High Yield Overview

POSTERIOR CERVICAL LAMINECTOMY AND FUSION

Posterior midline incision from inion (C2) to C7 spinous process | advanced

Critical Danger Structures - 5 Key Anatomical Zones

Danger 1: Spinal Cord

Location: Immediately anterior to lamina (0-2mm gap), cervical cord diameter 10mm

Protection: Thin lamina with burr before using Kerrison, use footplate attachments, stay in epidural space, avoid direct anterior pressure

Danger 2: Vertebral Artery

Location: Runs in foramen transversarium, 1.5-2mm lateral to lateral mass edge, anterior to C7 transverse process

Protection: Stay medial during lateral mass exposure, Magerl trajectory 25° lateral (not >30°), palpate all 4 walls before screw insertion, avoid lateral dissection beyond facet edge

Danger 3: C5 Nerve Root

Location: Exits above C5 pedicle (C4-5 foramen), shortest and most horizontal cervical root, 3-5mm from medial pedicle wall

Protection: Magerl technique 45° cephalad (not >50°), medial screw breach >4mm requires revision, foraminal decompression <50% facet resection, gentle nerve hook palpation

Danger 4: Epidural Venous Plexus

Location: Valveless Batson's plexus directly anterior to lamina (2-5mm from dura), engorges with increased abdominal pressure

Protection: Reverse Trendelenburg 15-20° positioning, thrombin-soaked gelfoam, bipolar cautery (not monopolar), TXA consideration, meticulous hemostasis before closure

Danger 5: Dura Mater

Location: 0-2mm anterior to ligamentum flavum (3-5mm thick yellow structure), adherent in OPLL cases

Protection: Thin lamina to eggshell before rongeur removal, identify ligamentum flavum (yellow), leave ossified dura intact in OPLL, repair tears primarily with 4-0 Nurolon

Mnemonic

LORDOSISLORDOSIS - Essential Considerations

Mnemonic

SCREW-INSCREW-IN - Lateral Mass Screw Safety

Primary Indications

Absolute Indications:

Multilevel cervical myelopathy (≥3 levels) with progressive neurological deficit
Cervical stenosis with PRESERVED cervical lordosis (20-40° C2-C7 Cobb angle)
OPLL (ossification of posterior longitudinal ligament) causing cord compression
Congenital cervical stenosis (canal diameter <13mm) with symptomatic myelopathy

Relative Indications:

Failed conservative management of multilevel stenosis (>3-6 months)
Multilevel spondylotic myelopathy with posterior predominant compression
Multilevel cervical radiculopathy not amenable to anterior approach
Combined central and foraminal stenosis across multiple levels

Contraindications

Absolute Contraindications:

Cervical KYPHOSIS (requires anterior column support first or combined approach)
Primarily anterior pathology (large disc herniation, anterior osteophytes) - ACDF better
Active cervical spine infection (pyogenic discitis, osteomyelitis)
Medical instability precluding prolonged anesthesia

Relative Contraindications:

Severe osteoporosis (T-score <-3.0) - screw purchase concerns
Previous posterior cervical surgery with scarring
Obesity with poor posterior neck anatomy exposure
Single or two-level disease (ACDF preferred for limited disease)
Loss of cervical lordosis <10° (consider combined approach)

Clinical Assessment

Myelopathy Signs (Upper Motor Neuron):

Hoffman's sign - flick distal phalanx middle finger causes thumb flexion
Inverted radial reflex - brachioradialis tap causes finger flexion (C5-6 lesion)
Hyperreflexia in lower extremities with clonus
Lhermitte's sign - neck flexion causes electric shock down spine
Gait disturbance - spastic gait, broad-based, circumduction

Radiculopathy Signs (Lower Motor Neuron):

C5 - deltoid/biceps weakness, reduced biceps reflex
C6 - wrist extension weakness, reduced brachioradialis reflex
C7 - triceps weakness, reduced triceps reflex
C8 - finger flexion weakness, grip strength reduced

Modified JOA Score (17 points):

Motor function upper extremity (0-5)
Motor function lower extremity (0-7)
Sensory upper extremity (0-2)
Sensory trunk and lower extremity (0-2)
Bladder function (0-1)
Score <12 indicates moderate-severe myelopathy requiring surgery

Positioning and Preparation

Patient Position: Prone position in Mayfield 3-pin head holder (4 finger-breadths above ears, 1cm above supraorbital ridge to avoid supraorbital nerve). Reverse Trendelenburg 15-20 degrees to reduce venous pressure. Shoulder tape traction caudally to expose C7-T1. Confirm neutral cervical alignment on lateral fluoroscopy - avoid flexion (cord compression) or extension (reduces canal diameter).

