Circumflex scapular artery

The circumflex scapular artery is a branch of the subscapular artery, which itself arises from the third part of the axillary artery. It is a key vessel that supplies blood to the muscles and structures in the scapular (shoulder blade) region. The circumflex scapular artery plays a significant role in the vascular network that surrounds the scapula, providing blood to important muscles involved in shoulder movement.

Location

The circumflex scapular artery originates from the subscapular artery, which branches off from the axillary artery near the lower border of the subscapularis muscle. The circumflex scapular artery passes through the triangular space formed by the teres major, teres minor, and the long head of the triceps brachii. It curves around the lateral border of the scapula and supplies the muscles on the posterior aspect of the scapula, including the teres major, teres minor, and infraspinatus muscles.

Structure and Anatomy

The circumflex scapular artery is an important branch of the subscapular artery, which arises from the axillary artery. It supplies blood to the posterior shoulder region and is part of the scapular vascular network. Below is a detailed description of the anatomy of the circumflex scapular artery, including its origin, course, branches, and relationship with surrounding structures.

Origin

The circumflex scapular artery originates from the subscapular artery, which is the largest branch of the axillary artery. The subscapular artery arises from the third part of the axillary artery, near the lower border of the subscapularis muscle. The circumflex scapular artery branches off from the subscapular artery shortly after the subscapular artery’s origin, just below the shoulder joint. It serves as an important source of blood supply to the muscles and bones around the scapula.

Course

The circumflex scapular artery takes a curved course around the scapula. Its path can be described in two distinct segments: through the triangular space and around the scapula.

Passing Through the Triangular Space

After branching from the subscapular artery, the circumflex scapular artery passes posteriorly through the triangular space. The triangular space is a small gap between the muscles of the posterior shoulder. It is bordered by:

• Superior Border: Teres minor muscle.
• Inferior Border: Teres major muscle.
• Lateral Border: Long head of the triceps brachii muscle.

This space allows the circumflex scapular artery to pass from the anterior axillary region to the posterior scapular region. The artery runs deep within this space, protected by the muscles that surround it.

Curving Around the Scapula

After passing through the triangular space, the circumflex scapular artery curves around the lateral border of the scapula, running toward the infraspinous fossa. The artery travels deep to the teres minor and teres major muscles, which it supplies. It then runs along the posterior surface of the scapula, reaching the infraspinatus muscle.

Infraspinatus Muscle: As it moves toward the scapula’s posterior surface, the artery provides critical blood supply to the infraspinatus muscle, a key muscle of the rotator cuff that is involved in external rotation of the shoulder.

Branches

The circumflex scapular artery gives rise to several smaller branches as it courses around the scapula. These branches supply various muscles and structures in the scapular region.

Muscular Branches

The circumflex scapular artery supplies muscular branches to several important muscles of the scapular region:

• Teres Minor: A rotator cuff muscle that is involved in the external rotation of the arm.
• Teres Major: A muscle that assists in adduction and internal rotation of the arm.
• Infraspinatus: Another rotator cuff muscle, which plays a key role in the external rotation of the shoulder.

These muscular branches provide the necessary blood flow for the proper functioning of these shoulder muscles.

Cutaneous Branches

The circumflex scapular artery also gives off cutaneous branches that supply the skin over the scapular region, contributing to the blood supply of the skin in the upper back and shoulder.

Anastomotic Branches

The circumflex scapular artery forms several important anastomoses (connections) with other arteries in the scapular region, contributing to a rich vascular network that ensures adequate blood supply to the shoulder area. These anastomoses include:

• Suprascapular Artery: The circumflex scapular artery anastomoses with the suprascapular artery, a branch of the thyrocervical trunk. This connection helps form a collateral circulation around the scapula.
• Dorsal Scapular Artery: It also forms anastomoses with the dorsal scapular artery, which supplies the medial border of the scapula and the rhomboid muscles. This connection reinforces the blood supply to the scapular muscles.

