import { OnePagerSummary, ContentSection, ExamWarning, InfoCardGrid, InfoCard, EvidenceCard, ComparisonTable, VivaScenario, MnemonicCard, ExamCheatSheet, Tab, Tabs } from '@/components/mdx' 18mm risks anterior cortex perforation into VA foramen). Maintains 3-5mm safety margin from VA.", "**C5 nerve root palsy MOST COMMON complication**: 4.6-11% after laminoplasty (Sakaura 2003), presents 1-7 days postop as deltoid/biceps weakness MRC 2-3/5 with preserved hand function. Mechanism: posterior cord shift (3-5mm) after decompression tethers short C5 root exiting C4-5 foramen. 70% recover to MRC 4/5 by 12 months, 30% PERMANENT MRC 3/5 weakness.", "**Laminoplasty vs laminectomy**: Laminoplasty preserves posterior tension band (15-25% axial pain, maintains lordosis) vs laminectomy without fusion (50-60% kyphotic deformity - Ratliff 1993). OPLL >60% canal occupancy favors laminoplasty (avoid direct dural manipulation - Iwasaki 2007).", "**C2 muscle preservation reduces axial pain**: Subperiosteal dissection preserving semispinalis cervicis and multifidus insertion on C2 spinous process reduces axial pain from 60% to 25% (Hosono 1996). C7 pedicle screws most reliable (97% safe corridor, 5-7mm diameter - Karaikovic 1997)." ]} examPearls={[ "C5 palsy prevention: Prophylactic C4-5 foraminotomy on laminoplasty opening side reduces palsy from 10.2% to 3.8% (Katsumi 2003) - releases tethered root, reduces posterior cord shift traction.", "Preoperative CT angiography if anomalous VA suspected: 10-15% have high-riding VA at C2 level, 5% have VA entering at C3 (typical C6 entry) - alters screw trajectory planning.", "C2 pars screws safer than pedicle screws: 5-8mm pars width vs 3-5mm pedicle width, 2% VA injury risk (Harms 2001 technique). C7 pedicle screws most reliable subaxial level (97% safe corridor).", "VA injury management: Immediate tamponade with bone wax, vascular surgery consult for ligation or endovascular coiling. Unilateral VA ligation tolerated if contralateral patent, but 5-10% risk brainstem/cerebellar infarction.", "Lateral mass screw length critical: 14-16mm max (>18mm penetrates anterior cortex into transverse foramen where VA courses) - measure on preop CT axial images." ]} summary="The posterior approach to the cervical spine provides comprehensive access to the subaxial spine (C3-C7) for decompression (laminectomy, laminoplasty) and instrumentation (lateral mass screws C3-C6, pedicle screws C7, C2 pars/pedicle screws) in multilevel cervical stenosis, OPLL, and subaxial trauma. The approach utilizes a midline posterior incision with subperiosteal muscle dissection to expose the posterior elements while preserving critical C2 muscle attachments (semispinalis cervicis, multifidus) to minimize axial neck pain. The vertebral artery is the MOST IMPORTANT structure at risk, coursing through the transverse foramen 3-5mm anterior to the lateral mass screw entry point - using Magerl technique (25° lateral, 25° cephalad trajectory, 14-16mm screw length) reduces VA injury to 0.2-0.5% compared to 2.8% with straight lateral trajectory. C5 nerve root palsy is the MOST COMMON neurological complication (4.6-11% after laminoplasty) caused by posterior cord shift (3-5mm) after decompression tethering the short C5 root exiting C4-5 foramen - prophylactic C4-5 foraminotomy reduces incidence from 10.2% to 3.8%. Laminoplasty preserves the posterior tension band and reduces kyphotic deformity (15-25% axial pain) compared to laminectomy without fusion (50-60% kyphosis), and is preferred for OPLL >60% canal occupancy where direct dural manipulation is hazardous. C2 muscle preservation through subperiosteal dissection reduces postoperative axial neck pain from 60% to 25%. C7 pedicle screws are the most reliable subaxial trajectory (97% safe corridor, 5-7mm diameter), while C2 pars screws are safer than C2 pedicle screws (5-8mm pars width vs 3-5mm pedicle)." /> # Posterior Approach to Cervical Spine The **posterior approach to the cervical spine** provides access to the subaxial spine (C3-C7) for: (1) **Decompression** (laminectomy, laminoplasty for multilevel stenosis or OPLL), (2) **Instrumentation** (lateral mass screws C3-C6, pedicle screws C7, C2 pars/pedicle screws), and (3) **Fusion** (posterior wiring, facet fusion, instrumented posterolateral fusion). This approach is **IDEAL for multilevel cervical stenosis** (greater than or equal to 3 levels), **ossification of posterior longitudinal ligament (OPLL)**, and **subaxial trauma** requiring posterior stabilization. **Key Anatomical Relationships:** - **Vertebral artery**: Courses through transverse foramen at C2-C6, 3-5mm ANTERIOR to lateral mass screw entry point (AN 1994) - MOST IMPORTANT structure at risk during lateral mass screw insertion - **C5 nerve root**: Exits C4-5 foramen, vulnerable to traction/tethering during decompression (4.6-11% palsy rate after laminoplasty - Sakaura 2003) - **Spinal cord**: 10-12mm diameter at C5-C6 level (largest in cervical spine), canal diameter 14-16mm (normal), spinal cord occupies 70-80% of canal in stenosis - **C2 muscle attachments**: Semispinalis