a. joint — the articulation between the first two cervical vertebrae.
a. membrane — the fibrous sheet which closes the interarcual space between the atlas and the axis.
a. subluxation — degeneration or malformation of the dens is seen mainly in toy breeds of dogs predisposing to displacement of the axis. Fracture of the dens can occur in any animal. Compression of the cervical cord is a common sequel that causes neck pain and varying degrees of spastic tetraparesis. Treatment is surgical stabilization. Also reported in Holstein cattle.