Definition

By: Gregory R. Waryasz, MD

The trapezius of the musculoskeletal system is characterized by being a direct attachment for the pectoral girdle to the trunk. The name trapezius is derived from how the muscles of the two sides from a trapezium.

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

Its unique structural features include being a large and traigular muscle. It is located covering the posterior neck and superior half of the trunk. There are three distinct fiber types giving different functions; superior, middle, and inferior fibers.

The origin is at the medial 3rd of the superior nuchal line, external occipital protuberance, nuchal ligament, and spinous processes of C7-C12 vertebrae.

The insertion is the lateral third of the clavicle, the acromion, and the scapular spine.

The blood supply is from transverse cervical artery and circumflex scapular artery and venous drainage is from the accompanying veins.

The innervation is from cranial nerve XI.

The trapezius 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 trapezius is to rotate the glenoid superiorly.  The descending/superior part of the trapezius is to elevate the scapula. The ascending/inferior part of the trapezius depresses the scapula. The middle part of the trapezius retracts the scapula.  The trapezius braces the shoulders by fixing the scapulae to the thoracic wall.  Weak trapezius muscles cause drooping of the shoulders.

Common diseases include trapezius paralysis and trapezius strain.

The winged scapula from trapezius paralysis is laterally whereas the winging is medial in serratus anterior paralysis.   Trapezius paralysis is often the result of surgical injury, trauma, or mishandled biopsy of a cervical lymph node.

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

It is usually treated with physical therapy and NSAIDs for trapezius strain.  Physical therapy and observation which usually result in improvement in of a winged scapula, but patients may not improve.

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: Trapezius (http://www.wheelessonline.com/ortho/trapezius)