cervicis and multifidus insert on C2 spinous process - preservation reduces axial neck pain from 60% to 25% (Hosono 1996) **Historical Context:** Posterior cervical laminectomy introduced by **Charles Elsberg (1913)** for spinal cord tumor decompression. Lateral mass screw fixation developed by **Roy-Camille (1972)** and refined by **Magerl (1987)** with divergent trajectory to avoid vertebral artery. Laminoplasty pioneered by **Hirabayashi (1977, Japan)** to preserve posterior tension band and reduce kyphotic deformity. ## Bony Anatomy - Subaxial Cervical Spine (C3-C7) ### Typical Cervical Vertebra (C3-C6) - **Vertebral body**: Anteroposterior (AP) diameter 15-18mm, mediolateral (ML) width 20-25mm, height 12-15mm - **Pedicle**: Transverse diameter 5-7mm (C3-C5), 6-8mm (C6-C7), sagittal height 7-9mm, medial angulation 40-45° (converges toward spinal canal) - **Lateral mass**: Rectangular pillar between superior and inferior articular processes, dimensions 10-12mm AP × 12-15mm ML × 10-12mm height (C3-C6) - **Facet joint**: Oriented 45° to coronal plane (allows flexion-extension), capsule innervated by medial branch of posterior ramus (facet-mediated axial pain common after posterior instrumentation) - **Spinous process**: Bifid at C3-C6 (except C7 which is prominens, non-bifid), serves as attachment for nuchal ligament and semispinalis cervicis muscle - **Transverse foramen**: Houses vertebral artery at C6-C2 (VA enters at C6, exits at C2 to curve posteriorly around C1 lateral mass), diameter 5-7mm ### C7 Vertebra (Transitional Anatomy) - **"Vertebra prominens"**: Non-bifid spinous process (long, palpable landmark for level identification) - **Pedicle diameter**: 5-7mm transverse, 7-9mm sagittal (LARGEST cervical pedicle, most reliable for pedicle screw placement - Karaikovic 1997) - **Transverse foramen**: May NOT contain vertebral artery (10% of population, VA enters at C6 but passes ANTERIOR to C7 transverse process, does not traverse foramen) - **Superior articular facets**: Orient more coronally (similar to thoracic spine) vs typical cervical facet at 45° ## Neurovascular Anatomy ### Spinal Cord and Nerve Roots - **Cervical spinal cord**: Diameter 10-12mm at C5-C6 (largest cervical level), 8-10mm at C7-T1 (cervical enlargement extends C5-T1) - **Spinal canal dimensions**: AP diameter 14-16mm (normal), less than 13mm = relative stenosis, less than 10mm = absolute stenosis (OPLL criteria) - **Nerve root anatomy**: - **C5 root**: SHORTEST cervical root (10-12mm from cord to foramen), exits C4-5 foramen at 45° angle, innervates deltoid (C5), biceps (C5-C6), courses ANTERIOR to lateral mass at C4-5 level - **C6 root**: Exits C5-6 foramen, innervates biceps (C5-C6), wrist extensors (C6), brachioradialis (C5-C6) - **C7 root**: Exits C6-7 foramen, innervates triceps (C7), wrist flexors (C7), finger extensors (C7) - **C8 root**: Exits C7-T1 foramen, innervates finger flexors (C8), intrinsic hand muscles (C8-T1) ### Vertebral Artery Course The vertebral artery (VA) courses through the transverse foramen at C6-C2, with CRITICAL relationships to bony landmarks: | Level | VA Position Relative to Lateral Mass | Distance from Lateral Mass Screw Trajectory | Clinical Implication | |-------|---------------------------------------|---------------------------------------------|---------------------| | **C2** | Courses posteriorly around C2 lateral mass in sulcus arteriosus (gutter on C2 superior surface) | 2-3mm (HIGHEST RISK for C2 pars/pedicle screws) | High-riding VA in 10-15% (CTA preoperatively), C2 pars screws safer than pedicle screws (5-8mm pars width vs 3-5mm pedicle) | | **C3** | Transverse foramen ANTERIOR to lateral mass | 3-5mm | Magerl trajectory (25° lateral, 25° cephalad) maintains safety margin | | **C4** | Transverse foramen ANTERIOR to lateral mass | 3-5mm | Safest level for lateral mass screws (no anomalous VA) | | **C5** | Transverse foramen ANTERIOR to lateral mass | 3-5mm | Safest level for lateral mass screws | | **C6** | VA enters transverse foramen from ANTERIOR (off carotid artery or aortic arch) | 4-6mm (VA more anterior at entry level) | Screw length less than 16mm (avoid anterior cortex perforation into VA entry zone) | | **C7** | VA may NOT traverse transverse foramen (passes ANTERIOR to C7 in 10% of population) | 5-7mm (if VA present in foramen) | Pedicle screws SAFE (VA rarely in C7 foramen), C7 most reliable pedicle screw site | **Anomalous VA Anatomy (10-15% incidence):** - **High-riding VA at C2**: VA enters transverse foramen at C3 instead of C6 (courses LATERAL to C3 lateral mass, 0mm safety margin for C3 lateral mass screws) - **Dominant VA**: One VA larger than contralateral (10% have dominant left VA supplying 70-80% of posterior circulation), unilateral injury may cause brainstem/cerebellar infarction - **Hypoplastic/atretic VA**: One VA congenitally absent or thread-like (3-5% incidence), contralateral VA supplies entire posterior circulation (CRITICAL to preserve patent VA during instrumentation) ### Venous Anatomy - **Epidural venous plexus**: Valveless Batson's plexus surrounds spinal cord, high-flow