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Spinal column injuries in adults: Definitions and mechanisms INTRODUCTION — This topic review describes injuries to the cervical, thoracic, and lumbosacral spinal column, including fractures, dislocations, and subluxations of the vertebrae, and injuries to the spinal ligaments. The importance of the recognition and management of injuries to the spinal column is underscored by their association with spinal cord injury. EPIDEMIOLOGY — Among patients included in a large trauma registry, approximately 3 percent of those with blunt trauma sustain a spinal column injury, such as spinal fracture or dislocation, and 1 percent sustains a spinal cord injury . Spinal column injury rates reported in other studies range from 2 to 6 percent . The incidence is likely to be significantly higher in patients with head trauma and those who are unconscious at presentation. Fracture of the thoracolumbar spine, including spinous and transverse process fractures, may occur in as many as 8 to 15 percent of blunt trauma patients cared for at major trauma centers . A systematic review of 13 international studies found great variation (up to a threefold difference) in the rate of spinal column injury among nations, particularly between developed and developing nations [4,5]. Most studies demonstrate a bimodal age distribution where the first peak is found in young adults between 15 and 29 years of age and a second peak in adults older than 65 years of age. Mortality is significantly higher in elder patients . Spinal column injuries are more common in males. Note that statistics from trauma registries can be incomplete and inaccurate, depending on the inclusion criteria, and may overestimate the number of patients with spinal column injury. As examples, victims who die at the accident scene and patients whose neurologic deficits rapidly improve are often not included. Motor vehicle related accidents account for almost half of all spinal injuries , and speeding, alcohol intoxication, and failure to use restraints are major risk factors. Occupants involved in a rollover accident are at increased risk of a cervical spine injury . Other common causes include falls, followed by acts of violence (primarily gunshot wounds), and sporting activities. The falls of older adults account for a growing proportion of spinal injuries, reflecting the aging population of many developing countries. Missed or delayed diagnosis of spinal column trauma results in a 7.5-fold increase in the incidence of neurologic injuries . ANATOMY — The human spine consists of 33 bony vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 sacral (fused), and 4 coccygeal (usually fused) . These 26 individual units are separated by intervertebral disks and connected by a network of ligaments. The vertebral column provides the body's basic structural support and also protects the spinal cord, which extends from the midbrain caudally to the level of the second lumbar vertebra and then continues as the cauda equina. Pictures and radiographs depicting the details of spinal anatomy are found below: Spine anatomy overview Vertebral anatomy Cervical vertebrae (picture 1) C1 and C2 detail Thoracic vertebrae (picture 2) Cervical joints and ligaments Skull and superior cervical spine interface (picture 3) Due to its exposed location above the torso and its inherent flexibility, the cervical spine is the most commonly injured part of the spinal column. Within the cervical spine, the most common sites of injury are around the second cervical vertebra (C2, or axis) or in the region of C5, C6 and C7 . In contrast, the thoracic spine is rigidly fixed, as the thoracic ribs articulate with the respective transverse processes and sternum. Thus, a great amount of force is necessary to damage the thoracic spine of an otherwise healthy adult. In older adults with osteoporosis or patients with bone disease, minor trauma may be sufficient to cause a compression fracture. The second most commonly injured region is the thoracolumbar (TL) junction. The orientation of the facet joints at the TL junction may concentrate forces created from traumatic impact at this level . At the TL junction, the spinal column changes from a kyphotic to a lordotic curve. Of all TL spine injuries, 90 percent of fractures occur in the region between T11 and L4. However, since the spinal canal is relatively wide at this level, TL junction injuries rarely result in complete cord lesions . MECHANISMS — Spinal column injury may result in spinal cord trauma through a number of mechanisms : Transection — Penetrating or massive blunt trauma resulting in spinal column injury may transect all or part of the spinal cord; less severe trauma may have similar neurologic effects by displacing bony fragments into the spinal canal or through disk herniation. Compression — When elderly patients with cervical osteoarthritis