Anterior Retropharyngeal Approach to the Upper Cervical Spine (C1–C3)

The anterior retropharyngeal approach (Robinson–Southwick or McAfee modification) provides extraoral access to the craniovertebral junction and upper cervical spine (C1–C3) without entering the oral cavity. Performed in the supine position with the head rotated away from the operative side and slightly extended, the approach uses either a transverse submandibular incision or an oblique incision along the anterior border of the sternocleidomastoid. The key internervous plane is developed medial to the carotid sheath and lateral to the visceral column (pharynx, larynx, trachea, oesophagus). The marginal mandibular branch of the facial nerve is the most superficial critical structure and is protected by early identification, ligation of the retromandibular vein and facial vessels, and cephalad retraction with the submandibular gland. Deeper dangers include the hypoglossal nerve, superior laryngeal nerve, and contents of the carotid sheath. The approach reaches the anterior arch of C1, the odontoid process, and the bodies of C2 and C3. It is indicated for odontoid nonunion, basilar invagination, upper cervical tumours or infection, and corpectomy when a clean extraoral field is preferred. The exposure extends caudally into a standard Smith–Robinson approach for multilevel pathology.

Primary Indications:

• Odontoid fracture nonunion or malunion requiring direct anterior access
• Basilar invagination or cranial settling with anterior compression
• Upper cervical (C1–C3) tumours (chordoma, metastasis, plasmacytoma)
• Pyogenic or tuberculous osteomyelitis/discitis of C1–C3 requiring debridement and grafting
• Anterior C1–C2 or C2–C3 corpectomy and reconstruction when transoral route is contraindicated
• Revision anterior surgery after failed transoral or posterior procedures

Why This Approach is Chosen:

The anterior retropharyngeal route provides wide extraoral exposure of the craniovertebral junction and upper cervical spine while avoiding oral bacterial contamination. It allows placement of odontoid screws, anterior C1–C2 plating, or strut grafting under clean conditions. When pathology extends below C3, the exposure continues seamlessly into a standard Smith–Robinson anterior cervical approach.

Contraindications:

• Active infection in the submandibular or anterior neck skin
• Severe trismus or limited mouth opening (relative — may still be feasible)
• Unstable cervical spine without prior posterior stabilisation (relative)
• Previous radical neck dissection on the ipsilateral side (vascular anatomy altered)
• Patient factors precluding supine positioning with head extension

Alternative Approaches:

• Transoral approach: Direct midline access to C1–C2 but carries higher infection risk and limited lateral exposure
• Posterior approaches (occiput–C2 fusion): For posterior stabilisation or when anterior access is not required
• Lateral retropharyngeal (Fisch): More lateral exposure but greater morbidity
• Endoscopic endonasal: Selected centres for purely midline upper clival pathology

Bony Anatomy:

The craniovertebral junction comprises the occiput, atlas (C1), and axis (C2). The anterior arch of C1 lies immediately posterior to the pharynx. The odontoid process projects superiorly from C2 and articulates with the anterior arch of C1 and the transverse atlantal ligament. C3 marks the transition to the typical cervical vertebral morphology. The longus colli muscles form the anterior paravertebral gutter and serve as the key midline landmark during deep dissection.

Muscular and Fascial Layers:

Neurovascular Anatomy (Layer by Layer):

Key Intervals:

The safe surgical corridor lies between the carotid sheath (lateral) and the visceral column (medial). The retropharyngeal space is entered by dividing the prevertebral fascia. The longus colli muscles are detached from their origins on the anterior tubercles and reflected laterally to expose the anterior arch of C1 and the bodies of C2 and C3.

Deep Internervous Plane:

• Between: Carotid sheath contents (vagus nerve, CN X) laterally and visceral column (pharynx, larynx, trachea, oesophagus) medially
• Clinical relevance: This plane is truly internervous because the vagus supplies the laryngeal muscles while the pharyngeal plexus (CN IX and X) supplies the pharyngeal constrictors. No muscle is divided; the interval is developed by blunt and sharp dissection.

Superficial Dissection:

There is no classical internervous plane superficially. The platysma is divided in line with the skin incision. The marginal mandibular branch of the facial nerve (CN VII) is identified and protected by ligating the retromandibular vein and facial vessels and retracting the nerve cephalad with the submandibular gland.

Structures at Risk in Each Layer:

Position: Supine on Radiolucent Table with Head Extension

Pre-positioning Checklist:

• Confirm cervical spine stability (may require prior posterior stabilisation)
• Gardner-Wells tongs or Mayfield head holder for controlled extension and rotation
• Arms tucked at sides with slight shoulder traction for fluoroscopic access
• Radiolucent table confirmed
• C-arm positioned for true lateral and AP (open-mouth) views of C1–C2
• Endotracheal tube secured on the contralateral side

Positioning Details:

• Supine position with slight head extension (10–15 degrees) and rotation 30–40 degrees away from the operative side
• Shoulder roll or slight reverse Trendelenburg to improve venous drainage
• Tongue gently retracted if necessary (rarely required)
• Tourniquet not applicable
• Neuromonitoring (MEP/SSEP) recommended for upper cervical procedures

Alternative Positioning:

• Slight lateral decubitus with head turned can be used if combined posterior access is planned, but pure supine is standard
• Mayfield three-pin fixation provides rigid control for odontoid screw placement

Key Bony Landmarks:

• Inferior border of mandible — transverse incision placed 2–3 cm below
• Hyoid bone — palpable at C3 level; marks the position of the hypoglossal nerve
• Thyroid cartilage — C4–C5 level; useful for orientation
• Sternocleidomastoid anterior border — guides oblique incision for caudal extension
• Cricoid cartilage — C6 level; marks the transition to standard anterior cervical approach

Key Soft Tissue Landmarks:

• Submandibular gland — palpable below mandible; mobilised during dissection
• Carotid pulse — palpable lateral to visceral column
• Anterior border of sternocleidomastoid — guides incision for extended exposure

Incision Planning:

• Transverse submandibular incision: 6–8 cm horizontal incision 2 cm below the inferior mandibular border, centred on the midline or slightly to the operative side
• Oblique SCM incision: Begins at the angle of the mandible and extends obliquely along the anterior border of the sternocleidomastoid toward the sternal notch for multilevel exposure
• Length and exact placement depend on the cephalad–caudal extent of pathology

Nerve Injury Management:

• Marginal mandibular or hypoglossal neuropraxia: observe; most recover within 3–6 months
• Superior laryngeal nerve injury: voice therapy; aspiration precautions
• Permanent deficit: consider medialisation thyroplasty or tongue suspension procedures after 12 months

Caudal Extension (Smith–Robinson Continuity):

The incision is lengthened distally along the anterior border of the sternocleidomastoid. The same internervous plane is developed to C7. Standard anterior cervical discectomy, corpectomy, or disc arthroplasty can be performed without repositioning. This is the most common extensile manoeuvre.

Proximal Extension:

Limited proximal extension toward the mastoid tip is possible by mobilising the facial nerve further cephalad and dividing the posterior belly of the digastric. True access to the clivus requires a separate transoral or endoscopic endonasal route.

Bilateral Exposure:

For midline tumours or extensive infection, bilateral retropharyngeal approaches can be performed simultaneously by two teams. This provides wider lateral exposure but increases nerve injury risk.

Combined Anterior–Posterior (360-Degree) Reconstruction:

When circumferential decompression and stabilisation are required, the anterior retropharyngeal approach is performed first, followed by posterior occiput–C2 or C1–C3 instrumentation in the same or staged procedure.

Revision Surgery Considerations:

Previous anterior cervical surgery or radiation alters tissue planes. The carotid sheath may be adherent to the visceral column. Intra-operative ultrasound or navigation assists in identifying the correct plane.

Intra-operative Complications:

Post-operative Complications:

Immediate Post-operative:

• Neurovascular checks including lower cranial nerves every 2 hours for first 24 hours
• Airway assessment and readiness for re-intubation
• Drain output monitoring (retropharyngeal drain)
• Head elevation 30 degrees to reduce oedema
• NPO until swallow assessment

Swallowing and Nutrition:

• Formal speech-language pathology swallow evaluation before oral intake
• If dysphagia present: thickened liquids, swallowing exercises, temporary nasogastric feeding
• Gastrostomy considered for prolonged dysphagia (greater than 7–10 days)

Mobilisation and Bracing:

• Soft cervical collar for comfort (2–6 weeks depending on procedure)
• Early mobilisation with assistance
• No heavy lifting or neck straining for 6–12 weeks

Follow-up Schedule:

• 2 weeks: wound check, suture removal, swallow review
• 6 weeks: radiographs (AP, lateral, open-mouth), assess fusion
• 3 months: CT to confirm fusion and implant position
• 6–12 months: final clinical and radiographic review

DVT Prophylaxis:

• Mechanical (IPC) while inpatient
• LMWH or aspirin per institutional protocol until mobile

Upper cervical spine pathology is managed at tertiary spine centres worldwide. The anterior retropharyngeal approach is recognised across examination systems (FRCS, FRACS, EBOT, ABOS) as the standard extraoral route to the craniovertebral junction when a clean field is required.

Side-by-side principles (where guidance converges):

Registry / population evidence:

• Odontoid fractures represent approximately 15% of all cervical spine fractures; nonunion rates after non-operative treatment range from 10–50% depending on fracture type and patient factors.
• Anterior odontoid screw fixation achieves fusion in 85–95% of appropriately selected cases when performed through an anterior retropharyngeal exposure.
• Infection rates after anterior retropharyngeal surgery are consistently lower (1–4%) than after transoral surgery (10–20%).

Global practice variation:

In high-resource centres, intraoperative navigation, robotic assistance, and custom patient-specific implants are increasingly used for odontoid screw and C1–C2 instrumentation. In resource-limited settings, the same anatomic principles apply using standard anterior cervical plates, tricortical iliac crest autograft, and careful hand-held retraction.

Consent (globally applicable):

Discuss marginal mandibular nerve injury (transient 10–15%, permanent less than 3%), hypoglossal nerve injury (transient 5–10%), superior laryngeal nerve injury with voice change and aspiration (5–15%), dysphagia (20–40% transient), airway compromise requiring re-intubation or tracheostomy (5–15%), infection (2–5%), nonunion (5–15%), and the possibility of future revision surgery or combined posterior stabilisation.