CHAPTER 4 The shoulder
Anatomical Features
Fig. 4.A. The shoulder is complex, and it is important to note that it has two main components, namely the glenohumeral joint (between the head of the humerus and the glenoid) and the scapulothoracic joint (between the scapula and the chest wall). The latter is a physiological rather than an anatomical joint, as it has no synovial cavity.
The glenohumeral joint accounts for about half of shoulder abduction (1), and this comes to an end when the greater tuberosity (2) impinges on the glenoid rim (3); the range of glenohumeral movement (about 90°) can be increased if the arm is externally rotated (4), thereby delaying the impingement of the greater tuberosity. Note that shoulder rotation occurs mainly in the glenohumeral joint.
Fig. 4.B. In the scapulothoracic joint the scapula (S), moves over the rib cage and serratus anterior. It is supported by the clavicle (C) (which articulates with the scapula at the acromioclavicular joint (AC), and with the sternum at the sternoclavicular joint (SC)), and by trapezius, rhomboids, levator scapulae and serratus anterior. The inferior angle of the scapula normally lies at the level of D7.
Fig. 4.C. The scapula, however, is normally a very mobile structure, varying in its position and permitting a wide range of scapulothoracic movements. The scapula may be elevated (e) or depressed (d), with a maximal total excursion in the order of 12 cm. (Note that elevation of the shoulder is a pure scapulothoracic movement, and must be distinguished from elevation of the arm. The latter term enjoys some popularity as a replacement for abduction or flexion, but because it is somewhat confusing it is probably best avoided.) The scapula may be rotated medially, or laterally and forwards (m, l) round the chest wall. It may also be tilted upwards (u) or downwards, with the glenoid angling in a corresponding fashion. When the glenoid is directed upwards, the angle between the vertebral border of the scapula and the vertical may reach 60°. Scapular movement is only possible if there is freedom at the acromioclavicular and sternoclavicular joints, and between the scapula and the chest wall.
Fig. 4.D. Abduction of the shoulder (1):
During the first 90° of abduction the glenohumeral joint is involved more than the scapula (a), whereas beyond 90° abduction is continued mainly by scapular movement (b). During the last 30° of abduction, when the glenohumeral joint is locked and the scapular attachments are tightening, movements of the spine may make a contribution: e.g. abduction of the shoulder may lead to some lateral flexion of the thoracic spine (T). The cervical spine may also laterally flex to the other side, to preserve the posture of the head. When both arms are abducted, neither the thoracic nor the cervical spine laterally flexes, but there may be an increase in lumbar lordosis.
The deltoid muscle (d) arises from the lateral end of the clavicle, the acromion and the spine of the scapula; it is attached to the deltoid tubercle of the humerus. When the arm is at the side, the deltoid acting alone is incapable of initiating abduction: its contraction tends to raise the head of the humerus relative to the glenoid. On the other hand, when the arm is at the side the supraspinatus (s) is in its position of greatest mechanical advantage; with deltoid it forms a couple and initiates abduction (which is then taken over by deltoid). A tear of the supraspinatus (or relevant part of the shoulder cuff) will prevent the normal initiation of abduction, which will then only be possible by trick movements. (b = subdeltoid bursa)
In spite of the tendency for glenohumeral and scapular movements to dominate specific portions of the abduction arc, it should be noted that there is no abrupt transition from one to the other, and indeed all the shoulder girdle joints make a contribution to nearly every movement that takes place in this region. The exceptions are shrugging movements, which do not involve the glenohumeral joint, and external rotation, which does not involve scapular movement.
The shoulder cuff: The glenoid (g) is widest inferiorly. Anteriorly lies the coracoid (co), and above is the supraglenoid tubercle (sg), from which the long head of biceps (b) arises. The fibrocartilaginous labrum (l) deepens the glenoid concavity and is attached to its peripheral margin, along with the joint capsule (c). The capsule is reinforced with the musculotendinous insertions of supraspinatus (s), subscapularis (sc), infraspinatus (i) and teres minor (t), which fuse with the capsule laterally, forming a complete tissue annulus (the shoulder cuff). The supraspinatus is its most important part. This in effect runs through a tunnel formed by the spine of the scapula (ss), the acromion (a), and the coracoacromial ligament (ca). It is partly separated from the acromion by the subdeltoid bursa (b).