and spondylosis forcibly extend their neck, the spinal cord may be compressed between an arthritically enlarged anterior vertebral ridge and a posteriorly located hypertrophied ligamentum flavum. Injuries that produce blood within the spinal canal can also compress the spinal cord. Contusion — Contusions of the spinal cord can occur from bony dislocations, subluxations, or fracture fragments. Vascular injury — Primary vascular damage to the spinal cord should be suspected when there is a discrepancy between a clinically apparent neurologic deficit and the known level of spinal column injury. As an example, when a lower cervical dislocation compresses the vertebral arteries within the spinal foramina of the vertebrae, thrombosis and decreased blood flow through the anterior spinal artery may result. The anterior spinal artery originates from both vertebral arteries at the level of C1. This injury may erroneously appear to localize to the level of C1 or C2 rather than the site of the dislocation. Certain conditions predispose patients to cervical spinal column injury. Down syndrome patients are predisposed to atlanto-occipital dislocation; patients with rheumatoid arthritis are prone to rupture of the transverse ligament of C2. CERVICAL SPINAL COLUMN INJURY Cervical spinal column injury classification — Acute cervical spinal column injury may be classified according to the stability of the injury, its location, or the mechanism (flexion, flexion-rotation, extension, and vertical compression) (table 1) [13,14]. To assess the stability of cervical spinal column injuries below C2, the spine is viewed as consisting of two columns. The anterior column is formed by alternating vertebral bodies and intervertebral disks held in alignment by the anterior and posterior longitudinal ligaments. The posterior column, which contains the spinal canal, is formed by pedicles, transverse processes, articulating facets, laminae, and spinous processes. The nuchal ligament complex (supraspinous, interspinous, and infraspinous ligaments), capsular ligaments, and ligamentum flavum hold the posterior column in alignment. If both columns are disrupted, the cervical spine can move as two independent units, and there is a high risk of causing or exacerbating a spinal cord injury . In contrast, if only one column is disrupted, the other column maintains structural integrity and the risk of spinal cord injury is far less. Atlanto-occipital dislocation — Pure flexion injuries involving the atlas (C1) and the axis (C2) can cause an unstable atlanto-occipital or atlanto-axial joint dislocation, with or without an associated odontoid fracture (picture 4). Several measurements are used to determine the presence of atlanto-occipital joint dislocation on plain lateral x-ray of the cervical spine, but their accuracy and interobserver reliability are not well studied in trauma patients . The basion-posterior axial line interval (BAI) and the basion-dental interval (BDI) demonstrate consistent relationships in normal adults . They are determined by using a line drawn along the posterior border of the anterior body of C2. Two lines are then drawn from this line: one perpendicularly to the basion (ie, occipital base), and another from the basion to the tip of the dens. A sum of these two lines originating from the basion exceeding 12 mm suggests atlanto-occipital joint dislocation. The Powers ratio is commonly used to assess for atlanto-occipital dislocation. It is defined by the ratio of BC:OA, where BC is the distance between the basion and the midpoint of the posterior laminar line of C2, and OA is the distance between the midpoint of the posterior margin of the foramen magnum (opisthion) and the anterior arch of C2 . A ratio greater than one suggests anterior subluxation. Another radiologic finding suggestive of an atlanto-occipital dislocation is disruption of the “basilar line of Wackenheim,” a line drawn from the posterior surface of the clivus to the odontoid tip [18,19]. Normally, the inferior extension of this line should just touch the posterior aspect of the tip of the odontoid. If the line runs anterior or posterior to the odontoid tip, this suggests an atlanto-occipital dislocation. Atlanto-axial dislocation — Rotary atlanto-axial dislocation is an unstable injury, caused by a flexion-rotation mechanism, best visualized on open- mouth odontoid radiographs or CT scan (picture 5). The interpretation of odontoid radiographs warrants careful attention, since there may be false positive asymmetry between the odontoid process and the lateral masses of C1 if the skull is rotated. When the x-ray reveals symmetric basilar skull structures, a unilaterally magnified lateral mass confirms a C1-C2 dislocation. C1 (Atlas) fractures Burst (Jefferson) — The Jefferson fracture of C1 is highly unstable and occurs when a vertical compression force is transmitted through the