ACDF - ANTERIOR CERVICAL DISCECTOMY AND FUSION
Smith-Robinson Approach | Disc Excision | Interbody Fusion | Plate Fixation
INDICATIONS BY PATHOLOGY
Critical Must-Knows
- Smith-Robinson approach is standard anterior cervical exposure
- Longus colli dissection protects vertebral artery and sympathetic chain
- Recurrent laryngeal nerve is at risk on right side (loops around subclavian)
- Dysphagia is commonest complication (transient in most)
- Anterior plate increases fusion rate especially in multilevel
Examiner's Pearls
- "Left-sided approach preferred to avoid RLN (loops around aorta - longer protected course)
- "Esophagus lies behind trachea - retract together medially
- "Vertebral artery lies in transverse foramen from C6 upward
- "Superior laryngeal nerve at risk with retraction above C3
Clinical Imaging
Imaging Gallery
Clinical Imaging
Post-Operative ACDF Radiographs
ACDF Complications: Adjacent Segment Disease and Subsidence
Critical ACDF Exam Points
Approach Side Matters
Left-sided approach preferred as recurrent laryngeal nerve has longer protected course around aortic arch. On the right side, RLN loops around subclavian artery and is more variable and vulnerable. Some surgeons prefer right for better angle to right-sided pathology.
Key Anatomy
The longus colli muscles must be dissected to expose disc space and protect vertebral artery laterally. Carotid sheath (carotid, IJV, vagus) retracted laterally. Esophagus and trachea retracted medially.
Dysphagia Prevention
Dysphagia is the most common complication (50% transient, 2-5% persistent). Minimize with: deflating endotracheal cuff during retraction, limiting retraction pressure, shorter surgical time, and avoiding high retractor blade placement.
Fusion Considerations
Anterior plate increases fusion rates especially in multilevel surgery. Cage height should restore disc height and lordosis but avoid over-distraction. Bone graft options include autograft, allograft, or cage with bone substitute.
ACDF At a Glance
| Parameter | Details | Clinical Relevance |
|---|---|---|
| Common indications | Radiculopathy, myelopathy, disc herniation | Failed conservative treatment or progressive neuro deficit |
| Most common level | C5-6 (60%), C6-7 (30%) | Correlates with degenerative disease pattern |
| Approach side | Left preferred (RLN protection) | Right may be used for right-sided pathology |
| Fusion rate | 95% single level, 85% two level | Plate increases rate in multilevel |
| Adjacent segment disease | 2.5-4% per year | Similar to lumbar spine |
| Common complications | Dysphagia (most common), hoarseness, hematoma | Most transient, rare but serious permanent |
ACDF - Indications
Memory Hook:ACDF is indicated for Arm pain, Cord compression, Disc herniation, and Failed conservative care
SMITH - Approach Layers
Memory Hook:SMITH-Robinson approach layers from superficial to deep
DANGER - Complications
Memory Hook:DANGER zones in ACDF - watch for these complications
LEFT Side Approach
Memory Hook:LEFT side preferred for recurrent laryngeal nerve protection
Overview and Epidemiology
Anterior cervical discectomy and fusion (ACDF) is one of the most commonly performed spinal procedures. First described by Robinson and Smith in 1955, it revolutionized cervical spine surgery by providing anterior access for neural decompression.
Historical development:
- 1955: Smith and Robinson describe anterior approach with iliac crest graft
- 1958: Cloward describes cylindrical dowel graft technique
- 1970s-80s: Introduction of anterior cervical plating
- 1990s-2000s: Development of cage technology
- 2000s-present: Total disc replacement as alternative
Indications:
- Cervical radiculopathy: Failed conservative treatment (6-12 weeks)
- Cervical myelopathy: Any progressive or significant myelopathy
- Disc herniation: Symptomatic soft or hard disc
- Cervical instability: Traumatic or degenerative
- Tumor/infection: Anterior column pathology
Conservative Treatment Duration
For cervical radiculopathy without myelopathy, 6-12 weeks of conservative treatment is recommended before surgery. Myelopathy with progressive symptoms or significant cord compromise should proceed to surgery without delay.
