THREE-COLUMN OSTEOTOMIES
Complex Deformity Correction | Pedicle Subtraction | Vertebral Column Resection
Schwab Classification of Spinal Osteotomies
Critical Must-Knows
- PSO (Grade 3) achieves 30-40° correction at single level through posterior closing wedge
- VCR (Grade 4-5) allows multiplanar correction for severe rigid deformities
- Neuromonitoring mandatory - wake-up test if signal changes occur
- Blood loss can exceed 2000mL - cell saver and preoperative autologous donation essential
- Biomechanical hinge is anterior column - protect at all costs during PSO
Examiner's Pearls
- "PSO apex is at posterior cortex - cutting too anterior risks anterior column failure
- "VCR requires anterior AND posterior support with mesh cage and rod construct
- "Schwab Grade 3 (PSO) is most common three-column osteotomy for sagittal imbalance
- "Complication rate higher with VCR (30%) versus PSO (20%) but greater correction achieved
Critical Three-Column Osteotomy Exam Points
Biomechanical Principles
PSO closes posteriorly, hinges anteriorly. Anterior column is tension band - must remain intact. Greenstick fracture of anterior cortex allows controlled closure. Breaking anterior column risks catastrophic failure requiring anterior reconstruction.
Neurological Risk Stratification
Highest risk: VCR at thoracic levels (1-10% deficit). Cord ischemia from canal compromise or vascular injury. PSO safer (1-2% risk) but still requires SSEP/MEP monitoring. Immediate wake-up test if signal loss.
Bleeding Complications
Expect 1500-3000mL blood loss. Epidural venous plexus bleeding during posterior decompression. Cell saver mandatory. Tranexamic acid reduces loss by 30%. Type and cross 4-6 units preoperatively.
Deformity Assessment
Sagittal Vertical Axis (SVA) drives indication. SVA greater than 5cm indicates sagittal imbalance. Pelvic incidence minus lumbar lordosis (PI-LL) mismatch greater than 10° requires correction. PSO at L2-L3 most effective for global sagittal balance.
At a Glance
Three-column osteotomies are powerful spinal deformity correction techniques classified by the Schwab system (Grades 1-6). Pedicle subtraction osteotomy (PSO, Grade 3) achieves 30-40° correction per level by creating a posterior closing wedge that hinges on the intact anterior column—this tension band must be preserved to avoid catastrophic failure. Vertebral column resection (VCR, Grade 4-6) enables 60-90° multiplanar correction for severe rigid deformities. Complication rates are significant (PSO 20%, VCR 30%) with neurological deficit risk of 1-5%; neuromonitoring (SSEP/MEP) is mandatory with immediate wake-up test if signals change. Blood loss typically exceeds 2000mL requiring cell saver and tranexamic acid.
PRECISEPSO Steps - Safe Execution
Memory Hook:Execute PSO with PRECISION - every step critical to avoid catastrophic anterior column failure or neurological injury!
SHARPVCR Indications
Memory Hook:SHARP deformities need SHARP corrections - VCR cuts through all three columns for maximum flexibility!
BLEEDSComplications of Three-Column Osteotomies
Memory Hook:Three-column osteotomies BLEED and carry major risks - prepare patient and surgical team accordingly!
Overview and Epidemiology
Three-column osteotomies represent the most powerful tools for correction of complex spinal deformity. These procedures involve resection of all three spinal columns (anterior, middle, posterior) to achieve significant sagittal and coronal plane realignment. The two main types are pedicle subtraction osteotomy (PSO, Schwab Grade 3) and vertebral column resection (VCR, Schwab Grade 4-6).
Why Three-Column Osteotomies Matter
Adult spinal deformity with sagittal imbalance causes progressive disability and pain. Sagittal Vertical Axis (SVA) greater than 5cm and PI-LL mismatch greater than 10° predict poor quality of life. Three-column osteotomies restore sagittal balance when less invasive procedures cannot achieve adequate correction. PSO is the workhorse for fixed sagittal deformity, while VCR is reserved for the most severe rigid curves or tumor resection.
