The posterior triangle is located in the lateral cervical region of the neck. This blog will describe the posterior triangle of the neck which includes: the apex, base, borders, roof, and floor.
The apex is formed by the meeting of the anterior and posterior borders. This is the union of the sternocleidomastoid and the trapezius muscles at the superior nuchal line of the occipital bone. The borders of the posterior triangle include:
- The base—the middle one third of the clavicle
- Anterior Border—the posterior border of the sternocleidomastoideus
- Posterior Border—anterior border of the trapezius
The roof of the triangle is covered by skin, as well as superficial fascia that contains the platysma, the external jugular vein, the cutaneous branches of the cervical plexus and deep fascia.
The floor of the triangle is formed by the Splenius, levator scapula, scalenus medius, and the anterior scalene muscles. The inferior belly of the omohyoid muscle crosses the triangle about 2.5 cm above the clavicle. The omohyoid muscle divides the space into two triangles: the occipital triangle and the subclavian or supraclavicular triangle.
The posterior triangle of the neck is comprised of several nerves including the spinal accessory nerve, the branches of the cervical plexus, the phrenic nerve, and the roots and trunks of the brachial plexus. The brachial plexus lies between the scalenus anterior and medius muscles. The arteries include the occipital, transverse cervical, subclavian, and suprascapular arteries.
There are two veins within the Posterior Triangle of the neck: the terminal part of the external jugular and the subclavian veins. Additionally, the deep cervical lymph nodes are located here. It is important for surgeons to remember that the spinal accessory nerve is vulnerable to damage during a lymph node biopsy. After a lymph node biopsy, the patient may have shoulder pain, dysfunction, and lateral winging of the scapula which can occur due to a spinal accessory nerve injury. An accessory nerve injury typically occurs due to a blunt or penetrating trauma, or during a surgical dissection of the posterior triangle of the neck such as in a lymph node biopsy.
Treatment
Spinal Accessory Nerve injuries are typically treated with physical therapy. A surgical repair of the nerve may be considered up to one year. A muscle transfer may be necessary for chronic cases such as a levator scapulae and rhomboids transfer.
