<P> In most cases of winged scapula, damage to the serratus anterior muscle causes the deformation of the back . 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 anchors the scapula against the rib cage . When the serratus anterior contracts, upward rotation, abduction, and weak elevation of the scapula occurs, allowing the arm to be raised above the head . The long thoracic nerve innervates the serratus anterior; therefore, damage to or impingement of this nerve can result in weakening or paralysis of the muscle . If this occurs, the scapula may slip away from the rib cage, giving it the wing - like appearance on the upper back . This characteristic may particularly be seen when the affected person pushes against resistance . The person may also have limited ability to lift their arm above their head . </P> <P> In facioscapulohumeral muscular dystrophy (FSH), the winged scapula is detected during contraction of the glenohumeral joint . In this movement, the glenohumeral joint atypically and concurrently abducts and the scapula internally rotates . </P> <P> The most common cause of scapular winging is serratus anterior paralysis . This is typically caused by damage (i.e. lesions) to the long thoracic nerve . This nerve supplies the serratus anterior, which is located on the side of the thorax and acts to pull the scapula forward . Serratus anterior palsy is a dysfunction that is characteristic of traumatic, non-traumatic, and idiopathic injury to the long thoracic nerve . Severe atrophy of the trapezius is seen with accidental damage to the spinal accessory nerve during lymph node biopsy of the neck . There are numerous ways in which the long thoracic nerve can sustain trauma - induced injury . These include, but are not limited to, blunt trauma (e.g. blow to the neck or shoulder, sudden depression of the shoulder girdle, unusual twisting of the neck and shoulder), repetitive movements (as observed in athletic activities such as weight lifting or sports that involve throwing), excessive compression of the shoulder area by straps (see backpack palsy), and various household activities (e.g. gardening, digging, car washing, prolonged abduction of the arms when sleeping, propping up the head to read, etc .). Sometimes, other structures in the body such as inflamed and enlarged subcorocoid or subscapular bursa press on the nerve . Clinical treatments may also cause injury to the long thoracic nerve (iatrogenesis from forceful manipulation, mastectomies with axillary node dissection, surgical treatment of spontaneous pneumothorax, post-general anesthesia for various clinical reasons, and electrical shock, amongst others). </P> <P> Non-traumatic induced injury to the long thoracic nerve includes, but is not limited to, causes such as viral illness (e.g. influenza, tonsillitis - bronchitis, polio), allergic - drug reactions, drug overdose, toxic exposure (e.g. herbicides, tetanus), C7 radiculopathy, and coarctation of the aorta . </P>

Paralysis of the serratus anterior would result in the inability to
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