Common Pathology around the Shoulder
The commonest cause of shoulder pain is cervical spondylosis. Pain from irritation of nerve roots in the neck is referred to the shoulder in the same way as pain originating in the lumbar spine may be referred to the hip. There may on occasion be simultaneous pathology in both shoulder and neck, but differentiation is usually straightforward; in particular, restriction of movements of the shoulder with pain at the extremes points to the shoulder as the site of the principal pathology.
Impingement Syndrome
The rotator cuff (and the subdeltoid bursa) may be compressed during glenohumeral movement, giving rise to pain and disturbance of scapulothoracic rhythm. The commonest site is subacromial, causing a painful arc of movement between 70° and 120° abduction. Compression may also occur beneath the acromioclavicular joint itself, when there may be a painful arc of movement during the last 30° of abduction, or deep to the coracoacromial ligament. Symptoms may occur acutely (e.g. in young sportsmen, especially those engaging in activities involving throwing) or be chronic, particularly in the older patient. In this latter group there are usually degenerative changes in the acromioclavicular joint which lead to a reduction in size of the supraspinatus tunnel; this may cause attrition and rupture of the shoulder cuff.
There is a small group of cases where there is no narrowing of the tunnel, but where there is often thickening of the subdeltoid bursa or of the rotator cuff tendons. Note also that severe shoulder pain may occur in patients being dialysed, and is often due to subacromial impingement on amyloid deposits.
In the acute case, symptoms generally respond to rest or modification of activities. In the chronic case, physiotherapy, analgesics, and the targeted injection of local anaesthetic and steroids may be helpful. If symptoms become persistent and remain disabling, surgery may be required. The commonest procedure (by open surgery or by arthroscopy) is a decompression of the subacromial space; this may involve excision of osteophytes, an AC joint arthroplasty, and excision of the coracoacromial ligament.
Rotator Cuff Tears
In the young athletic patient the shoulder cuff may be torn as the result of a violent traumatic incident. In the older patient tears may occur spontaneously (e.g. in a cuff weakened as a result of chronic impingement and attrition) or follow more minor trauma, such as sudden arm traction. It may occur in patients suffering from instability of the shoulder joint.
Most commonly the supraspinatus region is involved, and the patient has difficulty in initiating abduction of the arm. In other cases the torn shoulder cuff impinges on the acromion during abduction, giving rise to a painful arc of movement. Although the range of passive movements is not initially disturbed, limitation of rotation may supervene, so that many of these cases, particularly in older patients, become ultimately indistinguishable from those suffering from so-called frozen shoulder. In the young patient, surgical repair of acute tears is generally advised. In the older patient the indications for surgery are less clear, but operative repair, often combined with a decompression procedure, is becoming increasingly recommended. Arthroscopic repair may be performed, although it is technically demanding. In every case, prolonged postoperative physiotherapy is usually required.
Rotator Cuff Arthropathy
If complete rotator cuff tears are neglected, the loss of soft tissue above the head of the humerus may lead to its proximal migration. Friction between the humeral head and the acromion may result in bony collapse and gross degenerative changes in the glenohumeral joint, which in severe cases may lead to joint replacement having to be considered.
‘Frozen Shoulder’/Idiopathic Adhesive Capsulitis of the Shoulder
‘Frozen shoulder’ is a clinical syndrome characterised by gross restriction of shoulder movements and which is associated with contraction and thickening of the joint capsule. It is a condition that affects the middle-aged, in whose shoulder cuffs degenerative changes are occurring. Restriction of movements is often severe, with virtually no glenohumeral movements possible, but in the milder cases rotation, especially internal rotation, is primarily affected. Pain is often severe and may disturb sleep. There is frequently (but not always) a history of a minor trauma, which is usually presumed to produce some tearing of the degenerating shoulder cuff, thereby initiating the low-grade prolonged inflammatory changes and contraction of the shoulder cuff responsible for the symptoms. In a number of cases there are fibrotic changes in the coracohumeral ligament which resemble those found in Dupuytren’s disease. In some cases the condition is initiated by a period of immobilisation of the arm, not uncommonly as the result of the inadvised prolonged use of a sling after a Colles’ fracture. It is commoner on the left side, and in an appreciable number of cases there is a preceding episode of a silent or overt cardiac infarct. It is commoner in diabetics. Radiographs of the shoulder are almost always normal. If untreated, pain subsides after many months, but there may be permanent restriction of movements. Generally those with the most severe initial symptoms have the poorest outcome in terms of final mobility and overall function.
