Oblique Cord (Ligament of Weitbrecht): Anatomy, Function, Imaging

Topic

Oblique cord (ligament of Weitbrecht)

The oblique cord, also known as the ligament of Weitbrecht, is a small but important fibrous band located on the anteromedial aspect of the proximal forearm. It extends obliquely downward and laterally from the ulnar tuberosity (below the coronoid process of the ulna) to the radius, just distal to the radial tuberosity.

Although its exact function remains debated, the oblique cord plays a role in stabilizing the proximal radioulnar joint, limiting distal displacement of the radius, and assisting load transfer between the forearm bones during pronation and supination. It forms part of the complex ligamentous system connecting the radius and ulna, alongside the interosseous membrane and annular ligament.

Synonyms

Ligament of Weitbrecht
Oblique ligament of the forearm
Accessory interosseous ligament

Origin, Course, and Insertion

Origin: Anterolateral aspect of the ulnar tuberosity, just below the coronoid process.
Course: Runs obliquely downward and laterally, crossing the space between the proximal radius and ulna. Lies anterior to the interosseous membrane.
Insertion: Attaches to the radius just distal and medial to the radial tuberosity, sometimes blending with fibers of the supinator or bicipital aponeurosis.

Relations

Anteriorly: Deep fascia of the forearm and pronator teres muscle.
Posteriorly: Interosseous membrane and adjacent radial neck.
Medially: Coronoid process and brachialis tendon.
Laterally: Bicipital tuberosity and supinator muscle.
Superiorly: Bicipital aponeurosis and radial artery (laterally).
Inferiorly: Upper part of the interosseous membrane.

Function

Forearm stability: Helps maintain alignment between radius and ulna during motion.
Force transmission: Transfers axial load from radius to ulna during weight-bearing and forearm activity.
Limitation of motion: Restricts excessive distal displacement of the radius.
Accessory support: Reinforces proximal interosseous membrane and complements the annular ligament in stabilizing the proximal radioulnar joint.

Clinical Significance

Injury: Rarely injured in isolation but may be affected in proximal radioulnar joint dislocation, radial head fractures, or interosseous membrane tears.
Radioulnar instability: Disruption may contribute to Essex-Lopresti injury pattern (radial head fracture with interosseous membrane and DRUJ disruption).
Surgical relevance: Serves as a key landmark in forearm reconstruction, tendon transfer, and ligament repair procedures.
Variant anatomy: May be absent or variable in thickness; occasionally doubled or replaced by fibrous expansions from the biceps tendon.

MRI Appearance

T1-weighted images:
- Appears as a thin, low-signal (dark) linear band between the proximal radius and ulna.
- Surrounded by bright perimuscular fat, aiding visualization.
- Adjacent biceps and supinator muscles show intermediate signal.
- Disruption or thickening may appear as irregular low-signal discontinuity with intermediate intensity edema.
T2-weighted images:
- Normal ligament: low signal (dark line) between radius and ulna.
- Pathology (tear, inflammation): bright hyperintense signal or discontinuity.
- Fluid collection between radius and ulna accentuates the cord margins.
STIR:
- Normal cord: intermediate-to-dark signal.
- Injured or inflamed ligament: bright hyperintense periligamentous signal indicating edema or partial tear.
- Excellent for detecting subtle interosseous injuries.
Proton Density Fat-Saturated (PD FS):
- Normal: dark linear band, sharply defined.
- Tear or strain: bright linear or focal hyperintensity in ligament substance.
- Useful for distinguishing partial vs. complete disruption.
T1 Fat-Sat Post-Contrast:
- Normal: minimal or no enhancement.
- Pathologic: enhancement of periligamentous tissues in inflammation or scarring.
- Post-surgical fibrosis may appear as irregular enhancement near radial tuberosity.

MRI Arthrogram Appearance

Normal: Contrast outlines the proximal radioulnar joint and interosseous recess, but does not enter the oblique cord plane.

CT Appearance

Non-Contrast CT:

The oblique cord appears as a thin soft-tissue band anterior to the proximal interosseous space.
Better identified in thin axial or oblique sagittal reconstructions.
Adjacent radial tuberosity and ulnar tubercle form key bony landmarks.
Calcification or ossification within the cord (rare) appears as linear hyperdensity.
May show associated cortical irregularity or periosteal reaction in chronic traction injury.

Post-Contrast CT (standard):

Ligament itself does not enhance, but surrounding soft-tissue enhancement may be seen in inflammation or postoperative scarring.
Periligamentous enhancement indicates active inflammation or reactive change.
Useful for evaluating bony attachment sites and detecting small avulsion fragments.

MRI images

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