Anatomical Snuffbox

What is the Anatomical Snuffbox

The anatomical snuffbox, sometimes called the radial fossa, is an anatomical feature found at the dorsal surface of the hand at the base of the thumb as a triangular depression. The depression is located at the carpal level. It is best detectable when you extend the thumb or place the palm on a  table with the thumb lifted upward.

The name ‘snuffbox’ for this anatomical feature derives from the use of the depression to hold powdered tobacco, or ‘snuff,’ before inhaling it. The name was first coined when the anatomical feature was described in medical literature for the first time in 1850.

The anatomical snuffbox is anatomically significant as it allows passage to important blood vessels and nerves.

Anatomy and Structure

Borders

The anatomical snuffbox has 5 borders, with the elevated borders on its 2 sides made up of tendons of the hand.

Formed by Tendons

• Ulnar or Medial Border: The extensor pollicis longus tendon forms this border. It is the border near the top of the dorsum.
• Radial or Lateral Border: The abductor pollicis longus and extensor pollicis brevis tendons together contribute to the radial border. As evident from the name, this border binds the depression laterally.

The Other 3 Borders

• Proximal Border: It is the border on the side of the wrist, formed by the styloid process of the radius.
• Floor: The two adjacent carpal bones, the scaphoid, and trapezium, form the floor.
• Roof: Since the depression forms directly underneath the skin layer, its roof is formed by the skin.

Contents

There are 2 blood vessels and 1 vein in this area, and they cross the extensor retinaculum (the fibrous band that holds all the extensor tendons entering the hand) to pass into the hand on the thumb’s side. 

The superficial radial nerve reaches the wrist and courses over the extensor retinaculum as it divides into multiple branches to innervate several digital muscles along with the associated parts of the lateral digits and the dorsum. One of these branches passes through the anatomical snuffbox.

The cephalic vein arises from the radial side of the dorsal venous network. It passes through the anatomical snuffbox, running superior to the extensor retinaculum. It is responsible for draining blood from the dorsal side of the hand.

The radial artery travels deep to the extensor retinaculum and passes through the anatomical snuffbox along its floor. Then it courses towards the medial side of the hand, traveling between the oblique and transverse heads of the adductor:pollicis. In some people, the radial pulse can be felt at the anatomical snuffbox.

Significance of the Anatomical Snuffbox

Its primary significance lies in the fact that it is the region where scaphoid, the carpal bone, can be palpated. Pain and tenderness of the anatomical snuffbox call for examining the area for a scaphoid fracture. Since scaphoid fractures account for over two-thirds of all carpal bone fractures, it is important to detect them early for proper treatment.