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The distance between the atlas and the occipital condyles, the atlanto-occipital interval (AOI), should measure less than 4 mm, and is better assessed on coronal images. [ 4 ] The Powers ratio was formerly used, which was the tip of the basion to the spinolaminar line, divided by the distance from the tip of the opisthion to the midpoint of the ...
The atlanto-occipital joint may be dislocated, especially from violent accidents such as traffic collisions. [1] This may be diagnosed using CT scans or magnetic resonance imaging of the head and neck. [1] Surgery may be used to fix the joint and any associated bone fractures. [1] Neck movement may be reduced long after this injury. [1]
A widening of the atlanto-axial joint, as measured between the posterior surface of the anterior arch of atlas and the front of the odontoid process, indicates an injury to the transverse atlantal ligament. [6] Normally, this atlanto-dental distance is less than 2 mm, sometimes a maximum of 3 mm is accepted in men and 2.5 mm in women. [6]
The atlanto-occipital joint allows the head to nod up and down on the vertebral column. The dens acts as a pivot that allows the atlas and attached head to rotate on the axis, side to side. The atlas's chief peculiarity is that it has no body, [ 3 ] which has fused with the next vertebra . [ 4 ]
The occipital condyles are undersurface protuberances of the occipital bone in vertebrates, which function in articulation with the superior facets of the atlas vertebra.. The condyles are oval or reniform (kidney-shaped) in shape, and their anterior extremities, directed forward and medialward, are closer together than their posterior, and encroach on the basilar portion of the bone; the ...
The atlanto-occipital joint allows the skull to move up and down, while the atlanto-axial joint allows the upper neck to twist left and right. The axis also sits upon the first intervertebral disc of the spinal column.
This movement between the atlas and occipital bone is often referred to as the "yes joint", owing to its nature of being able to move the head in an up-and-down fashion. The movement of shaking or rotating the head left and right happens almost entirely at the joint between the atlas and the axis, the atlanto-axial joint. A small amount of ...
At either lateral extremity, [3]: 426, 430 the membrane is pierced by the vertebral artery [3]: 426, 430, 452 and cervical spinal nerve C1. [3]: 426 The free border of the membrane arches over the artery and nerve, [5] and is sometimes ossified (converting the passage for the vertebral artery into a foramen).