the X-ray survey does not show any instability injury or luxation, when the patient can sit or stand in an upright position, and when no neurologic deficit has been observed. In this case, the patients are asked to bend or stretch the neck as far as possible until they feel pain. A general recommendation of how to proceed in individual patients cannot be made: For this, the acute situations encountered in daily routine are too different and the medical and legal aspects involved are too great and too complex. 2.4.2. Computed tomography Detailed information about spinal canal involvement, the presence of interspinal fragments, or constriction of the epidural space can be provided in part by lateral tomography, if still in use, and especially by CT studies (Figs. 1–3). Vertebral bodies, intervertebral arches, small intervertebral joints, intervertebral disks, spinal canal, and paravertebral spaces can be ideally and freely visualized. For surgical treatment of vertebral injury, the images must include the traumatized segment and also the intact and neighboring cranial and caudal vertebrae. These include: • Unrestricted/clear representation of the epistropheus, for example, to exclude a fracture when a typical bright horizonal line at the base of the dens simulates a fracture when the posterior arch of the atlas is superimposed on target images (Mach effect). • Better representation of the transition from the cervical to the thoracic spine. • To image the pars interarticularis in the lumbar spine if spondylolysis is suspected. 2.4.3. CT instead of X-ray studies For injuries of the cervical spine, Griffen et al. [18] maintain that CT should be performed instead of X-ray studies. They established that 35% of cervical spinal injuries requiring treatment were overlooked on X-rays but identified on CT images. According to the reports of Imhof and Fuchsjager [19], conventional X-ray techniques provide up to 57% falsenegative results in the diagnosis of cervical spinal injuries. In contrast, Besman et al. [20] concluded from their study that imaging of the cervical spine at three levels provided a high sensitivity and specificity for detecting injuries. In only three of 549 patients (0.5%) were findings on the cervical spine X-rays normal although significant injury had been sustained. The authors emphasize, however, that this is precisely why a CT study of the cervical spine should be conducted when X-ray findings are normal and the nature of the acci-
dent and the clinical symptoms suggest a more serious degree of injury. This also corresponds to our experience and thus we have a broad definition for when CT imaging of the craniocranial and cervicalthoracic areas of the spine should be performed if the accident causing the injury would suggest more serious injury. 2.4.4. MSCT or conventional X-rays in patients with multiple injuries Because positioning is more difficult in accident victims and considering problems involved in obtaining useful images, often resulting in faulty radiographs and ultimately an increased radiation exposure, and also with respect to the considerable amount of time involved for diagnosis, new technique concepts are being introduced for diagnosis under acute conditions in patients with multiple injuries, specifically multi-slice spiral CT (MSCT) [21]. In some clinics, including ours, MSCT has already been integrated as part of an interdisciplinary program. The following studies have been carried out to address the question of whether conventional X-rays or a CT/MSCT should be performed first. According to a study by Rieger et al. [22], early implementation of MSCT reduces the time needed for diagnosis in polytraumatized patients by about half. Wintermark et al. [23] determined average times of 33 and 40 min for X-ray and MSCT, respectively, for examination and diagnosis. The effective radiation dose was 5.36 mSv for X-ray studies and 19.42 mSv for thoracoabdominal MSCT [23], i.e., a threefold higher dose of radiation for MSCT. In the study by Wintermark et al. [23] the cost of conventional X-ray examinations was $145 per patient and for MSCT $880. Blackmore et al. [24] examined the cost effectiveness in using conventional X-rays and additional use of CT in patients who had previously been divided into groups at high risk, normal risk, and low risk for sustaining fractures of the cervical spine. They determined that performing CT examinations in patients in the normal and high risk groups can identify the consequences and complications of injury at an early stage and that in this way costs, which are sometimes considerable, can be saved. In their study, Wintermark et al. [23] found a sensitivity of 97.2% for MSCT and 33.3% for X-ray in detecting instable fractures. For this reason, these authors also consider MSCT to be more suitable than X-rays for identifying spinal injuries and, because of the greater diagnostic accuracy and sensitivity in detecting instable fractures and also with respect to the documentation of concomitant injuries, recommend MSCT as a stand-alone modality for patients with multiple injuries. As soon as multiple injuries have been diagnosed according to a checklist, which includes accident mechanisms, vital signs, and injury patterns, and with the exception of an optional thoracic X-ray in cases of respiratory insufficiency, conventional X-rays can be dispensed with and a whole-body MSCT carried out directly after the vital functions have stabilized and abdominal ultrasound has been performed for
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orientation purposes and to exclude free fluid. This procedure is also followed at our clinic in cases of suspected polytrauma: after abdominal ultrasound and stabilization of the vital functions, we, in collaboration with the surgeon and anesthetist, quickly decide upon and carry out a CT examination. If the contents of the spinal canal are involved, the spine should be directly examined by MRI if a clear diagnosis cannot be made by CT and decisions about therapy depend on this. This involves considerable effort but today MRI examinations can also be performed in polytrauma patients.
2.4.6. Magnetic resonance imaging With MRI, the spine and contents of the spine can be directly and noninvasively imaged. This technique plays a decisive role in:
2.4.5. Myelography As a method for diagnosing acute injuries of the spine, myelography has been largely replaced by MRI [4]. In the past myelography served to identify CSF flow disorders in interspinal fragments, dural rupture, and nerve root ruptures, usually in combination with a subsequent CT study. Ultimately, the patient positioning required for spinal canal puncture renders this examination very difficult to carry out in multiply injured patients and the information for diagnosis that can be provided by this technique is relatively insignificant. Today the only place for myelography in trauma patients is, in exceptional cases, for clarification in suspected impending paraplegia or to determine the location of an intraspinal injury for surgical planning if MRI is contraindicated.
In addition to standard contraindications for MRI, e.g., cardiac pacemakers, trochlear implants, or ferromagnetic intracranial aneursymal clips, this technique cannot be nonrestrictively employed in acute spinal injuries for other reasons as well. In patients with multiple injuries the circulation is also often unstable. Thus MRI is less suitable in these patients as the spatial conditions would make it difficult to carry out cardiopulmonary resuscitation measures if necessary. Furthermore, the equipment required for adequate cardiocirculatory monitoring cannot always be implemented in a magnetic environment. Today, however, equipment lacking ferromagnetic properties is available and it is becoming increasingly possible to respirate polytraumatized patients during the MRI examination.
