Chapter 7 Upper Limb

Anterior aspect of the shoulder and upper arm (Figs 7.1–7.12) 64

Posterior aspect of the shoulder and upper arm (Figs 7.13–7.20) 69

Movements of the scapula and shoulder joint 71

Cubital fossa (Figs 7.21–7.26) 73

Anterior aspect of the forearm (Figs 7.27–7.33) 75

Posterior aspect of the elbow and forearm (Figs 7.34–7.39) 77

Movements of the elbow and radioulnar joints (Figs 7.40–7.41) 79

Anterior aspect of the wrist and hand (Figs 7.42–7.49) 80

Anatomical snuff box (Figs 7.50–7.54) 84

Dorsal aspect of the wrist and hand (Figs 7.55–7.58) 85

Movements of the wrist and hand (Figs 7.59–7.62) 87

Thenar and hypothenar eminences (Figs 7.63–7.65) 88

Thenar eminence 88

Hypothenar eminence 89

Finger movements (Figs 7.66–7.71) 89

Interosseous muscles 89

Lumbrical muscles 91

Movements of the hand (Figs 7.72–7.77) 91

Innervation of the upper limb (Figs 7.78–7.81) 92

Arteries of the upper limb (Fig. 7.82) 95

Superfi cial structures of the upper limb (Figs 7.83, 7.84) 96

Anterior aspect of the shoulder and upper arm (Figs 7.1–7.12)

The shoulder girdle is the means by which the humerus of the upper limb is attached to the axial skeleton. It consists of the scapula and the clavicle (Fig. 7.2) and is supported by powerful proximal muscles.

7.1 Anterior aspect of the shoulder and upper arm

7.4 Anterior aspect of the shoulder

1 Clavicle

2 Infraglenoid tubercle

7.6 Anterior aspect of the shoulder and upper arm: muscles

1 Pectoralis major

2 Pectoralis minor

3 Deltoid

4 Long head of biceps

5 Short head of biceps

6 Brachialis

7.7 Action of the pectoralis major muscle

1 Clavicle

2 Acromion

3 Humerus

4 Pectoralis major clavicular head

5 Pectoralis major sternocostal head

6 Seventh costal cartilage

7.10 Attachments and action of the deltoid muscle

1 Clavicle

2 Acromion

3 Spine of the scapula

7.11 Actions of the biceps muscle

A, pronation;

B, supination;

C, forced flexion and supination

Compression forces from the limb are transmitted through the humerus, scapula and clavicle to the axial skeleton. The clavicle articulates medially with the sternum and first rib at the sternoclavicular joint; the costoclavicular ligament is a powerful shock absorber. The clavicle articulates laterally with the scapula at the acromioclavicular joint and through strong coracoclavicular ligaments. The anterior surface of the clavicle, the acromion and the spine of the scapula are subcutaneous and palpable.

The lateral third of the clavicle, the acromion and the spine give lateral attachment to the trapezius muscle (Fig. 7.16, p. 70), which raises, laterally rotates and draws the scapula medially. It is supplied by the accessory (11th cranial) nerve. The deltoid muscle takes its medial attachments from the lateral quarter of the clavicle, the acromion and the spine of the scapula, and forms the smooth contour of the shoulder. Laterally, it is attached to the deltoid tubercle on the lateral aspect of the humerus. It is the prime abductor of the arm, its anterior fibres contributing to flexion and the posterior fibres to extension of the limb; it is supplied by the axillary nerve. The upper end of the humerus can be palpated through the fibres of the relaxed deltoid.

