[Different images of the atlanto-axial joint based on lateral flexion].
If lateral flexion results in narrowing of one of the two atlas/dens axis articulations, then this is exclusively due to a (facultative) rotation of the atlas. In this case the massa lateralis atlantis of that side displays the usual pattern associated with rotation. Narrowing of the articular cavity is entirely due to projection and definitely not pathological. Rotation of the dens axis, being obligatory in lateral flexion, does not affect the width of the articular cavities of the atlas/dens axis articulations. Both facts can be verified without leaving any doubt, by x-ray film. Ventral or dorsal "tipping" of the dens axis or lateral "tipping" of the atlas is anatomically impossible. In our daily routine diagnosis of lateral flexion x-ray films we never found any sign pointing to such movement.
D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging* / Q000502:physiology; D007839:Functional Laterality; D006801:Humans; D009068:Movement; D011859:Radiography
Die seitendifferente Darstellung der Atlas-Axisgelenke bei der Lateralflexion.