Introduction to Trauma X-ray

Fracture mimics

There are numerous normal anatomical features which may mimic fractures. Careful correlation of X-ray findings with clinical features are often useful to eliminate significant injury.

Some fracture mimics have characteristic features. Here are some examples.

Unfused growth plate

To the uninitiated eye the growth plate in a young patient with an unfused skeleton can mimic a fracture.

Key points

  • There are many normal features which can mimic fractures
  • Genuine fractures are often accompanied by soft tissue swelling
  • Correlation with clinical findings is essential
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Fracture mimic example - Growth plates

  • Oblique distal clavicle shaft fracture with inferior displacement
  • Widening of the acromioclavicular joint (arrowheads) indicating dislocation
  • Lines passing through the acromion and proximal humerus are growth plates - not fractures
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Unfused apophysis

The apophysis of the 5th metatarsal base is often mistaken for a fracture. Here the normal apophysis is orientated nearly longitudinally to the bone. A fracture at this site will typically be perpendicular to the length of the bone shaft.

Another clue is that the bones of an aphophysis will have a rounded and corticated edge. The edge of a fracture will be angulated with no cortication.

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Unfused apophysis example - 5th metatarsal

  • The normal apophysis runs lengthways along the bone
  • The fracture runs across the bone
  • Note the corticated and rounded edge of the apophysis compared with the sharp and non-corticated edge of the fracture fragment

Accessory ossicles

Accessory ossicles (small bones) are considered normal, but are not present in all individuals. They should not be mistaken for fractures. The best clue is that they have a dense fully corticated edge, whereas the edge of a fracture will not be corticated.

It should be remembered that although usually innocent, accessory ossicles and their surrounding soft tissues can be injured, and become symptomatic.

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Accessory ossicle example - Foot

  • This patient has an extra bone adjacent to the navicular
  • This bone is normal - note the corticated edge

Vascular/nutrient lines

Bones are highly vascular structures that are penetrated by nutrient vessels. These appear as low density black lines which often mimic fractures. Characteristically they pass obliquely through the cortex and may have a visible corticated edge. They are not associated with loss of alignment of bone as seen in genuine fractures.

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Vascular lines example - Femur

  • A well-defined lucent line passes lengthways through the bone
  • This vascular line passes obliquely through the cortex (lateral image)
  • A dense (white) corticated edge is a reassuring sign

Harris lines

You may see thin sclerotic lines passing transversely across the shaft of long bones. Although it is important not to overlook a genuine impacted fracture, these commonly seen lines are not pathological, and are considered developmental.

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Harris lines example - Tibia and fibula

  • Transverse fracture (#) of mid tibial shaft with minor displacement
  • White lines at the fracture site indicate bone overlapping or impaction
  • Multiple thin sclerotic lines pass across the tibia and fibula - these are 'Harris lines'
  • Harris lines are more evident in this patient who has reduced bone density elsewhere due to osteoporosis

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