AUTHOR AND EDITOR INFORMATION

Section 1 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

INTRODUCTION

Section 2 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Background

Thoracic spinal fractures can occur whenever forces exceed the strength and stability of the spinal column. Common injuries resulting in fractures of the thoracic spine include a fall from a height, automobile accidents, and penetrating trauma. After traumatic aortic rupture, spinal cord injuries represent the most serious long-term morbidities resulting from thoracic trauma.

The goal of the diagnostic imaging is to correctly identify spinal fractures, to identify injuries to the spinal cord and nerve roots, to aid in surgical planning, and to judge the stability of postoperative fixation. This article highlights the typical patterns of injury within a classification based on the mechanism of injury while focusing on the imaging methods that are most useful in clinical practice.

For excellent patient education resources, visit eMedicine's Back, Ribs, Neck, and Head Center. Also, see eMedicine's patient education article Vertebral Compression Fracture.

Pathophysiology

Fractures most commonly occur in the lower thoracic vertebrae and are less common in the upper and mid thoracic areas. The upper thoracic spine (T1-10) is stabilized by the ribs and the orientation of the facets. However, at the T12-L1 junction, increased range of motion allows combinations of acute hyperflexion and rotation. The mechanisms of thoracolumbar spine trauma are hyperflexion, vertical compression, hyperextension, and shearing injury.

Hyperflexion injury includes flexion with compression, lateral flexion, flexion-rotation, flexion-distraction, and seatbelt injuries. Vertical compression results in burst injuries of the vertebral bodies. Hyperextension injuries result in posterior spinal compression fractures, while shearing injury causes subluxation or dislocation of the spinal column. In thoracolumbar injuries, 60-70% occur in the T12-L2 region. Because the spinal cord terminates at this level, bladder and bowel signs and decreased movement and sensation in the lower extremities may result from fractures of the lower thoracic region.

Considering the thoracic spine as having an anterior column, a middle column, and a posterior column is useful (see Image 4). According to the classification proposed by Denis, the anterior column is composed of the anterior longitudinal ligament, the anterior annulus, and the anterior portion of the vertebral body. The middle column includes the posterior longitudinal ligament, the posterior annulus, and the posterior portion of the vertebral body. The posterior column includes those spinal structures that are posterior to the posterior longitudinal ligament.

Well-recognized patterns of spinal injury include anterior and lateral compression (see Image 17); burst fracture; seatbelt or Chance fractures (see Images 19-20, Image 22); and fracture dislocations, including flexion-rotation, shear, and flexion-distraction injuries (see Image 21). Compression fractures result from either an anterior flexion force or a lateral flexion force (see Image 24). Anterior compression fractures represent the most common fractures of the thoracic spine (see Image 7, Images 13-14).

A burst fracture results from a vertical force applied to the central axis that exceeds the strength of the vertebral endplate and the vertebral body (see Image 15).

In the classic seatbelt injury, the patient is thrown forward forcefully, while lower trunk is held in a fixed position. Although the point of fixation is most often a seatbelt, a similar injury can occur whenever an individual is held at the level of the lower trunk or upper pelvis by a steering wheel or the frame of the front window in a car. The primary force causing a seatbelt fracture is flexion with distraction. A unilateral or bilateral locked facet injury is uncommon in the thoracic region due to the limited range of rotation that occurs at level of the thoracic facet joints.

A horizontal force may lead to a shear injury with resulting bilateral facet disruptions. Avulsions of the spinous processes can occur and are similar to a clay shoveler's fracture of the lower cervical spine (see Image 8).

Fractures of the thoracic spine occur any time the combined forces of compression, distraction, and rotation exceed the strength of the spinal column. The predominant force determines the nature of the fracture or dislocation. An example of a predominately distractive injury is the Chance fracture of the spine. A Chance fracture is usually a lower thoracic spinal fracture and a posterior ligament rupture. It represents a variant of the flexion-distraction injury pattern.

Usually, a minor anterior vertebral compression occurs. When the anterior column fails in tension, a flexion-distraction fracture results, which primarily involves compression of the anterior column and distraction of the middle and posterior columns. Of patients with flexion-distraction injuries, 50% have rupture of the interspinous ligament, the ligamentum flavum, the facet capsule, the posterior annulus, and the thoracodorsal fascia. A traumatic compression fracture in a young patient (eg, after a motor vehicle accident) should be considered a possible Chance fracture.

Frequency

United States

The most commonly injured area of the thoracic-lumbar spine is the thoracolumbar junction. More than half of all injuries to the thoracolumbar spine occur between T12 and L2. In the young adult, thoracic spinal fractures are commonly associated with multisystemic blunt trauma. The occurrence of spinal fractures in a serious motor vehicle accident is 5-6%, with L1, L2, and T12 as the most common levels of injury.

Injuries are most common in patients aged 30-39 years and least common in persons younger than 18 years. Compression fractures are the most common injury in the thoracic spine. Compression deformities of the vertebral bodies are more common among elderly women than among other individuals.

International

Spinal fractures in the lower thoracic and upper lumbar spine occur in all nations as a result of accidents and industrial injuries. The incidence of such injuries is proportionate to the number of motorized vehicles. In the developing nations of Asia, spinal fractures are frequently associated with spinal tuberculosis as well. Trauma related to military action occurs on a regional basis, as reflected in current international relations.

