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Third condyle

The third condyle, also known as condylus tertius or median occipital condyle, is a rare anatomic variant of the occipital condyles. It is a small separate ossicle at the anteromedial margin of the occipital condyle formed by the failure of the embryonic proatlas (4th occipital sclerotome) to unite with the condyle proper.

It may form a true arthrosis or pseudoarthorosis with the adjacent odontoid process of the axis or anterior arch of the atlas and has an association with an os odontoideum.

The third condyle represents a spectrum of occipital vertebrae variations and the 3 other most common variants include:

Practical points

This anatomic variant may mimic an occipital condyle fracture.

Anatomy: Spine

Article information

rID: 56027
Section: Anatomy
Synonyms or Alternate Spellings:
  • Median occipital condyle
  • Condylus tertius

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Cases and figures

  • Case 1
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