occipital condyles to the lateral masses of the atlas (picture 6 and picture 7 and picture 8). This force drives the lateral masses outward, resulting in fractures of the anterior and posterior arches of the C1, with or without disruption of the transverse ligament. Disruption of the transverse ligament determines instability. Prevertebral hemorrhage combined with disruption of the transverse ligament may cause an increase in the predental space between C1 and the odontoid (dens) seen on the lateral radiograph. A predental space greater than 3 mm in adults or 5 mm in children is abnormal . In the AP projection (open-mouth or odontoid view), the masses of C1 lie lateral to the outer margins of the articular pillars of C2. The Jefferson fracture may be difficult to recognize on plain x-ray if there is minimal displacement . The transverse ligament is presumed to be disrupted if the interval between the atlas and the dens is increased on a lateral radiograph, or the lateral masses of the atlas extend laterally beyond those of the axis on the odontoid radiograph. In such instances, clinicians should obtain a CT scan of the cervical spine. Posterior arch — A posterior neural arch fracture of C1 results from compression of the posterior elements between the occiput and the spinous process of C2 during forced neck extension. A vertical fracture line through the posterior neural arch is seen on lateral x-ray (picture 9). Although mechanically stable because the anterior arch and the transverse ligament remain intact, this fracture is potentially dangerous because of its location. Anterior displacement of the atlas greater than 1 cm can injure adjacent spinal cord. C2 (Axis) pedicle fractures — Traumatic spondylolysis of C2 (so-called "hangman's fracture") is an unstable injury that occurs when the cervicocranium (the skull, atlas, and axis functioning as a unit) is thrown into extreme hyperextension as a result of abrupt deceleration (ie, forced extension of an already extended neck) (picture 10 and picture 11). Bilateral pedicle fractures of the axis may occur with or without dislocation in this circumstance. Although this lesion is unstable, spinal cord damage is often minimal because the AP diameter of the neural canal is greatest at C2, and bilateral pedicle fractures permit spinal canal decompression . Odontoid fractures — Forceful flexion or extension of the head in an anterior-posterior orientation (ie, sagittal plane), as might occur with a forward fall onto the forehead, may result in a fracture of the odontoid process, also called the dens. Fractures can occur above the transverse ligaments (type I) or, most commonly, at the base of the odontoid process where it attaches to C2 (type II) (picture 12 and picture 13). Type I fractures are stable. Although spinal cord injury is uncommon, type II odontoid fractures are unstable and complicated by nonunion in over 50 percent of patients treated with halo vest immobilization . Slight angulation of the force may result in extension of the fracture through the upper portion of the body of C2 (type III) (picture 14 and picture 13). Type III fractures are mechanically unstable, since they allow the odontoid and the occiput to move as a unit. Odontoid fractures are best seen on the AP odontoid radiograph (ie, open-mouth view) and cause prevertebral soft tissue swelling on lateral radiographs. Anterior wedge — Forceful flexion of the cervical spine can compress the anterior portion of a vertebral body, creating an anterior wedge fracture. Spinal instability can result if anterior wedge fractures are severe (loss of over half the height of the anterior vertebral body) or multiple adjacent wedge fractures occur (picture 15 and picture 16 and picture 17). In pure flexion injuries below C2, the strong nuchal ligament complex usually remains intact, and most of the force is expended on the vertebral body anteriorly, causing a simple wedge fracture . Radiographically, the height of the anterior border of the vertebra is diminished, and prevertebral soft tissue swelling is present. Because the posterior column remains intact, this injury is usually stable and rarely associated with spinal cord injuries. Flexion teardrop — A flexion teardrop fracture results when severe flexion and compression cause one vertebral body to collide with the body below, leading to anterior displacement of a wedge-shaped fragment (resembling a teardrop) of the antero-inferior portion of the superior vertebra (picture 18 and picture 19). They usually occur in the lower cervical spine. On plain lateral radiographs, the fractured vertebra appears to be divided into a smaller anterior fragment and a larger posterior piece. The larger piece displaces posteriorly as a unit with the superior cervical spine relative to the vertebrae below. The anterior fragment typically remains aligned with the inferior cervical vertebrae. If there is no