Dorsal Aspect of the Hand
Extensor retinaculum
The extensor retinaculum is a thickened band of deep fascia at the dorsal surface of the wrist. Its function is to hold the extensor tendons in position. It is attached laterally to the lower end of the radius and medially to the hook of the hamate and the pisiform.
Extensor retinaculum
The extensor retinaculum is a thickened band of deep fascia at the dorsal surface of the wrist. Its function is to hold the extensor tendons in position. It is attached laterally to the lower end of the radius and medially to the hook of the hamate and the pisiform.
Figure1: Extensor retinaculum.
The Structures passing superficial to the retinaculum
The structures passing superficial to the retinaculum from the medial to the lateral side are as follows, the:
1) Posterior cutaneous branch of the ulnar nerve,
2) Basilic vein,
3) Cephalic vein, and
4) Superficial branch of radial nerve.
The structures passing superficial to the retinaculum from the medial to the lateral side are as follows, the:
1) Posterior cutaneous branch of the ulnar nerve,
2) Basilic vein,
3) Cephalic vein, and
4) Superficial branch of radial nerve.
Figure2: Extensor tendons at the dorsum of the hand.
The Structures passing deep to the retinaculum
The space deep to the retinaculum is divided by five septa into six compartments
From lateral to medial compartment:
1) The first compartment transmits the tendons of abductor pollicis longus and extensor pollicis brevis.
2) The second compartment transmits the tendons of extensor carpi radialis longus and extensor carpi radialis brevis.
3) The third compartment transmits the tendon of extensor pollicis longus.
4) The fourth compartment transmits extensor digitorum and extensor indicis tendons.
5) The fifth compartment transmits the tendon of extensor digiti minimi.
6) The sixth compartment transmits the tendon of extensor carpi ulnaris.
The space deep to the retinaculum is divided by five septa into six compartments
From lateral to medial compartment:
1) The first compartment transmits the tendons of abductor pollicis longus and extensor pollicis brevis.
2) The second compartment transmits the tendons of extensor carpi radialis longus and extensor carpi radialis brevis.
3) The third compartment transmits the tendon of extensor pollicis longus.
4) The fourth compartment transmits extensor digitorum and extensor indicis tendons.
5) The fifth compartment transmits the tendon of extensor digiti minimi.
6) The sixth compartment transmits the tendon of extensor carpi ulnaris.
Synovial sheaths of extensor tendons
All the extensor tendons which pass deep to the extensor retinaculum are surrounded by synovial sheaths, which facilitate the movement of the tendons in the extensor compartments. All the extensor tendons have their own sheath
- except extensor digitorum and extensor indicis, which have a common synovial sheath. The synovial sheaths begin just above the retinaculum and reach the end of the tendons inserted into the metacarpals and only to the middle of the hand for those tendons inserted into the phalanges.
Figure3: Extensor tendon.
Anatomical Snuff Box
The anatomical snuff box is a triangular depression on the lateral side of the dorsal surface of the wrist when the thumb is abducted and extended. The apex of the triangle directed to the thumb.
Boundaries
Laterally
The tendons of abductor pollicis longus and the extensor pollicis brevis.
Medially
Extensor pollicis longus tendon.
Roof
The skin, the superficial fascia, the cephalic vein and the superficial branch of the radial nerve.
Floor
The floor is formed by the scaphoid and trapezium. It contains the radial artery, extensor carpi radialis longus and brevis tendons.
Figure4: Anatomical snuff box.
Extensor expansions
The extensor expansions are located in the dorsal surface of the proximal phalanges of the medial four fingers. They are formed as the tendon of extensor digitorum and extensor pollicis longus expand to form the extensor expansion at the dorsal surface of the proximal phalanx. These extensor expansions are joined by extensor digiti minimi, extensor pollicis brevis and extensor indicis. The index, middle, and ring fingers are joined by the tendon of one lumbrical and two interossei muscles. The expansion of the little finger is joined by one lumbrical and only one interosseous muscle. The extensor expansion is a triangular shape. The apex is attached to the base of the distal phalanx. The central part is attached to the middle phalanx of the medial four fingers and to the proximal phalanx of the thumb. The base encircles the metacarpophalangeal joint. The intrinsic muscles of the hand are inserted in the extensor expansion, the lumbricals and interossei in the medial four fingers, adductor pollicis and abductor pollicis brevis are inserted into the extensor expansion of the thumb.
