SGHL Ligament: Anatomy, Function, Injury, and Management

What is the SGHL ligament?

The SGHL ligament, or Superior Glenohumeral Ligament, is a key fibrous band within the shoulder joint capsule that plays a crucial role in maintaining glenohumeral stability, particularly in preventing inferior and posterior translation of the humeral head.

Anatomy and Location

The Superior Glenohumeral Ligament (SGHL) is one of three primary glenohumeral ligaments, alongside the Middle Glenohumeral Ligament (MGHL) and the Inferior Glenohumeral Ligament (IGHL) complex. These ligaments are thickenings of the anterior joint capsule of the shoulder, connecting the scapula's glenoid fossa to the humerus.

• Origin: The SGHL originates from the superior aspect of the glenoid labrum, often near the supraglenoid tubercle, which is the attachment point for the long head of the biceps brachii tendon.
• Insertion: It extends laterally and inferiorly to insert onto the anatomical neck of the humerus, typically blending with the joint capsule near the lesser tuberosity.
• Relationship to Rotator Interval: The SGHL forms the superior border of the "rotator interval," a triangular space in the shoulder joint capsule located between the supraspinatus and subscapularis tendons. This region also contains the coracohumeral ligament and the long head of the biceps tendon.

Structure and Composition

Like other ligaments, the SGHL is composed primarily of dense regular connective tissue. Its main structural component is Type I collagen fibers, which provide high tensile strength, allowing it to resist stretching and maintain joint integrity. While robust, it is generally considered the smallest and thinnest of the three glenohumeral ligaments, especially when compared to the robust Inferior Glenohumeral Ligament complex. Its specific orientation and fiber alignment contribute to its unique biomechanical function.

Primary Function and Biomechanics

The SGHL is a vital passive stabilizer of the glenohumeral joint, acting as a check-rein in specific arm positions. Its primary biomechanical roles include:

• Restricting Inferior Translation: The most recognized function of the SGHL is its role in preventing the humeral head from sliding excessively downwards (inferiorly) out of the glenoid fossa, particularly when the arm is adducted (hanging at the side) and in neutral rotation.
• Limiting Posterior Translation: It also contributes to limiting posterior translation of the humeral head, especially when the arm is adducted and internally rotated.
• Controlling External Rotation: The SGHL provides some restraint against excessive external rotation, particularly in positions of adduction and neutral to slight abduction.
• Stabilizing the Long Head of Biceps: Due to its close anatomical proximity and its role in forming the rotator interval, the SGHL works in conjunction with the coracohumeral ligament to stabilize the long head of the biceps tendon, preventing its subluxation or dislocation from the bicipital groove.

Clinical Significance and Injury

While less commonly injured in isolation than other shoulder structures, the SGHL can be implicated in various shoulder pathologies:

• Shoulder Instability: Laxity or injury to the SGHL can contribute to glenohumeral instability, particularly inferior subluxation or multidirectional instability (MDI) of the shoulder.
• Rotator Interval Lesions: Injuries to the SGHL are often associated with pathologies of the rotator interval, such as rotator cuff tears (especially supraspinatus and subscapularis) or biceps tendon pathologies.
• Adhesive Capsulitis (Frozen Shoulder): The SGHL, as part of the rotator interval, can become thickened and contracted in cases of adhesive capsulitis, contributing to the painful restriction of shoulder movement.
• Diagnosis: Injuries or abnormalities of the SGHL are typically diagnosed through a combination of clinical examination, advanced imaging techniques such as Magnetic Resonance Imaging (MRI), and sometimes confirmed via arthroscopy.

Role in Shoulder Stability

The SGHL is an integral component of the shoulder's complex passive stabilization system. While the dynamic stabilizers (rotator cuff muscles, deltoid, biceps, triceps) provide active control during movement, the ligaments provide static stability, preventing excessive translation and dislocation. The SGHL's specific contribution to stability is most pronounced in certain arm positions, particularly when the arm is at the side, complementing the roles of the MGHL (which limits external rotation in mid-range abduction) and the IGHL complex (the primary stabilizer in abduction and external rotation).

Interactions with Other Structures

The SGHL does not function in isolation; its efficacy is intertwined with that of surrounding anatomical structures:

• Coracohumeral Ligament (CHL): These two ligaments are often considered biomechanically linked, especially in their role in the rotator interval and in stabilizing the long head of the biceps tendon. They collectively limit inferior translation of the humeral head.
• Glenoid Labrum: The SGHL originates from the labrum, and labral tears (e.g., SLAP lesions) can affect the integrity and function of the ligament.
• Long Head of Biceps Tendon: Due to its close proximity and shared attachment area, pathologies involving the biceps tendon (e.g., instability, tears) can directly impact or be associated with SGHL issues.
• Rotator Cuff Muscles: While ligaments provide passive stability, the rotator cuff muscles provide dynamic stability. Weakness or tears in the rotator cuff can increase reliance on passive stabilizers like the SGHL, potentially leading to increased stress or injury.

Rehabilitation and Management

Management of SGHL pathologies typically follows principles similar to other ligamentous injuries of the shoulder:

• Conservative Management: For mild laxity or strains, physical therapy is often the first line of treatment. This focuses on:
  • Strengthening: Building strength in the rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis) and scapular stabilizers.
  • Proprioception: Exercises to improve joint awareness and control.
  • Range of Motion: Restoring pain-free movement.
• Surgical Intervention: Surgical repair or reconstruction of the SGHL in isolation is rare. More commonly, if surgical intervention is required, it is part of a broader procedure to address overall shoulder instability, such as a capsular shift or labral repair, especially if associated with other significant injuries. Post-surgical rehabilitation is crucial for restoring function and preventing recurrence.

Conclusion

The Superior Glenohumeral Ligament, or SGHL, though often overshadowed by its larger counterparts, is a critically important, albeit subtle, component of shoulder stability. Its specific role in limiting inferior and posterior translation of the humeral head, particularly when the arm is at rest or in specific rotational positions, underscores its significance. Understanding the SGHL's anatomy, biomechanics, and clinical relevance is essential for clinicians, trainers, and individuals seeking to comprehend and maintain optimal shoulder health and function.