Phu TranUpper Extremity Dissection Guide (Shoulder, brachium, antebrachium, and hand)

All incisions are to be carefully made with the belly of a scalpel, and subcutaneous fat is filleted or peeled to separate from skin and fascia. Fascia will then be carefully peeled away, making sure to note/preserve blood vessels and nerves. Superficial vessels and muscles can be fragile. The goal of the exercise is to expose the relevant anatomy of the upper extremity and then affix labels to them. No skin/muscle will be removed from the body, but the subcutaneous layer and fascia are removed and preserved alongside the body.

Starting at the acromion of the shoulder, perform a circumferential cut anterior to posterior, going a little bit underneath the axilla. This should expose the heads of the shoulder muscles, once the subcutaneous layer and fascia have been removed. Observable anatomies of the shoulder and torso include:

Muscles:-Pectoralis major / minor (ant)-Subclavius (ant)-Subscalpularis (ant above axilla)-Serratus anterior (ant in axilla)

-Teres major / minor (post)-Supraspinatus (post)-Infraspinatus (post)-Latissimus dorsi (post)-Levator scapulae (post on neck)-Trapezius (post)-Rhomboid major/minor (post)

Nerves:Branches of the brachial plexus are likely to be most observable. They are likely to be found with the blood vessels, although the roots and trunks will be buried deep in the neck area. These will continue down the brachium into the antebrachium, with the ulnar and median responsible for most of the hand.-Musculotaneous nerve-Axillary nerve-Median nerve-Radial nerve-Ulnar nerve

Vessels:-Suprascapular artery (ant in neck, crossing subclavian artery and brachial plexus)-Subscapular artery (ant, from axillary artery and anastomoses with suprascapular artery)-Thoracoacromial artery (ant, from axillary artery)-Thoracodorsal artery (ant/lat, branch of subscapular artery)-Scapular circumflex artery (ant on scapula, branch of subscapular artery

The next cut is proximal to distal from the starting circumferential on the shoulder. This cuts toward the lateral side and to the olecranon of the ulna. However, convenience may dictate cutting to the lateral epicondyle of the humerus instead. A next circumferential cut will be made 1-2cm above the cubital fossa to preserve the structures there. Skin is retracted and subcutaneous tissue and fascia peeled away to expose the muscles, vessels, and nerves. Observable anatomies of the brachium include:

Muscles:-Deltoideus (lat/ant)-Biceps brachii (ant with two heads)

-Brachial (lat of biceps)-Triceps brachii (post/med)-Brachioradialis (inf of biceps, under triceps)-Coracobrachialis (med superior near coracoids of scapula)

Nerves:The brachial plexus is further explored as its branches continue down the brachium.

Vessels:The great vessels here follow a branching system. The subclavian sources from the aortic arch on the left and brachiocephalic on the right side of the body. It branches into the axillary artery and cephalic artery. The axillary branches into the anterior/posterior circumflex humeral arteries, subscapular artery, the thoracoacromial artery. Continuing down it branches into the cephalic artery on the lateral side, the brachial artery deep within brachium, and the basilica artery on the medial side. The superficial upper extremity veins are the cephalic on the lateral and basilica on the medial. They communicate through the vena mediana cubiti in the cubital fossa and then branches into accessory veins in the antebrachium. The deep veins include the brachial vein on either side of the brachial artery, the axillary vein as its continuation, which becomes the subclavian vein at the sterna end of the clavicle where it unites with the internal jugular. The deep veins of the forearm are the venae comitantes of the radial and ulnar veins and arise from the deep and superficial volar venous arches in an anastomosis.-Axillary artery/vein-Basilic vein-Cephalic vein-Brachial artery-Profunda brachii artery (deep branch of brachial artery)-Anterior circumflex humeral artery-Posterior circumflex humeral artery/vein-Median cubital vein

At slightly above the cubital fossa, the circumferential cut is made and underlying subcutaneous layer and fascia removed. This will reveal insertions of the biceps brachii and brachioradialis. The bicipital aponeurosis will be fibrous and cover transversely the origins of the antebrachium flexors. The median cubital vein, basilica vein (med), cephalic vein (lat) should be on top or lateral of the aponeurosis. Bisecting the aponeurosis will expose the brachial artery and cubital origins and insertions of the muscles of the arm.

Continue dissecting a lateral cut past the olecranon / lateral epicondyle into the antebrachium and to the wrist. Then perform a circumferential cut at the wrist, slightly before the radioulnar articulation since this area is complex and continues into the hand. Retract/peel back the skin, remove the subcutaneous layer and fascia, being careful of superficial vessels. Observable anatomies of the antebrachium include:

Anterior superficial muscles from lateral to medial:-Brachioradialis (lat/ant from brachium and cubital fossa)-Pronator teres (ant)-Flexor carpi radialis (ant from med epicondyle of humerus)-Palmaris longus (ant/med)-Flexor carpi ulnaris (med on ulna side)-Anconeus (lat/post)-Extensor carpi ulnaris (lat/post on ulna side)

Posterior superficial muscles from lateral to medial:-Extensor digiti minimi (post)-Extensor digitorum (post)-Extensor carpi radialis brevis/longus (med/post/proximal)

Intermediate layer of muscle:Pronator teres and brachioradialis muscles are retracted to expose the middle layer of antebrachium. The Palmaris longus and flexor carpi ulnaris are then retracted to expose:-Flexor digitorum superficialis (ant under flexor carpi ulnaris/radialis, large)Retract the extensor digiti minimi and extensor digitorum on posterior of antebrachium to expose:-Abductor pollicis longus (post under extensor digitorum)

