Atlas Posterior Tubercle

tuberculum posterius atlantis

The posterior tubercle of the atlas is the midline bony prominence on the posterior arch of C1, representing the vestigial spinous process. It provides attachment for the ligamentum nuchae, the rectus capitis posterior minor, and the posterior atlanto-occipital membrane. It is palpable in the midline immediately below the external occipital protuberance.

Anatomical Data

Structure & Landmarks

Articulations	No joint; muscular and ligamentum nuchae attachment
Landmarks	Midline posterior arch prominence Ligamentum nuchae attachment Rectus capitis posterior minor origin Suboccipital triangle landmark
Ossification	The posterior arch of C1 ossifies from a single posterior centre that appears at 7-9 weeks gestation and fuses with the lateral mass by age 3-4.

Clinical Relevance

Clinical Notes

The posterior atlas tubercle is palpated in suboccipital headache assessment and is a landmark for the suboccipital approach to the craniocervical junction. Atlas posterior arch fractures may extend through or adjacent to the tubercle in axial loading injuries. The vertebral artery sulcus runs lateral to the posterior tubercle on the superior surface of the posterior arch, just medial to the lateral mass. The posterior atlanto-occipital membrane attaches along the posterior arch from the posterior tubercle to the lateral masses.

Pathology

Common Injuries & Conditions

Posterior Arch Fracture of C1

Hyperextension compresses the posterior arch between the occiput and C2, causing a stable fracture of the arch.

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