Topics

Topic

design image
Trapezoid Line

The trapezoid line is a rough, oblique ridge located on the inferior surface of the lateral clavicle. It serves as the attachment site for the trapezoid ligament, one of the two components of the coracoclavicular ligament complex, and plays a key role in stabilizing the acromioclavicular joint.

It is an important bony landmark in shoulder anatomy, trauma evaluation, and imaging of the clavicle and acromioclavicular region.

Synonyms

  • Trapezoid ridge

  • Line for the trapezoid ligament

Location

  • Located on the inferior surface of the lateral third of the clavicle

  • Anterior and lateral to the conoid tubercle

  • Near the acromial end of the clavicle

  • Inferior to the clavicular shaft

  • Superior to the coracoid process of the scapula

Anatomical components

  • Roughened bony ridge on the clavicle

  • Ligament attachment site:

    • Trapezoid ligament (part of the coracoclavicular ligament)

  • Associated structures:

    • Conoid tubercle (posteromedial)

    • Acromioclavicular joint (lateral proximity)

Relations

Anteriorly:

  • Subclavius muscle and fascia

Posteriorly:

  • Conoid tubercle

Inferiorly:

  • Trapezoid ligament

  • Coracoid process of the scapula

Superiorly:

  • Clavicular shaft

Laterally:

  • Acromioclavicular joint

Medially:

  • Conoid tubercle region

X-ray appearance

Plain radiographs (AP clavicle and shoulder views):

  • Trapezoid line: Usually not distinctly visible due to its inferior location

  • Indirect identification: Inferred from clavicular contour near the lateral third

  • AC joint region: Helps localize trapezoid line relative to joint

CT appearance

Non-contrast CT:

  • Trapezoid line: Seen as a subtle roughened ridge on the inferior surface of the lateral clavicle

  • Cortical margins: Slight cortical irregularity corresponding to ligament attachment

  • Spatial detail: Best modality for direct visualization of the trapezoid line

  • Relationship: Clearly shows proximity to conoid tubercle and AC joint

MRI appearance

T1-weighted images:

  • Clavicular cortex: Low signal intensity

  • Marrow: High signal within the clavicle

  • Trapezoid line region: Subtle cortical irregularity with adjacent ligament attachment

T2-weighted images:

  • Cortex: Low signal

  • Trapezoid ligament: Low-to-intermediate signal band attaching at the trapezoid line

  • Surrounding soft tissues: Higher signal than ligament

STIR:

  • Fat suppression: Uniform suppression of marrow fat

  • Ligament insertion: Clearly visualized against suppressed marrow

  • Adjacent soft tissues: High signal contrast

Proton density fat-saturated (PD FS):

  • Bone marrow: Suppressed fat signal

  • Trapezoid ligament fibers: Well seen as low-signal bands attaching to the trapezoid line

X ray image

Trapezoid Line x ray anatomy labelled image-img-00000-00000

CT image

Trapezoid Line ct coronal

CT VRT 3D image

Trapezoid line 3d image