Posterior Spinal Fusion and Instrumentation for Adolescent Idiopathic Scoliosis (PSF)

Indications

Absolute Indications

• Adolescent idiopathic scoliosis with Cobb angle >45-50 degrees (surgical threshold per SRS guidelines)
• Progressive curves despite orthotic management (>5 degrees documented progression over 6 months)
• Skeletally mature patients (Risser 4-5) with curves >40 degrees and unacceptable deformity/trunk imbalance
• Thoracic curves >50 degrees (high risk of progression in adulthood - natural history studies show 1° per year)
• Symptomatic curves causing pain, respiratory compromise (rare in AIS), or psychosocial distress

Relative Indications

• Thoracolumbar or lumbar curves >40-45 degrees with coronal imbalance (C7 plumb line >2cm from CSVL)
• Double major curves with both thoracic and lumbar components >40 degrees
• Curves 40-50 degrees in growing patients (Risser 0-3) with documented progression despite bracing
• Curves with significant sagittal plane deformity (thoracic hypokyphosis or hyperkyphosis >50 degrees)

Contraindications

Absolute Contraindications

• Active spinal infection (osteomyelitis, discitis, epidural abscess) - treat infection first
• Uncontrolled medical comorbidities (severe cardiac/pulmonary disease preventing safe anesthesia)
• Patient/family refusal after informed consent discussion of risks/benefits
• Bleeding diathesis uncorrectable with medical management (severe hemophilia, platelet disorders)

Relative Contraindications

• Severe osteopenia/osteoporosis (bone mineral density Z-score <-2.5) - poor screw purchase, consider cement augmentation
• Malnutrition (albumin <3.5 g/dL, BMI <18.5) - optimize nutrition preoperatively for wound healing and fusion
• Obesity (BMI >35) - increased infection risk, wound complications, technical difficulty
• Psychiatric instability or unrealistic expectations - requires preoperative counseling and optimization
• Age <10 years with open triradiate cartilage (crankshaft phenomenon risk) - consider anterior fusion or growth-friendly constructs
• Neuromuscular etiology scoliosis (not true AIS) - different surgical considerations, higher complication rates

Clinical Assessment

History

• Age at curve detection, progression rate, bracing compliance and effectiveness
• Pain (uncommon in true AIS - if present, investigate for underlying pathology like syrinx, tumor)
• Neurological symptoms (weakness, numbness, bowel/bladder dysfunction) - red flags requiring MRI
• Respiratory symptoms (dyspnea, exercise intolerance) - obtain PFTs if curve >70 degrees
• Family history (AIS has genetic component - 30% have affected family member)
• Psychosocial impact (body image concerns, clothing fit, participation restrictions)

Physical Examination

• Standing alignment: coronal balance (C7 plumb line to CSVL), sagittal balance (C7 plumb line to posterior S1)
• Curve magnitude and flexibility: forward bend test (Adams test) - rib hump indicates structural component
• Shoulder height asymmetry, scapular prominence, waist crease asymmetry, pelvic obliquity
• Spine flexibility: side bending to assess curve correctability
• Thorough neurological exam (motor 5/5 all groups, sensation intact, reflexes symmetric, abdominal reflexes present)
• Lower extremity length discrepancy (LLD >2cm can cause pelvic obliquity and compensatory scoliosis)
• Skin examination (café-au-lait spots suggest neurofibromatosis, midline hairy patch/dimple suggests intraspinal pathology)
• Cardiac exam if concern for Marfan syndrome (tall stature, arachnodactyly, pectus, joint laxity)

Imaging Studies

• Standing PA and Lateral Radiographs (36-inch cassette, full spine): Measure Cobb angles, identify curve apex and end vertebrae, assess coronal and sagittal balance, Risser sign (skeletal maturity), disc health
• Supine Bending Films (right and left side bending, or traction films): Assess curve flexibility and correctability. Structural curves correct <25 degrees, flexible curves >25 degrees. Determines which curves need fusion
• MRI Brain and Total Spine (MANDATORY in all presumed AIS before surgery): Rule out Chiari malformation (20% incidence in AIS), syringomyelia, tethered cord, intraspinal tumors. MRI abnormalities found in 5-10% of presumed AIS cases
• CT Scan with 3D Reconstruction (if complex anatomy, revision, congenital vertebral anomalies): Assess pedicle size and morphology, bone quality, plan screw trajectories
• Pulmonary Function Tests (if Cobb >70 degrees or symptoms): FVC and FEV1 reduced by 0.6% per degree of curve >50 degrees. Severe restriction (FVC <40% predicted) increases perioperative respiratory complications

Lenke Classification System

• Curve Type (1-6): Based on which curves are structural (Cobb >25 degrees AND <25 degrees correction on bending)
  • Type 1: Main thoracic (MT) only structural - fuse thoracic curve only
  • Type 2: Double thoracic (PT and MT both structural) - fuse both upper and main thoracic
  • Type 3: Double major (MT and TL/L both structural) - fuse thoracic and lumbar
  • Type 4: Triple major (PT, MT, TL/L all structural) - fuse all three curves
  • Type 5: Thoracolumbar/lumbar (TL/L) only structural - fuse lumbar only
  • Type 6: Thoracolumbar/lumbar-main thoracic (TL/L primary, MT structural) - fuse both
• Lumbar Modifier (A/B/C): Based on position of lumbar curve apex relative to CSVL (center sacral vertical line)
  • A: Apex between pedicles and CSVL (does not cross) - lumbar fusion usually not needed
  • B: Apex touches CSVL or between CSVL and medial border vertebral body - consider lumbar fusion
  • C: Apex crosses CSVL medially - lumbar fusion typically required
• Sagittal Modifier (-/N/+): Based on T5-T12 sagittal Cobb angle
  • (-) Hypokyphosis: <10 degrees - restore kyphosis during surgery
  • (N) Normal: 10-40 degrees - maintain kyphosis
  • (+) Hyperkyphosis: >40 degrees - may need less aggressive derotation to preserve kyphosis

