Trauma Radiography Series: Imaging of the Thoracic & Lumbar Spines


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This radiology continuing education learning module reviews the current practice of trauma imaging of the thoracic and lumbar spine. Finding a fracture in the cervical spine of a trauma patient is reason enough to image the thoracolumbar spine. Spinal cord injury results from trauma, therefore, the radiologic technologist must understand the importance of total spine precautions related to spine injury and patient care. Plain film and CT imaging are discussed in this lesson. The importance of horizontal beam imaging and the diagnostic criteria for different radiograph views are discussed.
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Author: Nicholas Joseph Jr. RT(R) B.S. M.S
Credits: 1.5

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Instructions:

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Objectives

Outline

Section 1.1: Introduction

Section 1.2: Anatomy of the Thoracic Vertebrae

Section 1.3: Anatomy of the Lumbar spine

Section 1.4: The Spinal Nerves

Section 1.5: Plain Film Radiography of the Thoracic Spine

Section 1.6: Plain Film Radiography of the Traumatic Lumbar Spine

Section 1.7: Computerized Tomography of the Traumatic Thoracolumbar Spine

Section 1.8: Conclusions and References

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Trauma Radiography series - Imaging of the Thoracic and Lumbar spines

Objectives:

  • State the rationale for trauma imaging of the thoracolumbar spine.
  • State the occurrence of traumatic spine injury involving the spine from motor vehicle accidents.
  • State the location of most spine injuries to the thoracolumbar spine.
  • State the most common type of vertebral injury to the thoracolumbar spine.
  • List the characteristics of a thoracic vertebra and state the differentiating feature of a thoracic vertebra.
  • List and discuss two types of joints of the spine, their structure and movements.
  • Discuss the structure of the intervertebral joints of the spine.
  • State the number of pairs of spinal nerves and their pattern of distribution for exiting the spinal canal.
  • List what are the standard plain film radiographs for the trauma thoracic spine series.
  • List the diagnostic criteria for the AP radiograph of the thoracic spine.
  • List the diagnostic criteria for the horizontal beam lateral radiograph of the thoracic spine.
  • State the diagnostic criteria for the horizontal beam lateral Swimmer’s view emphasizing the upper thoracic spine.
  • Discuss why complete thoracic spine CT imaging with coronal and sagittal 2D reconstruction is the study of choice at many institutions for the unconscious or intubated trauma patient.
  • State the structures best visualized by the AP and lateral lumbar spine views.
  • State the diagnostic criteria for the AP lumbar plain film radiograph.
  • State the diagnostic criteria for the horizontal beam lateral lumbar spine radiograph.
  • State why helical lumbar spine CT imaging is the study of choice for evaluating the spine of a multi-system injuries patient.
  • State the diagnostic criteria for CT evaluation of the lumbar spine.

Outline

1.1 Introduction
  1. Frequency of thoracolumbar spine injuries.
  2. Indications for imaging the thoracic and lumbar spines.
1.2 Anatomy of a typical thoracic vertebra
  1. Distinguishing feature(s) of thoracic vertebrae.
  2. Diarthroses and syndesmoses joints of the thoracic spine.
1.3 Anatomy of the lumbar vertebrae

1.4 The spinal nerves
  1. Basic sensory modalities of the spinal nerves.
  2. Distribution exit patterns of the spinal nerves.
1.5 Plain film imaging of the thoracic spine

1.6 Plain film imaging of the lumbar spine

1.7 CT Imaging of the thoracic and lumbar spines

1.8 Conclusions

1.1 Introduction

It is common to image the thoracolumbar spine following acute trauma. Some indications for radiographic imaging include pain, bruising, deformity or any abnormal neurological finding related to the thoracic or lumbar spines. In addition, a fracture in the cervical spine is a mandate to image the entire spine. Injuries such as fall from height, motor vehicle accident, and penetrating injury can produce forces that exceed the strength of the vertebrae.

The thoracolumbar junction is the most commonly injured area of the thoracolumbar spine. More than half of these injuries occur between T12 and L2. Motor vehicle accidents with multisystem trauma have an occurrence of 5-6% spinal fractures in the L1-T12 area. Surprisingly these patients are generally between the ages of 30-40 years. Compression injuries are the most common type seen in these cases. Compression deformity is more commonly noted in elderly women than in any other age or gender.