low-pressure system, MAJOR source of bleeding during laminectomy (tamponade with hemostatic agents - Surgicel, thrombin-soaked gelfoam, bipolar cautery at LOW settings to avoid thermal cord injury) - **Vertebral venous plexus**: Surrounds VA in transverse foramen, may bleed profusely if injured during lateral mass screw placement (tamponade with bone wax) ### Muscular Anatomy - Posterior Cervical Musculature The posterior cervical muscles are dissected in LAYERS during posterior approach: | Layer | Muscles | Nerve Supply | Function | Dissection Considerations | |-------|---------|--------------|----------|---------------------------| | **Superficial** | Trapezius | Spinal accessory nerve (CN XI) + C3-C4 (proprioception) | Shoulder elevation, scapular retraction | Midline incision splits trapezius raphe (avoids denervation) | | **Intermediate** | Splenius capitis, splenius cervicis | Posterior rami C2-C6 | Neck extension, ipsilateral rotation | Subperiosteal dissection preserves innervation | | **Deep** | Semispinalis cervicis, semispinalis capitis, multifidus | Posterior rami C2-C6 | Neck extension, fine motor control | **C2 MUSCLE PRESERVATION**: Semispinalis cervicis inserts on C2 spinous process - detachment causes 60% axial pain rate, preservation reduces to 25% (Hosono 1996) | | **Deepest** | Rotatores, intertransversarii | Posterior rami (segmental) | Proprioception, fine segmental control | Subperiosteal dissection from C3-C7 spinous processes and laminae | **C2 Muscle Preservation Technique:** Traditional posterior cervical approach detaches semispinalis cervicis from C2 spinous process (causes denervation, axial pain, reduced neck extension strength). **Modified technique** (Hosono 1996): (1) Subperiosteal dissection STARTING at C3 (preserves C2 muscle insertion), (2) Partial C2 laminectomy if needed (undercut C2 lamina from inferior, preserve superior attachments), (3) Avoid C1-C2 exposure unless atlantoaxial fusion required. This reduces axial pain from 60% to 25% (Hosono 1996). ## Indications ### Degenerative Conditions 1. **Multilevel cervical stenosis** (greater than or equal to 3 levels, C3-C7): Laminoplasty or laminectomy with fusion for myelopathy, radiculopathy resistant to conservative management (6 months physical therapy, epidural steroid injections) 2. **Ossification of posterior longitudinal ligament (OPLL)**: Laminoplasty for OPLL greater than 60% canal occupancy (direct anterior dural manipulation high-risk for CSF leak, cord injury - Iwasaki 2007) 3. **Posterior ligamentous injury** (facet dislocation, jumped facets): Posterior open reduction and lateral mass screw fixation 4. **Adjacent segment disease post-ACDF**: Extend fusion posteriorly with laminectomy and lateral mass screws (avoids re-exposure of anterior scarred field) ### Trauma 1. **Facet fracture-dislocation**: Posterior open reduction, lateral mass screw fixation C3-C7 2. **Burst fracture with posterior ligamentous injury**: 360° fusion (anterior corpectomy + posterior instrumentation for stability) 3. **Hangman's fracture (C2 pars fracture)**: C2 pars screws or C1-C3 fusion if unstable (greater than 5mm subluxation, disc disruption) ### Tumor/Infection 1. **Metastatic epidural spinal cord compression**: Posterior decompression (laminectomy) + instrumented fusion for structural support 2. **Intradural tumor**: Posterior laminectomy or laminoplasty for tumor resection access ### Deformity 1. **Post-laminectomy kyphosis**: Posterior instrumented fusion (lateral mass screws C3-C6, pedicle screws C7) with lordotic contouring 2. **Ankylosing spondylitis chin-on-chest deformity**: Posterior cervical osteotomy (Smith-Petersen or pedicle subtraction osteotomy at C7-T1) + instrumentation ## Contraindications ### Absolute Contraindications 1. **Active infection** (discitis, osteomyelitis): Treat infection first (6-12 weeks IV antibiotics), defer instrumentation until infection cleared (ESR/CRP normalized) 2. **Unstable fracture requiring anterior column reconstruction**: Isolated posterior instrumentation insufficient for burst fractures with greater than 50% anterior column comminution (requires anterior corpectomy + cage) ### Relative Contraindications 1. **Severe osteoporosis** (T-score less than -3.0): Poor screw purchase (lateral mass bone quality 50-100 HU on CT vs 150-250 HU normal bone), consider cement augmentation or longer construct to distribute load 2. **Prior posterior cervical surgery**: Scar tissue in posterior elements, obliterated tissue planes, increased dural tear risk (5-10% in revision vs 1-2% primary surgery) 3. **Radiation therapy to cervical spine**: Impaired bone healing (fusion rate 70-80% irradiated vs 92-96% non-irradiated - Emery 1994), consider BMP augmentation or longer immobilization (hard collar 12 weeks) 4. **Single-level disease**: Anterior cervical discectomy and fusion (ACDF) preferred for single-level stenosis (shorter recovery, no posterior muscle dissection, 95% fusion rate vs 92% posterior) 60% canal, age <70 years (better ROM preservation benefit)", laminectomyFusion: "Stenosis with KYPHOSIS >10° (fusion