The Trapezius Muscle

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

 

TRAPEZIUS

Anatomy
– It 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 arise from external occipital protuberance and medial third of superior nuchal line.
– Middle fibers from ligamentum nuchae and spinous process of C7.
– Lower fibers from spinous processes and supra spinous ligaments of all twelve thoracic vertebrae.
– It is inserted into the lateral third of clavicle, acromion process and spine of scapula.

Function
– It allows for rotation and lift of scapula.

Innervation
– 3rd and 4th cervical nerve.
– Spinal accessory nerve – motor innervation to trapezius.

Course: obliquely across posterior triangle ( where is it vulnerable since it is superficial and covered only by skin and subcutaneous fascia), surface of levator scapula muscle and reach trapezius.

Clinical correlation
– Its dysfunction results in lateral winging of scapula.
– Spinal accessory nerve is injured, resulting in difficulty in overhead activity. ( therefore extreme caution should be taken for any surgical procedure in posterior triangle)
– Occurs

• after radical neck surgery
• after biopsy or tumor dissection.

Treatment
– If injury is early – explore nerve.
– If injury is late – muscle transfer