Atlanto-occipital articulation
Updates to Article Attributes
The atlanto-occipital articulation is comprised of a pair of condyloid synovial joints that connect the occiput (C0) to the first cervical vertebra (atlas/C1).
Gross anatomy
Articulations
Each joint is comprised of two concave articular surfaces on the superior aspect of the lateral mass of atlas which articulate with a convex surface on the occipital condyle. The joint is reinforced by fibrous capsules which support each joint. The atlanta facets are tilted medially.
Attachments
-
anterior atlanto-occipital membrane:
dense, thinbroad,broaddense fibrous structure which joins the upper border of the anterior arch of the atlas (C1) to the anterior inferiorsurfacemargin of the foramen magnum; it is a continuation of the anterior longitudinal ligament and prevents excessive neck extension. Laterally it blends with the joint capsule and medially is strengthened by a strong, rounded cord which connects the basilar occipital bone to the anterior atlantal tubercle. - posterior atlanto-occipital membrane: a broad but thin fibrous membrane which attaches the upper border of the anterior surface of the posterior arch of the atlas (C1) to the posterior margin of the foramen magnum. It is continuous with the posterior atlanto-axial membrane inferiorly (part of the ligamentum flavum) and ligamentum nuchae posteriorly and lies immediately posterior to the spinal dura. Posteriorly lie the suboccipital muscles. The atlantic (V3) portion of the vertebral artery runs anteriorly to pierce the membrane and dura and become the dural (V4) portion.
- tectorial membrane: continuation of the posterior longitudinal ligament from the dens to the anterior aspect of the foramen magnum.
Innervation
The joint capsule is innervated by the C1 nerve.
Blood Supply
Anastomosis between the deep cervical, occipital and vertebral arteries.
Function
Allows for 25o of flexion/extension and around 5o of axial rotation.
Relations
posterior - vertebral artery
anterior - rectus capitis anterior
posteromedial - dorsal ramus of the first cervical nerve and rectus capitis posterior major
Variant anatomy
- Variable degree of communication between the atlanto-occipital joint and the cavity between the dens (odontoid peg) and transverse ligament of the cruciform ligament
- Third occipital condyle (condylus tertius) which may articulate with the anterior arch of the atlas, or the dens
- Paracondylar process
- Occipital condyle hypoplasia
- Division of the superior articular facet of the atlas
- Atlanto-occipital assimilation
- Arcuate foramen - foramen visualised by the atlantic portion of the vertebral artery as it courses through a calcified posterior atlanto-occipital membrane
Function
Allows for 25o of flexion/extension and around 5o of axial rotation.
Related pathology
Atlanto-occipital dissociation (AOD) represents the most common cervical spine injury following motor-vehicle accident and is usually highly unstable with significant neurological morbidity.
-<p>The <strong>atlanto-occipital articulation </strong>is comprised of a pair of <a href="/articles/condyloid-joint">condyloid synovial joints</a> that connect the <a href="/articles/occipital-bone">occiput</a> (C0) to the <a href="/articles/atlas-c1">first cervical vertebra</a> (atlas/C1).</p><h4>Gross anatomy</h4><h5>Articulations</h5><p>Each joint is comprised of two concave articular surfaces on the superior aspect of the lateral mass of atlas which articulate with a convex surface on the occipital condyle. The joint is reinforced by fibrous capsules which support each joint.</p><h5>Attachments</h5><ul>- +<p>The <strong>atlanto-occipital articulation </strong>is comprised of a pair of <a href="/articles/condyloid-joint">condyloid synovial joints</a> that connect the <a href="/articles/occipital-bone">occiput</a> (C0) to the <a href="/articles/atlas-c1">first cervical vertebra</a> (atlas/C1).</p><h4>Gross anatomy</h4><h5>Articulations</h5><p>Each joint is comprised of two concave articular surfaces on the superior aspect of the lateral mass of atlas which articulate with a convex surface on the occipital condyle. The joint is reinforced by fibrous capsules which support each joint. The atlanta facets are tilted medially. </p><h5>Attachments</h5><ul>
-<a href="/articles/anterior-atlanto-occipital-membrane-1">anterior atlanto-occipital membrane</a>: dense, thin, broad fibrous structure which joins the upper border of the anterior arch of the <a href="/articles/atlas-c1">atlas (C1)</a> to the anterior inferior surface of the <a href="/articles/foramen-magnum">foramen magnum</a>; it is a continuation of the <a href="/articles/anterior-longitudinal-ligament">anterior longitudinal ligament</a> and prevents excessive neck extension</li>- +<a href="/articles/anterior-atlanto-occipital-membrane-1">anterior atlanto-occipital membrane</a>: broad, dense fibrous structure which joins the upper border of the anterior arch of the <a href="/articles/atlas-c1">atlas (C1)</a> to the anterior inferior margin of the <a href="/articles/foramen-magnum">foramen magnum</a>; it is a continuation of the <a href="/articles/anterior-longitudinal-ligament">anterior longitudinal ligament</a> and prevents excessive neck extension. Laterally it blends with the joint capsule and medially is strengthened by a strong, rounded cord which connects the basilar occipital bone to the anterior atlantal tubercle.</li>