posterior displacement of the superior column, widening of the interlaminar and interspinous spaces supports the diagnosis of a flexion teardrop fracture . The severe anterior flexion involved in this injury creates distraction forces at the posterior cervical spine and disruption of the posterior longitudinal ligament. Thus, flexion teardrop fractures are highly unstable. They are associated with acute anterior cervical cord syndrome. (See "Anatomy and localization of spinal cord disorders", section on 'Ventral (anterior) cord syndrome'.) Extension teardrop — An extension teardrop fracture occurs when abrupt neck extension causes the anterior longitudinal ligament to avulse the antero-inferior corner from the remainder of the vertebral body, producing a triangular-shaped fragment (picture 20 and picture 21). This unstable injury is found most often at C2, but can also occur at C5 to C7 with diving accidents and can be associated with a central cord syndrome . Although similar in radiographic appearance to the flexion teardrop fracture, the vertebra involved in an extension teardrop injury generally does not lose height. In contrast, a vertebra with a flexion teardrop fracture may lose height from compression . (See "Anatomy and localization of spinal cord disorders", section on 'Central cord syndromes'.) Spinous process fractures — The clay shoveler's fracture, an isolated fracture of one of the spinous processes of the lower cervical vertebrae, is a stable injury (picture 22). It derives its name from its occurrence in clay miners during the 1930s. Today, this fracture is more commonly seen following direct trauma to the spinous process and after motor vehicle crashes involving sudden deceleration that result in forced neck flexion. Burst fractures — Vertical compression injuries occur in the cervical and lumbar regions when axial loads are exerted on the spine. Such forces are applied from above (via the skull) or below (via the pelvis or feet), and may cause one or more vertebral body end-plates to fracture. When the nucleus pulposus of the intervertebral disk is forced into the vertebral body, the body shatters outward, resulting in a burst fracture. The lateral radiograph shows a comminuted vertebral body and loss of vertebral height, while the anterior-posterior (AP) radiograph demonstrates a characteristic vertical fracture of the vertebral body (picture 23). Although technically burst fractures are “stable” since all ligaments remain intact, posteriorly displaced fracture fragments may impinge on the spinal cord, causing an anterior cord syndrome. (See "Anatomy and localization of spinal cord disorders", section on 'Ventral (anterior) cord syndrome'.) To reflect this risk of spinal cord injury, burst fractures can be classified as unstable if any of the following are present: Associated neurologic deficits Loss of greater than 50 percent of vertebral body height Greater than 20 degrees of spinal angulation Compromise of more than 50 percent of the spinal canal . Facet dislocations Bilateral — Bilateral facet dislocations occur when flexion forces extend anteriorly, causing disruption of the annulus fibrosus of the intervertebral disc and the anterior longitudinal ligament, resulting in extreme instability. The inferior articulating facets of the upper vertebra pass over the superior facets of the lower vertebra, resulting in anterior displacement of the spine. Complete spinal cord injury most often results. Radiographically, the displacement will appear to be greater than one half of the anteroposterior (AP) diameter of the lower vertebral body with the superior facets anterior to the inferior facets, which is best seen on the lateral view (picture 24 and picture 25). Unilateral — Unilateral facet dislocations involve flexion and rotation. Rotation occurs around one of the facet joints; dislocation occurs at the contralateral facet joint, with the superior facet moving over the inferior facet, and coming to rest within the intervertebral foramen (picture 26). On a lateral plain radiograph, the two lateral masses of the dislocated vertebrae may partially overlap giving the appearance of a bow tie (radiologists may refer to a bowtie or double diamond sign). Since the dislocated articular mass is locked in place, this is a stable injury despite posterior ligament complex disruption. Spinal cord injury rarely occurs following isolated unilateral facet dislocation. However, associated fractures of the facet or surrounding structures can create instability . Ligamentous injuries and SCIWORA — The definition of spinal cord injury without radiographic abnormality (SCIWORA) varies among studies, but it is often defined as the presence of neurologic deficits in the absence of bony injury on a complete, technically adequate, plain radiograph series or CT scan. This injury pattern is more common in children and has been attributed to several