Surveillance thoracic and lumbar spine radiographs are frequently indicated for a trauma patient who cannot be clinically assessed due to unconsciousness. The goal of diagnostic imaging is to correctly identify vertebral fractures, identify injury to the spinal cord and its nerve roots, and to provide data for surgical planning. The emergency room physician makes the decision as to what radiographs are required for each patient; however, the standard views are the antero-posterior (AP) and lateral views of the thoracic and lumbar spines. As a follow up to any suspicious or inadequately visualized areas, CT is the preferred imaging modality. The imaging standards are currently suggestive of reconstruction of the thoracic and lumbar spines from the chest/abdomen/pelvis CT scan of the trauma patient. MRI imaging should follow an abnormal finding from plain film or CT scan. This article will identify imaging procedures most useful in clinical radiography practice.

Therefore, as radiographers, we must know the diagnostic criteria for each image we take, and present it point for point of reference. Nowhere in radiography are the standards for imaging more important than in dealing with traumatic spine injury. This continuing education module applies such a standard to the radiography of the thoracolumbar spine following traumatic injury. This module will briefly review the normal anatomy of the thoracolumbar spine, present some of the universal recommendations for plain film and CT imaging, and show through radiographs how common it is for spine injury to be present following trauma. It is hoped that the reader will gain an appreciation of trauma imaging that will translate into better radiographic imaging and patient care.

1.2 Anatomy of the Thoracic Vertebrae

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There are twelve thoracic vertebrae numbered from superior to inferior. The vertebral bodies get progressively larger from top to bottom in order to bear the weight of the trunk. The vertebral bodies have a forward slope that results in a mild kyphotic curvature of the thoracic column. The outstanding feature of thoracic vertebrae is the presence of articular facets for the attachment of ribs. All thoracic vertebrae articulate with ribs. Some have two half facets called demifacets; these are located laterally on the bodies of T2 to T9. The superior demifacet is for articulation with the head of its own rib and the inferior one for articulation with the head of the rib below it. The other thoracic vertebrae have full single facets for articulation with their ribs.

Examination of spine alignment by palpating the spinous processes of all thoracic vertebrae is possible because of their long presentation. The spinous processes are long and slanted downward for most of the thoracic vertebrae, but the lower ones begin a horizontal transition like the lumbar vertebrae. They differ from cervical vertebrae in that the spinous processes are not bifid, and there are no transverse foramina.

Each transverse process projects posterolaterally and has a facet for articulation with the tubercle of the corresponding rib. The paired inferior articular process and facet face forward and laterally. They articulate with the superior articular processes of the vertebra below it. The superior articular processes and facet project backward, medially and upward to articulate with the inferior articular processes. The arrangement of the facet joints and the attachment of the ribs to the thoracic vertebra give this part of the spine added stability. This in part accounts for fewer injuries in this region of the spine.

There are six joint articulations of the typical thoracic vertebrae with the ribs. Paired ribs have an attachment on both sides of a thoracic vertebra; however, we will only review a unilateral description of these joints. The head of the rib attaches to the superior part of the vertebral body of the same number vertebrae. Its tubercle articulates with the transverse process of the same numbered vertebrae. The head of a rib will also articulate with the inferior demifacet of the vertebra above it.

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This CT axial slice of a thoracic vertebra demonstrates the attachment of the ribs (left). The head of the rib articulates with the vertebral body; it shares another attachment of its tubercle to the transverse process (arrows). The drawing on the right shows the facet articulations on the vertebrae for the ribs (yellow). The apophyseal joint articulation formed by the superior and inferior articular processes is also shown on the drawing.
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This axial CT slice through a thoracic vertebra shows the rib attachments vertebral foramen and spinal cord, and the apophyseal joints. Notice that the superior articular processes face back and the inferior articular processes forward. The partially seen spinous process slopes downward.
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These two 3D CT reconstructions are from axial CT data. They show the articulations of the ribs with the costal facets of the thoracic spine. Notice that the head of each rib articulates with the body of the same numbered vertebra.