The main aim of treatment is to improve the final range of movements in the shoulder, and graduated shoulder exercises are the mainstay of treatment. In some cases where pain is a particular problem, hydrocortisone injections into the shoulder cuff may be helpful. In a few cases, if there is no improvement with appropriate treatment for 4 months, manipulation of the shoulder under general anaesthesia or athroscopic capsular release may be helpful in restoring movements in a stiff joint.
Calcifying Supraspinatus Tendinitis
Degenerative changes in the shoulder cuff may be accompanied by the local deposition of calcium salts. This process may continue without symptoms, although radiographic changes are obvious. Sometimes, however, the calcified material may give rise to inflammatory changes in the subdeltoid bursa. Sudden, severe incapacitating pain results; the shoulder becomes acutely tender, and is often swollen and warm to the touch. It is important to differentiate the condition from an acute infection, or an acute attack of gout. Symptoms are relieved by the removal of the material by aspiration, curettage, or shock-wave therapy, but often local injections of hydrocortisone suffice. Note that the joint is frequently so acutely tender that general anaesthesia is necessary for any attempted aspiration and injection of hydrocortisone. Ultrasound-guided needling in combination with high-energy shock-wave therapy is more effective than shock-wave therapy alone, giving better elimination of the deposits, better clinical results and lesser need for surgery.
Osteoarthritis of the Acromioclavicular Joint
Arthritic changes in the acromioclavicular joint may give rise to prolonged pain associated with shoulder movements (with or without shoulder cuff involvement and the production of an impingement syndrome). There is usually an obvious prominence of the joint from arthritic lipping, with well localised tenderness. Conservative treatment with local heat and exercises may be helpful, but occasionally, in severe persistent cases, acromionectomy may be considered.
Osteoarthritis of the Glenohumeral Joint
Osteoarthritis of the glenohumeral joint is rare, and when it occurs is most frequently secondary to avascular necrosis of the humeral head. This may be idiopathic in origin, or follow a fracture of the proximal humerus which interferes with the blood supply of its head. It may result from faulty decompression regimens in deep-sea divers, caisson workers and pilots, and it may follow radiotherapy (radionecrosis), particularly following treatment for carcinoma of the breast. If empirical treatment fails, joint replacement may have to be considered.
Rheumatoid Arthritis of the Shoulder
Rheumatoid arthritis is more common than osteoarthritis in the shoulder, and the features are similar to those of the condition in other joints. It is necessary to localise the site of the main pathology so that treatment may be directed effectively, and diagnostic sequential injections (into the acromioclavicular joint, the shoulder cuff, and then the glenohumeral joint) may be helpful in this respect. Medical treatment and intra-articular injection therapy are tried first. In more advanced cases, where the symptoms are the result of impingement, decompression procedures may be highly effective. Where the glenohumeral joint is severely diseased, joint replacement will generally produce pain relief and improved function.
Instabilities of the Shoulder Joint
Recurrent Dislocation of the Shoulder
The shoulder may be affected by anterior, posterior or inferior instability. When the shoulder is unstable in several planes, then multidirectional instability (‘loose shoulder’) is said to be present.
Anterior instability is the commonest, and in many cases this follows a frank dislocation of the shoulder. It occurs most frequently in the 20–40-year age group. There may be a history of repeated dislocations in which the causal trauma has become progressively less severe (recurrent anterior dislocation of the shoulder). The shoulder is often symptom free between incidents, but there may be some pain and weakness. Surgical repair is generally advised if there have been four or more dislocations, but each case must be carefully assessed to exclude shoulder laxity in other planes: many case of failed reconstruction are due to an associated posterior instability.