Mortality/Morbidity

Thoracic spinal fractures may be associated with aortic rupture and other severe injuries associated with high-speed accidents. Sudden death may result from related injuries. Because disruption of the thoracic spinal cord does not interrupt vital functions such as respiration, thoracic spinal fractures are less likely than other fractures to directly result in death. Urinary dysfunction and spinal cord shock may lead to premature death in some patients.

The principle effects of thoracic spine injury are pain and neurologic dysfunction. Spinal pain may be seen in patients with acute fractures and fractures associated with advanced age. Although estrogen generally helps to prevent compression fractures in postmenopausal women, an increased risk of chronic pain related to thoracic spine fractures has been reported with estrogen therapy. This occurred despite a higher prevalence of vertebral fractures in women who have never used estrogen.

• Immediate surgical decompression of the spinal canal is indicated for burst fractures that are associated with a significant degree of spinal canal narrowing. An anterior surgical approach has been advocated because of limited access to retrodisplaced bone fragments with a posterior approach. An aggressive approach, including anterior decompression, is most important in patients with partial spinal cord injury patterns. Improvement was reported in patients in whom partial neurologic function was preserved following injury; however, patients with complete paraplegia failed to show any recovery.
• The probability of recovery after a thoracic spinal burst fracture can be predicted on the basis of the initial fracture pattern. The initial severity of paralysis is not closely correlated with initial fracture patterns or canal compromise demonstrated on CT scans.
  • Neurologic recovery is best for type I or type II fractures with kyphosis greater than 15°. Such injuries have been associated a neurologic recovery rate of greater than 90%.

  • Type III fractures with kyphosis less than 15° and maximal canal compromise are associated with a neurologic recovery rate of less than 50%.

  • Type IV fractures with kyphosis of 15° or less and maximal canal compromise at the level of the ligamentum flavum are associated with variable neurologic recovery. A kyphosis of greater than 15° is associated with a prognosis better than that of a purely compressive injury with little kyphosis.
• Although the degree of kyphosis is not always accurately predictive of a neurologic injury on initial presentation, the best likelihood for recovery is associated with a kyphosis of 15° or greater with only a moderate degree of spinal canal compromise. The deformity of the anterior column is associated with less compromise of the spinal canal, and in general, a better long-term outcome.

• Surgical repair, including anterior decompression, posterior fusion with decompression, and use of multisegmental hook systems, provides added spinal canal diameter and multiple points of distraction on the same spinal rod. Transpedicle screws and posterior fixation plates serve to stabilize the facets while preventing further kyphotic deformity. After the cause of compression is removed, patients rarely lose further cord or cauda equina function after anterior decompression. Most patients who present with a motor deficit improve by at least 1 class in motor strength, whereas patients with conus medullaris injury demonstrate partial neurogenic bowel and bladder recovery.

Race

Bone density may be greater in some black men and women. Compression fractures of elderly women are more common in Caucasian women than in black women. Postmenopausal estrogen use is associated with fewer spinal compression fractures but an increased likelihood of back pain and impaired back function in elderly white women.

Sex

To the extent that males participate in at-risk behaviors and have more accidents, young males are more likely to fracture the thoracic spine. Compression fractures are more common among older women.

Age

Two age distributions are noted in the occurrence of thoracic spinal fractures.

• In young athletes, an increased frequency of abnormal radiologic findings of the thoracolumbar spine is noted in various sports. Among young elite skiers (ski jumpers), a significantly higher rate of anterior endplate lesions of the thoracic spine was demonstrated than among control subjects. This was attributable to excessive loading and repetitive high-velocity trauma to the immature spine. Other high-risk activities, such as climbing, motorcycle racing, and skydiving, have been associated with an increased occurrence of compression and burst fractures of the thoracic spine.
• At the other end of the age spectrum, compression fractures occur more commonly in middle-aged women and older women and men, often with minimal trauma.
• A kyphosis of the thoracic spine in an older woman is more likely to be benign and related to osteoporosis than directly related to trauma. Age-related thoracic kyphosis is common in older women.

Anatomy

The thoracic vertebrae have 2 costal facets on each side, one along the upper and the other along the lower edge at the junction of the body with the arch (see Images 2-3). In reality, each facet is a demifacet that, together with the demifacet of the adjacent vertebra, forms a cup-shaped depression for articulation with the head of a rib. The spinous processes of the T2-T12 are long and slope sharply downward. The laminae are broad and sloping and overlap.

The transverse processes extend posteriorly and laterally. Each has a small facet for articulation with the tubercle of the corresponding rib. The superior articular facets face backward, upward, and medially, while the inferior articular facets face forward and laterally. The thoracic vertebral bodies normally slope anteriorly resulting in a mild kyphosis (see Image 5, Image 7). The natural curve of the upper thoracic spine is a reversal of the lordotic curve of the cervical region (see Image 8). The kyphosis of the thoracic vertebral region may increase with age (see Image 9).

