Deep Palmar Arch: Anatomy, Course, Function, Imaging

Topic

Deep palmar arch

The deep palmar arch is the principal arterial arch of the palm, formed primarily by the terminal branch of the radial artery, with contribution from the deep branch of the ulnar artery. It lies deep in the palm, closer to the metacarpal bases, and supplies blood to the metacarpal bones, interossei, and deep palmar muscles. It plays a vital role in maintaining collateral circulation within the hand, ensuring continuous perfusion even when one of the main arteries (radial or ulnar) is compromised.

Synonyms

Profunda palmar arch
Deep volar arch
Arteria arcus palmaris profundus

Origin, Course, and Termination

Origin: Formed mainly by the continuation of the radial artery after it passes between the two heads of the first dorsal interosseous muscle. It is completed medially by the deep branch of the ulnar artery.
Course: The arch curves medially across the bases of the metacarpal bones, approximately 1 cm proximal to the superficial palmar arch. It lies deep to the flexor tendons and lumbrical muscles, but superficial to the interossei.
Termination: Gives off three palmar metacarpal arteries, which run distally to join the common palmar digital arteries from the superficial palmar arch.

Relations

Anteriorly: Oblique head of adductor pollicis, flexor tendons, and lumbrical origins
Posteriorly: Interosseous muscles and metacarpal bones
Laterally: Radial artery and first dorsal interosseous muscle
Medially: Deep branch of the ulnar artery and hypothenar muscles

Branches

Palmar metacarpal arteries: Three slender arteries that join the superficial arch’s common digital arteries
Perforating branches: Communicate with the dorsal metacarpal arteries
Recurrent branches: Supply the adductor pollicis and interosseous muscles
Vascular twigs: To the deep palmar musculature and periosteum of metacarpal bases

Function

Main arterial supply to deep palm: Provides oxygenated blood to deep structures including interossei, adductor pollicis, and metacarpal bones
Collateral circulation: Ensures continuous perfusion of the hand by connecting with the superficial palmar arch and dorsal carpal network
Muscle and bone nutrition: Maintains metabolic support for deep palmar tissues and joints
Pressure regulation: Balances blood flow between superficial and deep arterial systems of the palm

Clinical Significance

Collateral flow assessment: Integrity of the arch is essential before radial artery cannulation or harvesting (Allen’s test, Doppler, or MRA)
Arterial injury: Trauma or iatrogenic damage can lead to ischemia of deep palmar structures
Aneurysm or pseudoaneurysm: Rare but can result from repetitive mechanical stress or invasive procedures
Arteriovenous malformations: May involve the arch or its branches
Surgical relevance: Important in flap design, vascular grafts, and reconstructive microsurgery

MRI Appearance

T1-weighted images:

Arterial lumen appears as a dark flow void due to fast-flowing blood
Perivascular fat and soft tissue: bright, providing natural contrast
Thrombosed or slow-flowing vessel: intermediate intraluminal signal

T2-weighted images:

Flowing blood: dark (flow void)
Arterial wall thickening or thrombosis: intermediate-to-bright depending on stage
Perivascular edema or inflammation: hyperintense signal surrounding the vessel

STIR:

Normal arch: dark flow void
Pathology (inflammation or hematoma): bright hyperintense perivascular signal
Useful for detecting vascular injury, post-traumatic edema, or inflammatory changes

Proton Density Fat-Saturated (PD FS):

Artery: low signal (flow void)
Wall inflammation or thrombus: bright intraluminal or mural signal
Accentuates perivascular soft-tissue changes

T1 Fat-Sat Post-Contrast:

Normal: uniform strong enhancement of the arch and branches
Stenosis or occlusion: segmental non-enhancement
Aneurysm or vascular malformation: focal intense enhancement or contrast pooling

MRA (Magnetic Resonance Angiography) Appearance

Normal: The deep palmar arch appears as a curved enhancing vessel across the bases of the metacarpals, primarily fed by the radial artery.
Technique: Best visualized on 3D time-of-flight (TOF) or contrast-enhanced MRA sequences with high spatial resolution.
Pathology:
- Occlusion: Focal or segmental loss of signal within the arch
- Aneurysm: Localized bulging or saccular enhancement
- Collateral flow: Multiple small enhancing channels if radial or ulnar flow is reduced
- Anatomic variants: Incomplete arches or dominance of one contributing artery

CT Appearance

Non-Contrast CT:

Artery not distinctly visible unless calcified
Arterial calcifications appear as fine curvilinear densities at the base of metacarpals
Bony landmarks and muscular planes provide orientation

Post-Contrast CT (Standard):

Deep palmar arch visualized as an enhancing curvilinear vessel beneath flexor tendons
Differentiates the deep arch from the superficial palmar arch based on depth and location
Detects small aneurysms, thrombosis, or perivascular soft-tissue changes

CTA (CT Angiography) Appearance

Normal: Well-opacified, smooth, curving arterial arch extending from the radial artery laterally to the ulnar contribution medially
Technique: Arterial-phase CTA with thin-section multiplanar and volume-rendered reconstructions provides optimal visualization
Pathology:
- Stenosis or occlusion: Narrowing or abrupt cutoff of contrast filling
- Aneurysm: Focal saccular or fusiform dilation
- Collateral circulation: Numerous fine enhancing channels when one inflow artery is compromised
- Variant anatomy: Partial arch or dominance by a single artery identified by asymmetric opacification