Coracoclavicular Ligaments: Anatomy, Function, Imaging

Topic

Coracoclavicular Ligaments

The coracoclavicular ligaments are a pair of strong, fibrous bands that connect the coracoid process of the scapula to the inferior surface of the clavicle, forming the principal stabilizers of the acromioclavicular (AC) joint. These ligaments — the conoid and trapezoid — act together to suspend the scapula and upper limb from the clavicle, maintaining alignment between the clavicle and scapula during shoulder movement.

They are essential for vertical and rotational stability of the AC joint and play a key role in counteracting the weight of the upper limb. Disruption of these ligaments occurs in shoulder separations (AC joint dislocations), with the severity graded according to the Rockwood classification.

Synonyms

Coracoclavicular complex
Claviculo-coracoid ligaments
Conoid and trapezoid ligaments

Location and Structure

The coracoclavicular ligament complex consists of two distinct components:
- Conoid ligament:
  - Medial and posterior component
  - Triangular in shape
  - Extends from the conoid tubercle on the inferior surface of the clavicle to the base of the coracoid process of the scapula
- Trapezoid ligament:
  - Lateral and anterior component
  - Broad and quadrilateral
  - Extends from the trapezoid line on the inferior surface of the clavicle to the superior surface of the coracoid process
The two ligaments form a V-shaped configuration, with the apex directed inferiorly toward the coracoid process.
The conoid ligament is more vertical, and the trapezoid ligament more oblique, resisting different vectors of force.

Relations

Superiorly: Clavicle and deltoid muscle
Inferiorly: Coracoid process and coracoacromial ligament
Anteriorly: Pectoralis minor tendon
Posteriorly: Trapezius and coracobrachialis origins
Medially: Conoid ligament
Laterally: Trapezoid ligament

Attachments

Conoid ligament:
- Origin: Base of coracoid process (posteromedial aspect)
- Insertion: Conoid tubercle on inferior clavicle
Trapezoid ligament:
- Origin: Upper surface of coracoid process (anterolateral aspect)
- Insertion: Trapezoid line on inferior clavicle

Nerve Supply

Sensory fibers from the suprascapular nerve and lateral pectoral nerve contribute to ligamentous innervation.

Function

Primary stabilizer: Anchors clavicle to scapula, maintaining acromioclavicular alignment.
Prevents vertical displacement: Resists downward movement of the scapula relative to the clavicle.
Resists rotation: Conoid ligament controls posterior rotation of clavicle; trapezoid resists anterior shearing.
Transmits load: Transfers upper limb weight to the axial skeleton.
Assists in scapular motion coupling: Coordinates scapular rotation during shoulder elevation.

Clinical Significance

Acromioclavicular joint dislocation:
- Grade II–III injuries involve partial or complete rupture of coracoclavicular ligaments.
- Clinically presents with shoulder step deformity and limited overhead motion.
Fracture association: May avulse the conoid tubercle or coracoid base.
Calcification: Chronic stress or post-traumatic changes may lead to visible ligament calcification.
Reconstruction: Surgical repair or augmentation is often required in severe AC joint separations.
Imaging relevance: MRI and CT are key for diagnosing ligament tears, avulsions, and evaluating post-repair integrity.

MRI Appearance

T1-weighted images:
- Ligament fibers: Low signal (dark), continuous band between clavicle and coracoid.
- Bone marrow (clavicle/coracoid): Bright fatty signal.
- Surrounding fat: High signal, enhancing ligament visualization.
- Tear: Disruption or discontinuity of dark band with surrounding intermediate-to-bright signal (hematoma).
T2-weighted images:
- Normal ligament: Low signal intensity.
- Acute tear: Hyperintense fluid replacing ligament fibers; loss of continuity.
- Chronic injury: Thickened, irregular, or wavy low-signal band with adjacent edema or fibrosis.
- Partial tear: Focal bright signal within ligament substance.
STIR:
- Normal ligament: Dark band.
- Pathology: Bright hyperintense signal indicating edema, hemorrhage, or inflammation in acute injury.
- Useful for detecting subtle partial tears or periligamentous edema.
Proton Density Fat-Saturated (PD FS):
- Normal: Low signal, sharply defined margins.
- Tear: Bright hyperintensity and surrounding soft-tissue edema.
- Post-surgical changes: Variable signal with mild periligamentous enhancement.
T1 Fat-Sat Post-Contrast:
- Normal ligament: Minimal or no enhancement.
- Inflammation or postoperative repair: Mild diffuse enhancement.
- Chronic fibrosis: Peripheral enhancement with central low-signal scar tissue.

CT Appearance

Non-Contrast CT:

Ligaments: Seen as soft-tissue bands connecting coracoid process to clavicle.
Bone landmarks: Conoid tubercle and trapezoid line on clavicle, coracoid base and surface on scapula.
Pathology:
- Avulsion fractures at insertion points.
- Calcification or ossification within ligament (post-traumatic or degenerative).
- AC joint malalignment due to ligament rupture.

Post-Contrast CT (standard):

Normal ligaments: No direct enhancement.
Inflammation or repair tissue: May show soft-tissue enhancement near ligament origin or insertion.
Useful for:
- Detecting peri-ligamentous edema, hematoma, or post-surgical grafts.
- Assessing bone-ligament interface in chronic injury or reconstruction.

MRI images

CT image

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