Atlantoaxial instability eMedicine Orthopedics

Description: Atlantoaxial instability (AAI) is characterized by excessive movement at the junction between the atlas (C1) and axis (C2) due to either a bony or ligamentous abnormality. Neurologic symptoms occur when the spinal cord is involved. The causes of AAI are varied. AAI sometimes results from trauma. Other cases occur secondary to an upper respiratory infection or infection following head and neck surgery. Another cause is rheumatoid arthritis (RA), with its predilection for the upper cervical spine. In addition, congenital anomalies, syndromes, or metabolic diseases can increase the risk of AAI.
Synonyms and related keywords: AAI, atlantoaxial subluxation, AAS, rotary dislocation, rotational subluxation, spontaneous hyperemic dislocation, atlantoaxial rotary subluxation
Banit, Murrey & Darden 2005