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M01.03.010 The Anatomical Snuffbox
The anatomical snuffbox, also known as the radial fossa, is a triangular depression on the lateral aspect of the dorsum of the hand, at the level of the carpal bones. It is most prominent when the thumb is extended. Historically, it was used to hold snuff (ground tobacco) for inhalation, giving it its distinctive name.
This guide explores the anatomy of the anatomical snuffbox, including its borders, contents, and clinical significance.
Anatomy of the Anatomical Snuffbox
Borders
The snuffbox has three borders, a floor, and a roof:
| Border | Anatomical Structure |
|---|---|
| Ulnar (medial) | Tendon of the extensor pollicis longus |
| Radial (lateral) | Tendons of the extensor pollicis brevis and abductor pollicis longus |
| Proximal | Styloid process of the radius |
| Floor | Carpal bones: scaphoid and trapezium |
| Roof | Skin |
Note: In anatomical terminology, “medial” and “lateral” refer to the forearm in a supinated position, even though the forearm is often pronated when observing the snuffbox. The borders are formed by the tendons of the muscles, not the muscles themselves.
Contents
The anatomical snuffbox houses critical anatomical structures:
| Structure | Description |
|---|---|
| Radial artery | Crosses the floor, then travels medially between the heads of the adductor pollicis muscle. The radial pulse can sometimes be palpated here. |
| Superficial branch of the radial nerve | Found in the skin and subcutaneous tissue, it innervates the dorsal surface of the lateral three and a half digits and the associated area on the back of the hand. |
| Cephalic vein | Arises from the dorsal venous network of the hand and crosses the snuffbox to ascend the anterolateral forearm. |
Clinical Relevance
1. Scaphoid Fracture
- Mechanism of Injury:
Most commonly caused by a fall on an outstretched hand (FOOSH). - Key Symptoms:
- Pain and tenderness in the anatomical snuffbox.
- Risk of avascular necrosis due to the scaphoid’s retrograde blood supply entering at the distal end.
- Complications:
Missed scaphoid fractures may lead to osteoarthritis of the wrist in later life.
| Feature | Detail |
|---|---|
| Blood Supply to Scaphoid | Runs from distal to proximal, increasing risk of avascular necrosis in proximal fractures. |
Points to Remember
- The anatomical snuffbox is best observed when the thumb is extended.
- Its borders are formed by tendons, not muscles.
- Key structures within the snuffbox include the radial artery, superficial branch of the radial nerve, and cephalic vein.
- Clinical relevance centers around scaphoid fractures and their complications, including avascular necrosis and osteoarthritis.