Pectoral girdle and upper limb: overview and surface anatomy

Published on 18/03/2015 by admin

Last modified 22/04/2025

Print this page

This article have been viewed 18905 times

CHAPTER 45 Pectoral girdle and upper limb: overview and surface anatomy

This chapter is divided into two sections. The first is an overview of the general organization of the upper limb, with particular emphasis on the distribution of the major blood vessels and lymphatic channels, and of the branches of the brachial plexus: it is intended to complement the detailed regional anatomy described in Chapters 46 to 50 Chapter 47 Chapter 48 Chapter 49 Chapter 50. The second section describes the surface anatomy of the upper limb.

BONES AND JOINTS

The bones of the upper limb are the clavicle, scapula, humerus, radius and ulna (connected for a large portion of their length by an interosseous membrane) and the bones of the hand, i.e. the carpals, metacarpals and phalanges (Figs 45.1, 45.2).

Fig. 45.1 Overview of the bones of the left pectoral girdle and upper limb: anterior view.

Fig. 45.2 Overview of the bones of the left pectoral girdle and upper limb: posterior view.

The shoulder girdle is extremely mobile because reciprocal movements at the sternoclavicular and glenohumeral joints enable 180° abduction of the upper limb. Movement occurs in all three planes at the glenohumeral joint.

The elbow joint is a hinge joint. It incorporates the superior (proximal) radio-ulnar joint within its capsule. The proximal and distal radio-ulnar joints permit pronation and supination of the forearm – a unique feature of the primate upper limb.

The range of movement at the condyloid wrist joint, between the distal ends of the radius and ulna and the proximal carpal bones, is supplemented by gliding movements between the carpal bones. The saddle-shaped first carpometacarpal joint, between the trapezium and the base of the first metacarpal, is unique to the primate forelimb and permits opposition of the thumb. The hand is clenched by flexion at the metacarpophalangeal joints, supplemented by gliding movements of the fourth and fifth carpometacarpal joints. In grasping, the thumb is of equal value to the remaining four digits: loss of the thumb is almost as disabling as loss of all of the other digits.

SKIN, FASCIA AND SOFT TISSUES

The skin of the anterior aspect of the upper arm and forearm differs from that of the posterior aspect in that it is thinner and hairless. The palmar skin is thick and hairless: firm attachments to the underlying palmar fascia reflect its role in gripping and shock absorption. The dorsal skin of the hand is much thinner, lax and mobile, and this allows the extensor tendons to glide underneath the subcutaneous tissue.

The direction in which skin tension is greatest varies regionally in the upper limb as in other areas of the body. Skin tension lines that follow the furrows formed when the skin is relaxed are known as ‘relaxed skin tension lines’ and can act as a guide in planning elective incisions.

The superficial fascia is a layer of subcutaneous fatty tissue. Its thickness depends on the degree of obesity of the subject: measurement of the thickness of the subcutaneous tissue of the posterior upper arm is used as an indicator of obesity. With the exception of the digital pads, there is less subcutaneous tissue in the palm of the hand than on the dorsum of the hand.

The depth of deep fascia varies according to the stresses to which it is subjected in the different areas of the limb. In the upper arm it is a thin but quite obvious layer. Intermuscular septa pass to the medial and lateral sides of the humerus, separating the upper arm muscles into anterior and posterior groups within their respective compartments. Each muscle also lies within its own delicate fascial shea than arrangement that allows individual muscles to glide upon each other.

The deep fascia condenses anteriorly at the elbow as the tough bicipital aponeurosis; it is otherwise relatively thin in the forearm where it is attached along the subcutaneous border of the ulna. Intermuscular septa divide the forearm into three compartments, namely, anterior (contains the flexor group of muscles), posterior (extensors) and the mobile wad compartment for brachioradialis and extensor carpi radialis longus and brevis.

At the wrist the deep fascia becomes condensed anteriorly and posteriorly as the flexor and extensor retinacula respectively. Further condensation occurs in the palm of the hand, where the palmar aponeurosis is reinforced by the insertion of the tendon of palmaris longus, and in the flexor tendon sheaths and fascial system associated with the digits.

MUSCLES

Posterior and anterior muscle groups connect the pectoral girdle to the axial skeleton; the only bony connection is at the sternoclavicular joint. The posterior muscles are trapezius, levator scapulae and the rhomboid muscles: their actions include raising the shoulder and drawing the scapula medially. The anterior muscles are pectoralis minor, serratus anterior, and subclavius. Serratus anterior and trapezius together rotate the scapula in abduction of the arm.

