Review of the Literature on Anatomical Variations of the Trapezius Muscle

The trapezius muscle originates on the occipital bone, nuchal ligament, spinous process of the 7th cervical vertebra (C7) and all of the thoracic vertebrae (Figure 1). It has three parts. The superior portion (descending fibers) terminates on the posterior margin and superior side of the lateral third of the clavicle. The transverse portion (middle fibers) terminates on the medial margin of the acromion and superior lip of the posterior border of the scapular spine. The inferior portion (ascending fibers) ends as an aponeurosis on the posterior edge of the scapular spine and a tubercle. The trapezius muscle is innervated by the accessory nerve and the cervical plexus. It helps to move the head (extension and rotation) and the shoulders (shrugging, lowering, posterior tipping, bringing the scapulae closer together).