Posterior humeral circumflex artery

The posterior humeral circumflex artery is a branch of the axillary artery, specifically arising from its third part. It plays a crucial role in supplying blood to the shoulder region, particularly the deltoid muscle, and other nearby structures. This artery works in conjunction with the anterior humeral circumflex artery to provide vascularization around the head of the humerus. It is often larger than the anterior humeral circumflex artery and has significant anastomotic connections.

Location

The posterior humeral circumflex artery originates from the axillary artery in the shoulder region. It travels posteriorly through the quadrangular space, a gap bordered by the teres major, teres minor, long head of the triceps brachii, and the surgical neck of the humerus. The artery accompanies the axillary nerve as it winds around the back of the surgical neck of the humerus. It supplies blood to the deltoid muscle, parts of the triceps, and the shoulder joint, making it a vital artery for upper limb vascularization.

Anatomy

The posterior humeral circumflex artery is an important vessel that provides blood to the shoulder region and nearby structures. Below is a detailed description of its origin, course, branches, and relationship with surrounding anatomical structures.

Origin

The posterior humeral circumflex artery originates from the third part of the axillary artery, which is a continuation of the subclavian artery after it passes the first rib. The axillary artery supplies the upper limb, and the posterior humeral circumflex artery branches off near the shoulder joint, typically alongside the anterior humeral circumflex artery, though the posterior artery is often larger.

Course

After originating from the axillary artery, the posterior humeral circumflex artery follows a posterior and lateral course. Its path is characterized by its travel through key anatomical spaces and its relationship with surrounding structures.

Quadrangular Space

The posterior humeral circumflex artery passes through the quadrangular space, which is a small anatomical gap located posteriorly in the shoulder region. This space is defined by:

• Superior Border: The teres minor muscle.
• Inferior Border: The teres major muscle.
• Medial Border: The long head of the triceps brachii muscle.
• Lateral Border: The surgical neck of the humerus.

Passing through this space, the artery travels alongside the axillary nerve, which innervates the deltoid and teres minor muscles.

Winding Around the Surgical Neck of the Humerus

After passing through the quadrangular space, the posterior humeral circumflex artery wraps around the posterior aspect of the surgical neck of the humerus, continuing along its lateral course.^[8] This close relationship with the humerus makes the artery vulnerable to injury in fractures of the surgical neck of the humerus.

Branches

The posterior humeral circumflex artery gives rise to several smaller branches that supply the shoulder region, muscles, and surrounding structures.

Deltoid Branches

The artery supplies multiple branches to the deltoid muscle, a major muscle of the shoulder that plays a critical role in arm abduction. These branches penetrate and nourish the muscle, ensuring a sufficient blood supply for its function.

Muscular Branches

In addition to supplying the deltoid, the posterior humeral circumflex artery also gives off muscular branches to other muscles in the posterior aspect of the shoulder, including:

• Teres Minor: A rotator cuff muscle responsible for external rotation of the arm.
• Long Head of the Triceps Brachii: This branch of the triceps muscle is involved in shoulder and elbow extension and also receives blood from the posterior humeral circumflex artery.

Anastomoses with Anterior Humeral Circumflex Artery

The posterior humeral circumflex artery forms anastomoses (connections) with the anterior humeral circumflex artery, another branch of the axillary artery.^[7] These anastomoses are crucial for ensuring an adequate blood supply to the humeral head and surrounding tissues.

Branches to the Glenohumeral Joint

The posterior humeral circumflex artery provides small branches to the glenohumeral joint, contributing to the vascular supply of this highly mobile shoulder joint. These branches are involved in maintaining the joint’s health and function by delivering oxygenated blood to the synovial tissues and surrounding structures.

Termination

The posterior humeral circumflex artery terminates by giving off further small branches that anastomose with other arteries around the shoulder region, including the acromial and deltoid branches from the thoracoacromial artery. These connections ensure that blood supply remains uninterrupted, even if one artery is blocked or compressed.