Padding and Monitoring:

Chest rolls shoulder to iliac crest (allows abdominal free breathing)
Padded knee and ankle supports (avoid peroneal nerve compression)
Arms tucked at sides or on arm boards <90° abduction
Eyes protected with ophthalmic ointment and taped closed
Foley catheter for cases >2 hours
Neuromonitoring electrodes (SSEPs, MEPs) after positioning

Step 1: Positioning and Exposure Planning

Positioning and Exposure Planning: Patient prone in Mayfield head holder with neck in NEUTRAL position - avoid flexion (cord compression) or extension (reduces canal diameter). Reverse Trendelenburg 15 degrees reduces epidural venous bleeding. Shoulder tape traction caudally exposes C7-T1. Mark midline with palpable spinous processes. Confirm C2 (largest palpable), C6 (carotid tubercle level), C7 (prominent). Use lateral fluoroscopy to mark skin incision from planned UIV to LIV.

Exam Pearl

Technical Tip: EXAM KEY: Neutral neck position critical - excessive flexion can cause spinal cord compression during surgery. Reverse Trendelenburg reduces venous pressure by 40-50%. Accurate level identification ESSENTIAL - count from C2 (axis) which is first palpable spinous process below occiput. Wrong level surgery is NEVER EVENT.

Dangers at this step

Spinal cord compression from positioning (flexion >10°)
Wrong level exposure (40% error with palpation alone in obesity)
Excessive venous bleeding (inadequate reverse Trendelenburg)
Brachial plexus injury from shoulder taping (>2kg traction)
Eye injury (pressure on globe from face positioning)

Step 2: Midline Incision and Subperiosteal Exposure

Midline Incision and Subperiosteal Exposure: Midline incision through skin and subcutaneous tissue. Identify avascular midline raphe between trapezius muscles. Incise down to nuchal ligament. Subperiosteal dissection with Cobb elevator staying on bone - detach semispinalis cervicis and multifidus from C2 spinous process and laminae. Expose lateral masses bilaterally to lateral edge of lateral mass (facet joint). Preserve C2 nerve root (greater occipital nerve) crossing C1-2 if possible. Self-retaining retractors maintain exposure.

Exam Pearl

Technical Tip: EXAM KEY: Subperiosteal dissection preserves segmental muscle innervation and reduces bleeding. Lateral dissection limit is LATERAL EDGE OF FACET JOINTS - going more lateral risks vertebral artery (1.5-2mm from lateral mass edge in foramen transversarium). Preserve C2 nerve if exposing C1-2 to avoid occipital neuralgia (15-20% if violated).

Dangers at this step

Vertebral artery injury (lateral dissection beyond facet edge)
Excessive bleeding from muscle (300-500mL typical blood loss)
C2 nerve injury causing occipital neuralgia (frontal/vertex pain)
Dural tear from aggressive subperiosteal dissection
Inadequate lateral exposure (insufficient decompression)

Step 3: Level Confirmation with Fluoroscopy

Level Confirmation with Fluoroscopy: Place marker (spinal needle or instrument) on spinous process and confirm level with lateral C-arm fluoroscopy. In cervical spine, nerve roots EXIT ABOVE their numbered vertebra (C5 root exits C4-5, unlike lumbar where L5 exits L5-S1). Identify C2 spinous process (bifid), C7 (longest, non-bifid). Count carefully from C2. Mark planned laminectomy levels with electrocautery on laminae.

Exam Pearl

Technical Tip: EXAM KEY: Wrong level surgery is NEVER EVENT. Cervical spine has 8 nerve roots but 7 vertebrae - C8 root exits C7-T1. Always confirm level BEFORE laminectomy. Palpation alone has 40% error rate in obese patients. Use lateral fluoroscopy with radiopaque marker on each level before decompression.

