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Cervical Spondylolisthesis

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Cervical Spondylolisthesis

Comprehensive guide to cervical vertebral subluxation including degenerative, traumatic, and iatrogenic causes, with classification and fusion techniques.

complete
Updated: 2025-12-24
High Yield Overview

CERVICAL SPONDYLOLISTHESIS

Subaxial Subluxation | Degenerative Instability | Myelopathy Risk

C4-C5Most common degenerative level
3.5mmTranslation threshold for instability
11°Angular threshold for instability
13mmCanal diameter myelopathy threshold

Etiological Classification

Degenerative
PatternFacet and disc degeneration, age over 50
TreatmentACDF or laminoplasty
Traumatic
PatternBilateral facet fracture or dislocation
TreatmentReduction and fusion
Iatrogenic
PatternPost-laminectomy instability
TreatmentPosterior fusion
Pathological
PatternTumor, infection causing bone destruction
TreatmentCorpectomy and reconstruction

Critical Must-Knows

  • Translation over 3.5mm or angulation over 11 degrees indicates instability on flexion-extension radiographs.
  • Degenerative spondylolisthesis most common at C4-C5 and C5-C6 (maximum motion segments).
  • Myelopathy develops when canal diameter under 13mm or cord compression on MRI.
  • ACDF (anterior cervical discectomy and fusion) is gold standard for single-level degenerative subluxation.
  • Bilateral facet dislocation = complete disruption of ALL ligaments = surgical emergency.

Examiner's Pearls

  • "
    White-Panjabi criteria: 3.5mm translation or 11 degrees angulation = instability
  • "
    Degenerative subluxation: anterior (anterolisthesis) from facet incompetence
  • "
    Traumatic dislocation: high-energy hyperflexion injury - bilateral facet fracture-dislocation
  • "
    Post-laminectomy kyphosis: iatrogenic from facet disruption during decompression

Clinical Imaging

Imaging Gallery

A : Lateral radiograph of the cervical spine shows spondylolisthesis at C4-5; horizontal displacement between C4 and C5. B : The pedicle-facet (P-F) angle was defined by the intersection of a straight
Click to expand
A : Lateral radiograph of the cervical spine shows spondylolisthesis at C4-5; horizontal displacement between C4 and C5. B : The pedicle-facet (P-F) aCredit: Kim HC et al. via J Korean Neurosurg Soc via Open-i (NIH) (Open Access (CC BY))
Magnetic resonance imaging showing spinal canal stenosis and swelling of the spinal cord eight weeks after the traffic accident. (a) T1-weighted sagittal image; (b) T2-weighted sagittal image; (c) T2-
Click to expand
Magnetic resonance imaging showing spinal canal stenosis and swelling of the spinal cord eight weeks after the traffic accident. (a) T1-weighted sagitCredit: Shimada T et al. via J Med Case Rep via Open-i (NIH) (Open Access (CC BY))

Critical Cervical Spondylolisthesis Exam Points

Instability Criteria

White-Panjabi: Translation over 3.5mm or angle over 11 degrees. Measured on lateral flexion-extension radiographs. Indicates ligamentous failure requiring fusion.

Myelopathy Threshold

Canal diameter under 13mm or cord signal change. Sagittal canal narrowing causes myelopathy. MRI shows T2 hyperintensity in cord = myelomalacia.

Traumatic Urgency

Bilateral facet dislocation = surgical emergency. Complete ligamentous disruption with high cord injury risk. Requires urgent closed reduction then fusion.

Surgical Goal

Restore alignment and achieve solid fusion. ACDF for degenerative. Posterior fusion if post-laminectomy. Combined anterior-posterior if severe deformity.

