11/13/24, 7\:33 PM Guide | Lumbar x-ray interpretation

Lumbar x-ray interpretation

Table of contents

Introduction

Lumbar spine X-rays are one of the most commonly requested radiographic investigations of the spine, however, it should be
noted that projectional radiography has limitations and other imaging modalities such as MRI and CT should be considered if
further evaluation is required.
A lumbar spine X-ray is a picture of the vertebrae in the lower part of the spine. This area includes the lumbar region and the
sacrum. It is important to remember that lumbar spine X-rays involve a signi
rays). The relevant literature suggests that lumbar spine X-rays are not routinely indicated for uncomplicated back pain which
resolves in about 90% of cases within 2 months, regardless of treatment.
Indications for a lumbar spine X-ray
Appropriate clinical indications for lumbar spine X-ray include\:
1
Signi
Age less than 20 or greater than 50
Past medical history of malignancy, ankylosing spondylitis or osteoporosis
Chronic corticosteroid use (increased risk of fracture)
An episode of back pain ongoing for 6 weeks or longer without improvement

Con

Begin by con
Patient details (name, date of birth, unique identi
Date and time the radiograph was taken
If previous radiographs are available, these should also be reviewed to provide a point of reference.

Acquire all necessary views

There are two standard projections produced when a lumbar spinal X-ray is performed\:
Lateral
Anterior-posterior (AP)/posterior-anterior (PA)
In the case of trauma, additional views can be sought including oblique and horizontal beam lateral views.

Views and adequacy

Lateral view

In a lateral view, the entire lumbar spine should be visible from T12-S1.
Lateral views are particularly useful for identifying fractures. Each vertebra (highlighted in yellow) should be examined looking
for a loss of height which could indicate a compression fracture commonly associated with osteoporosis (see fractures section
below).
Compression fractures are often seen in the upper lumbar or lower thoracic vertebrae.
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Figure 1. Lateral projection of a normal lumbar spine highlighting the vertebrae in yellow [2]

Anterior-posterior (AP)/posterior-anterior (PA)

In an AP/PA view, the entire lumbar spine should be visible from T12 superiorly and the sacrum inferiorly.
The spinous processes (red) should be central and there should be equal distance between transverse processes (green).
Transverse processes are often obscured by gas from the abdomen.
Spinal imaging should be taken erect in the non-trauma setting to give a functional overview of the lumbar spine. Patients with
a suspected spinal injury must remain immobilised in the supine position.
Figure 2. AP projection of a normal lumbar spine highlighting the spinous processes (red) and transverse processes (green) [2]
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Alignment

There are multiple lines that should be assessed across each of the two typical radiographic views of the lumbar spine (AP/PA
& lateral). These lines should run uninterrupted in healthy individuals.
On the AP/PA view check that the vertebral bodies and spinous processes are aligned.
On the lateral view, check the alignment of the vertebral bodies.
Disruption of any of these lines may indicate an underlying fracture.
Figure 3A. AP and lateral projections showing adequate alignment with yellow (spinous processes) and white (vertebral bodies) [2]

Interpretation

A structured approach to lumbar spine X-ray interpretation is essential.
Step 1
Assess alignment of the vertebral bodies and spinous processes including the lines discussed above and the distance
between spinous processes.
Step 2
Inspect for loss of vertebral height\:
The height of vertebral bodies should be equal in healthy individuals
Loss of vertebral height is suggestive of a fracture
Step 3
Inspect the vertebral spaces\:
In healthy individuals, the disc height should gradually increase from superior to inferior
Note\: the L5/S1 space is normally slightly narrower than L4/L5
Step 4
Inspect the vertebral endplates\: the continuity of superior and inferior endplates should remain uninterrupted.
Step 5
Trace the posterior elements including\:
Pedicles
Laminae
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Spinous processes
Ensure the vertebral and spinous processes are intact.

