What is the most likely diagnosis? 
              
- 27 year-old with neck pain after fall

                
                Lateral Radiograph of Cervical Spine
              
                - Foreign Body Impaction
- Atlanto-axial Subluxation
- Lymphoma
- Paget Disease
- Atlanto-occipital Dislocation
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                  Answer:
               
              
                2. Atlanto-axial Subluxation
                 
              
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              Atlanto-axial Subluxation
                  
              
              General       Considerations
              
                - Distance  between the anterior surface of the dens and the posterior surface of the  tubercle of C1 is usually 3 mm or less in adults and 5 mm or less in children
                  - This  space is called by many names: predentate space, predental space, atlantodental  distance
- The  distance may increase slightly on flexion in children but is usually unchanged  between flexion and extension in adults
- Forward  movement of the atlas on the axis is normally restricted by the transverse  ligament