import { ComparisonTable, ContentSection, EvidenceCard, ExamCheatSheet, ExamPearl, ExamWarning, MnemonicCard, OnePagerSummary, VivaScenario, VivaScenarioSection } from '@/components/mdx' # Spinal Osteotomy Techniques: PSO, VCR, and SPO PSO and VCR are high-risk procedures requiring experienced surgical teams, neuromonitoring, ICU capability, and appropriate patient selection. Examiners assess: (1) Biomechanical principles - which osteotomy for which deformity, (2) Technical mastery of each procedure, (3) Ability to prevent and manage neurological complications. Know the Schwab classification grades, correction potential per level, and response to neuromonitoring changes. Spinal osteotomies enable powerful deformity correction with increasing complexity and risk. **SPO (Smith-Petersen osteotomy)** is a posterior column only procedure providing **10 degrees per level** through a posterior-opening wedge with intact anterior column as hinge. **PSO (pedicle subtraction osteotomy)** resects all three columns via posterior approach, achieving **30-40 degrees correction** at a single level with 10-15mm shortening. **VCR (vertebral column resection)** removes the entire vertebra allowing **50-70 degrees correction** but carries highest risk. Neurological complication rates increase with complexity: SPO 1-3%, PSO 5-11%, VCR 10-25%. Match osteotomy type to deformity magnitude - neuromonitoring is mandatory. ### Three-Column Concept of the Spine **Denis Three-Column Model:** 1. **Anterior Column:** - Anterior longitudinal ligament - Anterior half of vertebral body - Anterior half of disc 2. **Middle Column:** - Posterior half of vertebral body - Posterior half of disc - Posterior longitudinal ligament 3. **Posterior Column:** - Pedicles, laminae, facets - Ligamentum flavum - Interspinous and supraspinous ligaments **Osteotomy Classification by Columns Affected:** - **SPO**: Posterior column only (Grade 1-2 osteotomy) - **PSO**: All three columns (Grade 3 osteotomy) - **VCR**: All three columns with complete vertebral resection (Grade 4-6 osteotomy) ### Biomechanical Principles **Axis of Rotation:** - **SPO**: Axis anterior to anterior longitudinal ligament - Opens posteriorly, closes anteriorly - Requires intact anterior column to act as hinge - Limited correction potential per level - **PSO**: Axis through middle of vertebral body - Symmetrical closure - No anterior column hinge required - Greater correction potential per level - **VCR**: Axis at surgeon's choice (depends on rod position) - Maximum flexibility in correction plane - Can address both sagittal and coronal deformity simultaneously - Requires temporary instability during closure **Correction Potential:** - SPO: 10 degrees per level (range 5-15 degrees) - PSO: 30-40 degrees per level (range 25-45 degrees) - VCR: 50-70 degrees per level (range 40-80 degrees) **Spinal Shortening:** - SPO: Minimal shortening (anterior column intact) - PSO: 10-15mm shortening at osteotomy level - VCR: 20-40mm shortening (entire vertebra removed) - Shortening relaxes neural elements but may affect visceral structures ### Anatomical Considerations **Vascular Anatomy:** - **Lumbar Segmental Arteries**: Exit at mid-vertebral body - At risk during PSO (vertebral body resection) - Sacrifice usually tolerated due to collaterals - Excessive bleeding risk in vascular disease - **Artery of Adamkiewicz**: - Typically T9-L2 on left (75% of cases) - Major anterior spinal artery supply - Injury causes paraplegia (anterior cord syndrome) - Risk minimized by maintaining MAP greater than 85 mmHg **Neural Anatomy:** - **Conus Medullaris**: Typically T12-L2 - Higher risk of myelopathy if osteotomy at this level - Lumbar levels (L3-L4) preferred for PSO - **Cauda Equina**: Below L2 - More tolerant of manipulation than spinal cord - Individual nerve roots can be mobilized - **Exiting vs Traversing Roots**: - Exiting root in neural foramen (vulnerable to pedicle work) - Traversing root medial to pedicle (vulnerable to canal work) ### Schwab Classification of Spinal Osteotomies ### Anatomic Location Classification **Cervical Osteotomies:** - Highest neurological risk (spinal cord injury = quadriplegia) - Typically SPO or opening wedge osteotomy - PSO/VCR rarely performed (extreme risk) **Thoracic Osteotomies:** - T1-T10: Spinal cord present, myelopathy risk - Narrow canal, less room for error - PSO preferred over VCR when possible **Thoracolumbar Osteotomies:** - T11-L2: Conus medullaris level (high risk) - Avoid if possible, prefer L3-L4 for PSO **Lumbar Osteotomies:** - L3-L4: Preferred level for PSO (below conus, cauda equina tolerates manipulation) - L5: Avoid PSO (proximity to sacrum, large vessels) **Sacral Osteotomies:** - Rare, typically for pelvic incidence reduction - S1 or S2 level - Risk of bowel/bladder dysfunction ### Deformity-Based Classification **Sagittal Plane Deformities:** - **Flatback**: PSO for lordosis restoration - **Kyphosis**: PSO or VCR depending on magnitude and rigidity - **Chin-on-chest**: Multiple SPOs or cervicothoracic VCR **Coronal Plane Deformities:** - **Scoliosis**: Asymmetric VCR for coronal and rotational correction - **Coronal Imbalance**: VCR at apex with lateral translation **Combined Deformities:** - **Kyphoscoliosis**: VCR for simultaneous sagittal and coronal correction - **3D Deformity**: Multiple osteotomies or extended VCR ### Patient Selection for Osteotomy **Ideal Candidate for PSO:** - Fixed sagittal imbalance (SVA greater than 50mm, PI-LL mismatch greater than 20 degrees) - Failed conservative management (minimum 6 months) - Rigid deformity not correctable with positioning - Good bone quality (T-score greater than -2.0) - Age less than 70 years - Medical fitness for major surgery - Realistic expectations **Contraindications to Osteotomy:** **Absolute:** - Active infection at osteotomy site - Severe osteoporosis (T-score less than -3.5) without treatment - Prohibitive medical comorbidities (severe cardiac, pulmonary disease) - Unrealistic expectations or psychiatric contraindications **Relative:** - Age greater than 75 years - Moderate osteoporosis (T-score -2.5 to -3.0) - Prior radiation to osteotomy site - Severe obesity (BMI greater than 40) - Revision at same level ### Deformity Assessment **Radiographic Assessment:** - **Standing Full-Length Spine**: AP and lateral - **Sagittal Parameters**: - SVA: Normal less than 50mm - PI-LL mismatch: Normal within 10 degrees - Pelvic tilt: Compensation mechanism (normal less than 20 degrees) - Thoracic kyphosis: Normal 20-50 degrees **Deformity Magnitude:** - **Mild**: SVA 50-75mm, PI-LL 10-20 degrees → Multiple SPOs - **Moderate**: SVA 75-150mm, PI-LL 20-40 degrees → Single PSO - **Severe**: SVA greater than 150mm, PI-LL greater than 40 degrees → PSO + SPOs or VCR **Flexibility Assessment:** - **Supine Hyperextension Film**: Assesses deformity flexibility - **Traction Films**: Pull test for deformity reducibility - **Rigid Deformity**: Less than 10 degree correction on flexibility films → PSO or VCR - **Flexible Deformity**: Greater than 20 degree correction → SPOs may suffice ### Preoperative Evaluation **Medical Clearance:** - Cardiac evaluation (ECG, echo if indicated, stress test if CAD risk) - Pulmonary function tests if restrictive lung disease - Renal function (creatinine clearance for contrast studies, blood loss) - Coagulation studies and type/screen (anticipate 2-4 unit PRBC transfusion) **Neurological Baseline:** - Document complete neurological examination - MRI to assess spinal cord (myelomalacia, stenosis, tumor) - Consider urodynamics if bowel/bladder symptoms **Bone Quality:** - DEXA scan mandatory - Optimize if osteoporotic (vitamin