Instability of the upper cervical spine.
D001172:Arthritis, Rheumatoid; D002574:Cervical Vertebrae / Q000033:anatomy & histology*; D006801:Humans; D004204:Joint Dislocations / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery; D007596:Joints; D008722:Methods; D011859:Radiography; D013123:Spinal Fusion