The pectoralis major muscle has two medial heads (Fig. 7.6). The clavicular is attached to the medial two-thirds of the clavicle and the sternocostal to the anterior surface of the sternum, the upper five to seven costal cartilages and the upper part of the external oblique aponeurosis. Laterally, the two heads converge onto a narrow tendon which passes deep to the deltoid muscle to be attached to the lateral lip of the bicipital groove on the humerus. The superior head overlaps the inferior and together they form the bulk of the anterior axillary fold (Fig. 4.14, p. 38). The muscle as a whole is a powerful abductor and medial rotator of the arm; the clavicular head, with the anterior fibres of deltoid, flexes the arm. In contrast, the sternocostal head is a powerful extensor from the flexed position, acting with latissimus dorsi (Fig. 7.16, p. 70), e.g. pulling the body up on an overhead bar and the follow-through of a tennis serve. It can be demonstrated clinically by pressing hands on hips (Fig. 7.7). The muscle is supplied by the medial and the lateral pectoral nerves from the brachial plexus.

The cephalic vein lies in the deltopectoral groove medial to the anterior fibres of the deltoid muscle. It passes deeply through the clavipectoral fascia (a layer between the pectoralis minor and the clavicle) to enter the axillary vein.

The axillary artery and vein can be exposed through an incision through skin and superficial fascia, separating the two heads of the pectoralis major muscle and dividing the clavipectoral fascia. The axillary vein becomes the subclavian vein at the outer border of the first rib behind the middle of the clavicle and is closely related to the posterior surface of this bone. A needle inserted below the clavicle and aimed superomedially adjacent to the posterior aspect of the bone will enter the vein; this provides an important point of access (Fig. 7.9).

The brachial artery lies in the groove between the biceps and brachialis muscles along the length of the arm: it can be palpated by lateral pressure onto the humerus. The median nerve crosses anterior to the brachial artery in the mid-upper arm and comes to lie on its medial side in the cubital fossa. The shoulder joint may be approached through an anterior incision along the anterior border of the deltoid muscle, dividing its attachment to the clavicle and the tendon of the subscapularis muscle, to expose the capsule and anterior surface of the joint.

Actions of the biceps muscle

The tendon of the long head of the biceps muscle is palpable between the lesser and the greater tuberosities of the humerus. The coracoid process of the scapula gives attachment to the coracobrachialis, the short head of the biceps and the pectoralis minor muscles. It can be palpated deeply 1 cm below the clavicle under the medial fibres of the deltoid muscle.

The biceps muscle forms a prominence on the anterior aspect of the arm. Its short head is attached to the coracoid process and the long head passes between the greater and lesser humeral tuberosities, within the bicipital groove, and is attached to the superior aspect of the glenoid fossa on the scapula. Inferiorly the muscle is attached to the bicipital tuberosity on the radius; it has no attachments to the humerus. The muscle flexes the elbow and is a powerful supinator of the forearm: combining these actions produces the greatest prominence of the muscle belly (Fig. 7.11C). The muscle is supplied by the musculocutaneous nerve, which also supplies the coracobrachialis and brachialis muscles. The former muscle is not easily palpable in the lateral aspect of the axilla but the latter forms, with the biceps, the muscle bulk of the anterior aspect of the upper arm.

Posterior aspect of the shoulder and upper arm (Figs 7.13–7.20)

The acromion and spine of the scapula are subcutaneous. The deltoid muscle forms the smooth prominence of the shoulder overlapping the upper end of the humerus; its posterior fibres aid in extension of the shoulder (Fig. 7.16).

7.13 Posterior aspect of the shoulder and upper arm

7.18 Scapula elevation

7.19 Scapula retraction

7.20 Lateral rotation of the scapula

The trapezius forms a wide triangular muscle sheet with its base medially attached to the medial half of the superior nuchal line of the occipital bone, the ligamentum nuchae and the spines and interspinous ligaments of the lower cervical and all the thoracic vertebrae. Laterally the muscle is attached to the lateral third of the clavicle and to the length of the acromion and the spine of the scapula. The wide medial attachment of the muscle produces a wide range of scapular movements, raising, laterally rotating and drawing the bone medially (Fig. 7.16 and 7.18–7.20). The muscle is supplied by the accessory (11th cranial) nerve.

