PYOGENIC ARTHRITIS OF THE SHOULDER (General description of arthritis, p. 96)

Pyogenic arthritis of the shoulder is uncommon. It may complicate a penetrating wound, or it may be a haematogenous (blood borne) infection. In children infection may spread to the shoulder from a focus of osteomyelitis in the upper metaphysis of the humerus (p. 279).

The clinical features resemble those of pyogenic arthritis of other joints. The onset is rapid and is accompanied by pyrexia. The shoulder is swollen and abnormally warm, and all movements are greatly restricted. Treatment follows the lines suggested on page 98.

TUBERCULOUS ARTHRITIS OF THE SHOULDER (General description of tuberculous arthritis, p. 98)

Tuberculous arthritis of the shoulder has become a rare disease in Western countries. It occurs much less commonly than tuberculosis of the spine, hip, and knee. As with tuberculosis elsewhere, it occurs more commonly in African countries and in the East than in most countries of Europe and in North America.

The pathological and clinical features correspond to those of tuberculous arthritis in any major joint. Treatment with antituberculous drugs follows the general principles outlined on page 102. In early cases good recovery of function may occur, but in more advanced cases of bone and joint destruction surgical intervention with arthrodesis of the joint may be required.

RHEUMATOID ARTHRITIS OF THE SHOULDER (General description of rheumatoid arthritis, p. 134)

The shoulder is commonly affected by rheumatoid arthritis, though less commonly than the more peripheral joints such as hands, wrists and feet. Often both shoulders are affected simultaneously with other upper limb joints, with consequent serious impairment of function.

As in other superficial joints, the main clinical features are local pain and stiffness, increased warmth, swelling from synovial thickening, and marked restriction of movement. There is wasting of the deltoid muscle, with consequent flattening of the shoulder contour (Fig. 14.5A). Radiographs show rare-faction of bone, narrowing of the cartilage space, and eventually erosion of bone at the joint margins (Fig. 14.5B).

Fig. 14.5 Rheumatoid arthritis of the shoulder. In A note the marked flattening of the contour from muscle wasting. The radiograph in B shows rarefaction of the bones, with narrowing of the joint space from loss of articular cartilage.

Treatment. This is mainly that for rheumatoid arthritis in general, as described on page 137. Exercises are important in maintaining a useful range of movement.

Operative treatment. Severe disability often results from the bone and cartilage destruction produced by the inflammatory rheumatoid synovitis. When this occurs replacement arthroplasty of the joint may be indicated to restore mobility and relieve pain. Early designs used a metal humeral head prosthesis with a stem cemented into the shaft of the bone (Fig. 14.6). This articulated with a small concave polyethylene prosthesis to resurface the glenoid socket. Pain relief following this surgery is usually good, but full active movement, particularly in abduction, is never restored. The main problems that compromise the result are loosening of the glenoid prosthesis because of inadequate bone support and the degeneration of the scapulo-humeral muscles. Newer prosthetic designs to address these problems, including surface replacements and reversed prostheses are under trial, but no long-term results are yet available.

Fig. 14.6 Replacement arthroplasty of the gleno-humeral joint for rheumatoid arthritis of the shoulder, using a two-piece Neer prosthesis.

OSTEOARTHRITIS OF THE SHOULDER (General description of osteoarthritis, p. 140)

Unlike most other joints, the shoulder is seldom affected by osteoarthritis. When it is affected there is usually a clear predisposing factor, such as previous injury or disease, avascular necrosis of the humeral head, or senility. The rarity of osteoarthritis of the shoulder is explained by its freedom from pressure stresses.

Pathology. The articular cartilage is worn away. The underlying bone becomes eburnated and at the joint margins it hypertrophies to form osteophytes.

Clinical features. The patient is usually elderly: osteoarthritis is exceptional in the shoulders of younger patients. The main complaint is of pain in the shoulder and down the upper arm.

On examination there is no increase of local skin temperature and no synovial thickening. But a soft swelling due to effusion of fluid into the joint is common. Movements are restricted.

Radiographs show narrowing of the cartilage space: the joint outlines are clear-cut and often show some sclerosis; there is ‘spurring’ from osteophyte formation at the joint margins (Fig. 14.7).

Fig. 14.7 Osteoarthritis of the shoulder in an old woman. Note loss of articular cartilage, marginal osteophytes and sclerosis at the joint surfaces. Osteoarthritis is uncommon in the shoulder.