The transverse diameter of the pedicle ranges from a mean ± a standard deviation of 4.5 mm ± 1.2 in the fourth thoracic vertebra to a mean of 7.8 mm ± 2.0 in the 12th thoracic vertebra. The pedicles are inclined anteromedially with an angle that ranges from 0.3° toward the midline in the 12th thoracic vertebra to 13.9° in the fourth thoracic vertebra. Lateral flexion (abduction and adduction) is facilitated by this arrangement. The spinal canal is narrow in the thoracic region relative to the size of the spinal cord. Dorsal and ventral nerve roots fuse laterally to form a thoracic nerve with the same number as the vertebral body and rib. Each thoracic nerve serves a specific dermatome of the trunk (see Image 1).

The structure of the thoracic spine can be considered to comprise anterior, middle, and posterior columns. Bony structures of the thoracic vertebral column, intervertebral disks, and ligaments contribute to the flexible strength that allows flexion, extension, rotation, and limited lateral movement of the thoracic vertebral column (see Image 4). Ligamentous structures include the anterior longitudinal ligament, posterior longitudinal ligament, supraspinous ligament, ligamentum flavum, and interspinous ligament. The facet joints of the thoracic region articulate with an anterior-posterior orientation (see Image 6).

Clinical Details

Traumatic compression fractures represent a primarily vertical load injury with anterior or lateral flexion causing failure of the anterior column. The middle column remains intact and may act as a hinge. These fractures are usually stable and rarely involve neurologic compromise. The Denis classification system includes 4 types of compression fractures: (1) involvement of both endplates, or type A; (2) involvement of the superior endplate, or type B; (3) involvement of the inferior endplate, or type C; and (4) buckling of the anterior cortex with both endplates intact, or type D.

A thoracic spine burst fracture results from hyperflexion, which produces wedge compression of one or more vertebral bodies. Because of the rigidity of the ribcage, most of these fractures are stable. The thoracic spinal canal is narrow in relation to the spinal cord; therefore, thoracic spinal cord injuries are commonly complete. A kyphosis greater than 30° requires internal stabilization to prevent further deformity. Dural laceration with impaled nerve roots can be anticipated at the time of surgery if a patient with neurologic damage has a burst fracture of a vertebral body combined with a laminar fracture at the same level.

The principal treatment for unstable thoracic spine fractures is surgical fixation with spinal canal decompression as needed. Instability usually is associated with a kyphosis of 30° or more. The primary posterior approach may use the Harrington rod system. Adverse effects, including the locking of 5-7 segments and incomplete reconstitution of the vertebral height, have been reported. An alternative posterior approach involves transpedicular screw fixation in which 2 segments are fused. The procedure results in both fracture reduction and fixation. The injured vertebra also is grafted through the pedicle. Clearance of bone fragments from within the spinal canal is an important goal for most surgical approaches to thoracic spine fractures. Patients with complete paraplegia can be expected to remain unchanged. Spinal fracture lines are stabilized in patients with spinal injuries and fixed neurologic deficits.

Preferred Examination

In general, anteroposterior (AP) and lateral radiographs should be obtained in the emergency department while other measures of resuscitation are performed. Spiral CT scans with intravenous contrast enhancement are indicated in most patients to exclude intrathoracic vascular injury. MRI of the thoracic spine should be reserved for patients with neurologic deficits or patients with spinal canal compromise who are unable to provide a full neurologic history.

Most patients who present with thoracic injury have a pulmonary, rib, or vascular injury. The expense and delay of obtaining routine CT scans of the thoracic spine are not justified. A review of the bone windows of thoracic CT scans indicates most major deformities associated with Chance fracture, distraction injury, and burst vertebral fractures. The more complex injuries can be studied later if necessary, but multisections CT studies can be reformatted to examine the thoracic spine in a lateral (sagittal) view. The application of MRI in spinal trauma should be linked to a neurologic examination or an evaluation of unexplained severe spinal pain.

Radiography

Radiography should be the initial examination in all patients in whom thoracic spine trauma is suspected. AP views of the chest often provide only a limited depiction of the thoracic spine structures. Specific radiographs of the thoracic spine are usually necessary. Lateral radiographs outline the general shape of the vertebral bodies and provide an appreciation of the normal spinal curves (see Images 5-6).

By examining the lateral shape of the vertebral bodies, significant compression fractures, traumatic kyphosis, and vertebral translation injuries can be appreciated (see Image 1). The AP view of the thoracic spine demonstrates the outline of the vertebral bodies. Important landmarks on anterior views of the thoracic spine include alignment of the spinous processes and continuity of the thoracic spine facet joints. Distraction of the interspinous process alignment may indicate a rotational or distractive thoracolumbar spinal fracture. Disturbance of the paravertebral stripes by hemorrhage may be an important clue to the presence of a fracture.

As a result of the anterior-to-posterior orientation of the spinal facet joints, oblique views of the thoracic spine are less helpful than oblique views of the lumbar spine. Flexion and extension views are helpful if subluxation is detected or if a chronic injury may be present; however, dynamic lateral imaging usually is limited to patients with significant postoperative reconstructions. In all patients with compression fractures, the anterior height of the vertebral body is diminished, while the posterior height remains within normal limits. No subluxation of vertebral bodies is present. The anterior compression is less than 40% unless a burst fracture is present.