Indications for PSO
- Fixed sagittal imbalance with SVA greater than 5cm
- Pelvic incidence minus lumbar lordosis (PI-LL) mismatch greater than 10°
- Ankylosing spondylitis with severe kyphosis
- Post-traumatic kyphosis
- Flatback syndrome after prior fusion
Indications for VCR
- Severe rigid deformity greater than 70° unresponsive to PSO
- Congenital hemivertebra
- Sharp angular kyphosis requiring multiplanar correction
- Spinal tumor requiring en bloc resection
- Revision with junctional kyphosis
Pathophysiology
Anterior Column Preservation in PSO
The anterior longitudinal ligament and anterior vertebral cortex form the biomechanical hinge during PSO closure. Greenstick fracture of the anterior cortex allows controlled closure of the posterior wedge. Complete fracture through the anterior column creates instability requiring anterior column reconstruction with cage support. Fluoroscopic monitoring during closure is mandatory to detect anterior column failure.
Three Spinal Columns: Anatomy and Resection Strategy
| Column | Anatomical Structures | Resection in PSO | Resection in VCR |
|---|---|---|---|
| Anterior | Anterior longitudinal ligament, anterior vertebral body, anterior annulus | PRESERVED as hinge (greenstick fracture) | Complete resection, replaced with mesh cage |
| Middle | Posterior vertebral body, posterior annulus, posterior longitudinal ligament | Complete resection within wedge | Complete resection |
| Posterior | Pedicles, facets, lamina, ligamentum flavum, interspinous ligaments | Complete bilateral resection | Complete resection |
Vascular Anatomy at Risk
Lumbar Vessels (L1-L4)
Segmental arteries arise from aorta at posterior vertebral body. At risk during anterior cortex perforation or VCR. Injury causes massive hemorrhage. Preoperative CT angiography identifies aberrant vasculature. Vascular surgery on standby for VCR cases.
Epidural Venous Plexus
Valveless venous network within spinal canal. Major source of bleeding during decompression. Hemostasis with bipolar cautery, thrombin-soaked Gelfoam, and bone wax on bleeding bone surfaces. Cell saver recovers 30-50% of blood loss.
Classification
Schwab Spinal Osteotomy Classification
Schwab Classification (Anatomical)
| Grade | Osteotomy Type | Columns Involved | Expected Correction |
|---|---|---|---|
| Grade 1 | Partial facet resection (SPO) | Posterior only | 5-10° |
| Grade 2 | Complete facet resection (Ponte) | Posterior only | 10-15° |
| Grade 3 | Pedicle subtraction osteotomy (PSO) | All three | 30-40° |
| Grade 4 | Posterior VCR with cage | All three | 40-60° |
| Grade 5 | Complete VCR (anterior + posterior) | All three | 60-90° |
| Grade 6 | Multiple VCR | All three at multiple levels | Greater than 90° |
Clinical Application
When to Use Each Grade:
Grades 1-2 (Smith-Petersen/Ponte):
- Mobile deformities
- Ankylosing spondylitis with flexible segments
- Multiple levels can achieve cumulative correction
Grade 3 (PSO):
- Fixed sagittal imbalance
- Ankylosing spondylitis with rigid kyphosis
- Flatback syndrome
- Single level provides 30-40° correction
Grades 4-6 (VCR):
- Severe rigid deformity greater than 70°
- Congenital hemivertebra
- Sharp angular kyphosis
- Spinal tumor requiring en bloc resection
PSO is the Workhorse
Schwab Grade 3 (PSO) is the most commonly performed three-column osteotomy. It provides reliable 30-40° sagittal correction with acceptable complication rates. VCR (Grades 4-6) reserved for cases where PSO cannot achieve adequate correction.
Clinical Presentation
Preoperative Workup
Standing scoliosis radiographs (36-inch cassette) to measure global sagittal and coronal alignment. Measure Sagittal Vertical Axis (SVA), Pelvic Incidence (PI), Lumbar Lordosis (LL), and PI-LL mismatch. CT spine for bone quality assessment and pedicle anatomy. MRI if neurological symptoms or to rule out stenosis.
Cardiopulmonary clearance for patients over 60 years or with comorbidities. Autologous blood donation (2-4 units) if time permits. Nutritional optimization - albumin greater than 3.5g/dL. Smoking cessation mandatory for fusion. Osteoporosis treatment if DEXA T-score less than -2.5.
