Unfused spinous process

Unfused spinous process, which is really failure of fusion of the neural arch, is a relatively common anatomical variant and is part of the spectrum of spina bifida occulta

This should be differentiated from accessory ossicles of the spinous process, which appear after non-fusion of the secondary ossification centre (or centres in bifid spinous processes). These appear as a well-corticated fragment adjacent to the tip of the spinous process with a vertical or near-vertical lucency. 

The importance lies in patients with potentially traumatic spinal injuries, in which it is important to identify this variant and avoid potential pitfall of diagnosing a fracture. A well-defined cortical margin is a helpful clue.

Differential diagnosis

  • spinous process accessory ossicles
  • spinous process fracture

Spinal anatomy
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Article Information

rID: 2239
Section: Anatomy
Tags: cases, variant
Synonyms or Alternate Spellings:

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