Smith Robinson Approach

 

Anterior cervical spine

 

Indication

 

Anterior approach to subaxial spine

C3 - T1

 

Conditions

 

Trauma

Radiculopathy

Myelopathy

Infection

Tumour

 

Position

 

Head

- Supine in tongs

- taped on head board with head taped

- neck slightly extended

 

Shoulders can be taped down for access to lower cervical spine

 

Reverse Trendelenberg 30°

- reduce venous bleeding

 

Turn head away from side of incision

 

Landmarks

 

Fluoroscopy for levels

 

Landmarks

- Hyoid cartilage C3/4

- Thyroid cartilage C4/5

- Cricoid cartilage C6

- Carotid tuberble C6

 

3 Fascial layers

 

1.  Deep cervical fascia

- under the subcutaneous fat

- invests neck like collar

- clavicle / sternum / spine scapula - mandible / base of skull

- invests sternocleidomastoid (SCM) & trapezius

- have to incise so can retract SCM

- platysma and external jugular vein superficial to deep cervical fascia

 

2.  Pretracheal fascia

- anterior neck only

- covers thyroid / tracheal / oesophagus

- deep to the strap muscles

- extends from hyoid into chest

- fuses laterally with carotid sheath

- have to divide to retract carotid sheath laterally

 

3.  Prevertebral fascia

- base of skull to T3

- invests longus colli and sympathetics

- covers ALL

- divide to separate longus colli muscles to approach vertebral bodies and discs

 

Technique

 

AO Surgery Reference Anterior Approach Subaxial Spine

 

Anterior approach subaxial spine

 

Transverse incision

- midline to medial border of SCM

 

Divide platysma

 

Incise deep cervical fascia

- just anterior to anterior border of SCM

- retract SCM laterally

- retract strap muscles (sternohyoid / sternothyroid) medially with trachea and oesophagus

 

Palpate and identify carotid sheath and divide pretracheal fascia medially

- retract carotid sheath laterally with SCM

- occasionally have to ligate superior thyroid artery

 

Expose Longus colli muscles anteriorly over ALL

- sympathetic chain lies on the Longus colli, just lateral to the vertebrae

- dissect between muscles in the midline

- retractors under longus colli

- expose cervical vertebrae

 

Confirm level with fluoroscopy

 

Which Side?

 

Most surgeons approach from the left

- the course of the Recurrent laryngeal nerve (RLN) is more predictable on left

 

Right sided approach

- used sometimes for C7/T1 to avoid thoracic duct

 

Structures at Risk

 

Vertebral artery

Esophagus

Superficial laryngeal nerve

Recurrent laryngeal nerve

Cervical sympathetic trunk

 

Vertebral artery

 

Anatomy

 

Origin from subclavian arteries

- anterior to C7 transverse process

- enter at C6 and travel in transverse foramina

 

Vertebral artery anatomyVertebral artery 2Vertebral artery 3

 

Vertebral artery 3Vertebral artery 4

 

Consequence of injury

 

Stroke / neurological deficit

Hemorrhage

Pseudoaneurysm and late hemorrhage

 

Incidence

 

Obermuller et al Acta Neruochirurgica 2015

- 992 cases

- 0.3% incidence vertebral artery injury

- all three cases stented and repaired

- no neurological deficit

 

Protection

 

Stay medial to uncovertebral joints

 

Management

 

Control hemorrhage

Vascular surgery

Repair +/- stent

 

Esophagus

 

Dysphagia

 

Symptoms range from difficulty swallowing to aspiration

 

Tsalimas et al Cureus 2022

- systematic review of 73 ACDF studies

- overall dysphagia rate 19%

- associated with prolonged surgery / multilevel surgery / revision surgery / female sex

- reduced with use of zero profile plates

 

Lee et al Spine 2007

- 310 ACDF patients followed for 2 years

- incidence at 1 month 54%

- incidence at 1 year 15%

- incidence at 2 years 14%

 

Perforation

 

Zhong et al J Clin Neurosci 2013

- incidence 5/1097 (0.5%)

 

Halani et al J Neurosurg Spine 2016

- systematic review of 165 patients sustaining esophageal perforation

- most in trauma setting

- caused by hardware failure or erosion most commonly, direct injury less common

- presented with dysphagia / fever / neck swelling / wound leakage

- diagnosed with contrast studies / CT / MRI

- treated by primary repair or modified muscle flap

- mortality 6/153 (3%) - pneumonitis / mediastinitis / sepsis

 

Recurrent Laryngeal Nerve

 

Consequence of injury

 

Ipsilateral paralysis of the vocal cord

Hoarseness

 

Anatomy

 

Left side

- arises at the level of the aortic arch

- ascends between trachea and esophagus

- doesn't slope across the wound

 

Right side

- given off the vagus at the level of the subclavian artery

- slopes from lateral to medial across lower part of wound to reach the oesophagus / trachea interval

- crosses the surgical approach in 50% of cases

- usually at C6/7 with inferior thyroid artery

- may be at C5/6

 

Incidence

 

Kilburg et al J Neurosurg Spine 2006

- 8/278 (1.9%) had RLN injury with right sided approach

- 3/140 (2.1%) had RLN injury with left sided approach

 

Risk factors

 

Erwood et al J Neurosurg Spine 2016

- meta-analysis of incidence of RLN injury after revision surgery

- 14%

 

Jung et al Neurosurgery 2010

- reduced injury to RLN with reduced endotracheal cuff pressure

 

Superior Laryngeal Nerve

 

Consequence of injury

 

Dysphagia

Hoarseness

 

Anatomy

 

Superior laryngeal nerve runs with superior thyroid artery at C3/4

 

Cervical sympathetic trunk

 

Anatomy

 

Runs on the longus colli muscles

 

Consequence of injury

 

Horner syndrome

- ipsilateral ptosis

- ipsilateral meiosis

- anhidrosis

 

Incidence

 

Lubelski et al World Neurosurg 2020

- systematic review of 21 studies

- incidence of 0.6%

- 60% completely resolved at 1 year