Definition

By: Gregory R. Waryasz, MD

The serratus anterior of the musculoskeletal system is characterized by being one of the most powerful pectoral girdle muscles.

It is part of the anterior axioappendicular muscles.  It consists of skeletal muscle fibers.

Its unique structural features include being a broad and thick muscle that has a sawtoothed appearance due to the “fleshy slips” and digitations.  It overlies the lateral thorax and forms the medial axillary wall. The serratus anterior attaches to the entire anteromedial scapula including the inferior angle.

The origin is at the external surfaces of the lateral parts of the 1st through 8th ribs.

The insertion is the anterior surface of the medial scapula.

The blood supply is from lateral thoracic artery and circumflex scapular artery and venous drainage is from the accompanying veins.

The innervation is from the long thoracic nerve.

The serratus anterior muscle as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in the embryo.

The function of the serrratus anterior is to protract the scapula and hold it against the thoracic wall. It also helps to rotate the scapula.  The serratus anterior is also known as the “boxer’s muscle” as it is used when punching or reaching anteriorly.  During push-ups, the serratus anterior helps to hold the scapula against the thoracic wall.

Common diseases include winged scapula or serratus paralysis.

The winged scapula or serratus paralysis refers to injury to the long thoracic nerve resulting in a scapular motion laterally and posteriorly to the thoracic wall. This is exacerbated when pushing on a wall with an outstretched arm.  The winging is medial in serratus paralysis, whereas in trapezius paralysis, the winging is lateral.

The inferior 3 slips of the serratus anterior can be used for free tissue transfer coverage of hand defects.

Commonly used diagnostic procedures include clinical history, physical exam, and MRI.

It is usually treated with physical therapy and observation which usually results in improvement in 6 months.

References

Lieberman J (ed), AAOS Comprehensive Orthopaedic Review, American Academy of Orthopaedic Surgeons, 2008.

Moore K, Dalley A (eds), Clinically Oriented Anatomy (5th edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.

Wheeless’ Textbook of Orthopaedics: Serratus Anterior (http://www.wheelessonline.com/ortho/serratus_anterior)