Fusion Level Selection

• UIV (Upper Instrumented Vertebra): Upper end vertebra of main structural curve OR proximal stable vertebra (typically T2-T4 for main thoracic curves). Stopping too low risks proximal junctional kyphosis
• LIV (Lowest Instrumented Vertebra): Stable vertebra (bisected by CSVL on coronal film) OR neutral vertebra (most closely bisected by CSVL). Considerations: Lenke modifier, disc wedging below LIV, lumbar flexibility. Stopping too short risks adding-on deformity. Stopping too long sacrifices lumbar motion

Laboratory Studies

• Complete blood count (baseline hemoglobin/hematocrit - may need transfusion, target Hgb >11 g/dL preop)
• Coagulation studies (PT/PTT/INR) if bleeding history or anticoagulation
• Type and cross-match 4-6 units PRBCs (anticipate 30-50% transfusion rate, reduced with cell saver and TXA)
• Nutritional markers if concern (albumin, prealbumin, vitamin D, calcium) - optimize to albumin >3.5 g/dL
• Pregnancy test in females of childbearing age (teratogenic radiation exposure, anesthetic considerations)

Preoperative Optimization

• Nutritional supplementation if deficient (vitamin D >30 ng/mL, calcium 1200-1500 mg/day for bone health)
• Iron supplementation if anemic (ferrous sulfate 325mg TID for 4-6 weeks preop, erythropoietin in severe cases)
• Smoking cessation (increases pseudarthrosis risk 2-4 fold) - minimum 4 weeks before surgery
• Weight optimization (BMI 18.5-30 ideal range) - obesity increases infection 3-fold
• Psychiatric optimization if anxiety/depression (common in adolescents with body image concerns)
• Autologous blood donation (controversial, limited utility with modern blood conservation techniques)
• Bowel prep evening before surgery (some surgeons, controversial) - reduces ileus risk

Informed Consent Discussion

• Risks: Neurological injury (0.5-1%, permanent paralysis 0.1-0.5%), infection (3-5%), blood loss requiring transfusion (30-50%), pseudarthrosis (2-5%), proximal junctional kyphosis (10-30%), implant failure (1-2%), chronic pain (5-10%)
• Benefits: Curve correction (50-70% typical), halt progression, improved cosmesis and self-image, high satisfaction (80-90%)
• Alternatives: Observation (if mild curve <40 degrees), bracing (if immature and curve <40-45 degrees), anterior approach (rarely indicated in AIS)
• Expected outcomes: Fusion permanent (loss of motion at fused segments), return to activities 6-12 months, long hospital stay (3-5 days), prolonged recovery (3-6 months to full activities)

Patient Positioning and Setup

Anesthesia Considerations

• General endotracheal anesthesia with large-bore IV access (16-18G x2) and arterial line for blood pressure monitoring
• AVOID neuromuscular blockade after intubation (interferes with neuromonitoring - MEPs unobtainable)
• AVOID volatile anesthetics >1 MAC if possible (suppress MEP amplitudes) - prefer total intravenous anesthesia (TIVA with propofol and remifentanil)
• Maintain mean arterial pressure >65-70 mmHg (spinal cord perfusion pressure critical during correction)
• Tranexamic acid (TXA) for blood conservation: loading dose 10-15 mg/kg IV over 15-20 minutes, then infusion 1 mg/kg/hr until closure (reduces blood loss 30-50%)
• Normothermia critical (core temperature >36°C) - forced air warming, fluid warmers (hypothermia increases blood loss and infection)

Neuromonitoring Setup

• MANDATORY for all scoliosis correction procedures
• Somatosensory evoked potentials (SSEPs): assess sensory pathways (posterior columns) - median and tibial nerve stimulation, cortical recording
• Motor evoked potentials (MEPs): assess motor pathways (corticospinal tract, anterior horn cells) - transcranial stimulation, record from lower extremity muscles (abductor hallucis, tibialis anterior, abductor digiti minimi)
• Spontaneous and triggered electromyography (EMG): assess nerve root integrity during pedicle screw placement, threshold >8-10 mA safe
• Baseline recordings before positioning, verify signals stable after positioning
• Alarm criteria: SSEP >50% amplitude decrease or >10% latency increase; MEP >50-75% amplitude decrease (some centers use stricter 50% threshold)