corrects deformity), INSTABILITY (facet dislocation, ligamentous injury), age >70 years (ROM less critical)", preferred: "Depends on cervical alignment and instability" } ]} /> ## Preoperative Planning ### Imaging Review 1. **Cervical spine X-rays** (AP, lateral, flexion-extension): Measure C2-C7 sagittal vertical axis (SVA), C2-C7 lordosis (normal 10-20°), assess instability (greater than 3.5mm translation or greater than 11° angulation on flexion-extension) 2. **MRI cervical spine**: Assess spinal cord signal (T2 hyperintensity indicates myelopathy), cord compression levels (Torg ratio less than 0.8 = stenosis), OPLL extent (ossification thickness, canal occupancy percentage) 3. **CT cervical spine**: Evaluate bony anatomy (pedicle dimensions for screw planning, facet joint orientation, ossified ligaments) 4. **CT angiography** (if C2 instrumentation planned): Identify high-riding VA at C2 (10-15% incidence), measure pars width (safe if greater than 5mm), assess VA dominance ### Surgical Planning - **Decompression extent**: Laminoplasty for stenosis greater than or equal to 3 levels with maintained lordosis, laminectomy + fusion for stenosis with kyphosis greater than 10° or instability - **Instrumentation levels**: Lateral mass screws C3-C6, pedicle screws C7, C2 pars screws if C2 instrumentation needed (safer than C2 pedicle screws, 5-8mm pars width vs 3-5mm pedicle) - **Screw trajectory planning**: Preoperative CT measures lateral mass dimensions (10-12mm AP × 12-15mm ML), pedicle dimensions (C7 pedicle 5-7mm transverse diameter, most reliable for pedicle screw) - **Graft planning**: Local bone graft from decompressed lamina/spinous processes (30-40cc available), allograft (cancellous chips or morselized bone) if insufficient local bone, consider BMP if high-risk nonunion (smoking, diabetes, radiation) ## Patient Positioning ### Prone Position with Head Fixation 1. **General anesthesia**: Endotracheal intubation, somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) for spinal cord monitoring 2. **Head fixation**: - **Mayfield 3-pin skull clamp** (gold standard): Pins placed 1-2cm above ears, 1 pin frontal (above eyebrow, avoids supraorbital nerve), 2 pins occipital (avoids transverse sinus, auricular nerve) - **Horseshoe headrest** (alternative if Mayfield unavailable): Foam padding, neutral neck position, avoid pressure on eyes/nose 3. **Prone position**: Patient prone on chest rolls (axillae free to prevent brachial plexus compression), arms tucked at sides or abducted 90° on arm boards 4. **Neck positioning**: NEUTRAL position (avoid flexion which increases epidural venous bleeding, avoid extension which narrows spinal canal and risks cord injury) 5. **Pressure point padding**: Elbows, iliac crests, knees, toes (avoid pressure ulcers) ## Skin Incision and Exposure ### Midline Posterior Approach 1. **Palpation of landmarks**: C2 spinous process (most prominent, starting point), C7 spinous process (vertebra prominens, non-bifid), inion (occipital protuberance) 2. **Skin incision**: Midline incision from C2 to C7 (or extend to occiput if C1-C2 fusion planned), centered on spinous processes 3. **Subcutaneous dissection**: Bovie electrocautery to ligamentum nuchae (midline avascular raphe between left and right trapezius muscles) 4. **Muscle dissection**: - **C3-C7 exposure**: Subperiosteal dissection along spinous processes and laminae STARTING at C3 (preserves C2 muscle attachments), carry dissection LATERALLY to lateral mass (expose lateral mass medial border, leave facet capsule INTACT until instrumentation) - **C2 exposure** (only if C2 instrumentation needed): Detach semispinalis cervicis from inferior C2 spinous process (if unavoidable), undercut C2 lamina from inferior (preserve superior muscle attachments) 5. **Self-retaining retractor placement**: Taylor or Scoville retractors on laminae (maintain subperiosteal plane, avoid excessive lateral retraction which increases bleeding from muscle) ## Laminoplasty Technique (Open-Door Hirabayashi Method) ### Hinge Side Creation (Typically Left Side) 1. **Hinge side laminar trough**: Using high-speed burr, create trough at lamina-lateral mass junction on LEFT side (hinge side), extend from C3 to C6 or C7 - Trough width 3-4mm - Depth to inner cortex ONLY (do NOT violate dura, risk of CSF leak and cord injury) - Leave thin cortical shell (greenstick fracture pattern allows hinge opening without complete laminar detachment) 2. **Confirm inner cortex**: Probe with micro-dissector (should feel thin bone give way, indicating inner cortex reached but dura protected) ### Open Side Osteotomy (Right Side) 1. **Open side laminar cut**: Using high-speed burr, perform COMPLETE osteotomy at lamina-lateral mass junction on RIGHT side (open side), same levels as hinge side (C3-C7) - Cut through BOTH inner and outer cortex (lamina freely mobile after osteotomy) - Protect dura with micro-dissector or Penfield elevator throughout burr work 2. **Ligamentum flavum release**: Sharply divide ligamentum flavum at open side (allows lamina to swing open) ### Lamina Opening and Spacer Placement 