Ulnar Artery – Anatomy and Clinical Relevance

What is the Ulnar Artery?

The ulnar artery (Latin: Arteria ulnaris) is one of the two principal arteries of the forearm. It arises in the cubital fossa as one of the two terminal branches of the brachial artery and courses along the medial (ulnar) side of the forearm toward the wrist and hand. Together with the radial artery, it provides the main arterial supply to the hand.

Course and Anatomy

The ulnar artery originates at the level of the cubital fossa from the brachial artery. It initially passes deep beneath the flexor muscles of the forearm before becoming more superficial distally. It runs along the medial aspect of the forearm and enters the hand through the Guyon canal (ulnar canal) – a narrow passage at the wrist between the pisiform bone and the hook of the hamate bone.

Within the palm, the ulnar artery joins a branch of the radial artery to form the superficial palmar arch (arcus palmaris superficialis), which gives rise to the digital arteries supplying the fingers.

Branches and Supply Areas

Along its course, the ulnar artery gives off several important branches:

• Recurrent ulnar artery: supplies the elbow joint
• Common interosseous artery: divides into the anterior and posterior interosseous arteries, supplying the deep forearm muscles and the interosseous membrane
• Muscular branches (rami musculares): supply the forearm musculature
• Ulnar carpal branch: supplies the wrist joint
• Deep palmar branch: contributes to the deep palmar arch

Clinical Relevance

Pulse Assessment

The pulse of the ulnar artery can be palpated at the wrist on the medial (little finger) side. Although less commonly assessed than the radial pulse, it plays an important role in the Allen test, which evaluates the adequacy of arterial blood supply to the hand from both forearm arteries.

Allen Test

The Allen test is a simple bedside procedure in which both forearm arteries are compressed simultaneously and then released alternately. This allows the clinician to assess whether the hand receives adequate perfusion from each artery independently. It is especially important before any procedure involving arterial cannulation or harvest of one of the arteries as a graft.

Guyon Canal Syndrome

Guyon canal syndrome (ulnar tunnel syndrome) occurs due to compression of the ulnar nerve and ulnar artery as they pass through the narrow Guyon canal at the wrist. Typical symptoms include tingling, numbness, and weakness in the ring and little fingers, as well as impaired circulation to the hand.

Ulnar Artery Thrombosis and Hypothenar Hammer Syndrome

Hypothenar hammer syndrome is a rare condition caused by repetitive blunt trauma to the hypothenar region of the palm, leading to injury of the ulnar artery. This can result in thrombosis (clot formation) or aneurysm (focal dilation) of the artery, causing ischemia and digital artery occlusion with reduced blood supply to the fingers.

Ulnar Artery as a Bypass Graft

In selected cases in cardiac and vascular surgery, the ulnar artery may be harvested as a conduit for coronary or peripheral revascularization. A prerequisite is always a negative Allen test confirming adequate collateral perfusion of the hand through the radial artery alone.

Diagnostic Methods

Several diagnostic tools are available to evaluate the ulnar artery:

• Doppler ultrasound: assesses blood flow velocity and detects stenoses or occlusions
• Duplex ultrasonography: combines B-mode imaging with Doppler flow analysis for detailed assessment
• Angiography: contrast-based imaging to visualize vessel anatomy and pathology
• MR angiography: non-invasive magnetic resonance imaging of the vascular anatomy
• Allen test: clinical assessment of hand perfusion

References

1. Drake R.L., Vogl A.W., Mitchell A.W.M.: Gray's Anatomy for Students. 4th edition. Elsevier, Philadelphia 2019.
2. Standring S. (ed.): Gray's Anatomy – The Anatomical Basis of Clinical Practice. 42nd edition. Elsevier, London 2020.
3. Moore K.L., Dalley A.F., Agur A.M.R.: Clinically Oriented Anatomy. 8th edition. Wolters Kluwer, Philadelphia 2018.