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Upper Extremities

23 Clavicle

Anatomy & Pathology

Anatomy Overview
The clavicle is a long, slender bone forming the anterior portion of the shoulder girdle. It acts as a strut between the sternum and scapula, helping stabilize the shoulder.

  • Key Structures: sternal extremity (medial end), acromial extremity (lateral end), shaft (body), acromioclavicular joint (AC), sternoclavicular joint (SC), acromion process of the scapula, upper ribs (as landmarks)

Common Pathologies

  • Fractures: Most frequent in the midshaft; common in falls and athletic trauma.
  • Dislocations: May occur at the AC or SC joints, altering clavicular alignment.
  • Osteolytic or metastatic lesions: Destructive or sclerotic changes from metastatic disease.
  • Degenerative changes: Arthritic involvement of AC or SC joints, often with joint space narrowing and subchondral sclerosis.

Projections

AP Clavicle

CR Location & Positioning

  • SID: 40 inches
  • Patient position: Upright or supine; supine preferred for trauma
  • Adjustments: Arms at sides, shoulders in same horizontal plane
  • CR: Perpendicular to midshaft of clavicle
  • Pt. Instructions: Suspend at the end of exhalation for uniform density
  • Exposure: Moderate kVp and mAs to visualize clavicle and adjacent structures

Evaluation Criteria

  • Coverage: Entire clavicle centered and including both AC and SC joints
  • Rotation checks: Lateral half of clavicle above scapula; medial half superimposing thorax; SC joints symmetrical
  • Motion checks: Sharp cortical margins without blur
  • Technique checks: Proper penetration at SC joint without overexposure of lateral end
  • Clinical aim: Demonstrates frontal anatomy of the clavicle in true AP projection

AP Axial (Semi-Axial) Clavicle

CR Location & Positioning

  • SID: 40 inches
  • Patient position: Upright (lordotic preferred) or supine if unable to stand
  • Adjustments: Center clavicle to IR; in upright, lean backward in extreme lordosis or angle CR cephalad when supine
  • CR: Cephalic angle of 15–30° to midshaft of clavicle (thinner patients require greater angulation)
  • Pt. Instructions: Suspend at end of full inspiration to elevate clavicle above ribs
  • Exposure: Slightly higher kVp than AP to penetrate thorax

Evaluation Criteria

  • Coverage: Entire clavicle from SC to AC joint
  • Rotation checks: Clavicle projected above ribs and scapula; medial end overlapping 1st or 2nd rib
  • Motion checks: Sharp margins without ghosting
  • Technique checks: Uniform brightness and detail throughout length
  • Clinical aim: Projects clavicle free of thoracic superimposition; evaluates displacement and alignment

PA and PA Axial (Alternative Projections)

  • PA: Improves recorded detail by reducing OID; used when patient can stand or lie prone.
  • PA Axial: Similar to AP axial but with 15–30° caudal angle; projects clavicle above ribs with less magnification.

 

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Hows & Whys of Clavicle Radiography

Anatomy

  • What is a common term for the clavicle?
    The collarbone.
  • With what bone does the medial end of the clavicle articulate?
    The manubrium of the sternum at the sternoclavicular joint.
  • With what bone does the lateral end of the clavicle articulate?
    The acromion process of the scapula at the acromioclavicular joint.

Positioning 

  • Why might a PA projection be preferable to an AP?
    The PA projection reduces OID, minimizing magnification and improving spatial resolution.
  • Why is the patient instructed to suspend at the end of exhalation for the AP view?
    End-expiration lowers the shoulders slightly, allowing the clavicle to assume a more horizontal orientation and improving density uniformity.
  • Why is full inspiration used for the AP axial projection?
    Full inspiration elevates the clavicle, projecting it above the ribs for clearer visualization.
  • Why is a cephalic angulation used in the AP axial projection?
    The angle frees the clavicle from thoracic structures, improving visibility of its entire length.
  • Why might thinner patients require more angulation?
    Thinner thoraxes have less natural curvature, requiring greater CR tilt (up to 30°) to clear the ribs.

Technique & Image Evaluation 

  • How can you tell the image is a true AP?
    The SC joints are symmetrical, and the clavicle appears horizontally across the thorax without rotation.
  • How can you tell the axial projection was angled correctly?
    The clavicle appears more horizontal and is projected above the upper ribs without overlapping lung apex.
  • How can you tell if rotation occurred?
    Unequal spacing of the SC joints or distortion of the thoracic spine relative to clavicle alignment.
  • How can you tell if exposure was adequate?
    The medial end near the SC joint should be visible without burnout, and the lateral end should retain trabecular pattern.

Clinical Applications

  • When is an axial projection preferred?
    To clear the clavicle from thoracic structures, evaluate displacement after trauma, or detect subtle fractures.
  • Why might a PA axial be used instead of AP axial?
    It provides better detail and less distortion since the clavicle lies closer to the image receptor.
  • What special consideration applies for trauma imaging?
    When fracture is suspected, the supine position minimizes movement and reduces risk of further displacement.

 

License

Radiographic Procedures Review Guide Copyright © 2025 by Carla M. Allen and Taylor M. Otto. All Rights Reserved.