Posterior Interosseous Artery: Anatomy, Course, Function, Imaging

Topic

Posterior interosseous artery

The posterior interosseous artery (PIA) is a major branch of the common interosseous artery, which arises from the ulnar artery in the proximal forearm. It passes posteriorly through the interosseous membrane to enter the posterior compartment of the forearm, supplying the extensor muscles, interosseous membrane, and the radiocarpal joint.

It plays a key role in the dorsal arterial network of the wrist, and through its recurrent branch, it participates in the elbow anastomosis. The artery provides rich collateral circulation between the radial, ulnar, and anterior interosseous arteries, ensuring vascular redundancy to the posterior forearm.

Synonyms

Dorsal interosseous artery
Posterior branch of the interosseous artery

Origin, Course, and Termination

Origin: Arises from the common interosseous artery, a short trunk from the ulnar artery, just distal to the cubital fossa.
Course:

Passes posteriorly above the upper margin of the interosseous membrane, between the radius and ulna, reaching the posterior compartment.
Descends between the superficial and deep layers of the extensor muscles, usually accompanied by the posterior interosseous nerve.
Proceeds distally toward the wrist, giving off multiple muscular and anastomotic branches.
Termination:
Ends in the dorsal carpal arch, where it anastomoses with the dorsal carpal branch of the radial artery and the anterior interosseous artery.

Relations

Anteriorly: Interosseous membrane (at its origin)
Posteriorly: Extensor muscles of the forearm
Laterally: Radius and posterior interosseous nerve
Medially: Ulna and extensor carpi ulnaris
Distally: Dorsal aspect of wrist and carpal bones

Branches

Interosseous recurrent artery: Ascends toward the lateral epicondyle, participating in the elbow anastomosis with the middle collateral artery.
Muscular branches: Supply the extensor carpi ulnaris, extensor digitorum, extensor pollicis longus, and other dorsal forearm muscles.
Articular branches: Supply the radiocarpal and midcarpal joints.
Anastomotic branches: Connect with the anterior interosseous and dorsal carpal arteries.

Function

Arterial supply: Provides blood to posterior compartment muscles, interosseous membrane, and elbow and wrist joints.
Collateral circulation: Important component of dorsal forearm collateral flow during arterial occlusion or compression.
Anastomotic network: Contributes to both elbow and dorsal wrist arterial arches, maintaining continuous perfusion.

Clinical Significance

Collateral importance: Preserves distal blood flow in ulnar or radial artery occlusion.
Vascular trauma: May be damaged in posterior forearm lacerations or fractures.
Surgical relevance: Preserved or used as a landmark during free flap harvests (posterior interosseous flap).
Aneurysm or thrombosis: Rare but may compress the posterior interosseous nerve, causing weakness in finger extension.
Imaging role: MRI, MRA, and CTA assess patency, anastomosis, and vascular integrity, especially in trauma and reconstructive surgery planning.

MRI Appearance

T1-weighted images:

Normal artery: flow void (dark linear signal) due to rapid blood flow
Perivascular fat: bright, enhancing the artery’s outline
Thrombosed segment: intermediate signal intensity replacing normal flow void

T2-weighted images:

Normal artery: dark (flow void) surrounded by intermediate-signal muscle
Thrombus or aneurysm: bright to intermediate signal, depending on blood stasis or wall thickening
Inflammatory changes: hyperintense perivascular signal

STIR:

Normal artery: dark flow void
Inflammation, edema, or hematoma: bright hyperintense halo surrounding the vessel

Proton Density Fat-Saturated (PD FS):

Normal: dark linear vessel
Pathologic: bright wall or luminal signal in thrombosis or vasculitis

T1 Fat-Sat Post-Contrast:

Normal: brisk homogeneous enhancement of the artery lumen
Occlusion: non-enhancing segment with collateral channels visible
Vasculitis: concentric wall enhancement

MRA (Magnetic Resonance Angiography) Appearance

Normal: Visualized as a small, enhancing longitudinal vessel running between the radius and ulna posteriorly.
Techniques: Best demonstrated with contrast-enhanced 3D MRA or time-of-flight (TOF) angiography.
Pathology:
- Stenosis or occlusion: segmental flow loss or narrowing.
- Aneurysm: localized focal dilation with smooth contrast filling.
- Collateral formation: serpiginous enhancement in chronic occlusion.
- Flap harvest planning: MRA maps arterial caliber and perforators for surgical use.

CT Appearance

Non-Contrast CT:

Artery not directly seen unless calcified.
Surrounding soft tissues and interosseous membrane visible for orientation.
Chronic vascular calcification: fine linear hyperdensity along artery wall.

Post-Contrast CT (standard):

Artery appears as an enhancing tubular structure between the radius and ulna, posterior to the interosseous membrane.
Detects mural thickening, aneurysm, or thrombosed segments.
Provides clear differentiation from adjacent veins and nerve structures.

CTA (CT Angiography) Appearance

Normal:
- Seen as a thin, well-enhancing artery running posteriorly from the common interosseous trunk, descending with the posterior interosseous nerve.
- Clearly delineated on arterial-phase CTA with thin-slice or multiplanar reconstruction.
Pathology:
- Stenosis or occlusion: abrupt tapering or cutoff of contrast flow.
- Aneurysm: focal saccular or fusiform contrast-filled dilation.
- Collateral flow: fine enhancing vessels joining the interosseous recurrent and dorsal carpal arches.
- Surgical planning: CTA defines course, caliber, and perforator branches for flap design.

MRI image

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