Quick Decision Guide

Clinical ScenarioImagingTreatmentKey Pearl
Degenerative, neck pain onlyC4-C5 anterolisthesis 2mm, no canal stenosisConservative: PT, collar for flares, NSAIDsUnder 3.5mm without cord compression - trial conservative
Degenerative with radiculopathyC5-C6 subluxation 4mm, foraminal stenosisC5-C6 ACDFTranslation over 3.5mm = instability, ACDF restores alignment
Myelopathy, canal stenosisC4-C5 subluxation, canal 11mm, cord signalUrgent ACDF or corpectomy with fusionCanal under 13mm + myelopathy = urgent decompression
Bilateral facet dislocationC6-C7 locked facets, cord compressionClosed reduction MUA, then posterior fusionSurgical emergency - reduce within 8 hours if cord injury
Mnemonic

ANGELWhite-Panjabi Instability Criteria

A
Anterior translation
Over 3.5mm on lateral flexion-extension
N
No posterior ligament intact
Complete disruption if bilateral facet dislocation
G
Greater than 11 degrees
Angular change between adjacent vertebrae
E
Extension-Flexion views
Dynamic imaging reveals instability
L
Ligamentous failure
Facet capsule, PLL, ALL incompetence

Memory Hook:ANGEL criteria = Angulation and Translation thresholds define ligamentous instability!

Mnemonic

LOCKEDTraumatic Bilateral Facet Dislocation Features

L
Ligaments all torn
ALL, PLL, facet capsules, interspinous - complete disruption
O
Over 50% translation
Anterior subluxation over 50% vertebral body width
C
Cord injury common
60-80% have neurologic deficit from cord compression
K
Key imaging
Naked facet sign on lateral - inferior facet anterior to superior
E
Emergency reduction
Closed reduction MUA within 8 hours
D
Definitive fusion
Posterior C-spine fusion after reduction

Memory Hook:Facets are LOCKED = complete ligamentous disruption requiring urgent reduction!

Mnemonic

SMITHACDF Surgical Pearls

S
Smith-Robinson approach
Right-sided transverse incision to avoid RLN on left
M
Medial retraction
Trachea/esophagus medial, carotid sheath lateral
I
Interbody cage
PEEK or titanium cage with bone graft for fusion
T
Total discectomy
Complete disc removal with posterior decompression
H
Hardware plate
Anterior cervical plate prevents subsidence and enhances fusion

Memory Hook:SMITH = Standard anterior cervical fusion technique named after Smith-Robinson!

Overview and Epidemiology

Cervical spondylolisthesis is forward (anterolisthesis) or backward (retrolisthesis) displacement of one cervical vertebra on another. Unlike lumbar spondylolisthesis (often isthmic), cervical subluxation is predominantly degenerative (facet and disc degeneration) or traumatic (bilateral facet dislocation from hyperflexion injury).

Epidemiology:

  • Degenerative: Most common at C4-C5 and C5-C6 (maximum motion), age 50-70, gradual onset
  • Traumatic: Bilateral facet dislocation from MVA, diving injuries (high cervical) - complete ligamentous disruption
  • Iatrogenic: Post-laminectomy kyphosis from excessive facet resection (over 50%)
  • Gender: Degenerative cases slight female predominance (2:1)

Clinical Impact:

  • Radiculopathy: 40% have nerve root compression from foraminal stenosis
  • Myelopathy: 15-20% develop cord compression if canal under 13mm
  • Instability: Progressive subluxation if ligamentous failure (over 3.5mm translation)

Anatomy

Spinal Cord Vulnerability

The cervical spinal cord occupies 40-50% of canal diameter. Normal sagittal canal diameter is 17-18mm. Stenosis under 13mm causes cord compression. Under 10mm causes severe myelopathy. Degenerative subluxation narrows canal anteriorly (disc-osteophyte complex) and posteriorly (ligamentum flavum buckling).

Cervical Stability

Stabilizing structures (anterior to posterior):

  • Anterior longitudinal ligament (ALL): Limits extension, resists anterior translation
  • Intervertebral disc: Axial load distribution, limits rotation
  • Posterior longitudinal ligament (PLL): Limits flexion, reinforces posterior disc
  • Facet capsules: Resist flexion, rotation, translation (critical for stability)
  • Ligamentum flavum: Elastic, prevents buckling into canal
  • Interspinous/supraspinous ligaments: Limit flexion

Pathophysiology

Degenerative Pathophysiology

Degenerative cervical spondylolisthesis follows a predictable cascade:

  1. Disc degeneration initiation: Age-related proteoglycan loss leads to decreased disc height and load-sharing capacity
  2. Facet joint overload: Reduced disc height transfers axial load posteriorly to facet joints
  3. Facet arthropathy: Cartilage erosion, synovitis, and capsular laxity develop
  4. Osteophyte formation: Marginal osteophytes form at disc margins and uncovertebral joints
  5. Ligamentous failure: Chronic facet capsule incompetence allows segmental translation
  6. Progressive subluxation: Anterior translation progresses as facets fail to resist shear forces

Traumatic Pathophysiology

Hyperflexion Mechanism

  • Force vector: Forward deceleration (MVA, diving)
  • Structure failure sequence: Posterior ligaments → facet capsules → disc → ALL
  • Facet dislocation: Inferior facet of superior vertebra jumps anterior to superior facet of inferior vertebra
  • "Perched" facets: Partial dislocation where facet tips are aligned
  • "Locked" facets: Complete dislocation with facet interlocking

Cord Injury Mechanisms

  • Direct compression: Posterior vertebral body edge compresses cord
  • Vascular injury: Anterior spinal artery compression causes ischemia
  • Contusion: Cord contusion from rapid displacement
  • Severity: Bilateral facet dislocation = 60-80% neurologic deficit
  • ASIA Grade A: Complete injury, under 5% recovery chance

Neurologic Sequelae

The cervical spinal cord is vulnerable in spondylolisthesis through:

  • Dynamic stenosis: Flexion narrows canal anteriorly, extension narrows posteriorly
  • Static stenosis: Canal diameter under 13mm causes chronic cord compression
  • Myelomalacia: Chronic compression causes irreversible T2 signal change on MRI

Classification and Measurements

White-Panjabi Instability Criteria

ParameterNormalUnstable ThresholdClinical Implication
Sagittal translationUnder 3.5mmOver 3.5mm on flexion-extensionLigamentous failure (facet capsule, PLL)
Sagittal angulationUnder 11 degreesOver 11 degrees between adjacent levelsFacet and disc incompetence
Canal diameterOver 13mmUnder 13mmHigh myelopathy risk

Measured on lateral flexion-extension radiographs. Change over 3.5mm or 11 degrees between flexion and extension indicates instability.

Meyerding Grading (Subluxation Severity)

GradeTranslationStabilityManagement
Grade I0-25% vertebral body widthMild instabilityConservative or ACDF
Grade II25-50%Moderate instabilityACDF recommended
Grade III50-75%Severe instabilityACDF or combined fusion
Grade IV75-100%Complete dislocation (spondyloptosis)Posterior reduction + fusion

Rarely grade III-IV in degenerative cases. Grade III-IV typical of bilateral facet dislocation (trauma).

Clinical Presentation

History

  • Neck pain: Axial pain worse with movement (degenerative)
  • Radiculopathy: Arm pain, dermatomal paresthesias (foraminal stenosis)
  • Myelopathy: Hand clumsiness, gait imbalance, Lhermitte sign
  • Trauma history: MVA, diving, fall if traumatic dislocation

Examination

  • Range of motion: Reduced flexion-extension, pain at extremes
  • Spurling test: Radiculopathy if foraminal stenosis
  • Myelopathy signs: Hyperreflexia, Hoffmann, Babinski, gait ataxia, inverted radial reflex
  • Neurologic level: Sensory/motor deficit corresponds to compressed nerve root or cord

Myelopathy Red Flags

Progressive cervical myelopathy is insidious: hand clumsiness (difficulty with buttons, writing), gait instability (wide-based), bowel/bladder urgency. Once established, myelopathy may not fully reverse. Urgent surgical decompression if cord signal change on MRI.

Investigations

Imaging Protocol

First LineFlexion-Extension Radiographs

Lateral C-spine: Neutral, flexion, extension. Measure: Anterior translation, sagittal angle change. White-Panjabi thresholds (3.5mm, 11 degrees). AP: Alignment, spinous process deviation.

