Serratus Anterior Muscles

1.) What muscle did the winging of the scapula suggest to be paralysed? Why does this sign occur?

The muscle that was suggested to be paralysed due to the winging of the scapula is the Serratus Anterior muscle. The Serratus Anterior muscle’s origin is situated on the external surface of the lateral surfaces of the upper 8 to 9 ribs (ribs 1 to 8) while the insertion of this muscle is located on the costal surface of the medial border of the scapula. Therefore, this muscle is innervated by the long thoracic nerve which is a branch of the brachial plexus (ventral rami of C5,6,7) by virtue of the nerves anterior relation to the muscle. The long thoracic nerve runs over Serratus Anterior during its course on the medial wall of the axilla on the mid axillary line, after exiting through scalene muscle and passing over the first rib and posterior to the clavicle.

The clinical indication of injury to the Serratus Anterior muscle is the winging of the scapula. Serratus Anterior is mainly used for anteversion of the arm and is referred to as the “boxer’s muscle” or the “big swing muscle” as it produces quick jab movements by pulling the scapula forward and around the rib cage when there is a punch directed movement. It is also responsible for protraction and
This movement involves the scapula moving both laterally and anteriorly against the chest wall. The same movement occurs when throwing a punch because the arms move forward and so does the scapula along the rib cage and since Mr. Whitwell has damaged his long thoracic nerve, he will have weak protraction of the scapula and due to rhomboid major and minor muscles, there will be a large amount of medialised scapula retraction accompanied by the elevation by actions of the