Determine osteotomy level - L2 or L3 most effective for global sagittal balance correction. Calculate correction needed - each PSO provides 30-40° lordosis. Plan instrumentation - extend 3-4 levels above and below osteotomy. Arrange neuromonitoring and wake-up test protocol.
PSO versus VCR: Decision Matrix
| Parameter | PSO (Schwab Grade 3) | VCR (Schwab Grade 4-5) |
|---|---|---|
| Correction achieved | 30-40° sagittal | 60-90° multiplanar |
| Operative time | 4-6 hours | 6-10 hours |
| Blood loss | 1500-2000mL | 2000-4000mL |
| Neurological risk | 1-2% | 5-10% |
| Approach | Posterior only | Anterior and posterior or posterior only |
| Indication | Fixed sagittal imbalance | Severe rigid deformity, tumor, hemivertebra |
Investigations and Surgical Planning
Patient Positioning
Position: Prone on radiolucent Jackson table or OSI frame Padding: All bony prominences, avoid abdominal compression (improves venous drainage) Arms: Tucked at sides or on arm boards at less than 90° abduction Neuromonitoring: SSEP and MEP electrodes placed before positioning C-arm: Position for AP and lateral lumbar imaging
Positioning Critical Points
Avoid abdominal compression to minimize epidural venous engorgement and bleeding. Ensure chest rolls or frame allow abdomen to hang free. Hip flexion reduces lumbar lordosis making posterior decompression easier. Confirm neuromonitoring baseline signals before prepping.
Exposure
Incision: Midline from upper instrumented vertebra to lower instrumented vertebra Dissection: Subperiosteal exposure of posterior elements from lamina to tips of transverse processes Levels: Expose 3-4 levels above and 3-4 levels below planned osteotomy Landmarks: Identify osteotomy level with intraoperative fluoroscopy Instrumentation: Place pedicle screws at all levels except osteotomy level (screws placed after PSO closure)
Subperiosteal dissection protects paraspinal muscles and minimizes bleeding. Use bipolar cautery liberally for hemostasis.
Management: Vertebral Column Resection (VCR)
Vertebral Column Resection Principles
Definition: Complete resection of vertebral body, pedicles, and posterior elements (all three columns) at one or more levels
Schwab Grades:
- Grade 4: Posterior VCR with posterior cage support
- Grade 5: Complete VCR with anterior and posterior support
- Grade 6: Multiple VCR
Correction: 60-90° multiplanar correction possible with VCR
VCR Technique Options
| Approach | Indication | Advantages | Disadvantages |
|---|---|---|---|
| Posterior-only VCR | Sagittal and coronal deformity | Single approach, shorter operative time | More difficult anterior reconstruction |
| Anterior-posterior VCR | Severe rigid deformity, tumor | Optimal anterior column reconstruction | Two approaches, longer operative time, higher morbidity |
| Posterior with transpsoas VCR | Lumbar deformity | Access to anterior column laterally | Learning curve, lumbar plexus risk |
VCR provides maximum correction but carries higher risk than PSO. Reserved for most severe deformities.
Complications
| Complication | Incidence | Risk Factors | Management |
|---|---|---|---|
| Neurological deficit | 1-5% | Thoracic level, cord ischemia, canal compromise during closure | Immediate wake-up test, open osteotomy if deficit confirmed, MRI to rule out hematoma |
| Massive hemorrhage | 10-20% | VCR, epidural plexus injury, segmental vessel injury | Cell saver, transfusion protocol, vascular surgery consultation if uncontrolled |
| Anterior column fracture | 5-10% of PSO | Osteoporosis, excessive closure force, thin anterior cortex | Anterior column reconstruction with cage, convert to VCR construct |
| Dural tear | 10-15% | Extensive decompression, adhesions, revision surgery | Primary repair, fibrin glue, lumbar drain if large tear, bed rest 48 hours |
| Infection | 2-8% | Prolonged operative time, blood loss, diabetes, obesity | Antibiotics, irrigation and debridement, hardware retention if stable |
| Pseudarthrosis | 10-20% | Smoking, osteoporosis, anterior column fracture, infection | Revision fusion, bone graft, anterior column support if deficient |
| Proximal junctional kyphosis | 20-30% | Osteoporosis, abrupt transition, inadequate proximal fixation | Extend fusion proximally, prophylactic vertebroplasty at UIV, tethering |
Immediate Postoperative Neurological Deficit
Postoperative neurological deficit requires emergent assessment. Obtain wake-up test in OR before emergence. If deficit present, obtain stat MRI to rule out epidural hematoma. If hematoma present, emergent decompression. If no hematoma, consider cord ischemia or intraoperative injury - supportive care and high-dose steroids (controversial). Document deficit and serial neurological exams.
