4.12 Disorders of the scapula

When humans assumed the erect position, the shoulder evolved with the series of complex adaptive changes exchanging stability for mobility. In our amphibian ancestry the forelimbs evolved from the longitudinal lateral folds and pectoral fins. After the migration of spinal nerves and muscle buds, the nerve fibres repeatedly divided to form a plexus and different regions of muscle tissue often combined or segmented as function evolved. Cartilage rays called radicals arose between muscle buds to form a support structure, and the proximal portions of these radials coalesced to form basal cartilages, or basilia, of the primitive pectoral girdle. They migrated ventrally towards the midline anteriorly to form a ventral bar, the precursor of the paired clavicles, and projected dorsally over the thorax to form the precursor of the scapula. Articulations within the basilia developed at the junction of the ventral and dorsal segments. The basic mammalian pattern developed with articulations arising between a well-developed clavicle and sternum medially and a flat and fairly wide scapula laterally.

Four main variations of pectoral girdle are seen in mammals. Those adapted for running have lost their clavicle to mobilize the scapula further, and the scapula is relatively narrowed. Mammals adapted for swimming also lost their clavicle although the scapula is wider, permitting more varied function. The shoulder girdles modified for flying have a large, long, well-developed clavicle with a small, narrow, curved scapula. Finally, shoulders modified for brachiating (including humans) have developed a strong clavicle, a large coracoid process, and a widened strong scapula. Adaptations also seen in the erect posture were the relative flattening of the thorax in the anteroposterior dimension, leaving the scapula approximately 45 degrees to the midline and the evolution of the pentadactyl limb.

The limb buds, consisting of a core of mesenchyme and a covering layer of ectoderm, become visible at the beginning of the fifth week. By the sixth week of development the first hyaline cartilage models of the forelimb bones can be recognized, which will eventually form by endochondral ossification. An area, termed the interzone, which has not undergone chondrification is the precursor of the shoulder joint. The clavicle is the first bone in the body to begin to ossify. Subsequently the scapula, which at this time lies at the level of C4 and C5, also forms by intramembranous ossification. The interzone assumes a three-layer configuration, with a chondrogenic layer on either side of a loose layer of cells. At this time, the glenoid lip is discernible, although cavitation or joint formation has not occurred. The scapula undergoes marked enlargement at this time and extends from C4 to approximately T7.

Early in the seventh week the shoulder is well formed, with the middle zone of the three-layered interzone becoming progressively less dense with increasing cavitation. The scapula has now descended and spans from just below the level of the first rib and the fifth rib. The final few degrees of downward displacement occur later when the anterior rib cage drops obliquely downward. By the eighth week the upper limb musculature is well defined and the shoulder joint has the form of the adult glenohumeral joint.

The postnatal development of the shoulder is mainly concerned with the appearance and progress of the secondary sites of ossification. The scapula at birth has its body and spine ossified by intramembranous ossification. The coracoid process has two, and occasionally three, centres of ossification. The first appears during the first year of life at the centre of the process with the second arising around the age of 10 years at its base. These two centres unite with the scapula around age 15 years. The acromion has two ossification centres which arise during puberty and fuse together around age 22 years. Failure of this fusion produces an os acromiale and may be present in up to 4.2% of the population. The glenoid fossa has again two ossification centres. The first appears at the base of the coracoid process around age 10 years and fuses around age 15 years. The second centre is a horseshoe shape arising from the inferior portion of the glenoid during puberty and forms the lower three-quarters of the glenoid. The vertebral border and inferior angle of the scapula each have one ossification centre, both of which appear at puberty and fuse around age 22 years.

Congenital elevation of the scapula is a rare congenital deformity first described by Eulenberg in 1863. Sprengel (1891) recognized that the deformity was caused by failure of the scapula to descend. In this condition the scapula lies high in relation to the thoracic cage and is usually rotated and hypoplastic (Box 4.12.1).

The disability is dependent on the severity of the deformity. In mild cases, the scapula is only slightly elevated and is slightly smaller than normal with minimal loss of function. In the severe cases it creates an ugly deformity with widening of the base of the neck. Occasionally the scapula can be so elevated that it almost touches the occiput and the patient’s head is deviated towards the affected side. Abduction is decreased in these severe cases as the glenoid faces downwards.

Other congenital anomalies, such as scoliosis, cervical ribs, malformations of ribs, and anomalies of the cervical vertebrae (Klippel–Feil syndrome), are commonly present; rarely, one or more scapular muscles are partly or completely absent. Cervicothoracic spine and thoracic outlet radiographs are required to identify these structural changes particularly if surgical correction is considered. An omovertebral bone together with a very straight clavicle is found in between a third and half of patients.