Trauma to the shoulder may also result in posterior dislocation, which can proceed to recurrent posterior dislocation. Posterior dislocation of the shoulder is much less common than anterior dislocation and the diagnosis is sometimes overlooked, especially when only one radiographic projection is taken. Surgical reconstruction is sometimes required, but this may fail if concurrent anterior instability is not taken into account.
Anterior and multidirectional instabilities may occur without previous trauma, and never proceed to frank dislocations or obvious subluxations. The condition may be congenital in origin. The primary complaints are of pain and weakness in the shoulder, and the rapid onset of joint fatigue during activity. The arm may feel ‘dead’. In the case of multidirectional instabilities muscle retraining is generally advocated, although surgical reconstruction is sometimes attempted.
Recurrent dislocation of the shoulder should be differentiated from habitual dislocation. In the latter the patient is often psychotic or suffering from a joint laxity syndrome. The shoulder repeatedly dislocates without much in the way of pain; the patient is often able to dislocate and reduce the shoulder voluntarily and with ease; and the radiological changes that are found in recurrent dislocation are not present in habitual dislocation. When habitual dislocation is found in children the prognosis is good, and surgery is never indicated. In the adult, surgery is usually best avoided (as the results are often poor), but good results are being claimed for biofeedback re-education of the shoulder muscles.
Infections around the Shoulder
Staphylococcal osteitis of the proximal humerus is the commonest infection occurring near the shoulder in this country at present; nevertheless, it is comparatively uncommon.
Tuberculosis of the shoulder is now rare. In the moist form, commonest in the first two decades of life, the shoulder is swollen, there is abundant pus production, and sinuses may form; the progress is comparatively rapid and destructive. In the dry form, caries sicca, an older age group is affected and the progress is slow, with little destruction or pus formation. (However, it should be noted that it is now thought that many of the cases of caries sicca described in the past were in fact suffering from frozen shoulder.)
Gonococcal arthritis of the shoulder is uncommon, but when it occurs there is moderate swelling of the joint and great pain, which often seems out of keeping with the physical signs.
Miscellaneous Conditions around the Shoulder
Acromioclavicular dislocation
The acromioclavicular joint may be disturbed as a result of a fall on the outstretched hand or on the point of the shoulder. If care is taken during examination, a lesion of this joint will not be confused with one of the glenohumeral joint. In major injuries the conoid and trapezoid ligaments are torn and the clavicle is very unstable: surgical fixation of the clavicle to the coronoid (by a screw or a sling procedure) is sometimes advised. In less severe cases the acromioclavicular capsular ligaments only are torn. Although the outer end of the clavicle becomes prominent, it follows the movement of the acromion and conservative treatment with a sling for several weeks is all that is required. These injuries are frequently missed, as they often do not show in the routine recumbent radiographs of the shoulder.
Clavicle
Primary pathology in the clavicle is uncommon, but a cause of confusion is pathological fracture due to radionecrosis years after treatment for breast carcinoma. The fracture may be preceded by pain for many months, and be mistaken for metastatic spread.
Scapula
Snapping scapula
A patient may complain of a grinding sensation arising from beneath the scapula. This is often due to a rib prominence, but in some cases it may be caused by an exostosis arising from the deep surface of the scapula itself. When symptoms are persistent, excision of such an exostosis may give relief.
High scapula
There are several related congenital malformations affecting the neck and shoulder girdle. In the most minor cases one scapula may be a little smaller than the other and be more highly placed; in more severe cases one or both shoulders are highly situated, the scapulae are small, and there may be webs of skin running from the shoulder to the neck (Sprengel shoulder). In the Klippel–Feil syndrome the neck is short and there are multiple anomalies of the cervical vertebrae, which may include vertebral body fusions and spina bifida. Apart from highly placed scapulae, other congenital lesions may be found in association with the Klippel–Feil syndrome; these include diastomatomyelia resulting in tethering of the spinal cord and neurological involvement; lumbosacral lipomata; and renal abnormalities.
