The anatomical snuffbox is a triangular deepening on the dorsoradial aspect of the hand at the level of the carpal bones.
It is visible with ulnar deviation of the wrist and extension and abduction of the thumb.
The name snuffbox is derived because this depression was used as a means of placement for the inhalation of powdered tobacco.
The anatomical snuffbox is an anatomical landmark, to be specific a surface anatomy feature.
By knowing the extent and content of the box, a better differential diagnosis could be created when there is pain in this area.
For example, tenderness in the anatomical snuffbox after a FOOSH injury may indicate a scaphoid fracture.
The anatomical snuffbox is also known as radial fossa.
Structure of Anatomical Snuffbox
Anatomically, the tendon of extensor pollicis longus forms the posterior border.
The anterior border is formed by extensor pollicis brevis and the abductor pollicis longus.
Just to make perspective clear, the thumb is on the lateral side and little finger is on the medial side.
The styloid process of the radius forms the proximal border and the apex of the triangle formed by the anterior and posterior border forms the distal border.
The floor of the anatomical snuffbox is formed by the scaphoid bone and trapezium bone of the wrist, as well as the tendons of the muscle named the extensor carpi radialis longus and the muscle named the extensor carpi radialis brevis.
The radius and scaphoid articulate deep to the snuffbox to form the basis of the wrist joint.
The base of the first metacarpal bone can be palpated distally, and the styloid process of the radius can be palpated proximally.
Following structures are present within the anatomical snuffbox
- Radial artery
- Superficial branches of the radial nerve,
- Cephalic vein.
Anatomical Variants
The variations noted are in the following structures
- Multiple tendon slips of both the extensor pollicis longus and the abductor pollicis longus have been shown to have not only numerous tendon slips
- Altered insertion points for both of the above tendons
- Variations in the location of the cephalic vein and radial artery.
- Could lead to inadvertent puncture
Clinical Significance
Scaphoid Fracture
The Scaphoid fractures are common after a patient falls onto an outstretched hand [especially when it is pronated and in ulnar deviation].
Tenderness in snuffbox is considered as a hallmark of the scaphoid fractures.
In fact, all patients with snuff box tenderness should be subjected to x-rays to confirm or rule out the scaphoid fractures as the sign is suggestive but is not specific.
De Quervain tenosynovitis
This is tenosynovitis that affects the first dorsal extensor compartment which houses the abductor pollicis longus and extensor pollicis brevis. These muscles form the lateral border of the snuffbox.
The presentation and clinical examination of de Quervain disease are quite typical and the diagnosis is often made clinically.
Idiopathic Radial artery aneurysm in the Snuffbox
Radial artery aneurysms are extremely rare but may develop following radial trauma.
References
- Thwin SS, Fazlin F, Than M. Multiple variations of the tendons of the anatomical snuffbox. Singapore Med J. 2014 Jan;55(1):37-40.
- Robson AJ, See MS, Ellis H. Applied anatomy of the superficial branch of the radial nerve. Clin Anat. 2008 Jan;21(1):38-45.