Surgery is only indicated in severe deformities, after consideration of the age of the patient and the severity of any associated deformities. Corrective surgery is too major to consider before the age of 3 years. However, the earlier surgery is performed after this age the better are the results, because as the child grows the operation becomes more difficult and ultimately impossible. In children older than 8 years attempts to bring the scapula inferiorly to its normal level may seriously stretch and damage the brachial plexus. Limited resection of the prominent superomedial angle may be considered after this age. It must be made clear to the parents that the results of surgery are occasionally disappointing as the deformity is never simply elevation of the scapula alone, but always complicated by malformations and contractures of the soft tissues.

Numerous methods of lowering the scapula have been described to correct this deformity. Before addressing the scapula position, consideration should be given to morcellation of the clavicle on the ipsilateral side as in severe deformities it reduces the risk of brachial plexus palsy. Many techniques of lowering the scapula have been described.

Woodward (1961) described transfer of the origin of the trapezius muscle to a more inferior position on the spinous processes. This utilizes a more cosmetic midline approach from the spinous process of the first cervical to the ninth thoracic vertebra. The patient is placed prone and draped so that the shoulder girdle and arm can be moved freely. The skin and subcutaneous tissues are undermined laterally to the medial border of the scapula. The lateral border of the trapezius is identified distally and separated by blunt dissection from the underlying latissimus dorsi muscle. Then the fascial sheath of origin of the trapezius is released from the spinous processes by sharp dissection. The origins of the rhomboideus major and minor muscles are similarly freed and separated from the muscles of the chest wall. This sheet of muscles can be retracted laterally to expose any omovertebral bone or fibrous bands attached to the superior angle of the scapula. The omovertebral bone, any fibrous band, or contracted levator scapulae are freed, taking care not to injury the spinal accessory nerve, the nerves to the rhomboids, or the transverse cervical artery. The supraspinatus part of the scapula is usually deformed and should be excised with its periosteum thus releasing the levator scapulae. The scapula can be displaced inferiorly with the attached sheet of muscles distally until its spine lies at the same level as that of the opposite scapula. With the scapula in this position, the aponeuroses of the trapezius and rhomboids are reattached to the spinous processes at a more inferior level. Postoperatively a sling or Velpeau bandage is worn for 2 weeks.

An alternative and simpler method is to lower the scapula by osteotomy. The patient is placed semiprone with the affected side uppermost. A vertical incision is made over the medial border of the scapula. The scapula is exposed by incising the periosteum along the medial part of the origin of supraspinatus and infraspinatus, which can be swept laterally. An osteotomy is made 1cm from the vertebral border with an oscillating saw passing through the base of the spine (Figure 4.12.1). Mobility of the lateral part of the scapula is gained by removal of the medial strip of scapula above its spine. This also allows removal of fibrous bands and any omovertebral bone. Remaining fibrous bands on the inferior strip of medial scapula are also divided. The lateral part of the scapula can be protracted and lifted away from the chest wall so that a finger can be swept between subscapularis and the underlying ribs, ensuring that any adhesions or fibrous bands are divided. Once the blade of the scapula is completely mobile, the lateral portion is rotated downwards and stabilized with sutures passing through the periostium and bone to the remaining strip. This procedure requires a longer period of immobilization in a sling for 6 weeks.

The major complication following these procedures is the significant risk of brachial plexus palsy. This risk is higher in severe deformities particularly in the presence of a straight clavicle and deformed high first rib. The other recognized complication is damage to the spinal accessory nerve on the undersurface of the trapezius.

Stability of the scapula is of paramount importance to efficient shoulder function. Paralysis or weakness of the scapular stabilizing muscles causes profound loss of function

It is of note that although we use the terms protraction, retraction, and winging, there can be few joints in the human body whose movement is so poorly defined (Box 4.12.2). We do not even have proper terms of reference regarding the range of motion of the scapulothoracic joint; somewhat surprising when we observe the remarkable range of movement maintained in patients who have undergone a glenohumeral arthrodesis. Observations are often focused on scapulothoracic rhythm, disturbance of which is a useful finding but usually reflects pathology arising from the glenohumeral or subacromial articulations rather than the scapula or its control.

The trapezius and levator scapulae support the entire weight of the upper extremity in the erect position (Figure 4.12.2A). In addition to their suspensory role they participate in a complicated muscle couple controlling scapulothoracic movement. The upper fibres of the trapezius and levator scapulae pull cephalad, whilst the lower fibres of the trapezius, acting with the rhomboids and the latissimus dorsi, pull the arm backwards (Figure 4.12.2B), allowing the upper fibres of trapezius to rotate the scapula.

