Distal Upper Extremity

Remove the skin and superficial fascia of the forearm and hand if not previously performed. Incise the deep fascia covering the forearm to expose individual muscles.

Re-identify the brachial, ulnar and radial arteries, median nerve and brachioradialis muscle in the proximal forearm. Note the brachioradialis arises from lateral epicondyle.

On the medial arm, locate the medial epicondyle of the humerus. Identify from lateral to medial the pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis and flexor carpi ulnaris muscles which all arise from the medial epicondyle.

Identify the following forearm structures:

• Dorsal forearm: Extensor carpi ulnaris, extensor digiti minimi and extensor digitorum
• Radial forearm: Radius, extensor carpi radialis brevis, extensor carpi radialis longus, brachioradialis, radial nerve
• Ulnar forearm: Ulna, flexor carpi ulnaris, extensor carpi ulnaris

At the wrist, identify muscles having a deep origin in the posterior forearm from medial to radial: extensor indicis, extensor pollicis longus, extensor pollicis brevis, abductor pollicis longus.

Divide the extensor retinaculum and follow the tendons of the superficial muscles onto the dorsum of the hand to identify: extensor digitorum, extensor digiti minimi, extensor indicis and ulnar nerve.

At the base of the thumb, locate the boundaries of the anatomical snuff box: extensor longus and extensor pollicis brevis. Within the anatomical snuff, locate the radial artery coursing from anterior to radial. Note the scaphoid bone forms the floor of the snuff box.

At the anterior wrist, locate the radial artery.

Locate the tendons of the superficial muscles radial to ulnar: flexor carpi radialis, palmaris longus and flexor carpi ulnaris. Locate the ulnar artery and nerve deep to the flexor carpi ulnaris.

Identify the flexor digitorum superficialis at the wrist. Find the median nerve at the lateral border of the muscle.

Divide the radial attachment of the flexor digitorum superficialis. Reflect the muscle medially to show the flexor pollicis longus, flexor digitorum profundus and the median nerve.

Follow the ulnar nerve and vessels into the hand by opening the ulnar tunnel (Guyton’s canal) which is lateral to the pisiform bone.

Follow the ulnar nerve branches into the hand.

Follow the radial artery into the hand and look for its contribution to the palmar arterial arch.

Identify and divide the flexor retinaculum (transverse carpal ligament) to expose the carpal tunnel.

Examine a skeleton and locate the scaphoid, trapezium, pisiform and hamate bones that form the attachments of the flexor retinaculum.

Follow the median nerve into the hand and identify the recurrent branch to the thenar eminence.

Tendons within the carpal tunnel: flexor digitorum superficialis, flexor digitorum profundus and flexor pollicis longus.

Examine the skeletal forearm and hand alongside the donor’s hand. Locate the positions of the wrist, carpometacarpal, metacarpophalangeal, interphalangeal joints.

In the hand, identify carpal tunnel, thenar and hypothenar eminences.

In the thenar eminence, identify flexor pollicis brevis and abductor pollicis brevis.  Separate these muscles to see opponens pollicis.

On the palmar side of the hand, incise the digital fibrous sheath of the middle finger to follow the tendons.

Locate the tendon of the deep flexor where it splits the tendon of the superficial flexor to reach the distal phalanx.

Follow the median nerve across the palm to the radial and ulnar borders of the digits. Note the accompanying digital arteries.

Identify the first and second lumbricals arising from radial side of the tendons of the flexor digitorum profundus and extending radially to the extensor hood. Generally, the lumbricals provide flexion of the metacarpointerphalangeal (MP) joint and extension of the interphalangeal (IP) joints.

Examine the hand from its radial border to see the 1st lumbrical extending to the extensor hood along with the 1st dorsal interosseous.

Identify the adductor pollicis in the web space between thumb and index fingers. Note this muscle is not part of the thenar eminence and is innervated by the ulnar nerve.

From a palmar view, identify the oblique and transverse heads of the adductor pollicis and its innervation from a deep branch of the ulnar nerve.

Follow the ulnar nerve distal to the wrist. Locate its superficial and deep branches. The superficial branches supply the muscles of the hypothenar eminence and sensation to the ulnar digits. The deep branches supply all of the intrinsic muscles of the hand except the thenar eminence and the first two lumbricals.

Divide flexor tendons and the median nerve proximal to the carpal tunnel at the wrist. Reflect these tendons and median nerve distally. Divide the adductor pollicis along its medial border to expose the interossei.

Dorsal interossei arise from metacarpals and extend to the extensor hood. Dorsal interossei spread digits, flex MP joints and extend IP joints. Palmar interossei arise from metacarpals and extend to extensor hood. Palmar interossei bring digits together, flex MP joints and extend IP joints.

The deep palmar arterial arch and deep branch of the ulnar nerve cross proximal to the phalanges. The deep ulnar branch supplies adductor pollicis, 3rd and 4th lumbricals and all interossei.

The extensor digitorum, interossei and lumbricals converge at the extensor hood to provide flexion of the MP joint and extension of the PIP and DIP joints.

Compare the video above and images below to a skeleton. The dissection depicted is destructive of other anatomic structures. If performed, use the non-dissected hand.

Examine the wrist joint, carpal bones, carpal tunnel, CMC joints, MP joints and IP joints on a skeleton. Note joint configuration in relation to its motion. Compare the joints of the hand to other joints in the body, for example, the knee and IP joints.