Latissimus dorsi (posteriorly) and pectoralis major (anteriorly) run from the axial skeleton to the humerus. They are both powerful adductors and medial rotators of the shoulder; latissimus dorsi is also a powerful extensor.

A large group of muscles arise from the shoulder girdle and pass to the humerus. They are the four muscles of the rotator cuff (subscapularis, supraspinatus, infraspinatus and teres minor), teres major, deltoid, the clavicular origin of pectoralis major, biceps brachii, coracobrachialis and the long head of triceps.

The muscles of the upper arm can be divided into an anterior group of elbow flexors (biceps brachii, brachialis and coracobrachialis) and a posterior group of elbow extensors (triceps and anconeus). Biceps brachii is also a powerful supinator of the radio-ulnar joints.

The extensor muscles of the wrist and fingers, together with brachioradialis and a slip of origin of supinator, arise from the lateral epicondyle of the humerus. The principal head of pronator teres, the carpal flexor muscles, palmaris longus and, at a deeper level, the main origin of flexor digitorum superficialis, all arise from the medial epicondyle of the humerus. More deeply, flexor pollicis longus, flexor digitorum profundus and pronator quadratus arise from the anterior aspects of the shafts of the radius and ulna and the intervening interosseous membrane. Abductor pollicis longus, extensors pollicis longus and brevis and extensor indicis all arise from the posterior aspects of these bones and the intervening interosseous membrane.

The small, intrinsic, muscles of the hand consist of a thenar and a hypothenar group, and the muscles of the palm (the anterior and posterior interossei and the lumbricals). They are all concerned with the intricate movements of the digits.

VASCULAR SUPPLY AND LYMPHATIC DRAINAGE

ARTERIAL SUPPLY

The blood supply to the skin of the upper limb comes from a combination of direct cutaneous, fasciocutaneous and musculocutaneous vessels (Figs 45.3, 45.4; see Fig. 7.19).

Fig. 45.3 Overview of arteries of the left upper limb.

Fig. 45.4 The anatomical territories served by the cutaneous blood supply to the upper limb.

(From Cormack GC, Lamberty BGH 1994 The Arterial Anatomy of Skin Flaps, 2nd edn. Edinburgh: Churchill Livingstone, with permission.)

The axial artery to the upper limb is the subclavian artery, which becomes the axillary artery after crossing the lateral edge of the first rib. The axillary artery becomes the brachial artery as it crosses the distal edge of the posterior axillary fold, i.e. at the lower border of teres major. At first, the brachial artery lies in the flexor compartment on the medial side of the upper arm, but later it inclines laterally until it lies anterior to the elbow joint. Just distal to the elbow, it divides into the radial and ulnar arteries, both of which remain in, and supply, the flexor compartment. The ulnar artery almost immediately gives rise to the common interosseous artery, and this divides into anterior and posterior interosseous arteries which travel towards the wrist on either side of the interosseous membrane (the anterior interosseous artery lies directly on the membrane and the posterior interosseous artery is separated from it by the deep extensor muscles).

The muscles and other components of the extensor aspect are supplied by the profunda brachii artery in the upper arm, and by the posterior interosseous artery in the forearm. The hand is supplied by rich, and somewhat variable, anastomoses between branches of the radial and ulnar arteries, principally on its palmar aspect.

Each upper limb joint is supplied by an extensive anastomosis of arteries fed by descending vessels that arise proximal to the joint and ascending recurrent branches that arise distal to the joint.

VENOUS DRAINAGE

The venous drainage of the upper limb is composed of superficial and deep groups of vessels.

The superficial group starts as an irregular dorsal arch on the back of the hand. The cephalic vein begins at the radial extremity of the arch, ascends along the lateral aspect of the arm within the superficial fascia and then pierces the deep fascia to enter the axillary vein just distal to the clavicle (Fig. 45.5). The basilic vein drains the ulnar end of the arch, passes along the medial aspect of the forearm, pierces the deep fascia at the elbow and joins the venae comitantes of the brachial artery to form the axillary vein. In front of the elbow, the prominent median cubital vein links the cephalic and basilic veins. It receives a number of tributaries from the front of the forearm and gives off the deep median vein which pierces the fascial roof of the antecubital fossa to join the venae comitantes of the brachial artery.

Fig. 45.5 Overview of veins of the left upper limb.

The deep group of veins accompany the arteries, usually as venae comitantes, and ultimately become the axillary and then the subclavian vein. They drain the tissues beneath the deep fascia of the upper limb and are connected to the superficial system by perforating veins.

