Anatomical Snuff Box

The anatomical snuff box is a small, triangular depression located on the dorsoradial aspect of the wrist. People use this space for placing and then sniffing the powered tobacco or “snuff”.

This is how the “snuff box” got its name. It is triangular in shape and the base is proximal. The apex of the snuff box is pointing towards the thumb. The anatomical snuff box is seen better when the thumb is extended. It can also be seen well by placing the palm flat on the table and then lift the thumb off of the table. This is another way to clearly see the anatomical snuff box. There are three tendons which form the anatomical snuff box: abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus. Laterally, you can see the tendon of the abductor pollicis longus, and it is inserted into the base of the first metacarpal. The abductor pollicis longus originates from the radius and the ulna. The second tendon is the extensor pollicis brevis, which is inserted into the base of the proximal phalanx. The extensor pollicis brevis originates from the radius. Brevis probably indicates that it is a short muscle, so it comes from the radius. The abductor pollicis longus and the extensor pollicis brevis both form the lateral border of the anatomical snuff box. The extensor pollicis longus forms the ulnar border of the anatomical snuff box. The extensor pollicis longus inserts into the base of the distal phalanx and as its name indicates, its “longus” so it has to be longer.

The extensor pollicis longus comes from the ulna and forms the ulnar side of the anatomical snuff box. The abductor pollicis longus and extensor pollicis brevis tendons are present in the first dorsal extensor compartment. The extensor pollicis longus is present in the third dorsal extensor compartment. All three muscles are supplied by the posterior interosseous nerve, which is a branch of the radial nerve. The contents of the anatomical snuff box are the radial artery that forms the deep palmar arch, the superficial radial nerve, and the cephalic vein. The floor of the anatomical snuff box is composed of the scaphoid and the trapezium. Fracture of the scaphoid bone is a common carpal bone injury. Look for tenderness in the anatomic “snuffbox”. You will consider a fracture and treat it as a fracture even if you don’t see a fracture on the x-ray. Immobilize the wrist in a thumb Spica and see the patient in 10 days to two weeks for re-evaluation and x-rays. Start immobilization early because the nonunion rate will increase if there is a delay in diagnosis for more than 4 weeks. You should diagnose and immobilize the wrist early. The EPL tendon is most commonly due to fractures of the distal radius. Rupture is more common in undisplaced fractures compared to displaced fractures. The patient will be unable to lift the thumb up, especially when the palm is down on a flat surface. Attrition rupture of the EPL can be treated with tendon transfer. Transfer the extensor indicis proprius (EIP) tendon to the EPL tendon; this is the best option. De Quervain syndrome is stenosing tenosynovitis of the first dorsal compartment of the wrist. Locate the anatomical snuff box before injection. The tendons of the radial boundary of the anatomical snuff box are the tendons involved in De Quervain syndrome. Locate these two tendons and inject them. You will find them on the radial aspect of the anatomical snuff box. The extensor pollicis longus (EPL) tendon is on the ulnar side of the anatomical snuff box; do not inject this.

Nabil Ebraheim, MD

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