Termination

The circumflex scapular artery terminates by giving off smaller branches that distribute blood to the posterior structures of the scapula, including the skin, muscles, and bones. Its terminal branches supply the infraspinatus muscle and contribute to the scapular anastomosis. The artery ends by forming connections with other arteries in the shoulder region, which ensures collateral blood flow in the event of vascular compromise.

Relationship to Surrounding Structures

The circumflex scapular artery has important anatomical relationships with nearby structures, particularly muscles and bones in the scapular region.

• Teres Minor and Teres Major Muscles: As it travels through the triangular space, the artery is closely related to both the teres minor and teres major muscles. These muscles form part of the borders of the triangular space, through which the artery passes. The artery provides critical blood supply to both muscles.
• Long Head of the Triceps Brachii: The circumflex scapular artery passes near the long head of the triceps brachii muscle, which forms the lateral boundary of the triangular space. The artery does not directly supply the triceps, but its close proximity to this muscle is a key anatomical relationship.
• Scapula: The circumflex scapular artery curves around the lateral border of the scapula, supplying blood to the posterior surface of the bone and surrounding muscles. Its position near the scapula’s bony structures means that fractures or injuries to the scapula could potentially compromise the artery.

Variations

Anatomical variations in the circumflex scapular artery can occur. Some common variations include:

• Size Variation: In some individuals, the circumflex scapular artery may be larger or smaller than usual, depending on the blood supply provided by other arteries in the region.
• Anastomotic Patterns: The anastomoses between the circumflex scapular artery and other arteries (such as the suprascapular and dorsal scapular arteries) can vary in size and extent, leading to differences in the vascular network of the scapula.

Function

The circumflex scapular artery plays a crucial role in supplying blood to the scapular region and surrounding muscles. Its function ensures that the structures in the posterior aspect of the shoulder remain well-nourished and capable of performing their roles in shoulder movement and stability. Below is a detailed description of the functions of the circumflex scapular artery.

Blood Supply to the Muscles of the Posterior Shoulder

The circumflex scapular artery provides blood to several muscles that play important roles in shoulder movement and stabilization, including the teres major, teres minor, and infraspinatus muscles.

• Teres Minor: As a part of the rotator cuff group, the teres minor is responsible for the external rotation of the shoulder. The circumflex scapular artery supplies this muscle with oxygenated blood, allowing it to perform its role in stabilizing and rotating the shoulder joint.
• Teres Major: This muscle assists in adduction (moving the arm toward the body) and internal rotation of the shoulder. The circumflex scapular artery delivers blood to the teres major, enabling it to contribute to arm movements, particularly during actions like pulling or lifting.
• Infraspinatus: Another muscle of the rotator cuff, the infraspinatus muscle is essential for external rotation of the shoulder. The circumflex scapular artery ensures that the infraspinatus receives the oxygen and nutrients needed for its function, which is critical for shoulder joint stability and movement.

Blood Supply to the Scapula and Surrounding Bones

The circumflex scapular artery also provides essential blood flow to the scapula (shoulder blade), which serves as an anchor point for many muscles involved in shoulder movement.

• Scapula Nourishment: The artery runs along the lateral border of the scapula and supplies the periosteum (outer covering) of the scapula. This blood supply ensures that the bone remains healthy, strong, and capable of withstanding the forces exerted during shoulder movement.
• Bone Health and Repair: In cases of scapular injury or stress fractures, the circumflex scapular artery plays a crucial role in delivering the necessary nutrients and oxygen for bone repair and regeneration.

Blood Supply to the Posterior Shoulder Joint

The circumflex scapular artery contributes to the blood supply of the posterior aspect of the shoulder joint, including the soft tissues and capsule that support shoulder stability and movement.

• Joint Capsule Nourishment: The artery provides small branches that supply the posterior joint capsule of the shoulder. This is important for the health of the ligaments and synovial tissues that allow the shoulder joint to move smoothly while maintaining its stability.
• Support for Shoulder Mobility: By delivering blood to the joint structures, the circumflex scapular artery ensures that the shoulder joint remains flexible and mobile, which is necessary for the wide range of motions the shoulder is capable of, such as abduction, rotation, and flexion.