Computed tomography

After conventional radiography, CT is the primary means used to depict the posterior elements, which is necessary to exclude the possibility of a Chance fracture. CT scans reveal the spinal canal better and help in estimating the degree of neural compromise. In a burst fracture, CT scans best demonstrate posterior spinal element involvement. Axial CT scans fail to demonstrate subtle horizontally oriented injuries of the vertebral bodies, pedicles, or lamina. Axial CT scans also may miss minimal vertebral body compression fractures. Frontal and sagittal reformation, together with very thin primary images, can overcome most of these limitations.

Magnetic resonance imaging

MRIs of the thoracolumbar spine provide information that is not available using CT scans. Early in an injury, T1-weighted spin-echo (SE) axial and sagittal images may demonstrate the high signal intensity related to acute hemorrhage, including the rare complicating epidural hemorrhage. Both T2-weighted fast SE (FSE) and fluid-attenuated inversion recovery (FLAIR) images demonstrate the high signal intensity associated with edema of bone marrow fat. Gradient-echo T2-weighted images best outline the shape and structure of the vertebral body and the posterior spinal elements.

These MRI sequences are superior to CT scans for detection of a posttraumatic herniated disk, ligamentous edema, and spinal cord compression. Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) contrast enhancement should be used in evaluating suspected metastatic disease and septic spondylosis, diskitis, or osteomyelitis.

Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have recently been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans. As of late December 2006, the FDA had received reports of 90 such cases. Worldwide, over 200 cases have been reported, according to the FDA. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble

movingor straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.

Nuclear medicine

Occult injury associated with thoracic vertebral body compression may be better understood using nuclear medicine bone scans. Technetium 99m–labeled hydroxydimethylpyrimidine is most commonly administered for this test. Chronic injuries demonstrate moderately increased activity, whereas acute fractures usually demonstrate a focally abnormal uptake 24 hours after a fracture.

Limitations of Techniques

Radiographs may not demonstrate the posterior spinal elements clearly, making the exclusion of a Chance fracture difficult.

Axial CT scans may fail to depict subtle horizontally oriented injuries of the vertebral bodies, pedicles, or lamina. Axial CT scans may also cause minimal vertebral body compression fractures to be missed. Frontal and sagittal reformation, with very thin sections for primary images, can be used to overcome most of these limitations.

The resolution of MRI used in the detection of spinal fractures is limited. Although gradient-echo and T1-weighted SE images outline fractures well, minimally displaced fractures are difficult to see.

Although nuclear medicine bone scans are sensitive to the processes that destroy or injure bone, a positive area of increased uptake on a bone scan is not specific for fracture. Fractures may not be detected for as long as 72 hours after an injury. Resolution of fracture outlines is poor.

DIFFERENTIALS

Section 3 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Other Problems to be Considered

Burst fracture

RADIOGRAPH

Section 4 of 12  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Radiographic features of an anterior compression (wedge) fracture include soft tissue swelling, anterior superior cortical impaction, loss of vertical height of the anterior vertebral body, buckling of the anterior cortex of the vertebral body, trabecular compaction, endplate fractures, and disk-space narrowing.

Among the more serious injuries of the thoracic spine, the burst fracture usually is detected easily by using standard radiographs of the thoracic spine. In the lateral view, the criteria for instability include a greater than 50% loss of vertebral body height, a greater than 20° angulation of the thoracolumbar junction, neurologic injury, and a canal narrowing of greater than 30%. Early surgical repair is indicated for such an injury because additional compression of the fracture and more severe neurologic injury can be expected if weight bearing is attempted without surgical fixation. The normal thoracolumbar spine junction presents with a 0° of angular measurement between the T12 and L1 levels.

Degree of Confidence

The degree of confidence in the initial identification of thoracic spine fractures is related directly to the severity of the spinal deformity and inversely related to technical factors such as the size of the patient, patient movement, and the type of radiologic equipment available.

The degree of compression and changes in the disk interspaces are important factors that help in determining if a compression fracture is clinically significant. A compression with intervertebral disk narrowing of more than 50% has a less favorable prognosis for successful treatment. Beyond acute trauma, anterior wedge fractures are subject to differential diagnostic considerations that include congenital hemivertebra, infections, primary tumors, metastatic tumors, metabolic bone disease, Scheuermann disease, Kummell disease, and Schmorl nodes.

False Positives/Negatives

Many spinal anomalies may be mistaken for a fracture. Horizontal residual venous sinus grooves may appear as suspected fractures. In young children, the anterior corners of the vertebral body may have a small depression, which represents the epiphyseal margin. The ossification centers at the ends of transverse processes may appear as fractures. Ossification centers may be irregular in appearance without pathologic fractures. Spina bifida occulta may occur in the posterior spine at any level. The body of T12 is often slightly wedged anteriorly, described as physiologic wedging.

Asymmetry of the pedicles of the lower thoracic spine has been reported in 7% of persons without spinal fracture. The best interobserver agreement can be obtained by measuring from the superior endplate of the vertebral body 1 level above the injured vertebral body to the inferior endplate of the vertebral body 1 level below.

