Cutaneous vascular supply

The blood supply to the skin of the upper arm can be divided into three regions with separate supply: the deltoid region, supplied by musculocutaneous perforators, and the medial and lateral regions, supplied by fasciocutaneous perforators (Cormack & Lamberty 1994; Salmon 1994) (Fig. 47.1, Fig. 47.2).

Fig. 47.1 Transverse section through the upper arm to show the location of fasciocutaneous perforators lying on the superficial aspect of the deep fascia.

Fig. 47.2 Muscles of the left upper arm, viewed from the lateral aspect showing fasciocutaneous and musculocutaneous perforating vessels.

The deltoid region is supplied by the posterior circumflex humeral artery (p. 817) via musculocutaneous perforators. After the posterior circumflex humeral artery passes through the quadrangular space (p. 814) it gives off a descending branch, which runs down to the deltoid insertion and the overlying skin, and an ascending branch which passes superiorly towards the acromion, pierces the edge of deltoid and the deep fascia to fan out and supply the overlying skin.

The medial side of the upper arm is supplied by five or six fasciocutaneous perforators which arise from the brachial artery, the superior ulnar collateral artery and, if present, the single artery to biceps. These perforators pass along the medial intermuscular septum to spread out in the deep fascia and anastomose with perforating vessels superiorly and inferiorly and from the lateral side. There are virtually no musculocutaneous perforators through biceps or triceps.

The lateral side of the upper arm below deltoid is supplied by perforating vessels from the middle collateral and radial collateral arteries (the terminating bifurcation of the profunda brachii). The middle collateral artery sends perforators to the skin via the lateral intermuscular septum between brachioradialis and triceps, while the radial collateral artery gives off cutaneous perforators via the intermuscular septum between brachialis and brachioradialis. These cutaneous vessels anastomose with those from the medial side.

Cutaneous innervation

The skin of the shoulder region is supplied by the supraclavicular nerves from the cervical plexus. The floor of the axilla and upper medial surface of the arm is supplied by the lateral branch of the second intercostal nerve (the intercostobrachial nerve). The lower aspect of the medial side of the upper arm is supplied by the medial cutaneous nerve of the arm. The lateral aspect of the upper arm is supplied by the upper lateral cutaneous nerve (a branch of the axillary nerve) and the lower lateral cutaneous nerve (a branch of the radial nerve). The posterior aspect is supplied by the posterior cutaneous nerve of the arm, a branch of the radial nerve (Fig. 45.15, Fig. 45.14).

Brachial fascia

Brachial fascia, the deep fascia of the upper arm, is continuous with the fascia covering deltoid and pectoralis major: it forms a thin, loose sheath for muscles of the upper arm, and sends septa between them. It is thin over biceps, but thicker over triceps and the humeral epicondyles, and is strengthened by fibrous aponeuroses from pectoralis major and latissimus dorsi medially and from deltoid laterally. Strong medial and lateral intermuscular septa extend from it on each side.

The lateral intermuscular septum extends distally from the lateral lip of the intertubercular sulcus of the humerus along the lateral supracondylar ridge to the lateral epicondyle, and blends with the tendon of deltoid. It gives attachment to triceps behind, and brachialis, brachioradialis and extensor carpi radialis longus in front. It is perforated in the middle third by the radial nerve and the radial collateral branch of the profunda brachii artery. The thicker medial intermuscular septum extends from the medial lip of the intertubercular sulcus, distal to teres major, along the medial supracondylar ridge to the medial epicondyle, and blends with the tendon of coracobrachialis. It gives attachment to triceps behind, and brachialis in front. It is perforated by the ulnar nerve, superior ulnar collateral artery, and the posterior branch of the inferior ulnar collateral artery. At the elbow, the brachial fascia is attached to the epicondyles of the humerus and the olecranon of the ulna, and is continuous with the antebrachial fascia. Medially, just below the middle of the upper arm, it is traversed by the basilic vein and lymphatic vessels and, at various levels, branches of the brachial cutaneous nerves.

Together, the lateral and medial intermuscular septa of the upper arm divide the upper arm into anterior and posterior compartments.