Like all typical vertebra the two main parts of a thoracic vertebra are; a large anterior portion called the body and posterior to it is the vertebral arch. The body bares the weight of the trunk, whilst the arch protects the spinal cord and its associated nerve roots. Forming the vertebral foramen are two pedicles that extend from the posterior portion of the vertebral body. Joining them laterally are the two laminae to make up the posterior bony ring. The laminae are broad and sloping and overlap. Successive stacking of vertebral foramen comprises a bony tube like vertebral canal that encloses the spinal cord and its meninges. Projecting from the vertebral arch are two transverse processes that project posterior and lateral. Each has a facet for the articulation of the corresponding rib. Extending posterior from the midline union of the laminae is a single spinous process. They are long and slope sharply downward like roof shingles. The transverse and spinous processes act as levers to which muscles attach to effect movement of the spine. Like all typical vertebrae, each thoracic vertebra has four zygapophyses arising from its arch. These apophyses are the basis of free joint movements of the spine. There are two superior articular processes and two inferior articular processes that bare facets for articulation with adjacent vertebrae. These articular surfaces are where joint movement in the spine takes place. Articulations of superior articular processes of one vertebra and the inferior articular processes of an adjacent vertebra form diarthroses joints, termed an apophyseal joint. Each vertebra articulates with an adjacent vertebra above it and the vertebra below it to share four apophyseal joints, two above and two below. These joints are synovial joints capable of flexion, extension, lateral bending, and rotational movements.

Intervertebral discs are a type of symphyses joints. The disc has concentric outer rings of fibrous tissue called the annulus fibrosus. The center contains a fluid moiety called the nucleus pulposus, which hydrostatically maintains the height of the vertebral column. Running the length of the column anteriorly and attached to the vertebrae and intervertebral discs is the anterior longitudinal ligament. It tends to prevent hyperextension of the column. The posterior longitudinal ligament runs inside the vertebral canal from the atlas to the sacrum. Its attachment is to the posterior aspect of the vertebral bodies and intervertebral disc. It serves to prevent hyperflexion of the vertebral column.

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This sagittal MRI image shows the thoracic spine, anterior and posterior longitudinal ligaments in their anatomical presentation. The anterior longitudinal ligament resists hyperextension of the spine; the posterior longitudinal ligament prevents hyperflexion of the spine.

Section 1.3 Anatomy of the Lumbar spine

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The five lumbar vertebrae are clearly distinguished by their large size, absence of costal facets, and absence of transverse foramina. Peculiar to lumbar vertebrae are short pedicles, an almost horizontal spinous process, and a roughen mamillary process on the posterior border of the superior articular processes. A small accessory process marks the root of the transverse process. Attached to the bodies of the upper lumbar vertebrae are the crura of the diaphragm. The superior articular processes bear vertical facets that are orientated posteromedially. The inferior articular processes have facets that are convex vertically and face anterolaterally. They form the zygapophyseal synovial joints, which are diarthroses type joints of the spine.

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This axial CT thin slice through an upper lumbar vertebra shows the thecal sac outlined with contrast media. Demonstrated is the orientation of the apophyseal joints between the second and third lumbar vertebrae.

The psoas major muscle attaches to all lumbar vertebrae. Within the vertebral foramen of the first lumbar lies the conus medullaris, distal foramina contain the caudal equina and meninges. The intervertebral foramina are relatively large facing laterally. The aorta and inferior vena cava run along the anterior left and right margins of the vertebrae, respectively. The anterior longitudinal ligament continues its attachment to the anterior portions of the lumbar vertebral bodies and their intervertebral disc. Attached to the posterior margins of the vertebral bodies lying within the vertebral canal is the posterior longitudinal ligament.

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1.4 The Spinal Nerves

An injury to a vertebra does not necessarily mean that there is an injury to the spinal cord; neither does injury to the spinal cord require a vertebral fracture for correlation. Neurological examination of the patient and radiographic interpretation by a radiologist is what determines what further testing is needed before a definitive diagnosis can be given. Injuries to spinal nerves or to “soft” tissue are issues in trauma care as well as awareness of bony injury. Traumatic injuries to the spinal cord or the spinal nerves may occur during a trauma event.

This section provides a basic understanding of the gross distribution of spinal nerves, which branch from the spinal cord and exit at various vertebral levels. These are mixed nerves with both sensory to the brain, and motor response from the brain to the body’s muscles. Sensory nerves carry more than just pain or the absence of pain; there is also touch, pressure distinction, two-point discrimination, temperature, proprioreception, and other sensory data the brain uses to formulate a motor response. The clinical physician gathers both sensory and motor data along with diagnostic testing to understand a patient’s injuries. Now let us briefly review the gross anatomy of the spinal nerves and their exit from the vertebral column.

