Forearm Lateral is a radiography positioning projection of the Upper Extremity. Seated, forearm lateral on IR with thumb up. SID 40". The centering point is located at the midpoint of the forearm, midway between the wrist and elbow joints, in the lateral position. The central ray is perpendicular to the IR at the midpoint of the forearm, midway between the wrist and elbow joints. Image-quality criteria include entire radius and ulna visible in true lateral position, distal radius and ulna superimposed. A sample technique is 70 kVp with DR 1.25 or CR 2.2 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Entire radius in true lateral projection.
- Entire ulna from styloid to olecranon.
- Radial tuberosity, demonstrated (Bontrager) and facing anteriorly (Merrill's).
- Proximal row of carpal bones.
- Elbow joint in true lateral position.
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.
- Seat the patient at the end of the table.
- Flex the elbow 90 degrees, forearm on the IR in lateral position with thumb up.
- Adjust table so humerus, elbow, and forearm rest in the same plane.
Position & centering point
At the midpoint of the forearm, midway between the wrist and elbow joints, in the lateral position.
Central ray
Perpendicular to the IR at the midpoint of the forearm, midway between the wrist and elbow joints.
Exposure / technique
- kVp
- 70
- mAs
- DR 1.25 / CR 2.2
- SID
- 40" (102 cm)
- Notes
- Tabletop technique. Include both wrist and elbow joints. Sample technique: DR 1.25 / CR 2.2 mAs at 70 kVp, 40 in SID, for a 7 cm part. Adjust for your equipment.
kVp and mAs are sample values. Use caution when applying them in your department.
Image-quality criteria
- Entire radius and ulna visible in true lateral position.
- Distal radius and ulna superimposed.
- Wrist and elbow joints included.
- Radial tuberosity demonstrated (Bontrager); facing anteriorly (Merrill's).
- Bone trabeculae sharp, no motion blur.
- Collimation: sides to the forearm; include at least 1 to 1 1/2 inches (3 to 4 cm) past both joints (Bontrager) or 2 inches (5 cm) (Merrill's).
Common errors
- 1 Hand and wrist not in true lateral: the head of the ulna should superimpose the radius.
- 2 Shoulder not dropped, so the upper limb is not on one horizontal plane.
- 3 Field too tight at the ends: beam divergence can cut off a joint.
Clinical indications
- Suspected radius or ulna fracture in lateral plane.
- Fractures and dislocations of the radius or ulna (routine with the AP).
- Pathologic processes such as osteomyelitis or arthritis.
- Elbow effusion or fat pad evaluation.