The anatomical snuffbox is a triangular deepening on the radial, dorsal

Dorsum (biology)

In anatomy, the dorsum is the upper side of animals that typically run, fly, or swim in a horizontal position, and the back side of animals that walk upright. In vertebrates the dorsum contains the backbone. The term dorsal refers to anatomical structures that are either situated toward or grow...

 aspect of the hand

Hand

A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...

—at the level of the carpal bones, specifically, the scaphoid and trapezium bones forming the floor. The name originates from the use of this surface for placing and then sniffing powdered tobacco

Tobacco

Tobacco is an agricultural product processed from the leaves of plants in the genus Nicotiana. It can be consumed, used as a pesticide and, in the form of nicotine tartrate, used in some medicines...

, or “snuff

Snuff

Snuff is a product made from ground or pulverised tobacco leaves. It is an example of smokeless tobacco. It originated in the Americas and was in common use in Europe by the 17th century...

.”

The boundaries

• The posterior border of the snuffbox is the tendon
  Tendon
  A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...
  
   of the extensor pollicis longus.
• The anterior border (closest to the edge of the hand) is a pair of parallel and intimate tendons, of the extensor pollicis brevis and the abductor pollicis longus. (Accordingly, the anatomical snuffbox is most visible, having a more pronounced concavity, during thumb extension
  Extension (kinesiology)
  In kinesiology, extension is a movement of a joint that results in increased angle between two bones or body surfaces at a joint. Extension usually results in straightening of the bones or body surfaces involved. For example, extension is produced by extending the flexed elbow. Straightening of...
  
  .)
• The proximal border is formed by the styloid process
  Radial styloid process
  The radial styloid process is a projection of bone on the lateral surface of the distal radius bone. It extends obliquely downward into a strong, conical projection. The tendon of the brachioradialis attaches at its base, and the radial collateral ligament of the wrist attaches at its apex...
  
   of the radius
  Radius
  In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
  
  
• The distal border is formed by the approximate apex of the schematic snuffbox isosceles triangle.
• The floor of the snuffbox varies depending on the position of the wrist, but both the trapezium
  Trapezium (bone)
  The trapezium bone is a carpal bone in the wrist.The trapezium is distinguished by a deep groove on its palmar surface. It is situated at the radial side of the carpus, between the scaphoid and the first metacarpal bone...
  
   and primarily the scaphoid can be palpated.

Neurovascular anatomy

Deep to the tendons which form the borders of the anatomical snuff box lies the radial artery

Radial artery

In human anatomy, the radial artery is the main blood vessel, with oxygenated blood, of the lateral aspect of the forearm.-Course:The radial artery arises from the bifurcation of the brachial artery in the cubital fossa. It runs distally on the anterior part of the forearm...

, which passes through the anatomical snuffbox on its course from the normal radial pulse detecting area, to the proximal space in between the first and second metacarpals to contribute to the superficial and deep palmar arches. The cephalic vein

Cephalic vein

In human anatomy, the cephalic vein is a superficial vein of the upper limb.It communicates with the basilic vein via the median cubital vein at the elbow and is located in the superficial fascia along the anterolateral surface of the biceps brachii muscle.Superiorly the cephalic vein passes...

 arises within the anatomical snuffbox, while the dorsal cutaneous branch of the radial nerve

Radial nerve

The radial nerve is a nerve in the human body that supplies the upper limb. It supplies the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm and the associated joints and overlying skin.It...

 can be palpated by stroking along the extensor pollicis longus with the dorsal aspect of a fingernail.

Pathology

The radius and scaphoid articulate deep to the snuffbox to form the basis of the wrist joint. In the event of a fall onto an outstretched hand, this is the area through which the brunt of the force will focus. This results in these two bones being the most often fractured of the wrist. In a case where there is localized tenderness

Tenderness (medicine)

In medicine, tenderness is pain or discomfort when an affected area is touched.Rebound tenderness is an indication of peritonitis....

 within the snuffbox, knowledge of wrist anatomy leads to the speedy conclusion that the fracture is likely to be of the scaphoid. This is understandable as the scaphoid is a small, oddly shaped bone whose purpose is to facilitate mobility rather than confer stability to the wrist joint. In the event of inordinate application of force over the wrist, this small scaphoid is clearly likely to be the weak link. Interestingly, scaphoid fracture is one of the most frequent causes of medico-legal issues.

Anatomical peculiarity

An interesting anatomical anomaly in the vascular supply to the scaphoid is the area to which the blood supply is first delivered. Blood enters the scaphoid distally. Consequently, in the event of a fracture the proximal segment of the scaphoid will be devoid of a vascular supply, and will—if action is not taken—avascularly necrose

Necrosis

Necrosis is the premature death of cells in living tissue. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis, which is a naturally occurring cause of cellular death...

within a sufferer's snuffbox. Due to the small size of the scaphoid and its shape, it is difficult to determine, early on, whether or not the scaphoid is indeed fractured with an x-ray. Further complications include; carpal instability (ligament disruption) and fracture-dislocations.

A sound understanding of the anatomical relationships within the wrist allows for rapid, informed, and logical appreciation of dysfunction.

External links

• "Instant Anatomy" (excellent resource for general anatomy)
• Umich.edu medical page
• Dissection at tufts.edu