There are thirty-one pairs of spinal nerves having attachments to the spinal cord. There are eight pair of cervical spinal nerves, 12 pair of thoracic nerves, 5 pair of lumbar nerves, 5 pair of sacral nerves, and one coccygeal nerve. The eight pair of cervical nerves exits the spine in the following way: the first cervical nerve exits between the first cervical vertebra and the base of the skull. The second cervical nerve exits between the first cervical vertebra and second cervical vertebra. The distribution of the cervical spinal nerves 3-8 follow the same pattern so that the eighth cervical nerve exits between the seventh cervical vertebra and first thoracic vertebra.

The twelve pairs of thoracic spinal nerves exit from below their numbered vertebra. The lumbar, sacral, and coccygeal nerve all follow the same pattern of distribution from the column. The spinal cord does not extend the length of the vertebral column. In infants, it terminates at L2 or L3, and in the adult at L1/L2 junction. The spinal cord is anatomically and functionally segmented. For example, the area corresponding to L4 is not at the level of the fourth lumbar vertebra because the cord ends at L1. The nerves for the lower lumbar segment, sacrum, and coccyx arise from their segments and descend within the vertebral canal. The length of the nerve roots increase, especially in the lumbar area to form a bundle of nerve roots in the subarachnoid space caudal to the termination of the spinal cord. The nerve roots that extend distal to L2 vertebra are collectively called the cauda equina (L. horse’s tail). The spinal cord ends in a tapered cone shape called the conus medullaris. Extending from the conus is a thin fibrous thread called the filum terminale, which attaches the cord to the dorsum of the coccyx.

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These CT axial images are of the lumbar spine taken following a myelogram. The subarachnoid space and nerve root within the sac can be seen on both images. The image on the right shows the exit site of the intervertebral foramen (white arrow) and distal caudal equina (yellow arrow).

The spinal nerves exit the spinal column through their respective intervertebral foramina. The superior and inferior borders of the intervertebral foramen are the inferior and superior notches of the pedicles of adjoining vertebrae. Posterior are the apophyseal joints and anteriorly the intervertebral disc. This relationship is clinically significant because compression of the nerve roots or dorsal root ganglion can occur at these exit sites. The oblique view demonstrates the intervertebral foramina of cervical vertebrae and the lateral view best demonstrates the lumbar foramina.

Section 1.5 Plain Film Radiography of the Thoracic Spine

For trauma patients a simple chest x-ray alone does not provide sufficient information about the thoracic spine. For a patient suspected of thoracic spine trauma specific radiographs of the thoracic spine are necessary. The standard trauma radiographs are the anterior-to-posterior (AP), horizontal beam lateral, and Swimmer’s view.

AP Thoracic Spine View

The diagnostic standard for the AP view is to include all 12 thoracic vertebrae. Without moving the patient directly, align the mid-sagittal plane by moving the spine board to align the patient. Always maintain spine precautions for the cervical region at all times. It is important to include the seventh cervical vertebra to evaluate subluxation of the upper thoracic spine. The first lumbar vertebra should also be included to evaluate subluxation of the thoracolumbar junction. In keeping with ALARA, use collimation to reduce patient radiation dose. The lateral margins of the film must include the entire transverse processes and a small portion of the ribs for all thoracic vertebrae. Radiographic exposure technique must penetrate the vertebral bodies without burnout of the upper thoracic vertebrae.

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This AP thoracic spine radiograph demonstrates the diagnostic imaging criteria. At least one vertebra above and below the twelve thoracic vertebrae is demonstrated. Lateral collimation is adequate for this study. The vertebral bodies are well penetrated and there is no burnout of the upper thoracic vertebrae.

When properly made the AP radiograph is useful for evaluating the outline of the vertebral bodies. The AP radiograph allows for evaluation of the alignment of the spinous processes and continuity of the facet joints. The anterior-posterior orientation of the thoracic apophyseal joints makes oblique t-spine images useless and nearly never done. The AP view offers good information about the interspinous process alignment and may give cues to rotational dislocation or fracture as do disruption of the paravertebral stripes by hemorrhage. Therefore, the radiographer must accomplish accurate positioning and adequate radiographic exposure technique.