Positioning Technique

• Patient PRONE on Jackson table (radiolucent with adjustable chest and pelvic supports) or Wilson frame
• CRITICAL: Abdomen free-hanging (chest rolls positioned from clavicle to iliac crest laterally, leave central abdomen without support) - decompresses IVC and epidural veins, reduces blood loss 30-50%
• Head positioning: Mayfield 3-pin fixation (if long fusion to upper thoracic, allows secure head positioning for 4+ hour case) OR prone head positioner with cushioned horseshoe (pad forehead, avoid pressure on eyes)
• Eyes taped closed, eye shields or protective goggles, avoid any pressure on globes (risk: retinal artery occlusion and blindness)
• Arms positioned: 90 degrees abduction or less on padded armboards, elbows padded, palms up or neutral (>90 degrees abduction risks brachial plexus stretch injury)
• Hip flexion 10-20 degrees (reduces lumbar lordosis, facilitates exposure, relaxes psoas)
• Pad ALL pressure points: eyes, nose, chin, breasts (females - ensure hanging free), genitalia (males - ensure not compressed), anterior superior iliac spines, knees (foam under shins), feet (toes not compressed)
• Confirm NEUROMONITORING signals after positioning (ensure no position-related signal changes from brachial plexus stretch or spinal cord compression)
• Prep and drape widely: occiput to sacrum, laterally to bilateral posterior axillary lines

Surgical Approach and Exposure

Incision and Superficial Dissection

• Palpate and mark spinous processes from 2 levels above planned UIV to 2 levels below planned LIV (allows flexibility for level verification and adjustment)
• MIDLINE POSTERIOR incision through skin and subcutaneous tissue - typically 30-50 cm depending on curve extent (e.g., T2-L4 fusion requires incision approximately T1-L5)
• Cauterize or ligate perforating vessels in subcutaneous tissue
• Identify lumbodorsal (thoracolumbar) fascia - thick fascial layer overlying paraspinal muscles

Subperiosteal Muscle Dissection

• Incise lumbodorsal fascia in midline over spinous processes
• SUBPERIOSTEAL DISSECTION critical (preserves muscle blood supply, minimizes bleeding): Use Cobb elevator to elevate paraspinal muscles (erector spinae - spinalis, longissimus, iliocostalis) off posterior elements
• Expose spinous processes, laminae, facet joints, and TRANSVERSE PROCESSES bilaterally (TP tips identify pedicle anatomy)
• Dissect laterally to transverse process tips but NO FURTHER (risk: pleural violation in thoracic spine if dissect lateral to TP)
• Self-retaining retractors placed (Darrach, McCullough, or similar) - deep blade on transverse processes, superficial blade on muscle
• Achieve meticulous HEMOSTASIS: electrocautery for muscle bleeding, bone wax for bleeding cancellous bone (use sparingly on fusion surfaces - inhibits fusion)

Level Localization

• CRITICAL STEP: Verify levels with intraoperative imaging BEFORE screw placement
• Fluoroscopy technique: Identify C7 (most prominent cervical spinous process at cervicothoracic junction) OR count ribs (T12 has last rib, T11 has 11th rib, etc.) OR palpate iliac crest (L4-L5 level)
• Count vertebrae from known landmark and mark levels with marker or needles under fluoroscopy
• AP and lateral fluoroscopy confirm correct levels - common error is counting mistake (transitional vertebrae, lumbarization of S1, sacralization of L5)
• Mark planned UIV and LIV with skin marker or needles for reference

Pedicle Screw Instrumentation

Thoracic Pedicle Screw Placement (T1-T12)

• Thoracic pedicles SMALL (diameter 4-6 mm at T4-T8, gradually increase to 8-10 mm at T11-T12) - requires precise technique
• Entry Point Identification: Intersection of VERTICAL line along lateral border of superior articular facet and HORIZONTAL line bisecting transverse process (lateral-superior quadrant of facet). Alternative description: 2mm lateral and 2mm inferior to center of facet joint
• Decorticate entry point with high-speed burr (create shallow divot in cortical bone to prevent pedicle probe from skiving) OR sharp pedicle awl
• Trajectory - Gear Shift Technique: Insert pedicle probe (3.0-3.5mm diameter) with slight lateral start (engage lateral pedicle wall), then redirect medially 10-15 degrees MEDIAL CONVERGENCE in axial plane (converging toward midline/spinal canal). Parallel to SUPERIOR ENDPLATE in sagittal plane (slight caudal angulation acceptable but avoid excessive cephalad angulation - risks superior endplate breach)
• Depth: 30-35 mm typical for mid-thoracic (aim for 80% vertebral body width - measure on preoperative CT or estimate 70-80% depth on lateral fluoroscopy). AVOID anterior cortex perforation
• Four-Wall Palpation MANDATORY: After probe placement, use ball-tip pedicle sound to palpate all four walls of pedicle tract (medial, lateral, superior, inferior). Should feel intact cortical bone 360 degrees. Medial wall breach MOST DANGEROUS (spinal cord), lateral breach risks pleura/vessels, inferior breach risks nerve root
• Triggered EMG Verification: Stimulate pedicle tract with triggered EMG probe. Threshold >8-10 mA indicates >2 mm distance from nerve root (safe). Threshold <5 mA indicates breach or nerve proximity (reposition)
• Tap pedicle tract (3.5-4.5 mm tap for 4.5-5.5 mm screw)
• Insert POLYAXIAL pedicle screw (allows 30-40 degrees of angulation for rod insertion) - hand tighten provisionally, do not fully tighten set screws yet
• Screw diameter: 4.5-5.5 mm typical for mid-thoracic, 5.5-6.5 mm for lower thoracic (T10-T12)
• Verify screw position: AP fluoroscopy (screw should converge medially, pedicle walls intact), lateral fluoroscopy (screw parallel to endplate, no anterior breach, 70-80% depth)
• Repeat for all instrumented thoracic levels bilaterally

