Aims. To determine the normal values and usefulness of the C1/4 space
available for spinal cord (SAC) ratio and C1 inclination angle,
which are new radiological parameters for assessing atlantoaxial
instability in children with Down syndrome. Patients and Methods. We recruited 272 children with Down syndrome (including 14 who
underwent surgical treatment), and 141 children in the control group.
All were aged between two and 11 years. The