Scapula AP is a radiography positioning projection of the Upper Extremity. Erect, arm abducted 90 degrees. CR perpendicular to midscapula. SID 40". The centering point is located midscapular region, about 2 inches (5 cm) inferior to the coracoid process, with the arm abducted 90 degrees to draw the scapula laterally. The central ray is perpendicular to the midscapular area. Image-quality criteria include lateral portion of the scapula clear of the ribs; the medial portion overlies them, scapular body, acromion, and inferior angle clearly seen. A sample technique is 85 kVp with DR 5.5 or CR 11 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Entire scapular body.
- Lateral and medial borders.
- Acromion process.
- Coracoid process.
- Inferior angle.
- Glenoid cavity.
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 shoulder.
- Position patient erect with the back against the IR.
- Gently abduct the arm of the affected side to 90 degrees from the body, hand supinated.
- Keep the posterior shoulder against the IR without rotating the thorax.
Position & centering point
Midscapular region, about 2 inches (5 cm) inferior to the coracoid process, with the arm abducted 90 degrees to draw the scapula laterally.
Central ray
Perpendicular to the midscapular area.
Exposure / technique
- kVp
- 85
- mAs
- DR 5.5 / CR 11
- SID
- 40" (102 cm)
- Notes
- Erect technique. Abducting the arm 90 degrees draws the scapula laterally, clearing it from the rib cage. Slow breathing technique blurs the ribs. Sample technique: DR 5.5 / CR 11 mAs at 85 kVp, 40 in SID, for an 18 cm part. Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Lateral portion of the scapula clear of the ribs; the medial portion overlies them.
- Scapular body, acromion, and inferior angle clearly seen.
- Arm abducted 90 degrees, shown by the lateral border of the scapula free of superimposition.
- Coracoid process visible projecting anteriorly.
- Scapula horizontal and not slanted.
- Collimation: closely to the scapula (Bontrager); 1.5 inches above the shoulder, 2 inches beyond its lateral aspect, 1 inch below the inferior angle (Merrill's).
Common errors
- 1 Failure to abduct the arm 90 degrees leaves the scapula over the ribs.
- 2 Superimposition of ribs obscures scapular detail.
- 3 Rotating the body toward the affected side offsets the lateral draw of the scapula and adds rib superimposition.
- 4 CR not at the midscapula, about 2 inches inferior to the coracoid process.
Clinical indications
- Scapular fracture evaluation across entire bone.
- Scapular body or spine fracture assessment.