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PEM Ortho X-ray Curriculum

Common Presentations

  • Paediatric Specific Radiological Features
    • Loss of normal C-spine curvature
      • Loss of normal lordosis until age 14 
    • Anterior vertebral wedging
    • Horizontal, flat interfacet joints
    • Ossification centres
    • Radiolucent synchondroses
    • Pseudosubluxation (FIGURE 4)
      • Anterior displacement of the vertebral bodies in the upper cervical spine of infants and young children is physiologic
      • Displacement may involve all four upper vertebral bodies, but usually occurs at the C2-C3 level
      • line of Swischuk (posterior cervical line) is drawn from the anterior aspect of the cortex of the spinous process of C1 to the same point on C3
        • If the line misses the anterior cortex of C2 by ≥ 2 mm, a true subluxation is present
x-rays showing pseudosubluxation in A and B and true subluxation of the upper C-spine in C
FIGURE 4: Pseudosubluxation (A and B) and true subluxation (C) of the upper C-spine


  • Prevertebral Soft Tissue Thickening 
    • Prevertebral soft tissue swelling or thickening resulting from edema or hematoma formation is an important ancillary finding
    • Soft-tissue thickening abnormal if:
      • ≥7 mm when above the glottis
      • ≥14 mm when below the glottis
    • Crying, neck flexion, or the expiratory phase of respiration may produce a pseudothickening in the prevertebral space
x-ray showing normal prevertebral soft tissue thickening
FIGURE 5: Normal prevertebral soft tissue thickening
  • Increased Predental Space (C1-to-Dens Distance)
    • In young children a predental distance of >5 mm is abnormal (FIGURE 6)
x-ray showing increased predental space
FIGURE 6: Predental Space