A congenital butterfly vertebral body appears as a compression fracture viewed in the lateral projection. Superimposed shadows of the glenoid process of the scapula may give a false impression of a compression fracture when viewed in the lateral project, whereas the outline of the mandible may suggest a fracture in an anterior view. False-positive findings can result from previous (chronic) kyphosis due to osteoporosis or prior injury. Kyphosis after trauma is best compared by using prior lateral radiographs if such images are available.

CT SCAN

Section 5 of 12  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Thin-section axial CT performed by using a bone algorithm is the single most sensitive means by which to diagnose fractures of the thoracic spine. Routine helical CT scans of the thoracic spine are valuable because multisection CT scanners can generate high-resolution spinal images, even during a primary multisystemic trauma evaluation.

Good-quality CT imaging depicts more thoracic spinal injuries than do conventional radiographic studies; however, the percentage of clinically important spinal fractures seen in the thoracic region on CT scans and not seen on radiographs is lower than similar studies in the evaluation of cervical spinal fractures. Most of the fractures missed on radiographs were spinous process fractures, transverse processes fractures, and fractures in large patients.

In general, the appearance of fractures on CT scans is similar to that seen by using radiographs of the thoracic spine. As a result of its superior contrast definition and the absence of superimposed structures, CT imaging of the spine is highly effective and accurate in the diagnosis of fractures. The confidence level for the diagnosis of a thoracic spinal fracture by using 2-mm axial sections (possible with a multisection CT unit) is greater than 98% and reportedly 99%. Because axial CT is performed with patients in a neutral position, bony distraction of the fracture fragments and subluxations of the spinal articulations may not be as significant on CT images as on they are on acute trauma-series radiographs.

The level of a burst fracture and the percentage of spinal canal stenosis have been correlated with associated neurologic deficits. A significant correlation exists between neurologic deficit and the percentage of spinal canal stenosis. The higher the level of injury, the greater the probability of neurologic deficit. This association may be related to the smaller canal diameter in the upper thoracic spine. The severity of neurologic deficit cannot be predicted.

Degree of Confidence

The confidence level for the diagnosis of a thoracic spinal fracture with 2-mm axial sections (possible with a multisection CT unit) is greater than 98% and reportedly 99%.

False Positives/Negatives

Because axial CT is performed with the patient in a neutral position, bony distraction of the fracture fragments and subluxations of the spinal articulations may not be as significant on CT images as on acute trauma-series radiographs.

False-positive results may occur in patients with a Schmorl node, which is a chronic internal herniation of the vertebral disk into the thoracic vertebral body endplate and failure of the fusion of the anterior vertebral endplate epiphysis, resulting in a limbus vertebra. False-negative CT studies may occur in chronic stress injuries and in severe generalized osteoporotic endplate fractures.

MRI

Section 6 of 12  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Thoracic spinal MRI can demonstrate many vertebral fractures and most abnormalities of alignment. The patterns of injury are similar to those demonstrated on radiographs. MRI is superior to both radiography and CT in the detection of soft tissue injury to the ligaments, facet capsules, and prevertebral spaces. MRI is unique in the ability to depict epidural bleeding and spinal cord injury. Injury to the thoracic cord is particularly critical because such injury may result in paralysis. However, MRI has fewer line pairs of resolution than does CT, which makes MRI a secondary method for fracture evaluation.

With a T2-weighted gradient-echo technique, the cortical break can be demonstrated in some fractures. MRI is superior to CT in the identification of the indirect signs of a fracture, such as paraspinal edema or hemorrhage, epidural bleeding, and sprains of the paraspinal and intraspinal ligaments.

A gradient-echo sagittal T2-weighted MRI of the spine demonstrates the compression fracture by showing the cortical bone as dark (black), while the T2-weighted quality shows cerebrospinal fluid and spinal cord edema as bright (white). Subacute hemorrhage within the spinal cord or in the epidural space may be seen as a susceptibility area of lost signal brightness.

Degree of Confidence

Thoracic spine MRIs demonstrate many vertebral fractures and most abnormalities of alignment. MRI is superior to CT in the identification of indirect signs of a fracture, such as perivertebral edema or hemorrhage, epidural bleeding, and sprains of the paraspinal and intraspinal ligaments. Associated injuries to intracranial structures are evaluated better by using MRI than CT imaging.

False Positives/Negatives

False-positive MRI results are often associated with movement artifacts of metal near the site of injury. Blood-vessel canals may mimic bone injury. The use of upper cervical and intracranial magnetic resonance angiography may help in differentiating certain vascular variations.

False-negative findings may result from motion on the part of the patient. Artifacts related to implanted metal may mask spinal fractures. In older patients or in patients with known neoplastic disease, a pathologic fracture should be considered. In these patients, MRI with Gd-DTPA enhancement demonstrates a spinal mass or osteomyelitis. MRI has less line-pair resolution than does CT scanning. With T2-weighted gradient-echo sequences, the cortical break can be demonstrated in some fractures; however, even with adequate MRI technique, minimally displaced fracture lines may not be seen by using MRI.

ULTRASOUND

Section 7 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

The use of thoracic ultrasonography is usually limited to the localization of pleural effusions, which may occur after significant thoracic spinal and chest wall injury. Diagnostic thoracentesis is more easily performed by using sonographic guidance. Paraspinal abscess may be localized prior to aspiration in select patients.

