Humerus AP is a radiography positioning projection of the Upper Extremity. Upright, arm extended at the side with the hand supinated. SID 40". The centering point is located at the midpoint of the humerus between shoulder and elbow. The central ray is perpendicular to IR at the midpoint of the humerus. Image-quality criteria include entire humerus visible from shoulder to elbow, humeral head, shaft, and condyles all included. A sample technique is 75 kVp with DR 2.8 or CR 5.6 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Humeral head, neck, and shaft.
- Greater and lesser tuberosities.
- Medial and lateral epicondyles.
- Distal humerus.
- Shoulder articulation and glenoid fossa.
- Proximal radius and ulna.
Patient preparation
- WARNING: with possible spinal injury or severe trauma, do not attempt to move the patient; do not rotate a severely injured part or remove splints (Bontrager). Merrill's: do not attempt true AP or lateral positioning of a severely injured limb; take two projections 90 degrees apart, moving it as little as possible, and move the IR and tube if the patient cannot reach the position.
- Verify patient identity using two identifiers.
- Remove watches, bracelets, and radiopaque items from the arm.
- Do not rotate the arm if a fracture or dislocation is suspected.
- Position patient upright facing forward.
- Keep the arm extended and slightly abducted, elbow straight.
- Supinate the hand so the palm faces forward, placing the epicondyles parallel to the IR.
- Suspend respiration during the exposure.
Position & centering point
At the midpoint of the humerus between shoulder and elbow.
Central ray
Perpendicular to IR at the midpoint of the humerus.
Exposure / technique
- kVp
- 75
- mAs
- DR 2.8 / CR 5.6
- SID
- 40" (102 cm)
- Notes
- Bontrager lists a grid unless the humerus is under 10 cm thick, with 70 ± 5 kV analog and 80 ± 5 kV digital. Sample technique: DR 2.8 / CR 5.6 mAs at 75 kVp, 40 in SID, for a 12 cm part, from the Bucky/grid row of Merrill's chart. Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Entire humerus visible from shoulder to elbow.
- Humeral head, shaft, and condyles all included.
- Minimal rotation with epicondyles symmetric.
- Shoulder articulation and upper arm well visualized.
- Bone trabeculae sharp, no motion blur.
- Collimation: sides to the soft tissue borders, with the elbow joint and about 1 inch of forearm included (Bontrager); 2 inches above the shoulder and below the elbow, 1 inch on the sides (Merrill's).
Common errors
- 1 Internal rotation superimposes the greater tuberosity.
- 2 Failure to supinate fully leaves the epicondyles oblique rather than parallel to the IR.
- 3 Shoulder or elbow joint cut off: set the IR so both are equidistant from its ends.
Clinical indications
- Trauma evaluation for humeral fracture.
- Suspected proximal humerus fracture.
- Shoulder dislocation assessment.
- Post-operative follow-up of humeral fixation hardware.