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Applied Skeletal Imaging Diagnostic Radiography Biology Essay

This essay will describe two types of spinal fractures .The essay is divided into four main sections. It will consider definitions of burst fracture and outline the mechanisms of injury for this fracture. It will then go on to describe chance fracture and outline the mechanisms of injury for this fracture. The third part will explain appropriate imaging regime from initial diagnosis through to discharge and specific projections, modalities, technical features and protocols. Finally some conclusions will summarise the main ideas.

According to Denis classification the spine is divided in three columns which are:

Anterior column: this involves the anterior third of the vertebral body and anterior longitudinal ligament.

Middle column: this is the posterior third of the posterior longitudinal ligament, the vertebral body, annulus and discs.

Posterior column: this includes the vertebral arches, facet joints, spinous process and transverse process (Imhof and Halpern2007).

Burst fracture:

Burst fracture is fracture of the anterior and middle columns of the spine. This fracture is a result of axial loading of the spine, from a heavy object falling on the head or a fall from a height landing on the heels. Burst fractures are caused by severe trauma such as car accident. It is localized mostly in the cervical and thoracolumbar region. Burst fractures might result from flexion injuries. In less severe cases may only involve the anterior column. So In this case the vertebral body is split vertically and fragments of bone may be extruded towards the back into the spinal canal, which may put its contents at risk and cause spinal cord injury. Progressive kyphosis with likely neurologic sequelae due to failure to diagnose a posterior ligamentous injury is complication of burst fracture (Elstrom et al 2006).

The diagnosis of burst fracture is made by X-ray of thoracolumbar, CT scan and MRI. The lateral radiograph indicates compression of the anterior and middle columns, with retropulsion of the middle column posterior into the spinal canal. An axial CT or MRI examination is to document the amount of middle column retropulsion. It is difficult to identify posterior ligamentous injuries with a burst fracture because voluntary flexion extension views are accessible (Elstrom et al 2006).

Chance fracture:

This fracture is flexion- distraction injury of the lumbar spine. This is when there is an acute, severe forward flexion of the spine across a restrictive tool, such as seat belt, through rapid deceleration. Chance fracture was first described by Chance in 1948. Because of the frequency of its occurrence in motor vehicle accidents, it is often called a “seat belt” fracture. The spine above the restraining device is pushed forward and distracted from the lower, fixed portion of the spine.

The flexion- distraction mechanism of injury results in a fracture through the midportion of the L1 vertebral body with addition through the pedicle and lamina. A chance fracture generally involves anterior, middle and posterior column injuries with a horizontal direction of the fracture. These fractures most commonly occur at the level of T12, L1 or L2. These fractures are associated with intraabdominal injuries such as duodenum, the colon and the pancreas; therefore these are unstable injuries that usually do not present with a neurologic deficit. (Bangash et al 2007).The study of 53 patients from the University of Maryland Shock Trauma Centre and analysing their imaging indicates that 40% of patients experienced intraabdominal injury which bowel and mesentery were mostly involved. And also in their study 21 patients had fracture of L1.

TABLE 1: Distribution of Chance-Type Fractures

Injury Level

No.

%

T4

1

1.8

T6

1

1.8

T7

1

1.8

T9

1

1.8

T11

2

3.6

T12

14

25.5

L1

21

38.2

L2

8

14.5

L3

1

1.8

L4

3

5.5

L5

2

3.6

Total

55

100

(Bernstein et al 2006)

There are two types of fractures:

Bony chance: Bony injuries could heel with immobilization, casting or bracing.

Ligamentous chance: With ligamentous chance injury, the soft tissue and ligaments do not heel and requires surgery (radiology 2011).

Diagnosis:

Plain X-ray of thoracolumbar is essential to the diagnosis of flexion-distraction injury. The positions used are AP and cross table Lateral view of thoracolumbar spine. Lateral radiograph of thoracolumbar is the best view to see the chance fracture. Because this view demonstrate Horizontal disruption through the spinous process, laminae, transverse process, pedicles and the vertebral body . Also this view indicates widening of the posterior column either inside or between the bony elements and localised kyphosis.

Anteroposterior view will show an increased distance of interspinous and a schism in the transverse process. This view also indicates the ligamentous posterior column injury, fracture through the spinous process lamina, or splayed posterior elements. In case of sustained forces ligamentous flexion-distraction injuries may progress to unilateral or bilateral facet subluxation or dislocation. On the lateral radiograph unilateral dislocation is characterised by anterior displacement of the superior vertebra on the inferior by 25%.In displacement of 50% or greater; a bilateral facet dislocation is possible.

Cross-table lateral radiograph of lumbar spine shows fanning of spinous processes (double-headed arrow) and fracture extending through pedicle (between arrowheads) and into L2 vertebral body (single-headed arrow) (WATURA et al 2004).

(Bernstein et al 2006)

Anteroposterior radiograph of lumbar spine: A corresponding line diagram show horizontal fracture line through L2 vertebral body across both pedicles and transverse processes. "Empty body" sign is present secondary to displaced L1 and L2 spinous processes.

If nothing visible is seen on X-ray and it is only ligamentous injury, CT scan may give more details where doubt exists. CT with sagital and coronal reconstruction is required because, routine axial CT scans of the spine often miss these fractures, and also the image cuts are parallel to the level of the injury (Wolfson et al 2009 and Elstrom et al 2006).

