Overview
The hand
and wrist is divided into a number of tunnels and anatomical spaces. This
simplifies interpretation of clinical findings; pain on palpation of the
anatomical snuffbox, is associated with injury to the underlying scaphoid bone.
The snuffbox is a triangular region found around the base of the thumb and
first metacarpal. The tendons of three thumb muscles define the space. Several
structures run within the anatomical snuff box.
Gross Anatomy
The anatomical snuffbox is a
triangular shaped region marked by three tendons, and located at the base of
the thumb. It is named the ‘snuff box’ as snuff was slang for tobacco, and was
snorted from this area in the past. The ulna border of the triangle is marked
by the extensor pollicis longus, which inserts onto the distal phalanx of the
thumb and is a long extensor of the thumb.
This radial border is marked by two
other tendons, the extensor pollicis brevis and the abductor pollicis longus.
The radial artery descends from the forearm, and courses radially, passing deep
to the tendons of the snuffbox. The artery runs on top of the scaphoid and
trapezium carpal bones as it traverses the base of the snuffbox. It will then
enter the hand by passing between the two heads of the first dorsal interosseus
muscle. Once it passes through it will form the deep palmar arch. The cephalic
vein originates in the region of the snuffbox before it to runs radially to
drain the dorsal venous network of the hand. The superficial branch of the
radial nerve also follows the course of the cephalic vein, and supplies
sensation to the dorsal surface of the radial 3 and half fingers and hand
(including nailbeds).
Clinical Anatomy
Scaphoid fracture - Pain over the anatomical snuffbox may indicate a scaphoid fracture. This is important because fractures of this bone may not been seen in initial x-rays and lead to significant morbidity. The blood supply to the scaphoid is via palmar and dorsal branches from the radial artery. Blood is transmitted in a retrograde fashion to the proximal pole. The palmar branch enters the distal tubercle and supplies the distal third of the bone. The dorsal branch enters through a non-articular ridge on the dorsal surface and supplies the proximal 80% of the bone. Undiagnosed fractures in patients may lead to avascular necrosis of the scaphoid.
Quick Anatomy
Key Facts
Medial border-
Extensor pollicis brevis and abductor pollicis longus
Lateral border- Extensor pollicis longus
Floor-
Scaphoid and trapezium carpal bones
Lymphatic drainage- Cubital node, supratrochlear nodes, brachial and delto-pectoral lymph nodes.
Lateral two digits- Mainly infraclavicular
nodes
Aide-Memoire
Summary
The
anatomical snuffbox is a triangular region found around the base of the thumb
and first metacarpal. The tendons of three thumb muscles define the space, and
the radial artery runs in this space in order to enter the hand. Anatomical
snuffbox tenderness may indicate scaphoid fracture and may not be seen on
x-ray.