Lumbar Pedicle Screw Placement (L1-L5)

• Lumbar pedicles LARGER (diameter 8-12 mm L1-L4, up to 15 mm at L5) - easier to cannulate than thoracic
• Entry Point: More LATERAL than thoracic - junction of lateral border of superior articular facet and superior border of transverse process (mamillary process region). Alternative: intersection of vertical line through lateral facet and horizontal line through superior TP border
• Trajectory - Gear Shift Technique: Start trajectory 30-45 degrees LATERAL (engage lateral pedicle wall), then redirect to 10-15 degrees MEDIAL convergence (creates J-shaped trajectory maximizing pedicle bone purchase and strength)
• Parallel to superior endplate in sagittal plane (avoid caudal angulation - risks inferior nerve root)
• Depth: 40-50 mm (80% vertebral body width). L5 depth may be 50-55 mm. Avoid bicortical purchase in lumbar spine (anterior vascular structures)
• Four-wall palpation (medial wall breach risks cauda equina/nerve roots, anterior breach risks great vessels)
• Triggered EMG threshold >8-10 mA safe (L5 nerve root crosses L5 pedicle anterolaterally - most at risk)
• Screw diameter: 6.5-7.5 mm typical lumbar (larger diameter improves pullout strength)
• Verify position on AP and lateral fluoroscopy

Sacral Screw Placement (S1 if fusion to sacrum)

• Entry point: 1-2 mm lateral to S1 foramen at junction of superior articular process and sacral ala
• Trajectory: 25-30 degrees lateral-to-medial (more lateral than lumbar), 25-30 degrees caudal (aim toward S1 promontory)
• Depth: 60-80 mm (long screws into sacral promontory provide best fixation). May use bicortical purchase (sacral screw penetrates anterior cortex safely - no vascular structures)
• S2 alar-iliac screws: alternative technique for lumbosacral fixation - start at S2 foramen, trajectory lateral into ilium (very strong fixation, used in neuromuscular scoliosis or long constructs to sacrum)

Deformity Correction Technique

Facet Decortication and Fusion Bed Preparation

• After all pedicle screws placed and verified, prepare fusion bed
• Remove facet joint CARTILAGE completely using osteotome or high-speed burr (facetectomy) - cartilage inhibits fusion
• Decorticate ALL posterior elements at instrumented levels: laminae (rough up with burr or osteotome), facets (remove cartilage), transverse processes (roughen with burr)
• Goal: expose bleeding cancellous bone (pink punctate bleeding indicates viable bone bed)
• Collect LOCAL AUTOGRAFT (spinous process bone, laminar bone, facet bone) in separate container - SAVE for grafting later
• Create large surface area for fusion (increases fusion success rate)
• If decompression needed (rare in AIS, more common in congenital or neuromuscular scoliosis): Laminectomy using Kerrison rongeurs (angle away from dura), remove ligamentum flavum carefully

Rod Contouring

• Measure rod length from UIV to LIV using measuring device or template rod
• Select rod diameter: 5.5 mm or 6.35 mm (most common in adolescent AIS). Cobalt-chrome rods (stiffer, better correction maintenance but more stress shielding) vs titanium rods (less stiff, less stress shielding but higher rod fracture risk if pseudarthrosis)
• ROD CONTOURING determines final sagittal alignment - CRITICAL for long-term outcomes
• Contour rods to DESIRED sagittal profile using French rod benders:
  • Thoracic kyphosis (T5-T12): 20-40 degrees (restore physiologic kyphosis - flat-back syndrome if inadequate)
  • Lumbar lordosis (L1-S1): 40-60 degrees (should approximate pelvic incidence ± 10 degrees for sagittal balance)
• Create SMOOTH curves (avoid sharp bends - create stress risers and rod fracture risk)
• May reference preoperative lateral radiographs or normal contralateral curve for template
• Contour BOTH rods similarly (slight differences acceptable but major asymmetry creates imbalance)

Rod Insertion

• Insert CONCAVE ROD first (easier to insert, spans shorter distance, less corrective force initially)
• Slide rod through tulip heads of pedicle screws from caudad to cephalad (or cephalad to caudad - surgeon preference)
• Provisionally lock 2-3 screws at UIV and LIV (anchor points) - do not fully tighten
• May need gentle rotation of rod to seat fully into all screw tulips (use rod holder or rod persuader)
• Insert CONVEX ROD second (more difficult, spans greater distance due to deformity, requires more reduction force)
• Use rod reducers or persuaders to bring rod down into screw tulips (apply gentle progressive force - avoid excessive force that can pull screws out or fracture pedicles)
• Verify both rods seated in all screw tulips - should be fully seated in base of tulip before tightening

Coronal Correction - Compression and Distraction

• Coronal deformity correction techniques (multiple strategies, often combined):
  1. Concave Compression: Compress segments on concave side of curve (shorten concave side, brings vertebrae toward midline) - apply at apex of concavity
  2. Convex Distraction: Distract segments on convex side (lengthen convex side) - apply carefully, limit to <50% correction in single maneuver
  3. Segmental Translation: Translate apical vertebrae toward midline using reduction screws
• Apply corrective forces GRADUALLY and INCREMENTALLY (avoid sudden large corrections)
• CONTINUOUS NEUROMONITORING during correction - if MEP/SSEP changes occur, STOP immediately
• Modern segmental pedicle screw fixation allows THREE-COLUMN correction (better than historical Harrington distraction which was two-point fixation and primarily distraction)
• Sequentially tighten set screws while applying corrective forces (locks in incremental correction)
• Typical curve correction: 50-70% of preoperative Cobb angle (overcorrection risks neurological injury and coronal imbalance)
• Residual Cobb angle 20-30 degrees is acceptable and safe

