Winged scapula

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Overview
Winged scapula is a condition in which the medial border (the side nearest the spine) of a person's scapula is abnormally positioned laterally and posteriorly (outward and backward). The resulting appearance of the upper back is said to be wing-like because the inferior angle of the shoulder blade protrudes backward rather than lying mostly flat like in people without the condition.

Causes
Although there are many causes of the condition, the most common is when the serratus anterior muscles are weakened (for various reasons) or when they are weakened and/or paralysed by impingement of the long thoracic nerve.

This lesion is also classically caused by denervation or damage to the trapezius muscle, which is much larger and stronger than the serratus anterior. Following damage to the serratus anterior muscle, however, it may take weeks for a winged scapula to develop, because the trapezius muscle must stretch before winging is apparent.

Presentation
The serratus anterior muscle attaches to the medial anterior aspect of the scapula (i.e. it attaches on the side closest to the spine and runs along the side of the scapula that faces the ribcage) and normally anchor the scapula against the rib cage. They also rotate the scapular upwards, allowing the arm to be raised above the head. They are innervated by the long thoracic nerve, so damage to or impingement of this nerve can result in weakening or paralysis of the muscle. This can then cause the scapula to slip away from the rib cage, giving it the wing-like appearance on the upper back. This sign can particularly be seen when the affected person pushes against resistance. The person may also have limited ability to lift their arm above their head.