Dangers at this step

Wrong level laminectomy (medicolegal catastrophe)
Radiation exposure to surgeon and staff (use lead, distance)
C-arm collision with patient/head holder (coordinate with radiology tech)
Misidentification of C2 vs occiput or C1

Step 4: Lateral Mass Screw Insertion

Lateral Mass Screw Insertion: Insert lateral mass screws BEFORE laminectomy for maximum stability. Entry point: CENTER of lateral mass between superior and inferior articular processes. Two main techniques: MAGERL (25° lateral, 45° cephalad toward opposite eye socket) or ANDERSON (10° lateral, 30-40° cephalad parallel to facet). Drill 12-14mm depth. Palpate 4 walls with ball-tip probe checking for breach. Typical screw: 3.5mm diameter x 12-14mm length. Bicortical purchase not necessary. Start at lowest level and work cephalad.

Exam Pearl

Technical Tip: EXAM KEY: Magerl trajectory 25/45 (higher angles) has LARGER safe zone but risks nerve root injury if too medial. Anderson trajectory 10/30 (lower angles) is SAFER for nerve root but smaller margin for error. Key danger: MEDIAL breach >4mm = nerve root injury, LATERAL breach = vertebral artery (VA 1.5-2mm lateral to lateral mass). Palpate all 4 walls before screw insertion.

Dangers at this step

Medial breach causing nerve root injury (2-5% incidence)
Lateral breach causing vertebral artery injury (0.3-0.5%, catastrophic)
Anterior breach into carotid sheath or esophagus (rare)
Screw loosening in osteoporotic bone (augment with PMMA if needed)
Facet joint violation causing neck pain

Step 5: Laminectomy - Progressive Posterior Decompression

Laminectomy - Progressive Posterior Decompression: Start laminectomy at most stenotic level. Use high-speed burr with footplate attachment to thin lamina from midline laterally, staying in epidural space. Thin to eggshell thickness. Identify ligamentum flavum (thick yellow elastic tissue, hypertrophied in stenosis to 7-10mm). Use Kerrison rongeurs to complete laminectomy removing lamina, spinous process, and ligamentum flavum. Work from cephalad to caudad. Undercut facets bilaterally for lateral recess and foraminal decompression. Preserve >50% of facet joint to avoid iatrogenic instability.

Exam Pearl

Technical Tip: EXAM KEY: Ligamentum flavum is 3-5mm thick (hypertrophies to 7-10mm in stenosis), identified by YELLOW color. Dura is immediately anterior (0-2mm gap). Thin lamina with burr FIRST before rongeur to avoid dural injury. If OPLL present, leave ossified dura intact - attempting removal risks catastrophic CSF leak and cord injury (CSF fistula rate 50% if ossified dura violated).

Dangers at this step

Dural tear (5-8% incidence, higher with revision or OPLL)
Spinal cord injury from instrument penetration anteriorly
Epidural venous plexus bleeding (Batson's plexus, engorged if inadequate positioning)
Inadequate decompression laterally (residual foraminal stenosis)
Excessive facet resection causing iatrogenic instability

Step 6: Foraminal Decompression

Foraminal Decompression: Undercut medial aspect of facet joints bilaterally using Kerrison rongeurs. Remove 25-50% of facet joint medial portion to decompress nerve root in foramen. Nerve roots exit ABOVE pedicle at each level (C5 root exits above C5 pedicle in C4-5 foramen). Confirm adequate decompression by passing micro nerve hook into foramen - should slide freely without resistance. Avoid resecting >50% of facet which causes iatrogenic instability requiring fusion extension.

Exam Pearl

Technical Tip: EXAM KEY: Cervical foraminal stenosis often caused by UNCOVERTEBRAL JOINT (joints of Luschka) osteophytes anteriorly. May need anterior approach (ACDF) if predominantly anterior compression. Safe foraminal decompression: remove medial 25-50% of facet, stay on BONE (not soft tissue laterally where VA lies 1.5-2mm away). Nerve hook should pass freely without resistance.

