The scapula (shoulder blade) is a flat, triangular bone that rests against the back of the rib cage.
On its outer side it has a shallow socket (the glenoid) that articulates with the head of the humerus. It also has two important projections: the scapular spine, which ends in the acromion, and the coracoid process at the front.
Normal movement of the scapula includes elevation and forward tilting, movements achieved through the coordinated action of several muscles of the back and shoulder. Abnormal function of any one of these muscles causes the scapula to deviate from its normal position and restricts shoulder movement.
What is normal scapulothoracic movement?
Shoulder movement requires not only movement of the glenohumeral joint but also of the scapulothoracic joint. Normal movement of the scapula allows patients to use their shoulder at work and in their daily and sporting activities.
What are the abnormal patterns of scapulothoracic movement?
When the muscles are unable to control the movement of the scapula, this leads to scapulothoracic dysfunction or dyskinesis, as a result of fatigue of the scapular stabilising muscles after certain sports or activities.
Indeed, athletes who report shoulder pain often have abnormal scapular movement, and a physiotherapy programme is an important part of their rehabilitation. In its most severe form, scapulothoracic dyskinesis is the result of nerve dysfunction, either due to injury or idiopathic (of unknown cause).
Diagnosis
Loss of scapular control is often underdiagnosed (it is “missed” by the doctor). The patient may develop pain, with possible loss of the normal range of shoulder movement. In some cases, instability of the glenohumeral joint may develop because the scapula cannot move in all directions.
Normal movement of the scapula provides a stable base for the head of the humerus and is achieved through the coordinated action of several muscles of the back and shoulder. If the scapula cannot move outwards and forwards, this can lead to shoulder instability.
Clinically, the assessment of abnormal scapular movement begins with inspection of both shoulders. Diagnosis is not difficult, as the scapula may sit lower than normal and lift away from the back of the chest wall. Some patients report pain that can mimic rotator cuff problems. This is caused by the tendons striking the acromion (impingement), which the scapular muscles normally prevent by rotating the scapula upwards so that the arm can be raised freely. More specifically, because of weakness of the serratus anterior muscle, the scapula cannot rotate, resulting in impingement and irritation of the rotator cuff.
Classification – are there different types of winged scapula?
- Medial winging of the scapula: This is caused by poor function of the serratus anterior muscle, due to palsy of the long thoracic nerve, resulting in the inner (medial) border of the scapula shifting inwards and upwards.
The serratus anterior is a powerful muscle that arises from the ribs and attaches to the inner border of the scapula. When the muscle is not working properly, it loses the ability to control the scapula. Severe forms of winged scapula are caused by injury to the long thoracic nerve, which supplies the serratus anterior muscle.
The nerve can be injured by excessive stretching or compression in the neck or chest area from a road traffic accident or other trauma. Sometimes, when no clear cause is found, it is thought that it may be due to a viral infection of the nerve. The diagnosis is usually confirmed by electromyography (EMG) studies carried out by experienced staff.
- Lateral winging of the scapula: This is caused by poor function of the trapezius muscle, due to palsy of the spinal accessory nerve, resulting in the outer (lateral) border of the scapula shifting outwards and downwards. The trapezius is a large triangular muscle, supplied by the spinal accessory nerve, which holds the scapula in place and rotates it outwards and upwards to help raise the arm. It is usually caused by injury to the spinal accessory nerve as a result of a direct blow, as in a road traffic accident, a wound from a sharp object, or iatrogenically, after a lymph node biopsy in the neck.
- Some rarer causes of winged scapula include combined palsy of the scapular stabilising muscles, brachial plexus palsy and chronic shoulder instability, either from repeated dislocations or from injury to the ligaments of the acromioclavicular joint.
Treatment
In most cases the condition is treated conservatively, with rest and physiotherapy. However, surgical treatment has specific indications and is used in a small number of patients.
In long thoracic nerve palsy, recovery is slow and can take one to two years.
More recent studies recommend early surgical exploration, although without clear results. When the nerve palsy does not recover, the most common solution is a pectoralis major tendon transfer, with good results in terms of pain relief and restoration of shoulder function.
In spinal accessory nerve palsy that does not recover, patients learn to live with the problem. If, however, it causes a high degree of dysfunction and pain, the Eden-Lange tendon transfer is recommended; it involves several muscles (levator scapulae, rhomboid major and rhomboid minor) and gives good results in terms of pain and function.
In the rare cases where tendon transfers fail, scapulothoracic fusion is performed using a plate and wire, giving the scapula stability for shoulder movement.
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