Upper Extremities
Humerus
Anatomy
Routine Projections (ARRT- Required)
AP Humerus
CR Location & Positioning
- SID: 40 inches (102 cm)
- Patient position: Upright preferred (standing or seated) or supine if necessary. Place the back against the upright Bucky or table.
- Adjustments: Abduct the arm slightly and supinate the hand. Align humeral epicondyles parallel with the IR plane so the shoulder and elbow are in the same horizontal plane.
- CR (angle and centering): Perpendicular to mid-humerus, centered midway between shoulder and elbow.
- Patient instructions: Suspend respiration during exposure.
- Exposure: Use 70–85 kVp range. Collimate to include the entire humerus and both joints.
Evaluation Criteria
- Coverage: Entire humerus including shoulder and elbow joints visible; 1 inch of forearm and entire shoulder joint included.
- Rotation checks: Humeral epicondyles seen in profile; greater tubercle in profile laterally; lesser tubercle between humeral head and greater tubercle.
- Motion checks: Sharp bony margins and trabecular detail indicate no motion.
- Technique checks: Uniform brightness and contrast from proximal to distal; soft tissue and bone detail visible; no artifacts.
- Clinical aim: Demonstrates humeral shaft and shoulder articulation for trauma, pathology, or degenerative evaluation.
Lateral Humerus
CR Location & Positioning
- SID: 40 inches (102 cm)
- Patient position: Upright or supine.
- Adjustments: Flex the elbow 90 degrees and internally rotate the arm so the palm rests on the hip, placing epicondyles perpendicular to the IR.
- CR (angle and centering): Perpendicular to mid-humerus, centered midway between shoulder and elbow.
- Patient instructions: Suspend respiration.
- Exposure: 70–85 kVp, same technique range as AP for comparison.
Evaluation Criteria
- Coverage: Entire humerus including shoulder and elbow joints.
- Rotation checks: Humeral epicondyles superimposed; lesser tubercle in profile medially; greater tubercle superimposed over humeral head.
- Motion checks: Sharp humeral outline and trabecular pattern.
- Technique checks: Even brightness and contrast; visible soft tissue and bony trabeculae.
- Clinical aim: Demonstrates the entire humerus in a true lateral projection; used for trauma, dislocation, or alignment assessment.
Transthoracic Lateral Humerus (Lawrence Method)
CR Location & Positioning
- SID: 40 inches (102 cm)
- Patient position: Upright or supine lateral, affected arm against the upright Bucky. Raise the unaffected arm above the head to clear the humerus.
- Adjustments: Ensure the midcoronal plane is perpendicular to the IR. If the patient cannot elevate the arm fully, angle the CR 10–15° cephalad.
- CR (angle and centering): Perpendicular to the surgical neck (or angled 10–15° cephalad if limited mobility).
- Patient instructions: Perform shallow breathing during exposure if possible; otherwise suspend respiration.
- Exposure: Use a long exposure time (3–5 seconds) with low mA to blur ribs and lung markings.
Evaluation Criteria
- Coverage: Proximal humerus and shoulder joint included; entire shaft if possible.
- Rotation checks: Epicondyles superimposed; minimal rib superimposition over the humerus.
- Motion checks: Ribs appear blurred with breathing technique; humerus remains sharply defined.
- Technique checks: Adequate penetration through thorax; soft tissue and bone detail visible.
- Clinical aim: Used when fracture or immobilization prevents conventional lateral positioning; demonstrates the proximal humerus without moving the injured limb.
Hows & Whys of Humerus Radiography
Anatomy
- What structure articulates with the head of the humerus?
The glenoid cavity of the scapula. - What bony landmark is a frequent fracture site on the humerus?
The surgical neck. - Which tubercle serves as the insertion for the subscapularis muscle?
The lesser tubercle. - Which depression receives the olecranon process during elbow extension?
The olecranon fossa.
Positioning
- Why must the hand be supinated for the AP projection?
Supination aligns the humeral epicondyles parallel to the IR, ensuring a true AP without rotation. - Why is the elbow flexed 90° and the hand placed on the hip for the lateral projection?
This internal rotation makes the epicondyles perpendicular to the IR and places the humerus in a true lateral position. - Why is the transthoracic lateral projection used for suspected fractures?
It visualizes the proximal humerus without rotating or manipulating the injured arm. - Why must both the shoulder and elbow joints be included on AP and lateral images?
To ensure accurate evaluation of alignment, possible fracture extension, and joint integrity.
Technique & Image Evaluation
- How can you tell the humerus was properly positioned for the AP projection?
The greater tubercle appears in profile laterally and the epicondyles are parallel to the IR. - How can you tell the humerus was properly positioned for the lateral projection?
The lesser tubercle is seen in profile medially and the epicondyles are perfectly superimposed. - How can you confirm correct centering on the transthoracic lateral projection?
The proximal humerus is clearly visible through the thorax at the level of the surgical neck. - How can you verify that a breathing technique was successful on the transthoracic lateral?
The ribs appear blurred while the humeral cortex remains sharp, confirming motion of soft tissue only. - How can you tell that exposure technique was appropriate?
Soft tissue and bony trabeculae are visible throughout; no clipped highlights or lost cortical definition.
Clinical Applications
- When would the transthoracic lateral projection be preferred?
When the patient has a suspected fracture or casted humerus that cannot be rotated. - Why is it critical to assess both proximal and distal joints on humerus projections?
Fracture displacement or angulation may involve the shoulder or elbow, affecting surgical planning or reduction.
