AC Joints AP is a radiography positioning projection of the Upper Extremity. Erect, bilateral AC joints. Arms at sides, no weights. SID 72". The centering point is located midline at the level of the ac joints, with both shoulders level and equal exposure intended.. The central ray is perpendicular to the midline at the level of the ac joints.. Image-quality criteria include both ac joints visualized on one image for side-by-side comparison., ac joint space clearly demonstrated without superimposition.. Standard exposure ranges from 65 to 75 kVp, 5 to 8 mAs, at an SID of 72 inches (183 cm).
Anatomy demonstrated
- Bilateral acromioclavicular joints.
- Distal third of both clavicles.
- Lateral aspects of both scapulae.
- Coracoid processes bilaterally.
- Proximal humeral heads.
- Medial clavicles and sternoclavicular joints.
Patient preparation
- Verify patient identity using two identifiers.
- Remove watches, bracelets, and radiopaque items from both arms.
- Position patient erect with the back against the IR.
- Place arms at sides with palms facing forward.
- Keep shoulders level and relaxed throughout the exposure.
Position & centering point
Midline at the level of the AC joints, with both shoulders level and equal exposure intended.
Central ray
Perpendicular to the midline at the level of the AC joints.
Exposure / technique
- kVp
- 65–75
- mAs
- 5–8
- SID
- 72" (183 cm)
- Notes
- Upright bilateral technique without weights; the weighted comparison is a separate projection. SID 72" for bilateral comparison.
Image-quality criteria
- Both AC joints visualized on one image for side-by-side comparison.
- AC joint space clearly demonstrated without superimposition.
- Distal clavicles and lateral scapulae all included.
- Clavicles in a horizontal plane, symmetric and level.
- No rotation; both shoulders equidistant from midline.
- Collimation: 1 inch above and below AC joints.
Common errors / ARRT traps
- 1 Unequal weight distribution tilts one shoulder higher.
- 2 Patient rotation makes one AC joint appear higher.
- 3 Insufficient distance between clavicles limits separation visibility.
- 4 Off-centered CR misses one AC joint on the film.
- 5 Inadequate collimation includes unnecessary shoulder anatomy.
Clinical indications
- Acromioclavicular joint separation or dislocation.
- Distal clavicle fracture evaluation.
- Osteoarthritis or degenerative changes at AC joint.
- Post-operative AC joint fixation assessment.
Aligned to the current ARRT Radiography Content Specifications.