The purpose of this exhibit is: 1. Review developmental embryology, anatomy, biomechanics, measurement of the atlantodental interval in the adult and pediatric population and its main anatomical variations that can simulate solutions.2. Review imaging protocols for their evaluation according to clinical suspicion (X-ray, CT and MRI). 3. Discuss the main traumatic and non-traumatic injuries that can affect the joint, correlating their findings with imaging methods.

1. Developmental embryology (ossification nuclei). 2. Atlanto-axial joint anatomy: CT, X-ray, ligaments (MRI), craniometry (basion-dens interval, power ratio, basion-axial interval, atlantodental interval, spinolamine distance C1-C2) 3. Normal variants that mimic lesions: fusion anomalies, posterior/anterior rachischisis, persistence of the terminal ossicle (Bergman), "os odontoideum", calcification of the alar ligament. 4. Biomechanics: extension, flexion, lateral flexion, axial rotation. 5. Imaging assessment: RX, CT and MRI protocols (ligaments and spinal cord injury). 6. Differentiation of normal/positional findings from pathological alignment changes. 7. Atlas fracture (Jefferson). 8. Odontoid fracture (Anderson and D'Alonzo classification). 9. Traumatic spondylolisthesis of C2 (hangman's fracture). 10. Atlanto-axial subluxation (anteroposterior, rotational, vertical and lateral). 11. Alar ligament deformity-rupture. 12. Rupture of the transverse ligaments. 13. Rheumatoid arthritis. 14. CPPD