LYMPH NODES AND DRAINAGE

Superficial tissues

Superficial lymphatic vessels begin in cutaneous plexuses. In the hand, the palmar plexus is denser than the dorsal plexus. Digital plexuses drain along the digital borders to their webs, where they join the distal palmar vessels, which pass back to the dorsal aspect of the hand. The proximal palm drains towards the carpus, medially by vessels that run along its ulnar border, and laterally to join vessels draining the thumb. Several vessels from the central palmar plexus form a trunk that winds round the second metacarpal bone to join the dorsal vessels that drain the index finger and thumb.

In the forearm and arm, superficial vessels run with the superficial veins. Collecting vessels from the hand pass into the forearm on all carpal aspects. Dorsal vessels, after running proximally in parallel, curve successively round the borders of the limb to join the ventral vessels. Anterior carpal vessels run through the forearm parallel with the median vein of the forearm to the cubital region, then follow the medial border of biceps brachii before piercing the deep fascia at the anterior axillary fold to end in the lateral axillary lymph nodes (Fig. 45.6).

Fig. 45.6 Lymph nodes of the left upper limb.

Lymph vessels that lie laterally in the forearm receive vessels that curve round the lateral border from the dorsal aspect of the limb. They follow the cephalic vein to the level of the deltoid tendon, where most incline medially to reach the lateral axillary nodes; a few continue with the vein and drain into the infraclavicular nodes. Vessels lying medially in the forearm are joined by vessels that curve round the medial border of the limb. They follow the basilic vein. Proximal to the elbow some end in supratrochlear lymph nodes whose efferents, together with the medial vessels that have bypassed them, pierce the deep fascia with the basilic vein and end in the lateral axillary nodes or deep lymphatic vessels.

Collecting vessels from the deltoid region pass round the anterior and posterior axillary folds to end in the axillary nodes. The scapular skin drains either to subscapular axillary nodes or by channels that follow the transverse cervical vessels to the inferior deep cervical nodes.

Lymphatic drainage of deep tissues

Deep lymph vessels follow the main neurovascular bundles (radial, ulnar, interosseous and brachial) to the lateral axillary nodes. They are less numerous than the superficial vessels and communicate with them at intervals. A few lymph nodes occur along the vessels. Scapular muscles drain mainly to the subscapular axillary nodes, and pectoral muscles drain mainly to the pectoral, central and apical nodes (Fig. 45.6).

INNERVATION

OVERVIEW OF THE BRACHIAL PLEXUS

The brachial plexus is formed by the union of the ventral rami of the lower four cervical nerves and the greater part of the first thoracic ventral ramus (Fig. 45.7; see Fig. 46.29).

Fig. 45.7 A schematic plan of the left brachial plexus.

(Adapted from Drake, Vogl and Mitchell 2005.)

The fourth ramus usually gives a branch to the fifth, and the first thoracic ramus frequently receives a branch from the second. These ventral rami are the roots of the plexus: they are almost equal in size but variable in their mode of junction. Contributions to the plexus by C4 and T2 vary. When the branch from C4 is large, that from T2 is frequently absent and the branch from T1 is reduced, forming a ‘prefixed’ type of plexus. If the branch from C4 is small or absent, the contribution from C5 is reduced but that from T1 is larger and there is always a contribution from T2: this arrangement constitutes a ‘postfixed’ type of plexus.

Close to their exit from the intervertebral foramina, the fifth and sixth cervical ventral rami receive grey rami communicantes from the middle cervical sympathetic ganglion, and the seventh and eighth rami receive grey rami from the cervicothoracic ganglion. The first thoracic ventral ramus receives a grey ramus from, and contributes a white ramus to, the cervicothoracic ganglion.

The most common arrangement of the brachial plexus is as follows: the fifth and sixth rami unite at the lateral border of scalenus medius as the upper trunk; the eighth cervical and first thoracic rami join behind scalenus anterior as the lower trunk; the seventh cervical ramus becomes the middle trunk. The three trunks incline laterally, and either just above or behind the clavicle each bifurcates into anterior and posterior divisions. The anterior divisions of the upper and middle trunks form a lateral cord that lies lateral to the axillary artery. The anterior division of the lower trunk descends at first behind and then medial to the axillary artery and forms the medial cord; it often receives a branch from the seventh cervical ramus. Posterior divisions of all three trunks form the posterior cord, which is at first above, and then behind, the axillary artery. The posterior division of the lower trunk is much smaller than the others and is frequently derived from the eighth cervical ramus before the trunk is formed; it contains few, if any, fibres from the first thoracic ramus.