D, calcium, teriparatide) - Consider cement augmentation if T-score less than -2.5 **Osteotomy Selection Algorithm:** 1. **Assess Deformity Magnitude:** - SVA less than 100mm with flexible deformity: Multiple SPOs - SVA 100-150mm with rigid deformity: Single PSO at L3 - SVA greater than 150mm or severe angular deformity: PSO + SPOs or VCR 2. **Evaluate Rigidity:** - Greater than 20 degrees correction on flexibility films: SPOs may suffice - Less than 10 degrees correction: Requires bony osteotomy (PSO or VCR) 3. **Match Correction to Deformity:** - SPO: 10 degrees per level (posterior column only) - PSO: 30-40 degrees per level (all three columns) - VCR: 50-70 degrees per level (complete vertebrectomy) ### Smith-Petersen Osteotomy (SPO) **Indications:** - Flexible kyphosis requiring 10-30 degrees total correction - Ankylosing spondylitis with mild-moderate deformity - Scheuermann's kyphosis - Post-laminectomy kyphosis (iatrogenic flatback) **Technique:** **Step 1 - Exposure:** - Midline incision over planned osteotomy levels - Subperiosteal dissection exposing laminae and facets - Identify levels with radiograph (count from C7 or sacrum) **Step 2 - Posterior Element Resection:** - Remove inferior facet completely (leave superior facet intact) - Remove ligamentum flavum - Resect spinous process and interspinous ligament - Thin superior lamina to create hinge point - Wide resection creates V-shaped gap **Step 3 - Instrumentation:** - Place pedicle screws 2-3 levels above and below each osteotomy - Temporary rods to maintain stability during multiple osteotomies **Step 4 - Closure:** - Gradual compression on rods closes posterior gap - Anterior column acts as hinge (must be intact) - Monitor neuromonitoring during closure - Achieve desired lordosis restoration **Step 5 - Final Fixation:** - Permanent rod placement - Cross-links for rotational stability - Bone graft over osteotomy sites **Pearls:** - Multiple levels better than single level (distributes stress) - Apex of kyphosis is optimal location - Preserve anterior column (DO NOT violate anterior longitudinal ligament) - Gradual closure reduces neurological risk **Pitfalls:** - Fracture through anterior column (loss of hinge, unstable) - Excessive correction at single level (neurological injury) - Inadequate facet resection (limited correction, rod stress) ### Pedicle Subtraction Osteotomy (PSO) **Indications:** - Fixed sagittal imbalance requiring 30-40 degrees correction - Flatback deformity with PI-LL mismatch greater than 20 degrees - Rigid kyphosis not amenable to SPO - Revision deformity surgery **Optimal Level Selection:** - **L3**: Most common (below conus, good bone stock, central lordosis) - **L2**: Acceptable if L3 anatomy unfavorable - **L4**: Avoid if possible (proximity to L5-S1, lordosis distribution) - **Thoracic**: High risk (spinal cord), avoid if possible **Technique:** **Step 1 - Exposure and Instrumentation:** - Wide midline exposure from 3-4 levels above to 3-4 levels below - Place all pedicle screws first (including osteotomy level) - Temporary rods for stability - Identify osteotomy level with fluoroscopy **Step 2 - Posterior Element Resection:** - Complete laminectomy at osteotomy level (L3) - Bilateral facetectomy (L2-L3 and L3-L4) - Resect spinous processes L2, L3, L4 - Expose pedicles completely (circumferential) - Identify and protect nerve roots (exiting L3 root at risk) **Step 3 - Pedicle Resection:** - Remove pedicles with osteotomes or high-speed burr - Start lateral, work medial to avoid nerve injury - Create cortical shell of posterior vertebral body - Expose lateral walls of vertebral body **Step 4 - Vertebral Body Resection:** - Use curettes, osteotomes, or high-speed burr - Create wedge-shaped defect (wider posteriorly) - Preserve anterior cortex (1-2mm shell) - Angle: 30-40 degrees from horizontal - Copious