Postoperative Care and Rehabilitation
Postoperative Protocol
ICU monitoring for first 24-48 hours. Hourly neurological checks for lower extremity motor and sensory function. Hemodynamic monitoring and transfusion as needed for anemia or hemodynamic instability. Drain output monitored, expect 200-500mL first 24 hours. Pain control with PCA narcotics and muscle relaxants.
Out of bed to chair on postoperative day 1 or 2 with brace. Physical therapy for ambulation with walker. TLSO brace for 3 months when out of bed. Drain removal when output less than 30mL per 8 hours. DVT prophylaxis with sequential compression devices and pharmacological prophylaxis.
Brace wear whenever out of bed. No bending, lifting, or twisting (BLT precautions). Gradual increase in ambulation distance. Wound check at 2 weeks, staples removed if healing well. Pain management transition from narcotics to non-narcotics.
Standing X-rays at 6 weeks to assess alignment and hardware position. Brace weaning if early fusion signs present. Physical therapy for core strengthening and flexibility. Return to sedentary work possible at 8-12 weeks.
Radiographs at 3, 6, and 12 months to assess fusion. Full activity after solid fusion confirmed, typically 9-12 months. Monitor for complications including proximal junctional kyphosis, pseudarthrosis, and hardware failure.
Outcomes and Prognosis
Patient-Reported Outcomes
Pain and function: Oswestry Disability Index (ODI) improves by 15-20 points on average after PSO for sagittal imbalance. Patients with severe preoperative disability benefit most. Pain scores (VAS) decrease from 7-8/10 to 3-4/10 on average.
Quality of life: SF-36 and SRS-22 scores improve significantly in physical function domains. Mental health scores less reliably improved. Patient satisfaction 70-80% at 2 years.
Radiographic correction: PSO achieves 30-40° sagittal correction and SVA improvement from 10-15cm to less than 5cm. VCR achieves 60-90° multiplanar correction. Correction maintained in 80-90% of patients without junctional failure.
Outcomes by Osteotomy Type
| Outcome Measure | PSO | VCR |
|---|---|---|
| Sagittal correction | 30-40° per level | 60-90° per level |
| Fusion rate at 1 year | 85-90% | 75-85% |
| Major complication rate | 15-20% | 25-35% |
| Neurological deficit | 1-2% | 5-10% |
| Reoperation rate at 2 years | 10-15% | 15-25% |
Predictors of Poor Outcome
Factors associated with worse outcomes include: smoking (doubles pseudarthrosis risk), osteoporosis (T-score less than -2.5), obesity (BMI greater than 35), diabetes, age over 70 years, proximal junctional kyphosis at upper instrumented vertebra, inadequate sagittal correction (residual SVA greater than 5cm), and anterior column fracture during PSO closure requiring conversion to VCR.
Evidence Base and Key Trials
PSO for Adult Spinal Deformity Correction
- Retrospective review of 77 patients undergoing PSO for fixed sagittal imbalance
- Mean correction 31° sagittal plane, SVA improved from 12cm to 3cm
- Complications in 37%: 11% neurological (all temporary except 1), 13% pseudarthrosis
- Significant improvement in pain and function scores at 2-year follow-up
Comparison of PSO versus VCR for Deformity Correction
- Retrospective comparison of 35 PSO versus 28 VCR for severe spinal deformity
- VCR achieved greater correction (48° vs 35°) but higher complication rate (39% vs 23%)
- Neurological complications higher with VCR (11% vs 3%)
- Blood loss greater with VCR (2400mL vs 1800mL)
Tranexamic Acid Reduces Blood Loss in Spinal Deformity Surgery
- RCT of 40 patients undergoing spinal deformity surgery randomized to tranexamic acid vs placebo
- Tranexamic acid reduced intraoperative blood loss by 35% (1200mL vs 1850mL)
- Transfusion requirements reduced (2.1 units vs 3.4 units)
- No difference in thromboembolic complications between groups
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Ankylosing Spondylitis with Fixed Kyphosis (Standard)
"A 45-year-old man with ankylosing spondylitis presents with severe thoracolumbar kyphosis. He cannot look horizontally and has chronic back pain. Standing radiographs show 60° thoracolumbar kyphosis, chin-brow vertical angle of 30°, and SVA of 18cm. How would you assess and manage this patient?"