Brachial artery

The brachial artery, a continuation of the axillary, begins at the distal (inferior) border of the tendon of teres major and ends about a centimetre distal to the elbow joint (at the level of the neck of the radius) by dividing into radial and ulnar arteries (Fig. 47.5, Fig. 47.6). At first it is medial to the humerus, but gradually spirals anterior to it until it lies midway between the humeral epicondyles. Its pulsation can be felt throughout.

Fig. 47.6 The arterial anastomoses around the left elbow joint viewed from the anterior aspect.

(From Drake, Vogl and Mitchell 2005.)

Relations

The brachial artery is wholly superficial, covered anteriorly only by skin and superficial and deep fasciae. The bicipital aponeurosis crosses it anteriorly at the elbow, separating it from the median cubital vein; the median nerve crosses it lateromedially near the distal attachment of coracobrachialis. Posterior are the long head of triceps, separated by the radial nerve and profunda brachii artery, and then successively by the medial head of triceps, the attachment of coracobrachialis and brachialis. Proximally the median nerve and coracobrachialis lie laterally while distally the biceps and the muscles overlap the artery. Proximally the medial cutaneous nerve of the forearm and ulnar nerve lie medially, while distally the median nerve and basilic vein lie medially. With the artery are two venae comitantes, connected by transverse and oblique branches.

At the elbow the brachial artery sinks deeply into the triangular intermuscular cubital fossa (p. 831).

Variants

The brachial artery, with the median nerve, may diverge from the medial border of the biceps, descending towards the medial humeral epicondyle, usually behind a supracondylar process from which a fibrous arch crosses the artery, and which then runs behind or through pronator teres to the elbow. Occasionally the artery divides proximally into two trunks which reunite. Frequently it divides more proximally than usual into radial, ulnar and common interosseous arteries. Most often the radial branches arise proximally, leaving a common trunk for the ulnar and common interosseous; sometimes the ulnar arises proximally, the radial and common interosseous forming the other division; the common interosseous may also arise proximally. Sometimes slender vasa aberrantia connect the brachial to the axillary artery or to one of the forearm arteries, usually the radial. The brachial artery may be crossed by muscular or tendinous slips from coracobrachialis, biceps, brachialis or pronator teres. Rarely the median nerve crosses behind, and not in front of, the brachial artery near the insertion of coracobrachialis.

Branches

These are profunda brachii, nutrient, superior, middle and inferior ulnar collateral, deltoid, muscular, radial and ulnar arteries.

Profunda brachii artery

The profunda brachii (Fig. 47.2, Fig. 47.3, Fig. 47.5, Fig. 47.6) is a large branch from the posteromedial aspect of the brachial artery, distal to teres major. It follows the radial nerve closely, at first posteriorly between the long and medial heads of triceps, then in the spiral groove covered by the lateral head of triceps. It supplies muscular branches, the nutrient artery of the humerus, and finally divides into terminal radial and middle collateral branches (Fig. 47.6). The radial collateral branch pierces the lateral intermuscular septum to reach the anterior aspect of the epicondyle of the humerus in the groove between brachioradialis and brachialis, and takes part in the anastomosis around the elbow. The middle collateral branch runs posterior to the septum and epicondyle.

The profunda brachii can originate from a common origin with the posterior circumflex humeral artery, from the axillary artery proximal to the tendon of latissimus dorsi or from the distal portion of the axillary artery.

Middle collateral (posterior descending) branch

The middle collateral artery is the larger terminal vessel. It arises posterior to the humerus and descends down the posterior surface of the lateral intermuscular septum to the elbow (Fig. 47.4, Fig. 47.6). Proximally, the artery lies between brachialis (anteriorly) and the lateral head of triceps (posteriorly) while distally it lies between brachioradialis (anteriorly) and the lateral head of triceps (posteriorly). It may pierce the deep fascia and become cutaneous or remain deep to the fascia until anastomosing with the interosseous recurrent artery behind the lateral epicondyle; it gives off about five small fasciocutaneous perforators and often has a small branch that accompanies the nerve to anconeus.

This artery and its fasciocutaneous perforators provide the anatomical basis to allow a skin flap (the lateral arm flap) to be surgically raised (either pedicled or by free tissue transfer) for reconstructing areas of tissue missing elsewhere in the body.

Radial collateral (anterior descending) branch

The radial collateral artery is the continuation of the profunda (Fig. 47.6). It accompanies the radial nerve through the lateral intermuscular septum, descending between brachialis and brachioradialis anterior to the lateral epicondyle, anastomosing with the radial recurrent artery. It supplies brachialis, brachioradialis, the radial nerve and a few fasciocutaneous perforators.