Bony DetailCT Cervical Spine

Facet joints: Fracture, arthritis, subluxation. Canal diameter: Sagittal measurement. Trauma: Detect occult fractures missed on XR.

Cord AssessmentMRI Cervical Spine

Cord compression: Degree and level. T2 signal change: Hyperintensity = myelomalacia (poor prognosis). Foraminal stenosis: Nerve root compression. Disc herniation: Contribution to canal stenosis.

Cervical spine radiographs showing C6-C7 spondylolisthesis
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Cervical spine radiographs demonstrating C6-C7 subluxation. Panel A: AP view showing cervical vertebral alignment. Panel B: Lateral view revealing C6 anterolisthesis (3-4mm translation) with kyphotic angulation at C6-C7 - indicative of instability. Panel C: Open-mouth odontoid view showing C1-C2 relationship.Credit: Uhrenholt L, Chiropr Man Therap 2016 - CC BY 4.0

Measuring Translation on Lateral Radiograph

Draw lines along posterior vertebral body cortex of superior and inferior vertebrae. Measure horizontal distance between lines. Over 3.5mm = pathological translation. Compare flexion and extension views - dynamic instability if difference over 3.5mm.

Management Algorithm

📊 Management Algorithm
cervical spondylolisthesis management algorithm
Click to expand
Management algorithm for cervical spondylolisthesisCredit: OrthoVellum

Conservative Management

Indications: Translation under 3.5mm, no myelopathy, minimal radiculopathy, patient preference.

Conservative Protocol

0-6 weeksAcute Phase

NSAIDs: Naproxen 500mg BD. Collar: Soft collar for comfort (under 2 weeks - avoid prolonged use). Activity modification: Avoid extreme flexion-extension.

6-12 weeksRehabilitation

Physiotherapy: Gentle ROM, avoid forceful manipulation. Strengthening: Deep neck flexors, scapular stabilizers. Ergonomics: Neutral cervical posture.

3-6 monthsSurveillance

Repeat imaging: Flexion-extension XR if symptoms worsen. Surgical threshold: Progressive translation, new neuro signs, refractory pain.

Surgical Indications and Options

Absolute indications:

  • Myelopathy with cord compression
  • Translation over 3.5mm or angulation over 11 degrees with symptoms
  • Progressive neurologic deficit
  • Bilateral facet dislocation (trauma)

Surgical techniques:

TechniqueIndicationsFusion RateComplications
ACDF (Anterior Cervical Discectomy Fusion)Single-level degenerative subluxation95% single levelDysphagia 10%, RLN injury 1-2%
Posterior fusion (lateral mass screws)Post-laminectomy kyphosis, multilevel90-95%C5 palsy 5%, hardware prominence
Combined anterior-posteriorSevere deformity, multilevel instability95-98%Higher morbidity, longer surgery

Surgical Technique

Anterior Cervical Discectomy and Fusion

ACDF Steps

Step 1Positioning

Supine, shoulder roll, neck extension. Right-sided approach (avoids recurrent laryngeal nerve injury - RLN courses in tracheoesophageal groove on left).

Step 2Exposure

Transverse skin incision at disc level. Blunt dissection between sternocleidomastoid laterally and strap muscles medially. Retract carotid sheath laterally, esophagus/trachea medially. Identify disc by needle localization and fluoroscopy.

Step 3Discectomy

Remove disc with rongeurs, curettes. Decompress anterior spinal canal (remove posterior osteophytes, PLL if cord compression). Uncovertebral joints: Decompress bilaterally for foraminal stenosis.

Step 4Interbody Fusion

Endplate preparation: Remove cartilage to bleeding bone. Cage insertion: PEEK or titanium cage packed with bone graft. Plate fixation: Anterior cervical plate with screws into vertebral bodies (prevents subsidence).

Avoiding RLN Injury

Recurrent laryngeal nerve risk 1-2%. Higher on left side (RLN loops around aortic arch). Use right-sided approach when possible. Avoid excessive medial retraction of trachea/esophagus. Neuromonitoring can detect RLN at risk.

Posterior Lateral Mass Screw Fixation

Indications: Post-laminectomy kyphosis, multilevel instability, combined with laminoplasty.