Dangers at this step

Nerve root injury from excessive retraction or direct trauma
Vertebral artery injury (lateral dissection beyond bone edge)
Excessive facet resection (>50%) causing instability
Inadequate decompression leaving residual radiculopathy
Nerve root avulsion (gentle technique essential)

Step 7: Rod Contouring and Placement

Rod Contouring and Placement: Contour rods to match patient's cervical lordosis (normal 20-40 degrees C2-C7 Cobb angle). Goal is to MAINTAIN or RESTORE lordosis - kyphotic alignment leads to poor outcomes and swan-neck deformity. Connect rods to lateral mass screws bilaterally. Use rod holders to provisionally seat rods. May need to compress or distract at individual levels to achieve optimal alignment. Ensure rods are fully seated in screw heads before final tightening. Compression loads bone graft.

Exam Pearl

Technical Tip: EXAM KEY: Cervical lordosis MUST be maintained - post-laminectomy kyphosis occurs in 10-20% without fusion. Normal cervical lordosis 20-40° (C2-C7 Cobb angle). Rod diameter typically 3.5mm titanium. Compression across levels loads bone graft and closes laminectomy defect. Avoid excessive compression causing foraminal stenosis (nerve root impingement).

Dangers at this step

Loss of lordosis causing kyphotic malalignment (swan-neck deformity)
Rod-screw interface failure (inadequate seating)
Neurovascular injury during rod passage (especially first rod)
Malposition causing junctional kyphosis at UIV or LIV
Excessive compression causing foraminal stenosis

Step 8: Decortication and Bone Grafting

Decortication and Bone Grafting: Decorticate lateral masses bilaterally with high-speed burr or osteotome to expose bleeding cancellous bone. Remove outer cortex only - preserve medial wall adjacent to spinal canal. Decorticate between lateral mass screws creating fusion bed. Pack morselized bone graft (local autograft from removed lamina/spinous processes plus allograft or demineralized bone matrix) over lateral masses and between screws. Goal: posterolateral fusion mass connecting instrumented levels. BMP consideration (expensive AU$3000-5000, ectopic bone risk).

Exam Pearl

Technical Tip: EXAM KEY: Fusion is REQUIRED after laminectomy to prevent progressive kyphosis (up to 21% without fusion vs 0-2% with fusion). Autograft from removed bone is excellent but limited volume (30-50cc). Posterolateral fusion between lateral masses is gold standard. BMP accelerates fusion (faster by 2-3 months) but risk ectopic bone, seroma, dysphagia, expensive.

Dangers at this step

Inadequate fusion bed preparation (pseudarthrosis 5-10%)
BMP-related seroma requiring drainage (5-8% if BMP used)
Graft dislodgement into canal (rare, catastrophic cord compression)
Ectopic bone formation causing radiculopathy
Excessive decortication causing lateral mass fracture

Step 9: Final Tightening and Imaging

Final Tightening and Imaging: Perform final tightening of all set screws and locking caps in sequential manner to avoid construct strain. Torque to manufacturer specifications (typically 80-100 in-lb for 3.5mm systems). Obtain intraoperative lateral and AP fluoroscopy or plain radiographs to confirm: 1) Screw positions (no breaches), 2) Rod position and alignment, 3) Cervical lordosis maintained, 4) No hardware prominence. Address any malpositioned screws immediately - medial breach >4mm requires revision.

Exam Pearl

Technical Tip: EXAM KEY: Inadequate final tightening is common cause of hardware failure. Final imaging is MANDATORY to confirm correct screw placement and alignment. Post-op CT often performed to verify screw position - medial breach >4mm requires revision (nerve root risk). C5 palsy can manifest in recovery (delayed onset 24-48h) - monitor motor function hourly x 24h.