Pathophysiology and Mechanisms
Surgical anatomy of the anterior cervical spine:
Superficial structures (anterior to posterior):
- Skin and platysma muscle
- Superficial cervical fascia
- Sternocleidomastoid muscle (lateral landmark)
Deep structures:
- Carotid sheath (lateral): Contains carotid artery, internal jugular vein, vagus nerve
- Trachea and esophagus (medial): Retracted together
- Pretracheal fascia: Dissected to reach spine
- Longus colli muscles: Cover anterior vertebral bodies
Vertebral Artery
The vertebral artery enters the transverse foramen at C6 (variable, can be C5-C7). During lateral dissection and foraminotomy, stay medial to the uncovertebral joint to avoid vertebral artery injury.
Key neural structures:
-
Recurrent laryngeal nerve (RLN):
- Left: Loops around aortic arch (longer protected course)
- Right: Loops around subclavian artery (shorter, more vulnerable)
- Supplies all intrinsic laryngeal muscles except cricothyroid
- Injury causes hoarseness, aspiration
-
Superior laryngeal nerve (SLN):
- External branch at risk with retraction above C3
- Supplies cricothyroid muscle
- Injury affects voice quality/projection
-
Sympathetic chain:
- Lies lateral on longus colli
- Injury causes Horner syndrome
Disc space anatomy:
- Anterior longitudinal ligament (superficial)
- Annulus fibrosus
- Nucleus pulposus
- Posterior longitudinal ligament
- Uncovertebral joints (Joints of Luschka) - lateral margin
Classification Systems
When to perform ACDF
| Indication | Key Features | Timing |
|---|---|---|
| Radiculopathy | Dermatomal arm pain, motor/sensory deficit | After 6-12 weeks failed conservative |
| Myelopathy | Long tract signs, gait disturbance, hand dysfunction | Urgent - avoid delay |
| Soft disc herniation | Acute or subacute, may be single level | Failed conservative or significant deficit |
| Spondylotic radiculopathy | Hard disc, osteophytes, foraminal stenosis | Failed conservative treatment |
| Traumatic instability | Flexion-distraction, facet dislocation | Urgent |
Myelopathy with progression or significant cord compression should not be delayed for conservative treatment.
Clinical Assessment
History:
- Neck pain (axial)
- Arm pain (radicular - dermatomal distribution)
- Numbness/tingling (dermatomal)
- Weakness (myotomal)
- Hand clumsiness (myelopathy)
- Gait disturbance (myelopathy)
- Bladder/bowel symptoms (severe myelopathy)
- Duration and progression
- Response to conservative treatment
Examination:
Cervical Radiculopathy Examination
| Root | Motor | Sensory | Reflex |
|---|---|---|---|
| C5 | Deltoid, biceps | Lateral arm | Biceps |
| C6 | Wrist extensors, biceps | Lateral forearm, thumb | Brachioradialis |
| C7 | Triceps, wrist flexors | Middle finger | Triceps |
| C8 | Finger flexors, intrinsics | Medial forearm, ring/little finger | None reliable |
| T1 | Intrinsics | Medial arm | None reliable |
Myelopathy signs:
- Upper motor neuron signs (hyperreflexia, clonus, Babinski)
- Lhermitte sign (electric shock with neck flexion)
- Hoffmann sign (thumb/index flexion with middle finger flick)
- Gait disturbance (broad-based, spastic)
- Hand dysfunction (grip and release test)
- Inverted radial reflex
Disc vs Root Relationship
The C5-6 disc compresses the C6 nerve root (exiting above the disc). Similarly, C6-7 disc affects C7 root. The nerve root exits above the pedicle of the same numbered vertebra (unlike lumbar spine where root exits below).
Investigations
Gold standard imaging
Key sequences:
- T1-weighted: Anatomy, bone marrow changes
- T2-weighted: Cord signal (myelomalacia), disc pathology
- Gradient echo (T2*): Metal artifact reduction, better disc visualization
Key findings:
- Disc herniation (soft disc)
- Osteophyte complex (hard disc)
- Cord compression
- Cord signal change (poor prognostic sign)
- Foraminal stenosis
MRI should correlate with clinical findings to confirm surgical level(s).