Treatment. In most cases active treatment is unnecessary once the nature of the affection has been explained. If treatment is called for, conservative measures should usually be relied upon and gentle exercises are often helpful. If there is a large effusion it should be aspirated. Only exceptionally would operation be justified: if it were, replacement arthroplasty (see under rheumatoid arthritis, p. 260) would usually be advised, but arthrodesis might occasionally be appropriate.

‘FROZEN’ SHOULDER (Adhesive capsulitis; periarthritis)

‘Frozen’ shoulder is a common but ill’understood affection of the gleno-humeral joint, characterised by pain and uniform limitation of all movements but without radiographic change, and with a tendency to slow spontaneous recovery under appropriate treatment.

Cause. This is unknown. There is no evidence of infection. Injury is an inconstant factor and its significance is doubtful. Nevertheless it is accepted that symptoms of ‘frozen’ shoulder do often begin a few weeks after some form of injury.

Pathology. This is not fully understood, though the intense fibroblastic response may represent an auto-immune reaction similar to that seen with Dupuytren’s contracture of the hand. There is a loss of resilience of the joint capsule, with adhesions between the synovial folds. Whatever their nature, the changes are reversible, and in most cases the range of joint movement is eventually restored to near normal.

Clinical features. The patient complains of severe aching pain in the shoulder and upper arm, of gradual and spontaneous onset. Pain is often severe enough to disturb sleep. On examination the only finding is uniform impairment of all gleno-humeral movements – abduction, flexion, extension, rotation – which are often reduced to about a quarter or half of their normal range. In a severe case much of the shoulder movement that remains is contributed by scapular movement, which is unimpaired. Radiographs do not show any abnormality.

Diagnosis. The characteristic feature of ‘frozen’ shoulder is the uniform limitation of all gleno-humeral movements without evidence of inflammatory or destructive changes.

Course. There is a tendency towards spontaneous recovery, usually within 6–12 months. The pain subsides first, leaving gleno-humeral joint stiffness, which thereafter gradually resolves with active use of the limb. If movements are not practised deliberately some permanent restriction of movement may remain.

Treatment. In the early, acutely painful stage the arm is rested in a sling, which is removed for short periods each day to permit gentle assisted shoulder exercises. Generally, non-steroidal anti-inflammatory drugs should be prescribed in addition to conventional analgesics. Steroid injections into the gleno-humeral joint may be of value in some patients with persistent severe pain. When the pain lessens, active exercises are intensified and continued for weeks or months until full movement is regained. If mobilisation is very slow after the pain has abated the shoulder may be manipulated gently under anaesthesia to break down residual adhesions. Manipulation may be required at some stage in up to a third of all cases, or arthroscopic distension with saline may be used as an alternative method.

It is important to warn the patient at the beginning that recovery may take many months, but at the same time to give assurance that eventually recovery is likely to be complete.

RECURRENT ANTERIOR DISLOCATION OF THE SHOULDER

Traumatic dislocation of the shoulder is liable to cause structural changes in the gleno-humeral joint which predispose to repeated dislocations. Rarely, dislocation may occur repeatedly in a patient with unduly lax ligaments, in the absence of trauma.

Pathology. This is twofold (Figs 14.8 and 14.9A):

Fig. 14.8 Horizontal section of left shoulder showing the pathology of recurrent dislocation. The diagram on the left shows the normal condition. In the right-hand diagram the humeral head is shown dislocated forwards. It has stripped the capsule from the margin of the glenoid, creating a pocket in front of the neck of the scapula into which the humeral head is displaced. Note that the humeral head has been dented by the sharp glenoid margin, producing the typical defect of the articular surface.

Fig. 14.9 A Typical defect of articular surface of humeral head (arrow), found in most cases of recurrent dislocation of the shoulder. B Radiographic appearance with the arm in 80 ° of medial rotation. The defect (arrow) is seen in profile at the upper and outer quadrant of the humeral head.

The consequent defect in the contour of the articular surface allows the head to slip over the front of the glenoid when the arm is in lateral rotation, abduction, and extension. The dislocation is anterior, and it must be emphasised that the humeral head always remains within the capsule, in contradistinction to non-recurrent dislocation, in which the humeral head is displaced through a rent in the capsule.

Clinical features. The patient is usually a fit young adult, accustomed to sporting activities. Nearly always, recurrent dislocation follows an initial violent dislocation, often in a heavy fall. Thereafter dislocation recurs with trivial violence, characteristically during combined abduction, lateral rotation, and extension (for example, in putting on a coat).