irrigation to prevent thermal injury **Step 5 - Temporary Stabilization:** - Place temporary rods with moderate compression - Prevents premature closure during contralateral work - Maintain canal decompression **Step 6 - Closure:** - Gradually compress bilateral rods - Posterior wedge closes, anterior cortex fractures (controlled hinge) - Monitor neuromonitoring (SSEP, MEP) continuously - Stop if significant neuromonitoring changes - Shortening of 10-15mm relaxes neural elements **Step 7 - Final Fixation:** - Permanent rod placement (cobalt-chromium 6.0-6.35mm) - Dual rods for high-stress cases - Multiple cross-links (every 3-4 levels) - Bone graft entire construct **Intraoperative Pearls:** - **Four-Rod Technique**: Temporary rods during osteotomy, permanent rods after closure - **Cell Saver**: Autotransfusion reduces allogeneic blood transfusion - **Hypotensive Anesthesia**: Reduce blood loss (maintain MAP 65-70 during resection) - **Maintain MAP greater than 85 during closure**: Spinal cord perfusion - **Have wake-up test ready**: If neuromonitoring changes persist **Complications During PSO:** - **Excessive Bleeding**: Segmental arteries, epidural plexus - Management: Hemostatic agents, temporary closure, blood transfusion - **Neurological Injury**: Traction on nerve roots, cord ischemia - Management: Release compression, augment blood pressure, consider wake-up test - **Anterior Cortex Fracture Too Early**: Uncontrolled closure - Management: Temporary stabilization, controlled gradual closure - **Inadequate Correction**: Insufficient bone resection - Management: Remove more bone (carefully), accept and add SPO at adjacent level ### Vertebral Column Resection (VCR) **Indications:** - Severe rigid deformity requiring greater than 50 degrees correction - Sharp angular kyphosis (kyphoscoliosis) - Congenital deformity (hemivertebra, bar) - Tumor resection with reconstruction - Failed PSO requiring salvage **Level Selection:** - Apex of deformity (maximum correction with single level) - Avoid conus medullaris (T12-L2) if possible - Thoracic VCR requires ICU monitoring (cord injury = paraplegia) **Technique:** **Step 1 - Extensive Exposure:** - Wide exposure 5-6 levels above and below - Circumferential exposure of vertebra to be resected - Place all pedicle screws excluding VCR level **Step 2 - Posterior Element Removal:** - Complete laminectomy at VCR level and adjacent levels - Bilateral facetectomies above and below - Identify and protect nerve roots (dura completely exposed) **Step 3 - Pedicle and Posterior VB Resection:** - Resect pedicles bilaterally with burr or osteotome - Remove posterior wall of vertebral body - Create working channel to anterior column **Step 4 - Lateral and Anterior VB Resection:** - Blunt dissection laterally (protect great vessels) - Ligate segmental arteries if necessary - Resect vertebral body completely (anterior cortex last) - Elevate disc above and below (remove completely) **Step 5 - Temporary Stabilization:** - Place temporary rods to prevent catastrophic collapse - Dura completely exposed (360 degree decompression) - Sac of neural elements free-floating **Step 6 - Gradual Closure and Correction:** - Slowly compress rods to close gap - Monitor neuromonitoring continuously - Translate spine as needed for coronal correction - Rotate spine for rotational correction - Shortening of 20-40mm **Step 7 - Anterior Column Reconstruction:** - Place structural graft (cage, mesh, allograft bone) - Provides anterior column support - Allows bone ingrowth for fusion - Prevents kyphosis recurrence **Step 8 - Final Fixation:** - Robust fixation with dual rods (four-rod construct) - Cobalt-chromium 6.35mm diameter - Multiple cross-links for stability - Extend fixation 4-5 levels beyond VCR **Anterior vs Posterior-Only VCR:** **Posterior-Only (Single-Stage):** - Advantages: Single surgery, less morbidity, shorter recovery - Disadvantages: Limited anterior access, higher blood loss, more technically demanding - Preferred for most cases if surgeon experienced **Staged Anterior-Posterior:** - Advantages: Better anterior column visualization, controlled resection - Disadvantages: Two surgeries, increased morbidity, longer hospitalization - Indicated for: Tumor resection, extensive anterior pathology, vascular anomalies **Complications of VCR:** - **Neurological Injury (10-25%)**: Highest of all osteotomies - Prevention: Meticulous technique, neuromonitoring, gradual closure - **Vascular Injury**: Great vessels, segmental arteries - Prevention: Blunt dissection, vascular surgery standby for thoracic VCR - **Massive Blood Loss**: Average 2-5 liters - Prevention: Cell saver, controlled hypotension, hemostatic agents - **Construct Failure**: Rod fracture, screw pullout - Prevention: Robust fixation (dual rods, extend fixation) ### Immediate Postoperative Care (ICU - First 24-48 Hours) **Neurological Monitoring:** - **Frequent Neuro Checks**: Every 1-2 hours for first 24 hours - **Document**: Motor strength (all myotomes), sensation, reflexes - **Wake Patient Early**: Assess for deficits as soon as safely extubated - **Urgent MRI if Deficit**: Rule out hematoma, hardware malposition **Hemodynamic Management:** - **Maintain MAP greater than 85 mmHg**: Spinal cord perfusion (first 48 hours) - **Vasopressors if Needed**: Phenylephrine or norepinephrine - **Fluid Resuscitation**: Replace blood loss (target Hb greater than 8 g/dL) - **Monitor Urine Output**: Target greater than 0.5 mL/kg/hour **Pain Management:** - **Multimodal Analgesia**: Acetaminophen, NSAIDs (if renal function allows), gabapentin - **Epidural**: Excellent pain control if placed preoperatively - **PCA (Patient-Controlled Analgesia)**: Opioids as needed - **Avoid Excessive Opioids**: Delirium, ileus, respiratory depression **Drain Management:** - **Closed Suction Drains**: Monitor output (expect 200-400 mL first 24 hours) - **Remove When Output less than 50 mL per 8 hours**: Typically POD 2-3 - **Watch for Excessive Bleeding**: Greater than 500 mL in 8 hours → consider re-exploration ### Early Mobilization (POD 1-5) **Out of Bed:** - **POD 1**: Sit at edge of bed if neurologically intact - **POD 2**: Sit in chair, stand with assistance - **POD 3**: Walk with walker or assistance - **Goal**: Walking independently by discharge **Bracing:** - **TLSO Brace**: For PSO/VCR patients, worn for 12 weeks - **No Brace if SPO Only**: Unless multiple levels or poor bone quality - **Custom-Molded**: Better fit, compliance **Physical Therapy:** - **Early Mobilization**: Reduces DVT, pneumonia, ileus - **Core Strengthening**: Gentle isometrics (no trunk rotation for 12 weeks) - **Gait Training**: Restore normal gait pattern - **ADL Training**: Transfers, stairs, dressing ### Complications and Management **Neurological Deficit:** **Immediate Postoperative Deficit:** - **Urgency**: Emergent evaluation - **Differential**: Epidural hematoma (most common), hardware malposition, cord ischemia - **Workup**: Urgent MRI, check coagulation studies - **Management**: - Hematoma: Emergent evacuation (decompress within 8 hours for best recovery) - Hardware malposition: Revision to remove offending screw/rod - Cord ischemia: Augment MAP to 90-100 mmHg, steroids controversial (no proven benefit) **Delayed Deficit (POD 1-7):** - **Causes**: Delayed hematoma, overcorrection with stretch injury, cord ischemia - **Management**: Similar to immediate deficit, MRI to differentiate **Neurological Recovery:** - **Incomplete Deficits**: 50-70% significant recovery - **Complete Deficits**: Poor prognosis (less than 20% recovery) - **Nerve Root Injuries**: Better prognosis than cord injuries **Wound Complications:** - **Hematoma/Seroma**: Aspiration vs surgical drainage - **Superficial Infection**: Antibiotics, local wound care - **Deep Infection**: Irrigation and debridement, retain hardware if early (less than 3 months) **Medical Complications:** - **DVT/PE**: Mechanical prophylaxis POD 0, chemical POD 1 (after drain removal) - **Ileus**: Early mobilization, minimize opioids, NG tube if severe - **Pneumonia**: Incentive spirometry, early mobilization, respiratory therapy - **Delirium**: Especially age greater than 65, minimize opioids and benzos, reorient ### Surveillance and Follow-Up **Early Follow-Up (First 3 Months):** - **2 Weeks**: Wound check, staple removal, neurological exam - **6 Weeks**: Radiographs (AP/Lateral standing), advance PT, pain assessment - **12 Weeks**: Radiographs, discontinue brace if appropriate, functional assessment **Late Follow-Up (3 Months to 2 Years):** - **6 Months**: Radiographs, CT if fusion concern, return to light activities - **12 Months**: Radiographs and CT to confirm fusion, return to full activities - **24 Months**: Final radiographs, assess for adjacent segment degeneration **Radiographic Assessment:** - **Immediate Postop**: Confirm correction achieved, hardware position - **6 Weeks**: Assess for early hardware failure (screw loosening, rod fracture) - **12 Weeks**: Look for loss of correction - **12 Months**: CT to confirm fusion (greater than 50% bridging bone) **Functional Outcome Measures:** - **ODI (Oswestry Disability Index)**: Baseline, 6 months, 12 months - **SRS-22**: Spine-specific quality of life - **VAS Pain Score**: Track pain improvement - **Walking Distance**: Objective functional measure ### Neurological Complications **Risk Factors for Neurological Injury:** - Revision osteotomy at same level (epidural scarring) - Thoracic location (spinal cord present) - Excessive correction (greater than 40 degrees PSO, greater than 60 degrees VCR) - Osteoporosis (vertebral body fracture during closure) - Vascular disease (cord ischemia) **Neuromonitoring:** - **SSEPs (Somatosensory Evoked Potentials)**: Monitor dorsal column - Alert: Greater than 50% amplitude decrease or greater than 10% latency increase - Sensitivity: 75-85% for sensory deficits - **MEPs (Motor Evoked Potentials)**: Monitor corticospinal tract - Alert: Greater than 50% amplitude decrease - Sensitivity: 85-95% for motor deficits (more reliable than SSEPs) - **Triggered EMG**: Pedicle screw placement, nerve root monitoring - **Continuous Free-Running EMG**: Nerve root irritation during dissection **Response to Neuromonitoring Changes:** 1. **Notify surgeon immediately** 2. **Augment blood pressure** (MAP to 90-100 mmHg) 3. **Release recent manipulation** (stop compression, reduce correction) 4. **Reassess signals** (wait 10-15 minutes) 5. **Wake-up test if signals do not return** 6. **Accept less correction if needed** (neurological preservation paramount) ### Vascular Complications **Major Vascular Injury (Rare, Less than 1%):** - **Great Vessels**: Aorta, IVC (during anterior VCR exposure) - **Iliac Vessels**: L4-L5 PSO or VCR - **Segmental Arteries**: Ligated during PSO/VCR (usually tolerated) **Prevention:** - Blunt dissection laterally (protect vessels) - Vascular surgery standby for high-risk cases - Avoid anterior cortex violation until final closure **Management:** - Immediate vascular surgery consultation - Direct pressure, hemostatic agents - Repair or graft if major vessel injured - Massive transfusion protocol **Artery of Adamkiewicz Injury:** - Anterior spinal artery thrombosis → paraplegia - Prevention: Maintain MAP greater than 85, avoid excessive hypotension - No effective treatment once injury occurs (devastating complication) ### Mechanical Complications **Rod Fracture:** - Incidence: 5-10% at 2 years (higher with PSO/VCR) - Risk Factors: Single rods, small diameter (5.5mm), pseudarthrosis - Prevention: Dual rods, 6.35mm diameter, achieve solid fusion - Management: Revision if symptomatic or pseudarthrosis present **Screw Loosening/Pullout:** - Incidence: 3-5% (higher in osteoporosis) - Risk Factors: Osteoporosis, inadequate screw purchase, excessive stress - Prevention: Cement augmentation if T-score less than -2.5, bicortical screws - Management: Revision with longer/larger screws or cement augmentation **Proximal Junctional Kyphosis (PJK):** - Incidence: 20-40% after PSO/VCR - Risk Factors: Osteoporosis, overcorrection, UIV at inflection point - Prevention: Prophylactic vertebroplasty at UIV, gradual lordosis transition - Management: Observation if asymptomatic, revision if symptomatic/severe **Pseudarthrosis:** - Incidence: 10-20% at 2 years - Risk Factors: Smoking, diabetes, osteoporosis, inadequate biologics - Prevention: Smoking cessation, autograft + BMP, teriparatide - Management: Revision if symptomatic or hardware failure ### Expected Outcomes by Osteotomy Type **Smith-Petersen Osteotomy:** - **Correction Achieved**: 90-95% achieve planned correction (10 degrees per level) - **Pain Relief**: 70-80% significant improvement - **Fusion Rate**: 90-95% (low-stress osteotomy) - **Complication Rate**: 15-25% (mostly minor) - **Patient Satisfaction**: 75-85% **Pedicle Subtraction Osteotomy:** - **Correction Achieved**: 80-90% achieve planned correction (30-40 degrees) - **Sagittal Balance**: SVA less than 50mm achieved in 85-90% - **Pain Relief**: 65-75% significant improvement - **Functional Improvement**: 60-70% meaningful ODI improvement - **Fusion Rate**: 85-90% - **Complication Rate**: 40-50% (major complications 10-15%) - **Patient Satisfaction**: 65-75% **Vertebral Column Resection:** - **Correction Achieved**: 75-85% achieve planned correction (50-70 degrees) - **Pain Relief**: 60-70% significant improvement - **Functional Improvement**: 55-65% meaningful improvement - **Fusion Rate**: 75-85% - **Complication Rate**: 50-70% (major complications 20-30%) - **Patient Satisfaction**: 55-65% ### Predictors of Success **Positive Predictors:** - Appropriate osteotomy selection (match to deformity) - Achievement of solid fusion - Restoration of sagittal balance (SVA less than 50mm, PI-LL within 10 degrees) - Good bone quality (T-score greater than -2.0) - Age less than 65 years - Non-smoker - Single osteotomy (vs multiple or revision) - Realistic expectations **Negative Predictors:** - Severe osteoporosis (T-score less than -3.0) - Active smoking - Multiple comorbidities (Charlson index greater than 3) - Revision osteotomy at same level - Chronic opioid use preoperatively - Poor nutritional status (albumin less than 3.5) - Unrealistic expectations (expect complete cure) ### Long-Term Outcomes **5-Year Outcomes:** - **Maintained Correction**: 75-85% maintain SVA less than 50mm - **Fusion Rate**: 85-95% if solid at 1 year - **Adjacent Segment Disease**: 20-30% develop symptomatic ASD - **Reoperation Rate**: 15-25% - PJK (most common reason): 8-12% - Pseudarthrosis: 3-5% - Rod fracture: 3-5% - Infection: 2-3% **10-Year Outcomes:** - Limited data due to recent adoption of techniques - Cumulative reoperation rate: 25-35% - Patient satisfaction maintained: 60-70% of those initially satisfied - Adjacent segment degeneration: cumulative 35-45% **Q: How much sagittal correction does each type of spinal osteotomy provide?** A: **SPO/Ponte osteotomy** (Grade 1-2): ~10° per level (posterior column only). **PSO** (pedicle subtraction osteotomy, Grade 3): **25-35° per level** (all three columns). **VCR** (vertebral column resection, Grade 4-6): **greater than 40° per level**, unlimited correction. Choose based on correction needed and deformity type. **Q: What is the key anatomical difference between SPO and PSO?