Pathology

Fractures

When describing and diagnosing spinal fractures, Radiologists divide the spinal column into 3 sections known as the ‘Three
Column model’
. This states that if any 2 columns are injured then the injury is 'unstable'
. If spinal instability is suspected further
imaging with CT or MRI should be considered.
Anterior column
Involves the anterior two-thirds of the vertebral body/intervertebral disc and the anterior longitudinal ligament.
Middle column
Involves the posterior aspect of the vertebral body/intervertebral disc and the posterior longitudinal ligament.
Posterior column
Involves the posterior elements including the lamina, facet joints, spinous processes, and the associated ligaments.
Figure 4. Schematic representation of the ‘Three Column Model’ [3]
Anterior column - anterior compression fracture
An anterior compression fracture is a fracture in which the front part of the vertebral body is crushed, resulting in a wedge
shape.
Anterior compression fractures are the most common type of lumbar spine fracture.
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Figure 5A. AP & Lateral projection depicting loss of vertebral height in keeping with a vertebral compression fracture. [2]
Middle column-
'burst fracture'
A burst fracture occurs when the vertebral body is crushed in all directions simultaneously (e.g. sudden axial loading force).
This type of fracture can result in bone fragments being projected outwards anteriorly into the spinal canal causing secondary
spinal cord injury.
A burst fracture involves two columns and is therefore typically considered to be unstable.
Figure 6. Lateral projection depicting burst fracture evident from multiple fragments of the vertebral body. [2]
Posterior column -
Flexion-distraction fractures (a.k.a. chance fractures) occur when any part of the spinal column breaks away from another
part. This type of fracture is often caused by sudden severe compression or rotation of the spine (e.g. use of a lap-only seat
belt during a deceleration injury, resulting in forceful forward
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The result is a fracture of the vertebral body with associated transverse/horizontal fractures of the posterior elements. This
type of fracture is unstable and carries a high risk of spinal cord injury.
Figure 7. Lateral projection depicting a chance fracture evident from the increased distance between the spinous processes [2]

Spondylosis

Spondylosis involves degeneration of the interverbal disc leading to disc space narrowing, endplate sclerosis and
osteophyte formation.
In some cases, osteophytes can cause neural impingement.

Spondylolysis

Spondylolysis occurs when a fracture (acute or chronic) extends from the inferior facet across the pars interarticularis (area
of the lamina that lies within the facets), to the superior facet.
This defect can in some cases be bilateral and lead to spondylolisthesis (see below). Spondylolysis is often best identi
an oblique radiograph, appearing (with the eye of faith) to represent a "Scotty dog"\:
4
Nose\: transverse process
Eye\: pedicle
Ear\: superior facet
Front leg\: inferior facet
Neck\: pars interarticularis
Collar across the neck\: fracture
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Figure 8. Oblique projection highlighting the ‘Scotty dog’ appearance of the lumbar spine [2]

Spondylolisthesis

Spondylolisthesis occurs when one vertebra is displaced forward upon another.
This can occur secondary to trauma or as a result of degenerative disease such as osteoarthritis. If severe it may lead to
foraminal stenosis, causing nerve root impingement.
Figure 9. Spondylolisthesis [5]

Vertebral bone lesions

Vertebral bone lesions can often be asymptomatic in patients and thus are often identi
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These lesions typically become symptomatic when they present as a pathological fracture with or without neurological
de
Di
6
Prostate cancer metastases
Breast cancer metastases
Thyroid cancer metastases
Renal cell carcinoma metastases
Lung cancer metastases
Multiple myeloma
Figure 10. Lateral projection displaying lytic lesions (arrows) in keeping with vertebral metastases [2]

Summary

When interpreting a lumbar spine X-ray, remember the following key points\:
Begin by con
Compare to previous X-rays where possible to provide additional context.
Assess alignment of the vertebral bodies and spinous processes carefully for inconsistencies indicative of underlying
pathology (e.g. fracture)
Inspect for loss of vertebral height which may be indicative of a vertebral fracture.
Inspect the vertebral spaces\: in healthy individuals, the disc height should gradually increase from superior to inferior.
Inspect the vertebral endplates\: the continuity of superior and inferior endplates should remain uninterrupted.
Trace the posterior elements including pedicles, laminae and spinous processes.
Inspect for signs of fracture and determine how many columns of the 'Three Column Model' are a
fracture stability.
Inspect for other important pathologies such as spondylosis, spondylolysis, spondylolisthesis and vertebral body lesions.
Projectional radiography has limitations and other imaging modalities such as MRI and CT should be considered if further
evaluation is required.
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