Nutrient artery of humerus

The nutrient artery of the humerus arises near the mid-level of the upper arm, and enters the nutrient canal near the attachment of coracobrachialis, posterior to the deltoid tuberosity; it is directed distally.

Superior ulnar collateral artery

The superior ulnar collateral artery arises a little distal to the mid-level of the upper arm, usually from the brachial artery, but often as a branch from the profunda brachii (Figs 47.4–47.6). It accompanies the ulnar nerve, piercing the medial intermuscular septum to descend in the posterior compartment and supply the medial head of triceps. It passes between the medial epicondyle and olecranon, ending deep to flexor carpi ulnaris by anastomosing with the posterior ulnar recurrent and inferior collateral arteries. A branch sometimes passes anterior to the medial epicondyle and anastomoses with the anterior ulnar recurrent artery.

Fig. 47.7 Superficial veins and nerves of the left upper arm.

(From Sobotta 2006.)

Middle ulnar collateral artery

If present, the middle ulnar collateral artery arises from the brachial artery between the superior and inferior ulnar collaterals. It passes anterior to the medial epicondyle and anastomoses with the anterior ulnar recurrent artery. It supplies triceps and sends small fasciocutaneous perforators to the skin.

Inferior ulnar collateral (supratrochlear) artery

The inferior ulnar collateral artery begins approximately 5 cm proximal to the elbow, passes medially between the median nerve and brachialis and, piercing the medial intermuscular septum, curls round the humerus between the triceps and bone (Fig. 47.5, Fig. 47.6). It forms, by its junction with the middle collateral branch of the profunda brachii artery, an arch proximal to the olecranon fossa. As it lies on brachialis it gives off branches which descend anterior to the medial epicondyle to anastomose with the anterior ulnar recurrent artery. Behind the epicondyle a branch anastomoses with the superior ulnar collateral and posterior ulnar recurrent arteries.

Muscular branches

Muscular branches are distributed to the coracobrachialis, biceps and brachialis.

Deltoid (ascending) branch

The deltoid branch ascends between the lateral and long heads of triceps, and anastomoses with a descending branch of the posterior humeral circumflex artery.

Radial and ulnar arteries

The radial and ulnar arteries are described in detail on page 835.

Brachial veins

The brachial veins flank the brachial artery, as venae comitantes with tributaries similar to the arterial branches; near the lower margin of subscapularis they join the axillary vein. The medial branch, however, often joins the basilic before it becomes the axillary.

These deep veins have numerous anastomoses with each other and with the superficial veins.

Superficial veins

The cephalic vein ascends in front of the elbow superficial to a groove between the brachioradialis and biceps, crosses superficial to the lateral cutaneous nerve of the forearm, ascends lateral to biceps and between pectoralis major and deltoid, where it adjoins the deltoid branch of the thoracoacromial artery (Fig. 45.5, Fig. 47.7). Entering the infraclavicular fossa to pass behind the clavicular head of pectoralis major, it pierces the clavipectoral fascia, crosses the axillary artery and joins the axillary vein just below clavicular level. It may connect with the external jugular by a branch anterior to the clavicle. Sometimes the median cubital vein is large, transferring most blood from the cephalic to the basilic vein; the proximal cephalic vein is then absent or much diminished.

Median nerve

The median nerve (Fig. 45.7, Fig. 47.5, Fig. 47.8) enters the arm lateral to the brachial artery. Near the insertion of coracobrachialis it crosses in front of (rarely behind) the artery, descending medial to it to the cubital fossa where it is posterior to the bicipital aponeurosis and anterior to brachialis, separated by the latter from the elbow joint.

Fig. 47.8 Anterior aspect of the left upper arm dissected to show the musculocutaneous nerve.

(From Sobotta 2006.)

It gives off vascular branches to the brachial artery and usually a branch to pronator teres, a variable distance proximal to the elbow joint.

Musculocutaneous nerve

The musculocutaneous nerve is the nerve of the anterior compartment of the arm (Fig. 47.5, Fig. 47.8). It gives a branch to the shoulder joint and then passes through coracobrachialis, which it supplies, emerging to pass between biceps and brachialis. It sends branches to both these muscles. In the cubital fossa it lies at the lateral margin of the biceps tendon where it continues as the lateral cutaneous nerve of the forearm.

