AP Dens (Fuchs)

• Odontoid (dens) of axis (C2).
• Lateral masses of atlas (C1).
• C1-C2 articulation relationship.
• Axis vertebral body.
• Upper cervical vertebral alignment.

• CONTRAINDICATED in known or suspected cervical trauma: this projection requires hyperextension.
• Confirm cervical injury has been excluded before extending the head.
• Verify patient identity using two identifiers.
• Remove dentures, removable bridges, and neck metal.
• Supine on table, no rotation or tilt.
• Extend head backward gently until the mentomeatal line is near perpendicular to the IR.

1.5 inches below chin, with head extended.

Perpendicular to IR, 1.5 inches below chin.

kVp

70–80

mAs

10–15

SID

40" (102 cm)

Notes

Used as alternative when open-mouth is contraindicated.

• Odontoid process clearly visualized without tooth obscuration.
• Lateral borders of C1 symmetrically positioned.
• No head rotation or lateral flexion evident.
• Body of C2 inferior to dens shown.
• Structures sharp with no motion artifact.

1. 1 Insufficient head extension closes the odontoid view.
2. 2 Head rotation to either side tilts lateral masses off symmetry.
3. 3 CR misalignment off chin prevents clear dens visualization.
4. 4 Upper incisors may overlap odontoid if centration off.

• Non-trauma patient who cannot open the mouth sufficiently for the open-mouth projection.
• Suspected C2 odontoid pathology once cervical injury has been excluded.
• Post-operative follow-up of odontoid fusion.
• Dental appliances or anatomy obscuring the dens on the open-mouth projection.