The trapezius is a large superficial muscle that extends
from the back of the skull, back of the neck, and back of the thorax. The upper
fibers of the trapezius muscle arise from the external occipital protuberance
and the medial third of the superior nuchal line. The middle fibers arise from
the ligamentum nuchae and the spinous process of C7. The lower fibers arise
from the spinous processes and supraspinous ligaments of all twelve thoracic
vertebrae. The trapezius is inserted into the lateral third of the clavicle,
and from the acromion process and the spine of the scapula. The trapezius
muscle allows for rotation and lift of the scapula. Dysfunction of the
trapezius muscle may cause lateral winging of the scapula. Winging can occur
after radical neck surgery, but it usually occurs after biopsy or tumor
dissection. The spinal accessory nerve will be injured, and the patient will
have difficulty with overhead activity. If injury to the spinal accessory nerve
occurs early, explore the nerve. If injury is late, do a muscle transfer. The
spinal accessory nerve provides motor innervation to the sternocleidomastoid
and the trapezius muscle. The spinal accessory nerve courses obliquely across
the posterior triangle on the surface of the levator scapula muscle and reaches
the trapezius. Within the posterior triangle of the neck, the nerve is
vulnerable since it is superficial and only covered by skin and subcutaneous
fascia. Extreme caution should be taken for any surgical procedure done in the
posterior triangle of the neck.