The musculocutaneous nerve has frequent variations. It may run behind coracobrachialis or adhere for some distance to the median nerve and pass behind biceps. Some fibres of the median nerve may run in the musculocutaneous nerve, leaving it to join their proper trunk; less frequently the reverse occurs, and the median nerve sends a branch to the musculocutaneous. Occasionally it supplies pronator teres and may replace radial branches to the dorsal surface of the thumb.

Ulnar nerve

The ulnar nerve gives no branches in the arm (Fig. 47.5, Fig. 47.8). It runs distally through the axilla medial to the axillary artery and between it and the vein, continuing distally medial to the brachial artery as far as the midarm. Here it pierces the medial intermuscular septum, inclining medially as it descends anterior to the medial head of triceps to the interval between the medial epicondyle and the olecranon, with the superior ulnar collateral artery.

Radial nerve

The radial nerve descends behind the third part of the axillary artery and the upper part of the brachial artery, anterior to subscapularis and the tendons of latissimus dorsi and teres major (Figs 47.2–47.4, Fig. 47.8). With the profunda brachii artery it inclines dorsally, passing through the triangular space (see p. 814) below the lower border of teres major, between the long head of triceps and the humerus. Here it supplies the long head of triceps, and gives rise to the posterior cutaneous nerve of the arm which supplies the skin along the posterior surface of the upper arm. It then spirals obliquely across the back of the humerus, lying posterior to the uppermost fibres of the medial head of triceps which separate the nerve from the bone in the first part of the spiral groove. Here it gives off a muscular branch to the lateral head of triceps and a branch which passes through the medial head of triceps to anconeus. On reaching the lateral side of the humerus it pierces the lateral intermuscular septum to enter the anterior compartment; it then descends deep in a furrow between brachialis and proximally brachioradialis, then more distally extensor carpi radialis longus. Anterior to the lateral epicondyle it divides into superficial and deep terminal rami.

The branches of the radial nerve in the upper arm are: muscular, cutaneous, articular and superficial terminal and posterior interosseous.

Medial cutaneous nerve of arm

The medial cutaneous nerve of arm supplies the skin of the medial aspect of the arm (Fig. 47.7). It is the smallest branch of the brachial plexus, and arises from the medial cord and contains fibres from the eighth cervical and first thoracic ventral rami. It traverses the axilla, crossing anterior or posterior to the axillary vein, to which it is then medial, and communicating with the intercostobrachial nerve; it descends medial to the brachial artery and basilic vein (Fig. 47.7) to a point midway in the upper arm, where it pierces the deep fascia to supply a medial area in the distal third of the arm, extending on to its anterior and posterior aspects. Rami reach the skin anterior to the medial epicondyle, and over the olecranon. It connects with the posterior branch of the medial cutaneous nerve of the forearm. Sometimes the medial cutaneous nerve of the arm and the intercostobrachial nerve are connected in a plexiform manner in the axilla. The intercostobrachial nerve may be large and reinforced by part of the lateral cutaneous branch of the third intercostal nerve. It then replaces the medial cutaneous nerve of the arm and receives a connection representing the latter from the brachial plexus (occasionally this connection is absent).

Medial cutaneous nerve of forearm

The medial cutaneous nerve of forearm comes from the medial cord (Fig. 47.7). It is derived from the eighth cervical and first thoracic ventral rami. At first it is between the axillary artery and vein and gives off a ramus which pierces the deep fascia to supply the skin over the biceps, almost to the elbow. The nerve descends medial to the brachial artery, pierces the deep fascia with the basilic vein midway in the arm and divides into anterior and posterior branches. The larger, anterior branch usually passes in front of, occasionally behind, the median cubital vein, descending anteromedial in the forearm to supply the skin as far as the wrist and connecting with the palmar cutaneous branch of the ulnar nerve. The posterior branch descends obliquely medial to the basilic vein, anterior to the medial epicondyle, and curves round to the back of the forearm, descending on its medial border to the wrist, supplying the skin. It connects with the medial cutaneous nerve of the arm, the posterior cutaneous nerve of the forearm, and the dorsal branch of the ulnar.