Relationship to Surrounding Structures

The posterior humeral circumflex artery has important anatomical relationships with nearby structures, particularly in the shoulder region.^[6] These relationships are crucial for understanding its course and potential implications for injury or surgery.

• Axillary Nerve: The posterior humeral circumflex artery travels through the quadrangular space alongside the axillary nerve. This nerve innervates the deltoid and teres minor muscles. The close proximity of the artery and nerve means that injuries affecting one of these structures may impact the other.
• Surgical Neck of the Humerus: The artery winds around the posterior aspect of the surgical neck of the humerus, making it vulnerable in fractures of this region. Fractures or dislocations at the surgical neck can disrupt blood flow through the artery and lead to complications in the shoulder.
• Quadrangular Space: The quadrangular space is a key anatomical area that provides a passage for both the posterior humeral circumflex artery and the axillary nerve. Compression or injury to this space, such as from a shoulder dislocation or impingement, can affect both the artery and the nerve.

Variations

The anatomy of the posterior humeral circumflex artery can vary among individuals. Some common variations include:

• Size Disparity: In some individuals, the posterior humeral circumflex artery may be smaller than usual, with the anterior humeral circumflex artery taking a more dominant role in supplying the shoulder.^[5]
• Anastomotic Patterns: The anastomotic connections between the posterior and anterior humeral circumflex arteries can vary, with some individuals having more robust connections that provide better collateral circulation.

Function

The posterior humeral circumflex artery plays a critical role in the vascular supply of the shoulder region. Its primary function is to deliver oxygenated blood to various muscles, bones, and joints in the shoulder area, ensuring that these structures receive the nutrients and oxygen they need to function properly. Below is a detailed description of its specific functions.

Blood Supply to the Deltoid Muscle

The primary function of the posterior humeral circumflex artery is to supply blood to the deltoid muscle, one of the most important muscles in the shoulder responsible for arm abduction.

• Deltoid Muscle Vascularization: The posterior humeral circumflex artery provides multiple branches that penetrate and supply the deltoid muscle. This muscle plays a crucial role in raising the arm, particularly in abduction (lifting the arm away from the body). By supplying oxygenated blood to the deltoid muscle, the artery ensures the muscle has the energy required to perform these movements effectively.
• Sustaining Muscle Function: By delivering nutrients and oxygen to the muscle, the posterior humeral circumflex artery helps maintain the strength and endurance of the deltoid during activities that require shoulder movement, such as lifting, pushing, and overhead motions.

Blood Supply to the Teres Minor Muscle

The posterior humeral circumflex artery supplies the teres minor muscle, a key muscle in the rotator cuff group responsible for stabilizing and rotating the shoulder joint.

• External Rotation of the Arm: The teres minor helps externally rotate the arm at the shoulder, a movement that is crucial for many upper limb activities.^[4] The posterior humeral circumflex artery ensures that the teres minor has adequate blood flow to maintain its function during arm rotation and shoulder stability.
• Rotator Cuff Health: By supplying blood to the teres minor, the artery plays a role in maintaining the overall health and function of the rotator cuff, a group of muscles and tendons that stabilize the shoulder joint.

Blood Supply to the Long Head of the Triceps Brachii

The posterior humeral circumflex artery also provides blood to the long head of the triceps brachii, which is involved in extending the elbow and stabilizing the shoulder joint.

• Elbow and Shoulder Extension: The long head of the triceps is important for extending the elbow and assisting in shoulder extension. The posterior humeral circumflex artery ensures that this part of the triceps has an adequate supply of blood, allowing it to generate the force required for pushing movements and overhead activities.
• Shoulder Joint Stability: The long head of the triceps also helps stabilize the shoulder joint, especially during movements involving the arm overhead. Proper blood flow from the posterior humeral circumflex artery is crucial for maintaining the strength and stability of this muscle.