Degree of Confidence

As a result of the limitations of sonographic studies of bone and the lungs, sonography should be used only in specific patients.

False Positives/Negatives

Ultrasound does not penetrate the air in the lungs or the bones of the spine and ribs. Ultrasonography may be applied in select patients for localization studies.

NUCLEAR MEDICINE

Section 8 of 12  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Nuclear medicine studies have a limited role in the acute phase of thoracic spine injury; however, in a possible congenital anomaly, an acute fracture can be differentiated from a limbus vertebra.

After 12-24 hours, a bone scan with technetium-99m hydroxydimethylpyrimidine demonstrates increased uptake in the area of a fracture. Later in the clinical course, persistent back pain may be explained by a nondisplaced facet injury or pedicle fracture, which is also associated with an area of increased uptake. After surgery or in open spinal fractures, diskitis and osteomyelitis can be identified by focal areas of increased activity; however, indium 111–tagged white blood cells (WBCs) act as a more specific agent in the detection of abscess and osteomyelitis. Unfortunately, ¹¹¹In-tagged WBC scans have a poor sensitivity for the detection of diskitis.

Fat-saturated T1-weighted MRI with intravenous gadolinium enhancement may demonstrate the enhancement of osteomyelitis or diskitis, even in cases in which the ¹¹¹In WBC scan was negative. MRI is also superior in the detection of an associated epidural abscess.

In cases in which MRI is contraindicated (pacemaker, aneurysm clip, etc) or in the presence severe MRI artifacts resulting from fixation plates, wires, or screws, a combined ^99mTc hydroxydimethylpyrimidine-gallium scan is recommended. In all patients, the tomographic qualities of single-photon emission computed tomography (SPECT) improve both accuracy and specificity.

Degree of Confidence

In the absence of prior surgery, radionuclear bone imaging is fairly sensitive. If bone scans are needed, SPECT should be applied in all patients with suspected upper thoracic spine trauma.

False Positives/Negatives

Many false-positive findings can be expected in older adults. Osteomyelitis, diskitis, metastatic disease, degenerative spondylosis, rheumatoid arthritis, and ankylosing spondylitis may result in abnormal spinal images that are not related directly to acute trauma. In the young child, variations of thoracic spine development may mimic acute injury. SPECT helps improve visualization of these conditions, reducing the occurrence of false-positive findings

False-negative results may occur in the first hours after an acute trauma. If possible, 24 hours should be allowed to pass prior to attempting nuclear bone scans of the thoracic spine.

ANGIOGRAPHY

Section 9 of 12  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Findings

Angiography has a limited but critical indirect role in the assessment of thoracic spinal injury. After a gunshot wound to the chest, injuries to the aorta and the proximal great vessels are best evaluated by using angiography. New higher-resolution CT angiography makes catheter angiography less essential. Evaluation of injury to the aorta, subclavian arteries, and innominate artery are routinely performed during the assessment of patients with multisystemic trauma. Trauma, including arterial laceration with hemorrhage, may be seen associated with displaced rib and transverse-process fractures.

Degree of Confidence

The higher resolution of digital subtraction angiography results in excellent image quality. Rarely are other vascular images necessary. Use of angiography is typically reserved for possible interventional repair of arterial injuries and in patients in whom the diagnosis is confused.

False Positives/Negatives

Standing waves within the proximal carotid artery or innominate artery may mimic vascular injury with spasm. In the older adult, arteriosclerotic vascular disease may mimic spasm. Intercostal arteries may be in spasm at the time of an examination, preventing localization of a bleeding site.

INTERVENTION

Section 10 of 12  

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• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Primary intervention in thoracic spinal fractures is unusual. Occasionally, the placement of a lumbar spine drainage catheter improves the likelihood of primary closure of a dural tear in the thoracic area. Intraoperative radiography provides important information that may require consultation in the operating room between the radiologist and the surgeon. A pleural effusion may need to be drained in patients with chest wall trauma. Thoracentesis is most easily performed by using ultrasonographic guidance.

Flexion-extension maneuvers are well within the normal range of motion of most patients with spinal fusion. After the initial period of healing of 12-24 weeks, moderate flexion-extension movements are safe. Instability and subluxation indicate a primary failure of the fusion surgery.

Medical/Legal Pitfalls

• The primary legal pitfall is the failure to diagnose an injury that later may result in neurologic deficits that prompt diagnosis and treatment may have prevented.
• Key elements in avoiding legal pitfalls involve prompt correct interpretation of the initial spinal radiographs with direct communication of important results to the treating physician.
• • Comparison of the current studies with prior thoracic spinal imaging studies may further enhance the understanding of the current medical problem.
  • The direct recommendation for repeated or more advanced imaging (eg, MRI or nuclear medicine studies) has been increasingly emphasized in recent court decisions.