Scenario 2: PSO Technique and Anterior Column Management (Challenging)
"You are performing a PSO at L3 for sagittal imbalance. You have completed the posterior column resection and are beginning to close the osteotomy. During closure, you hear a loud crack and feel sudden loss of resistance. Fluoroscopy shows discontinuity of the anterior vertebral cortex. What has happened and how do you manage it?"
Scenario 3: Postoperative Neurological Deficit Management (Critical)
"Postoperative day 0 after L2 PSO for sagittal imbalance. Patient underwent 6-hour procedure with 2500mL estimated blood loss, transfused 4 units PRBCs. In PACU, patient is somnolent but arousable. When you perform neurological exam, patient has 0/5 bilateral lower extremity motor function and sensory level at L1. Intraoperative neuromonitoring was stable throughout case. How do you assess and manage?"
MCQ Practice Points
PSO Correction Question
Q: What is the expected sagittal plane correction achieved with a single-level pedicle subtraction osteotomy (PSO)? A: 30-40° - A single-level PSO typically provides 30-40° of sagittal plane correction. This is achieved through posterior column closing wedge with anterior column acting as hinge. Multiple PSOs (e.g., two-level) can achieve 60-80° correction but with increased morbidity.
Schwab Classification Question
Q: In the Schwab classification of spinal osteotomies, what defines a Grade 3 osteotomy? A: Pedicle subtraction osteotomy (PSO) - Schwab Grade 3 is defined as pedicle and partial vertebral body resection (pedicle subtraction osteotomy). Grade 1-2 are posterior column only. Grades 4-6 involve vertebral column resection with increasing complexity.
Anterior Column Biomechanics Question
Q: What structure serves as the biomechanical hinge during PSO closure? A: Anterior longitudinal ligament and anterior vertebral cortex - The anterior column must remain intact during PSO to serve as hinge. Greenstick fracture allows controlled closure. Complete anterior column fracture requires cage placement and converts procedure to modified VCR.
Complication Rate Question
Q: What is the approximate major complication rate for PSO versus VCR? A: PSO 15-20%, VCR 25-35% - Major complications include neurological deficit, massive hemorrhage, infection, and pseudarthrosis. VCR has higher complication rate due to more extensive resection and greater destabilization during procedure.
Optimal Level Question
Q: What is the optimal level for PSO to correct global sagittal imbalance in adult spinal deformity? A: L2 or L3 - PSO at L2 or L3 provides maximum correction of sagittal vertical axis (SVA). More proximal osteotomies correct regional kyphosis but less effective for global SVA. L4 or L5 PSO increases risk of L5 nerve root injury.
Blood Loss Question
Q: What is the expected blood loss for PSO and what strategies reduce bleeding? A: 1500-2500mL for PSO - Strategies to reduce blood loss include: tranexamic acid (1g bolus + 1g infusion reduces loss by 30%), cell saver autotransfusion, preoperative autologous donation, meticulous hemostasis with bipolar cautery, avoiding abdominal compression to reduce epidural venous engorgement, and hypotensive anesthesia (controversial).
Australian Context and Medicolegal Considerations
Australian Guidelines
RACS Surgical Competence: Three-column osteotomies are advanced spine procedures requiring fellowship training in spinal deformity surgery. Not within scope of general orthopaedic practice. These procedures should only be performed at centres with appropriate multidisciplinary support including neuromonitoring, ICU capacity, and blood banking services.
Australian Registry Data
AOA National Joint Replacement Registry: Does not cover spinal procedures. No national spine registry in Australia currently.
