Humeral Head: Blood Supply, Anatomy, and Clinical Significance

What is the Blood Supply of the Humeral Head?

The humeral head, the spherical upper end of the humerus forming the ball of the shoulder joint, receives its crucial blood supply primarily from an intricate anastomotic network derived from branches of the axillary artery, most notably the anterior and posterior circumflex humeral arteries, with lesser contributions from the ascending branch of the deep brachial artery.

Anatomical Context: The Humeral Head's Importance

The humeral head is a vital component of the glenohumeral joint, allowing for the wide range of motion characteristic of the shoulder. Its unique anatomical position and the forces it endures make a robust and reliable blood supply absolutely critical. Unlike many other bones, the primary blood vessels supplying the humeral head enter at specific points, making certain injuries particularly prone to compromising blood flow and potentially leading to serious complications like avascular necrosis (AVN), where bone tissue dies due to lack of blood.

Main Arterial Contributors

The blood supply to the humeral head is derived predominantly from branches of the axillary artery, a continuation of the subclavian artery that passes through the axilla. The key arteries involved include:

• Anterior Circumflex Humeral Artery (ACHA):

  • Origin: This smaller vessel typically arises from the lateral aspect of the axillary artery, running anteriorly around the surgical neck of the humerus.
  • Course and Branches: It passes deep to the deltoid and pectoralis major muscles. A significant branch, often referred to as the arcuate artery (or ascending branch of the ACHA), ascends within the bicipital groove (intertubercular sulcus). This arcuate artery is a crucial contributor, supplying the greater tuberosity and a significant portion of the superior aspect of the humeral head.
  • Supply Area: Primarily supplies the anterior and superior aspects of the humeral head and the greater tuberosity.

• Posterior Circumflex Humeral Artery (PCHA):

  • Origin: Generally larger than the ACHA, the PCHA also arises from the axillary artery, often distally to the ACHA.
  • Course and Branches: It courses posteriorly, passing through the quadrangular space (bounded by the teres major, teres minor, long head of triceps, and surgical neck of the humerus). It wraps around the surgical neck of the humerus deep to the deltoid muscle. It gives off numerous branches that penetrate the bone.
  • Supply Area: This artery is considered the dominant blood supply to the humeral head, particularly its posterior, inferior, and lateral aspects. It provides a more extensive contribution to the epiphyseal region of the humeral head than the ACHA.

• Deep Brachial Artery (Profunda Brachii Artery):

  • Origin: This artery branches off the brachial artery (a continuation of the axillary artery) in the upper arm.
  • Course and Branches: It typically gives off an ascending branch that can contribute to the arterial network around the surgical neck and humeral head, especially to the posterior aspect. While not a primary direct supplier to the head itself, it plays an important role in the collateral circulation.

• Suprascapular Artery:

  • Origin: A branch of the thyrocervical trunk (from the subclavian artery).
  • Contribution: While primarily supplying muscles of the scapula, it can contribute to the anastomotic network around the shoulder joint, potentially providing some collateral flow to the humeral head, though its direct contribution is less significant than the circumflex humeral arteries.

Anastomotic Network and Collateral Circulation

The various arterial branches supplying the humeral head do not act in isolation. They form a rich, interconnected network known as an anastomosis. This collateral circulation is vital for ensuring continuous blood flow even if one vessel is partially compromised.

• The ACHA and PCHA anastomose extensively around the surgical neck of the humerus.
• Branches from the deep brachial artery and suprascapular artery also contribute to this network, creating redundancy.
• The primary entry points for these vessels into the humeral head itself are through small foramina (openings) located mainly at the greater and lesser tuberosities, as well as the bicipital groove.

Clinical Significance: Why This Matters

Understanding the blood supply to the humeral head is paramount in clinical practice, particularly in orthopedics and sports medicine:

• Fractures of the Humeral Neck: Fractures, especially those involving the anatomical neck (just below the humeral head articular surface) or surgical neck (the constriction below the tuberosities), pose a significant risk to the blood supply.
  • Anatomical Neck Fractures: These are particularly problematic because they occur proximal to the main entry points of the circumflex humeral arteries, often disrupting the direct supply to the humeral head.
  • Surgical Neck Fractures: While more common, the risk of AVN depends on the displacement and comminution (fragmentation) of the fracture. Highly displaced or comminuted fractures can sever the critical ascending branches that supply the head, leading to ischemia.
• Avascular Necrosis (AVN): When the blood supply to the humeral head is severely compromised or interrupted (e.g., due to trauma, chronic steroid use, or certain medical conditions), the bone tissue can die. This leads to collapse of the articular surface, pain, and severe functional limitations, often necessitating surgical intervention such as shoulder replacement (arthroplasty).
• Shoulder Dislocations: Severe or recurrent glenohumeral dislocations can also potentially damage the surrounding vascular structures, though AVN is a less common complication compared to fractures.
• Surgical Planning: Orthopedic surgeons rely on a detailed understanding of this vascular anatomy when performing procedures such as fracture repair, shoulder arthroplasty, or tumor resections to preserve blood flow and optimize patient outcomes.

Conclusion

The blood supply to the humeral head is a sophisticated and vital arterial network, primarily orchestrated by the anterior and posterior circumflex humeral arteries, with supportive roles from other vessels. This intricate vascularization is essential for maintaining the viability and health of the bone, enabling the shoulder's remarkable mobility. Any disruption to this supply, particularly from trauma like displaced humeral neck fractures, carries a significant risk of severe complications such as avascular necrosis, underscoring the critical importance of this anatomical knowledge for both clinicians and those interested in musculoskeletal health.