Axial Rotation Correction - Rod Derotation

• Scoliosis is THREE-DIMENSIONAL deformity: coronal curve + sagittal profile changes + AXIAL ROTATION
• Vertebral bodies rotate toward convexity in scoliosis (ribs follow vertebral bodies - posterior rib hump on convex side)
• Rod Derotation Technique: With rods provisionally secured, apply derotation force using rod holders or derotation instruments
• Rotate CONCAVE ROD posteriorly (90 degrees rotation for right thoracic curve - rotate clockwise; for left thoracic rotate counterclockwise)
• Effect: Translates apical vertebrae toward midline, improves rib hump deformity (30-50% improvement typical)
• Limit derotation: Excessive rotation can cause loss of thoracic kyphosis (flat-back) or neurological injury
• Check neuromonitoring during derotation
• Alternative technique: Direct Vertebral Derotation (DVR) - forceps applied directly to vertebrae, rotate under fluoroscopy control
• Sequential set screw tightening locks in rotational correction

Final Construct Assembly

• After correction maneuvers (compression, distraction, derotation), perform FINAL SET SCREW TIGHTENING
• Use calibrated torque wrenches or torque-limiting drivers (typically 80-120 in-lbs depending on screw system - follow manufacturer specifications)
• Tighten systematically from UIV to LIV (or LIV to UIV - surgeon preference) - ensures even load distribution
• Apply CROSS-LINKS (transverse connectors) between rods:
  • Typically place at apex of major curve and at UIV (some surgeons add third at LIV)
  • Improves construct torsional rigidity, prevents rod migration, distributes loads
  • May use rigid or hinged cross-links
• Obtain INTRAOPERATIVE RADIOGRAPHS (AP and lateral full-spine if C-arm large enough, or fluoroscopy spot images)
• Verify: Screw positions satisfactory, coronal Cobb angle improvement (calculate correction percentage), sagittal alignment appropriate (kyphosis/lordosis), balanced alignment (C7 plumb line centered over sacrum), no hardware prominence
• CHECK NEUROMONITORING FINAL - ensure signals stable or returned to baseline

Arthrodesis Technique

Bone Graft Application

• Bone graft ESSENTIAL for successful fusion (fusion rate 95-98% in AIS with modern techniques)
• Local Autograft (gold standard): Bone collected from decortication of spinous processes, laminae, facets, transverse processes
  • Contains all three properties: OSTEOGENIC (viable bone cells), OSTEOINDUCTIVE (growth factors like BMPs), OSTEOCONDUCTIVE (scaffold for bone ingrowth)
  • Best graft material available - use generously
  • Typically harvest 20-30 cc local autograft from multilevel fusion
• Allograft (freeze-dried cancellous chips or corticocancellous chips):
  • OSTEOCONDUCTIVE only (no viable cells, minimal growth factors)
  • Use as extender to increase graft volume if local autograft insufficient
  • Mix with local autograft in 1:1 or 1:2 ratio (autograft:allograft)
• Demineralized Bone Matrix (DBM):
  • Processed allograft with OSTEOINDUCTIVE potential (contains BMPs)
  • Available as putty, gel, or paste formulations
  • Use as supplement, not primary graft
• Bone Morphogenetic Protein (rhBMP-2):
  • Very potent osteoinductive agent (recombinant human BMP-2, e.g., Infuse)
  • OFF-LABEL use in pediatric spine (FDA approved only for adult anterior lumbar interbody fusion)
  • Controversial: expensive ($3000-5000), risk of excessive bone formation, seroma formation, unknown long-term effects in adolescents
  • If used: Low dose (1/2 to 1 kit for multilevel fusion), avoid placement in spinal canal (can cause swelling and compression)
• Bone Graft Substitutes: Ceramics (hydroxyapatite, tricalcium phosphate) - osteoconductive, used as extenders

Graft Placement Technique

• Mix bone graft with patient's blood (creates paste consistency, easier to pack and adhere)
• Pack graft into ALL FACET JOINTS bilaterally (facet fusion is primary fusion mass - critical)
• Apply graft over decorticated laminae (create continuous bone bridge)
• Apply along transverse processes (posterolateral fusion mass)
• Use bone tamps to compress graft firmly into decorticated surfaces (improves contact)
• Goal: Complete coverage of all instrumented levels with continuous bony bridge from UIV to LIV posteriorly
• Typical graft volume: 30-50 cc total for 10-15 level fusion (combination of autograft and allograft)
• Ensure graft NOT placed in spinal canal or neural foramina (risk: nerve compression)

Fusion Biology

• Fusion process: Inflammatory phase (1-2 weeks), repair phase (2-6 weeks with soft callus), remodeling phase (3-12 months with hard callus and bridging bone)
• Fusion assessment: Clinical (pain-free, no motion on flexion-extension radiographs), Radiographic (bridging bone on CT scan at 12-24 months - gold standard)
• Factors promoting fusion: Adequate decortication, generous bone graft, rigid fixation, patient factors (young age, good nutrition, non-smoker, avoid NSAIDs)
• Factors inhibiting fusion: Smoking (2-4x pseudarthrosis risk), NSAIDs (COX inhibition impairs bone healing - avoid first 3 months), malnutrition, infection, motion at fusion site, inadequate graft

