Anterior Approach to Cervical Spine - Approaches

Indications

Overview
- widely used approach that exposes anterior vertebral bodies from C2 to T1
Indications
- cervical radiculopathy
  - anterior cerical disctomy & fusion (ACDF)
- myelopathy
  - anterior corpectomy and fusion
- tumor
  - anterior corpectomy and fusion
- odontoid fracture
  - C2 anterior screw osteosynthesis
- infection & epidural abscess
  - anterior cervical discectomy & fusion (ACDF)

Applied surgical anatomy

It is important to understand the three fascial layers of the neck
- superficial fascia
  - formed by the investing layer of deep cervical fascia
  - platysma and external jugular vein are only structures superficial to it
  - surround neck like a collar, but splits around the SCM and trapezius
- pretracheal fascia
  - continous with carotid sheath at sheath's lateral margin
  - superior and inferior thyroid vessels run from the carotid sheath through the pretracheal fascia to the midline
- prevertebral fascia
  - thick and tough fascia that lines in front of the prevertebral muscles
  - the cervical sympathetic trunk (runs over transverse processes) runs on its surface
Landmarks
- angle of mandible correlates with the C2-3 disc space
- carotid tubercle is the anterior tubercle of the transverse process of C6

Planes

Superificial
- divide platysma which is innervated high up in the neck by the facial (seventh) cranial nerve
Middle
- sternocleidomastoid (spinal accessory nerve)
- strap muscles (segmental innervation from C1, C2, C3)
Deep
- left longus colli muscles (segmental branches of cervical nerves)
- right longus colli muscles

Preparation

Anesthesia
- general as airway needs to be protected
Position
- supine
Imaging
- cross table lateral required to identify correct level
  - shoulders/arms often pulled caudal to obtain better visualization of C7

Approach

Incision
- make transverse skin crease incision at appropriate level
- extend obliquely from the midline to the posterior border of the SCN
- side
  - surgeons preference
Superficial Dissection
- incise fascia over platysma
- spit platysma with finger
- identify anterior border of SCM
- incise fascia and retract SCM lateral
- identify and retract strap muscles medially (sternohyoid and sternothyroid)
- identify the carotid pulse and retract carotid sheath lateral
- cut through pretrachial fascia
- localize superior and inferior thyroid arteries and tie off if necessary
Deep dissection
- split longus colli muscles and anterior longitudinal ligament
  - be aware of sympathetic chain that lies on longus colli lateral to vertebral body
- subperiostally disect to expose anterior surface of vertebral body
  - retract longus colli muscles and ALL laterally
- identify level with needle in disc space and lateral xray

Structures at Risk

Recurrent laryngeal nerve
- injury rate 2.3% (same injury rate for left RLN and right RLN)
- left RLN
  - ascends in neck in tracheoesophageal groove after branching off from parent nerve the vagus at the level of the arch of the aorta
- right RLN
  - runs alongside the trachea in the neck after hooking around the right subclavian artery
  - crosses from lateral to medial to reach midline
  - more vulnerable than left during exposure because
    - it has a more variable course
    - lies more anterolateral
- protect by placing retractors under medial edge of longus colli muscle
Sympathetic nerves and stellate ganglion
- damage or irritation causes Horner's syndrome
  - characterized by ptosis, anhydrosis, miosis, enophthalmos and loss of ciliospinal reflex on the affected side of the face
  - caused by injury to sympathetic chain, which sits on the lateral border of the longus colli muscle at C6
- protect by subperiosteal dissection of longus colli muscles from midline
Carotid sheath and contents
- protected by the anterior border of SCM
- be careful with lateral retractor placement
Postoperative retropharyngeal hematoma
- presents with respiratory difficulties
- tense hematomas should be emergently decompressed if causing respiratory compromise
  - physical exam will show a tense mass under the incision
- most common cause is postsurgical edema