Management Algorithm
For radiculopathy without myelopathy
Medications:
- NSAIDs
- Oral corticosteroids (short course for acute)
- Neuropathic pain agents (gabapentin, pregabalin)
- Muscle relaxants
Physical therapy:
- Cervical traction (controversial)
- Strengthening exercises
- Postural training
- Activity modification
Injections:
- Cervical epidural steroid injection
- Selective nerve root blocks
- Transforaminal vs interlaminar approach
Expected outcomes:
- 50-70% improve with conservative treatment
- Natural history of radiculopathy is generally favorable
Give adequate conservative trial unless progressive deficit or myelopathy.
Surgical Technique
Smith-Robinson anterior cervical approach
Positioning:
- Supine with neck in neutral or slight extension
- Head on gel ring or Mayfield
- Arms tucked at sides
- Fluoroscopy to confirm level
Approach Steps
Transverse skin crease incision (cosmetic) or longitudinal incision for multilevel. Left side preferred. Incise platysma in line with skin.
Identify medial border of sternocleidomastoid. Develop plane between carotid sheath laterally and trachea/esophagus medially. Blunt dissection to pretracheal fascia.
Divide pretracheal fascia. Identify anterior spine covered by longus colli. Confirm level with fluoroscopy using needle in disc.
Subperiosteal elevation of longus colli off anterior vertebral bodies. Elevate to expose uncovertebral joints (lateral limit of dissection). Place self-retaining retractor under longus colli.
The longus colli must be elevated carefully to protect the vertebral artery and sympathetic chain laterally.
Complications
Frequently encountered issues
| Complication | Incidence | Prevention/Management |
|---|---|---|
| Dysphagia | 30-50% transient, 2-5% persistent | Minimize retraction, deflate ETT cuff, shorter surgery |
| Hoarseness (RLN injury) | 2-5% transient, 0.2-1% permanent | Left-sided approach, gentle retraction, protect nerve |
| Hematoma | 1-2% | Meticulous hemostasis, consider drain |
| Pseudarthrosis | 5% single level, 15% multilevel | Use plate, cage with bone graft, no smoking |
| Adjacent segment disease | 2.5-4% per year | Minimize levels, consider disc replacement |
Dysphagia is the most common complication but usually resolves within weeks.
Postoperative Care
First 24-48 hours
Monitoring:
- Airway assessment (watch for hematoma)
- Neurological checks
- Pain management
- Dysphagia screening before oral intake
Red flags:
- Increasing neck swelling
- Stridor or respiratory distress
- New neurological deficit
Hematoma protocol:
- If airway compromise developing
- Open wound at bedside to decompress
- May need emergency intubation (can be very difficult)
- Return to OR for evacuation
First 48 hours critical for hematoma detection.
Outcomes and Prognosis
ACDF Outcomes by Indication
| Indication | Success Rate | Recovery Timeline | Factors Affecting Outcome |
|---|---|---|---|
| Radiculopathy | 85-95% | Arm pain improves within days/weeks | Duration of symptoms, motor deficit |
| Myelopathy | 70-80% stabilize/improve | May take 6-12 months | Preop severity, cord signal change |
| Disc herniation | 90-95% | Rapid improvement typical | Soft disc better than hard disc |
Prognostic factors:
Factors Affecting Outcomes
| Factor | Better Prognosis | Worse Prognosis |
|---|---|---|
| Symptom duration | Short (less than 6 months) | Prolonged (greater than 2 years) |
| Pathology type | Soft disc | Hard disc, severe spondylosis |
| Myelopathy signs | Mild, recent onset | Severe, long-standing, cord signal change |
| Number of levels | Single level | Multiple levels |
| Patient factors | Non-smoker, no diabetes | Smoker, diabetic, workers comp |
ACDF has excellent outcomes for radiculopathy; myelopathy outcomes depend on severity and duration.
Evidence Base
ACDF vs Conservative for Radiculopathy
- Faster arm pain relief with surgery
- Similar outcomes at 12 months
- Surgery indicated for failed conservative or progressive deficit
- Natural history of radiculopathy is favorable
ACDF vs Disc Replacement
- Similar clinical outcomes
- Motion preservation with TDR
- May reduce adjacent segment disease
- Not for myelopathy or significant instability
Plate vs No Plate
- Higher fusion rate with plate
- More benefit in multilevel cases
- May increase dysphagia rates
- Low-profile plates may reduce dysphagia
Surgical Timing in Myelopathy
- Better outcomes with earlier surgery
- Avoid delay beyond 6 months
- Cord signal change indicates poorer prognosis
- Progressive myelopathy is urgent
Left vs Right Approach
- Left-sided approach preferred
- RLN loops around aorta on left
- Right-sided RLN more variable
- Some surgeons prefer right for right-sided pathology
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Radiculopathy Management
"A 45-year-old man presents with 8 weeks of right arm pain radiating to the thumb with numbness. He has weakness of wrist extension. MRI shows a C5-6 disc herniation compressing the C6 nerve root."
