Congenital Kyphosis
The Neurological Emergency
Winter Classification
Critical Must-Knows
- Type I is CRITICAL: Failure of anterior formation leads to progressive kyphosis and cord compression.
- Neurology is the Priority: Unlike scoliosis, paraplegia is a real and common threat.
- Early Fusion is Acceptable: Unlike EOS, early fusion is often the safest option.
- Bracing is Ineffective: Rigid deformity does not respond to bracing.
- MRI Mandatory: Assess cord compression and intraspinal anomalies.
Examiner's Pearls
- "Look for cutaneous stigmata (hairy patch)
- "Full neurological exam is critical
- "Assess for associated VACTERL anomalies
- "Check for scoliosis (often coexists)
Clinical Imaging
Imaging Gallery
Paralysis Risk
Orthopaedic Emergency
Urgent: Natural history of Type I is progressive paraplegia.
The Danger Zone
T10-L2: Apex often here, putting cord at max risk.
Rapid Deterioration
Growth Spurts: Even normal infants can deteriorate rapidly.
Treatment
Early Fusion: Safest option, even at age 1-2. Better than paralysis.
Congenital Kyphosis vs Congenital Scoliosis
| Feature | Congenital Kyphosis | Congenital Scoliosis |
|---|---|---|
| HIGH (25-50%) | Low (unless severe) | |
| Ineffective | Occasionally useful | |
| Early Fusion | Observation / Growing Rods | |
| Less important than neurology | Critical (TIS prevention) |
Winter Classification
Memory Hook:Type I is the WORST. Think 'I' for 'Ischemic cord'.
Associated Anomalies (VACTERL)
Memory Hook:Screen for ALL these before surgery.
Red Flags for Cord Compression
Memory Hook:CORD = Check the Cord.
Overview/Epidemiology
Congenital Kyphosis is a sagittal plane deformity caused by abnormal vertebral development (failure of formation or segmentation of the anterior vertebral body).
- Epidemiology:
- Rare (much less common than congenital scoliosis).
- Often occurs at the thoracolumbar junction (T10-L2).
- Male = Female.
- Natural History:
- Type I: Relentless progression (5-10 degrees/year). High paraplegia risk.
- Type II: Slower progression. Lower but still significant paraplegia risk.
- Type III: Unpredictable. Behaves like whichever component dominates.
Pathophysiology and Spinal Development
Failure of Formation (Type I)
- The anterior part of one or more vertebral bodies fails to form.
- This creates a posteriorly based "wedge" vertebra or complete aplasia of the body.
- The spine is forced into kyphosis at that level.
- Cord Risk: The spinal cord is stretched over the apex of the deformity. As kyphosis progresses, the cord is progressively compressed against the posterior body.
Failure of Segmentation (Type II)
- An anterior unsegmented bar forms (like a stalactite of bone connecting adjacent vertebrae anteriorly).
- Posterior growth continues normally, but anterior growth is tethered.
- Result: Progressive kyphosis (usually slower than Type I).
Classification Systems
Winter Classification (1973)
The standard classification.
Type I: Failure of Formation
- Partial aplasia of anterior body (Wedge vertebra).
- Complete aplasia of anterior body (Aplastic vertebra).
- Worst prognosis. High progression and neurology risk.
Type II: Failure of Segmentation
- Anterior unsegmented bar.
- Slower progression than Type I.
Type III: Mixed
- Combination of Type I and II defects.
Clinical Assessment
History:
- Birth Hx: Antenatal diagnosis? VACTERL screening?
- Development: Walking? Continence? (Suggests cord function).
- Progression: Any worsening noted by parents?
Physical Exam:
- Neurology (CRITICAL):
- Full upper and lower limb exam.
- Tone: Spasticity? Clonus?
- Reflexes: Hyperreflexia?
- Gait: Ataxic? Scissoring?
- Spine:
- Sharp angular kyphosis (Gibbus deformity)?
- Assess flexibility (usually rigid).
- Cutaneous Stigmata: Hairy patch, dimple (concurrent spinal dysraphism).
Investigations
Imaging:
- X-ray (PA and Lateral Whole Spine): Identify the anomaly. Measure kyphosis.
- CT Scan (3D Reconstruction): Essential for surgical planning. Defines the bony anatomy.
MRI:
- Mandatory before surgery.
- Assess cord compression (Myelomalacia? Signal change?).
- Rule out intraspinal anomalies (Diastematomyelia, Tethered Cord, Syrinx).
Systemic Screening (VACTERL):
- Echocardiogram.
- Renal Ultrasound.
- GI / Anorectal exam.
Management Algorithm
Observation / Bracing
- Bracing: Ineffective. The deformity is rigid.
- Observation: May be considered in mild Type II with no progression, but rare.
- Casting: Not used (unlike scoliosis).