The major cause of trapezius palsy is injury to the spinal accessory nerve (Box 4.12.2). Although the dangers of iatrogenic injury cannot be overstressed, it is important to appreciate that this palsy is commonly seen when the nerve is sacrificed during radical neck dissection for malignant disease. The ensuing disability can be so great that preservation should be encouraged if at all possible. The disability may be compounded by using the levator scapulae muscle to cover the carotid artery during this procedure. Not only is it the only other suspensory muscle, but it is also of great importance in late reconstruction of the shoulder girdle.

The spinal accessory nerve is the major nerve supply to trapezius. It exits the base of skull through the jugular foramen and passes obliquely through the sternomastoid muscle in its upper third before crossing the posterior triangle of the neck to enter trapezius. As it lies very superficially, it is vulnerable to injury and is at risk with even the simplest surgical operation in the neck region. The injury is usually not recognized at the time of surgery and the diagnosis is often delayed until the patient describes inability to abduct the arm without pain. Some of the palsies are due to neurapraxia and recover spontaneously. Electromyographic examination may be of help but if there is no recovery by 10 weeks the nerve should be explored. If the nerve is found in continuity lying in scar tissue, neurolysis may be successful, but if there is obvious discontinuity then suture or grafting is necessary. Should the repair be unsuccessful or not possible, surgical reconstruction with muscle transfers should be considered.

Reconstruction is the only option in the post-radical neck resection patients. There is a marked contrast in the subjective perception of the condition between these patients and patients with iatrogenic injury to the nerve. Many do not wish to consider further surgery and have insufficient disability to require reconstruction. The degree of disability is extremely variable which may be partly due to the dual innervation from C2 and C3 (occasionally C3 and C4) in some patients. The indications are usually not precise and depend on the activity level, age, and life expectancy of the patient.

The cause of pain in these patients may be uncertain. It is important to try and ascertain the mechanism in order to plan treatment. Pain from neurologic denervation and adhesive capsulitis may be a factor in the early phase. Ptosis of the scapula may cause discomfort by a brachial plexus traction radiculitis. More commonly the pain appears to be due to fatigue and functional impingement (Figure 4.12.3).

The procedures to restore the function of the scapulothoracic articulation must address not only the winging, but also the ptosis due to loss of the scapular suspension mechanism. The complex nature of force couples makes substitution of even one muscle acting in a single plane difficult. The Eden–Lange tendon transfer of levator scapulae and the rhomboids (Figure 4.12.4A) is probably best for near-normal. These three muscles are used to replace the upper, middle, and lower portions of the trapezius respectively.

The alternative procedures, originally used in patients with facial nerve paralysis in which the spinal accessory nerve was used as a motor for the facial muscles, have significant disadvantages. Dewar and Harris (1950) transferred the levator scapulae insertion laterally to substitute for the upper trapezius, and used a fascial sling in place of middle and lower parts of trapezius (Figure 4.12.4B). The slings were passed from the vertebral border of the scapula to the spinous processes of the second and third thoracic vertebrae. Unfortunately, these slings used in this procedure and the many variations described tend to stretch with time. If soft-tissue reconstruction fails, the only other option is limited to scapulothoracic fusion. This procedure has also been suggested as an option as a primary procedure in cases where heavy demands are anticipated. Conservative treatment has not been found successful other than treating concomitant adhesive capsulitis.

On elevation of the arm as the upper fibres of trapezius rotate the scapula, the serratus anterior assists by rotating the scapula forwards and maintaining the vertebral border of the scapula in firm apposition with the chest wall in all positions (Figures 4.12.2 and 4.12.3). Paralysis of this muscle may limit active elevation, but more frequently presents as deformity with fatigue pain on elevation of the arm. The fine tuning of scapula movement is of paramount importance in shoulder performance. In many vigorous shoulder activities the scapula is positioned so that the glenoid centre line and axis of the humeral head are closely aligned, for example, in a boxer’s punch, bench press, throwing action, and tennis shot. It is easy to demonstrate the effect of fatigue if the glenoid centre line and humerus are not aligned. Try maintaining the arm or lifting an object with the scapula deliberately retracted. With the scapula correctly protracted, the glenohumeral joint stabilizes with ease, making more muscle action available for power.

