Exhaustive Radiographic Notes on Humerus AP and Lateral Projections

Minimum Anatomical Requirements for Humerus Radiography

• Joint Visualization: As the humerus is classified as a long bone, the minimum anatomy required for a diagnostic image includes both the proximal and distal joints. These include:
  • The shoulder joint.
  • The elbow joint.
• Soft Tissue Documentation: The image must capture the lateral soft tissue borders on both sides of the long bone throughout its length.
• Patient Orientation: A correctly positioned AP humerus can be performed in either an erect (standing or sitting) position or a supine position.

AP Humerus Projection: Positioning and Distal Evaluation

• Hand and Arm Position: The patient's hand must be supinated.
• Epicondylar Alignment: The most critical positioning factor for an AP humerus is ensuring that the humoral epicondyles are parallel to the Image Receptor (IR).
• Distal Anatomical Markers: When the epicondyles are correctly aligned parallel to the IR, the following is demonstrated:
  • The lateral epicondyles are seen in profile.
  • The radial head will demonstrate approximately one-eighth ($0.125$) to $0.25$ inches of superimposition over the ulna.
  • The anatomy visualized at the distal aspect should be the exact same demonstration as a correctly positioned AP elbow.

Proximal Anatomical Evaluation of the AP Humerus

• Greater Tubercle: When the epicondyles are parallel to the IR and the arm is in the AP position, the greater tubercle (or tuberosity) is seen in profile laterally.
• Lesser Tubercle: The lesser tubercle is typically superimposed by the humoral head in this projection.
• Cortical Margin: The vertical cortical margin of the lesser tubercle should be visualized approximately halfway between the greater tubercle and the humeral head. This appears as a distinct vertical line in the proximal bone structure.

Deviations from Correct AP Positioning: Rotational Errors

• External Rotation:
  • Distal Appearance: When the humerus is rotated externally, the radial head demonstrates less than one-eighth ($0.125$) superimposition by the ulna.
  • Epicondyles: The humeral epicondyles are not visible in profile.
  • Proximal Appearance: The greater tubercle (or tuberosity) is not seen in profile.
• Internal Rotation:
  • Distal Appearance: The radial head demonstrates more than one-eighth ($0.125$) superimposition over the ulna. At this stage, the distal humerus begins to resemble an internal oblique elbow.
  • Proximal Appearance: The greater tubercle is not in profile laterally, and the humongoepicondyles (as described in the transcript) are not in profile.

Lateral Humerus Projection: Methods and Criteria

• Projection Variations: There are two primary ways to achieve a lateral projection of the humerus:
  • Lateromedial: The arm is tucked down and positioned against the IR.
  • Mediolateral: The patient rolls into the board (IR) to achieve the lateral orientation.
• Anatomical Coverage: Like the AP, the lateral projection must include the entire long bone from the shoulder joint to the elbow joint regardless of the specific method used.
• Epicondylar Alignment: For a lateral projection, the humoral epicondyles must be perpendicular to the IR.
• Proximal Anatomical Markers (Lateral):
  • The lesser tubercle is seen in profile medially.
  • The humeral head and the greater tubercle are superimposed on one another.
• Distal Anatomical Markers (Lateral):
  • The anterior surfaces of the capitulum and the metatrochia (as transcribed) are aligned.
  • The epicondyles appear superimposed, although perfectly matching superimposition may be difficult to achieve due to natural anatomical angulation.
• Anatomical Consideration: There is typically a slight degree of angulation between the shoulder and the elbow level on both lateral methods, though the specific degree of this angulation varies between the lateromedial and mediolateral approaches.