The anatomical snuff box or snuffbox or foveola radialis is a triangular deepening on the radial,

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

aspect of the

hand A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the Koala#Characteristics, koala (which has two thumb#O ...

—at the level of the

carpal bones The carpal bones are the eight small bones that make up the wrist (carpus) that connects the hand to the forearm. The terms "carpus" and "carpal" are derived from the Latin wikt:carpus#Latin, carpus and the Greek language, Greek wikt:καρπός ...

, 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 is the common name of several plants in the genus '' Nicotiana'' of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the ...

, or " snuff." It is sometimes referred to by its French name ''tabatière''.

Structure

Boundaries

* The medial border (ulnar side) of the snuffbox is the

tendon A tendon or sinew is a tough band of fibrous connective tissue, dense fibrous connective tissue that connects skeletal muscle, muscle to bone. It sends the mechanical forces of muscle contraction to the skeletal system, while withstanding tensi ...

of the

extensor pollicis longus In human anatomy, the extensor pollicis longus muscle (EPL) is a skeletal muscle located dorsally on the forearm. It is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together w ...

* The lateral border (radial side) is a pair of parallel and intimate tendons, of the

extensor pollicis brevis In human anatomy, the extensor pollicis brevis (EPB) is a skeletal muscle on the dorsal side of the forearm. It lies on the medial side of, and is closely connected with, the abductor pollicis longus. The extensor pollicis brevis belongs to t ...

and the abductor pollicis longus. (Accordingly, the anatomical snuffbox is most visible, having a more pronounced concavity, during thumb extension.) * The proximal border is formed by the styloid process of the

radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

* The distal border is formed by the approximate apex of the schematic snuffbox

isosceles In geometry, an isosceles triangle () is a triangle that has two sides of equal length and two angles of equal measure. Sometimes it is specified as having ''exactly'' two sides of equal length, and sometimes as having ''at least'' two sides ...

triangle. * The floor of the snuffbox varies depending on the position of the wrist, but both the trapezium 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 In human anatomy, the radial artery is the main artery of the lateral aspect of the forearm. Structure The radial artery arises from the bifurcation of the brachial artery in the antecubital fossa. It runs distally on the anterior part of the ...

, 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 In human anatomy, the metacarpal bones or metacarpus, also known as the "palm bones", are the appendicular skeleton, appendicular bones that form the intermediate part of the hand between the phalanges (fingers) and the carpal bones (wrist, wris ...

to contribute to the superficial and deep palmar arches. In the anatomical snuffbox, the radial artery is closely related (<2 mm) with the superficial branch of radial nerve near the styloid process of radius in 48%, while in 24% the radial artery is openly related to the lateral cutaneous nerve of forearm. The

cephalic vein In human anatomy, the cephalic vein (also called the antecubital vein) is a superficial vein in the arm. It is the longest vein of the upper limb. It starts at the anatomical snuffbox from the radial end of the dorsal venous network of hand, a ...

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

radial nerve The radial nerve is a nerve in the human body that supplies the posterior portion of the upper limb. It innervates the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the Posterior compartment of the ...

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

Clinical significance

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 (FOOSH), 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 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 likely to be the weak link . Scaphoid fracture is one of the most frequent causes of medico-legal issues. An 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 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.

Additional images

File:Gray416.png, Tendons of forefinger and vincula tendina. File:Gray573.png, The veins on the dorsum of the hand. File:Gray1237.svg, Palm of left hand, showing position of skin creases and bones, and surface markings for the volar arches. File:Anatomical snuff box2.jpg, A particularly cavernous anatomical snuff box. File:Schematic drawing of anatomical snuffbox.png, Schematic drawing of anatomical snuffbox.

References

External links

"Instant Anatomy"
{{DEFAULTSORT:Anatomical Snuff Box Hand Anatomy