Structure and Location
The bicipital aponeurosis (aponeurosis m. bicipitis brachii) is a triangular tendinous band. Its fibers diverge from the medial aspect of the biceps tendon, passing obliquely and medially across the cubital fossa to blend with the deep fascia of the upper extremity (fascia propria). This reinforcement strengthens the antebrachial fascia overlying the origin of the flexor muscle group of the forearm. Near the medial margin of the cubital region, this fascial layer attaches to the ulna.
Structures Deep to the Bicipital Aponeurosis
The aponeurosis acts as a protective retinaculum bridging the medial neurovascular bundle of the cubital fossa.
Deep to the aponeurosis lie:
- Brachial artery (a. brachialis) — travels in the sulcus between the pronator teres (m. pronator teres) and brachialis (m. brachialis) muscles.
- Bifurcation of the brachial artery — typically occurring 1–2 cm inferior to the interepicondylar line of the humerus, where the artery divides into its terminal branches: the radial and ulnar arteries.
- Median nerve (n. medianus) — positioned medial to the brachial artery in the distal third of the arm.
- Deep veins — two venae comitantes (vv. brachiales) accompanying the brachial artery.
Topography of Brachial Artery Branches
Following the bifurcation of the brachial artery deep to the bicipital aponeurosis, its terminal branches course as follows:
- Radial artery (a. radialis) — courses laterally, crossing anterior to the m. biceps brachii tendon, and enters the intermuscular interval between the brachioradialis (m. brachioradialis) and pronator teres (m. pronator teres) muscles.
- Ulnar artery (a. ulnaris) — passes deep to the pronator teres muscle and runs between the superficial and deep flexor layers of the forearm.
(Note: High origin of the radial artery or a superficial brachial artery [a. brachialis superficialis] can occasionally present as an anatomical variation.)
Surrounding Structures and Landmarks
Key topographical landmarks surrounding the bicipital aponeurosis include:
- Muscles: m. brachioradialis and m. pronator teres.
- Superficial veins: v. mediana cubiti (median cubital vein), which connects the cephalic and basilic veins within the cubital fossa and sends a perforating branch to the deep venous system.
- Cutaneous nerves: Cutaneous innervation is supplied by the medial cutaneous nerve of the arm (n. cutaneus brachii medialis) and the lateral cutaneous nerve of the forearm (n. cutaneus antebrachii lateralis).
Relationship with the Biceps Brachii Muscle
The aponeurosis is an integral component of the distal insertion apparatus of the biceps brachii muscle (m. biceps brachii).
- Proximal attachments: The long head originates from the supraglenoid tubercle of the scapula (tuberculum supraglenoidale), while the short head arises from the apex of the coracoid process (processus coracoideus).
- Distal attachments: The primary tendon inserts onto the radial tuberosity (tuberositas radii), while the bicipital aponeurosis radiates into the forearm fascia. The bicipitoradial bursa (bursa bicipitoradialis) lies between the main tendon and the radial tuberosity to reduce friction.
- Function and innervation: The biceps brachii is a powerful forearm flexor and supinator. It is innervated by the musculocutaneous nerve (n. musculocutaneus).