• Assessing the spatial relationship between bony fragments and myelon compression. • Visualizing concomitant intracanalicular and paravertebral soft tissue and vascular or nerve injuries. • Visualizing primary and secondary spinal cord changes in the acute and postacute phases.
Fig. 5. (a and b) T1-weighted sequence shows traumatic disc injury of the segment C3/4 and rupture of the anterior and posterior ligament as well as of the interspinosus ligament. T2-weighted sequence shows high signal intensity of the spinal cord due to intramedullary edema due to contusion of the spinal cord.
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Table 8 MRI protocol for spinal injuries Sagittal T1-weighted sequences to demonstrate the anatomy Sagittal, fat-suppressed T2-weighted TSE/FSE sequences to image the total spine in order to detect edema or the presence of blood in any section of the spine and to localize and assess the extent of injury in one session Sagittal GRE sequences to image the blood and blood vessels and to better distinguish between osteophytes and disks Axial T1-weighted sequences to further assess the epidural space, the spinal cord, and neuroforamina in areas of certain abnormal findings on sagittal sections
The standard sequences used to examine patients with spinal injuries are (Table 8): • Sagittal and axial T1-weighted spin echo sequences to evaluate the anatomy. • Sagittal T2-weighted fluid-sensitive turbo SE sequences with and without fat suppression, making it easier to detect pathological changes in the presence of persistent, concomitant edema in these patients.
• Susceptibility-sensitive, blood-sensitive gradient echo sequences that can also visualize the ligaments, distinguish between traumatic vertebral prolapse and osteophytes, and can render spinal cord anatomy and the blood vessels (Table 8). At our institution, the protocol outlined in Table 7 is carried out in cases of spinal trauma. 2.5. Spinal cord injury Detecting spinal cord injury (concussion/contusion of the spinal cord, central cord syndrome, spinal cord hematoma) in conjunction with intramedullary edema (Fig. 5) or bleeding or a combination of these two components has particular significance for prognosis and further outcome. Progrnosis in terms of recovery from neurological complications is worse in patients in whom bleeding is present than in those with only edema. Generally, a true contusion of the spinal cord or transient traumatic spinal cord apraxia with or without a weak, hyperintense signal on T2-weighted images is completely reversible within a maximum of 72 h. In spinal cord
Fig. 6. (a and b) Rupture of the anterior longitudinal and interspinosus ligament together with edema and hematoma.
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contusion with spinal cord edema MRI signal recovery is slower and may indicate remaining neurological deficit. In contrast, hematoma in the spinal cord (weak signal on T2weighted and gradient echo contrast) shows only little or no signal recovery over time (Table 8). 2.6. Ligament injuries Additionally, MRI can detect both unexpected ligament injuries and ligament injuries beyond the extent of those anticipated, particularly when conventional X-ray findings were normal. Here, T2-weighted images are most suitable, showing a disruption in the course of the ligament structure, which otherwise lacks a signal, in combination with a signal increase that may involve neighboring sections (Fig. 6). MRI studies show that in thoracolumbar ligament injuries conforming to the aforementioned frequency of thoracolumbar flexion injuries in conjunction with distraction of the dorsal parts of the vertebrae, the following ligaments are affected with decreasing frequency: • • • •
Inter- and supraspinal ligaments. Flaval ligaments. Posterior longitudinal ligament. Anterior longitudinal ligament.
2.7. Traumatic vertebral disk prolapse It is equally important to identify traumatic vertebral disk prolapse, which by compressing the spinal cord or nerve roots can cause corresponding neurologic symptoms that urgently require surgical treatment. Vertebral disk prolapse is observed particularly frequently in patients who have sustained uni- or bilateral facet joint subluxation injury. To better distinguish between the vertebral disks and osteophytes we recommend using gradient echo sequences where the loss of signal intensity in bone represents a significant contrast to the relatively high signal of the vertebral disks (Fig. 5). 2.8. Epidural bleeding Last but not least, epidural bleeding can be detected by MRI. As a result of the tight binding of the posterior longitudinal ligament of the spine with the ventral dura and the disk, hematomas form typically in the dorsal epidural space. This can develop acutely after trauma or be delayed and in 50% of patients without any evidence of injury to the spine. In the acute phase (1–3 days) a hematoma is hypo- or isointense to the spinal cord on contrast-enhanced T1-weighted images and shows a signal increase on T2-weighted images. Subsequently, as a result of oxidation processes in the hemoglobin and the development of blood degradation products, the total signal on T2-weighted images decreases and the peripheral signal increases both on T1- and T2-weighted images. On gradient echo sequences, a strong signal decrease is noted as a sign of the bleeding.
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3. Summary Fractures of the spine account for 3–6% of all injuries of the skeleton and occur more frequently in individuals between 20 and 50 years of age. Most fractures involve the thoracic and lumbar spine and often are associated with severe concomitant injuries (spinal cord, blood vessels, intrathoracic or intraabdominal organs, head-brain trauma) [6,7,9]. In general, spinal injuries occur less frequently in children than in adults because of the anatomical, biomechanical, and physiological differences in the skeleton during growth (2–5% of the total) [11,12]. If no injuries are visible on Xrays in children, an MRI study should be conducted quickly in order to exclude spinal cord injury (SCIWORA). The diagnosis and treatment of spinal injuries presents all specialists with a great challenge, particularly in unconscious patients and patients with multiple injuries in whom the extent of injury is not known when they are admitted to the hospital. At many centers, conventional X-rays at two levels and possibly special images, are still primarily taken to detect and diagnose injuries of the spine. In interpreting the findings, it is useful to know the cause and mechanism of the injury as these injuries leave certain “fingerprints” on the axial skeleton. These “fingerprints” facilitate diagnosis, i.e., analysis of the visible and anticipated injuries. The majority of authors are of the opinion that CT should be used instead of conventional X-rays, particularly in patients at normal and high risk for fractures. In patients with multiple injuries, rapid diagnosis – which begins when they enter the shock room – is essential for successful therapy. At many centers multi-slice spiral CT has already been integrated into diagnostic workup in the shock room and therefore conventional diagnostic X-ray studies can be dispensed with in these cases. The complete assessment of spinal trauma includes Xrays to determine the level of the injury and also the use of CT and MRI. With CT the extent of the injury can be documented, including the dorsal parts of the vertebrae. MRI serves to determine whether concomitant soft tissue injuries have been sustained, including the vertebral disks, ligaments, epidural space, and vessels, and also to directly assess the spinal cord. Furthermore, in cases of unexplained persisting clinical symptoms (e.g., SCIWORA), MRI is very useful for excluding epidural hematoma, traumatic disk hernation, or spinal cord injuries.
