Atlantoaxial Instability and Ligamentous Hyperlaxity in down Syndrome

Sports practice in Down syndrome patients has been established as an important method of therapy, integration and socialization(1). However, the presence of atlantoaxial instability (AAI) in those children deserves a special concern, because it exposes their carriers to high risks of acute medullary injuries with sudden death, in case a forced cervical flexion occurs during sports activity, dislocating or sub-dislocating vertebrae and compressing spinal cord(1) . Spitzer et al.(2) published the first report on atlantoaxial instability in Down syndrome patients. Since then, many authors have reported this association at rates ranging from 9% to 40%, with only 10 to 15% of those individuals being symptomatic(1,3,4,5,6). Thus, the identification of AAI and its risk factors in those children is very important before indicating a sport practice. The odontoid hypoplasia and the degenerative changes on cervical spine have already been reported as predisposing factors; however, the generalized ligamentous hyperlaxity, which is also found in high rates in those individuals, has been considered by some authors as the major entity related to AAI. It is known that the atlantoaxial instability (AAI) is an affection characterized by the increased mobility of the joint formed by the first and second cervical vertebrae (atlantoaxial joint) due to the laxity of the alar ligament at this level(7). However, the association between alar ligamentous laxity and generalized ligamentous laxity, as well as its real meaning, remain poorly defined in literature. Based on this controversy, a transverse-sectioned study was conducted aiming to check the incidence of AAI in Down syndrome patients and its potential correlation with generalized ligamentous hyperlaxity.