On examination no clinical abnormality is apparent, but it may be found that the patient becomes apprehensive when the arm is placed in a position of abduction, extension, and lateral rotation – the position often adopted when putting on a coat.

Imaging. Routine radiographs with the limb in the anatomical position do not show any abnormality, but special profile views taken with the arm in 60–80 ° of medial rotation show the characteristic bony defect of the humeral head (Fig. 14.9B). The defect is not seen in any other projection, but it can be shown more clearly by computerised tomographic (CT) imaging or by magnetic resonance imaging (MRI). An MRI scan combined with arthrography provides the most detailed information on the bone and soft-tissue pathology (Fig. 14.10).

Treatment. Conservative treatment is not effective and if dislocation recurs frequently operation is justified. The two treatment principles used to prevent further dislocation are to either repair the defect in the glenoid labrum (Bankart¹ operation), or to create an overlapping buttress of muscle or bone on the anterior margin of the glenoid (Putti–Platt² or Bristow operations). Traditionally this required an open procedure through an anterior incision but increasingly this has been replaced by closed arthroscopic techniques for repair. However, it must be emphasised that the results in terms of functional outcome are identical with open or closed methods. Arthroscopic surgery, though more convenient for the patient, should only be undertaken by surgeons trained in the necessary specialist skills and equipped with the sophisticated equipment required.

RECURRENT POSTERIOR DISLOCATION

Posterior dislocation of the shoulder is much less common than anterior dislocation. Often – indeed usually – the cause is an electric shock or an epileptiform convulsion, and it is not uncommon for both shoulders to be dislocated together. The dislocation is prone to become recurrent. The pathology is analogous to that of recurrent anterior dislocation:

Dislocation occurs on abduction and medial rotation.

Operative repair may be effected by reefing the infraspinatus tendon in a similar way to that used on the subscapularis for anterior dislocation. An alternative method is to deepen and widen the glenoid socket by screwing a suitably shaped block of iliac bone to the back of the neck of the scapula (bone-block operation).

Like recurrent anterior dislocation, recurrent posterior dislocation may sometimes occur spontaneously, without previous injury, in a patient with ligamentous laxity.

COMPLETE TEAR OF ROTATOR (TENDINOUS) CUFF (Torn supraspinatus)

It is important to distinguish complete tears of the rotator tendinous cuff from incomplete tears. The clinical effects are different. Whereas an incomplete tear is one cause of the ‘painful arc syndrome’ (p. 268), without obvious loss of power, a complete tear impairs seriously the ability to abduct the shoulder.

Cause. The tendon gives way under a sudden strain, usually caused by a fall. The injury is not necessarily a severe one; indeed it often seems to be mild. Age-degeneration of the tendon is a constant predisposing factor.

Pathology. The tear is mainly of the supraspinatus tendon, but it may extend into the adjacent subscapularis or infraspinatus tendons. The tear is close to the insertion of the tendons and usually involves the capsule of the joint, with which the tendons are blended. The edges of the rent retract, leaving a gaping eliptical hole which establishes a communication between the shoulder joint and the subacromial bursa (Fig. 14.11). In general, it may be said that a tendon that ruptures is usually already degenerate: thus rupture occurs mainly in the elderly.

Fig. 14.11 Tear of supraspinatus shown diagrammatically. Note that the subacromial bursa communicates with the shoulder joint through the rent.

Clinical features. The patient is usually a man over 60: only occasionally is a younger patient affected. After a strain or fall he complains of pain at the tip of the shoulder and down the upper arm, and of inability to raise the arm.

On examination there is local tenderness below the lateral margin of the acromion. When the patient attempts to abduct the arm no movement occurs at the gleno-humeral joint but a range of about 45–60 ° of abduction can be achieved, entirely by scapular movement (Fig. 14.12A). There is, however, a full range of passive movement; and if the arm is abducted with assistance beyond 90° the patient can sustain the abduction by deltoid action (Fig. 14.12B). Thus the essential and characteristic feature in cases of torn supraspinatus tendon is inability to initiate gleno-humeral abduction. The usual explanation is that the early stages of abduction demand the combined action of the deltoid muscle, which supplies the main motive force, and the supraspinatus, which stabilises the humeral head in the glenoid fossa (like the workman’s foot against a ladder that is being raised from the ground).

Diagnosis. Complete tear of the rotator cuff must be distinguished from other causes of impaired gleno-humeral abduction, especially the painful arc syndrome and paralysis of the abductor muscles (as from poliomyelitis or nerve injury). Inability to initiate gleno-humeral abduction, with power to sustain abduction once the limb has been raised passively, is characteristic of a widely torn supraspinatus. In the painful arc syndrome the power of abduction is retained but the movement is painful.

