Dissection of the anterior compartment of the forearm and the palm of the hand:
Start with a vertical incision throughout the full length of the forearm; reflect the skin and clean the fascia. Starting with the anterior compartment of the forearm, trace the radial artery starting from the cubital fossa going distally, under the surface of brachioradialis until it leaves the anterior compartment to pass to the anatomical snuff box. Find the radial nerve between brachialis and brachioradialis where it divides into deep and superficial branches. Follow the deep branch as it passes to the posterior compartment to become the posterior interosseous nerve. The superficial branch appears distally going to the dorsum of the hand. Follow the ulnar artery from its origin in the cubital fossa as it travels between the two heads of pronator teres and flexor digitorum superficialis. Identify the common interosseous artery as it arises from the upper part and divides immediately into the anterior and posterior interosseous arteries. Identify the median nerve in the anterior compartment between the two heads of pronator teres after passing the cubital fossa and continues deep to flexor digitorum superficialis. Find the anterior interosseous branch of the median nerve running on the anterior surface of the interosseous membrane. Follow the course of the ulnar nerve from the posterior surface of the medial epicondyle to pass between the two heads of flexor carpi ulnaris and distally on flexor digitorum profundus. It passes superficial to the flexor retinaculum while the median nerve passes deep to it. Now attempt to identify the muscles of the anterior compartment of the forearm. Notice that they lie in three layers and most of them originate from the common flexor tendon and the interosseous membrane, which occupies the space between the radius and ulna separated into the anterior and posterior compartments. The first layer consists of flexor carpi ulnaris, palmaris longus which is sometimes missing, flexor carpi radialis and pronator teres (from medial to lateral). The second layer consists of flexor digitorum superficialis; the third layer consists of flexor digitorum profundus, flexor pollicis longus and pronator quadratus.
On the palmar surface of the hand, start to separate the skin from the palmar surface and from the fingers. You will notice that a large amount of fat is located under the skin of the palm. At the proximal part of the palm, identify palmaris brevis and the triangular palmar aponeurosis; the ulnar nerve and ulnar artery lie deep to palmaris brevis. A small cutaneous branch originates from the ulnar nerve in this area. Notice the palmar digital nerves and arteries passing between the adjacent sides of each two fingers. Try to remove the palmar aponeurosis, taking into consideration the septa from the inferior surface that separates the palm into compartments. Now identify the structures in each compartment as follows, first the thenar eminence which consists of abductor pollicis brevis, flexor pollicis brevis, opponens pollicis and adductor pollicis (don’t forget to identify the two heads). Secondly, identify the three muscles of the hypothenar eminence, abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi. In the proximal part of the palm identify the flexor retinaculum, which forms the carpal tunnel beneath and identify all the related muscles and structures. At this point, the ulnar nerve divides into superficial and deep branches; follow these branches at the base of the hypothenar eminence. Follow the superficial branch in the palm of the hand. The ulnar artery passes superficial to the flexor retinaculum; follow its course across the palm to identify the superficial palmar arch. The median nerve passes to the palm under the flexor retinaculum; follow the median nerve and trace its branches. Follow the tendons of the flexor muscles under the flexor retinaculum. The tendons of flexors digitorum superficialis and profundus lie in a common synovial sheath, but flexor pollicis longus is enclosed in a separate sheath. Follow the extent of both sheaths, and then examine the synovial sheath of the medial four fingers. The lumbrical muscles originate from the flexor digitorum profundus tendons and are inserted in the extensor expansion and in proximal phalanx. Identify the muscles origins and insertions. Expose the palmar interosseous and dorsal interosseous muscles and the deep palmar arch by cutting through the flexor retinaculum and reflecting the flexor tendons. Attempt to identify the muscle origin and insertion and the branches of the deep palmar arch.
Dissection of the anterior compartment of the forearm
Dissection of the palm of the hand
Structure of the front of the forearm
The structures of the hand
Dissection of the posterior compartment of the forearm and the dorsum of the hand:
After removing the skin, clean the fascia and separate the muscles of the posterior compartment of the forearm. Attempt to identify the posterior cutaneous nerve, the medial cutaneous nerve of the forearm, and the dorsal digital nerves on the dorsum of the hand. Identify the extensor retinaculum at the posterior surface of the wrist, and try to keep it until lately to know the direction of the extensor tendons. Try to identify these muscles and their origin and insertion in the posterior compartment; they are arranged in a superficial and a deep group. In the superficial compartment identify brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris and anconeus. The deep group consists of supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis. Do not omit to trace the tendon of the extensor muscles at the dorsum of the hand as some of the tendons pass under the extensor retinaculum to be inserted into the extensor expansion of each finger. Identify the posterior interosseous nerve by following its course passing deep to supinator and going to the posterior compartment of the forearm. The radial artery travels from the anterior compartment of the forearm to end by forming the deep palmar arch. Try to follow the radial artery in the anatomical snuff box until it forms the deep palmar arch.