Cervical spine exposure

The anatomy of neck can be for purpose of convenience is divided into various triangles. The sternocleidomastoid muscle divides the neck into two triangles. These are further subdivided into smaller triangles by the traversing diagastric and omohyoid muscles into the diagastric, subclavian and the carotid triangle. The skin over the neck is mobile and soft and along with sub cutaneous tissue and platysma offer wide retraction. Platysma muscle lies beneath the skin extending from the mandible to the superficial fascia over the chest. Below the Platysma there is superficial cervical fascia, which contains the superficial nerves of the neck. In the same plane also lies the external jugular vein formed by posterior auricular vein joining a branch of posterior facial vein. The fascial layers of the neck are the important landmarks in the course to the vertebral bodies in the front of neck providing a natural cleavage plane. The deep cervical fascia can be divided into four layers: the superficial layer of the deep cervical fascia surrounds the neck enclosing the trapezius and sternomastoid. The middle layers enclose the strap muscles and the omohyoid. The deep component of the middle layer encloses the larynx, trachea esophagus and thyroid. The carotid sheath is also a condensation of the deep cervical fascia. The deepest layer is the prevertebral fascia, which surrounds the vertebra and para spinal muscles. It also contains the phrenic nerve and the scalene muscles. The carotid sheath contains the common carotid artery the internal jugular vein and the vagus nerve. The sympathetic trunk lies directly over the longus capitii and colli, posterior to the carotid sheath. The vertebral artery, which is the first branch of the subclavian artery, enters the costotransverse foramen of the sixth cervical vertebra ascending through the successive vertebral foraminas.

The patient is positioned supine with a pad of rolled towel placed in between the scapulae. A gardener well’s tongs may be placed if extension or distraction is contemplated. The head should be turned to the opposite side and the shoulders can be pulled down and strapped with adhesive tapes. This helps in taking intraoperative radiographs particularly if lower cervical vertebrae needs to be visualized.

Exposure:

Incision: For exposing a single level or two levels a transverse incision corresponding to the level described above can be taken, however for broad exposure, an longitudinal incision starting at the angle of mandible and extending down to the manubrium sternii anterior to sternocleidomastoid muscle needs to be taken.

The skin, subcutaneous tissue and platysma are divided in the same direction till the superficial fascia is reached. The traversing cervical veins and superficial nerves can be identified through the superficial fascia. After dividing the superficial fascia longitudinally these veins can be ligated and transected. Avoid transecting the mandibular branch of Facial nerve in the most cephalad aspect of incision.

A plane is then developed between the medial border of sternocleidomastoid and the strap muscles.

The Superior belly of Omohyoid muscle runs transversely between the strap muscles and the sternocleidomastoid. The muscle can be divided between two ligatures. Palpate for the carotid pulse below the sternocleido mastoid and gently retract it laterally. The middle cervical fascia should be dissected bluntly and divided medial to carotid pulse in the mid portion of neck. The transverse branches of deep ansa cervicalis may need to be transected.

The strap muscles, trachea, larynx and thyroid are retracted medially while the neuro vascular bundle (the common carotid artery, internal jugular vein and vagus nerve) is retracted laterally.

Middle thyroid vein needs to be tied in exposure of mid portion of neck.

For most of the dissection in middle neck this is the only vessel that needs to be tied.

The deep prevertebral Fascia is then divided in the midline and dissected laterally till the long muscles of neck.

Using a periosteal elevator the longus colli can then be elevated on both sides of anterior longitudinal ligament until the base of transverse processes on both the side. The disc is elevated and softer than the surrounding vertebral body making its identification easier. The level can be confirmed by taking an intraoperative radiograph.

For extending the exposure superiorly superior thyroid artery and veins need to be tied and transected, and for extending the exposure inferiorly the inferior thyroid artery and vein needs to be tied.

If the dissection needs to be extended upwards a blunt dissection is best carried out with fingers. It is vital to identify five vital structures 1) the superior laryngeal nerve. 2) The Hypoglossal nerve. 3) The Facial artery. 4) The lingual artery. 5) The Digastric muscle. The superior laryngeal nerve should be carefully dissected; its caudad external branch is especially vulnerable owing to its close proximity to the superior thyroid artery.

For extending the exposure inferiorly the inferior thyroid artery, which is a branch of thyro cervical trunk or sub clavian, artery should be ligated and divided. The sympathetic trunk and stellate ganglion lies at the same level and should not be injured. The cervical pleura corresponds to the first thoracic vertebrae, and recurrent laryngeal nerve which is a branch of vagus nerve loops around the aorta on the left side and then ascends into the tracheoesophageal groove. The prominent tubercle on C6 vertebrae may serve as guide to level identification but occasionally even the C7 vertebrae may have a prominent tubercle and thus it may be safe to take an intra operative radiograph.

Potential Complications:

Airway obstruction secondary to retropharyngeal edema or hematoma.

Hypoesthesia around the ear.

Esophageal perforation

Recurrent laryngeal palsy

Horner’s Syndrome.

Vertebral Artery Injury

Superior Thyroid Artery injury.

Inferior Thyroid Artery Injury.

Thoracic duct injury.

Laryngeal edema and Hoarseness