Anatomical Snuffbox: Borders, Floor, Contents and Scaphoid

By Dr Richard Miller, MBChB FRCS · Reviewed 1 October 2026

The anatomical snuffbox is a triangular hollow on the radial side of the back of the wrist, visible when the thumb is fully extended. It lies between the tendons of extensor pollicis longus and extensor pollicis brevis, has the scaphoid in its floor, and carries the radial artery.

Anatomical Snuffbox · key facts

Boundaries: EPL tendon medially (ulnar side); APL and EPB tendons laterally (radial side); radial styloid proximally
Roof: Skin and superficial fascia with the start of the cephalic vein and branches of the superficial radial nerve
Floor: Radial styloid, scaphoid, trapezium and base of first metacarpal (proximal to distal)
Contents: Radial artery crossing the floor
Clinical relevance: Scaphoid fracture, radial pulse, de Quervain's tenosynovitis, cephalic vein cannulation

Boundaries

The anatomical snuffbox is bounded by extensor tendons of the thumb, and it appears only when those tendons are tensed by extending the thumb.

Medial (ulnar, posterior) border: the tendon of extensor pollicis longus (EPL). EPL hooks around the dorsal (Lister's) tubercle of the radius before angling towards the thumb, which is why this border runs obliquely.
Lateral (radial, anterior) border: the tendons of abductor pollicis longus (APL) and extensor pollicis brevis (EPB), which run together in the first extensor compartment.
Proximal border: the styloid process of the radius.
Distal apex: the point where the borders converge, near the base of the first metacarpal.

Floor, roof and contents

The floor of the snuffbox is bony: from proximal to distal it is the radial styloid, the scaphoid, the trapezium and the base of the first metacarpal. The scaphoid is the part felt most clearly, and the tendons of the radial wrist extensors pass under EPL at the medial edge of the floor on their way to the second and third metacarpals.

The roof is skin and superficial fascia. Two superficial structures cross it:

Cephalic vein: it begins here from the radial side of the dorsal venous network of the hand.
Superficial branch of the radial nerve: its branches cross the tendons and supply the skin of the lateral dorsum of the hand and the thumb.

The main content is the radial artery. It leaves the front of the forearm, winds deep to the APL and EPB tendons, crosses the floor on the scaphoid and trapezium, and then passes deep to EPL. It enters the palm between the two heads of the first dorsal interosseous muscle and goes on to form the deep palmar arch.

Blood supply of the scaphoid

The scaphoid is supplied mainly by branches of the radial artery that enter its dorsal ridge and distal pole, and blood reaches the proximal pole by flowing backwards through the bone. The proximal pole has little or no independent supply because most of its surface is covered in articular cartilage.

This retrograde pattern explains why a fracture through the waist of the scaphoid can cut off the proximal fragment. The result is delayed union, non-union or avascular necrosis of the proximal pole, and the more proximal the fracture, the higher the risk.

Clinical relevance

Tenderness in the anatomical snuffbox after a fall on the outstretched hand is treated as a scaphoid fracture until proved otherwise. Early radiographs, including dedicated scaphoid views, can be normal, so a suspected fracture is immobilised and imaged further, often with MRI or CT.

Other scaphoid signs: tenderness over the scaphoid tubercle on the palmar side and pain on axial compression of the thumb.
Radial pulse: the radial artery can be felt against the scaphoid in the floor of the box.
De Quervain's tenosynovitis: inflammation of the APL and EPB tendon sheaths in the first extensor compartment causes pain on the lateral border, reproduced by Finkelstein's test.
EPL rupture: the tendon can fray and rupture at Lister's tubercle weeks after a distal radius fracture, and the medial border of the box is then lost.
Cephalic vein: its start here is a reliable site for cannulation, but the superficial radial nerve lies alongside and can be injured, causing numbness over the dorsum of the thumb.

How it is examined

On a cadaveric spotter, in an OSPE and in MRCS Part B anatomy.

The usual spotter pins the two tendon borders: the single tendon on the ulnar side is extensor pollicis longus; the paired tendons on the radial side are abductor pollicis longus and extensor pollicis brevis.
A pin on the vessel lying on the scaphoid in the floor is the radial artery. The vein in the roof is the cephalic vein, and the thin nerve beside it is the superficial branch of the radial nerve.
Expect the viva question 'why does a scaphoid waist fracture risk avascular necrosis?' Answer with the retrograde blood supply entering distally from branches of the radial artery.
Name the floor in order from proximal to distal: radial styloid, scaphoid, trapezium, base of first metacarpal.
Know where the radial artery goes next: between the heads of the first dorsal interosseous into the palm to form the deep palmar arch.

Key points

The snuffbox lies between EPL medially and APL with EPB laterally.
Its floor is formed by the radial styloid, scaphoid, trapezium and base of the first metacarpal.
The radial artery crosses the floor on its way to the deep palmar arch.
The cephalic vein begins in the roof, alongside the superficial radial nerve.
Snuffbox tenderness after a fall suggests a scaphoid fracture.
Retrograde blood supply puts the proximal scaphoid pole at risk of avascular necrosis.

Common questions

Where is the anatomical snuffbox?

The anatomical snuffbox is on the back of the wrist at the base of the thumb, on the radial side. It shows as a triangular dip when the thumb is extended hard. Its borders are the extensor pollicis longus tendon on the ulnar side and the abductor pollicis longus and extensor pollicis brevis tendons on the radial side, with the radial styloid at its proximal end.

What bone is in the floor of the anatomical snuffbox?

The scaphoid is the main bone in the floor of the anatomical snuffbox, and it is the one that matters clinically. From proximal to distal the floor is the styloid process of the radius, the scaphoid, the trapezium and the base of the first metacarpal. Tenderness when pressing into the floor after a fall is a classic sign of a scaphoid fracture.

What runs through the anatomical snuffbox?

The radial artery runs through the anatomical snuffbox, crossing its floor on the scaphoid and trapezium before passing into the palm through the first dorsal interosseous muscle. The cephalic vein begins in the roof, and branches of the superficial radial nerve cross over the tendons. The radial pulse can be felt in the snuffbox against the scaphoid.

Why is snuffbox tenderness important?

Snuffbox tenderness after a fall on the outstretched hand suggests a scaphoid fracture. The fracture is often invisible on first radiographs, and missing it matters because the scaphoid's blood supply enters distally. A waist or proximal pole fracture can starve the proximal fragment, leading to non-union, avascular necrosis and later wrist arthritis. Suspected fractures are immobilised and imaged further.

References

Gray's Anatomy: The Anatomical Basis of Clinical Practice. Standring S (ed). Elsevier. 42nd edition, 2020.
Moore's Clinically Oriented Anatomy. Moore KL, Dalley AF, Agur AMR. Wolters Kluwer. 9th edition, 2022.
Gray's Anatomy for Students. Drake RL, Vogl AW, Mitchell AWM. Elsevier.