MULTIMEDIA

Section 11 of 12  

• Authors and Editors
• Introduction
• Differentials
• Radiograph
• CT SCAN
• Mri
• Ultrasound
• Nuclear Medicine
• Angiography
• Intervention
• Multimedia
• References

Media file 1:  Thoracic spine trauma. Drawing of the thoracolumbar spine viewed from an oblique frontal projection. SC indicates the spinal cord; NP, nucleus pulposus; VB, vertebral body; AF, annulus fibrosis; VNR, ventral nerve root; SN, spinal nerve; TP, transverse process; DNR, dorsal nerve root; and NRG, nerve root ganglion.
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Media file 2:  Thoracic spine trauma. Axial drawing of a typical thoracic vertebral body viewed from above. The thoracic vertebral bodies are unique in that ribs articulate by rib facets (red outline and red arrow) with the correspondingly numbered vertebrae. The superior articular facet (outlined in blue, blue arrow) is oriented along a lateral plane.
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Media file 3:  Thoracic spine trauma. Drawing of a typical thoracic vertebral body viewed in a lateral projection. The superior rib facet, semilunar inferior rib facet and the costal facet provide articulation for the ribs. The articular facet surfaces are oriented laterally. The spinous processes of the upper and mid thoracic vertebrae are angulated caudally.
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Media file 4:  Thoracic spine trauma. Sagittal drawing of the thoracic spine demonstrating the structures that comprise the anterior, middle, and posterior columns. ALL indicates the anterior longitudinal ligament; AF, annulus fibrosus; NP, nucleus pulposus; PLL, posterior longitudinal ligament; SSL, supraspinous ligament; LF, ligamentum flavum; and ISL, interspinous ligament. Lateral drawing of the 3 spinal columns of the thoracolumbar junction. The anterior column is indicated by the black dotted line and includes the anterior spinal ligament, the anterior annulus fibrosis and the intervertebral disk, and the anterior two thirds of the vertebral bodies. The middle column (red dotted line) includes the posterior aspect of the vertebral bodies, the posterior annulus fibrosis, and the posterior longitudinal ligament. The posterior column (blue dotted line) includes all of the spine posterior to the longitudinal ligament (thick blue dotted line).
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Media file 5:  Thoracic spine trauma. Twelve similar thoracic vertebral bodies form the thoracic spine. A rib is attached to each of the vertebral bodies of the same number. The mild kyphosis of the thoracic spine occurs due to the slightly wedged shape of the anterior thoracic vertebral bodies.
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Media file 6:  Thoracic spine trauma. Posterior drawing of the lower thoracic spine. The last rib usually is attached to the 12th thoracic vertebral body. Each thoracic vertebral body articulates with a rib. The facet joints of the thoracic region are oriented in an anterior to posterior direction. The first lumbar vertebral body (blue arrow) is similar to the last thoracic vertebral body (black arrow) except for the absence of a rib at T12.
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Media file 7:  Thoracic spine trauma. Lateral drawing the spine with the natural spinal curves shown by a curved line. A normal lordotic curve of the cervical spine, a mild kyphosis of the thoracic spine, and lordosis of the lumbar region are noted. These curves act to distribute the vertical weight-bearing load most efficiently.
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Media file 8:  Thoracic spine trauma. The natural lordotic curvature of the cervical spine is reversed in the upper thoracic spine to form a kyphosis in the T1-T2-T3 segments in most adults.
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Media file 9:  Thoracic spine trauma. Lateral radiograph of the thoracic spine of a 74-year-old woman. The kyphosis of the thoracic spine is related to osteoporotic failure of the T8 vertebral body. Note the 30-40% wedge-shaped deformity of the T8 vertebra.
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Media file 10:  Thoracic spine trauma. Lateral 3-dimensional maximum intensity projection CT scan of multiple upper thoracic and lower cervical spinous process fractures. The force necessary to fracture the spinous processes of the upper thoracic spine may also involve the lower cervical spine.
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Media file 11:  Thoracic spine trauma. Lower cervical spine facet fracture (same patient as in Image 5). Multiple spinal injuries may occur in a single patient due to the similarity of the mechanisms of injury that affect the lower cervical spine and the upper thoracic spine.
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Media file 12:  Thoracic spine trauma. Three-dimensional CT scan of complex midface fractures including a Le Fort I injury in a patient who had fractures of the upper thoracic and lower cervical spinous processes (same patient as in Images 5-6). Sudden deceleration of the face and skull resulted in severe stress forces on the spinous processes.
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Media file 13:  Thoracic spine trauma. Anteroposterior view radiograph of the lumbar spine demonstrates a narrowed T12 vertebral body height (arrow) consistent with a compression fracture.
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Media file 14:  Thoracic spine trauma. Lateral radiograph of the lumbar spine. In the upper portion of the lumbar radiograph, a T12 compression fracture (arrow) is demonstrated. Superimposed lung and rib shadows make full depiction of the fracture difficult.
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Media file 15:  Thoracic spine trauma. Lateral radiograph of the thoracic spine with compression fracture (arrow) centered in the image. The radiograph demonstrates a 40% anterior compression of the vertebral body.
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Media file 16:  Thoracic spine trauma. Lateral radiograph of the lumbar spine in a patient with chronic renal disease. Metabolic bone disease, such as renal osteodystrophy (arrow), results in more frequent and more severe compression fractures.
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Media file 17:  Thoracic spine trauma. Axial CT scan of a T12 compression fracture demonstrates a fracture line through the anterior body of the T12 (white arrow), posterior displacement of the T12 vertebral endplate (black arrow) into the spinal canal, and a fracture of the left transverse spinous process.
