Anatomy of Serratus Anterior Muscle

Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

 

The serratus anterior is a fan-shaped muscle that originates on the superolateral surfaces of the first to eighth ribs and inserts along the anterior aspect of medial border of the scapula.

It is the strong protractor of scapula .

It is known as BOXERS MUSCLE or BIG SWING MUSCLE .
It is innervated by long thoracic nerve which arise from the C4 C5 C6 nerve roots.

Injury to this nerve by any kind of trauma, pressure , neuritis or surgery can lead to medial winging of scapula ,difficulty in elevating the arm ,pain ,weakness, spasm and cosmetic deformity. clinically we test this muscle using wall test, in which patient is asked to stand 2 feet in front of a wall, facing the wall and asked to push against the wall with a flat palms at the waist level ,and then we can appreciate winging. alternate test used for evaluation is Resistance of forward flexion test, in this test patient resist the examiners attempt to bring the forward flexed arm downwards.

There is another condition called lateral winging of scapula which is caused by weakness of trapezius muscle due to injury to spinal accessory nerve .

Medial winging of scapula can be treated conservatively by observation for a minimum 18 months ,serratus anterior muscle strengthening exercises . Operative method that we use is pectoralis major muscle transfer