Adjective
atlantoaxial (not comparable)
(anatomy) Of or pertaining to the articulation of the atlas with the axis.
The upper and lower borders respectively give attachment to the anterior atlantooccipital membrane and the anterior atlantoaxial ligament ; the former connects it with the occipital bone above, and the latter with the axis below. Source: Internet
Instability of the atlantoaxial joint occurs in about 20% and may lead to spinal cord injury in 1–2%. Source: Internet