Long thoracic nerve palsy is the major cause of serratus anterior weakness. This nerve is formed from the roots of C5, C6, and C7 immediately after leaving their intervertebral foramina. It runs collaterally to the main brachial plexus and is often spared in traction lesions. The cause of long thoracic nerve palsy is often difficult to explain, but may follow viral illness, carrying objects on the shoulder, open iatrogenic injury in the axilla, lying on the operating table, and long periods of anaesthesia. It is also described after recumbency for a prolonged period of time and immunization, but these causes are rarely encountered in clinical practice. Kauppila and Vastamäki (1995) presented 27 cases of iatrogenic causes. These occurred during seven operations for first rib resection, four mastectomies with axillary clearance, two scalenotomies, two surgical procedures for spontaneous pneumothorax, and two infraclavicular plexus anaesthetic blocks. Nine occurred after general anaesthesia and one after spinal anaesthesia. Only one of these cases recovered spontaneously.

Palsies occurring after closed trauma are usually traction lesions and spontaneous recovery can be anticipated. Recovery is usually seen by 1 year. After this time the prognosis is poor, although some cases may still recover at 2–3 years.

The major problem is pain with difficulty in lifting the arm and lifting weights (Figure 4.12.5). Discomfort from the prominent scapula when sitting against a chair back is common. The shoulder may also be painful as a consequence of functional impingement within the subacromial space. There is little useful treatment; braces are uncomfortable and rarely tolerated, but may be of value in selected patients required to lift at work. Many patients learn to live with the disability and thus few come to surgery. There is no place for nerve repair and the only option is surgical reconstruction. Pectoralis major transfer with a fascia lata graft to the lower pole of scapula gives gratifying results (Figure 4.12.6).

Generalized weakness of the scapular stabilizers is commonly seen with many injuries and conditions affecting the shoulder. Careful examination will often demonstrate minor winging even in the absence of stiffness of the glenohumeral joint. When the weakness is severe, the imbalance as a consequence of relatively greater strength of deltoid pulling up the scapula causes winging on elevation of the arm. Duchenne showed this mechanism of winging of the scapula in his treatise Physiology of Motion (Figure 4.12.7). This is the situation in muscular dystrophies affecting the muscles of the scapula.

Muscle dystrophies should be suspected in cases of atraumatic onset of weakness and atrophy occurring in first and second decade. The most common type is fascioscapulohumeral dystrophy (FSHD; Landouzy–Déjerine disease) (Box 4.12.4). A positive family history is common, as this is an autosomal dominant condition with sporadic cases appearing very occasionally. Recent genetic linkage studies have mapped the FSHD gene to chromosome 4q35. On presentation it is usually unilateral, with the other side not developing until months or even years later. Involvement of the facial muscle may be detected early, with the child’s inability to whistle or blow out candles on the birthday cake. This condition has a variable muscle involvement and prognosis. There is usually good life expectancy and slow deterioration. The deltoid is spared but loses its stable origin and tilts the scapula rather than raising the humerus. The cosmetic appearance due to the selective muscle loss is characteristic and may cause difficulty with clothing (Figure 4.12.8).

In this condition, muscle involvement is global, precluding muscle transfer. If the function of the deltoid muscle is preserved and the disability is severe, scapulothoracic fusion should be considered. This operation recreates the stable origin by anchoring the scapula to the fourth, fifth, and sixth ribs. This procedure was described by Copeland and Howard in 1978. There are many technical variations performed but the principles remain the same. The results in 11 shoulders were reported with an average range of 90 degrees of flexion and 100 degrees of abduction. There was no deterioration with time and the vital capacity was preserved. The most frequent complication reported is stress fracture, which is treated by immobilization in a sling.

The patient is initially placed supine to harvest sufficient corticocancellous bone graft from the iliac crest. The patient is then moved into the prone position with the arm free and supported on an adjustable stool.

An incision is made along the medial border of the scapula. The atrophied muscles on the deep and superficial surfaces of the scapula are stripped laterally for at least 2cm. The subjacent three ribs (usually the fourth, fifth, and sixth) are exposed by subperiosteal dissection. Retractors are placed under the ribs to protect the pleura. Corticocancellous grafts are placed between each rib and the scapula. Three to four screws are inserted taking care that they do not protrude into the pleura. Chips of bone are packed between the grafts. The shoulder should be fused and held in 50 degrees of abduction and 30 degrees of forward flexion with sufficient internal rotation to place the hand in front of the mouth.

A spica cast or shoulder brace is worn for 3 months. The abduction is reduced slowly over a week by adjusting the brace or replacing the spica with foam wedges.

