Sternoclavicular (SC) Joints

Thorax and Abdomen

6 Sternoclavicular (SC) Joints

Anatomy:

Pathology & clinical relevance:

CR Location & Positioning

SID: typically 40 inches
Patient prone or erect (upright)
Arms relaxed at sides (palms posterior) to bring shoulders forward/reduce distance from joints to IR
Center midsagittal plane to midline of IR
Direct CR perpendicular to IR, at level T2–T3 (≈ 3 inches inferior to C7 spinous process, or at a level even with the top of the scapulae)
Exposure made on expiration (less lung volume helps equalize thoracic density)

Evaluation Criteria

Both SC joints visible, symmetric
No overlap from medial clavicles or sternum
Clear joint space of SC joints
No rotation (medial clavicular ends equidistant from vertebra)
Sharp bony margins, minimal motion
The image should be collimated to include the medial third of both clavicles and the manubrium.

CR Location & Positioning

SID: typically 40 inches
Patient prone or erect
Arms relaxed with palms facing posteriorly
Rotate patient 10–15° (slightly) toward side of interest (i.e., RAO for right SC, LAO for left)
CR perpendicular to IR
CR centered to the same level as PA (T2–T3, i.e. a point 3 inches inferior to the C7 spinous process, or at a level even with the top of the scapulae), and 1–2″ lateral toward the elevated side (i.e., the joint of interest)
Exposure on expiration (same as PA)

Evaluation Criteria

The manubrium and the down-side (side toward IR) SC joint is demonstrated free from superimposition by the vertebral column.
Joint space and articulation between the clavicle and manubrium surfaces clearly seen
The sternoclavicular joint on the side opposite the obliquity will be foreshortened and obscured by the bony thorax.
Sharp margins, no motion
Compare with opposite side (for asymmetry)
Collimation should include the medial third of both clavicles, the sternoclavicular joints, and the manubrium, ensuring tight collimation to minimize scatter.

Trauma / limited mobility: Use supine PA or obliques if patient cannot stand. Adjust centering accordingly. PA obliques will demonstrate the up-side SC joint.
Pediatric: Lower exposure factors, use immobilization if needed.
Large body habitus: Increase kVp to penetrate thoracic density, ensure CR is aligned to T2–T3 despite soft tissue thickness.
Suspected posterior dislocation: Consider additional specialized views (e.g. 40° cephalad tube angle, i.e. “Serendipity” view ) or cross-sectional imaging (CT).

kVp: 70–80 (moderate, to balance bone and soft tissue detail)Why perform a PA first?
To demonstrate both SC joints symmetrically and assess for gross displacement.
mAs: Low, short exposure time to minimize motion
Collimation: Tight collimation to SC region reduces scatter and improves contrast
Shielding: Gonadal shielding where appropriate without covering anatomy
Respiration: Exposure on expiration for consistency and density control

Why perform a PA first?
To demonstrate both SC joints symmetrically and assess for gross displacement.
Why do obliques after the PA?
To demonstrate each SC joint free from superimposition.
Why is correct rotation important?
Too little rotation keeps the joint superimposed on the spine; too much rotation foreshortens and distorts the joint.

Positioning & Rotation

How can you tell that a patient was not rotated on a PA SC image?
The sternoclavicular joints are equal distance from the vertebrae.
How can you tell that the patient for PA SC joints is not rotated before taking the image?
The shoulders are equal distance from the bucky.
What bony landmarks can be used to position for SC joints?
The top of the scapula or about 3 inches below the vertebra prominens.
What vertebral level are the SC joints located at?
T2–T3.

Obliques

How can you tell that the degree of obliquity was correct on anterior oblique projections?
The joint of interest is visualized free from superimposition of other bony structures.
On anterior obliques of the SC joints, which joint is best demonstrated?
The joint on the downside (closest to the IR).
If your patient’s condition requires posterior obliques, which joint will be best visualized?
The joint on the upside (farthest from the IR).
Why are posterior obliques less desirable than anterior obliques?
Because they result in greater magnification and less detail due to increased OID.

Respiration & Image Quality

Why should SC joint images be exposed on expiration?
To reduce thoracic volume and make density more uniform.
Why should posterior oblique images be taken on suspended respiration?
To minimize motion blur.
Why is short exposure time important?
To reduce motion and ensure sharp bony margins.