Deep layer of muscle:The flexor digitorum superficialis is either retracted or bisected to reveal the deep layer of muscles.-Flexor pollicis longus (ant/lat)-Flexor digitorum profundus (ant)-Pronator quadratus (ant/lat near wrist)The deep layer of the posterior forearm can be accessed after retracting/bisecting the extensor digitorum and extensor digiti minimi. They lay underneath the extensor carpi ulnaris and extensor carpi radialis brevis.-Extensor indicis (lat/post under extensor digiti minimi, closer to wrist)-Extensor pollicis brevis/longus (med/post/distal)-Supinator (post/med, proximal and diagonally transverse)-Abductor pollicis longus (med/post/distal)

Nerves:The median nerve at the cubital fossa lies internal to the brachial artery next to the biceps brachii tendon on the brachialis muscle. It crosses the ulnar artery obliquely then passes downward between the superficial and deep layers of muscles, between the tendons of flexor digitorum superficialis and flexor carpi ulnaris, deep to the tendon of plamaris longus. It then passes under the annular ligament, called the carpal tunnel, to enter the palm of the hand. The anterior interosseous nerve arises from the median nerve in the distal cubital fossa and passes deep to the pronator quadratus. The ulnar nerve passes posterior to the medial epicondyle of humerus and passes between the two heads of flexor carpi ulnaris into the forearm, descending deep on flexor digitorum profundus, and accompanies the ulnar artery near the middle of the antebrachium. It becomes more superficial in the distal part of the antebrachium. The radial nerve descends between the brachialis and brachioradialis on top of the lateral epicondyle, dividing into superficial and deep branches in the antebrachium. The superficial branch is the direct continuation of the radial nerve, anterior to pronator teres and under the cover of brachioradilias. It then passes posteriorly in the distal forearm deep to the tendon of brachioradalis, piercing the deep fascia before the wrist. The deep branch is larger and pierces the supinator, curving around the lateral radius, giving branches to extensor muscles.-Deep radial nerve-Radial Nerve-Ulnar nerve-Laterial, medial and posterior cutaneous antebrachial nerves (from medial cord of brachial plexus, medial to axillary artery, brachial artery)-Posterior interosseous nerve (continuation of radial nerve after the supinator)

Vessels:The ulnar artery is the main blood vessel of the medial forearm, arising from the brachial artery and terminates in the superficial palmar arch, joining with the radial artery, accompanied by the ulnar veins. The radial artery is the main blood vessel of the lateral forearm, arising from the brachial artery bifurcation in the cubital fossa. The radial winds laterally around the wrist between the heads of the first dorsal interosseous muscle that occupy the space between the metacarpals. The radial artery joins with the deep branch of the ulnar artery, accompanied by the radial vein. The interosseous arteries arise below the tuberosity of the radius from the ulnar artery, dividing into anterior and posterior interosseous branches at the border of the interosseous membrane between ulna and radius.-Ulnar artery/vein-Radial artery/vein-Interosseous arteries (deep)-Median cubital vein (connects basilica and cephalic veins in cubital fossa)

The dissection continues into the hand with a continuous cut from the wrist up the lateral side of the hand, going across the fingertips and into the valleys of each finger, bisecting the skin of the hand in the coronal plane. The skin is then peeled back very carefully to expose the very intricate anatomy of the hand. The volar surface has superficial vessels, and the muscles and nerves are protected by layers of aponeurosis. There are muscles in between the metacarpals, and the big pollicis muscles make up most of the lateral art of the hand. Vessels continue from the wrist from the ulnar artery into the lateral and medial sides of the fingers. Nerves from the median and ulnar nerves innervate the finger muscles and also receive information from the skin of the hand. Tendons from flexor digitorum profundus and superficialis go into the hand. The carpal tunnel ligament should be cut to reveal the deeper muscles and nerves of the hand. Observable anatomies include:

Muscles:-Abductor digiti minimi-Abductor pollicis brevis-Adductor pollicis-Flexor digiti minimi brevis-Flexor pollicis brevis/longus-Hypothenar muscle-Interosseous muscles-Lumbricals-Opponens digiti minimi-Opponens pollicis-Thenar muscle

Nerves:Broken into cutaneous (superficial) and motor groups. There are 4 nerves coming into the general area of the hand: posterior antebrachial cutaneous, radial, ulnar, and median. The ulnar’s dorsal branch and radial nerves continue on their respective sides over the dorsum of the hand. The posterior cutaneous nerve of forearm arises from the radial nerve in the arm can identified over the metacarpals. The ulnar nerve’s superficial branch continues on the medial side but within the hand, supplying the skin and palmar brevis muscle. The median nerve follows under the carpal tunnel (flexor retinaculum), lateral to the ulnar nerve. It follows with the tendons of flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus. The median nerve sends off a recurrent branch of the thenar compartment muscles, and digital cutaneous branches to the fingers coronally into the fingers and across the fingertips. The ulnar nerve’s deep branch passes between abductor digiti minimi and flexor digiti minimi brevis, perforating opponens digiti minimi and follows the deep palmar arch, supplying the hypothenar muscles, all the interosseous muscles, and the third and fourth lumbricals. It ends by supplying adductor pollicis and deep head of flexor pollicis.-Fibrous digital sheaths-Flexor retinaculum-Median nerve-Radial nerve-Recurrent branch of the median nerve-Tendons of flexor digitorum profundus and superficialis-Ulnar nerve

Vessels:-Ulnar artery (med, deep)-Radial artery (lat, deep)-Dorsal venous plexus of the hand (post/dorsal, forming basilica and cephalic veins into forearm)

Bones of the hand:Carpal, wrist:-Scaphoid-Lunate-Triquetrum

-Pisiform-Trapezium-Trapezoid-Capitate-Hamate, hook of hamateFive metacarpals, I to V lateral to medial, I being of the thumbPhalanges: Five proximals, four middles, and five distals (thumb only has proximal and distal)