In the study of University of Maryland Shock Trauma Centre in transaxial CT images of the thoracolumbar spine, dissolving pedicle sign and naked- facet sign was displayed. Protocols for Scanning of thoracic and lumbar spine were sagital and coronal plane, 300 mAs and 140 Kv, 3mm width, 3D and coronal MPRs reconstruction type and 3mm increment (Mark et al 2005).

Coronal CT reformation confirms distraction of left facets (arrow) and fracture of right (arrowhead).

Sagittal CT reformation depicts horizontal L2 Chance fracture through left pedicle and into vertebral body (arrow).

A-C, Three serial transaxial CT images of lumbar spine reveal progressive loss of definition of L2 left pedicle (arrow, B and C). Note right transverse process fracture (arrowhead, B). D, Sagittal CT reformation depicts horizontal L2 Chance fracture through left pedicle and into vertebral body (arrow). (Bernstein et al 2006)

MSCT might reveal further fractures and CT abdomen can demonstrate these injuries. All examinations will be performed using IV and oral contrast media. Morbidity and mortality from bowel injury increases if surgical intervention is delayed, especially for duodenal injury. The CT finding of duodenal injury may be subtle with simply small extraluminal gas bubbles, or minimal duodenal fold thickening. Small bowel injury generally occurs at points of fixation such as the ligament of Treitz or the ilio-caecal valve. Only the most minor small bowel or mesenteric injury can be treated with non-operative management. Sign on CT include wall thickening (due to hematoma), intra-peritoneal air, extravasation of oral contrast and sentinel clot adjacent to bowel. Intra-peritoneal air can be present in the absence of hollow viscus injury due to pneumothorax (via the diaphragm) or subcutaneous dissection from the chest (Hopkins et al 2008 and Novelline et al 1999).

Below is a review of literature for abdominal injury chance fractures and associated intraabdominal injuries.

Study

Authors [reference no.]

Year of Publication

No. of Patients

No. (%) of Spinal Fractures

Type of Fracture

Comments

Appleby and Nagy

1989

36

7 (19)

Not specified

All lumbar spine fractures included

Rutledge et al.

1991

531

27 (5)

Not specified

All lumbar spine fractures included

Beaunoyer et al.

2001

18

13

chance

Paediatric

Inaba et al

2001

5

3

chance

(Bernstein et al 2006)

For patients with ongoing neurologic deficit MRI is essential to evaluation of the soft tissue component of spinal cord injury. Compare with CT, MRI has enabled the focus of spinal injury to shift from bony structures to the spinal cord itself. Thecal sac and spinal cord impingement are easily identified. Up to 40% of patients who present with acute spinal injury have evidence of disk herniation. Other sequelae of spinal injury such as epidural hematoma, spinal cord edema, spinal cord hematoma, ligamentous disruption and vascular injury, as well as complications such as syringomyelia and myelomalacia, can be recognized by MRI.

The first symptom of injury to the spinal cord is a sign of intramedullary swelling and edema. These symptoms can be seen with increased cord calibre on T1-weightd images and increased cord signal on T2 weighted images on MRI examination. The length and extent of spinal cord edema is relative to neurologic deficit and prognosis. Second symptoms are intramedullary and extramedullary hemorrhage due to injury to the spinal cord (Jallo & Vaccaro 2008).

(Bernstein et al 2006)

Low-signal fracture line seen centrally in posterior vertebral body (arrow) with surrounding edema represents MRI sandwich sign.

There are two options of treatment for chance fracture. For a patient with bony fracture, medical therapy is required by placing the patient on Risser table with hyperextension in the junction of thoracolumbar and a fiberglass or plaster cast and thoracolumbosacral orthosis used for 2-3 months. A follow up erect lateral radiograph will be performed after this period of time to consider any remaining abnormality. The second option is for a patient with ligamentous injury. When immobilisation is unworkable in case of an obese patient or polytrauma, surgical therapy is required. The need to rebuild the posterior tension band with a hook-pedicle, screw-rod, and rod hook or pedicle screw-construct during surgery depends on patients’ anatomical body. Same procedures are used for ligamentous injuries. If operative intervention is selected; an axial CT scan detailing the pedicle structure is useful in selecting the suitable fixation device. MRI is also useful if a neurologic injury is present.

Arthrodesis generally is complete by 6 months. Follow-up erect lateral radiograph of thoracolumbar should be obtained monthly to check the healing process. Following 3 months of immobilization in a cast or TLSO, a treatment exercise program with emphasis on the extensor muscles of the thoracolumbar spine can assist the return to preinjury movement levels. The final outcome probably will not be determined for a year postinjury. In this period of time back pain is the most important compliant (Goodrich 2010).

Burst fracture is fracture of anterior and middle column and is unstable when posterior margin of the vertebra is also involved. The majority of Chance fractures usually are seen in patients wearing lap seat belts. This is a transverse fracture of thoracolumbar spine through body and pedicles; posterior elements. Intra-abdominal injuries such as duodenum and pancreas injuries are associated with chance fracture. It is unstable fracture and rarely associated with neurologic compromise except an important quantity of translation is noted on the lateral x-ray radiograph. It is common in thoracolumbar region. To diagnose fracture plain Radiographic imaging of thoracolumbar including AP and Lateral view, CT scan including MSCT, coronal, axial and sagital reconstruction and magnetic resonance imaging are essential.

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