1. **Open laminar door**: Using laminar spreaders or Kerrison rongeurs, carefully open lamina from hinge side (swing lamina laterally like a door, hinge side greensticks open) - **Target canal expansion**: 4-5mm opening increases canal diameter from 10-12mm (stenotic) to 14-17mm (normal) 2. **Spacer placement**: Insert bone graft spacer (harvested from spinous process, cut into 5-7mm blocks) OR ceramic/titanium spacers between open side lamina and lateral mass to maintain opening - Secure spacer with microplate and screws (prevents spacer migration) OR suture to lateral mass (non-absorbable suture through drill hole in lateral mass) 3. **Bone graft at hinge**: Place morselized bone graft at hinge site to promote lamina-to-lateral mass fusion over 6-12 months (prevents hinge fracture and canal re-stenosis) ## Laminectomy Technique ### Multilevel Laminectomy (C3-C7) 1. **Spinous process removal**: Rongeur to remove spinous processes at affected levels (C3-C7) 2. **Laminar removal**: - **Kerrison rongeurs**: Begin at inferior edge of C3 lamina, remove lamina in piecemeal fashion (small bites with rongeur, avoid dural tear from excessive force) - **Lateral extent**: Remove lamina to MEDIAL EDGE of facet joint (preserve facet capsule and joint for stability), expose lateral recess and nerve root origin 3. **Ligamentum flavum removal**: Sharply dissect and remove ligamentum flavum (thick, yellow elastic tissue posterior to dura), use micro-dissector to separate ligamentum from dura BEFORE removing 4. **Dural inspection**: After laminectomy, dura should be pulsatile (indicates spinal cord decompression), inspect for CSF leak (clear fluid pooling, requires primary repair with 5-0 Prolene suture) ### Foraminotomy (if Radiculopathy Present) 1. **Identify nerve root**: Use micro-dissector to palpate nerve root exiting foramen (under facet joint) 2. **Facet resection**: High-speed burr to resect MEDIAL 50% of inferior articular process (unroofs nerve root, preserves facet stability) - **Critical limit**: Do NOT resect greater than 50% of facet joint (causes iatrogenic instability, requires fusion) 3. **Decompress root**: Kerrison rongeur to remove compressive disc, osteophyte, or bone at foramen (root should be freely mobile after decompression) ## Lateral Mass Screw Instrumentation (Magerl Technique) ### C3-C6 Lateral Mass Screws 1. **Expose lateral mass**: Subperiosteal dissection to expose lateral mass (10-12mm AP × 12-15mm ML), identify landmarks: - **Medial border**: Junction of lamina and lateral mass (palpable ridge) - **Lateral border**: Facet joint capsule (preserve capsule until ready for screw insertion) - **Superior border**: Superior articular process - **Inferior border**: Inferior articular process 2. **Magerl starting point**: 1mm MEDIAL to lateral mass center (avoids anterolateral corner where VA courses), 1mm SUPERIOR to midpoint of lateral mass (targets thickest bone) 3. **Trajectory**: - **Axial plane**: 25° LATERAL angulation (diverges away from midline, avoids VA at anterolateral corner, maintains 3-5mm safety margin - Heller 1991) - **Sagittal plane**: 25° CEPHALAD angulation (parallels facet joint orientation, avoids exiting nerve root inferiorly) 4. **Drilling**: Use 2.5mm drill bit, drill to depth 12-14mm (bicortical purchase without anterior cortex perforation), SHOULD FEEL BONE throughout drilling (sudden loss of resistance indicates cortical perforation, potential VA injury - ABORT) 5. **Tapping**: Tap hole with 3.5mm tap (cortical bone requires tapping for screw insertion) 6. **Screw insertion**: Insert 3.5mm × 14-16mm cortical screw (bicortical purchase), torque to 4-6 Nm (avoid overtightening which strips bone) ### C7 Pedicle Screw (Alternative to Lateral Mass) 1. **C7 pedicle entry point**: 1mm LATERAL to center of lateral mass, at junction of lamina and lateral mass 2. **Trajectory**: - **Axial plane**: 25-30° MEDIAL angulation (converges toward vertebral body center) - **Sagittal plane**: 5-10° CAUDAD angulation (follows pedicle axis toward vertebral body) 3. **Drilling**: 2.5-3.0mm drill bit, depth 25-30mm (enters vertebral body, bicortical purchase at anterior vertebral body cortex) 4. **Screw insertion**: 3.5-4.5mm × 28-32mm pedicle screw (longer than lateral mass screw due to pedicle length + vertebral body depth) ### Rod Contouring and Fixation 1. **Rod contouring**: Contour 3.5mm titanium rod to match cervical lordosis (10-20° at C3-C7) 2. **Rod placement**: Secure rod to screw heads with set screws, tighten to 6-8 Nm torque 3. **Compression/distraction**: Apply compression across levels if deformity correction needed (closes facet joints, promotes fusion) ## Fusion Bed Preparation and Bone Grafting 1. **Facet fusion**: Decorticate facet joints at instrumented levels with high-speed burr (expose bleeding bone), pack morselized bone graft into facet joints (promotes posterolateral fusion) 2. **Lateral mass fusion**: Decorticate lateral mass surfaces, place bone graft over lateral masses (creates posterolateral fusion bed) 3. **Graft options**: - **Autograft**: Local bone from spinous processes/lamina (30-40cc available from multilevel laminectomy) - **Allograft**: Cancellous chips (if insufficient local bone) - **BMP**: rhBMP-2 2-4mg on collagen sponge (off-label use in cervical spine, increases fusion rate from 78% to 92% in high-risk patients - smokers, diabetics - Vaccaro 2008) ## Closure 1. **Hemostasis**: Achieve meticulous hemostasis (bipolar electrocautery to muscle edges, hemostatic agents - Surgicel, thrombin-soaked gelfoam - to epidural venous plexus) 2. **Drain placement**: Closed suction drain in subfascial space (prevents hematoma, remove when output less than 30mL/day, typically postoperative day 1-2) 3. **Muscle closure**: Re-approximate muscle to midline ligamentum nuchae raphe with absorbable suture (0-Vicryl) 4. **Fascial closure**: Close fascia with absorbable suture (0-Vicryl running stitch) 5. **Skin closure**: Subcuticular 3-0 Monocryl OR staples (remove at 10-14 days) ## Postoperative Protocol 1. **Immobilization**: Hard cervical collar for 6-12 weeks (laminectomy + fusion), no collar needed for laminoplasty (posterior elements preserved, intrinsically stable) 2. **Mobilization**: Ambulate postoperative day 1, no lifting greater than 5kg for 12 weeks (promotes fusion, reduces hardware stress) 3. **Neurological monitoring**: Assess motor strength (deltoid, biceps, triceps, hand intrinsics), sensation (C5-T1 dermatomes), bowel/bladder function daily until discharge 4. **DVT prophylaxis**: LMWH (enoxaparin 40mg daily) OR pneumatic compression devices, mobilize early (reduces VTE risk from 2-3% to 0.5-1% - Glotzbecker 2010) 5. **Radiographic follow-up**: X-rays at 6 weeks, 3 months, 6 months, 12 months (assess fusion, hardware position, maintenance of cervical lordosis) ## Neurological Complications ### C5 Nerve Root Palsy (4.6-11% Incidence) - **Presentation**: Deltoid/biceps weakness (MRC 2-3/5), preserved hand function, onset 1-7 days postoperatively, may have anterolateral shoulder pain - **Mechanism**: Posterior cord shift (3-5mm) after decompression tethers SHORT C5 root (11mm from cord to foramen, SHORTEST cervical root - Sakaura 2003), causes stretch injury OR ischemia from radicular artery disruption during foraminotomy - **Natural history**: 70% improve to MRC 4/5 by 6-12 months, 30% plateau at MRC 3/5 (PERMANENT weakness, functionally significant - cannot lift arm above shoulder) - **Management**: - **Conservative**: Physical therapy (deltoid/biceps strengthening with isometric then progressive resistance exercises), reassurance (emphasize 70% recovery rate, plateau at 12 months) - **EMG/NCS at 3 weeks**: Establish baseline (differentiate neuropraxia from axonotmesis), repeat at 6 months if no recovery - **NO surgical re-exploration indicated**: Decompression does not reverse tethering injury, foraminotomy does NOT improve recovery (retrospective series show NO benefit from revision surgery - Sakaura 2003) ### Spinal Cord Injury (0.2-0.5% Incidence) - **Presentation**: Immediate postoperative quadriparesis/quadriplegia, sensory level at injury site, bowel/bladder dysfunction - **Mechanism**: Direct cord trauma during laminectomy (Kerrison rongeur injury, burr injury), dural tear with cord herniation through defect, hematoma compression, or intraoperative hypotension causing cord ischemia - **Management**: - **Immediate recognition**: Intraoperative MEP/SSEP monitoring detects cord injury in real-time (50% decrease in MEP amplitude indicates cord compromise - Nuwer 1995), prompt reversal of offending maneuver (reduce retraction, evacuate hematoma, maintain mean arterial pressure greater than 85mmHg) - **Postoperative imaging**: Emergent MRI cervical spine (identify hematoma, cord contusion, instrumentation malposition) - **High-dose methylprednisolone NO LONGER RECOMMENDED**: NASCI S II protocol (30mg/kg bolus, then 5.4mg/kg/hr × 23-48 hours) has NO proven benefit and 2.6× infection risk (Hurlbert 2013, guidelines recommend AGAINST use) - **Surgical evacuation**: If hematoma present (greater than 50% canal compromise), emergent re-exploration for clot evacuation within 24 hours (time-sensitive, neurological recovery correlates with early decompression) ### Recurrent Laryngeal Nerve Palsy (Rare, 0.1-0.2%) - **Mechanism**: Prone positioning with neck hyperextension causes excessive traction on recurrent laryngeal nerve (courses anteriorly in tracheoesophageal groove) - **Presentation**: Hoarseness, aspiration, dysphagia (unilateral vocal cord paralysis) - **Management**: Laryngoscopy (confirm vocal cord paralysis), speech therapy (swallow rehabilitation), consider medialization thyroplasty if no recovery by 6-12 months ## Hardware Complications ### Vertebral Artery Injury (0.2-0.5% Lateral Mass Screws, 2-5% C2 Pedicle Screws) - **Intraoperative recognition**: Sudden arterial/venous bleeding from screw hole (pulsatile if arterial, continuous if venous), hypotension if significant blood loss - **Immediate management**: 1. **Tamponade**: Immediately insert screw into hole (occludes VA laceration), pack bone wax around screw 2. **Leave screw in place**: DO NOT remove screw intraoperatively (screw