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Posterior circumflex humeral artery

The posterior circumflex humeral artery (PCHA) is a major branch of the third part of the axillary artery that supplies the deltoid region, shoulder joint, and proximal humerus. It is one of the two circumflex humeral arteries (the other being the anterior circumflex humeral artery) and plays a vital role in the vascular supply of the shoulder girdle.

It passes posteriorly through the quadrangular space with the axillary nerve, wrapping around the surgical neck of the humerus, and forms an anastomotic network with the anterior circumflex humeral artery, thoracoacromial, and subscapular arteries.

Synonyms

  • PCHA

  • Posterior humeral circumflex artery

Origin, Course, and Termination

  • Origin: Arises from the third part of the axillary artery, distal to the subscapular artery.

  • Course:

    • Passes posteriorly through the quadrangular space, accompanied by the axillary nerve.

    • Curves around the posterior aspect of the surgical neck of the humerus deep to the deltoid muscle.

    • Travels in close relation to the humeral head and glenohumeral joint capsule.

  • Termination: Divides into branches supplying the deltoid, teres major, teres minor, triceps brachii (long head), and the shoulder joint capsule, before anastomosing with the anterior circumflex humeral artery.

Branches

  • Muscular branches: To the deltoid, teres minor, and triceps (long head).

  • Articular branches: To the shoulder joint and capsule.

  • Cutaneous branches: To overlying skin of the posterior deltoid region.

  • Anastomotic branches: With anterior circumflex humeral and subscapular arteries around the shoulder.

Relations

  • Anteriorly: Subscapularis and surgical neck of the humerus.

  • Posteriorly: Deltoid muscle.

  • Superiorly: Teres minor.

  • Inferiorly: Teres major.

  • Medially: Long head of triceps brachii and axillary artery.

  • Laterally: Humeral head and deltoid muscle.

Function

  • Vascular supply: Provides major arterial supply to the deltoid, teres minor, triceps (long head), and the posterior capsule of the shoulder joint.

  • Anastomotic role: Forms part of the scapular and humeral arterial anastomosis, ensuring collateral circulation during arm movement or axillary compression.

  • Clinical landmark: Serves as a key structure within the quadrangular space used for surgical and radiologic orientation.

Clinical Significance

  • Quadrangular Space Syndrome: Compression of the artery (and axillary nerve) within the quadrangular space may lead to ischemia of the deltoid and paresthesia of the lateral shoulder.

  • Aneurysm or pseudoaneurysm: May occur post-trauma or repetitive overhead activity, presenting as a pulsatile mass in the posterior shoulder.

  • Fractures of the surgical neck of the humerus: May compromise arterial flow, leading to avascular necrosis of humeral head.

  • Iatrogenic injury: Possible during deltoid or rotator cuff surgery.

  • Imaging relevance: Important for evaluating vascular injury, aneurysm, dissection, and postoperative vascular flow.

MRI Appearance

  • T1-weighted images:

    • Arterial lumen: Flow void (dark signal) due to rapid blood flow.

    • Wall: Thin, low-signal outline if visualized.

    • Adjacent fat planes: Bright, aiding delineation of the artery.

    • Thrombosed or slow-flow regions: May appear intermediate-to-bright depending on flow velocity.

  • T2-weighted images:

    • Patent lumen: Flow void (dark) on standard spin-echo sequences.

    • Surrounding fat: Bright, allowing visualization of arterial course.

    • Thrombus or mural hematoma: Hyperintense if acute; becomes intermediate in chronic phase.

    • Edematous changes in nearby muscles (e.g., deltoid, teres minor) appear bright hyperintense in vascular compression or injury.

  • STIR:

    • Arterial lumen: Low to absent signal (flow void).

    • Pathology: Perivascular inflammation or hematoma shows bright hyperintense signal.

    • Useful for detecting soft-tissue edema or vascular entrapment in quadrangular space syndrome.

  • Proton Density Fat-Saturated (PD FS):

    • Artery: Dark signal due to flow void.

    • Surrounding inflammation or edema: Bright hyperintense region adjacent to vessel.

    • Highlights perivascular soft-tissue abnormalities or extravasated blood.

  • T1 Fat-Sat Post-Contrast (MR Angiography):

    • Arterial lumen: Bright enhancement, delineating full course and branches.

    • Aneurysms: Focal saccular or fusiform bright outpouching.

    • Occlusion or thrombosis: Segmental loss of enhancement.

    • Useful for assessing post-traumatic vascular integrity and surgical planning.

CT Appearance

Non-Contrast CT:

  • Artery seen as a tubular soft-tissue density structure posterior to humeral head.

  • Surrounding fat planes help identify its course through the quadrangular space.

  • Calcified plaques (rare) or mural thickening may be visualized.

  • Not optimal for flow assessment but excellent for detecting post-traumatic hematoma or aneurysmal calcification.

Post-Contrast CT (CT Angiography):

  • Lumen: Brightly enhancing tubular structure curving posterior to humeral neck.

  • Anastomoses: Clearly seen with anterior circumflex humeral and subscapular arteries.

  • Aneurysm or pseudoaneurysm: Focal contrast-filled outpouching.

  • Occlusion: Absence of contrast filling; may show adjacent soft-tissue swelling or collateral flow.

  • Quadrangular space compression: May demonstrate vessel narrowing or displacement.

  • Excellent for trauma evaluation, aneurysm detection, and surgical mapping.

CT VRT 3D image

Posterior circumflex humeral artery 3d vrt image

MRI image

Posterior circumflex humeral artery axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

Posterior circumflex humeral artery ct axial 1

CT image

Posterior circumflex humeral artery ct axial