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Media file 18:  Thoracic spine trauma. Axial and sagittal CT images of an acute lower thoracic spine compression fracture. Note the paraspinal hematoma (white arrows) and the slight narrowing of the spinal canal at the level of the compression fracture (double yellow arrows).
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Media file 19:  Thoracic spine trauma. Three-dimensional CT scan of the thoracic spine demonstrates a compression fracture.
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Media file 20:  Thoracic spine trauma. Drawing of a Chance fracture of the thoracic lumbar junction. The defect follows an irregular horizontal plane (arrows), which results in disruption of the anterior (black dotted line), the middle column (red dotted line), and the posterior column (blue dotted line).
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Media file 21:  Thoracic spine trauma. Sagittal MRIs in a patient with acute spinal injury resulting from a motor vehicle accident. A, Fast spin-echo MRI demonstrates a combined fracture compression of vertebral bodies of T8 and T9. A small fragment of bone compromises the spinal canal and is in contact with the spinal cord. B, Gradient-echo T2-weighted image better defines the bone fragment within the canal (arrow). This fracture was associated with a partial spinal cord injury in which loss of motor function occurred with preservation of distal sensory function.
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Media file 22:  Thoracic spine trauma. Anterior view of multiple spinal cord contusions caused by burst compression fractures of the middle and lower thoracic spine.
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Media file 23:  Thoracic spine trauma. Sagittal CT scan of the thoracic and lumbar spine demonstrates a complete distraction fracture at the L1-2 interspace (arrow).
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Media file 24:  Thoracic spine trauma. Drawing illustrates the mechanism of injury causing a Chance fracture.
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Media file 25:  Thoracic spine trauma. Axial CT image of an unstable fracture of the thoracic spine. Note the association of compression of the vertebral body with laminar and pedicle fractures. Injury to the anterior, middle, and posterior columns results in an unstable fracture.
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Media file 26:  Thoracic spine trauma. Coronal multiplanar reformatted CT images of an unstable thoracic spinal fracture. The association of both anterior compression and lateral subluxation (arrows) indicates instability.
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Media file 27:  Thoracic spine trauma. Sagittal MRIs of the thoracic spine in a patient who had a complete spinal cord injury. A, Sagittal fast spin-echo T2-weighted MRI demonstrates disruption of the anterior longitudinal ligament (white arrow) and a wide distraction of the T9-T10 facets joints (yellow arrow). The spinal cord between T8-T9 and T9-T10 is disrupted with poorly defined margins. B, Sagittal gradient-echo T2-weighted MRI demonstrates the ligamentous injuries anteriorly (white arrow) and posteriorly (black arrow).
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Media file 28:  Thoracic spine trauma. Sagittal T1-weighted MRI image of a compression fracture of the lower thoracic spine. The forces causing a Chance fracture include vertical loading and forward rotation around a fixation point, which often is a seatbelt.
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Media file 29:  Thoracic spine trauma. Gradient-echo T2-weighted sagittal MRI image of a compression fracture. The T12 vertebral body has lost vertical height (white arrow). The spinal canal has been narrowed. Note the disruption of the posterior spinal ligaments (black arrow).
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Media file 30:  Thoracic spine trauma. Chance fracture of the T12 resulting in lower thoracic cord injury. Note the edema of the lower thoracic spinal cord (arrow) resulting from the T12 fracture and the associated hyperflexion injury.
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Media file 31:  Thoracic spine trauma. Axial T1-weighted MRI image of the thoracic spine in a patient with a burst injury of the T12 vertebral body. A large bone fragment has entered the spinal canal resulting in posterior displacement of the conus (arrow).
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Media file 32:  Thoracic spine trauma. Volume maximum intensity projection CT image of the entire thoracic spine demonstrates spinous process fractures of the C7 through T7 vertebra. Although spinous process fractures of the T1 may occur in a manner similar to a clay shoveler's fracture of the C6 or C7, middle and lower thoracic spinous process fractures most likely occur due to a combination of forward flexion and axial rotation. Note the lack of findings of compression vertebral body fractures.
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Media file 33:  Thoracic spine trauma. Three-dimensional surface CT image of the cervical spine (same patient as in Image 24). Note the spinous process fractures of the C6, C7, and T1. CT examination of both the cervical and the thoracic spine was obtained as a single study using a multisection CT scanner. All images were obtained by using a 3-mm reconstruction with 1.5-mm collimation. Scanning times were 0.5 seconds per rotation. These 3-dimensional images were reconstructed by using an independent imaging workstation. In complex cases, reconstructed images are very useful in consultation with treating physicians.
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Media file 34:  Thoracic spine trauma. Scout view image from a spiral CT scan shows a complete subluxation fracture (curved blue lines) of the lower thoracic spine. Such an injury combines lateral displacement with rotational injury (arrow).
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Media file 35:  Thoracic spine trauma. Fracture dislocation of the lower thoracic spine. Axial CT image demonstrates the large distance that the lower thoracic spine has been displaced.
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Media file 36:  Thoracic spine trauma. Sagittal T2-weighted MRI of the thoracolumbar junction demonstrates a complete dislocation at the T12-L1 interspace (arrow).