Axillary nerve (C5, 6)

The axillary nerve is a branch of the posterior cord of the brachial plexus. It winds posteriorly around the neck of the humerus together with the circumflex humeral vessels, and supplies deltoid and teres minor and an area of skin over the deltoid region (Fig. 45.8).

Fig. 45.8 Motor and sensory branches of the axillary nerve.

The radial nerve is the continuation of the posterior cord of the brachial plexus (Fig. 45.9). In the upper arm it lies in the spiral groove of the humerus where it is accompanied by the profunda brachii artery and its venal comitantes. It enters the posterior (extensor) compartment and supplies triceps, then re-enters the anterior compartment of the arm by piercing the lateral intermuscular septum. At the level of the lateral epicondyle it gives off the posterior interosseous nerve, which passes between the two heads of supinator and enters the extensor compartment of the forearm. The posterior interosseous nerve supplies these muscles, while the radial nerve proper continues into the forearm in the anterior compartment deep to brachioradialis and terminates by supplying the skin over the posterior aspect of the thumb, index, middle and radial half of the ring finger.

Fig. 45.9 Motor and sensory branches of the radial nerve. Variation exists in the cutaneous innervation of the dorsal aspects of the digits. Here the radial nerve is shown to supply all five digits. The dorsum of the ring and little fingers is frequently innervated by the dorsal branch of the ulnar nerve.

Musculocutaneous nerve (C5–7)

The musculocutaneous nerve is formed from the continuation of the lateral cord of the brachial plexus. It pierces and supplies coracobrachialis, biceps and brachialis, and then continues into the forearm as the lateral cutaneous nerve of the forearm (Fig. 45.10).

Fig. 45.10 Motor and sensory branches of the musculocutaneous nerve.

Median nerve (C6–8, T1)

The median nerve is formed by the union of the terminal branch of the lateral and medial cords of the brachial plexus (Fig. 45.11). It has no branches in the upper arm. It enters the forearm between the two heads of pronator teres and gives off the anterior interosseous nerve, which supplies all the flexor muscles of the forearm apart from flexor carpi ulnaris and the ulnar half of flexor digitorum profundus. The median nerve itself passes deep to the flexor retinaculum at the wrist. On entering the palm, it gives off motor branches to the thenar muscles and the radial two lumbricals, and cutaneous branches to the palmar aspect of the thumb, index and middle fingers and the radial half of the ring finger.

Fig. 45.11 Motor and sensory branches of the median nerve. Flexor pollicis brevis may be supplied by both median nerve and ulnar nerve.

Ulnar nerve (C7, C8, T1)

The ulnar nerve is the continuation of the medial cord of the brachial plexus (Fig. 45.12). Like the median nerve, it has no branches in the upper arm. It enters the posterior compartment of the upper arm midway down its length by piercing the medial intermuscular septum, passes behind the medial epicondyle of the humerus to enter the forearm and descends to the wrist deep to flexor carpi ulnaris. The ulnar nerve supplies flexor carpi ulnaris and the ulnar half of flexor digitorum profundus. Just proximal to the wrist it gives off a dorsal cutaneous branch that supplies the skin over the dorsal aspect of the little finger and the ulnar half of the ring finger, and then crosses into the palm superficial to the flexor retinaculum in Guyon’s canal. It divides into a motor branch, which supplies the hypothenar muscles, the intrinsic muscles of the hand (apart from the radial two lumbricals) and adductor pollicis, and cutaneous branches, which supply the skin of the palmar aspect of the little finger and the ulnar half of the ring finger.

Fig. 45.12 Motor and sensory branches of the ulnar nerve together with the medial cutaneous nerve of the arm and the forearm. Flexor pollicis brevis may be supplied by both median nerve and ulnar nerve.

AUTONOMIC INNERVATION

The autonomic supply to the limbs is exclusively sympathetic. The preganglionic sympathetic inflow to the upper limb is derived from neurones in the lateral horn of the upper thoracic spinal segments T2–6(7). Fibres pass in white rami communicantes to the thoracic sympathetic chain and synapse in the stellate and second thoracic ganglia. Postganglionic fibres to the skin are distributed via cutaneous branches of the brachial plexus. The blood vessels to the upper limb receive their sympathetic supply via adjacent peripheral nerves, thus the median nerve supplies postganglionic sympathetic fibres to the brachial artery and the palmar arches, and the ulnar nerve supplies the ulnar artery.

