Normal range of atlanto-denal interval

The roentgenologic diagnosis of lateral subluxation of the atlanto-axial joint is very difficult because theonly presentation is increase of the atlanto-dental interval. This study was carried out with 70 volunteers rornormal value of atlanto-dental interval. we measured these intervals from lateral roentgenograms of cervical spinein neutral flexion, and extension of the neck. The results were as follows: 1. The mean value of atlnato-dentalinteral in all subjects was 1.54+-0.52mm in neutral, 1.59+-0.62mm in flexion, and 1.46+-0.48 mm in extensionposition. 2. After thirty years of age the atlnato-dental interval was getting narrower according to aging. 3. Inneutral and flexion positions there is no difference in atlanto-dental intervals, but in extension position it wassignificantly narrowed.