Radialis Indicis Artery: Anatomy, Course, Function, Imaging

Topic

Radialis indicis artery

The radialis indicis artery is a slender, constant branch of the radial artery that supplies the lateral (radial) aspect of the index finger. It arises in the palm from the radial artery near the origin of the princeps pollicis artery, typically just as the radial artery curves medially to form the deep palmar arch.

This artery is clinically important in digital perfusion, microvascular flap surgeries, and angiographic evaluation of hand circulation. Together with the ulnar digital artery of the index finger, it provides rich collateral supply to the digit and participates in the fine vascular arcade at the fingertip.

Synonyms

Arteria radialis indicis
Lateral digital artery of the index finger
Radial digital branch of index finger

Origin, Course, and Termination

Origin: From the radial artery or occasionally from the princeps pollicis artery in the palm, near the first intermetacarpal space.
Course:
- Runs distally along the lateral side of the index finger, usually accompanied by a pair of digital veins.
- Lies deep to the flexor tendons and beneath the fibrous digital sheath, continuing toward the distal phalanx.
- Along its course, it gives off small cutaneous and periosteal branches to the finger.
Termination:
- Forms a vascular arcade with the ulnar digital artery of the same finger near the fingertip pulp and nail bed region.

Relations

Anteriorly: Fibrous digital sheath and skin of the radial side of the index finger
Posteriorly: Shaft of proximal and middle phalanges and interosseous tissue
Medially: Flexor digitorum profundus tendon
Laterally: Princeps pollicis artery (proximally) and first dorsal interosseous muscle
Distally: Nail bed and pulp of the index finger

Branches

Periosteal branches: To the phalangeal bones and periosteum
Cutaneous branches: To lateral skin of the index finger
Articular twigs: To digital joints, especially the proximal and distal interphalangeal joints
Terminal arcade: Anastomoses with the ulnar digital artery of the index finger

Function

Digital perfusion: Supplies the radial aspect of the index finger, including the pulp, periosteum, nail bed, and distal phalanx
Collateral network: Contributes to the fingertip anastomotic arcade ensuring uniform capillary refill
Surgical significance: Essential for finger flap planning, replantation surgery, and angiographic mapping
Physiological role: Maintains thermoregulation and tactile tissue oxygenation at the fingertip

Clinical Significance

Trauma: Laceration can cause ischemia or digital necrosis if collateral flow is inadequate
Atherosclerosis and embolism: May lead to localized ischemic changes or ulceration of the fingertip
Reconstructive surgery: Used as a vascular pedicle for radialis indicis flaps in hand reconstruction
Vascular studies: Evaluated in angiography, MRA, or CTA for assessing digital perfusion or vascular injury
Variation: May arise from the superficial palmar branch of the radial artery or share a common trunk with the princeps pollicis artery

MRI Appearance

T1-weighted images:
- Artery appears as a dark flow void due to rapid blood flow.
- Perivascular fat: bright, outlining the vessel wall clearly.
- Thrombosis or slow flow: may show intermediate intraluminal signal.
T2-weighted images:
- Normal flow: dark signal (flow void).
- Vessel wall: thin low-signal rim.
- Thrombosed segment: intermediate-to-bright signal depending on clot age.
- Adjacent soft tissue and tendons clearly delineated.
STIR:
- Normal: dark linear flow void.
- Inflammation, trauma, or hematoma: appear bright hyperintense in perivascular soft tissues.
Proton Density Fat-Saturated (PD FS):
- Normal artery: dark signal; wall appears thin and regular.
- Abnormal: hyperintense thickened wall or perivascular signal in vasculitis or contusion.
T1 Fat-Sat Post-Contrast:
- Normal lumen: strong homogeneous enhancement.
- Stenosis: focal or segmental non-enhancing gap.
- Aneurysm or pseudoaneurysm: rounded or fusiform area of intense enhancement.
- Vasculitis: concentric mural enhancement with surrounding soft-tissue reaction.

MRA (Magnetic Resonance Angiography) Appearance

Normal: The radialis indicis artery appears as a slender enhancing vessel arising from the radial artery near the base of the thumb and running along the radial border of the index finger.
Best technique: Contrast-enhanced MRA or 3D Time-of-Flight (TOF) sequences with high spatial resolution.
Findings:
- Normal patency: Continuous bright signal without interruption.
- Stenosis: Segmental signal drop or narrowing.
- Occlusion: Abrupt cutoff with absent distal enhancement.
- Collateral flow: Fine tortuous reconstitution from adjacent digital arteries.

CT Appearance

Non-Contrast CT:

Artery not directly visible without contrast.
Vascular calcifications (if present) appear as fine curvilinear high-density lines along arterial course.
Bony landmarks (phalanges and metacarpal heads) aid in localization.

Post-Contrast CT (standard):

Artery enhances as a small contrast-filled tubular structure on the lateral side of the index finger.
Differentiated from veins by timing and enhancement pattern.
Detects arterial wall thickening, pseudoaneurysm, or traumatic disruption.

CTA (CT Angiography) Appearance

Normal:
- Visualized as a fine, enhancing artery branching from the radial artery near the base of the thumb, coursing distally along the radial aspect of the index finger.
- Best seen in arterial-phase thin-slice reconstructions or volume-rendered 3D images.
Pathology:
- Stenosis: Focal narrowing or luminal irregularity.
- Occlusion: Abrupt termination with distal reconstitution.
- Aneurysm or pseudoaneurysm: Focal outpouching with contrast filling.
- Traumatic injury: Extravasation of contrast or vessel discontinuity.
- Collateral patterns: Seen as fine tortuous reconstitution via adjacent digital arteries.