An alternative method of fixation is with Luque wires through drill holes in the scapula. A pelvic reconstruction plate on the posterior surface can be incorporated to increase the strength of fixation. This method allows early mobilization and a sling rather than a spica.

The ligamentous structures, that is, the conoid and trapezoid parts of the coracoclavicular ligaments, are important static suspensory structures and constraints to scapular movement. They not only prevent the scapula from dropping but also prevent posterior displacement of the clavicle and protraction of the scapula (Figure 4.12.1).

An injury commonly not recognized is described by Rockwood and Matsen and termed ‘scapulothoracic dissociation’. This results from violent lateral displacement of the scapula causing disruption of the soft tissues with separation of the acromioclavicular joint or fracture of the clavicle. Vessel or brachial plexus damage may occur with these injuries. There is also a more discrete type of injury in which there is stretching of the scapular stabilizers usually associated with type IV acromioclavicular joint separations and displaced clavicular fractures, particularly those of the lateral third. The increased distance from spinous processes to medial border of scapula can be appreciated on clinical examination or on the chest radiograph. Similarly, protraction of the scapula with soft-tissue stretching is seen with malunion and non-union of the clavicle. The protraction and winging can be accentuated by resisted external rotation with the arm by its side.

Restoration of the skeletal injury even with repair of the disrupted ligaments may be insufficient to correct the deformity, and specific rehabilitation of the scapular muscles must be stressed.

Obligatory winging is seen following glenohumeral fusion. This is rarely of significance, with the exception of arthrodesis for brachial plexus injury. In some cases of C5 and C6 root avulsion, the upper part of serratus anterior may be denervated. This should be assessed prior to surgery.

Injuries to the upper roots of the brachial plexus during childbirth may also cause winging of the scapula. Anterior contracture and capsular tightness develops with posterior subluxation of the humeral head and stretching of the posterior capsule. The glenohumeral joint becomes fixed in abduction, so that when the shoulder is forced into adduction and external rotation, superior winging due to the contracture occurs—known as the scapular sign of Putti.

An abduction contracture of deltoid may cause secondary winging. This is not so rare and many cases are reported, so it should be looked for in clinical practice. It is often bilateral and usually affects the anterior part of deltoid. Two types occur; congenital or secondary to multiple intramuscular injections. The treatment is by release of fibrous bands and manipulation. A defect in deltoid may result and require closure by transfer of posterior deltoid anteriorly. Displacement of the scapula and pseudowinging may be seen with large subscapular osteochondromas.

Rowe (1988) described four patients with voluntary winging. A more common appearance of winging is seen in cases of habitual or voluntary glenohumeral instability. In this situation the ability to sublux the shoulder requires winging of the scapula to destabilize the glenohumeral joint. The role of the scapula in this poorly understood condition is well demonstrated by observing the persistent muscle activity of the muscles controlling the scapulothoracic movement after brachial plexus anaesthesia blocked in patients with severe dysfunction. The importance of addressing the task of re-educating these muscles is apparent.

Presentation with a tactile and acoustic clunk localized at the superomedial corner of the scapula is not infrequent. This phenomenon, termed a snapping scapula, is usually encountered in the third decade and normally only requires treatment if painful (Box 4.12.5).

A variety of causes have been reported but the condition remains poorly understood. A history of trauma is not uncommon, but fractures of the scapula and ribs are extremely rare causes. More commonly the onset is gradual. A prominent Luschka’s tubercle, excessive forward curvature of the superomedial border, exostoses, or tumours are potential skeletal causes. These identifiable causes are comparatively rare and the majority of patients present with poor posture with sagging of the shoulder girdle such that the superomedial corner descends and impinges on the chest wall.

Plain radiographs, including a carefully positioned lateral view, will exclude an exostosis or obvious bony cause. Computed tomography is of limited value and difficult to interpret. Occasionally narrowing between the superomedial corner and the chest wall can be demonstrated in comparison to the contralateral side. Magnetic resonance imaging has little place, with the exception of defining the rare cases of tumor.

The treatment is usually non-operative; careful assessment and correction of abnormal posture is essential. The snapping or grating often disappears when the scapula is passively elevated and retracted. This can be demonstrated to the patient and is helpful in increasing the patient’s understanding of the rehabilitation programme. Before abandoning these measures in favour of surgery it is important to consider the natural history and the not infrequent association with psychological stress. It is interesting to note that very few cases fail to resolve with time. However, this can be a disabling condition and can be relieved by surgical resection of the superomedial scapula. Some authors advocate arthroscopic resection, but since the surgical landmarks are few, and important nerves are close by, this technique should be left to a few superspecialists.