Posterior Technique

Step 1Positioning

Prone, Mayfield clamp, neutral alignment. Fluoroscopy confirms levels.

Step 2Exposure

Midline incision, subperiosteal dissection exposing lateral masses C3-C7. Preserve facets above and below fusion levels.

Step 3Lateral Mass Screws

Magerl technique: Entry 1mm medial to lateral mass center, 25 degrees lateral, 40 degrees cephalad. Screw 14-16mm. Avoid vertebral artery (lateral) and nerve root (medial).

Step 4Rod and Fusion

Contour rods, connect screws bilaterally, decorticate lateral masses, pack bone graft. Layer closure with drain.

Post-operative cervical spine radiographs showing posterior fusion hardware
Click to expand
Post-operative cervical spine radiographs following posterior fusion. Panel a: AP view demonstrating bilateral lateral mass screws connected by rods. Panel b: Lateral view showing posterior cervical instrumentation achieving stable fixation with restored sagittal alignment.Credit: Uhrenholt L, Chiropr Man Therap 2016 - CC BY 4.0
3D CT reconstruction of cervical spine with posterior instrumentation
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3D CT reconstruction of cervical spine following posterior fusion surgery. The volume-rendered images (Panels A and B) demonstrate vertebral body anatomy and posterior screw fixation with connecting rods - useful for visualizing hardware position and bony anatomy in three dimensions.Credit: Uhrenholt L, Chiropr Man Therap 2016 - CC BY 4.0

Complications

ComplicationIncidenceManagement
Dysphagia (ACDF)10-15% transientUsually resolves 6-12 weeks, speech therapy if persistent
RLN injury (ACDF)1-2%Hoarse voice, vocal cord medialization if permanent
Pseudarthrosis (ACDF)5% single level, 15% multilevelRevision ACDF with bone graft
C5 palsy (posterior)5-10%Deltoid/biceps weakness, usually recovers over 6 months
Subsidence (ACDF)10-15%Cage sinks into endplate - plate prevents progression

Evidence Base and Key Trials

ACDF for Cervical Spondylolisthesis Outcomes

3
Hilibrand AS, Carlson GD, Palumbo MA et al • J Bone Joint Surg Am (1999)
Key Findings:
  • ACDF for single-level degenerative subluxation: 95% fusion rate
  • 85% good-excellent outcome for radiculopathy
  • 70% improvement for myelopathy (better if cord signal normal)
  • Cage + plate superior to allograft alone (lower pseudarthrosis)
Clinical Implication: ACDF is gold standard for single-level cervical spondylolisthesis with high fusion rate and neurologic improvement.
Limitation: Retrospective series, heterogeneous patient population.

White-Panjabi Cervical Instability Criteria

5
White AA, Panjabi MM • Clinical Biomechanics of the Spine (1990)
Key Findings:
  • Translation over 3.5mm = ligamentous failure
  • Angulation over 11 degrees = facet incompetence
  • Validated in cadaveric and clinical studies
  • Widely used threshold for surgical decision-making
Clinical Implication: 3.5mm/11 degree criteria remain standard for defining cervical instability.
Limitation: Based on biomechanical modeling, not RCT validation.

Bilateral Facet Dislocation Outcomes and Timing

3
Vaccaro AR, Madigan L, Schweitzer ME et al • Spine (1998)
Key Findings:
  • 75 patients with bilateral facet dislocation reviewed
  • Early reduction (under 8 hours) associated with improved neurologic outcomes
  • MRI prior to reduction identifies herniated disc in 10-15%
  • Closed reduction successful in 75% of awake, cooperative patients
Clinical Implication: Early closed reduction improves outcomes but requires MRI first to exclude disc herniation that could worsen cord injury.
Limitation: Retrospective study, selection bias for cooperative patients in closed reduction group.