References [1] Greenspan A. Orthopedic radiology. A practical approach. Philadelphia: Lippincott-Raven; 2000. [2] Roberstson A, Branfoot T, Barlow IF, Giannoudis PV. Spinal injuries patterns resulting from car and motorcycle accidents. Spine 2002;27:2825–30. [3] Hawighorst H, Berger MF, Moulin P, Z¨ach GA. MRT bei spinoligament¨aren Verletzungen. Orthop¨ade 2001;30:565–79.
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[4] Daffner RH. Imaging of vertebral trauma. Philadelphia: LippincottRaven; 1996. [5] Kiwerski J. The influence of the mechanism of cervical spine injuries on the degree of spinal cord lesion. Paraplegia 1991;29:531–6. [6] Rommel O, Niedeggen A, et al. Carotid and vertebral artery injury following severe head or cervical spine injury. Cerebrovasc Dis 1999;9:202–9. [7] Rabinovici R, Ovadia P, Mathiak G, et al. Abdominal injuries associated with lumbar spine fractures in blunt trauma. Injury 1999;30: 471–4. [8] Holly LT, Kelly DF, et al. Cervical spine trauma with moderate and severe head injury: incidence, risk factors, an injury characteristics. J Neurosurg 2002;96:285–91. [9] Webb JC, Munishi P, et al. The prevalence of spinal trauma associated with brachial plexus injuries. Injury 2002;33:587–90. [10] Roche C, Carty H. Spinal trauma in children. Pediatr Radiol 2001;31: 677–700. [11] Patel JC, Tepas JJ, et al. Pediatric cervical spine injuries: defining the disease. J Pediatr Surg 2001;36:373–6. [12] Reynolds R. Pediatric spinal injury. Curr Opin Pediatr 2000;12: 67–71. [13] Keenan HT, Hollingshead MC, et al. Using the CT of the cervical spine for early evaluation of pediatric patients with head trauma. Am J Roentgenol 2001;177:1405–9.
[14] Orhun H, Saka G, Berkel T. Carotid and vertebral injury following severe head or cervical spine trauma. Acta Orthop Traumatol Turc 2002;36:268–72. [17] Maiman DJ, Yoganandam N. Biomechanics of cervical spine trauma. Clin Neurosurg 1991;37:543–70. [18] Griffen MM, Frykberg ER, et al. Radiographic clearance of blunt cervical spine injury: plain radiograph or computed tomography scan? J Trauma 2003;55:222–6. [19] Imhof H, Fuchsjager M. Traumatic injuries: imaging of spinal injuries. Am J Roentgenol 2002;12:1262–72. [20] Besman A, Kaban J, et al. False negative plain cervical spine X-rays in blunt trauma. Am Surg 2003;69:1010–4. [21] Messmer P, L¨ow R, Jacob AL. Interdisziplin¨ares Management von polytraumatisierten Patienten: Beitrag der Radiologie. Radiologie 2003;3:275–95. [22] Rieger M, Sparr H, et al. Modern CT diagnosis of acute thoracic and abdominal trauma. Anaesthesist 2002;51:835–42. [23] Wintermark M, Mouhsine E, et al. Thoraco-lumbar spine fractures in patients who have sustained severe trauma: depiction with multidetector row CT. Emerg Radiol 2003;3:681–6. [24] Blackmore CL, Ramsey SD, et al. Cervical spine screening with CT in trauma patients: a cost-effectiveness analysis. Radiology 1999;212: 117–25.
Diagnostic strategies in spinal trauma Uwe Heinemann, Michael Freund ∗ Institut f¨ur Radiologie und Neuroradiologie, Klinikum Aschaffenburg, Am Hasenkopf 1, 63739 Aschaffenburg, Germany Received 25 November 2005; received in revised form 28 November 2005; accepted 1 December 2005
Abstract Spinal injuries may result in severe neurological deficits, especially if nerve roots or even the spinal cord are affected. Besides presenting the important anatomical and technical basis underlying the imaging findings of spinal injuries, the trauma mechanisms and the resulting injuries are discussed. Based on the current literature and recommendations of scientific organizations, an approach is provided to the radiologic work up of spinal trauma. The different imaging modalities are presented. Advantages and disadvantages of the methods are discussed. © 2005 Elsevier Ireland Ltd. All rights reserved. Keywords: Spinal trauma; Radiology; Spine; Computed tomography; Magnetic resonance imaging
1. Introduction Injuries to the axial skeleton such as fracture, dislocation, and soft tissue injury can affect the entire spine. The range of consequences of such injuries extend from minor pain without neurological deficit to severe paralysis and even death. Spinal fractures, mainly of the thoracic and lumbar spine, represent 3–6% of all skeletal injuries. They occur most frequently in individuals between the ages of 20 and 50 years [1]. The risk of damage to the spinal cord is greatest in cervical spine injuries as the spine is narrower there and movement is less restricted in the cervical spine than in the thoracic and lumbar portions. The most common causes of these injuries are traffic and sport accidents (e.g., scuba diving and skying) and falls from considerable heights. The results of an English study showed that: • Patients presenting after a motorcycle or automobile accident are most often men (motorcycle: 88.9%; automobile; 60.6%) of a young age (average age 30.2 and 37.8 years, respectively).
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Corresponding author. Tel.: +49 6021 323100; fax: +49 6021 323105. E-mail address: [email protected] (M. Freund). 0720-048X/$ – see front matter © 2005 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.ejrad.2005.12.007
• Among motorcyclists, the thoracic spine was affected most often (54.8%), among automobile drivers, the cervical spine (50.7%). • In general, motorcyclists sustain more serious injuries than automobile drivers, mortality is higher, and they present primarily with injuries to the extremities and mainly with flexion injuries of the thoracic spine. • Automobile drivers more frequently present with injuries to the cervical spine and show a higher rate of neck and face injuries. This is associated with the fixation of the chest and abdomen by a safety belt [2]. For injuries of the axial skeleton, the tasks of the radiologist include: • Confirming the diagnosis of an injury using appropriate diagnostic methods. • Diagnosing bony, chondral, ligamentous, articular, and any possible neural injuries as well as associated injuries to the neighboring soft tissues. • Establishing whether an injury has affected the stability of the spine. • Discussing diagnosis and further treatment with all physicians involved. • Documenting the results of treatment and assessing the course of the healing process.