The Lateral T-spine View

The diagnostic standard for the horizontal beam lateral thoracic spine view begins with the visualization of all twelve thoracic vertebrae. Usually this requires a horizontal beam lateral and a Swimmer’s view of the upper thoracic spine (C7 thru T4). To evaluate the height of the vertebral bodies and their posterior architecture the radiographic exposure technique should penetrate all vertebrae. The horizontal beam lateral is a survey type image and the spinous processes may not be entirely included. This is because of the attenuation of the x-ray beam by the tabletop that may occur.

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This horizontal beam lateral thoracic spine image with the patient in the supine dorsal recumbent position. Vertebrae L1 through T2 are demonstrated on this radiograph; however, the upper thoracic (T1 and T2) and seventh cervical vertebra is not adequately demonstrated. This is acceptable for the crosstable trauma lateral view since a Swimmer’s view will be necessary to complete the study. Attenuation of the beam along the posterior border of the image is due to absorption by the tabletop. The amount of attenuation seen on this radiograph is acceptable.
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This crosstable lateral thoracic spine radiograph demonstrates most of the thoracic spine. Considering radiographic technique and patient size this radiograph demonstrates an adequate number of thoracic vertebrae. A Swimmer’s view must be included to demonstrate the upper thoracic and seventh cervical vertebrae. The distal presentation of the first lumbar vertebra allows for evaluation for inferior dislocation.

The Swimmer’s View

The Swimmer’s view helps demonstrate the upper thoracic (T1-T3) and the seventh cervical vertebrae of trauma patients. This view compliments the trauma horizontal beam lateral view. It is an important view for evaluating the relationship of the cervicothoracic junction and upper thoracic vertebrae. The diagnostic criteria for the Swimmer’s view include demonstration of the apophyseal joints, alignment of the vertebral bodies, and the minimum required vertebrae (C7 through T3).

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These two horizontal beam lateral Swimmer’s views demonstrate the diagnostic criteria for thoracic spine imaging. The picture on the right uses a standard radiographic technique on suspended ventilation and the picture on the left uses a breathing technique.

The lateral view gives a good outline of the vertebral bodies and overall curvature of the thoracic spine. The degree of confidence in the evaluation of the thoracic spine alignment, thoracic spine fractures, and the posterior spine elements depend largely on the radiographic technique, patient size, and motion present on the radiograph. To overcome these plain film diagnostic challenges the radiologist may recommend a CT scan, nuclear bone scan or MRI as complimentary studies.

1.6 Plain Film Radiography of the Traumatic Lumbar Spine

There are three radiographic views used to evaluate the traumatic lumbar spine. These are the horizontal beam lateral, the horizontal beam lateral L5/S1 and sacrum, and the AP lumbar spine views. These views have diagnostic criteria that the radiographer must achieve.

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These three radiographs demonstrate the standard trauma views of the lumbar spine. Top picture is a horizontal beam lateral, the bottom left is a horizontal beam L5/sacrum view, and the bottom right is the AP view.

The horizontal beam lateral lumbosacral spine view

Trauma imaging of the lumbar spine begins with a high suspicion for vertebral or spinal cord injury. The patient is supine, fully supported on a spine board, with neck collar and immobilization apparatus in place for trauma imaging. The trauma survey of the lumbosacral spine includes the horizontal beam lateral rather than the recumbent view made on ambulatory patients. By using a horizontal beam, the patient’s spine is stationary for the entire set of radiographs. The patient’s mid-sagittal plane should be aligned perpendicular to the central ray by sliding the spine board to the right position. The radiographic exposure technique should penetrate the entire lumbosacral spine. For most patients a second L5/S1 view will be required; it should include down to the distal coccyx.

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Above is a horizontal beam lateral lumbosacral spine view demonstrating the diagnostic criteria for this radiograph. The sacrum and vertebrae T11 thru L5 demonstrated on this radiograph.
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This picture is a horizontal beam lateral spot film that includes L5/S1 junction and the entire sacrum. It is included as part of the lateral lumbar spine view to image the entire lumbosacral spine. Generally, this view is limited to only the L5/S1 spot for ambulatory patients.

The AP lumbar spine radiograph

The vertical beam AP view is part of the trauma lumbar spine series. Some institutions require the full abdomen view as part of the lumbar AP series. However, the minimum diagnostic criterion is that the lateral collimation should allow for the visualization of both sacroiliac joints. The radiographer must include all vertebrae from the twelfth thoracic through the entire lumbosacral spine. There should be sufficient radiographic exposure to penetrate the vertebral bodies and spinous processes. Soft tissue detail should include the psoas muscles, bowel gas pattern, and urinary bladder.