Imaging. Examination by ultrasound scanning can identify a complete tear of the rotator cuff, but MR scans provide more detailed information on associated pathology in the surrounding structures (Fig. 14.13).

Fig. 14.13 Coronal T2 weighted MR scan of shoulder. There is a defect in the rotator cuff indicating a cuff tear (arrow). Most commonly this involves the supraspinatus tendon.

Treatment. In older patients operation should usually be avoided, because the degenerate state of the tendon makes satisfactory repair impracticable: the disability tends to become gradually less noticeable, and indeed the power of active abduction (by deltoid action alone) may sometimes be regained despite the persistence of a large tear.

In younger patients operation should be undertaken to repair both partial-thickness and full-thickness tears. As with other shoulder surgery this can be carried out as an open or an arthroscopic procedure depending on the experience of the surgeon. At the same operation it may be necessary to perform an acromioplasty to reduce impingement on the rotator cuff and to prevent repeat rupture. Thereafter passive movements may be begun within a few days but attempts to lift the arm actively should be deferred for 4 weeks, when provisional healing of the tendon may be expected to have occurred. The results of operation are not uniformly satisfactory, probably because of the poor quality of the degenerate tendon.

PAINFUL ARC SYNDROME (Supraspinatus syndrome)

This is a clinical syndrome characterised by pain in the shoulder and upper arm during the mid-range of gleno-humeral abduction, with freedom from pain at the extremes of the range. The syndrome is common to five distinct shoulder lesions.

Cause. The pain is produced mechanically by nipping of a tender structure between the tuberosity of the humerus and the acromion process and coraco-acromial ligament.

Pathology. Even in the normal shoulder, the clearance between the upper end of the humerus and the acromion process is small in the range of abduction between 45 and 160 °. If a swollen and tender structure is present beneath the acromion it is liable to get nipped during the arc of movement in which the clearance is small (Fig. 14.14A), with consequent pain. In the neutral position and in full abduction the clearance is greater and pain is less marked or absent (Figs 14.14B and 14.14C).

Fig. 14.14 Mechanical basis of the painful arc syndrome. The black spot represents any tender lesion near the supraspinatus insertion. A With the arm in mid-abduction the lesion is nipped between the humerus and the acromion. B With the arm dependent, the lesion is free from pressure. C At full elevation the lesion is again free from pressure.

Five primary lesions can give rise to the syndrome (Fig. 14.15). In general, though, these labels only represent variations of a process of degeneration which is the underlying defect.

Fig. 14.15 (Left) Five causes of the painful arc syndrome. The clinical features are the same in each. 1. Incomplete tear of supraspinatus. 2. Supraspinatus tendinitis. 3. Calcified deposit in supraspinatus. 4. Subacromial bursitis. 5. Crack fracture of greater tuberosity.

Clinical features. Whatever the primary cause, the clinical syndrome has the same general features, though they vary in degree. With the arm dependent pain is absent or minimal. During abduction of the arm pain begins at about 45 ° and persists through the arc of movement up to 160° (Fig. 14.16). Thereafter the pain lessens or disappears. In descent from full elevation pain is again experienced during the middle arc of the range: often the patient will twist or circumduct the arm grotesquely in an effort to get it down with the least pain. The severity of the pain varies from case to case. In cases of calcified deposit in the supraspinatus tendon the pain may be so intense that the patient is scarcely able to move the shoulder, or to sleep, and is driven to seek emergency treatment.

Fig. 14.16 (Right) Painful arc syndrome. The middle arc of abduction is painful whereas the extremes are painless.

Radiographic features. These vary with the underlying cause. Plain radiographs will reveal a fracture of the greater tuberosity or a calcified deposit (Fig. 14.17). A calcified deposit is distinguished radiologically from an avulsed fragment of bone by the fact that it is homogeneous and does not show the trabeculation characteristic of bone. MR scanning may demonstrate some of the other causes from degeneration and partial tears of the rotator cuff.

Fig. 14.17 Radiograph of shoulder showing calcification of the soft tissues above the greater tuberosity of the humerus (arrow). The calcified material usually lies within the supraspinatus tendon and is often associated with a painful tendinitis, but can be asymptomatic.

Diagnosis. Painful arc syndrome is sometimes confused with arthritis of the acromio-clavicular joint, which also causes pain during a certain phase of the abduction arc. But in acromio-clavicular arthritis the pain begins later in abduction (not below 90 °) and increases rather than diminishes as full elevation is reached.