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1.1. Traumatic injury to the cranial articulations 1.1.1. Special structural features There are no vertebrae between the occiput, atlas and axis, enabling greater and very complex movement in this spinal segment. The atlanto-occipital articulation is mainly stabilized by the articular capsule and the anterior and posterior atlantooccipital ligaments but also by the cruciform ligament of atlas (transverse ligament and apical dental ligament). The alar ligaments also prevent excessive movement between the atlas and the axis [3]. 1.2. Fractures of the atlas The most common cause of burst fractures of the atlas is collision injury (traffic accidents, swimming and diving accidents). The vertebral body is missing in the atlas, rendering the ring of the atlas susceptible for typical burst fractures after axial trauma (Jefferson fracture). Here, the most important stabilizing element for atlanto-axial articulation, the transverse ligament, can rupture. However, osteoligamentous ruptures of the transverse ligament at the point of attachment to the lateral mass of atlas occur more frequently than purely ligamentous ruptures. As a consequence, the tooth of axis no longer proceeds dorsally and due to ventral slippage from C1 to C2 can deviate dorsally into the spinal column and compress the spinal cord. The atlantodental articulation is then instable and through anteflexion causes ventral atlas dislocation. The normal distance between the dens and the atlas is <3 mm in adults and <4 mm in children. The key sign of a burst fracture of the atlas is lateral displacement of the lateral mass of atlas towards the dens axis on images taken with the mouth open. A lateral deviation of >7 mm indicates a ligamentous rupture and instability. Lateral X-rays of the cervical spine, including the skull base, are particularly important for evaluating a vertical subluxation involving the atlantooccipital articulation and displacement of the dens axis into the posterior cranial cavity because of the threat of injury to the medulla oblongata and the spinal cord. Atlanto-dental compression in the skull base in the presence of cranial displacement of the dens can be assessed according to characteristic orientation lines.
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but sagittal and coronal secondary reformatted images are needed as horizonal fractures can be easily missed on axial sections. Fractures of the dens axis are classified according to the Classification of Anderson and D’Alonzo. However, individual authors have called this classification system, which is still widely used, into question: Daffner believes that the type I and II fractures presented in the work of Anderson and D’Alonzo are pseudofractures caused by known normal variations in ossiculum terminale and seen as bright lines at the base of the dens due to the “Mach” effect. He justifies this with the observation that in the further course these fractures were considered “healed” and therefore recommends classifying the type III fractures as axial body fractures. In his experience, true fractures of the dens axis can be divided into injuries deeply situated and close to the base and those high above the base, whereby the fragment may be ventrally or dorsally displaced. The key sign of a dens axis fracture is identification of a fracture line on special anteroposterior dens images and lateral images, possibly with a dorsally displaced dens fragment and a clear increase in the prevertebral soft tissue shadow. To verify the findings, thin-slice (1 mm) axial computed tomography scans reconstructed from raw data in the bone window at the sagittal and coronal level are important. 1.4. Fractures of the arch Fractures of the vertebral arch of the axis (hangman’s fracture, traumatic spondylolisthesis) represent hyperextension distraction fractures (Fig. 1). The classic case of hanging a person with a rope knotted submentally completely ruptures the vertebral disk and ligaments between C2 and C3, with the medulla oblongata and the brainstem tearing suddenly as a result of hyperextension and distraction. In contrast, neurological complications seldom occur as a result of traumatic spondylolisthesis because the spinal column is wide at this point and the fracture itself actually causes decompression (rescuing vertebral arch fracture). The key sign of a hangman’s fracture is a nearly vertical course of the fracture line projecting towards the vertebral arch or the interarticular part of the axis. More rarely this line runs in a coronal plane through the posterior third of the vertebral body, with or without ventral spondylothesis of the second cervical vertebra.
1.3. Fractures of the axis 2. Mechanisms of injury and classification We distinguish between fractures of the arch and the dens axis. The most common causes of fractures of the dens axis are hyperflexion injuries. Only seldom are hyperextension mechanisms responsible for this. Conventional anteroposterior X-rays with the mouth open are usually sufficient for diagnosis. Computed tomography can also be used
Injury to the spine is usually caused indirectly by trauma. Under such circumstances the force to the affected vertebra is exerted from a certain distance. Severity and extent of the damage depend on the degree of force, the position of the body, and the speed of the patient at the time the injury is sustained.
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Fig. 1. (a–c) CT shows anterior arch fracture with rupture of the atlantis transversum ligament of C1. Congenital cleft of the posterior arch due to the sclerotic rim. No fracture of the posterior arch.
2.1. Patterns of injury Numerous different classifications are available for defining spinal injuries. According to Daffner, most spinal fractures occur according to predictable patterns [4]. The radiological changes seen after certain kinds of injuries are similar; these may range, however, from minor soft tissue injuries to severe skeletal injury and ligament ruptures with and without involvement of neural structures. Bony injury possibly only represents the “tip of the iceberg” and may be relatively insignificant in comparison to spinal cord damage. Daffner calls these injury patterns “fingerprints”. Knowledge of the individual kinds of injuries, therefore, facilitates analysis and diagnostic interpretation of the actual and the anticipated damage. Essentially there are four injury patterns: • Flexion injury. • Extension injury.