Hemostasis and Wound Closure

Hemostasis

• Meticulous hemostasis CRITICAL (reduces transfusion, hematoma, infection risk)
• Electrocautery for muscle bleeding
• Bone wax for bone bleeding (use sparingly - inhibits local fusion if excessive)
• Topical hemostatic agents:
  • Gelatin sponge (Gelfoam) soaked in thrombin solution - apply to oozing surfaces
  • Flowable hemostatic matrix (Floseal - gelatin matrix + human thrombin)
  • Oxidized cellulose (Surgicel) - apply to raw surfaces
• Irrigate wound with copious antibiotic solution (controversial - some use bacitracin 50,000 units in 3L saline, others use saline only due to bacitracin anaphylaxis risk)
• Consider tranexamic acid (TXA) topical application (1-2 grams in 100 mL saline, soak for 5 minutes before closure - may further reduce postop bleeding)

Drain Placement

• Subfascial closed-suction drains: Two large-bore drains (19F Blake or Jackson-Pratt)
• Position drains along length of fusion, avoiding direct contact with hardware
• Bring drains out through separate stab incisions lateral to main wound (not through main incision - reduces infection risk)
• Purpose: Prevent hematoma formation, reduce postoperative pain and swelling
• Drain management: Remove when output <30-50 cc per 8-hour shift (typically POD 2-4)
• Controversy: Some surgeons do not use drains routinely (argue no benefit and potential infection risk), others use routinely for large exposures

Infection Prevention

• Vancomycin Powder: Some surgeons apply 1-2 grams vancomycin powder to wound before closure (sprinkle over bone graft and in subcutaneous layer)
  • OFF-LABEL use, evidence mixed (some studies show reduced SSI rate from 5% to 2%, others show no benefit)
  • Theoretical concern: Local antibiotic resistance, aseptic seroma
  • Many spine surgeons use routinely, others avoid
• Maintain normothermia (core temp >36°C) - hypothermia increases infection risk
• Maintain perioperative glucose <180 mg/dL (hyperglycemia increases SSI)
• Re-prep skin before closure (some surgeons)

Layered Closure

• Deep Layer - Lumbodorsal Fascia: Heavy absorbable suture (#0 or #1 Vicryl or PDS)
  • Running or interrupted technique (running faster, interrupted theoretically stronger)
  • Fascia closure CRITICAL (provides wound strength, prevents hernia/dehiscence)
  • Ensure tension-free approximation (if high tension, consider relaxing incisions)
  • Some surgeons use barbed suture (V-Loc, Stratafix) for fascia - faster, self-locking, no knots
• Muscle Layer: May place additional absorbable sutures (0 or 2-0 Vicryl) if large muscle gap - helps approximate dead space
• Subcutaneous Layer: Absorbable suture (2-0 or 3-0 Vicryl) in interrupted or running fashion
  • Close deep subcutaneous layer (Scarpa's fascia) to reduce dead space
  • Place superficial subcutaneous layer
• Skin Closure:
  • Option 1: Subcuticular absorbable suture (3-0 or 4-0 Monocryl or Biosyn) - best cosmetic result, no removal needed (important for adolescent patients concerned about appearance)
  • Option 2: Skin staples - faster but requires removal at 2 weeks, leaves staple marks
  • Skin adhesive (Dermabond) over top of closure for additional seal and waterproofing
• Dressing: Sterile absorbent dressing (standard gauze and tape) OR negative pressure wound therapy dressing (NPWT like Prevena for high-risk patients - obese, diabetic, revision)

Immediate Postoperative Care (POD 0-1)

ICU or Monitored Bed

• Admit to ICU or step-down unit for first 24 hours (monitor hemodynamic status, neurological status, drains)
• Continuous telemetry and pulse oximetry
• Neurological checks HOURLY for first 24 hours:
  • Lower extremity motor (ask patient to wiggle toes, dorsiflex/plantarflex feet) - should be 5/5
  • Sensation (light touch lower extremities) - should be intact
  • Any deficit: URGENT evaluation (examine patient, check neuromonitoring records, consider MRI if concern for hematoma or cord injury)

Pain Management

• Multimodal analgesia approach (reduce opioid consumption, minimize side effects):
  • IV Patient-Controlled Analgesia (PCA) with opioid (morphine 1mg q6min, hydromorphone 0.2mg q6min) - backbone of pain control first 24-48 hours
  • Scheduled acetaminophen (1000mg PO/IV q6h) - mild analgesic, opioid-sparing
  • Gabapentin or pregabalin (gabapentin 300-600mg TID, pregabalin 75-150mg BID) - neuropathic pain, opioid-sparing
  • Muscle relaxants (cyclobenzaprine 5-10mg TID, tizanidine 2-4mg TID) - reduce muscle spasm
  • Ketorolac (Toradol 15-30mg IV q6h) - potent NSAID, use ONLY first 24-48 hours then STOP (NSAIDs inhibit fusion - controversial but many surgeons avoid after initial perioperative period)
• Transition to oral opioids POD 2-3 (oxycodone 5-10mg q4-6h PRN)
• Wean opioids by discharge (typically POD 3-5) - prescribe limited supply (10-14 days maximum)