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This plain film AP lumbar spine radiograph demonstrates the diagnostic criteria. Included are a portion of T12, all lumbar and sacral vertebrae, and the sacroiliac joints. The radiographic exposure well penetrates the spine. Well visualized are the contour of the vertebral bodies, spinous processes, transverse processes, psoas muscles, apophyseal joints, and renal shadows.

Radiographic assessment of the thoracolumbar spine

The radiologists and emergency room physicians use a systematic approach to evaluating spine radiographs. The radiographer should be sure their images meet the criteria for systematic evaluation. Knowing what systematic evaluation entails should be the guide for the radiographer to evaluate the quality of their images. By presenting images that meet each criterion category the radiographer helps the physician avoid missed or delayed diagnoses. Including all of the required anatomy properly positioned, well penetrated, and sufficient bone and soft tissue detail is fundamental to spine assessment.

ABC's of radiographic spine assessment of trauma.

Evaluate for abnormalities of:
  • Alignment and anatomy
  • Bony integrity
  • Cartilage or joint space injury
  • Soft tissue injury

1.7 Computerized Tomography of the Traumatic Thoracolumbar Spine

Computerized axial tomography (CAT or CT) scan is preferred for further evaluation of any abnormal, suspicious or inadequately visualized parts of the spine. Furthermore, many studies have concluded that accurate evaluation of the thoracolumbar spine is possible with targeted image reconstruction of the spine as part of a MDCT (multidetector computerized tomography) chest/abdomen/pelvis trauma protocol. There is high sensitivity and specificity for diagnostic performance of 4-MDCT and 16-MDCT spine reconstruction for patients with multiple traumatic injuries. Sensitivity and specificity for both remain greater than 97% and in some studies, it approaches 99% with a statistically high confidence rating. The performance of CT equipment and technologist expertise are main factors in the quality of axial acquired and multiplanar reformats for interpretation. The thoracoabdominal multi-detector row CT is the acquisition scan to evaluate for aortic and other visceral traumatic lesion.

In this module, we will discuss our standardized trauma protocol using 16-MDCT thin slice reconstructed axial images (1.25 X 1.25 mm) from the helical mode chest/abdomen/pelvis trauma CT scan. The basic protocol calls for reconstructed axial collimated thoracic and lumbar spine images, sagittal 2D reconstructions, and 2D coronal reconstruction if a fracture is present. This protocol has a 99% sensitivity and specificity when the axial images are excellent, which is approximately greater than 85% of studies. Protocols will vary from institution to institution and from scanner to scanner, for example a 4-DCT may only be capable of 3mm slices at 1.25 intervals.

Axial CT Reconstructions

Spine imaging begins with axial thin slice CT reconstructions to include the vertebra above and below the region of the spine requested. For example, for the thoracic spine reconstruct C7 through L1 including the apophyseal joints of C7/T1 and T12/L1. Bone algorithm with detail should also be selected and a small FOV (field of view). The pictures below demonstrate reconstructed CT axial slices through the thoracic spine.

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In this series of three images the CT image on the left is a scanogram with a white line indicating the level of the vertebral slice. Notice that the slice is about midway through the seventh cervical vertebra. Middle and right CT images are axial thin slices through the seventh cervical showing the vertebral foramen, intervertebral foramen and apophyseal joint of C7/T1. Including the cervicothoracic junction on the CT scan is an important part of the protocol for thoracic or cervical spine imaging.
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This series of three CT axial images are samples of thin slice axial reformats of the thoracic spine from the chest/abdomen/pelvis trauma CT survey. These images were acquired using 16-MDCT at 1.25 X 1.25 mm. Upper left image is through the first thoracic vertebra, the middle CT image is from a slightly lower vertebral level. The right image is at the level of the aortic arch. The relative position of each slice documents the natural kyphotic curvature of the thoracic spine. The slant of the white arrow in the picture indicates this curvature. The trachea (T) and aortic arch (A) are good references for the anatomical level of each slice.
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These three axial thin slice CT images are of the thoracic spine at various anatomical levels. On the left is the thoracic vertebra at the level of the pulmonary vessels. The middle image is at a level through the esophagus (E), and the right image is through L1 vertebra, which completes the axial imaging protocol for the thoracic spine.