Dangers at this step

Screw loosening from inadequate torque (under-tightening)
Unrecognized screw malposition (medial or lateral breach)
Hardware prominence posteriorly causing wound breakdown
Junctional kyphosis at UIV or LIV (extend fusion if malaligned)
Loss of lordotic correction

Step 10: Meticulous Hemostasis

Meticulous Hemostasis: Achieve hemostasis with bipolar electrocautery focusing on epidural venous plexus, muscle edges, and bone surfaces. Use thrombin-soaked gelfoam over exposed dura. Bone wax on bleeding bone edges (use sparingly - inhibits fusion). Ensure no active bleeding before closure - cervical epidural hematoma is devastating complication (1-2% incidence). Consider tranexamic acid (TXA) 1g load + 1g over 8h to reduce blood loss by 30-40%. Irrigate copiously with antibiotic solution (1g vancomycin in 1L saline).

Exam Pearl

Technical Tip: EXAM KEY: Epidural hematoma causing cord compression is surgical EMERGENCY (1-2% incidence). Risk factors: multilevel surgery, bleeding disorders, epidural venous engorgement, inadequate hemostasis. Post-op neuro checks q1h first 24h. Any deterioration requires urgent MRI and emergent decompression if hematoma confirmed (within 6h to prevent permanent deficit).

Dangers at this step

Epidural hematoma with cord compression (1-2%, emergency decompression)
Excessive bleeding requiring transfusion (mean blood loss 300-500mL)
Hematoma causing wound dehiscence (superficial collection)
Seroma formation (especially if BMP used)
Inadequate hemostasis necessitating re-exploration

Step 11: Layered Closure with Drain

Layered Closure with Drain: Place 10Fr round drain in epidural space if extensive dissection or oozing (>5 levels, revision, BMP use). Bring drain out through separate stab incision lateral to main wound. Close in layers: 1) Muscle and nuchal ligament with 0 Vicryl interrupted sutures (restore posterior tension band), 2) Deep dermis with 2-0 Vicryl, 3) Subcuticular closure with 3-0 Monocryl, 4) Skin glue or steri-strips. Apply sterile dressing. Keep drain for 24-48h or until output <50mL/24h. Rigid cervical collar optional (many surgeons avoid with instrumented fusion).

Exam Pearl

Technical Tip: EXAM KEY: Drain reduces hematoma risk but increases infection risk slightly - use selectively for multilevel cases (>4 levels), revision, BMP cases. Collar NOT required with instrumented fusion (immediately stable construct). Early mobilization (day 1) recommended - reduces complications. Fusion takes 3-6 months cervical spine (faster than lumbar 6-12 months). CT at 3 months to assess bridging bone.

Dangers at this step

Wound infection (1-3% incidence, higher if drain >48h)
CSF leak if dural tear not repaired (post-op headache, clear drainage)
Drain site infection or persistent drainage
Wound dehiscence from hematoma or infection
Seroma requiring aspiration

Step 12: Post-operative Monitoring and Management

Post-operative Monitoring and Management: Neurological checks hourly for first 24 hours focusing on motor and sensory function. C5 palsy is most common nerve root injury post-cervical decompression (5-10% incidence) - manifests as deltoid/biceps weakness with or without pain. Usually delayed onset (24-48h). Mechanism: nerve root tethering with cord drift posteriorly after decompression. Management is expectant - most recover over 3-12 months (80-90% at 1 year). Obtain post-op cervical spine radiographs (AP, lateral) on day 1 to confirm alignment and hardware position. Early mobilization unless C5 palsy severe.

Exam Pearl

Technical Tip: EXAM KEY: C5 PALSY pathophysiology: spinal cord drift posteriorly after decompression (increased canal diameter) causes traction on C5 root which is shortest (25-30mm), most horizontal (90° from cord), and has least mobility of cervical roots. Risk factors: large decompression (>3 levels), significant pre-op cord compression, posterior cord shift >3mm on MRI, combined anterior-posterior surgery. Usually RECOVERS spontaneously (80-90% at 1 year). EMG at 3 weeks if no improvement to confirm axonal injury vs neurapraxia.