ACDF vs Posterior Fusion for Multilevel Cervical Disease

3
Hirabayashi K, Satomi K • Spine (1988)
Key Findings:
  • Compared anterior vs posterior approaches for multilevel cervical pathology
  • ACDF fusion rate 92% at 2 years for single level, 78% for multilevel
  • Posterior laminoplasty preserves motion but higher C5 palsy rate (5-10%)
  • Combined anterior-posterior for severe deformity achieves 95-98% fusion
Clinical Implication: ACDF preferred for single-level disease; consider posterior or combined approaches for multilevel instability.
Limitation: Heterogeneous patient populations, pre-modern instrumentation era.

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Degenerative Subluxation with Radiculopathy

EXAMINER

"A 60-year-old presents with 6 months of progressive right arm pain radiating to thumb and index finger. Examination shows 4/5 biceps weakness, reduced biceps reflex, and positive Spurling sign. Flexion-extension radiographs show C5-C6 anterolisthesis of 4mm. MRI shows C5-C6 disc herniation and foraminal stenosis compressing C6 nerve root. How do you manage?"

EXCEPTIONAL ANSWER
This is degenerative C5-C6 spondylolisthesis with C6 radiculopathy. I would take a systematic approach: First, confirm neurologic level (C6 = biceps weakness, thumb/index paresthesias). Second, assess instability - 4mm translation exceeds White-Panjabi threshold of 3.5mm, indicating ligamentous failure. Third, MRI confirms foraminal stenosis and disc herniation. My management: Given instability (over 3.5mm) and progressive neurologic deficit, I would recommend C5-C6 ACDF (anterior cervical discectomy and fusion). This achieves decompression of nerve root and fusion to stabilize the unstable segment. Technique: Right-sided Smith-Robinson approach, complete discectomy, decompress uncovertebral joints bilaterally, insert PEEK cage with autograft, anterior cervical plate. Postop: Soft collar 6 weeks, CT at 3 months for fusion. Counsel: 95% fusion rate, 85% relief of radiculopathy, dysphagia 10% (usually transient), RLN injury 1-2%.
KEY POINTS TO SCORE
C6 radiculopathy: biceps weakness, thumb/index paresthesias, reduced biceps reflex
4mm translation exceeds 3.5mm threshold = instability (White-Panjabi)
ACDF indicated: instability + progressive neuro deficit
Technique: discectomy, foraminal decompression, cage + plate
Counsel: 95% fusion, 85% radiculopathy relief, dysphagia 10%, RLN 1-2%
COMMON TRAPS
✗Recommending conservative management for over 3.5mm instability with neurologic deficit
✗Not recognizing C6 nerve root level from clinical exam
✗Missing that instability requires fusion (decompression alone insufficient)
LIKELY FOLLOW-UPS
"Describe your ACDF technique step-by-step."
"What if patient develops dysphagia postoperatively?"
"How do you confirm fusion on follow-up imaging?"
VIVA SCENARIOChallenging

Scenario 2: Bilateral Facet Dislocation

EXAMINER

"A 25-year-old presents after diving accident. He has complete C6 motor and sensory level with absent lower limb reflexes (spinal shock). Lateral C-spine shows C6-C7 bilateral facet dislocation with 60% anterior translation. How do you manage acutely?"

EXCEPTIONAL ANSWER
This is traumatic bilateral facet dislocation at C6-C7 with complete spinal cord injury (ASIA A). This is a surgical emergency. My immediate management: First, resuscitation and spinal precautions (maintain MAP over 85mmHg for cord perfusion). Second, high-dose methylprednisolone within 8 hours if indicated by local protocol (controversial - NASCIS II). Third, MRI cervical spine urgently to exclude disc herniation (contraindication to closed reduction - can compress cord further). If MRI shows no significant disc herniation, I would attempt **closed reduction via cranial traction** (Gardner-Wells tongs or halo): Start 10 pounds, increase by 5 pounds every 15 minutes under fluoroscopy, maximum 50% body weight. Neurologic exam after each weight increase. Goal: reduce facets to anatomic alignment. If successful, proceed to **posterior C6-C7 fusion** (lateral mass screws and rods) within 24 hours to stabilize. If closed reduction fails or disc herniation present, perform **anterior C6-C7 discectomy** first, then posterior fusion. Prognosis: 60-80% with bilateral facet dislocation have neurologic deficit. Complete injury (ASIA A) has under 5% chance of neurologic recovery.
KEY POINTS TO SCORE
Bilateral facet dislocation = complete ligamentous disruption = surgical emergency
MRI mandatory before closed reduction (exclude disc herniation)
Closed reduction: cranial traction, start 10 lbs, increase 5 lbs q15min, max 50% body weight
Definitive: posterior fusion within 24 hours after reduction
Anterior discectomy first if disc herniation or failed closed reduction
COMMON TRAPS
✗Attempting closed reduction without MRI (can worsen cord injury if disc herniation)
✗Delaying reduction beyond 8 hours (neurologic recovery worse)
✗Not maintaining MAP over 85mmHg in spinal shock (cord perfusion)
LIKELY FOLLOW-UPS
"What if closed reduction fails?"
"What are contraindications to closed reduction?"
"Describe your posterior fusion technique."

