Long Head of Biceps Tendon: Anatomy, Function, Imaging

Topic

Long head of biceps tendon

The long head of the biceps tendon (LHBT) is one of the two proximal tendons of the biceps brachii muscle. It originates from the supraglenoid tubercle of the scapula and the superior glenoid labrum, travels intra-articularly within the shoulder joint, and exits through the bicipital (intertubercular) groove of the humerus.

This tendon plays a crucial role in shoulder stabilization, acting as a dynamic depressor of the humeral head and assisting with elbow flexion and forearm supination via its continuity with the biceps muscle. Its intra-articular and extra-articular course makes it highly susceptible to tendinitis, instability, or rupture, often associated with rotator cuff pathology or shoulder impingement.

Synonyms

Long head of biceps brachii tendon
Bicipital tendon
Glenohumeral biceps tendon

Origin, Course, and Insertion

Origin: From the supraglenoid tubercle of the scapula and the superior glenoid labrum (labral anchor).
Course:
- Runs intra-articularly within the shoulder joint capsule but extra-synovially (surrounded by synovial sheath).
- Passes over the humeral head and exits the joint through the rotator interval between supraspinatus and subscapularis.
- Enters the bicipital groove (intertubercular sulcus) on the humerus, held in place by the transverse humeral ligament.
- Descends to merge with the muscle belly of the biceps brachii.
Insertion: Continues into the biceps muscle belly, which inserts onto the radial tuberosity and the bicipital aponeurosis (lacertus fibrosus).

Relations

Superiorly: Coracohumeral ligament and supraspinatus tendon.
Inferiorly: Humeral head and bicipital groove.
Medially: Subscapularis tendon.
Laterally: Greater tubercle and supraspinatus tendon.
Posteriorly: Superior glenoid labrum and joint capsule.

Tendon Sheath and Stabilizing Structures

The tendon is enclosed in a synovial sheath continuous with the glenohumeral joint synovium.
Transverse humeral ligament and fibers of the subscapularis form the roof of the bicipital groove, maintaining tendon stability.
The biceps pulley system includes the superior glenohumeral ligament (SGHL) and coracohumeral ligament (CHL), preventing medial subluxation.

Nerve Supply

Supplied by the musculocutaneous nerve (C5–C6), branch of the lateral cord of the brachial plexus.
Additional proprioceptive fibers from the suprascapular nerve (C5–C6) may innervate the proximal tendon region.

Function

Shoulder stabilization: Depresses humeral head and stabilizes it within the glenoid cavity during movement.
Elbow flexion and supination: Works synergistically with the short head of biceps brachii.
Load distribution: Reduces shear stress across the glenohumeral joint.
Dynamic restraint: Contributes to anterior shoulder stability during abduction and external rotation.

Clinical Significance

Tendinitis and tendinosis: Common due to overuse, impingement, or rotator cuff tears.
Subluxation/dislocation: Results from disruption of the biceps pulley or transverse humeral ligament.
Tear or rupture: Typically at the intra-articular origin; causes "Popeye" deformity when distal muscle retracts.
SLAP lesions (Superior Labrum Anterior to Posterior): Often involve the long head origin on the glenoid labrum.
Surgical importance: Tenotomy or tenodesis frequently performed for chronic tendinopathy.

MRI Appearance

T1-weighted images:
- Normal tendon: Low signal (dark, cord-like structure).
- Marrow of humerus: Bright due to fatty content.
- Synovial sheath: Thin, low-signal outline.
- Pathology: Partial tear or tendinopathy shows focal intermediate-to-bright signal within the tendon; discontinuity in rupture.
T2-weighted images:
- Normal tendon: Low signal, surrounded by fluid-filled bicipital groove which appears bright.
- Muscle: Intermediate-to-low signal.
- Pathology:
  - Tendinitis: High T2 signal within thickened tendon.
  - Partial tear: Focal bright intratendinous signal with fiber disruption.
  - Complete rupture: Absence of tendon in groove, with retracted stump and fluid-filled tract.
STIR:
- Normal tendon: Intermediate-to-dark signal.
- Inflammation or tear: Bright hyperintense signal in tendon or peritendinous fluid.
- Highlights reactive edema in adjacent bone or soft tissues.
Proton Density Fat-Saturated (PD FS):
- Normal tendon: Uniformly dark, low-signal cord in groove.
- Tendinitis: Linear or patchy bright signal within tendon substance.
- Subluxation: Medial displacement from groove, visible beneath subscapularis.
- Tear: Discontinuity with bright peritendinous fluid.
T1 Fat-Sat Post-Contrast:
- Normal tendon: Minimal enhancement.
- Inflamed sheath or tenosynovitis: Enhances brightly around tendon margins.
- Chronic tendinopathy: Peripheral enhancement with central low-signal fibrosis.
- Post-surgical changes: Linear enhancement at tenodesis or repair sites.

CT Appearance

Non-Contrast CT:

Tendon: Soft-tissue density band in the bicipital groove.
Bicipital groove: Clearly defined cortical margins; may show sclerosis in chronic tendinopathy.
Calcific tendinitis: Dense focal calcifications along the tendon path.
Bony changes: Irregularity or cortical remodeling at the groove in chronic inflammation.

Post-Contrast CT (standard):

Tendon itself: Non-enhancing.
Surrounding sheath or inflamed tissue: May enhance in tenosynovitis or postoperative cases.
Utility: Excellent for detecting calcific deposits, osseous erosions, or tendon displacement when MRI is contraindicated.