Lumbar Spine Radiographs

• Bones are transparent and so where bony structures overlap this complicates interpretation of plan x-rays of the lumbar spine.
  • Lateral x-rays have few superimposed structures
  • Anteroposterior views have multiple superimposed elements.
  • Interpretation is through "anatomy by expectation" - expect what should be there, and then decide if what they expect is indeed present.

Lateral Views

Lateral radiograph of the lumbar spine

• Evident: Vertebral bodies and posterior elements
• Trace the anatomy, start with L3 which is usually the least obscured then repeat with other vertebrae
  • Vertebral body: Superior, anterior, and inferior margins. L5 has a large base that flows onto the pedicle and vertebral body of L5
  • Pedicle: at the posterior margin of the vertebral body
  • Superior articular process: starts on the posterior superior corner of the pedicle, projects dorsally and cephalad, with a rounded mushroom shaped head
  • Inferior articular process: From the posterior inferior corner of the pedicle, narrow lamina projects caudally and slightly dorsally, and expands into a rounded mass.
  • Transverse process: At the junction between the pedicle and the superior articular process, elliptical shadow
  • Spinous process: profile of the blade of an axe, arises from the back of the lamina
• Interpretation of the facet joints
  • The superior articular processes cover the inferior articular processes of the vertebra above.
  • Multiple markings can appear in the facet joints, creating the illusion that the joint space projects laterally.
    • This occurs when C-shaped or J-shaped joints are viewed from the side.
    • The joint space seen is only the ventral aspect of the joint, the rest of the joint projects laterally and is covered by the superior articular process.
• Soft tissues to expect but can't see
  • Dural sac behind the vertebral bodies
  • Spinal nerves in the intervertebral foramina
  • Psoas major clamping the lumbar arteries and lumbar veins against the vertebral bodies
  • Right crus and IVC anteriorly towards the right
  • Aorta and left crus anteriorly towards the left
  • Multifidus posteriorly behind the laminae and against the spinous process, fibres passing dorsally and cephalad
  • Quadratus lumborum centrally, behind and lateral to the psoas
  • Lumbar and lower thoracic erector spinae posteriorly, lateral to the multifidus, fibres running cephalad and ventrally.

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  Lateral radiograph of L3

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  Lateral radiograph the L4-5 zygapophyseal joint

Anterior (or Posterior) View

AP radiograph of the lumbar spine

References

• Bogduk, Nikolai. Clinical and radiological anatomy of the lumbar spine. Chapter 18. Edinburgh: Elsevier/Churchill Livingstone, 2012.