Definition
The term Scapula alata comes from Latin. Scapula means shoulder blade and ala wing. It is the protrusion of one or both shoulder blades from the back of the thorax. The shoulder blade protrudes like a wing, which gives this appearance its name. A scapula alata can be the result of various diseases that can affect muscles, nerves and the skeletal system.
Causes
A scapula alata can have a variety of causes. The wing position of the shoulder blades can be particularly noticeable in people who are very slim and at the same time very tall. In this case one speaks of a leptosome habitus.
A physique that is very sinewy and thin. At the same time, there is often little padding of subcutaneous fatty tissue, so that bone malpositions appear much more pronounced. In addition, the scapula alata can also be the result of various nerve damage.
The serratus muscle, also called the saw muscle (M. serratus anterior), is one of the most important muscles that hold the shoulder blade in position. The muscle pulls from the ribs to the middle edge of the shoulder blade, thereby pulling it forward towards the rib cage. This muscle is innervated by the long thoracic nerve.
If the muscle is injured, paralysis can occur, which eventually causes the corresponding shoulder blade to protrude. Typical injuries to this nerve are trauma from blows, accidents, overstraining in bodybuilding or over-stimulation from wearing a backpack for a long time, since the carrying strap runs underneath the arm. The paralysis can also be idiopathic, which means that there is no known clear cause.
Other nerves such as the thoracodorsalis nerve also innervate the shoulder blade. If the shoulder blade is damaged, the lower tip of the shoulder blade protrudes. Furthermore, a disease of the muscles themselves can also lead to the appearance of wing shoulder blades.
Especially the progressive muscular dystrophy in the shoulder girdle area can lead to a scapula alata. As a result of the increasing atrophy of the muscles, the shoulder blade is no longer attached to the body and turns away from the outside, so that it protrudes from the chest. A scapula alata can occur in the context of various neurological clinical pictures.
Frequent nerve damage that causes the shoulder blade to protrude is damage to the thoracic nerve longus and the dorsal nerve scapulae. If the thoracic long nerve fails, the anterior serratus muscle is paralyzed, resulting in the formation of a scapula alata, especially when the shoulder is raised. Damage to the scapula dorsalis nerve leads to the loss of the major and minor rhomboid muscles on the same side and occasionally to the scapula levator muscle. As a consequence of the nerve damage, the image of a scapula alata also occurs here. At the same time, damage to the accessorius nerve can paralyze the trapezius muscle, musculus trapezius, and trigger a scapula alata when the shoulder is abducted.