Dangers at this step

C5 palsy (5-10%, delayed onset 24-48h, usually recovers)
Epidural hematoma (1-2%, emergency if cord compression)
Respiratory compromise from anterior soft tissue swelling
Hardware-related dysphagia (rare with posterior approach)
Neurological deterioration requiring urgent imaging

Post-operative Care

Immediate Post-operative (0-24h):

Neurological checks hourly x 24h (motor/sensory all extremities)
Monitor for C5 palsy (deltoid/biceps weakness, delayed onset 24-48h)
Watch for epidural hematoma (acute neuro deterioration = emergency MRI)
Elevate head of bed 30-45° to reduce swelling
Drain output monitoring (remove when <50mL/24h, typically 24-48h)
Pain management: multimodal (paracetamol, NSAIDs, opioids PRN)

Early Mobilization (1-7 days):

Mobilize day 1 with physiotherapy (no collar needed with instrumented fusion)
Log-roll for bed mobility first 48h (comfort, not stability concern)
Deep breathing exercises and incentive spirometry (prevent atelectasis)
VTE prophylaxis: sequential compression devices, mobilization, chemical prophylaxis (enoxaparin 40mg daily) if low bleeding risk
Post-op radiographs (AP, lateral cervical spine) day 1 to confirm alignment and hardware

Discharge Planning (2-5 days typical):

Discharge when: mobilizing independently, pain controlled oral medications, no neurological deterioration, drain removed, wound dry
BLT precautions (bending, lifting >5kg, twisting) x 6 weeks
Wound care: keep dry x 10 days, remove sutures/staples at 10-14 days
Red flags: fever >38.5°C, wound drainage, neurological change, severe pain
Follow-up: 2 weeks (wound check), 6 weeks, 3 months, 6 months, 1 year

Rehabilitation Protocol:

Week 0-6: BLT precautions, gentle ROM exercises (active, no resistance)
Week 6-12: Progressive strengthening, isometric cervical exercises
Month 3+: Full activity as tolerated if fusion progressing on imaging
Return to work: sedentary 4-6 weeks, manual labor 3-6 months (after fusion confirmed)
Driving: when comfortable turning head (no collar), off opioids, 2-4 weeks typical

Imaging Follow-up:

Post-op day 1: AP and lateral cervical radiographs (baseline alignment, hardware)
6 weeks: Cervical radiographs (alignment, hardware, early fusion assessment)
3 months: CT cervical spine (assess fusion, bridging bone formation)
6 months: Flexion-extension radiographs (assess fusion stability)
1 year: CT if pseudarthrosis concern, otherwise clinical assessment

Fusion Assessment:

Radiographic fusion: bridging bone across fusion levels on CT
Dynamic fusion: <2mm translation or <5° angulation on flexion-extension
Time to fusion: 3-6 months cervical spine (faster than lumbar)
Pseudarthrosis if no bridging bone at 12 months on CT

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"A 62-year-old man presents with progressive hand clumsiness, gait instability, and bladder urgency. MRI shows multilevel cervical stenosis C3-C6 with cord signal change. Describe your surgical approach and technique in detail."

EXCEPTIONAL ANSWER

This patient has CERVICAL MYELOPATHY indicated by: hand clumsiness (upper motor neuron), gait instability (spastic), bladder urgency (cord compression), and MRI T2 hyperintensity (myelomalacia). Multilevel stenosis C3-C6 with preserved lordosis is IDEAL for posterior approach. SURGICAL PLAN: Posterior cervical laminectomy C3-C6 with lateral mass screw instrumentation and fusion. ALTERNATIVE would be multilevel ACDF but posterior preferred for >3 levels (single approach, maintains motion at C2-3 and C6-7). POSITIONING: Prone in Mayfield head holder, NEUTRAL neck position (avoid flexion → cord compression), reverse Trendelenburg 15° (reduce venous bleeding), shoulder tape traction (expose C6-7). TECHNIQUE: Midline incision, subperiosteal dissection to lateral facet edge bilaterally. Confirm levels with fluoroscopy (C2 bifid, C7 longest non-bifid). Insert lateral mass screws C3-C6 bilaterally BEFORE laminectomy using MAGERL technique (25° lateral, 45° cephalad, 12-14mm depth). Palpate 4 walls to confirm no breach. DECOMPRESSION: Burr lamina to eggshell thickness, identify ligamentum flavum (thick yellow), remove with Kerrison rongeurs C3-C6. Undercut facets medially 25-50% for foraminal decompression. Ensure adequate central and lateral decompression. FUSION: Contour rods to 30° lordosis, connect to screws bilaterally. Decorticate lateral masses, pack morselized autograft (local bone) plus allograft. Achieve meticulous hemostasis, place drain, layered closure.