MOVEMENTS, MUSCLES AND SEGMENTAL INNERVATION

Most limb muscles are innervated by neurones derived from more than one segment of the spinal cord. The predominant segmental origin of the nerve supply for each of the muscles of the upper limb and for the movements which take place at the joints of the upper limb is summarized in Tables 45.1–45.4. Red has been used in Table 45.1 to highlight those muscles or movements which have diagnostic value (see below). The following caveats should be borne in mind when consulting these tables.

Table 45.1 Movements, muscles and segmental innervation in the upper limb. Muscles and movements that have diagnostic value are marked in red

Table 45.2 Segmental innervation of the muscles of the upper limb

C3, 4	Trapezius, levator scapulae
C5	Rhomboids, deltoids, supraspinatus, infraspinatus, teres minor, biceps
C6	Serratus anterior, latissimus dorsi, subscapularis, teres major, pectoralis major (clavicular head), biceps, coracobrachialis, brachialis, brachioradialis, supinator, extensor carpi radialis longus
C7	Serratus anterior, latissimus dorsi, pectoralis major (sternal head), pectoralis minor, triceps, pronator teres, flexor carpi radialis, flexor digitorum superficialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi
C8	Pectoralis major (sternal head), pectoralis minor, triceps, flexor digitorum superficialis, flexor digitorum profundus, flexor pollicis longus, pronator quadratus, flexor carpi ulnaris, extensor carpi ulnaris, abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis, extensor indicis, abductor pollicis brevis, flexor pollicis brevis, opponens pollicis
T1	Flexor digitorum profundus, intrinsic muscles of the hand (except abductor pollicis brevis, flexor pollicis brevis, opponens pollicis)

Table 45.3 Segmental innervation of joint movements of the upper limb

Shoulder	Abductors and lateral rotators	C5
Shoulder	Adductors and medial rotators	C6–8
Elbow	Flexors	C5, 6
Elbow	Extensors	C7, 8
Forearm	Supinators	C6
Forearm	Pronators	C7, 8
Wrist	Flexors and extensors	C6, 7
Digits	Long flexors and extensors	C7, 8
Hand	Intrinsic muscles	C8, T1

Table 45.4 Movements and muscles tested to determine the location of a lesion in the upper limb

Movements

At the central nervous level of control, muscles are not recognized as individual actuators but as components of movement, and may therefore contribute to several types of movement, acting variously as prime movers, antagonists, fixators or synergists. For example, serratus anterior acts as an antagonist of trapezius as the scapula moves around the thorax, whereas both muscles act together as prime movers during the forward rotation of the scapula. Some muscles have been included in more than one place in Table 45.1, on the basis that a muscle which acts across one joint can produce a combination of movements (e.g. flexion with medial rotation, or extension with adduction) and a muscle which crosses two joints can produce more than one movement. It must also be remembered that these listings are not exhaustive.

Nerve roots

There is no universal consensus concerning the contribution that individual spinal roots make to the innervation of individual muscles: the most positive identifications, which are limited, have been obtained by electrically stimulating spinal roots and recording the evoked electromyographic activity in the muscles. Much of the information in Tables 45.1–45.4 is therefore based on neurological experience gained in examining the effects of lesions, and some of it is far from new. In Table 45.1, spinal roots have been given the same colour (light peach, dark peach, red) when they innervate a muscle to a similar extent, or when differences in their contribution have not been described. Red has been used to indicate roots from which there is known to be a dominant contribution. From a clinical viewpoint, some of these roots may be regarded as innervating the muscle almost exclusively, e.g. deltoid by C5, brachioradialis by C6, and triceps by C7. Minor contributions have been retained in the table in order to increase its utility in other contexts, such as electromyography and comparative anatomy.

Neurological location of a lesion

In clinical practice it is only necessary to test a relatively small number of muscles in order to determine the location of a lesion. Any muscle to be tested must satisfy a number of criteria. It should be visible, so that wasting or fasciculation can be observed, and the muscle consistency with contraction can be felt. It should have an isolated action, so that its function can be tested separately. It should help to differentiate between lesions at different levels in the neuraxis and in the peripheral nerve, or between peripheral nerves. It should be tested in such a way that normal can be differentiated from abnormal, so that slight weakness can be detected early with reliability. Some preference should be given to muscles with an easily elicited reflex.

Table 45.4 gives a list of movements and muscles chosen according to these criteria. For example, with an upper motor neurone lesion, shoulder abduction, elbow extension, wrist and finger extension and finger abduction are weaker than their opposing movements. Since this weakness may be more distal than proximal or vice versa, normal shoulder abduction and finger abduction excludes an upper motor neurone weakness of the arm. Some muscles are difficult to test but are included for special reasons, e.g. the strength of brachioradialis is difficult to assess but it can be seen and felt, it is mostly innervated by the C6 root, and it has an easily elicited reflex.