Scenario 2: Myelopathy
"A 62-year-old woman presents with difficulty writing and buttoning clothes, unsteady gait, and electric shocks down her spine when she flexes her neck. Examination shows hyperreflexia and Hoffmann sign bilaterally. MRI shows multilevel stenosis C4-C7 with cord compression and T2 signal change in the cord at C5-6."
Scenario 3: Postoperative Complication
"You are called to see a patient 6 hours after ACDF who is developing stridor and has increasing neck swelling. The patient is becoming increasingly distressed."
MCQ Practice Points
Approach Side
Q: Which side is preferred for the anterior cervical approach and why?
A: Left side is preferred. The recurrent laryngeal nerve (RLN) on the left loops around the aortic arch, giving it a longer and more protected course, while the right RLN loops around the subclavian artery, making it shorter and more vulnerable to injury during retraction.
Disc-Root Relationship
Q: A C5-6 disc herniation will compress which nerve root?
A: C6 nerve root. In the cervical spine, the nerve root exits ABOVE the pedicle of the same-numbered vertebra, so the C5-6 disc affects the C6 root. This is opposite to the lumbar spine pattern.
Myelopathy Timing
Q: What is the recommended timing for surgical intervention in cervical myelopathy?
A: Early surgery is recommended - do not delay for conservative treatment. Evidence shows better outcomes when surgery is performed within 6 months of symptom onset. Myelopathy with progressive symptoms is urgent.
Complication Rates
Q: What is the rate of dysphagia after ACDF?
A: 50% transient dysphagia (usually resolves within weeks), with 2-5% persistent dysphagia. Dysphagia is the most common complication of ACDF.
Adjacent Segment Disease
Q: What is the annual rate of adjacent segment disease after cervical fusion?
A: 2.5-4% per year. This is similar to lumbar spine fusion. Total disc replacement may reduce this rate but evidence is limited.
Airway Emergency
Q: What is the immediate management of suspected postoperative hematoma with airway compromise?
A: Open the wound at the bedside to evacuate hematoma and relieve pressure on the airway. This should be done before or while attempting intubation, as intubation may be extremely difficult due to swelling.
Australian Context
ACDF is commonly performed across Australia in both public and private hospital settings. Surgical volume and experience correlate with outcomes, with high-volume spine centers typically concentrated in metropolitan areas.
Wait times for elective cervical spine surgery in public hospitals vary by state and urgency category. Myelopathy with progressive symptoms should be expedited through urgent pathways. Private health insurance generally provides faster access to elective procedures.
The Australian Spine Registry collects data on cervical spine procedures when participating, providing valuable national outcomes data. Surgeon training and credentialing follows established pathways through AOA and relevant spine society training programs.
Exam Cheat Sheet
ACDF - Anterior Cervical Discectomy and Fusion
High-Yield Exam Summary
Key Numbers
- •C5-6 most common level (55-65%)
- •Fusion rate: 95% single, 85% multilevel
- •Dysphagia: 50% transient, 2-5% persistent
- •Adjacent segment disease: 2.5-4%/year
Approach Anatomy
- •Left side preferred (RLN protection)
- •Carotid sheath retracted laterally
- •Trachea/esophagus retracted medially
- •Longus colli protects vertebral artery
Nerve Root Levels
- •C5-6 disc = C6 root compression
- •C6-7 disc = C7 root compression
- •Root exits ABOVE pedicle of same number
- •Different from lumbar spine pattern
Complications
- •Dysphagia (most common)
- •Hematoma (airway emergency)
- •RLN injury (hoarseness)
- •Pseudarthrosis (especially multilevel)
Exam Traps
- •Not knowing left vs right approach rationale
- •Wrong nerve root level correlation
- •Delaying surgery for myelopathy
- •Not recognizing hematoma emergency