• Rotation injury. • Shear injury. These injury patterns can present individually or in combination and the various sections of the spine are affected at varying frequencies. As already mentioned, as a result of their varying spatial orientation and structure within the three sections of the spine, the small vertebral articulations represent important stabilizing structures and are involved in: • Extension injuries, which occur mainly in the upper segments of the cervical spine, usually C2. • Flexion injuries, which occur more often in the lower segments of the cervical spine, usually C5 and below. • Burst fractures caused by flexion, rotation, or shear forces, which occur mainly in the thoracic and lumbar portions of the spine, particularly at the thoracolumbar junction. Compression, flexion, and burst injuries occur more frequently in young people. Older individuals, in contrast, often
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Table 3 Rotation injury “fingerprints”
Compression, fragmentation, and burst fractures of the vertebral bodies Teardrop-shaped fragments at the ventral edge of the vertebral bodies Ventral slippage of the vertebrae Disruption in the line of the posterior vertebral bodies Luxated or blocked facet joints
Severe vertebral fragmentation and rotation and dislocation of the fragments (rotation grinding injury) Fractures of the transverse process and/or ribs Fracture or luxation of facet joints and joint laminae Interruption in the line of the dorsal vertebral bodies Circular arrangement of fragments on CT
sustain extension and luxation injury. The authors believe this is a result of the decrease in flexibility, mobility remaining the greatest at the C2 level [4,5]. 2.1.1. Flexion injuries Flexion injuries can be caused at any level of the spine by forward bending force, for example, as a result of indirect dorsal or ventral force to the trunk upon impact to a fixed or solid object. A fall from a considerable height or a swimming accident such as diving into flat water would represent such an injury (Fig. 2). The typical “fingerprints” of flexion injuries are summarized in Table 1. A teardrop fracture represents an instable and therefore very dangerous injury. Typically, a teardrop-shaped fragment of bone breaks off the front edge of the vertebral body, pushing the affected vertebra in a dorsal direction and fracturing the posterior part of the vertebra. 2.1.2. Extension injuries Extension injuries are caused by bending the spine in a dorsal direction as a result of frontal impact of a propelled object or a sudden break in movement by a fixed or solid object, for example, the back colliding against a motorway railing or a tree after being thrown out of a moving vehicle. The typical “fingerprints” of extension injuries are summarized in Table 2. These injuries include fractures of the axis with dorsal displacement of the odontoid process of axis or spondyolysis of C2 caused by cervical hyperextension. Fewer extension injuries occur in the thoracic and lumbar spine than in the cervical spine as movement in those areas is limited by physiologic thoracic kyphosis and the differing orientation of the facet joints there [11].
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occur primarily at the thoracolumbar junction. Strong tearing forces are in play and the vertebra is literally crushed. A heavy blow to the shoulders that compresses the spine while the lower trunk is bent sideways and is twisted laterally represents a typical mechanism, for example, when a person is thrown out of a motor vehicle and crashes against a fixed or solid object (note any bruises or cuts and skin lacerations on the shoulders!). In particular, the thoracolumbar junction is affected and severe neurological damage is usually found. The radiological fingerprints are summarized in Table 3. 2.1.4. Shear injuries Shear injuries are the result of horizontal or diagonal force when axial force does not play a role. These injuries can occur in combination with flexion or extension injuries. Typically they occur in forest workers who have been hit by a falling tree or if a person is pinned between two solid objects, such as truck and loading ramp. The typical “fingerprints” for shear injuries are summarized in Table 4. Table 4 Shear injury “fingerprints” Distraction and luxation in a lateral direction “Tilted” appearance Fractures of the transverse process or ribs Diagonal, “tilted” arrangement of the fragments on CT Table 5 Signs of instability on the front, middle, and back parts of the spine as indications for injury of another part Column
Sign of instability
Front
2.1.3. Rotation injuries Rotation injuries are sustained by an abnormal force of torsion to the spine, where rotational movement is more restricted than extension or flexion. Because of the form and changing orientation of the small vertebral joints, torsional rigidity increases at Th7/8 in a caudal direction. Torsion rigidity is greatest at the Th12/L1 segment. Thus, rotation injuries
Teardrop break of the posterior longitudinal ligament Compression >50% Tilt of the vertebral bodies >11◦ with respect to neighboring segments
Middle
Irregular conture along the dorsal edge of the vertebrae (“instability line”) Translation of the dorsal edge >3.5 mm Decrease in height of the posterior wall of the vertebral bodies Displacement of the vertebral arch pedicles, or laminae on anteroposterior images
Table 2 Extension injury “fingerprints”
Back
Displacement and divergence of the spinous process Fracture of posterior elements Lateral displacement of the articular process Facet displacement >5 mm Facet articulation <50% Facet luxation or lock
Enlarged disk space below the injury Triangular break off the upper ventral corner of the vertebral body Dorsal spondyloisthesis Fracture of the vertebral arch
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Fig. 2. (a–c) The lateral plain film demonstrates a flexion-compression fracture of L1. The lesion looks unstable therefore CT is mandatory. CT shows a intraspinal fragment with severe compression of the dural sac. The lateral plain film demonstrates, that the height loss of L1 is nearly diminished after surgery.
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2.2. Concomitant injuries Spinal injuries may be accompanied by other severe injuries. 2.2.1. Vascular injuries in the neck A study group in Germany investigated by Doppler ultrasound the blood vessels in the necks of 60 patients who had suffered head and brain trauma and/or fracture of the cervical spine. Concomitant injury to the blood vessels in the neck could only be excluded in two patients by this modality. Three patients developed severe cerebral ischemia: in one patient this was the result of left internal carotid artery dissection, which could only be identified in the early phase by ultrasound; in another patient, Doppler ultrasound demonstrated persisting internal carotid artery and vertebral artery occlusion; and in the third patient, outcome was fatal as a result of thrombosis and vertebral and basilar arteries after traumatic cervical spine injury. Of 57 patients without any clinical signs of vascular damage, Doppler ultrasound detected changes mainly in the vertebrobasilar arteries in three patients with head injuries (11%) and in six patients with cervical spine or combined head and neck injuries (20%). The authors conclude that injury to the vessels in the neck represents a neglected complication in diagnosing head injury or traumatic injury of the cervical spine [6]. 2.2.2. Intraabdominal injuries Rabinovici et al. [7] examined 258 patients who had suffered blunt spinal trauma and fractures to the lumbar spine. Most of the injuries had been sustained in motor vehicle accidents. Often fractures of the lumbar spine were observed at multiple levels. In 26 patients concomitant intraabdominal injuries were diagnosed. 2.2.3. Fractures of the cervical spine in traumatic head and brain injury Fractures of the cervical spine are present in 4–8% of patients who have suffered head and brain trauma [8]. Accident victims with head injuries and those who have a Glasgow Outcome Score of 8 or below are at greatest risk of having cervical spine fracture, too. An extraordinarily high number of these patients also present with a mechanically instable fracture of the upper cervical spine and spinal cord injury. 2.2.4. Plexus brachialis injuries In 12% of patients with spinal injury, injuries of the plexus brachialis are found as well [9]. Thus, for certain traumatic mechanisms and injury patterns an active search for accompanying signs is required and additional imaging methods should be implemented to exclude further complications. 2.3. Traumatic spinal injury in children Mistakes continue to be made in the assessment of the spine in children who have suffered trauma, and these mis-
