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Superficial palmar arch

The superficial palmar arch (SPA) is the primary arterial arcade of the palm, located superficial to the flexor tendons and deep to the palmar aponeurosis. It serves as the main vascular channel supplying the palm and fingers, formed predominantly by the ulnar artery with contribution from the superficial palmar branch of the radial artery.

This arch plays a critical role in maintaining collateral blood flow to the hand, ensuring adequate perfusion during grasping, compression, or arterial obstruction. Anatomical variations are common, making the arch highly significant in hand surgery, flap design, and angiographic evaluation.

Synonyms

  • Superficial volar arch

  • Ulnar palmar arch

  • Arteria arcus palmaris superficialis

Origin, Course, and Formation

  • Origin: The superficial palmar arch is primarily formed by the terminal branch of the ulnar artery, which enters the palm superficial to the flexor retinaculum, lateral to the pisiform bone.

  • Formation: Completed on the lateral side by the superficial palmar branch of the radial artery (in about 80% of individuals).

  • Course:

    • Curves laterally across the palm at the level of the distal border of the fully extended thumb.

    • Lies superficial to the flexor tendons but deep to the palmar fascia and palmar aponeurosis.

    • Terminates by giving rise to the common palmar digital arteries.

Branches

  • Common palmar digital arteries: Usually three branches supplying the 2nd–4th web spaces, dividing into proper digital arteries.

  • Proper palmar digital arteries: Arise from common palmar digital arteries and supply adjacent sides of the fingers.

  • Palmar cutaneous branches: Supply skin and subcutaneous tissue of the palm.

  • Anastomotic connections: Communicate with the deep palmar arch and dorsal metacarpal arteries, forming a rich vascular network.

Relations

  • Superficially: Palmar aponeurosis and palmaris brevis muscle

  • Deeply: Flexor tendons of the fingers, lumbrical muscles, and digital branches of the median and ulnar arteries

  • Medially: Pisiform bone and hypothenar muscles

  • Laterally: Thenar muscles and radial artery contribution

Function

  • Main arterial supply to palm: Provides majority of blood flow to the superficial palmar tissues and digits.

  • Collateral circulation: Ensures continuous perfusion even if one contributing artery (ulnar or radial) is compromised.

  • Functional support: Supplies muscles, fascia, tendons, and skin of the palm and fingers.

  • Clinical relevance: Critical in maintaining finger perfusion; essential to assess before radial or ulnar artery cannulation or harvesting.

Clinical Significance

  • Allen’s test: Used to evaluate patency of the superficial and deep palmar arches before invasive arterial procedures.

  • Anatomical variations: Complete arch (typical) in ~80% of cases; incomplete arch in the rest can predispose to ischemia if one contributing artery is compromised.

  • Trauma and laceration: Common due to its superficial location in the palm; injuries may cause significant hemorrhage or digital ischemia.

  • Surgical relevance: Important during flap harvests, carpal tunnel surgery, and reconstructive hand procedures.

  • Embolic or atherosclerotic disease: May result in digital ischemia or ulceration in systemic vascular disorders.

MRI Appearance

  • T1-weighted images:

    • Vessel lumen: flow void (dark) due to fast arterial flow

    • Surrounding fat: bright, clearly outlining the arch’s course

    • Thrombosed or slow-flow segments: intermediate intraluminal signal

    • Muscle and fascia: intermediate-to-dark signal background

  • T2-weighted images:

    • Flowing blood: dark flow void

    • Arterial wall or thrombus: intermediate-to-bright signal, depending on composition and flow

    • Surrounding soft tissues: provide excellent contrast for identifying vascular course and pathology

  • STIR:

    • Normal vessel: dark flow void

    • Perivascular inflammation, hematoma, or edema: appear as bright hyperintense signals adjacent to the arch

  • Proton Density Fat-Saturated (PD FS):

    • Normal artery: dark linear structure

    • Pathologic areas (inflammation or mural thickening): bright perivascular signal

    • Excellent for delineating arterial walls in inflammatory or traumatic conditions

  • T1 Fat-Sat Post-Contrast:

    • Normal arch: brisk homogeneous enhancement throughout its curve

    • Stenosis or occlusion: focal non-enhancement or irregular narrowing

    • Aneurysm or pseudoaneurysm: focal rounded enhancement with flow void center

    • Perivascular enhancement: indicates active inflammation or infection

MRA (Magnetic Resonance Angiography) Appearance

  • Normal:

    • The superficial palmar arch appears as a smooth, curved enhancing vessel across the palm, connecting ulnar and radial arteries.

    • Clearly visualized on contrast-enhanced MRA or 3D time-of-flight (TOF) angiography.

  • Variations:

    • Complete arch: Continuous loop with consistent enhancement.

    • Incomplete arch: Unilateral filling with no visible communication between ulnar and radial systems.

  • Pathology:

    • Occlusion or stenosis: Segmental loss or tapering of signal.

    • Aneurysm: Focal outpouching with intense contrast pooling.

    • Collateralization: Serpiginous small vessels bridging interrupted segments in chronic ischemia.

CT Appearance

Non-Contrast CT:

  • The artery is not directly visualized unless calcified.

  • Soft-tissue density tracing the arch’s location between flexor tendons and palmar aponeurosis.

  • Chronic vascular calcification appears as fine curvilinear hyperdensities in arterial wall.

Post-Contrast CT (standard):

  • Superficial palmar arch appears as an enhancing curvilinear vessel crossing the palm.

  • Provides anatomical detail of arterial relationships to tendons and muscles.

  • Helps identify traumatic pseudoaneurysm, wall thickening, or extravasation.

CTA (CT Angiography) Appearance

  • Normal:

    • Shows a well-defined curved enhancing vessel across the palm, connecting ulnar and radial systems.

    • Optimal visualization during arterial phase with high-resolution thin-slice reconstruction.

  • Pathology:

    • Incomplete arch: Enhancement only from one side, lacking radial or ulnar communication.

    • Aneurysm: Saccular or fusiform dilation with intense contrast filling.

    • Occlusion or stenosis: Narrowing, cutoff, or delayed enhancement.

    • Collateral network: Small fine vessels visible bridging the arch in chronic obstruction.

MRI image

Superficial palmar arch coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Superficial palmar arch coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002

CT VRT 3D image

Superficial palmar arch of hand 3D VRT CT image