Knowledge of the sequence in which motor branches leave a peripheral nerve to innervate specific muscles is very helpful in locating the level of a lesion. For example, with radial nerve lesions, if triceps is involved, then the lesion must be high in the axilla; if (as is usual), triceps is spared but brachioradialis, wrist extensors, finger extensors and the superficial radial nerve are all involved, then the lesion is in the arm, where the radial nerve is vulnerable to pressure against the humerus; if wrist extension is normal and the superficial radial nerve is not involved but finger extension is weak, then the lesion involves the posterior interosseous branch of the radial nerve.

SURFACE ANATOMY

SKIN

Palmar skin is marked by a number of creases, but they are of little value as points of reference. Transverse skin creases cross the palmar aspects of the fingers in three situations. The most proximal crease is placed at the junction of the digit with the palm and lies nearly 2 cm distal to the metacarpophalangeal joint, the intermediate crease lies opposite the proximal interphalangeal joint, and the distal crease is placed just proximal to the distal interphalangeal joint.

The flexor retinaculum may be outlined by defining its bony attachments. Its distal border, concave downwards, may be indicated on the surface by a curved line that joins the crest of the trapezium to the hook of the hamate. Its proximal border may be indicated by a curved line, concave upwards, that joins the tubercle of the scaphoid to the pisiform. Flexion of the wrist produces a number of transverse skin creases (usually two or three) at the wrist. The dominant crease, which is distal, overlies the proximal edge of the flexor retinaculum; the carpal tunnel lies distal to this crease, under the palmar skin.

SKELETAL LANDMARKS

The clavicle is both visible and palpable throughout its course. Its outline can be traced from the expanded sternal end, which forms the lateral boundary of the suprasternal notch, to the flattened acromial extremity. The line of the acromioclavicular joint is palpable as a distinct ‘step’ in an anteroposterior plane. The acromion can be traced from the acromioclavicular joint to its tip, and then backwards across the top of the shoulder until it meets the crest of the spine of the scapula at the prominent acromial angle. From this point, the spine of the scapula can be palpated as it passes medially from the acromial angle to the medial (vertebral) border of the scapula, where it lies opposite the spine of the third thoracic vertebra. The spine is subcutaneous and is easily visible in a thin subject.

The medial border of the scapula is hidden in its upper part by trapezius, but below the spine it can be palpated as it passes downwards to the inferior angle. Although covered by teres major and latissimus dorsi, the inferior angle can easily be felt when it is approached from below, and it can be seen to move laterally and forwards around the chest wall when the arm is raised above the head. The inferior angle of the scapula is at the level of the spine of the seventh thoracic vertebra and overlies the seventh rib. When a thoracotomy is being performed, it is a convenient landmark from which the ribs can be counted along the lateral chest wall.

A small depression can be seen inferior to the clavicle at the junction of its convex medial and concave lateral portions. This is the infraclavicular fossa (or deltopectoral triangle) and it intervenes between the surface elevations produced by the clavicular origins of pectoralis major and deltoid. The apex of the coracoid process lies 2.5 cm below the clavicle immediately to the lateral side of this fossa, under cover of the anterior fibres of deltoid. If the examining finger is passed laterally from the coracoid process, the lesser tubercle of the humerus will be felt below the tip of the acromion on deep pressure through deltoid. This bony prominence slips away from the examining finger when the humerus is rotated laterally or medially. The greater tubercle of the humerus is the most lateral bony point in the shoulder region and projects laterally below and in front of the acromial angle. It can also be felt to move on rotation of the humerus. When the arm is abducted, the head of the humerus can be palpated on deep pressure in the apex of the axilla.

The shaft of the humerus can only be felt indistinctly through its course because its outline is obscured by overlying muscles. Distally, the medial epicondyle of the humerus is a conspicuous landmark and is easily felt, particularly when the elbow is flexed; proximally it can be traced upwards into the medial supracondylar ridge. The ulnar nerve can be rolled from side to side posterior to the base of the medial epicondyle. The lateral epicondyle is not so prominent, but its posterior surface is easily palpated and its lateral margin can be traced upwards into the lateral supracondylar ridge on deep pressure. Inspection of the posterior aspect of the extended elbow reveals a well-marked depression to the lateral side of the midline. This is bounded laterally by the fleshy elevation formed by the superficial group of forearm extensor muscles and medially by the lateral side of the olecranon. The floor of this depression contains, in its upper part, the posterior surface of the lateral epicondyle and, in its lower part, the head of the radius. Although the latter is covered by the anular ligament, it can be felt to rotate when the forearm is pronated and supinated. Between the lateral epicondyle and the radial head, the humero-radial part of the elbow joint can be felt as a distinct transverse depression.

