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Circumflex subscapular artery

The circumflex subscapular artery is a large branch of the subscapular artery, arising near the lateral border of the scapula. It plays a key role in the scapular anastomosis, connecting the subclavian and axillary arterial systems. It supplies the subscapularis, teres major, teres minor, and infraspinatus muscles, and contributes to collateral circulation around the shoulder joint.

This vessel is of great surgical and radiologic importance, especially in axillary dissection, flap surgeries, and shoulder trauma imaging.

Synonyms

  • Subscapular circumflex artery

  • Posterior scapular circumflex branch

Origin, Course, and Termination

  • Origin: Arises from the subscapular artery, which is the largest branch of the third part of the axillary artery.

  • Course:

    • Runs backward and laterally along the inferior border of the subscapularis muscle.

    • Passes through the triangular space (bounded by the teres major, teres minor, and long head of triceps).

    • Curves around the lateral border of the scapula to reach the dorsal aspect of the scapula.

  • Termination: Divides into two main branches — the scapular branch and the descending branch — which participate in the scapular anastomosis.

Branches

  • Scapular branch:

    • Curves around the lateral border of the scapula.

    • Supplies the infraspinatus and teres minor muscles.

    • Anastomoses with the suprascapular and dorsal scapular arteries on the posterior surface of the scapula.

  • Descending branch:

    • Descends along the axillary border of the scapula.

    • Supplies teres major, latissimus dorsi, and subscapularis.

    • Communicates with branches of the thoracodorsal and posterior circumflex humeral arteries.

Relations

  • Anteriorly: Subscapularis muscle and the posterior wall of the axilla.

  • Posteriorly: Teres major, teres minor, and long head of the triceps brachii.

  • Superiorly: Axillary artery and vein (proximal segment).

  • Inferiorly: Latissimus dorsi and thoracodorsal artery.

  • Lateral boundary: Triangular space through which it passes to the dorsal scapular region.

Function

  • Arterial supply: Provides oxygenated blood to the subscapularis, teres major, teres minor, infraspinatus, and adjacent shoulder capsule.

  • Scapular anastomosis: Ensures collateral circulation between subclavian and axillary systems, maintaining perfusion during proximal arterial obstruction.

  • Muscle perfusion: Vital contributor to posterior scapular and axillary musculature blood flow.

Clinical Significance

  • Surgical relevance:

    • Important landmark during axillary lymph node dissection and posterior shoulder surgeries.

    • Serves as the vascular pedicle in latissimus dorsi and scapular free flaps.

  • Trauma: May be injured in scapular or axillary fractures and dislocations, causing posterior shoulder hematoma.

  • Aneurysm: Rare, but can cause a pulsatile mass in the posterior axillary region.

  • Imaging importance: Key artery in shoulder MR angiography, CT angiography, and vascular mapping for reconstructive surgery.

MRI Appearance

  • T1-weighted images:

    • Arterial lumen: Flow void (black tubular signal) due to high-velocity blood flow.

    • Arterial wall: Thin, low-to-intermediate signal rim.

    • Surrounding muscles (subscapularis, teres): Intermediate signal intensity.

    • Fat planes: Bright, delineating the vessel course.

  • T2-weighted images:

    • Arterial lumen: Flow void or mild hyperintensity if slow flow or turbulence is present.

    • Wall and perivascular tissue: Intermediate-to-bright signal in inflammation or compression.

    • Muscles: Intermediate-to-low signal; distinguishable from bright perivascular fat.

  • STIR:

    • Normal artery: Low-to-dark signal (flow void).

    • Pathologic findings: Bright hyperintensity in surrounding soft tissues in cases of edema, hematoma, or vascular inflammation.

    • Excellent for detecting post-traumatic perivascular edema or entrapment.

  • Proton Density Fat-Saturated (PD FS):

    • Artery: Flow void (dark).

    • Pathology: Bright perivascular edema or hematoma signal surrounding the vessel.

    • Useful for postoperative evaluation and vascular injury detection.

  • T1 Fat-Sat Post-Contrast:

    • Artery: Strong, uniform enhancement of lumen following contrast injection.

    • Surrounding tissues: Highlight enhancement in inflammatory or neoplastic invasion.

    • Aneurysm or pseudoaneurysm: Well-defined, rounded, enhancing structure along expected course.

    • Vascular flaps: Enhancement confirms patency and adequate perfusion.

CT Appearance

Non-Contrast CT:

  • Artery: Linear or tubular soft-tissue density structure along lateral scapular border.

  • Surrounding fat: Clearly demarcates artery in axillary and scapular regions.

  • Calcification: May be seen in chronic vascular disease or healed aneurysmal wall.

  • Fractures or mass effect: Easily appreciated relative to artery’s position.

Post-Contrast CT (CT Angiography):

  • Artery: Brightly opacified with contrast, clearly visualized along its course from subscapular artery to posterior scapula.

  • Branches: Scapular and descending branches easily traced to their muscular territories.

  • Collateral network: Demonstrates connections with suprascapular, dorsal scapular, and posterior circumflex humeral arteries.

  • Pathology: Detects stenosis, occlusion, dissection, or aneurysm.

  • Surgical planning: Defines vascular anatomy for scapular and latissimus dorsi flaps.

MRI images

Circumflex subscapular artery axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT images

Circumflex subscapular artery ct axial image