Blood Management

• Monitor hemoglobin/hematocrit q6-12h initially
• Transfusion threshold: Hgb <7-8 g/dL (restrictive strategy per modern guidelines), or symptomatic anemia (tachycardia, hypotension, dizziness)
• Cell saver blood (if used intraoperatively) can be reinfused up to 6 hours postop
• Drain output monitoring: Record q8h, expect 100-300 cc per 8h initially, decreasing trend

Pulmonary Care

• Incentive spirometry q1-2h while awake (prevent atelectasis - common after long prone surgery)
• Supplemental oxygen to maintain SpO2 >94%
• Early mobilization to sitting position (improves lung expansion)
• Chest physiotherapy if poor effort or concerning exam findings
• If curve was >70 degrees preoperatively: Closer respiratory monitoring (risk: restrictive lung disease, pneumonia)

DVT Prophylaxis

• Mechanical prophylaxis: Sequential compression devices (SCDs) bilateral lower extremities, start in OR and continue until ambulatory
• Chemical prophylaxis: Controversial timing (balance bleeding risk vs VTE risk)
  • Low-risk patient (young, healthy, ambulatory POD 1): Mechanical only until ambulatory
  • Higher-risk (obese, limited mobility, prior VTE): Consider low-molecular-weight heparin (enoxaparin 40mg SC daily) starting POD 1-2 once drains removed and bleeding controlled
• Early ambulation (best DVT prophylaxis)

Gastrointestinal

• Ileus common after long spine surgery in prone position (bowel edema, opioid-induced, manipulation)
• NPO or clear liquids initially, advance diet as tolerated (return of bowel sounds, passing flatus)
• Antiemetics PRN (ondansetron 4mg IV q6h PRN) - nausea common from opioids and ileus
• Stool softeners (docusate 100mg BID) to prevent constipation from opioids
• If ileus prolonged (>3-4 days): NG tube decompression, promotility agents (metoclopramide), aggressive bowel regimen

Bladder

• Foley catheter placed intraoperatively, continue first 24-48 hours (monitor urine output, prevent urinary retention from opioids)
• Remove Foley POD 1-2 when patient ambulatory and pain controlled (reduces CAUTI risk)
• Monitor for urinary retention after Foley removal (bladder scan if no void within 6-8 hours)

Inpatient Recovery (POD 1-5)

Mobilization Protocol

• POD 0 (day of surgery): Bed rest, log roll for position changes (maintain spinal alignment)
• POD 1: Sit in chair with PT/nursing assistance, dangle legs at bedside (assess orthostasis - common after blood loss and bed rest)
• POD 1-2: Ambulate with PT assistance - start with short distances (room to hallway), walker or assistance as needed
• POD 2-3: Increase ambulation distance, goal independent ambulation or minimal assist
• NO brace typically required for instrumented AIS fusion with pedicle screw constructs (construct is stable - historical hook/wire constructs required postop bracing)
• May use soft lumbar brace or thoracolumbar corset for COMFORT first 4-6 weeks (not structural - just reminder to protect spine and reduces muscle spasm)

Drain Management

• Monitor drain output q8h (record on flowsheet)
• Expect decreasing output trend: POD 1 (100-300cc/8h), POD 2 (50-150cc/8h), POD 3 (30-80cc/8h)
• Remove drains when output <30-50 cc per 8-hour shift (typically POD 2-4)
• If output remains high (>100cc/8h after POD 3): Investigate (bleeding source, CSF leak if clear fluid - send for beta-2 transferrin)

Radiographic Evaluation

• Obtain standing PA and lateral 36-inch spine radiographs before discharge (if patient able to stand)
• If unable to stand: Sitting or supine AP/lateral radiographs
• Assess: Coronal Cobb angle (calculate correction %), sagittal alignment (kyphosis/lordosis), coronal balance (C7 plumb line to CSVL), sagittal balance (C7 plumb line to posterior superior S1), hardware position (screws, rods intact, no migration)
• Compare to intraoperative radiographs (ensure no early hardware failure or position change)

Discharge Criteria

• Pain controlled on oral medications
• Tolerating regular diet (no nausea/vomiting, no ileus)
• Ambulating independently or with minimal assistance
• Adequate family/caregiver support at home
• Drains removed
• Neurologically intact
• No concerning wound issues (no drainage, no signs of infection)
• Typical hospital stay: 3-5 days for uncomplicated AIS PSF

Outpatient Recovery and Rehabilitation

Activity Restrictions

• First 3 months (until fusion solid):
  • NO BLT: Bending at waist, Lifting >5-10 lbs, Twisting of spine
  • Avoid high-impact activities (running, jumping, contact sports)
  • Encourage walking (gradually increase distance - excellent low-impact activity promotes healing)
  • May climb stairs, ride in car (short trips), perform activities of daily living
• 3-6 months:
  • Gradually liberalize activities if radiographs show healing
  • May begin light recreational activities (swimming, stationary bike)
  • Return to school full-time (most patients return 3-4 weeks postop, initially half-days)
• 6-12 months:
  • Return to non-contact sports (tennis, volleyball, golf) at 6 months if fusion progressing
  • Return to contact sports (basketball, soccer, football) at 9-12 months after CONFIRMED FUSION on CT
  • Full activities without restrictions once fusion solid (12-24 months)