When the elbow is extended, the apex of the olecranon can be felt and seen to lie in a line level with the two epicondyles. When the elbow is flexed, the apex of the olecranon descends and the three bony points then form the angles of a triangle. This relationship is lost in dislocation of the elbow. The posterior surface of the olecranon is subcutaneous and tapers from above downwards. It can be felt with ease immediately below the apex.

The level of the elbow joint is situated 2 cm below a line joining the two epicondyles. It slopes downwards and medially from its lateral extremity, and this obliquity produces the ‘carrying angle’. When the elbow is fully extended and the forearm and hand are in supination (‘the anatomical position’), the carrying angle is normally 165° in the female and 175° in the male. It disappears on full flexion of the elbow, when the shafts of the ulna and humerus come to lie in the same plane, and is also obscured in full pronation of the forearm.

The posterior border of the ulna is subcutaneous throughout its whole extent, from the subcutaneous surface of the olecranon superiorly to the styloid process below. Its position corresponds to the longitudinal furrow that can be seen on the posterior aspect of the forearm when the elbow is fully flexed, and which separates the flexor group of muscles from the extensors. In contrast, the shaft of the radius can only be felt indistinctly because it is covered by muscles. The rounded head of the ulna forms a surface elevation on the medial part of the posterior aspect of the wrist when the hand is pronated. The styloid process of the ulna projects distally from the posteromedial aspect of the head.

The expanded lower end of the radius forms a slight surface elevation on the lateral side of the wrist and can be traced downwards into the styloid process of the radius. The posterior aspect of the lower end of the radius is partly obscured by the extensor tendons but can be palpated without difficulty. It presents a tubercle (of Lister), which is grooved on its ulnar aspect by the tendon of extensor pollicis longus. The tubercle lies in line with the cleft between the index and the middle fingers.

The wrist joint is easily identified between the carpus and the distal ends of the radius and ulna on flexion and extension of the wrist, even though it is covered by tendons. The line of the wrist joint corresponds to a line, convex upwards, that joins the styloid process of the radius to that of the ulna. It is delineated by the proximal of the two transverse anterior wrist skin creases.

Four of the bones of the carpus can be palpated and identified. The pisiform forms an elevation that can be both seen and felt on the palmar aspect of the wrist at the base of the hypothenar eminence. It can be moved over the articular surface of the triquetrum when the wrist is passively flexed. The hook of the hamate lies 2.5 cm distal to the pisiform and is in line with the ulnar border of the ring finger. It can be felt by deep pressure in this situation, and here the superficial division of the ulnar nerve can be rolled from side to side over the tip of the hook. The tubercle of the scaphoid is situated at the base of the thenar eminence, and in many subjects forms a small visible elevation. Immediately distal to it, but covered by the muscles of the thenar eminence, the crest of the trapezium can be identified on deep pressure. The scaphoid and trapezium can also be palpated in the ‘anatomical snuffbox’.

The heads of the metacarpal bones form the prominence of the knuckles, that of the middle finger being the most prominent. Their convex palmar aspects can be felt on deep pressure over the front of the metacarpophalangeal joints and can be gripped between the finger and the thumb. Deep pressure over the distal aspect of the head of the metacarpal bone reveals the base of the corresponding proximal phalanx; the line of the metacarpophalangeal joint can be detected on the dorsum of the hand as the fingers are flexed and extended. The dorsal aspects of the shafts of the metacarpal bones of the fingers and thumb and of the trapezium can be felt rather indistinctly, since they are obscured by the extensor tendons. The interphalangeal joints can be felt on the dorsal aspect of the flexed finger, just distal to the prominences caused by the heads of the proximal and middle phalanges.

MUSCULOTENDINOUS LANDMARKS

Deltoid may be delineated when the arm is abducted against resistance, and its tendon can be identified about half-way down the lateral aspect of the humerus. Its anterior border can be traced upwards and medially from the anterior aspect of the humerus, across the tendon of pectoralis major, to form the lateral boundary of the infraclavicular fossa. The posterior border runs upwards and medially from the posterior aspect of the deltoid tendon and reaches the crest of the spine of the scapula near its medial end. The normal rounded contour of the shoulder is produced by deltoid, which spreads out over the lateral aspect of the greater tubercle of the humerus. In dislocation of the shoulder, the greater tubercle is displaced medially, deltoid descends vertically to its humeral attachment, and the normal rounded contour of the shoulder is lost.