The latissimus dorsi muscle also has a wide medial attachment, to the lumbar spines, lumbar fascia and posterior half of the iliac crest. Its fibres pass upwards and laterally to the floor of the bicipital groove on the humerus. The muscle is also attached to the inferior angle of the scapula, producing medial rotation, and helps to prevent this angle from jutting out from the chest wall during shoulder movements. The latissimus dorsi is a powerful adductor of the arm; its narrow tendon wraps around the teres major muscle in the posterior axillary wall. It is supplied by the thoracodorsal branch of the posterior cord of the brachial plexus, the nerve descending over the medial wall of the axilla to enter the muscle in the axilla.

The lower part of the posterior axillary fold is formed mainly of the teres major muscle, passing from the dorsum of the inferior angle of the scapula to the medial lip of the bicipital groove on the humerus. The lateral border of the scapula can be felt through the bulk of the teres major muscle. The subscapularis muscle contributes to the posterior axillary wall superiorly. Together, the supraspinatus, infraspinatus, teres minor and subscapularis are termed the ‘rotator cuff’ muscles, being closely applied to the shoulder joint and maintaining its stability.

The teres major and the subscapularis muscles pass anterior to the joint, the latter to the lesser tuberosity, and are medial rotators of the shoulder joint. The infraspinatus and teres minor muscles pass posterior to the joint to the greater tuberosity and are lateral rotators. The former muscle is attached medially to the posterior aspect of the scapula below its spine and is palpable, the latter to its lateral border.

The supraspinatus muscle is attached to the posterior aspect of the scapula above the spine and is palpable deep to the trapezius. It passes laterally under the acromion to the greater tuberosity of the humerus. It also stabilises the shoulder joint and is important in initiating abduction, as the deltoid muscle has insufficient mechanical advantage to initiate this movement from the adducted position.

If the supraspinatus muscle is inactive the arm has to be swung or flicked by the hip laterally, away from the body, to enable the deltoid to take over abduction. While not primarily a rotator, supraspinatus does form one of the ‘cuff’ muscles.

The supraspinatus tendon is compressed between the greater tuberosity of the humerus and the acromion in mid-abduction; the arm has to be laterally rotated for full abduction to take place. This can be demonstrated by holding the medial and lateral epicondyles of the humerus through the full range of abduction. The supraspinatus and infraspinatus muscles are supplied by the suprascapular nerve from the upper trunk, and the teres major and suprascapularis muscles by the subscapular nerves from the posterior cord of the brachial plexus. All the intrinsic scapular muscles derive their nerve supply from the fifth and sixth cervical spinal nerve roots. The rotator muscles and supraspinatus stabilise the shoulder joint anteriorly, posteriorly and superiorly.

The muscle bulk of the posterior aspect of the upper arm is produced by the triceps muscle with a smaller contribution from the anconeus near the elbow (Fig. 7.14). The triceps is attached to the posterior shaft of the humerus above (lateral head) and below (medial head) the radial groove and, by its long head, below the glenoid fossa on the scapula. The muscle is attached distally to the palpable olecranon process of the ulna and is a powerful extensor of the elbow; it is supplied by the radial nerve.

Falls onto the outstretched hand can result in fractures of the clavicle; this usually occurs at the junction of the middle and lateral thirds. The shoulder joint is least supported inferiorly, and dislocation in this direction is usually due to a blow to the upper lateral aspect of the abducted humerus. The axillary nerve is at risk. Sensation should be assessed over the distal attachment of the deltoid, since this examination, of the upper lateral cutaneous branch of the axillary nerve, is less painful than testing the action of deltoid in the immediate post-traumatic period. Fractures of the humerus are usually by direct violence. At the upper end this is through the surgical neck; the axillary nerve is again at risk as it lies adjacent to this site. Fractures of the humeral shaft are usually spiral, and the radial nerve, lying in its groove on the posterior aspect of the bone, is at risk; nerve injury produces wrist drop. The triceps is spared in this injury, as it is supplied from above this level.