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takes are often the result of two problems (Table 5). The consequence is that radiological findings are overinterpreted and, subsequently, treatment is inadequate [10]. 2.3.1. Frequency and localization of spinal injuries in children In general, spinal injuries occur less frequently in children than in adults because of the anatomical, biomechanical, and physiological differences in the skeleton during growth. Most often, the upper segments of the cervical spine are affected after head and brain trauma [10]. In the opinion of some authors, this has to do with the particular elasticity of the connective tissue, the flexibility of the axial skeleton and muscular system, the compressibility of the bones in children due to the lower mineral content, and the difference in the size relationship between body and head. According to these authors, only 2–5% of all spinal injuries occur in children [11,12]. 2.3.2. Practical procedures A neurosurgical study published in 2002 recommends the following procedure for diagnosing traumatic spinal and spinal cord injury in children: • In children who are awake, oriented, and not intoxicated, who do not demonstrate any neurological deficit, or do not present with torticollis or show painful distraction trauma, X-rays are not required to exclude cervical spinal injury. • In children who are not completely conscious or who are disoriented or intoxicated, who demonstrate neurological deficit, torticollis, or painful distraction trauma, conventional anteroposterior and lateral X-rays are required. In addition, the dens, specifically, should be X-rayed in children older than 9 years. • It is sensible to perform computed tomography to exclude occult fractures at the level of any anticipated injury to the nerves or to image those regions that cannot be adequately rendered by conventional imaging techniques. • Functional images are recommended to identify instable ligament injuries. • With MRI, spinal cord and nerve root injuries as well as damage to the capsular ligaments can be identified, and this technique plays an important role in SCIWORA (see next section). Furthermore, MRI can provide prognostic information. Some authors are of the opinion that a broader indication for conducting supplementary CT of the cervical spine after head injury in children would considerably reduce the number of conventional comprehensive X-ray studies needed to exclude cervical spine injury [13]. 2.3.3. Spinal cord injury without radiographic abnormalities (SCIWORA) 2.3.3.1. Pathogenesis. In up to 50% of children presenting with severe neurological symptoms after trauma, no abnormal findings are observed on X-ray. Orhun et al. [14] reported
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the case of a 4-year-old polytraumatized girl whose neurological condition worsened in the course of treatment although findings were normal according to conventional radiographic studies. Using MRI, the authors found intramedullary signal changes at the Th11-L3 level. Thus, they maintain that for careful neurological diagnosis, an MRI study should definitely be carried out to rule out any uncertainty and to identify any spinal cord injuries as early as possible. In the authors’ opinion the cause of such injuries is the considerable flexibility of the spine and the expansibility of the capsular ligament structures in children, in contrast to spinal cord, nerve roots, and blood vessels, which are, relatively speaking, more fixed and which can thus be distended and more easily injured. In some cases, however, neurological deficit may persist, with consequences as severe as paraplegia. 2.4. Imaging procedures 2.4.1. Conventional X-rays In most hospitals conventional X-rays are still the first radiological diagnostic procedure to be conducted. X-rays quickly provide information about whether an injury is present, give a comprehensive representation of a large section of the axial skeleton, and – although to a limited degree – help assess the extent of injury (Fig. 3, Table 6). To examine sections of the spine that for anatomical reasons cannot be viewed without also visualizing the overlying structures, CT should be performed to exclude fracture. Relatively frequently, other injuries have been sustained in the axial skeleton although only one is initially apparent. Thus, the examiner should always search for multi-level injury [19]. On lateral images of the cervical spine, the distance between the posterior wall of the pharynx to the lower anterior edge of the axis is about 7 mm (retropharyngeal space). The distance between the back of the trachea and the lower anterior edge of C6 (retrotracheal space) is about 22 mm in adults and 14 mm in children. On lateral images of the cervical spine usually only the intervertebral joint space C2/3 is not visible. If any of the small intervertebral joint spaces C3/4 to C6/7 is not freely projected or if the joint at C2/3 is visible (imaging in standard position!), it must be assumed that the joint is displaced or deformed and a further CT or MRI study must be conducted. Lateral images of the cervical spine are also suitable for identifying blocked small intervertebral joints, which can be present on only one or on both sides (Fig. 4). This is caused by flexion movements. Malfunction of the ligament–bone complex is the result of a force over time: if the rate of the force is slow, bone function usually fails; in the case of a short, strong force, the ligament is more likely to rupture [17]. If the articulation is not intact, physiological function of the ligaments cannot be maintained.
Fig. 3. (a and b) The a.-p. plain film demonstrates a multi-fragment flexioncompression fracture. CT clearly demonstrates the dislocation of the fragments.
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Table 6 Problems in the assessment of spinal injuries in children Problem
To be observed for correct diagnosis
Lack of familiarity with the special anatomical features (articulation spaces during growth) of the axial skeleton in children
Articulation spaces during growth are automatically found at expected places, marked by sclerotic margins. Fractures, in contrast, occur at unexpected sites. The margins are irregular and not sclerotic Vertebral displacement of up to 3 mm is normal (step phenomenon along the line of the dorsal vertebral bodies in adolescents on images of the cervical spine) and should not be considered luxation; the distance between the atlas and the dens can be up to 4 mm in children
Danger of overlooking injuries that could possibly cause considerable neurologic damage
Fig. 4. (a and b) The lateral plain film demonstrates subluxation of the small articula facets after distraction and rotation injury. Disturbance of the dorsal alignment. Edema and hematoma of the dorsal cervical soft tissues (T2-weighted sequences).
