Week 4 · the limb bud
The arm is just a bud; the hand has no shape yet. A single vessel, the brachial artery, enters the bud.
The mechanism
From one vessel, to three, to just two
In the fourth week of embryonic development, the arm is a small bud, and the hand doesn't have a hand's shape yet. The brachial artery, coming down from the shoulder, branches for the first time in the fifth week: one of those branches, the median artery, feeds the forming hand at this stage. The radial and ulnar arteries develop alongside it and gradually take over. By the eighth week, in most embryos, the median artery regresses. In the rest, it stays.
Week 4 · the limb bud
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Adult anatomy
Where the artery that never disappeared ends up
Of the 43 limbs in 100 where the median artery stays, most have the antebrachial type: in 28 of 100, the vessel ends somewhere in the forearm, before the wrist. In 15 of 100, though, it crosses the carpal tunnel and reaches the palm, where it can become the sole blood supply of a finger.
57 · no persistent median artery
28 · antebrachial type
15 · palmar type
The usual route · 57 of 100
The hand is fed by the radial and ulnar arteries. The median artery no longer exists: it regressed during embryonic development.
What the measurements show
The vessel leaves a mark on the arteries around it
The researchers recorded whether the median artery was present and measured the diameter of the vessels around it. One result clears the usual bar for statistical significance; the other stays a trend.
The authors think the explanation lies in the shared route: a persistent median artery most often branches off the ulnar artery itself, or off a close relative of it, the common interosseous artery. An extra vessel on the same route could draw more blood through the whole ulnar system: it remains a plausible hypothesis, unconfirmed so far.
A secondary finding, unrelated to the median artery
Your left arm barely predicts your right
The cadavers also gave a comparison unrelated to the median artery: how similar the radial and ulnar arteries of the same person are, from one arm to the other. The answer surprised even the study's own authors.
In other words, if you know how thick someone's radial artery is on one arm, you can barely guess how thick it is on their other arm. Each limb seems to build its own map of blood vessels, largely on its own.
Why it matters to a surgeon
The risk for a surgeon who isn't looking for it
In an ordinary carpal tunnel release, the surgeon cuts the ligament covering the tunnel to free the compressed median nerve. If a palmar-type median artery is present and has become, further down in the palm, the sole blood supply of a finger, accidentally tying it off or cutting it can cut off circulation to that finger, with a risk of necrosis: tissue death from lack of blood.
A link between the palmar-type median artery and carpal tunnel syndrome has been proposed by other researchers, but causation remains unproven: it isn't known whether the artery contributes to compressing the nerve, or whether the two simply tend to occur together in the same tight space. Hand and wrist injuries are common: according to the authors, they account for 11% to 22% of all emergency-room visits in the United States.
This page explains the anatomy; medical decisions stay with the surgeon. Someone about to have wrist surgery cannot tell, just from reading this text, whether they have a persistent median artery or not: that is established through examination and imaging, by the surgeon handling the case.
Limits of the study
What this study doesn't cover
The 56 cadavers were between 62 and 100 years old at death, and information about vascular disease, prior trauma, and prior surgery to the hand and forearm was not available for any of them. The journal's editor flagged this limit explicitly. The authors also say this is the first study to measure the external diameter of the persistent median artery and its relationship to the surrounding vessels, which means the result is waiting on independent replication.
The overall rate of 43% sits close to a prior meta-analysis, by Solewski and colleagues, of 10,394 limbs, which reported 8.6% palmar-type and 34.0% antebrachial-type separately: added together, about 42.6%. But the split between the two types differs a great deal: this study found nearly double the palmar-type share found in that much larger meta-analysis. It isn't known whether the difference comes from the population studied, the dissection method, or chance, and the 15% figure remains an estimate from a single sample, awaiting confirmation from future studies.
Recap
The whole mechanism, in brief
The same story, in words and numbers: the development of the median artery, the three possible routes in an adult, and the full table of measurements.
Weeks 4–5
The arm is a bud; the brachial artery branches for the first time, and the median artery is the main branch feeding the forming hand.
Weeks 6–7
The radial and ulnar arteries develop in parallel and take over more and more of the hand's blood supply; the median artery gradually becomes surplus.
Week 8
In most limbs (57 of 100, in the studied sample), the median artery regresses during embryonic development. In the rest (43 of 100), it stays open for the rest of life.
The antebrachial type (28 of 100)
The median artery persists but ends somewhere in the forearm, before the carpal tunnel. It never reaches the hand.
The palmar type (15 of 100)
The median artery crosses the carpal tunnel alongside the median nerve and continues into the palm, where it can become the sole blood supply of a finger.
The conclusion
A surgeon who cuts the carpal tunnel ligament without knowing about this vessel risks cutting off circulation to the finger it supplies.
| Measurement | Without / type | With / type | Significance |
|---|---|---|---|
| Persistent median artery (of 89 limbs) | — | 43% (38 limbs) | — |
| · antebrachial type | — | 28% (25 limbs) | — |
| · palmar type | — | 15% (13 limbs) | — |
| Superficial palmar arch | 2.02 mm | 2.47 mm (with palmar type) | p = 0.03 |
| Ulnar artery | 2.75 mm | 3.02 mm (with palmar type) | p = 0.08 (trend) |
| Left vs. right arm, radial artery | r² = 0.098 | — | |
| Left vs. right arm, ulnar artery | r² = 0.005 | — | |
Method and sources
What this page is built from
This page starts from the study by Connor Ellis, Drew Thibault, Josh Lencke and Laurieanne D. Hemric (Liberty University College of Osteopathic Medicine), published in PLOS One on 31 March 2025. Every figure about prevalence, diameters and significance thresholds comes from that study. The comparison with the prior published rate comes from Solewski and colleagues' 2021 meta-analysis, cited directly in the article.
The page invents no clinical detail, surgical procedure or individual outcome. The routes shown in the interactive diagram follow the anatomical descriptions in the study; the weeks of development in the embryology figure follow the published timeline (formation around week five, usual regression by week eight). The diagrams are schematic drawings.
- Ellis, Thibault, Lencke, Hemric — "Prevalence and anatomical significance of the persistent median artery: A cadaveric study," PLOS One 20(3):e0320288, 31 March 2025. journals.plos.org · full text on PMC
- Solewski, Lis, Pękala et al. — "The persistent median artery and its vascular patterns: A meta-analysis of 10,394 subjects," Clinical Anatomy 34:1173–1185, 2021. pubmed.ncbi.nlm.nih.gov
- Anatomical plate of the brachial artery's branching — Henry Vandyke Carter, Anatomy of the Human Body (Gray's Anatomy, 20th edition, 1918), public domain. commons.wikimedia.org