VIVA SCENARIOStandard

EXAMINER

"Describe the anatomy relevant to lateral mass screw insertion. What are the key differences between Magerl and Anderson techniques?"

EXCEPTIONAL ANSWER

LATERAL MASS ANATOMY: Lateral mass is bony prominence between superior and inferior articular processes, unique to cervical spine C3-C7. Dimensions: 10-15mm height, 8-12mm width, 6-10mm anteroposterior depth. C3 has SMALLEST lateral mass (may need 3.0mm screw). C7 has LARGEST but anterior VA course risk. DANGER STRUCTURES: MEDIAL breach → nerve root (3-5mm from medial wall). LATERAL breach → vertebral artery (1.5-2mm from lateral mass edge in foramen transversarium). ANTERIOR breach → carotid sheath, esophagus. POSTERIOR breach → rare, screw prominence. MAGERL TECHNIQUE: Entry point CENTER of lateral mass. Trajectory 25° LATERAL (toward ear), 45° CEPHALAD (toward opposite eye socket). Depth 12-14mm. ADVANTAGE: LARGER safe zone for screw placement, better pullout strength. DISADVANTAGE: Higher medial breach risk if >25° lateral or >45° cephalad (nerve root injury). ANDERSON TECHNIQUE: Same entry point CENTER of lateral mass. Trajectory 10° LATERAL (more parallel to sagittal plane), 30° CEPHALAD (more parallel to facet joint). Depth 12-14mm. ADVANTAGE: SAFER for nerve root (lower angles), less medial breach risk. DISADVANTAGE: Smaller safe zone, slightly less pullout strength. SCREW SPECIFICATIONS: 3.5mm diameter (3.0mm if small lateral mass), 12-14mm length (unicortical), titanium. BICORTICAL purchase NOT necessary (risks anterior breach). Palpate 4 WALLS with ball-tip probe before screw insertion to confirm no breach.

VIVA SCENARIOStandard

EXAMINER

"A patient develops progressive deltoid weakness 24 hours after posterior cervical laminectomy C3-C6. What is your differential diagnosis and management?"

EXCEPTIONAL ANSWER

DIFFERENTIAL DIAGNOSIS: Most likely C5 PALSY (5-10% incidence post-cervical decompression). Alternatives: C5 nerve root compression from hematoma, screw malposition, inadequate foraminal decompression, or cord injury (rare). C5 PALSY FEATURES: Deltoid and biceps weakness (C5 myotome), with or without radicular pain. DELAYED ONSET 24-48h post-op is CLASSIC. Mechanism: spinal cord drifts POSTERIORLY after decompression (increased canal diameter) causing TRACTION on C5 root. C5 root is SHORTEST (25-30mm), most HORIZONTAL (90° from cord), and has LEAST MOBILITY of cervical roots. IMMEDIATE ASSESSMENT: Detailed neurological examination: C5 motor (deltoid abduction 0-5/5, biceps flexion), sensation (lateral arm), reflexes (biceps reduced). Check other levels (C4, C6-C8) to rule out broader injury. Urgent MRI cervical spine to EXCLUDE compressive hematoma (surgical emergency if present). MRI FINDINGS in C5 palsy: NO compression of nerve root or cord. May show nerve root edema at C5. Posterior cord shift >3mm on sagittal T2. NO epidural hematoma (would require emergency decompression). MANAGEMENT: C5 palsy is managed EXPECTANTLY (conservative). NO surgical intervention indicated (no compression to decompress). Physical therapy for shoulder mobilization and strengthening. Pain management with NSAIDs, gabapentin if neuropathic component. EMG at 3 WEEKS to differentiate axonotmesis vs neurapraxia. PROGNOSIS: 80-90% recover spontaneously over 3-12 months. Monitor with serial exams at 6 weeks, 3 months, 6 months, 1 year. RISK FACTORS: Large decompression >3 levels, severe pre-op cord compression, posterior cord shift >3mm on MRI, combined anterior-posterior surgery, pre-existing C5 radiculopathy.