Table 7 Conventional X-rays in spinal injury Projection
Assessment
Lateral projection
Assessment of the dorsal edge, decreases in height of the vertebral bodies, spinal laminar line, joint process line Indications for injury by assessing deviations of the dorsal/spinous process after rotation injury, increased distance between the peduncles after burst injury Visualization of joint process fractures or unilateral luxation fractures, particularly in the cervical spine Image of the cervicothoracic junction from C7-Th2, which is nearly impossible to assess on lateral projections Diagnosis of articulation disorders
Anteroposterior projection Transverse projection Special projections (“Swimmer” projection) Functional images in positions of ante- and retroflexion
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Stress/strain images (functional images of the cervical and lumbar spine) are taken in a lateral projection at maximal flexion and/or extension. A clear indication for radiological diagnosis is given when the physician suspects that the articulation of the vertebral segments has loosened. This applies in particular for instable dorsal ligament injuries such as hyperflexion–subluxation distorsion. We perform these imaging studies when the X-ray survey does not show any instability injury or luxation, when the patient can sit or stand in an upright position, and when no neurologic deficit has been observed. In this case, the patients are asked to bend or stretch the neck as far as possible until they feel pain. A general recommendation of how to proceed in individual patients cannot be made: For this, the acute situations encountered in daily routine are too different and the medical and legal aspects involved are too great and too complex. 2.4.2. Computed tomography Detailed information about spinal canal involvement, the presence of interspinal fragments, or constriction of the epidural space can be provided in part by lateral tomography, if still in use, and especially by CT studies (Figs. 1–3). Vertebral bodies, intervertebral arches, small intervertebral joints, intervertebral disks, spinal canal, and paravertebral spaces can be ideally and freely visualized. For surgical treatment of vertebral injury, the images must include the traumatized segment and also the intact and neighboring cranial and caudal vertebrae. These include: • Unrestricted/clear representation of the epistropheus, for example, to exclude a fracture when a typical bright horizonal line at the base of the dens simulates a fracture when the posterior arch of the atlas is superimposed on target images (Mach effect). • Better representation of the transition from the cervical to the thoracic spine. • To image the pars interarticularis in the lumbar spine if spondylolysis is suspected. 2.4.3. CT instead of X-ray studies For injuries of the cervical spine, Griffen et al. [18] maintain that CT should be performed instead of X-ray studies. They established that 35% of cervical spinal injuries requiring treatment were overlooked on X-rays but identified on CT images. According to the reports of Imhof and Fuchsjager [19], conventional X-ray techniques provide up to 57% falsenegative results in the diagnosis of cervical spinal injuries. In contrast, Besman et al. [20] concluded from their study that imaging of the cervical spine at three levels provided a high sensitivity and specificity for detecting injuries. In only three of 549 patients (0.5%) were findings on the cervical spine X-rays normal although significant injury had been sustained. The authors emphasize, however, that this is precisely why a CT study of the cervical spine should be conducted when X-ray findings are normal and the nature of the acci-
dent and the clinical symptoms suggest a more serious degree of injury. This also corresponds to our experience and thus we have a broad definition for when CT imaging of the craniocranial and cervicalthoracic areas of the spine should be performed if the accident causing the injury would suggest more serious injury. 2.4.4. MSCT or conventional X-rays in patients with multiple injuries Because positioning is more difficult in accident victims and considering problems involved in obtaining useful images, often resulting in faulty radiographs and ultimately an increased radiation exposure, and also with respect to the considerable amount of time involved for diagnosis, new technique concepts are being introduced for diagnosis under acute conditions in patients with multiple injuries, specifically multi-slice spiral CT (MSCT) [21]. In some clinics, including ours, MSCT has already been integrated as part of an interdisciplinary program. The following studies have been carried out to address the question of whether conventional X-rays or a CT/MSCT should be performed first. According to a study by Rieger et al. [22], early implementation of MSCT reduces the time needed for diagnosis in polytraumatized patients by about half. Wintermark et al. [23] determined average times of 33 and 40 min for X-ray and MSCT, respectively, for examination and diagnosis. The effective radiation dose was 5.36 mSv for X-ray studies and 19.42 mSv for thoracoabdominal MSCT [23], i.e., a threefold higher dose of radiation for MSCT. In the study by Wintermark et al. [23] the cost of conventional X-ray examinations was $145 per patient and for MSCT $880. Blackmore et al. [24] examined the cost effectiveness in using conventional X-rays and additional use of CT in patients who had previously been divided into groups at high risk, normal risk, and low risk for sustaining fractures of the cervical spine. They determined that performing CT examinations in patients in the normal and high risk groups can identify the consequences and complications of injury at an early stage and that in this way costs, which are sometimes considerable, can be saved. In their study, Wintermark et al. [23] found a sensitivity of 97.2% for MSCT and 33.3% for X-ray in detecting instable fractures. For this reason, these authors also consider MSCT to be more suitable than X-rays for identifying spinal injuries and, because of the greater diagnostic accuracy and sensitivity in detecting instable fractures and also with respect to the documentation of concomitant injuries, recommend MSCT as a stand-alone modality for patients with multiple injuries. As soon as multiple injuries have been diagnosed according to a checklist, which includes accident mechanisms, vital signs, and injury patterns, and with the exception of an optional thoracic X-ray in cases of respiratory insufficiency, conventional X-rays can be dispensed with and a whole-body MSCT carried out directly after the vital functions have stabilized and abdominal ultrasound has been performed for
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orientation purposes and to exclude free fluid. This procedure is also followed at our clinic in cases of suspected polytrauma: after abdominal ultrasound and stabilization of the vital functions, we, in collaboration with the surgeon and anesthetist, quickly decide upon and carry out a CT examination. If the contents of the spinal canal are involved, the spine should be directly examined by MRI if a clear diagnosis cannot be made by CT and decisions about therapy depend on this. This involves considerable effort but today MRI examinations can also be performed in polytrauma patients.
2.4.6. Magnetic resonance imaging With MRI, the spine and contents of the spine can be directly and noninvasively imaged. This technique plays a decisive role in:
2.4.5. Myelography As a method for diagnosing acute injuries of the spine, myelography has been largely replaced by MRI [4]. In the past myelography served to identify CSF flow disorders in interspinal fragments, dural rupture, and nerve root ruptures, usually in combination with a subsequent CT study. Ultimately, the patient positioning required for spinal canal puncture renders this examination very difficult to carry out in multiply injured patients and the information for diagnosis that can be provided by this technique is relatively insignificant. Today the only place for myelography in trauma patients is, in exceptional cases, for clarification in suspected impending paraplegia or to determine the location of an intraspinal injury for surgical planning if MRI is contraindicated.
In addition to standard contraindications for MRI, e.g., cardiac pacemakers, trochlear implants, or ferromagnetic intracranial aneursymal clips, this technique cannot be nonrestrictively employed in acute spinal injuries for other reasons as well. In patients with multiple injuries the circulation is also often unstable. Thus MRI is less suitable in these patients as the spatial conditions would make it difficult to carry out cardiopulmonary resuscitation measures if necessary. Furthermore, the equipment required for adequate cardiocirculatory monitoring cannot always be implemented in a magnetic environment. Today, however, equipment lacking ferromagnetic properties is available and it is becoming increasingly possible to respirate polytraumatized patients during the MRI examination.
• Assessing the spatial relationship between bony fragments and myelon compression. • Visualizing concomitant intracanalicular and paravertebral soft tissue and vascular or nerve injuries. • Visualizing primary and secondary spinal cord changes in the acute and postacute phases.