When there is no fracture present, only the sagittal 2D reconstructions are made of the thoracic and lumbar spines. The radiologist will have an adequate amount of information from this protocol to interpret injuries to the thoracic spine. The 2D sagittal reconstructions should include sufficient thin slices to visualize all apophyseal joints along the longitudinal axis of the spine bilaterally. Include the apophyseal joints on both sides of each vertebral pair throughout the spine. The joints will often be in different planes due to the patient’s position on the spine board, normal kyphotic curvature, and scoliosis. Demonstrate the entire vertebral canal, anterior contour line, and posterior contour lines that frame the vertebral bodies. The spinolaminal line is also to be demonstrated on the sagittal images. This requires the technologist to check each 2D image to make sure the number and slice thickness is adequate for interpretation.

The picture below demonstrates the alignment for sagittal 2D reconstructions of the thoracic spine. The technologist is able to adjust the position, angle, slice thickness and FOV for the reformats.

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This image shows the spacing protocol the technologist selected. Notice that 35 slices were selected which should adequately demonstrate all structures for interpretation. The FOV is the range between the slices from 1-35. The technologist is able to change this range as well as the slice thickness. For example, more slices within the FOV means thinner slices. Adjusting the slice thickness may be necessary to complete the diagnostic criteria for 2D reconstructions.
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These three 2D sagittal reformats from axial CT data demonstrate some of the diagnostic criteria for the thoracic spine. The CT image on the left demonstrates the apophyseal joints along the right longitudinal axis of the spine (white arrow at one joint). The middle CT image gives an accurate representation of the anterior and posterior longitudinal lines and vertebral canal. The CT image on the right shows the soft tissues around the spinous processes very well.
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These three CT images are a continuation of the thoracic spine series above. Partially visualized are the apophyseal joints on the left side of the spine (left CT image). The middle CT image provides useful information, but does not complete the diagnostic picture. Therefore, the technologist should adjust the FOV and/or slice thickness to include all apophyseal joints along the left longitudinal axis. The CT image on the right demonstrates the left lateral margin of the imaging field displayed in the slice series.

CT Imaging of the lumbar spine

The diagnostic criteria and protocol we use for the lumbar spine is the same as for the thoracic spine. A helical chest/abdomen/pelvis CT scan is performed from which axial images of the lumbar spine are reconstructed. These images are used to reformat 2D sagittal images. Again, the vertebra above and below the spine region should be included. This means from T12 through S1 is included in the FOV, and the lateral margins must include both sacroiliac joints. The pictures below are taken with a GE lightspeed 16-MDCT. Slice thickness is 1.25 X1.25 axial reformats from the chest/abdomen/pelvis CT scan.

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These four CT images demonstrate the axial CT imaging protocol for the lumbar spine. The CT image on the left is a scanogram indicating the vertebral level of T12 (white line) through which the first slice is made. The first CT image, next to the scanogram with the liver (L) and the spleen (S) labeled. Notice the ribs attached to the vertebral body and spinous process of T12. Including T12 as part of the superior limit of the lumbar spine CT is in keeping with the protocol to demonstrate the vertebra above the region of interest. On the right middle CT image, the kidney (K) is labeled marking it as a slightly lower lumbar vertebra. Note the orientation of the apophyseal joints on this image, which is typical for lumbar vertebrae. The lumbar vertebra on the far right CT image identified by the psoas muscle (P) is slightly lower.
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These three CT images are a continuation of the lumbar spine series above. From left to right the selected slices descend the lumbar spine to demonstrate parts of lumbar vertebra anatomy. The image on the right shows the apophyseal joints of L4/L5 as the sacrum begins to come into view.
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These three CT images represent the distal portion of the lumbosacral CT protocol. The vertebra below (S1) and the lateral boundaries of the sacroiliac joints demonstrated. The picture to the left shows the top of S1 and the iliac wings. The middle CT image shows S1 and the apophyseal joints of L5/S1 and the beginning of the sacroiliac joints. The right image completes the diagnostic criteria of including the S.I. joints and vertebra below the region of interest.

Sagittal 2D reconstructions are also part of the CT lumbar spine trauma imaging protocol. As with the thoracic spine the apophyseal joints on each side of the longitudinal axis of the column must be visualized. To accomplish this criterion the technologist may need to adjust the number of slices, and position of the FOV.

