Wrist PA Axial for Scaphoid is a radiography positioning projection of the Upper Extremity. Seated, hand in ulnar deviation. CR angled 10-15° toward elbow. The centering point is located scaphoid, about 3/4 inch (2 cm) distal and medial to the radial styloid, with the hand in ulnar deviation. The central ray is CR angled 10-15 degrees proximally, toward the elbow along the long axis of the forearm, centered to the scaphoid (Bontrager). Merrill's gives a Stecher variation with the CR 20 degrees toward the elbow. (Alternative, modified Stecher: hand raised 20 degrees on a sponge, wrist on the IR, CR perpendicular.). Image-quality criteria include scaphoid elongated and demonstrated without foreshortening, distal carpal row and metacarpal bases included. The SID is 40 inches (102 cm).
Anatomy demonstrated
- Scaphoid fully elongated without foreshortening.
- Scaphoid borders sharp, with adjacent carpal interspaces open.
- Distal scaphoid pole without overlap.
- Lunate, capitate, and trapezium.
- First through fifth metacarpal bases.
- Distal radius and ulna.
Patient preparation
- WARNING: if wrist trauma is possible, do not attempt this position before a routine wrist series has been completed and evaluated to rule out a distal forearm or wrist fracture (Bontrager).
- Verify patient identity using two identifiers.
- Remove watches, bracelets, and radiopaque items from the arm.
- Seat the patient at the end of the table, shoulder, elbow, and wrist in one horizontal plane.
- Extend the forearm on the IR with the hand pronated, palm down.
- Without moving the forearm, turn the hand toward the ulnar side as far as the patient can tolerate.
Position & centering point
Scaphoid, about 3/4 inch (2 cm) distal and medial to the radial styloid, with the hand in ulnar deviation.
Central ray
CR angled 10-15 degrees proximally, toward the elbow along the long axis of the forearm, centered to the scaphoid (Bontrager). Merrill's gives a Stecher variation with the CR 20 degrees toward the elbow. (Alternative, modified Stecher: hand raised 20 degrees on a sponge, wrist on the IR, CR perpendicular.)
Exposure / technique
- kVp
- N/A
- mAs
- N/A
- SID
- 40" (102 cm)
- Notes
- Tabletop technique. Angle CR proximally to elongate the scaphoid. Bontrager lists 60 to 70 kV analog and 60 ± 5 kV digital; neither book's chart prints an mAs for this projection.
Image-quality criteria
- Scaphoid elongated and demonstrated without foreshortening.
- Distal carpal row and metacarpal bases included.
- Distal radius and ulna visible, with minimal superimposition at the distal radioulnar joint.
- No motion blur; scaphoid borders sharp and distinct.
- Collimation: four sides to the carpal region (Bontrager); 2.5 inches proximal and distal to the wrist joint, 1 inch on the sides (Merrill's).
Common errors
- 1 CR not angled 10-15 degrees proximally leaves the scaphoid foreshortened.
- 2 CR angled toward the fingers: Merrill's does this only for a superoinferiorly angled fracture line.
- 3 Radial deviation instead of ulnar: it opens the ulnar side of the wrist, not the scaphoid.
- 4 CR not at the scaphoid, about 3/4 inch distal and medial to the radial styloid.
Clinical indications
- Possible scaphoid fracture. Nondisplaced fractures may need more projections or a CT scan.
- Wrist trauma with scaphoid pain.