Medication Management

• Pain medications:
  • Opioids (oxycodone 5-10mg q4-6h PRN): Prescribe limited supply (7-14 days), wean by 2-3 weeks
  • Acetaminophen 1000mg q6h standing - continue 4-6 weeks
  • Gabapentin 300-600mg TID - continue 4-6 weeks then taper (prevents neuropathic pain)
  • Muscle relaxants PRN (cyclobenzaprine, tizanidine) - first 2-4 weeks
• AVOID NSAIDs for first 3 MONTHS (COX inhibition impairs bone healing and fusion - controversial but many surgeons recommend avoidance during critical fusion period)
• Stool softeners while on opioids

Wound Care

• Keep incision dry and covered for first 2 weeks (sponge baths, no submersion)
• Remove dressing at 2 weeks (if subcuticular closure with absorbable suture - no removal needed)
• If skin staples used: Remove at 2-week postop visit
• May shower after 2 weeks once incision sealed (no submersion in bath/pool for 6 weeks)
• Watch for signs of infection: Increasing redness, warmth, swelling, drainage, fever >38.5°C (report immediately)

Follow-Up Schedule

• 2 weeks: Wound check, staple removal if used, assess pain control and functional status
• 6 weeks: Clinical exam, AP/lateral standing radiographs (assess alignment, hardware position, early fusion progress), advance activities (return to school full-time, light activities)
• 3 months: Radiographs, advance activities (discontinue activity restrictions, begin light sports), assess pain
• 6 months: Radiographs, assess fusion progress, clear for non-contact sports if fusion progressing well
• 12 months: Radiographs, CT scan (gold standard for fusion assessment - look for bridging bone through facets and over transverse processes bilaterally), clear for contact sports if fused
• 24 months: Final radiographs, discharge from active follow-up if stable, fused, and doing well (annual check-ins recommended lifelong to monitor for late complications like PJK)

Physical Therapy

• NOT typically required for uncomplicated AIS PSF (patient self-directs recovery with activity advancement)
• May refer for PT if: Deconditioning, gait abnormalities, pain management assistance, core strengthening at 3-6 months
• Focus on core strengthening (abdominal and paraspinal muscles), cardiovascular conditioning, flexibility
• Avoid aggressive manipulation or aggressive passive range of motion of spine (risk: fusion disruption)

Complications and Management

Early Complications (0-6 weeks)

• Neurological Deficit: If new deficit postop: URGENT MRI (rule out epidural hematoma, instrumentation malposition, cord injury), Neuro exam by spine surgeon, Consider re-exploration if hematoma or correctable cause, High-dose steroids controversial (methylprednisolone protocol per institutional guidelines)
• Infection (superficial SSI 2-5%, deep SSI 1-3%): Superficial: Oral antibiotics if cellulitis, I&D if abscess; Deep: Return to OR for irrigation and debridement, culture-specific IV antibiotics 6 weeks, retain hardware if possible (early infection <3 months may clear with hardware in place), remove hardware if chronic infection or failure to clear
• Wound Dehiscence: Superficial separation: Local wound care, steri-strips; Deep fascial dehiscence: Return to OR for reclosure
• Hematoma: If symptomatic (pain, wound swelling, drainage): Return to OR for evacuation
• Ileus: Conservative management (NPO, NG tube, bowel rest), promotility agents, typically resolves POD 3-5
• Pulmonary Complications (atelectasis, pneumonia, PE): Incentive spirometry, mobilization, antibiotics if pneumonia, anticoagulation if PE

Late Complications (>6 weeks)

• Pseudarthrosis (2-5%): Presents with persistent pain, motion on flexion-extension radiographs, lucency around hardware, or rod fracture (rod fracture = pseudarthrosis until proven otherwise). Diagnosis: Flexion-extension radiographs (motion >3mm), CT scan (no bridging bone). Treatment: If asymptomatic - observe; If symptomatic - revision fusion (add bone graft, extend fusion if needed, exchange broken hardware)
• Proximal Junctional Kyphosis (PJK) (10-30%): Definition - >10° kyphosis between UIV and UIV+2, AND >10° greater than preop. Presents with proximal back pain, visible kyphosis. Radiographs show kyphotic angulation at UIV. Treatment: If asymptomatic and no progression - observe; If symptomatic or progressive - revision with extension of fusion proximally
• Distal Adding-On Deformity (5-10%): Progression of curve distal to LIV (LIV selection error - stopped above stable vertebra). Treatment: Revision with extension of fusion distally if progressive or symptomatic
• Implant Failure (rod fracture 1-2%, screw breakage <1%): Usually indicates pseudarthrosis (motion at fusion site fatigues hardware). Diagnosis: Radiographs show broken rod or screw. Treatment: If fused - may observe or remove if symptomatic; If not fused (pseudarthrosis) - revision fusion
• Chronic Pain (5-10%): May be neuropathic (nerve injury), mechanical (hardware prominence, facet arthritis above/below fusion), or psychosocial. Workup: Exam, radiographs, consider MRI. Treatment: Multimodal pain management, PT, injections, hardware removal if prominent, revision surgery rarely indicated for pain alone
• Junctional Degeneration: Accelerated disc and facet degeneration adjacent to fusion (especially proximally). May develop years later. Treatment: Conservative management (PT, injections), revision fusion if severe symptomatic degeneration