Blood Supply to the Glenohumeral Joint

The posterior humeral circumflex artery plays a role in supplying blood to the glenohumeral joint, the main shoulder joint where the head of the humerus meets the glenoid cavity of the scapula.

• Joint Health: By delivering oxygenated blood to the soft tissues surrounding the joint, including the synovium and joint capsule, the posterior humeral circumflex artery helps maintain the health and function of the shoulder joint.^[3] This is important for lubricating the joint and enabling smooth, pain-free movement.
• Nutrient Supply for Cartilage and Ligaments: The small branches of the posterior humeral circumflex artery that supply the glenohumeral joint also contribute to the health of the joint’s cartilage and ligaments, which are essential for stability and mobility.

Contribution to Collateral Circulation

The posterior humeral circumflex artery plays a vital role in the collateral circulation of the shoulder, forming anastomoses (connections) with other arteries that supply the region.

• Anastomosis with Anterior Humeral Circumflex Artery: The posterior humeral circumflex artery forms an anastomosis with the anterior humeral circumflex artery, ensuring that blood flow to the shoulder region remains adequate even if one of the arteries is blocked or compromised. This collateral circulation helps maintain continuous blood supply to the deltoid muscle, humeral head, and shoulder joint.
• Support During Movement: The collateral circulation provided by the posterior humeral circumflex artery ensures that the shoulder joint and muscles receive adequate blood flow even during complex or strenuous movements, such as lifting or rotating the arm.^[2] This is particularly important for maintaining joint health and preventing ischemia (lack of blood supply) during intense physical activity.

Oxygen and Nutrient Delivery to Surrounding Tissues

Like all arteries, the primary function of the posterior humeral circumflex artery is to deliver oxygen and essential nutrients to the tissues it supplies. This is crucial for the health, maintenance, and repair of the muscles, bones, and connective tissues in the shoulder.

• Tissue Repair and Maintenance: The oxygen and nutrients delivered by the posterior humeral circumflex artery are essential for the repair and maintenance of the shoulder muscles, tendons, and joints. This is particularly important for healing after injuries, such as rotator cuff tears, shoulder dislocations, or muscle strains.
• Support for Muscle Growth and Strength: Continuous blood flow from the artery ensures that the muscles it supplies, particularly the deltoid, teres minor, and triceps, receive the necessary nutrients to maintain their strength, size, and functionality.

Support for Shoulder Movement and Stability

The posterior humeral circumflex artery’s role in vascularizing the deltoid, teres minor, and triceps brachii muscles makes it essential for shoulder movement and stability.

• Arm Abduction: By supplying blood to the deltoid muscle, the artery enables the arm to be lifted away from the body (abduction), a critical movement for activities like reaching or lifting objects overhead.
• Arm Rotation and Stabilization: The artery’s supply to the teres minor and long head of the triceps allows for proper rotation and stabilization of the shoulder joint, ensuring that the arm can move smoothly and remain stable during physical activity.

Clinical Significance

The posterior humeral circumflex artery is clinically significant due to its role in supplying blood to critical structures in the shoulder region, including the deltoid muscle, rotator cuff muscles, and the glenohumeral joint.^[1] Some key clinical points include:

• Shoulder Trauma and Fractures: The posterior humeral circumflex artery travels around the surgical neck of the humerus, making it vulnerable to injury during fractures or dislocations of the humerus. Damage to this artery can result in compromised blood flow to the deltoid and other muscles, potentially leading to muscle weakness or tissue ischemia.
• Axillary Nerve Injury: The artery accompanies the axillary nerve through the quadrangular space, meaning injuries that affect one structure often impact the other. Damage to the axillary nerve or artery can impair shoulder mobility and muscle function, particularly affecting the deltoid and teres minor muscles.
• Surgical Procedures: During shoulder surgeries, such as rotator cuff repairs or fracture fixations, care must be taken to avoid damaging the posterior humeral circumflex artery. Injury to this vessel can lead to significant bleeding and postoperative complications related to inadequate blood supply to the shoulder region.