Differentiation between the five primary causes of the syndrome is aided by the history and by radiography. A history of injury suggests a strain of the supraspinatus tendon or a lesion of the greater tuberosity, whereas a spontaneous onset suggests tendinitis, calcified deposit or subacromial bursitis. As noted, radiography will confirm or exclude a fracture or a calcified deposit (Fig. 14.17).

Treatment in the acute case. In mild cases treatment is often unnecessary, but when pain is more severe this may be required depending upon the primary cause of the syndrome.

Calcified deposit in supraspinatus tendon. If the pain is intense, as it sometimes is in these cases, relief can usually be gained by direct injection of hydrocortisone into the calcified deposit. If this fails the deposit of hydroxyapatite crystals may be dispersed with an aspiration needle followed by lavage of the subacromial space.

Contusion or crack fracture of greater tuberosity. Reliance should be placed on active use and mobilising exercises.

Strain of supraspinatus, supraspinatus tendinitis, and subacromial bursitis. Most of these cases respond gradually to physiotherapy in the form of ultrasound or interferential therapy, and mobilising exercises.

Treatment in the chronic case. In cases of painful arc syndrome in which severe symptoms persist despite a full trial of efficient conservative treatment, operation may be required. The procedure of acromioplasty excises the acromion process, or preferably its anterior third, together with the coraco-acromial ligament to prevent the possibility of further nipping of inflamed tissue between it and the upper end of the humerus. The operation can be carried out as either an open or closed arthroscopic procedure.

RUPTURE OF LONG TENDON OF BICEPS

The long tendon of the biceps is one of several tendons in the body that are prone to rupture without violent stress or injury. (Others are the supraspinatus tendon and the tendon of extensor pollicis longus.)

Cause. The tendon will not rupture under ordinary stresses unless it is already weak. The predisposing factor is age-degeneration, probably accelerated by oft-repeated friction and angulation at the point where the tendon enters the bicipital groove of the humerus.

Clinical features. The patient is usually a man past middle age. While lifting or pulling with the arm he feels something give way in the region of the front of the shoulder. There is only moderate discomfort, and often the patient neglects to seek early advice. Later he may notice an unusual bulge of the muscle in front of the arm.

On examination soon after the rupture, there is slight tenderness over the bicipital groove of the humerus. When the patient contracts the biceps muscle, as in flexing the elbow or supinating the forearm against resistance, the belly of the long head is seen to bunch up into a short round mass like a ball. There is surprisingly little weakness of elbow flexion or of supination.

Treatment. The disability is usually so slight that operation is not required. When repair is considered necessary, it is sufficient to produce a tenodesis by fixing the distal stump of the tendon to the walls of the bicipital groove. The proximal stump is ignored.

TENOSYNOVITIS OF LONG TENDON OF BICEPS (Biceps tendinitis)

This is an uncommon and rather minor affection characterised by pain and local tenderness in the region of the bicipital groove of the humerus and the long tendon of the biceps. It is generally ascribed to frictional irritation of the tendon within its groove, but it may be associated with degeneration of the tendons that form a cuff at the top of the shoulder.

Clinical features. The complaint is of pain in the front of the shoulder, worse on active use of the arm. Examination reveals local tenderness in the course of the long tendon of the biceps in the bicipital groove of the humerus. The pain can often be exacerbated by moving the shoulder while the tendon is made taut by forced supination of the forearm.

Treatment. Excessive use of the shoulder should be avoided. Physiotherapy by ultrasound, interferential therapy, or short-wave diathermy is worth a trial. Failing this, a local injection of hydrocortisone may be advised.

POLYMYALGIA RHEUMATICA

Polymyalgia rheumatica was described on page 166. It is worth mentioning again here because the soft tissues about the shoulders and the base of the neck are commonly the parts affected. The onset of this disorder of connective tissue is insidious, with aching pain and tenderness in the muscles of the shoulder girdle, neck, and spine, and severe ‘stiffness’ with substantial restriction of mobility of the shoulders, neck, and spine. There is also constitutional illness, with malaise, mild pyrexia, and night sweats, and elevation of the erythrocyte sedimentation rate. Early treatment by prednisolone in high doses should be advised if there is a suspicion of giant cell arteritis, pending confirmation of the diagnosis by biopsy.