tamponades injury, removal causes uncontrolled hemorrhage) 3. **Hemodynamic support**: Fluid resuscitation, blood transfusion if indicated 4. **Vascular surgery consultation**: Intraoperative or immediate postoperative consultation - **Postoperative imaging**: CT angiography within 24 hours (assess VA patency, pseudoaneurysm formation) - **Definitive management**: - **Unilateral VA injury with contralateral patent VA**: Consider observation (VA injury may thrombose spontaneously, monitor with serial CTAs at 1 week, 1 month, 3 months) OR endovascular coiling (preferred if pseudoaneurysm present, risk of delayed rupture) - **Unilateral VA injury with contralateral atretic/hypoplastic VA**: URGENT endovascular VA stenting or open VA repair (preserve ipsilateral VA flow to prevent brainstem/cerebellar infarction, 30-50% risk if sole VA occluded) - **Bilateral VA injury**: CATASTROPHIC complication, emergent bilateral endovascular stenting/coiling, high risk of brainstem infarction (50-70% mortality - Smith 2008) ### Screw Loosening/Pull-Out (3-5% Incidence) - **Risk factors**: Osteoporosis (T-score less than -2.5), smoking (impaired fusion), inadequate screw length (less than 14mm, unicortical purchase), pseudarthrosis - **Presentation**: Recurrent neck pain, clicking/clunking with neck motion, X-rays show radiolucent halo greater than 2mm around screw (indicates loosening) - **Management**: - **Asymptomatic loosening with solid fusion**: Observation (hardware not load-bearing once fusion solid) - **Symptomatic loosening with pseudarthrosis**: Revision surgery (remove loose hardware, extend fusion, consider longer construct or cement augmentation if osteoporotic) ### Hardware Prominence/Impingement (5-10% Incidence) - **Presentation**: Axial neck pain at specific level, palpable hardware prominence under skin, pain with neck extension (hardware impinges on overlying muscle/fascia) - **Management**: - **Conservative**: NSAIDs, activity modification, consider removal after fusion solid (12 months postoperatively, X-rays/CT confirm bridging bone) - **Surgical**: Hardware removal if symptomatic and fusion confirmed (relieves impingement pain in 80-90%) ## Fusion-Related Complications ### Pseudarthrosis (4-8% Incidence) - **Risk factors**: Smoking (3× risk, impairs osteoblast function), diabetes (2× risk, impaired healing), multilevel fusion (greater than or equal to 4 levels, 8-12% pseudarthrosis vs 4-5% single level), inadequate immobilization (non-compliance with collar) - **Presentation**: Persistent neck pain at 6-12 months postoperatively, pain with flexion-extension, X-rays show motion greater than 2mm on flexion-extension views or no bridging bone on CT at 12 months - **Diagnosis**: - **Flexion-extension X-rays**: Motion greater than 2mm or angulation greater than 5° at instrumented level indicates pseudarthrosis - **CT cervical spine**: Grade fusion (Grade 1 = no bridging bone, Grade 2 = partial bridging, Grade 3 = solid bridging on 50% or more of fusion bed) - **Management**: - **Asymptomatic pseudarthrosis**: Observation (some patients tolerate stable fibrous union without pain) - **Symptomatic pseudarthrosis**: Revision fusion (anterior approach - ACDF to supplement posterior fusion, OR revision posterior fusion with BMP augmentation, extended immobilization 12 weeks hard collar) ### Adjacent Segment Disease (25-30% at 10 Years) - **Mechanism**: Increased stress on adjacent segments (rigid fusion shifts motion to adjacent levels, causes accelerated disc degeneration, facet arthritis) - **Presentation**: New neck pain, radiculopathy, or myelopathy at level ABOVE or BELOW previous fusion, MRI shows new disc herniation or stenosis at adjacent level - **Management**: - **Conservative**: Physical therapy, epidural steroid injections (40-50% respond, avoid surgery) - **Surgical**: Extend fusion to adjacent symptomatic level (ACDF or posterior extension of construct) ## Wound Complications ### Infection (Superficial 2-3%, Deep 0.5-1%) - **Superficial wound infection**: Erythema, drainage, fever within 2 weeks postoperatively, NO hardware involvement - **Management**: Wound washout, oral antibiotics (cephalexin 500mg four times daily × 10 days OR clindamycin 300mg three times daily if MRSA suspected), culture-directed therapy - **Deep infection** (involves hardware, posterior elements): Persistent neck pain, fever, elevated CRP/ESR (weeks to months postoperatively), wound drainage (purulent or serous) - **Diagnosis**: MRI cervical spine (T2 hyperintensity in posterior soft tissues, epidural abscess), CT-guided biopsy for culture - **Management**: - **Hardware RETENTION if fusion not solid**: Debridement and washout (remove all necrotic tissue, copious irrigation), culture-specific IV antibiotics 6-12 weeks (cefazolin 2g every 8 hours OR vancomycin 15mg/kg every 12 hours if MRSA, culture-directed), maintain hardware if fusion not yet solid (hardware provides stability, biofilm formation controlled with prolonged antibiotics) - **Hardware REMOVAL if fusion solid**: Remove hardware (eliminates biofilm nidus), debridement, culture-specific