causes, including ligamentous injuries, disc prolapse, and cervical spondylosis. (See "Evaluation of cervical spine injuries in children and adolescents".) Clinicians should suspect a cervical ligamentous injury in the injured patient who has persistent severe pain or paresthesias or focal neurologic findings (eg, upper extremity weakness) in the absence of a fracture seen on plain radiographs or CT. Such injuries may be unstable, although they are rarely associated with permanent neurologic damage. Evaluation of suspected ligamentous injury or SCIWORA in adults is discussed separately. (See "Evaluation and acute management of cervical spinal column injuries in adults", section on 'Evaluation for ligamentous injury and SCIWORA'.) THORACIC AND LUMBAR (TL) SPINAL COLUMN INJURY TL spinal column injury classification — In contrast to the two column scheme for cervical spinal column injury, a three column scheme may be used to describe injuries of the thoracic and lumbar (TL) spinal column . The three columns are anterior, middle, and posterior. The anterior column includes the anterior longitudinal ligament, the annulus fibrosus, and the anterior half of the vertebral body. The middle column comprises the posterior longitudinal ligament, the posterior annulus fibrosus, and the posterior half of the vertebral body. The posterior column includes the supraspinous and interspinous ligaments, as well as the facet joint capsule. According to the three column scheme, stability is based upon the integrity of two of the three spinal columns. Spinal instability may be inferred when plain radiographs demonstrate a loss of 50 percent of vertebral height or excessive kyphotic angulation around the fracture . The angle is determined by the intersection of two lines, one measured along the superior endplate of the vertebral body one level above the fracture and the other along the inferior endplate of the vertebral body one level below . Compression fractures with greater than 30 degrees and burst fractures with greater than 25 degrees angulation are generally considered unstable. The presence of a neurologic deficit also indicates spinal instability, since the spinal column has failed to protect the spinal cord . Few studies have been performed to validate the three column scheme. In a biomechanical study of cadaveric human spines, researchers found the middle column to be the major determinant of spine stability when axial or flexion stress was applied . TL injuries can be divided into four basic patterns: wedge compression fractures, stable and unstable burst fractures, flexion-distraction injuries, and translational injuries. All of these fractures result from one or more of three mechanisms of injury: axial compression, axial distraction, and translation [26,31]. A widely used classification for TL spinal column injury combines a distinction between major and minor fracture patterns using the three column scheme and the five injury patterns. In 2005, the Spine Trauma Study Group introduced a classification system for thoracolumbar injuries called the Thoracolumbar Injury Classification and Severity Score (TLICS). This score assigns numerical values to each injury based upon morphology, neurologic status, and integrity of the posterior ligamentous complex, which includes the supraspinous ligament, interspinous ligament, ligamentum flavum, and facet joint capsules . Scoring of the TLICS is as follows: Injury morphology Compression = 1 point Burst = 1 point Translational/rotational = 3 points Distraction = 4 points Neurological Status Intact = 0 points Nerve root = 2 points Cord, conus medullaris: Incomplete = 3 points Complete = 2 points Cauda equina = 3 points Posterior Ligament Complex Intact = 0 points Injury suspected/indeterminate = 2 points Injured = 3 points The total numerical score is used to guide treatment. A score ≥5 suggests instability and the need for operative treatment, whereas a score ≤3 suggests stability. A score of 4 is considered indeterminate and either operative or conservative management may be indicated . Compression fractures — Wedge, or anterior, compression fractures account for 50 to 70 percent of all TL fractures [31,34]. They usually result from compressive failure of the anterior column under an axial load applied in flexion. Injuries that do not disrupt the posterior ligament complex are stable. An additional rotational force is necessary to cause an unstable fracture pattern. If there is severe compression (>50 percent of vertebral height), significant fracture kyphosis (>30 degrees), a rotational component to the injury, or compression fractures at multiple levels, then the posterior ligamentous complex may fail and progress to involve the middle column, resulting in spinal instability. Fractures with any of these characteristics or a TLICS score ≥4 warrant imaging with CT. Fracture kyphosis is described above. (See 'TL