AP Humerus

The AP Humerus is a comprehensive view designed to capture the entire length of the humerus, from the “ball” of the shoulder to the “hinge” of the elbow. Because this bone is long and the joints at either end are oriented differently, the challenge is ensuring both the proximal and distal ends are diagnostic in a single exposure.

The Goal

To demonstrate the entire humerus in a true anatomical position, including the shoulder and elbow joints, with the greater tubercle profiled laterally.

Patient Positioning

The Setup: Position the patient upright with their back against the bucky or supine on the table.
The Arm: Abduct the arm slightly to prevent the humerus from overlapping the ribs.
The Rotation: Externally rotate the arm until the palm is facing forward.
The Epicondyles: Crucially, the elbow epicondyles must be parallel to the IR. This ensures the humerus is in a true AP orientation.
Pro-Tip: If the patient has a suspected mid-shaft fracture, do not force rotation. In trauma cases, move the patient’s body as a unit or angle the tube to achieve the AP perspective without moving the injured limb.

Technical Factors

Central Ray (CR): Perpendicular to the IR, centered to the mid-shaft of the humerus.
SID: 40″.
Collimation: Must include the entire humerus, extending at least 1 inch (2.5 cm) past both the shoulder and elbow joints.

Image Evaluation Criteria (The “Richie” Checklist)

A professional AP Humerus must meet these benchmarks:

Joint Inclusion: Both the shoulder and elbow joints must be visible on the image. If the humerus is too long for one IR, use two overlapping images.
Proper Rotation: The greater tubercle should be seen in profile laterally.
No Motion: Look for sharp trabecular markings throughout the shaft.
Alignment: The humeral head and the distal epicondyles should be shown without excessive distortion.
Marker Placement: Place your physical R/L marker in the lateral light field, ensuring it doesn’t block any bony anatomy or soft tissue.

Why the AP Humerus Matters

This view is the primary way we assess for mid-shaft fractures, which often result from direct trauma or falls. It also allows the radiologist to check for “pathologic fractures”—breaks that happen because the bone has been weakened by an underlying condition like a cyst or tumor. Without including both joints, we might miss secondary injuries or a dislocation associated with the primary fracture.

Richie’s Pro-Tips for Humerus Imaging

Privacy & Breathing: Provide a lead shield and ensure the patient’s privacy. Have the patient hold their breath on expiration to minimize any torso movement that could blur the image.osis.

The Overlap Technique: If the patient’s arm is longer than the 14×17 IR, take one image centered high (to get the shoulder) and one centered low (to get the elbow). Make sure there is plenty of overlap in the middle so no anatomy is missed.

Physical Markers are the Standard: Only use digital markers if necessary for long bone imaging. Lead markers placed on the IR at the time of exposure are a legal requirement for orthopedic studies.