IV antibiotics 6 weeks ### CSF Leak/Pseudomeningocele (1-3% Incidence) - **Mechanism**: Dural tear during laminectomy (Kerrison rongeur injury, adhesions from prior surgery, OPLL with dural ossification), creates CSF fistula - **Presentation**: Clear wound drainage (CSF), positional headache (worse upright, improves supine), palpable fluctuant neck mass (pseudomeningocele) - **Diagnosis**: Fluid beta-2 transferrin assay (confirms CSF), MRI cervical spine (identifies dural defect, size of pseudomeningocele) - **Management**: - **Small leak** (less than 5mm dural defect): Conservative management (bed rest flat × 48-72 hours, pressure dressing, acetazolamide 250mg twice daily to reduce CSF production), 60-70% heal spontaneously - **Large leak** (greater than 5mm defect, persistent drainage greater than 7 days): Surgical repair (re-exploration, primary dural repair with 5-0 Prolene suture, dural sealant - DuraSeal, fat graft overlay), lumbar drain (10mL/hr CSF drainage × 3-5 days reduces pressure, promotes healing) ## Deformity-Related Complications ### Post-Laminectomy Kyphosis (5-10% Laminoplasty, 50-60% Laminectomy Without Fusion) - **Mechanism**: Loss of posterior tension band (laminectomy removes posterior ligaments, allows progressive kyphotic deformity over months-years), exacerbated by preoperative kyphosis or pediatric laminectomy (growing spine deforms more readily) - **Presentation**: Progressive neck pain, inability to extend neck, chin-on-chest deformity (swan-neck deformity in severe cases), myelopathy from cord stretch over kyphotic apex - **Prevention**: - **Laminoplasty over laminectomy**: Preserves posterior tension band (lamina hinged, not removed), reduces kyphosis from 50% to 5-10% (Ratliff 1993) - **Prophylactic fusion**: If laminectomy performed in patient with preoperative kyphosis (greater than 10°), neutral sagittal balance, or ligamentous laxity, perform fusion + instrumentation (prevents progressive deformity) - **Management**: - **Mild kyphosis** (10-20°, no myelopathy): Observation, collar support, physical therapy for neck extensor strengthening - **Severe kyphosis** (greater than 20°, myelopathy, chin-on-chest): Revision surgery with posterior instrumented fusion + lordotic contouring (may require anterior column release - corpectomy - if rigid deformity, then posterior fusion for correction) 10° (requires correction), instability (facet dislocation, ligamentous injury), age >70 years (ROM less critical)", "C2 muscle preservation reduces axial pain from 60% to 25% (Hosono 1996) - should be routine in all posterior cervical surgeries" ]} commonMistakes={[ "❌ Offering laminectomy WITHOUT fusion for multilevel stenosis - 50-60% develop kyphotic deformity (loss of posterior tension band causes progressive kyphosis - Ratliff 1993)", "❌ Recommending laminoplasty for patient with preoperative kyphosis >10° - laminoplasty does NOT correct deformity (only prevents progression), patient needs fusion with lordotic correction", "❌ Not discussing C5 palsy risk preoperatively - 4.6-11% incidence is PREDICTABLE, patient must understand 30% risk of PERMANENT shoulder weakness", "❌ Assuming laminoplasty has NO axial pain - 60% axial pain if C2 detached (traditional technique), but 15-25% with C2 preservation (modern technique - Hosono 1996)", "❌ Recommending fusion for ALL multilevel stenosis - motion preservation benefit is SIGNIFICANT (50% reduction in adjacent segment disease at 10 years), laminoplasty preferred if lordosis maintained and no instability" ]} followUpQuestions={[ "What are the biomechanical differences between laminoplasty and laminectomy in terms of posterior tension band? (Answer: Laminoplasty hinges lamina open, maintains ligamentum flavum/interspinous ligaments on hinge side, preserves 50-60% of posterior column load-bearing; laminectomy removes lamina entirely, eliminates posterior tension band, causes 50-60% kyphotic deformity without fusion - Ratliff 1993)", "How does adjacent segment disease incidence compare between laminoplasty and fusion? (Answer: Laminoplasty 10-15% at 10 years (motion preserved, reduces adjacent stress) vs fusion 25-30% at 10 years (rigid construct increases adjacent segment stress - Hilibrand 1999), 50% relative risk reduction with motion preservation)", "What patient factors would make you choose fusion over laminoplasty? (Answer: Preoperative kyphosis >10° - fusion corrects deformity; instability - facet dislocation, ligamentous injury; age >70 years - ROM less critical, fusion's lower C5 palsy risk preferred; patient risk-aversion - cannot tolerate 7-8% shoulder weakness risk)", "What is the mechanism of lamina fracture during laminoplasty? (Answer: Hinge side incomplete osteotomy creates greenstick fracture pattern (thin cortical shell), 15-20% of hinges fracture completely during lamina opening, higher risk in OPLL (ossified lamina less flexible), usually asymptomatic but may cause re-stenosis if complete fracture displaces lamina)" ]} /> 60% canal occupancy (larger decompression canal expansion causes greater posterior cord shift, OR 3.2 - Sakaura 2003)" }, ]} />