Elbow AP Oblique (Medial Rotation) is a radiography positioning projection of the Upper Extremity. Arm extended, whole arm internally rotated 45 degrees from true AP. The centering point is located mid-elbow joint, about 3/4 inch (2 cm) distal to the midpoint of the line between the epicondyles, with the entire arm internally rotated 45 degrees from a true AP start. The central ray is perpendicular to the mid-elbow joint. Image-quality criteria include coronoid process of the ulna in profile, free of the radial head, radial head and neck superimposed by the proximal ulna. The SID is 40 inches (102 cm).
Anatomy demonstrated
- Coronoid process of the ulna in profile.
- Trochlea of the humerus in profile.
- Medial epicondyle.
- Distal humerus.
- Proximal radius (overlapped by the ulna).
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.
- Extend the arm over the IR, palm up, in true AP first.
- Internally rotate the entire arm 45 degrees from true AP, hand pronated (palm down).
Position & centering point
Mid-elbow joint, about 3/4 inch (2 cm) distal to the midpoint of the line between the epicondyles, with the entire arm internally rotated 45 degrees from a true AP start.
Central ray
Perpendicular to the mid-elbow joint.
Exposure / technique
- kVp
- N/A
- mAs
- N/A
- SID
- 40" (102 cm)
- Notes
- Medial rotation projects the coronoid process free of the radius. If the patient cannot fully extend the elbow, Bontrager points to the Coyle axial laterals. Bontrager digital range: 65 to 75 kV. Merrill's chart has no separate row for this oblique, so no mAs is given.
Image-quality criteria
- Coronoid process of the ulna in profile, free of the radial head.
- Radial head and neck superimposed by the proximal ulna.
- Trochlea visible in profile.
- Trochlear notch partially open, with the olecranon process seated in the olecranon fossa.
- Distal humerus and proximal forearm both included.
- Collimation: 3 inches proximal and distal to the joint.
Common errors
- 1 Interepicondylar plane not about 45 degrees to the IR, so the coronoid process is not in profile.
- 2 Shoulder and elbow not on the same horizontal plane.
- 3 Rotating only the wrist instead of the whole forearm gives a partial oblique.
Clinical indications
- Suspected coronoid process fracture.
- Pathologic processes such as osteoporosis and arthritis.