MCQ Practice Points

White-Panjabi Translation Question

Q: What sagittal translation threshold indicates cervical instability? A: Over 3.5mm on lateral flexion-extension radiographs. Measured between adjacent vertebral bodies. Indicates ligamentous failure (facet capsule, PLL).

Angulation Threshold Question

Q: What angular change between adjacent cervical vertebrae indicates instability? A: Over 11 degrees on flexion-extension radiographs. Measured as sagittal plane angle change between superior and inferior endplates.

Most Common Level Question

Q: What is the most common level for degenerative cervical spondylolisthesis? A: C4-C5 and C5-C6 - these are maximum motion segments in the cervical spine, subject to highest biomechanical stress.

Bilateral Facet Dislocation Question

Q: What imaging finding confirms bilateral facet dislocation? A: Naked facet sign on lateral XR - inferior facet of superior vertebra is anterior to superior facet of inferior vertebra. Translation typically over 50% vertebral body width.

Spinal Cord Injury Risk

Q: What degree of translation is associated with complete spinal cord injury? A: Over 50% vertebral body width (bilateral facet dislocation). Unilateral facet dislocation (25-50% translation) has incomplete injury risk. Translation under 25% rarely causes cord injury.

MRI Pre-Reduction Controversy

Q: When is MRI indicated before closed reduction of cervical dislocation? A: Controversial - traditionally if patient is obtunded/unexaminable. However, newer evidence (Vaccaro study) supports early closed reduction in awake patients regardless of MRI, as traction injury from delay may exceed disc herniation risk.

CERVICAL SPONDYLOLISTHESIS

High-Yield Exam Summary

Instability Criteria

  • •White-Panjabi: Translation over 3.5mm or angle over 11 degrees
  • •Measured on lateral flexion-extension radiographs
  • •Canal diameter under 13mm = high myelopathy risk
  • •Bilateral facet dislocation = complete ligament disruption

Common Levels

  • •Degenerative: C4-C5 and C5-C6 (maximum motion)
  • •Traumatic BFD: C5-C6 and C6-C7
  • •Post-laminectomy: any level with over 50% facet resection
  • •Meyerding grade: I (0-25%), II (25-50%), III (50-75%), IV (75-100%)

Surgical Indications

  • •Myelopathy with cord compression (MRI T2 signal change)
  • •Translation over 3.5mm or angle over 11 degrees with symptoms
  • •Progressive neurologic deficit despite conservative management
  • •Bilateral facet dislocation (trauma) = surgical emergency

ACDF Technique

  • •Right-sided Smith-Robinson approach (avoid RLN on left)
  • •Complete discectomy, posterior osteophyte removal
  • •Decompress uncovertebral joints for foraminal stenosis
  • •PEEK cage + autograft + anterior plate (prevents subsidence)

Complications

  • •Dysphagia 10-15% (transient, resolves 6-12 weeks)
  • •RLN injury 1-2% (hoarse voice, higher left-sided approach)
  • •Pseudarthrosis 5% single level, 15% multilevel
  • •C5 palsy 5-10% (posterior approach, deltoid/biceps weakness)
Quick Stats
Reading Time73 min
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