State-based outcome tracking: Some centers participate in international spine deformity databases (e.g., SRS Morbidity and Mortality database) to track outcomes and complications.
Medicolegal Considerations for Three-Column Osteotomies
Informed consent must include:
- Neurological deficit risk (1-5% depending on procedure) with possibility of permanent paralysis
- Massive blood loss and transfusion requirements (multiple units likely)
- Infection risk (2-8%) with potential need for hardware removal
- Pseudarthrosis (10-20%) requiring revision surgery
- Proximal junctional kyphosis (20-30%) may require extension of fusion
- Medical complications: DVT/PE, cardiac events, prolonged recovery (3-6 months)
- Alternative treatments discussed including continued conservative management
Documentation requirements:
- Preoperative radiographic measurements (SVA, PI-LL mismatch) justifying surgery
- Medical optimization completed (smoking cessation, osteoporosis treatment, cardiac clearance)
- Neuromonitoring records with any signal changes documented and managed
- Operative report detailing osteotomy level, extent of resection, closure technique, any complications
- Postoperative neurological exam documented immediately in PACU and daily thereafter
Common litigation issues:
- Unrecognized neurological deficit in immediate postoperative period - ensure hourly neuro checks
- Inadequate informed consent regarding paralysis risk - document discussion of worst-case scenarios
- Anterior column fracture not recognized or inadequately managed - fluoroscopy before final closure mandatory
- Pseudarthrosis from inadequate fusion technique - ensure adequate bone graft and biologics used
Management Algorithm
THREE-COLUMN OSTEOTOMIES
High-Yield Exam Summary
Key Anatomy and Biomechanics
- •Three columns: Anterior (ALL + anterior VB), Middle (posterior VB + PLL), Posterior (pedicles + facets + lamina)
- •PSO hinge = anterior column (ALL + anterior cortex) - MUST preserve for stability
- •Greenstick anterior cortex fracture allows controlled closure - complete fracture requires cage
- •Epidural venous plexus is major bleeding source - valveless system drains to IVC
Classification and Correction
- •Schwab Grade 3 = PSO = 30-40° correction per level (posterior only)
- •Schwab Grade 4-5 = VCR = 60-90° correction (all three columns resected)
- •L2 or L3 optimal level for PSO to correct global sagittal imbalance
- •SVA greater than 5cm and PI-LL mismatch greater than 10° indicate need for three-column osteotomy
Surgical Technique Pearls
- •PSO apex at posterior cortex - cutting too far anterior risks anterior column fracture
- •Gradual closure over several minutes prevents sudden anterior column failure
- •SSEP/MEP monitoring mandatory - wake-up test if signals lost during closure
- •VCR requires temporary rod stabilization before vertebral body resection to prevent collapse
- •Mesh cage with bone graft provides anterior column support in VCR
Major Complications
- •Neurological deficit 1-5% (higher with VCR and thoracic levels) - cord ischemia or compression
- •Massive hemorrhage 1500-3000mL - epidural plexus and segmental vessels at risk
- •Anterior column fracture 5-10% of PSO - requires cage placement or conversion to VCR
- •Pseudarthrosis 10-20% - smoking, osteoporosis, anterior fracture are risk factors
- •Proximal junctional kyphosis 20-30% - extend fusion if UIV osteoporotic
Management Algorithms
- •Ankylosing spondylitis with kyphosis greater than 60° → PSO at L2/L3 for correction
- •Severe rigid deformity greater than 70° unresponsive to PSO → VCR for maximum correction
- •Anterior column fracture during closure → STOP, check neuromonitoring, place cage, convert to VCR construct
- •Postoperative neurological deficit → STAT MRI, evacuate hematoma if present emergently (within 6 hours)
Key Evidence and Outcomes
- •Bridwell 2003: PSO achieves 31° correction, SVA improves from 12cm to 3cm, but 37% complication rate
- •Lenke 2009: VCR achieves 48° vs PSO 35° but higher complications (39% vs 23%)
- •Tranexamic acid reduces blood loss by 30% (Elwatidy 2008 RCT)
- •Fusion rate 85-90% at 1 year for PSO, 75-85% for VCR
- •Patient satisfaction 70-80% at 2 years despite high complication rates