Radial Collateral Artery: Anatomy, Course, Function, Imaging

Topic

Radial collateral artery

The radial collateral artery (RCA) is a major terminal branch of the profunda brachii (deep brachial) artery in the arm. It descends along the lateral aspect of the humerus, accompanying the radial nerve through the radial groove, and contributes to the lateral arterial anastomosis around the elbow joint.

It primarily supplies the triceps brachii, brachioradialis, and anconeus muscles, and anastomoses with the radial recurrent artery anterior to the lateral epicondyle, forming an important component of the periarticular elbow collateral network.

Synonyms

Superior lateral collateral artery
Lateral branch of profunda brachii artery
Radial collateral branch of the deep brachial artery

Origin, Course, and Termination

Origin: Arises from the profunda brachii artery, a branch of the brachial artery, typically in the posterior compartment of the arm near the humeral shaft.
Course:
- Descends obliquely between the brachialis and brachioradialis muscles on the lateral aspect of the arm.
- Runs anterior to the lateral intermuscular septum.
- Approaches the lateral epicondyle of the humerus, where it becomes more superficial.
Termination:
- Divides into several small branches that anastomose with the radial recurrent artery anterior to the lateral epicondyle and with the interosseous recurrent artery posteriorly.

Relations

Anteriorly: Brachialis and brachioradialis muscles
Posteriorly: Lateral head of triceps brachii and the humerus
Laterally: Lateral intermuscular septum
Medially: Radial nerve (in upper arm)
Inferiorly: Lateral epicondyle of the humerus and elbow joint capsule

Branches

Muscular branches: Supply brachioradialis, triceps brachii (lateral head), and anconeus
Articular branches: Supply the lateral aspect of the elbow joint
Anastomotic branches: Join the radial recurrent artery anteriorly and the interosseous recurrent artery posteriorly, forming part of the elbow anastomosis

Function

Collateral circulation: Provides a vital anastomotic connection between the profunda brachii and radial recurrent arteries around the elbow
Muscular supply: Nourishes extensor and flexor muscles of the lateral arm and elbow
Vascular redundancy: Ensures continuous blood flow during flexion-extension when brachial artery compression occurs
Surgical importance: Key artery in flap surgeries and vascular bypass grafts around the elbow

Clinical Significance

Collateral pathway: Critical in maintaining distal limb perfusion during brachial artery occlusion or trauma
Injury risk: May be damaged during lateral epicondyle fractures or surgical exposure of the humerus
Aneurysm or pseudoaneurysm: Rare but possible following penetrating trauma or iatrogenic injury
Surgical relevance: Important to preserve during posterolateral approaches to the distal humerus and triceps dissection
Vascular imaging relevance: Evaluated in cases of upper limb ischemia, arterial repair, or collateral mapping before surgery

MRI Appearance

T1-weighted images:
- Normal artery: dark flow void due to rapid flow.
- Perivascular fat: bright, enhancing visualization.
- Thrombosis or sluggish flow: intermediate intraluminal signal.
- Muscles supplied (triceps, brachioradialis) show intermediate muscle signal.
T2-weighted images:
- Flowing blood: dark signal (flow void).
- Vessel wall thickening or thrombus: intermediate-to-bright signal depending on chronicity.
- Surrounding soft-tissue edema: bright hyperintensity if inflammation or trauma present.
STIR:
- Normal artery: dark flow void.
- Pathology: bright perivascular signal in cases of hematoma, inflammation, or infection.
Proton Density Fat-Saturated (PD FS):
- Artery: dark flow void.
- Thrombosed or inflamed artery: wall thickening with bright rim or perivascular enhancement.
T1 Fat-Sat Post-Contrast:
- Normal: brisk homogeneous enhancement of the lumen.
- Stenosis or occlusion: segmental non-enhancing areas with collateral filling.
- Vasculitis or adventitial inflammation: circumferential vessel wall enhancement.

MRA (Magnetic Resonance Angiography) Appearance

Normal: The radial collateral artery appears as a slender, enhancing vessel descending laterally from the profunda brachii and joining the radial recurrent artery near the lateral epicondyle.
Technique: Best visualized using contrast-enhanced 3D MRA or time-of-flight (TOF) angiography with high-resolution gradient sequences.
Pathology:
- Occlusion or stenosis: loss of signal continuity or reduced lumen caliber.
- Aneurysm: localized outpouching with intense contrast enhancement.
- Collateral pathways: visualized as serpiginous enhancing channels around the lateral elbow in chronic occlusive disease.

CT Appearance

Non-Contrast CT:

Vessel lumen not directly visualized unless calcified.
Chronic vascular calcification appears as curvilinear high-attenuation lines on lateral humeral aspect.
Surrounding muscular and bony landmarks aid localization near the lateral epicondyle.

Post-Contrast CT (standard):

Radial collateral artery enhances as a fine tubular structure ascending along the lateral humerus.
Easily differentiated from veins due to earlier and denser enhancement.
Pathology: aneurysm, focal stenosis, or wall thickening detectable.

CTA (CT Angiography) Appearance

Normal:
- Depicted as a small, contrast-filled vessel branching from the profunda brachii artery and descending anterior to the lateral epicondyle.
- Seen best on arterial-phase CTA with thin-slice 3D reconstruction.
Pathology:
- Occlusion: abrupt cutoff or tapering of contrast column.
- Stenosis: segmental narrowing or irregular vessel wall.
- Aneurysm: focal contrast-filled dilation with smooth or irregular margins.
- Collateralization: multiple fine tortuous enhancing channels near the lateral epicondyle.
Utility: CTA provides precise mapping of collateral vessels and helps assess arterial continuity in trauma, occlusion, or surgical planning.