The rounded lower border of pectoralis major forms the anterior axillary fold. It is rendered more conspicuous when the abducted arm is adducted against resistance, e.g. when the hand is placed on the hip and pressed firmly against the trunk. When the arm is flexed to a right angle against resistance, the clavicular head of the muscle can be felt and seen to contract. When the flexed arm is extended against resistance, the clavicular head becomes relaxed but the sternocostal head stands out in relief.

The posterior fold of the axilla, produced by latissimus dorsi and the underlying teres major, reaches a lower level on the humerus than the anterior fold. Both latissimus dorsi and teres major participate in adduction of the arm: when the abducted arm is adducted against resistance, the posterior fold of the axilla is accentuated and the lateral border of latissimus dorsi can be traced downwards to its attachment to the iliac crest. When the arm is raised above the head, the lower five or six serrations of serratus anterior can be seen on the lateral aspect of the chest; they pass downwards and forwards to interdigitate with the serrations of external oblique. When serratus anterior is paralysed following injury to its nerve, the medial border, and especially the lower angle of the scapula, stand out prominently to produce a characteristic ‘winged’ appearance that can be accentuated by asking the patient to press both hands against a wall.

The belly of biceps brachii produces a conspicuous elevation on the anterior aspect of the arm. It diminishes above, where it is covered by pectoralis major, and below, where it is replaced by its tendon just above the elbow joint. Shallow furrows indicate its medial and lateral borders. When the elbow is flexed against resistance, biceps becomes still more obvious, and the bicipital tendon can be held between finger and thumb and traced down into the cubital fossa. With the arm held in this position, the sharp upper margin of the bicipital aponeurosis can be traced downwards and medially over the elevation produced by the superficial group of forearm flexor muscles. Coracobrachialis emerges from the lateral wall of the axilla and forms a rounded ridge on the upper part of the medial side of biceps.

Posteriorly, the lateral head of triceps forms an elevation medial and parallel to the posterior border of deltoid and is thrown into prominence when the elbow is extended against resistance. On its medial side, the fleshy mass produced by the long head of triceps disappears above under cover of deltoid.

Brachioradialis is the most superficial of the muscles on the lateral side of the forearm. When the elbow is flexed in the semi-prone position against resistance, brachioradialis stands out as a prominent ridge extending upwards beyond the level of the elbow joint on the lateral side of the arm.

Proximal to the wrist crease, the prominent tendon of flexor carpi radialis can be seen and palpated when the wrist is flexed; the radial artery lies on its lateral side. By palpating lateral to flexor carpi radialis, 3 or 4 cm proximal to the wrist crease, it is possible to feel flexor pollicis longus (bending and straightening the thumb will confirm that the examining finger is in the correct place). The area on the ulnar side of flexor carpi radialis is packed most densely with functionally important structures. The median nerve lies very close to the skin surface and is therefore often injured in lacerations. It is covered by palmaris longus, when that muscle is present (best confirmed by pinching thumb and ring finger together, when the muscle will be seen to stand out). When palmaris longus is absent, only a thin covering of subcutaneous fat and deep fascia separates skin and nerve. The four tendons of flexor digitorum superficialis lie deep to the median nerve: the tendons for the middle and ring fingers lie in front of those for the index and little fingers as they pass deep to the flexor retinaculum and can be felt, and usually seen, to move on flexion of the fingers. Deeper still are the tendons of flexor digitorum profundus. The large and robust tendon of flexor carpi ulnaris is easily palpated on the ulnar side of the front of the wrist; the ulnar nerve, artery and venae comitantes lie in the shelter of its radial edge. Any sharp injury powerful enough to cut through this strong tendon usually has enough energy left to cut the nerve and vessel.

When the thumb is fully extended, a depression known as the anatomical snuffbox is seen on the lateral aspect of the wrist, immediately distal to the radial styloid process (Fig. 45.13). Palpating distally from the styloid process, three structures are usually encountered: the convex ovoid proximal articular surface of the scaphoid (best felt during alternate ulnar and radial deviation at the wrist); less distinctly, the radial aspect of the trapezium; and the expanded base of the first metacarpal (best felt during circumduction of the thumb). When clinically assessing wrist stability throughout the range of wrist movements, the scaphoid may be effectively compressed bidigitally, between index finger and thumb, along its oblique long axis between tubercle and articular surface. The trapezium may be similarly compressed between its crest and radial aspect.