Upper Cervical Spine Biomechanics

Lateral Flexion (Sidebending)
 While both the atlanto-occipital and atlanto-axial joints are capable of sidebending, the greatest percentage of sidebending occurs between C0 and C1(approximately +8 degrees). Sidebending between the atlas and the axis is limited predominately by the orientation and shape of the atlantoaxial joint.

The occipital condyles are convex from front to back, and from side to side. The superior facets on the atlas are concave from the front to the back and from side to side. During sidebending of the occiput on the atlas, the occipital condyles slide on the superior articular surfaces of the atlas.
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