spinal column injury classification' above.) Compression fractures that exhibit between 10 and 40 percent compression are managed on a case-by-case basis in consultation with a spine surgeon. Neurologic findings or concomitant injuries warrant a thorough evaluation. Management of spinal column injury is discussed separately. (See "Evaluation and acute management of cervical spinal column injuries in adults".) Simple wedge fractures demonstrate less than 10 to 30 percent compression and generally cause no neurologic impairment, since the middle column remains intact. These fractures generally result from falls, motor vehicle crashes, and occasionally generalized tonic-clonic seizures . Associated injuries are common and fractures frequently occur at other spinal levels. Simple wedge compression fractures are best seen on lateral radiographs, which demonstrate anterior compression of the vertebral body without disruption of the posterior cortex. The AP radiograph may demonstrate a subtle increase in the interspinous distance if there is a kyphotic deformity. It is important to confirm that the posterior elements remain intact (ie, no vertebral subluxation), since the integrity of the posterior cortex is what distinguishes the stable wedge compression fracture from the unstable burst fracture. Standard radiographs may not be adequate to evaluate the integrity of the posterior vertebral cortex. In an analysis of 67 thoracolumbar radiographs reviewed by two radiologists and two orthopedists, 20 percent of CT-confirmed burst fractures were initially misdiagnosed as wedge fractures . Thus, CT should be performed when plain radiographs suggest any possible involvement of the posterior cortex in what appears to be a wedge compression fracture. Such findings include fracture lines that extend into the posterior cortex and any compression of the posterior cortex. Other suggestive features include loss of posterior vertebral height and widening of the interpedicular distance. Burst fractures — Burst fractures comprise approximately 14 percent of all TL injuries . They are caused by compressive forces that fracture the vertebral endplate and pressure from the nucleus pulposus upon the vertebral body. Spinal cord injury from retropulsion of bony fragments into the spinal canal can occur. Burst injuries can occur with or without injury to posterior elements; posterior element involvement increases the risk for neurologic deficits . Burst fractures are most commonly associated with falls and motor vehicle collisions. All burst fractures should be considered unstable, since neurologic deficits are seen in 42 to 58 percent of patients . Burst fractures can be difficult to visualize and are often misdiagnosed by plain radiography because posteriorly displaced bone fragments often lie at the level of the pedicles . Lateral x-rays of burst fractures may demonstrate a loss of anterior and posterior vertebral height, and may show a distorted posterior longitudinal ligament line. AP radiographs may demonstrate a widening of the interpedicular distance (>1 mm difference between the vertebrae above and below). Unstable burst fractures are often misdiagnosed as stable anterior wedge fractures. In one retrospective trial, 6 experienced radiologists correctly identified only 30 of 39 burst fractures among 53 thoracolumbar radiographs reviewed . We recommend that a CT be obtained if there is vertebral compression greater than 50 percent or a burst fracture is suspected for any reason. Flexion-distraction (lap belt) injuries — Flexion-distraction injuries account for 10 percent of all TL spinal column injuries and occur most frequently in patients wearing only a lap belt (ie, no chest restraint) during vehicular trauma . While neurologic deficits are rare, associated intraabdominal injuries, such as small and large intestinal perforations, are more common. A seat belt sign may be present. (See "General approach to blunt abdominal trauma in adults".) Chance fractures are representative of TL flexion-distraction injury. Classically the patient is wearing only a lap belt, positioned incorrectly above the pelvic bones. Sudden deceleration during a collision causes forceful flexion at the lap belt, leading to compressive failure of the anterior and middle columns and a tear in the posterior longitudinal ligament. Chance fractures are often misdiagnosed as compression fractures. Pure ligamentous disruptions also occur and account for 10 to 25 percent of flexion-distraction injuries . In contrast to the cervical region, where articular processes are small, flat, and almost horizontal, articular processes in the lumbar region are large, curved, and nearly vertical, and thus, unilateral facet dislocations are rare. Instead, one or both articular processes fracture, and the upper vertebra swings forward, resulting in an unstable fracture-dislocation pattern. Radiographic findings