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The FOV selected by the technologist in this image allows for visualization of the apophyseal joints on each side of the longitudinal axis of the lumbar vertebral column. In order to demonstrate the required anatomy the technologist made forty slices. Each reconstructed slice within the FOV is 1.8 mm spacing. We can see the rationale and results of this selection in the following images.
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The most obvious feature of these sagittal selections is that they cover from T11 through the first sacral segment. The picture on the left is about mid-sagittal and demonstrates the vertebral canal. This is a good image for evaluation of the anterior and posterior contour lines to help r/o dislocation of a vertebra. The middle image shows the apophyseal joints of the thoracic vertebra only. Notice that the patient’s mid-sagittal plane is not aligned evidenced by the apophyseal joints along the spine’s left longitudinal axis not seen in the same image spacing. This is ok, except that the technologist must check subsequent slices to make sure all joints on either side of the column are included.
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These six radiographs (from left to right) demonstrate how multiple thin slice reconstructions can demonstrate the apophyseal joints along the longitudinal axis. Even though they are not all displayed in a single slice the sum of the slices do cover the required criterion. Here we only show a few slices; however, the original set included 35 images that cover joints along both longitudinal viewing planes. To display apophyseal joints along more vertebral levels in a single slice align the patient’s spine parallel to the mid-sagittal plane.

The technologist should make 2D coronal reconstructions whenever there is an abnormal finding on axial images, or if it is their institution’s spine protocol. Coronal images should include soft tissue anterior the vertebral bodies and part of the muscle group posterior to the spinous processes. This will give a coronal viewing of the soft tissue structures about the abnormal area. Adjust the slice thickness to demonstrate the vertebral bodies, articular pillars, and vertebral canal.

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The CT axial slice above shows the alignment for 2D coronal reconstructions. Slices are perpendicular to the spinous process, sufficiently thin to demonstrate the apophyseal joints, vertebral canal, and articular pillars.
image032
These four coronal selections demonstrate the anterior anatomy of the lumbar column. These images are from anterior to posterior (left to right). The lower vertebrae appear first because of the lordotic curvature of the lumbar vertebrae. Note that the lateral margins include the sacroiliac joints (displayed on the two right images) which are a diagnostic criterion. In each of these images, we see the psoas muscles and surrounding soft tissues of the spine.
image033
These four coronal slices are a continuation of the images above. Because we cannot demonstrate all of the apophyseal joints on any single slice, when reconstructing coronal images the technologist must make sure all joints (white arrows) bilaterally are demonstrated at all vertebral levels.

Section 1.8 Conclusions

Plain film imaging of the thoracolumbar spine remains the imaging modality of choice for trauma patients without multitrauma injuries. CT, especially multi detector row CT is currently the most effective method of imaging patients with bony injury. It is useful to evaluate multitrauma injuries that involve the chest/abdomen/pelvis as well as suspected spine injury. Sagittal and coronal reconstructions are extremely useful to demonstrate retropulsed fragments and conditions that compromise the vertebral canal. MRI is the imaging modality of choice for evaluating patients with neurological defect.

References

  1. Stuhlfault, J.W. , Soto, J.A., Blunt Abdominal Trauma: Performance of CT without Oral Contrast Material, Radiology, December 1, 2004; 233(3);689-694.
  2. Brooks RA, Willett KM, Evaluation of the Oxford protocol for total spinal clearance in the unconscious trauma patient. J. Trauma 2001 May; 50(5):862-867).
  3. Watura, R., Cobby, M., Taylor, J. Multislice CT in imaging of trauma of the spine, pelvis, and complex foot injuries, Br.J.Radiol., December 1, 2004; 77(supl_1): 546-563.
  4. El-Khoury, G. Y, New Trends in Imaging of Thoraco-Lumbar Spine Trauma, Virtual hospital at www.vh.org/adult/provider/radiology/thoracolumbarspinetrauma/, May, 2003.
  5. Wintermark, M., Mouhsine, E., Theumann, N., Mordasini, P., Guy van Melle, Leyvraz, Schnyder, P., Thoracolumbar Spine Fractures in Patients Who Have Sustained Severe Trauma: Depiction with Multi-Detector Row CT, Radiology, April 2003, 10.1148/radiol.2273020592. Online at http://radiology.rsnajnls.org/cgi/content/full/227/3/681.

Special thanks to the radiographers and physicians at Regions Hospital in St. Paul, Minnesota, a Level I trauma center, for their expert advice and radiographs.




Copyright image Copyright 2006 Nicholas Joseph Jr.




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