Fig. 5. (a and b) T1-weighted sequence shows traumatic disc injury of the segment C3/4 and rupture of the anterior and posterior ligament as well as of the interspinosus ligament. T2-weighted sequence shows high signal intensity of the spinal cord due to intramedullary edema due to contusion of the spinal cord.
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Table 8 MRI protocol for spinal injuries Sagittal T1-weighted sequences to demonstrate the anatomy Sagittal, fat-suppressed T2-weighted TSE/FSE sequences to image the total spine in order to detect edema or the presence of blood in any section of the spine and to localize and assess the extent of injury in one session Sagittal GRE sequences to image the blood and blood vessels and to better distinguish between osteophytes and disks Axial T1-weighted sequences to further assess the epidural space, the spinal cord, and neuroforamina in areas of certain abnormal findings on sagittal sections
The standard sequences used to examine patients with spinal injuries are (Table 8): • Sagittal and axial T1-weighted spin echo sequences to evaluate the anatomy. • Sagittal T2-weighted fluid-sensitive turbo SE sequences with and without fat suppression, making it easier to detect pathological changes in the presence of persistent, concomitant edema in these patients.
• Susceptibility-sensitive, blood-sensitive gradient echo sequences that can also visualize the ligaments, distinguish between traumatic vertebral prolapse and osteophytes, and can render spinal cord anatomy and the blood vessels (Table 8). At our institution, the protocol outlined in Table 7 is carried out in cases of spinal trauma. 2.5. Spinal cord injury Detecting spinal cord injury (concussion/contusion of the spinal cord, central cord syndrome, spinal cord hematoma) in conjunction with intramedullary edema (Fig. 5) or bleeding or a combination of these two components has particular significance for prognosis and further outcome. Progrnosis in terms of recovery from neurological complications is worse in patients in whom bleeding is present than in those with only edema. Generally, a true contusion of the spinal cord or transient traumatic spinal cord apraxia with or without a weak, hyperintense signal on T2-weighted images is completely reversible within a maximum of 72 h. In spinal cord
Fig. 6. (a and b) Rupture of the anterior longitudinal and interspinosus ligament together with edema and hematoma.
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contusion with spinal cord edema MRI signal recovery is slower and may indicate remaining neurological deficit. In contrast, hematoma in the spinal cord (weak signal on T2weighted and gradient echo contrast) shows only little or no signal recovery over time (Table 8). 2.6. Ligament injuries Additionally, MRI can detect both unexpected ligament injuries and ligament injuries beyond the extent of those anticipated, particularly when conventional X-ray findings were normal. Here, T2-weighted images are most suitable, showing a disruption in the course of the ligament structure, which otherwise lacks a signal, in combination with a signal increase that may involve neighboring sections (Fig. 6). MRI studies show that in thoracolumbar ligament injuries conforming to the aforementioned frequency of thoracolumbar flexion injuries in conjunction with distraction of the dorsal parts of the vertebrae, the following ligaments are affected with decreasing frequency: • • • •
Inter- and supraspinal ligaments. Flaval ligaments. Posterior longitudinal ligament. Anterior longitudinal ligament.
2.7. Traumatic vertebral disk prolapse It is equally important to identify traumatic vertebral disk prolapse, which by compressing the spinal cord or nerve roots can cause corresponding neurologic symptoms that urgently require surgical treatment. Vertebral disk prolapse is observed particularly frequently in patients who have sustained uni- or bilateral facet joint subluxation injury. To better distinguish between the vertebral disks and osteophytes we recommend using gradient echo sequences where the loss of signal intensity in bone represents a significant contrast to the relatively high signal of the vertebral disks (Fig. 5). 2.8. Epidural bleeding Last but not least, epidural bleeding can be detected by MRI. As a result of the tight binding of the posterior longitudinal ligament of the spine with the ventral dura and the disk, hematomas form typically in the dorsal epidural space. This can develop acutely after trauma or be delayed and in 50% of patients without any evidence of injury to the spine. In the acute phase (1–3 days) a hematoma is hypo- or isointense to the spinal cord on contrast-enhanced T1-weighted images and shows a signal increase on T2-weighted images. Subsequently, as a result of oxidation processes in the hemoglobin and the development of blood degradation products, the total signal on T2-weighted images decreases and the peripheral signal increases both on T1- and T2-weighted images. On gradient echo sequences, a strong signal decrease is noted as a sign of the bleeding.
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3. Summary Fractures of the spine account for 3–6% of all injuries of the skeleton and occur more frequently in individuals between 20 and 50 years of age. Most fractures involve the thoracic and lumbar spine and often are associated with severe concomitant injuries (spinal cord, blood vessels, intrathoracic or intraabdominal organs, head-brain trauma) [6,7,9]. In general, spinal injuries occur less frequently in children than in adults because of the anatomical, biomechanical, and physiological differences in the skeleton during growth (2–5% of the total) [11,12]. If no injuries are visible on Xrays in children, an MRI study should be conducted quickly in order to exclude spinal cord injury (SCIWORA). The diagnosis and treatment of spinal injuries presents all specialists with a great challenge, particularly in unconscious patients and patients with multiple injuries in whom the extent of injury is not known when they are admitted to the hospital. At many centers, conventional X-rays at two levels and possibly special images, are still primarily taken to detect and diagnose injuries of the spine. In interpreting the findings, it is useful to know the cause and mechanism of the injury as these injuries leave certain “fingerprints” on the axial skeleton. These “fingerprints” facilitate diagnosis, i.e., analysis of the visible and anticipated injuries. The majority of authors are of the opinion that CT should be used instead of conventional X-rays, particularly in patients at normal and high risk for fractures. In patients with multiple injuries, rapid diagnosis – which begins when they enter the shock room – is essential for successful therapy. At many centers multi-slice spiral CT has already been integrated into diagnostic workup in the shock room and therefore conventional diagnostic X-ray studies can be dispensed with in these cases. The complete assessment of spinal trauma includes Xrays to determine the level of the injury and also the use of CT and MRI. With CT the extent of the injury can be documented, including the dorsal parts of the vertebrae. MRI serves to determine whether concomitant soft tissue injuries have been sustained, including the vertebral disks, ligaments, epidural space, and vessels, and also to directly assess the spinal cord. Furthermore, in cases of unexplained persisting clinical symptoms (e.g., SCIWORA), MRI is very useful for excluding epidural hematoma, traumatic disk hernation, or spinal cord injuries.
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