Inferior Glenohumeral Ligament Posterior Band: Anatomy & Imaging

Topic

Inferior glenohumeral ligament posterior band

The posterior band of the inferior glenohumeral ligament (IGHL) is a thickened portion of the inferior glenohumeral ligament complex, which stabilizes the shoulder joint during abduction and internal rotation. The IGHL forms a hammock-like structure between the glenoid labrum and the anatomic neck of the humerus, consisting of anterior and posterior bands connected by the axillary pouch.

The posterior band becomes taut in flexion, adduction, and internal rotation, preventing posterior translation of the humeral head and posterior dislocation. It is particularly important in stabilizing the joint when the shoulder is elevated and rotated, contributing to posterior capsular reinforcement.

Synonyms

Posterior band of the inferior glenohumeral ligament (IGHL-PB)
Posterior inferior glenohumeral capsular ligament
Posterior inferior capsuloligamentous band

Location and Structure

Origin: Posterior-inferior margin of the glenoid labrum and adjacent glenoid rim.
Course: Passes laterally and slightly superiorly across the posterior-inferior aspect of the glenohumeral joint capsule.
Insertion: Posterior-inferior aspect of the anatomic neck of the humerus, blending with the joint capsule.
Composition: Dense collagen fibers continuous with the joint capsule; forms part of the capsuloligamentous complex of the shoulder.
Associated structure: Continuous medially with the axillary recess and anteriorly with the anterior band of the IGHL.

Relations

Anteriorly: Axillary pouch of the inferior capsule and humeral head
Posteriorly: Posterior capsule and infraspinatus tendon
Superiorly: Posterior labrum and glenoid rim
Inferiorly: Inferior capsule and axillary recess
Medially: Glenoid labrum (origin)
Laterally: Humeral attachment on anatomic neck

Nerve Supply

Supplied by articular branches of the axillary nerve and suprascapular nerve, contributing to capsular innervation.

Function

Joint stability: Prevents posterior and inferior translation of the humeral head, particularly in flexion and internal rotation.
Posterior restraint: Key static stabilizer against posterior dislocation.
Humeral head centering: Works synergistically with rotator cuff and labrum to maintain congruency.
Capsular reinforcement: Strengthens posterior-inferior capsule, limiting excessive laxity.
Dynamic interplay: Tightens during internal rotation and relaxes during external rotation.

Clinical Significance

Posterior shoulder instability: Laxity or tear of the posterior IGHL band contributes to recurrent posterior dislocations.
Capsulolabral injuries: Commonly associated with reverse Bankart lesions or posterior labral tears.
Posterior band thickening: May be seen in chronic microtrauma or adaptive capsular hypertrophy in throwers.
Posterior capsular contracture: Leads to limited internal rotation and compensatory anterior impingement.
Surgical importance: Repaired or tightened during posterior capsulolabral reconstruction procedures.
Imaging relevance: MRI essential for detecting capsular detachment, thickening, or partial tearing.

MRI Appearance

T1-weighted images:
- Ligament: Low signal (dark linear band) contiguous with joint capsule.
- Surrounding fat: Bright, outlining the ligament’s margins.
- Humeral and glenoid attachments appear as low-signal points blending with cortical bone.
- Thickening or discontinuity indicates injury or scarring.
T2-weighted images:
- Normal ligament: Low signal, sharply defined against bright joint fluid.
- Partial tear: Focal hyperintense signal within ligament fibers.
- Complete tear: Discontinuity with fluid interposed between humeral and glenoid attachments.
- Posterior capsular thickening or synovitis may appear intermediate-to-bright.
STIR:
- Ligament: Intermediate-to-dark in normal state.
- Edematous or inflamed capsule: Bright hyperintense signal, particularly at humeral attachment.
- Excellent for detecting posterior capsular strain, sprain, or contusion.
Proton Density Fat-Saturated (PD FS):
- Ligament: Intermediate-to-dark, with uniform thickness.
- Injury: Bright hyperintense foci or irregular margins at attachment sites.
- Best for identifying subtle posterior band sprains, partial detachment, or capsular tears.
T1 Fat-Sat Post-Contrast:
- Normal posterior band: Thin low-signal structure with minimal enhancement.
- Inflamed capsule or synovitis: Focal or diffuse enhancement along posterior capsule.
- Capsulolabral tear: Linear enhancement along posterior labral interface or humeral neck.
- Postoperative fibrosis: Peripheral rim enhancement around repair site.

CT Appearance

Non-Contrast CT:

Ligament itself is not directly visualized, but bony landmarks (glenoid rim, humeral neck) are well defined.
Indirect signs:
- Glenoid or humeral avulsion fragments (bony reverse Bankart lesion).
- Cortical irregularity at posterior glenoid rim indicating chronic stress or detachment.
Useful for evaluating associated bony pathology in posterior shoulder instability.

Post-Contrast CT (standard):

Enhancing posterior capsule or soft-tissue density may indicate capsular inflammation or fibrosis.
CT arthrography:
- Contrast outlines the posterior band and capsule.
- Extravasation or pouch expansion indicates capsular tear or detachment.
- Reverse Bankart lesions seen as contrast extending beneath posterior labrum.

MRI image

MRI image 1mm

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