Contribution to Collateral Circulation

The circumflex scapular artery plays a critical role in the collateral circulation of the shoulder, which is essential for maintaining continuous blood flow to the region, even if one artery is compromised or blocked.

• Anastomosis with Suprascapular Artery: The circumflex scapular artery forms an important anastomosis with the suprascapular artery, a branch of the thyrocervical trunk. This connection provides an alternative pathway for blood to reach the muscles and structures of the scapula in case of arterial blockage or injury.
• Anastomosis with Dorsal Scapular Artery: The artery also forms an anastomosis with the dorsal scapular artery, which supplies the medial border of the scapula and the rhomboid muscles. This anastomosis reinforces the vascular network around the scapula and ensures adequate blood flow to the posterior shoulder.
• Collateral Flow During Movement: The collateral circulation formed by the circumflex scapular artery is especially important during shoulder movements that could compress one of the main arteries. This network ensures that the shoulder receives blood even during strenuous or complex arm movements.

Oxygen and Nutrient Delivery to Muscles and Skin

Like all arteries, the primary role of the circumflex scapular artery is to deliver oxygen and essential nutrients to the tissues it supplies. This is particularly important for the muscles and skin in the posterior shoulder region.

• Tissue Repair and Maintenance: The circumflex scapular artery ensures that the muscles and skin in the scapular region receive a continuous supply of oxygen and nutrients, which is essential for muscle function, tissue repair, and skin health. This blood supply is especially important after injury or strenuous use of the shoulder muscles, allowing for tissue regeneration and recovery.
• Support for Muscle Function: The blood supplied by the circumflex scapular artery allows the muscles of the scapular region, particularly the rotator cuff muscles, to function effectively. Proper oxygenation ensures that the muscles can contract efficiently and remain strong, preventing fatigue during prolonged or repetitive shoulder movements.

Cutaneous Blood Supply

The circumflex scapular artery also supplies blood to the skin and superficial tissues over the scapular region through its cutaneous branches.

• Skin Nourishment: By supplying blood to the skin over the scapula, the artery ensures that the skin remains healthy and nourished. This blood flow is essential for maintaining the elasticity and function of the skin, particularly in areas exposed to pressure or friction from clothing or movement.
• Healing of Skin Injuries: In cases of skin injury or trauma in the scapular region, the circumflex scapular artery provides the necessary blood supply to promote healing and tissue regeneration.

Support for Shoulder Movements and Stability

The circumflex scapular artery’s role in supplying the scapular muscles and joint structures is critical for supporting shoulder movements and stability.

• Rotator Cuff Function: By supplying blood to the teres minor and infraspinatus muscles, the circumflex scapular artery ensures that the rotator cuff muscles can effectively stabilize the shoulder joint during movement. This is essential for preventing dislocations and maintaining joint integrity during activities that require strength and precision, such as throwing or lifting.
• Shoulder Joint Stability: The blood supply to the posterior joint capsule and surrounding ligaments helps maintain the stability of the shoulder joint. This is especially important for maintaining the range of motion and protecting the joint from injury.

Clinical Significance

The circumflex scapular artery is clinically significant due to its role in supplying blood to the muscles and structures of the posterior shoulder and scapula. Key points of clinical relevance include:

• Scapular Fractures: The circumflex scapular artery runs along the lateral border of the scapula, making it vulnerable in cases of scapular fractures. Damage to this artery can result in compromised blood flow to the muscles and bones in the region, leading to delayed healing or avascular necrosis (bone death due to lack of blood supply).
• Surgical Considerations: The artery is important during shoulder surgeries, especially those involving the posterior approach, such as rotator cuff repairs or procedures on the scapula. Surgeons must avoid damaging the artery to prevent complications like bleeding or ischemia.
• Collateral Circulation: The circumflex scapular artery forms part of the scapular anastomosis, a network of arteries that ensures blood supply to the shoulder even if one vessel is blocked. This collateral circulation is essential during conditions like arterial occlusion or trauma, helping to maintain adequate blood flow.