of flexion-distraction injuries include compression fractures of the vertebral body, and increased posterior interspinous spaces caused by distraction. A characteristic finding is increased length of the vertebral segment as a result of distraction. Displacement is unusual, since the mechanism does not involve a significant rotational or translational component. Flexion-distraction injuries may be missed on routine axial CT scans since the disruption is oriented in the horizontal plane. Thus, it is important to obtain sagittal reconstructions of CT images if a lap belt mechanism is known or a flexion-distraction injury is suspected for other reasons (eg, presence of abdominal seat belt sign, known bowel injury) . A systematic review found that reformatted CT images from visceral studies demonstrated greater sensitivity and specificity than plain TL radiographs in detecting spinal column injury . Translational spinal column injury — Massive direct trauma to the back can cause failure of all three columns of the TL spine resulting in translational injuries. Several injury patterns can occur, including rotational fracture-dislocations, shear injuries, and pure vertebral dislocations. The thoracolumbar junction (T10 to L2) is the most common site . Patients with a complete vertebral dislocation from massive trauma almost invariably demonstrate neurologic deficits. Among patients rendered paraplegic from TL trauma, the majority have sustained a fracture-dislocation injury. Approximately 26 to 40 percent of these result in permanent neurologic deficits . Most patients also sustain multiorgan system trauma. Shear fractures and pure dislocations result in severe neurologic injury, causing complete paraplegia in nearly all patients. Pure dislocations appear as a complete displacement of the superior vertebrae relative to the one below. Fracture fragments created by shearing forces may lodge in the spinal canal. CT scan is helpful in evaluating these injuries because it quantifies the extent of spinal cord impingement. Other TL fracture patterns — Minor spinal fracture patterns account for 14 percent of all TL injuries and include isolated transverse process fractures, spinous process fractures, facet or laminar fractures, bipedicular fractures, and fractures of the pars interarticularis. Most minor spinal fractures occur in the lumbar region and are caused by direct blows. Sudden contraction of the psoas muscles can result in avulsion of a transverse process. While transverse process fractures are considered stable, in high velocity trauma they frequently do NOT occur in isolation. In one retrospective analysis of 28 patients who initially appeared to have isolated transverse process fractures by plain x-ray, three patients were subsequently found to have compression and burst fractures by CT scan . High thoracic spinous process fractures may be associated with brachial plexus injury, while lumbar and sacral spinous process fractures may cause lumbosacral plexus injury. To ensure appropriate diagnosis and management of spinal column injury, a CT should be obtained when transverse process fractures are seen on plain radiographs. SUMMARY AND RECOMMENDATIONS Blunt trauma, particularly motor vehicle collisions, accounts for most spinal column injuries. Approximately three percent of blunt trauma patients sustain such an injury. Elder patients who fall are also at risk. (See 'Epidemiology' above.) The cervical spine is the most commonly injured part of the spinal column. Within the cervical spine, the most common sites of injury are around the second cervical vertebra (C2, or axis) or in the region of C5, C6, and C7. The anatomy of the spinal column and common mechanisms of injury are described in the text. (See 'Anatomy' above and 'Mechanisms' above.) The degree of stability is perhaps the most important feature of any spinal column injury. The stability of common spinal injuries is described in the text and summarized in the accompanying table (table 1). (See 'Cervical spinal column injury' above and 'Thoracic and lumbar (TL) spinal column injury' above.) Differences in the structure and location of the cervical and thoracolumbar portions of the spinal column lead to different types of injuries, although there is some overlap. The cervical spinal column is susceptible to a wide range of fractures, dislocations, and ligamentous injuries. Compression fractures are the most common injury of the thoracolumbar spinal column. Use of UpToDate is subject to the Subscription and License Agreement. REFERENCES 1. National Spinal Cord Injury Association Resource Center. www.sci-info-pages.com/factsheets.html (Accessed on May 22, 2008). 2. Greenbaum J, Walters N, Levy PD. An evidenced-based approach to radiographic assessment of cervical spine injuries in the emergency department. J Emerg Med 2009; 36:64. 3. 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