Introduction
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).
Presentation
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.
Differential Diagnoses
Lumbar Spine, Trauma
Spondylodiskitis
Spondylolisthesis
Spondylolysis
Stress Fracture
Syringohydromyelia
Other Problems to Be Considered
Burst fracture
More on Thoracic Spine, Trauma |
 Overview: Thoracic Spine, Trauma |
| Imaging: Thoracic Spine, Trauma |
| Follow-up: Thoracic Spine, Trauma |
| Multimedia: Thoracic Spine, Trauma |
| References |
| Next Page » |
References
Chance CQ. Note on a type of flexion fracture of the spine. Br J Radiol. 1948;21:452-3.
Dall BE, Stauffer ES. Neurologic injury and recovery patterns in burst fractures at the T12 or L1 motion segment. Clin Orthop. Aug 1988;(233):171-6. [Medline].
Denis F. The three column spine and its significance in the classification of acutethoracolumbar spinal injuries. Spine. 1983;Nov-Dec;8(8):817-31. [Medline].
Denis F. Spinal instability as defined by the three-column spine concept in acute spinaltrauma. Clin Orthop. 1984;Oct;(189):65-76.
Esses SI, Botsford DJ, Kostuik JP. Evaluation of surgical treatment for burst fractures. Spine. Jul 1990;15(7):667-73. [Medline].
Fontijne WP, de Klerk LW, Braakman R, et al. CT scan prediction of neurological deficit in thoracolumbar burst fractures. J Bone Joint Surg Br. 1992;74(5):683-5.
Holmes JF, Miller PQ, Panacek EA, et al. Epidemiology of thoracolumbar spine injury in blunt trauma. Acad Emerg Med. Sep 2001;8(9):866-72. [Medline].
Kostuik JP. Anterior fixation for burst fractures of the thoracic and lumbar spine with or without neurological involvement. Spine. Mar 1988;13(3):286-93. [Medline].
McAfee PC, Bohlman HH, Yuan HA. Anterior decompression of traumatic thoracolumbar fractures with incomplete neurological deficit using a retroperitoneal approach. J Bone Joint Surg Am. Jan 1985;67(1):89-104. [Medline].
Musgrave DS, Vogt MT, Nevitt MC, Cauley JA. Back problems among postmenopausal women taking estrogen replacement therapy: the study of osteoporotic fractures. Spine. Jul 15 2001;26(14):1606-12. [Medline].
Nicoli EA. Fractures of the dorso-lumbar spine. J Bone Joint Surg. 1949;31B:376-94.
Olerud S, Karlstrom G, Sjostrom L. Transpedicular fixation of thoracolumbar vertebral fractures. Clin Orthop. Feb 1988;227:44-51. [Medline].
Purcell GA, Markolf KL, Dawson EG. Twelfth thoracic-first lumbar vertebral mechanical stability of fractures after Harrington-rod instrumentation. J Bone Joint Surg Am. Jan 1981;63(1):71-8. [Medline].
Rachbauer F, Sterzinger W, Eibl G. Radiographic abnormalities in the thoracolumbar spine of young elite skiers. Am J Sports Med. Jul-Aug 2001;29(4):446-9. [Medline].
Vaccaro AR, Rizzolo SJ, Allardyce TJ, et al. Placement of pedicle screws in the thoracic spine. Part I: Morphometric analysis of the thoracic vertebrae. J Bone Joint Surg Am. Aug 1995;77(8):1193-9. [Medline].
Vaccaro AR, Rizzolo SJ, Balderston RA, et al. Placement of pedicle screws in the thoracic spine. Part II: An anatomical and radiographic assessment. J Bone Joint Surg Am. Aug 1995;77(8):1200-6. [Medline].
Wheeless. Wheeless' Textbook of Orthopaedics. Available at: http://www.medmedia.com/. Accessed January 18, 2002. [Full Text].
Further Reading
Keywords
Chance fracture, spinal compression fracture, burst fracture, thoracic trauma, thoracic fracture, spinal fractures, seatbelt injury, thoracic fracture-dislocation, Denis classification, Denis fractures