The extensor expansions are located in the dorsal surface of the proximal phalanges of the medial four fingers. They are formed as the tendon of extensor digitorum and extensor pollicis longus expand to form the extensor expansion at the dorsal surface of the proximal phalanx. These extensor expansions are joined by extensor digiti minimi, extensor pollicis brevis and extensor indicis. The index, middle, and ring fingers are joined by the tendon of one lumbrical and two interossei muscles. The expansion of the little finger is joined by one lumbrical and only one interosseous muscle. The extensor expansion is a triangular shape. The apex is attached to the base of the distal phalanx. The central part is attached to the middle phalanx of the medial four fingers and to the proximal phalanx of the thumb. The base encircles the metacarpophalangeal joint. The intrinsic muscles of the hand are inserted in the extensor expansion, the lumbricals and interossei in the medial four fingers, adductor pollicis and abductor pollicis brevis are inserted into the extensor expansion of the thumb.
Figure5: Radial artery.
Radial Artery on the Dorsum of the Hand
The radial artery leaves the forearm by winding round the lateral margin of the wrist to reach the posterior surface of the hand after passing through the anatomical snuff box. It passes between the base of the first and second metacarpals and the two heads of the first dorsal interosseous muscle to reach the palm, where it forms the deep palmar arch.
Branches
1) Dorsal carpal branch:
The dorsal carpal arch provides three dorsal metacarpal arteries which run over the second, third, and fourth interosseous spaces; each divides into two dorsal digital arteries for the adjacent sides of two fingers.
2) First dorsal metacarpal artery:
The first dorsal metacarpal artery divides into two dorsal digital arteries for the adjacent sides of the thumb and index fingers.
3) Dorsal digital artery:
The dorsal digital artery supplies the lateral side of the thumb.
Dorsal metacarpal arteries
There are four dorsal metacarpal arteries which arise from the posterior carpal arch, except for the first one which arises from the radial artery. These arteries supply the adjacent sides of the first, second, third, and fourth intermetacarpal spaces.
Venous Drainage of the Upper Limb
The venous drainage of the upper limb starts by the dorsal venous network that lies on the dorsum of the hand and continues laterally, into the cephalic vein, and medially, into the basilic vein.
The cephalic vein starts from the lateral end of the dorsal venous network and runs along the radial side of the forearm. It crosses the forearm in front of the elbow and then runs into the arm along the lateral border. It passes through the deep fascia to lie in the deltopectoral groove, and then passes through the clavipectoral fascia to drain into the axillary vein where it terminates.
The basilic vein, begins from the medial end of the dorsal venous network and runs along the medial border of the forearm onto the front of the elbow. It then continues upwards along the medial border of the arm where it pierces the deep fascia to terminate at the lower border of the teres major by becoming the axillary vein.
Another vein is the median vein of the forearm that ascends in the midline of the front of the forearm terminating at the median cubital vein, which is a large communicating vein shunting blood from the cephalic vein to the basilic vein. It is located in the superficial fascia of the cubital fossa, starting from the cephalic vein, and runs obliquely upwards and medially to end at the basilic vein. It is separated from the brachial artery by the bicipital aponeurosis.
The venous drainage of the upper limb starts by the dorsal venous network that lies on the dorsum of the hand and continues laterally, into the cephalic vein, and medially, into the basilic vein.
The cephalic vein starts from the lateral end of the dorsal venous network and runs along the radial side of the forearm. It crosses the forearm in front of the elbow and then runs into the arm along the lateral border. It passes through the deep fascia to lie in the deltopectoral groove, and then passes through the clavipectoral fascia to drain into the axillary vein where it terminates.
The basilic vein, begins from the medial end of the dorsal venous network and runs along the medial border of the forearm onto the front of the elbow. It then continues upwards along the medial border of the arm where it pierces the deep fascia to terminate at the lower border of the teres major by becoming the axillary vein.
Another vein is the median vein of the forearm that ascends in the midline of the front of the forearm terminating at the median cubital vein, which is a large communicating vein shunting blood from the cephalic vein to the basilic vein. It is located in the superficial fascia of the cubital fossa, starting from the cephalic vein, and runs obliquely upwards and medially to end at the basilic vein. It is separated from the brachial artery by the bicipital aponeurosis.
Figure6: Venous drainage of the upper limb.
Lymphatic Drainage of the Upper Limb
The superficial lymph nodes of the upper limb can be divided into the deltopectoral lymph nodes that are located in the deltopectoral groove and the supratrochlear lymph nodes, which are located above the medial epicondyle. Deep lymph nodes are also present that can be either axillary lymph nodes (arranged within the armpit), or fewer lymph nodes located along the brachial, radial and ulnar arteries.
The superficial lymph nodes of the upper limb can be divided into the deltopectoral lymph nodes that are located in the deltopectoral groove and the supratrochlear lymph nodes, which are located above the medial epicondyle. Deep lymph nodes are also present that can be either axillary lymph nodes (arranged within the armpit), or fewer lymph nodes located along the brachial, radial and ulnar arteries.