Digits 2-5 PA Oblique is a radiography positioning projection of the Upper Extremity. Seated, hand rotated 45 degrees laterally, radial side raised. The 2nd digit may instead be a 45-degree medial oblique, thumb side down. SID 40". The centering point is located PIP joint of the affected digit, rotated 45 degrees. The central ray is perpendicular to the PIP joint of the affected digit. Image-quality criteria include affected digit shown in 45-degree oblique with minimal overlap, all three phalanges and the distal metacarpal included. A sample technique is 63 kVp with DR 0.6 or CR 1.6 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Distal, middle, and proximal phalanges of digits 2-5.
- Distal portion of the adjoining metacarpal.
- DIP, PIP, and MCP joint spaces.
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 rings, bracelets, and radiopaque items from the hand.
- Seat the patient at the end of the table.
- Flex the elbow about 90 degrees with hand rotated 45 degrees.
- Raise the radial (thumb) side of the hand. Separate digits on IR.
- Support the digit on a 45-degree foam step, parallel to the IR.
Position & centering point
PIP joint of the affected digit, rotated 45 degrees.
Central ray
Perpendicular to the PIP joint of the affected digit.
Exposure / technique
- kVp
- 63
- mAs
- DR 0.6 / CR 1.6
- SID
- 40" (102 cm)
- Notes
- Tabletop technique. Radial side raised 45 degrees. Sample technique: DR 0.6 / CR 1.6 mAs at 63 kVp, 40 in SID, for a 1.5 cm part. Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Affected digit shown in 45-degree oblique with minimal overlap.
- All three phalanges and the distal metacarpal included.
- Joint spaces open and clearly visible.
- Bone trabeculae and soft tissue sharp, no motion blur.
- Collimation: 1 inch on all sides, 1 inch proximal to MCP joints.
Common errors
- 1 Rotation other than 45 degrees: a correct oblique shows concavity on the elevated side of the phalangeal bodies.
- 2 Digits flexed or overlapped obscures joint spaces.
- 3 CR not at the PIP joint of the affected digit.
Clinical indications
- Fractures and dislocations of the phalanges, distal metacarpal and associated joints (routine with the PA and lateral).
- Suspected finger joint arthritis or degenerative changes.