OSTEOARTHRITIS OF THE ACROMIO-CLAVICULAR JOINT

Degenerative arthritis (osteoarthritis) of the acromio-clavicular joint is seen much more often than is osteoarthritis of the gleno-humeral joint. Pathologically, there are degeneration and attrition of articular cartilage, and spurs of bone (osteophytes) are formed at the joint margins.

Clinical features. There is pain, localised accurately to the acromio-clavicular joint and aggravated by strenuous use of the limb – especially in overhead work. On examination irregular bony thickening of the joint margins due to osteophytes may be felt. There is no soft-tissue thickening and no increase of local skin temperature. The total range of shoulder movements is not appreciably decreased, but pain in the region of the acromio-clavicular joint is exacerbated at the extremes of movement, especially on elevation of the arm towards the vertical: the arc of movement below 90 ° is painless, but above 90 ° pain develops and persists throughout the remainder of the arc to full elevation (compare painful arc syndrome, p. 268).

Imaging. Radiographs show features that are typical of osteoarthritis with narrowing of the cartilage space and marginal osteophytes. MR scans can provide more information on the extent of rotator cuff impingement in the sub-acromial space.

Treatment. Often treatment is not needed, other than modification of everyday activities. In severe cases operation is justified: it should take the form of excision of the lateral end of the clavicle with preservation of the conoid and trapezoid ligaments.

PERSISTENT ACROMIO-CLAVICULAR DISLOCATION OR SUBLUXATION

Persistent upward displacement of the lateral end of the clavicle is a common sequel to traumatic dislocation or subluxation of the acromio-clavicular joint. In most cases the displacement is slight and causes no symptoms, except perhaps for pain or discomfort during overhead work. Exceptionally there is pain, worse during full elevation of the arm. On examination the lateral end of the clavicle is unduly prominent, and a distinct step can be felt between it and the surface of the acromion.

Treatment. Usually treatment is unnecessary, but if disabling pain persists operation is advised. A simple and effective method to achieve pain relief is to excise the lateral end of the clavicle. However, in younger patients the resultant instability may be troublesome and it may be preferable to reconstruct the joint by coraco-acromial ligament transfer combined with internal fixation of the coraco-clavicular joint.

PERSISTENT OR RECURRENT DISLOCATION OF THE STERNO-CLAVICULAR JOINT

Forward dislocation of the medial end of the clavicle may be permanent, or it may recur on certain movements of the arm. Often, but not always, there is a history of precipitating injury. The symptoms are slight: there is a prominence in the region of the joint, with mild local pain. Recurrent displacement of the clavicle in and out of joint during movements of the arm may be an annoying disability. On examination the medial end of the clavicle, when displaced, is easily felt as a prominent forward projection. In recurrent dislocation the clavicle can be felt to click out of joint when the shoulders are braced back, and to go back into position when the shoulders are arched forwards.

Imaging. Radiographs reveal the displacement, when present. It is difficult to show the joint clearly on plane films and CT scanning may be necessary to provide fuller information.

Treatment. In many cases treatment is unnecessary, but operation is occasionally justified. The displacement is reduced and the clavicle is held in place by constructing a new retaining ligament from the tendon of the subclavius muscle or an autogenous semitendinosus tendon in a figure-of-eight configuration. Wire fixation must be avoided because of the risk of damage to the underlying major vessels.

DISORDERS OF THE BRACHIAL PLEXUS OR ITS ROOTS

The pain caused by pressure upon the brachial plexus or its roots is commonly attributed erroneously to an affection of the shoulder. Such pain varies in its precise distribution according to the site and nature of the nerve lesion. Usually it radiates from the base of the neck, across the top of the shoulder, and down the front, side, or back of the arm; thence it extends into the forearm, and often into the hand and fingers. Thus in its typical form the pain from a nerve lesion in the neck differs from the pain of a shoulder lesion, which typically does not extend below the elbow. The conditions which can result in brachial plexus symptoms are described in Chapter 12.

Affections that may cause referred symptoms in the distribution of the brachial plexus include prolapsed cervical intervertebral disc, osteoarthritis of the cervical spine, cervical rib, herpes zoster, and tumours involving the spinal cord or the component nerves of the brachial plexus.

DISORDERS OF THE UPPER ARM

Shoulder pain typically radiates distally and is often felt near the insertion of the deltoid muscle. Pain arising locally at this site, for instance from a lesion in the shaft of the humerus, may thus be confused with pain arising at the shoulder itself. Radiographs including the upper half of the humerus will usually help to make the distinction.

DISORDERS WITHIN THE THORAX

DISORDERS WITHIN THE ABDOMEN