Elbow Axiolateral, Coyle (Radial Head) is a radiography positioning projection of the Upper Extremity. Elbow flexed 90 degrees, palm flat on IR. CR angled 45 degrees toward shoulder. The centering point is located radial head, with the cr exiting at the mid-elbow. elbow flexed 90 degrees, palm flat on ir.. The central ray is cr angled 45 degrees toward the shoulder, entering at the radial head.. Image-quality criteria include radial head, neck, and tuberosity free of ulnar superimposition., open humeroradial joint space.. Standard exposure ranges from 60 to 75 kVp, 3 to 6 mAs, at an SID of 40 inches (102 cm).
Anatomy demonstrated
- Radial head free of ulnar overlap.
- Radial neck and tuberosity.
- Capitulum of the humerus.
- Open humeroradial joint.
- Distal third of the humerus.
- Proximal half of the radius and ulna.
Patient preparation
- 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 80 degrees with the palm flat against the IR.
- Adjust so humerus, elbow, and wrist sit in the same plane.
Position & centering point
Radial head, with the CR exiting at the mid-elbow. Elbow flexed 90 degrees, palm flat on IR.
Central ray
CR angled 45 degrees toward the shoulder, entering at the radial head.
Exposure / technique
- kVp
- 60–75
- mAs
- 3–6
- SID
- 40" (102 cm)
- Notes
- Useful when the patient cannot extend the elbow for a standard lateral.
Image-quality criteria
- Radial head, neck, and tuberosity free of ulnar superimposition.
- Open humeroradial joint space.
- Radial head projected proximal to the capitulum.
- Distal humerus and proximal forearm both included.
- Bone trabeculae sharp, no motion blur.
- Collimation: 3 inches proximal and distal to the joint.
Common errors / ARRT traps
- 1 CR angled less than 45 degrees leaves the radial head overlapped.
- 2 Failure to keep humerus and wrist on the same plane distorts the joint.
- 3 Pronation past flat closes the humeroradial space.
- 4 Centering off the radial head clips the proximal forearm.
Clinical indications
- Suspected radial head or neck fracture.
- Patient unable to extend the elbow for a true AP or lateral.
- Post-trauma assessment when other projections are inconclusive.
- Follow-up of radial head fixation.
Aligned to the 2025 ARRT Content Specifications.