Peg and lateral mass C1 fractures

Case contributed by Dr Craig Hacking



Patient Data

Age: 25 years
Gender: Male

There is a slightly posteriorly displaced transverse type III fracture of the odontoid process of C2. Associated prevertebral soft tissue swelling. There is widening of the right atlanto-occipital joint and suggestion of an associated fracture of the posterior right lateral mass of C1, best appreciated on the sagittal projection. Bilateral C7 cervical ribs, with the left rib fused to the transverse process which is fractured posteriorly.

Small left apical pneumothorax.


  • Minimally displaced type III fracture of the odontoid process of C2.
  • Suggestion of an subtle right posterior C1 lateral mass fracture with widening of the right atlanto-occipital joint. MRI is recommended.
  • Fractured left C7 transverse process fused to a cervical rib.
  • Small left apical pneumothorax.

Case Discussion

Peg fractures should be graded I, II or III as the grading indicates the risk of non union and hence the need for operative management.

Always look for upper rib fractures and apical PTX on a C-spine trauma CT.

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Case information

rID: 37474
Case created: 10th Jun 2015
Last edited: 13th Sep 2017
Inclusion in quiz mode: Included

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