-<a href="/articles/posterior-atlanto-occipital-membrane-1">posterior atlanto-occipital membrane</a>: a broad but thin fibrous membrane which attaches the upper border of the anterior surface of the posterior arch of the <a href="/articles/atlas-c1">atlas (C1)</a> to the posterior margin of the <a href="/articles/foramen-magnum">foramen magnum</a>. It is continuous with the posterior atlanto-axial membrane inferiorly (part of the <a title="Ligamentum flavum" href="/articles/ligamentum-flavum">ligamentum </a><a title="Ligamentum flavum" href="/articles/ligamentum-flavum">flav</a><a title="Ligamentum flavum" href="/articles/ligamentum-flavum">um</a>) and <a href="/articles/ligamentum-nuchae">ligamentum nuchae</a> posteriorly and lies immediately posterior to the <a title="Spinal dura mater" href="/articles/spinal-dura-mater">spinal dura</a>. Posteriorly lie the <a href="/articles/suboccipital-muscle-group">suboccipital muscles</a>. The atlantic (V3) portion of the <a href="/articles/vertebral-artery">vertebral artery</a> runs anteriorly to pierce the membrane and dura and become the dural (V4) portion.</li>-</ul><h5>Innervation</h5><p>The joint capsule is innervated by the C1 nerve.</p><h4>Variant anatomy</h4><ul>-<li>Variable degree of communication between the atlanto-occipital joint and the cavity between the dens (odontoid peg) and transverse ligament of the <a title="Cruciform ligament" href="/articles/cruciate-ligament-of-the-atlas">cruciform ligament</a>- +<a href="/articles/posterior-atlanto-occipital-membrane-1">posterior atlanto-occipital membrane</a>: a broad but thin fibrous membrane which attaches the upper border of the anterior surface of the posterior arch of the <a href="/articles/atlas-c1">atlas (C1)</a> to the posterior margin of the <a href="/articles/foramen-magnum">foramen magnum</a>. It is continuous with the posterior atlanto-axial membrane inferiorly (part of the <a href="/articles/ligamentum-flavum">ligamentum </a><a href="/articles/ligamentum-flavum">flav</a><a href="/articles/ligamentum-flavum">um</a>) and <a href="/articles/ligamentum-nuchae">ligamentum nuchae</a> posteriorly and lies immediately posterior to the <a href="/articles/spinal-dura-mater">spinal dura</a>. Posteriorly lie the <a href="/articles/suboccipital-muscle-group">suboccipital muscles</a>. The atlantic (V3) portion of the <a href="/articles/vertebral-artery">vertebral artery</a> runs anteriorly to pierce the membrane and dura and become the dural (V4) portion.</li>
- +<li>tectorial membrane: continuation of the posterior longitudinal ligament from the dens to the anterior aspect of the foramen magnum. </li>
- +</ul><h4>Innervation</h4><p>The joint capsule is innervated by the C1 nerve.</p><h4>Blood Supply</h4><p>Anastomosis between the deep cervical, occipital and vertebral arteries.</p><h4>Function</h4><p>Allows for 25<sup>o</sup> of flexion/extension and around 5<sup>o</sup> of axial rotation.</p><h4>Relations</h4><ul>
- +<li><p>posterior - vertebral artery</p></li>
- +<li><p>anterior - rectus capitis anterior</p></li>
- +<li><p>posteromedial - dorsal ramus of the first cervical nerve and rectus capitis posterior major </p></li>
- +</ul><h4>Variant anatomy</h4><ul>
- +<li>Variable degree of communication between the atlanto-occipital joint and the cavity between the dens (odontoid peg) and transverse ligament of the <a href="/articles/cruciate-ligament-of-the-atlas">cruciform ligament</a>
-</ul><h4>Function</h4><p>Allows for 25<sup>o</sup> of flexion/extension and around 5<sup>o</sup> of axial rotation.</p><h4>Related pathology</h4><p><a href="/articles/atlanto-occipital-dissociation-injuries">Atlanto-occipital dissociation (AOD)</a> represents the most common cervical spine injury following motor-vehicle accident and is usually highly unstable with significant neurological morbidity.</p>- +<li>Atlanto-occipital assimilation</li>
- +<li>Arcuate foramen - foramen visualised by the atlantic portion of the vertebral artery as it courses through a calcified posterior atlanto-occipital membrane </li>
- +</ul><h4>Related pathology</h4><p><a href="/articles/atlanto-occipital-dissociation-injuries">Atlanto-occipital dissociation (AOD)</a> represents the most common cervical spine injury following motor-vehicle accident and is usually highly unstable with significant neurological morbidity.</p>