Antebrachial Fascia

The antebrachial fascia is the deep fascia of the forearm. It is a strong, fibrous connective tissue layer that encloses the muscles of the forearm and helps form the boundaries of the anterior (flexor-pronator) and posterior (extensor-supinator) compartments. It also plays a role in forming specialized structures such as the flexor and extensor retinacula at the wrist.

Location

The antebrachial fascia surrounds the entire forearm, extending from the brachial fascia at the elbow to the palmar fascia and dorsal hand fascia at the wrist. It lies beneath the skin and superficial fascia, superficial to the muscles, vessels, and nerves.

Structure

• Thick, collagenous, and continuous with brachial fascia above and hand fascia below.
• Sends intermuscular septa to the radius and ulna, dividing the forearm into two major compartments.
• Thickens distally to form:
  • Flexor retinaculum (volar carpal ligament)
  • Extensor retinaculum (dorsal carpal ligament)
• Connected by the interosseous membrane between radius and ulna.

Compartments Formed

Function

• Compartmentalization: Separates forearm muscles into flexor and extensor groups.
• Force Transmission: Provides a firm structure for muscles to contract against.
• Venous Return Support: Helps compress veins during muscle movement.
• Retinaculum Formation: Distal thickening forms strong fibrous bands that prevent tendon bowstringing.

Relations

• Superficial to: Muscles, nerves (median, ulnar, radial), radial and ulnar arteries
• Deep to: Skin and superficial fascia (housing cephalic, basilic, and median cubital veins)

Blood Supply

• Small perforating branches from the radial, ulnar, and interosseous arteries

Innervation

The fascia itself has minimal sensory innervation, though adjacent nerves (e.g., medial antebrachial cutaneous nerve) may supply overlying skin and superficial fascia.

Surface Anatomy

The antebrachial fascia influences the contour and firmness of the forearm. It is particularly thick in the distal third, where it anchors muscles and transitions into the carpal retinacula.

Development

Arises from mesenchymal connective tissue of the limb bud. Its specialization in the distal forearm (retinacula) reflects functional demands of tendon control and muscle force routing during hand and wrist activity.

Anatomical Variations

• Thickness varies between individuals and dominant vs. non-dominant limbs.
• May contain accessory fascial bands, especially near the wrist.
• Flexor retinaculum may be unusually thick or have septations contributing to carpal tunnel syndrome.

Clinical Significance

• Forearm Compartment Syndrome: Increased pressure within the compartments may require surgical fasciotomy through the antebrachial fascia.
• Carpal Tunnel Syndrome: The antebrachial fascia contributes to the flexor retinaculum, which may compress the median nerve if thickened or inflamed.
• Surgical Landmark: Used in orthopedic and vascular access procedures to navigate compartments and neurovascular structures.

Comparative Anatomy

In quadrupeds, the antebrachial fascia is generally thinner and more elastic. In humans, it has adapted to support fine motor control, tendon containment, and wrist stability necessary for tool use and manual dexterity.