** A: **SPO (Smith-Petersen)**: Resects posterior elements only; correction through **disc space** opening anteriorly (hinges on ALL). Requires mobile anterior column. **PSO**: Resects pedicles and wedge of vertebral body; closure is **bone-on-bone**, no disc involvement. PSO preferred when anterior column fused or osteoporotic. **Q: What is the major complication risk difference between PSO and VCR?** A: **PSO** blood loss: 1.5-3L average; **VCR** blood loss: 3-5L average. **Neurological risk**: PSO ~5-10%, VCR ~15-20%. VCR requires circumferential decompression with temporary spinal cord instability. Both require **neuromonitoring**. VCR reserved for severe rigid deformities, tumors, or failed prior surgery. **Q: What is the Schwab classification of spinal osteotomies?** A: **Grade 1**: Partial facetectomy. **Grade 2**: Complete facetectomy (Ponte). **Grade 3**: PSO through single vertebra. **Grade 4**: VCR single vertebra. **Grade 5**: VCR two adjacent vertebrae. **Grade 6**: VCR three+ vertebrae. Higher grades = more correction possible but higher morbidity. Guides surgical planning. **Q: What are the indications for pedicle subtraction osteotomy (PSO)?** A: **Fixed sagittal imbalance** greater than 10-15cm, **ankylosed spine** (AS, DISH), **failed prior fusion** with kyphosis, **iatrogenic flatback syndrome**. Performed at **apex of deformity** or L3 (L2-L4 acceptable). Contraindicated at previously instrumented/fused levels without hardware removal. Goal: Restore SVA to within 5cm of sacrum. ### Australian Epidemiology and Management **Complex Spine Surgery in Australia:** - Spinal osteotomy procedures concentrated at major tertiary centres (Royal North Shore, St Vincent's Melbourne, Royal Adelaide, Princess Alexandra Brisbane, Royal Perth) - Fellowship-trained complex spine surgeons perform majority of PSO/VCR procedures - Australian Spine Society (AOSS) maintains registry for deformity surgery outcomes - Multidisciplinary spine deformity clinics at major centres coordinate complex cases **RACS Orthopaedic Training Relevance:** - Spinal osteotomies are high-yield FRACS Orthopaedic examination topics - Key exam focus: Schwab classification, osteotomy selection based on deformity, neuromonitoring principles - Viva scenarios commonly test response to neuromonitoring changes and patient selection - Understanding of biomechanical principles (correction potential, axis of rotation) is examined **Private Health Insurance:** - Complex spine surgery requires prosthesis billing (rods, screws, cages) - Prostheses List items covered under hospital insurance - Extended ICU and hospital stay typical for PSO/VCR (7-14 days) **AHPRA and TGA Considerations:** - Spinal implants (pedicle screws, rods, cages) require TGA registration - BMP (bone morphogenetic protein) usage for fusion augmentation is off-label in spine - Informed consent must address specific TGA-registered implant details **Training Pathway:** - AOSS Complex Spine Surgery Fellowship (1-2 years post-FRACS) - International fellowship options (USA scoliosis centres, AOSpine fellowship) - Minimum 50 PSO cases before independent practice recommended **Neuromonitoring Services:** - Dedicated intraoperative neurophysiology technicians required - Available at all major Australian centres performing complex osteotomies - SSEP and MEP monitoring standard of care for PSO/VCR - **Adult Deformity Surgery**: Primary indication for osteotomies - **Revision Deformity Surgery**: Often requires PSO or VCR for correction - **Proximal Junctional Kyphosis**: Common complication after osteotomy - **Spinal Cord Monitoring**: Essential for safe osteotomy execution - **Flatback Deformity**: Most common indication for PSO - **Ankylosing Spondylitis**: Classic indication for SPO - **Sagittal Balance**: Understanding parameters guides osteotomy selection - **Rod Fractures**: Mechanical complication after osteotomy