Surgical Techniques
Posterior Fusion In Situ / With Instrumentation
Goal: Stop progression. Prevent paraplegia. Technique:
- Posterior midline approach.
- Expose the levels to be fused (usually 2 levels above and below the apex).
- Pedicle screws (if pedicle anatomy allows) or laminar hooks.
- Apply compression across the kyphotic apex.
- Decorticate and bone graft. Outcome: Halts progression. Limited correction in young children.
Deep Dive: Posterior Shortening
The Concept Unlike scoliosis (where we lengthen the concavity), kyphosis correction requires shortening the convexity (posterior spine).
Cantilever Technique
- Anchor screws at proximal and distal ends.
- Pre-bent rod is contoured to the desired lordosis.
- Rod is "cantilevered" into the screws, progressively reducing the kyphosis.
- Risk of screw pullout (especially proximally). Requires strong anchor constructs.
Compression Technique
- In situ rod placement.
- In situ compressor applied across the kyphotic apex.
- Safer but less powerful correction.
Complications
Neurological Complications
| Complication | Incidence | Risk Factors | Prevention and Management |
|---|---|---|---|
| Spinal Cord Injury | 10-20% (VCR) | Severe deformity, rapid correction | Neuromonitoring, staged correction, wake-up test |
| Nerve Root Injury | 5-10% | Osteotomy sites | Meticulous technique, decompression |
| Delayed Neurological Deterioration | Rare | Post-op haematoma, swelling | Close monitoring first 48 hours |
| Paraplegia (Untreated) | Nearly 100% Type I | Progressive stenosis | Early surgical intervention |
Surgical Complications
| Complication | Rate | Prevention | Treatment |
|---|---|---|---|
| Pseudarthrosis | 10-30% | Combined anterior/posterior fusion | Revision with bone graft augmentation |
| Proximal Junctional Kyphosis | 15-30% | Avoid stopping at apex, adequate proximal anchors | Extension of fusion if symptomatic |
| Hardware Failure | 5-15% | Strong constructs, dual rods, cross-links | Revision and reinforcement |
| Wound Infection | 3-10% | Muscle coverage, meticulous technique | Debridement, antibiotics, VAC therapy |
| Dural Tears | 5-8% | Careful dissection around vertebrae | Primary repair, fibrin sealant |
Long-term Considerations
- Crankshaft Phenomenon: Anterior growth continues despite posterior fusion in young children. May need anterior fusion.
- Adding-on: Curve progression above or below fusion. Monitor with serial radiographs.
- Chronic Pain: May develop at fusion ends. Physiotherapy and pain management.
- Functional Limitations: Short trunk, reduced spinal mobility. Occupational therapy for adaptation.
Postoperative Care
Immediate Postoperative Period
- ICU Care: 24-48 hours for complex cases (VCR, severe deformity)
- Neurological Monitoring: Hourly checks for first 24 hours, then 4-hourly
- Pain Management: Multimodal analgesia, PCA if appropriate for age
- DVT Prophylaxis: Mechanical and pharmacological as appropriate
Rehabilitation Timeline
| Phase | Duration | Focus |
|---|---|---|
| Acute | 0-2 weeks | Mobilisation, wound care, pain control |
| Subacute | 2-6 weeks | Gentle ROM, core stability, bracing compliance |
| Recovery | 6 weeks - 3 months | Progressive strengthening, return to activities |
| Long-term | 3-12 months | Sports restriction, fusion consolidation |
Bracing Protocol
- TLSO: Custom-molded for 3-6 months post-op
- Full-time wear: Except for bathing initially
- Weaning: Gradual, guided by imaging and clinical stability
- Compliance: Essential for fusion success
Follow-up Schedule
- 2 weeks: Wound check, neurological examination
- 6 weeks: Radiograph, assess healing
- 3 months: CT if fusion concerns
- 6 months: Clinical and radiographic review
- Annually: Long-term surveillance during growth
Outcomes/Prognosis
Natural History by Type
| Type | Untreated Progression | Expected Outcome |
|---|---|---|
| Type I (Failure of Formation) | Inevitable progression greater than 100 degrees | Paraplegia if untreated |
| Type II (Failure of Segmentation) | Variable, often less severe | May remain stable or progress |
| Type III (Mixed) | Unpredictable | Depends on dominant component |
Surgical Outcomes
- Neurological Preservation: Greater than 90% with early intervention
- Curve Correction: 50-70% correction achievable
- Fusion Rate: Greater than 90% with combined approach
- Patient Satisfaction: High when cosmesis improved
Factors Affecting Prognosis
| Factor | Better Prognosis | Worse Prognosis |
|---|---|---|
| Timing | Early intervention | Delayed surgery with neurological deficit |
| Type | Type II | Type I (especially posterior bar) |
| Age at Surgery | Young (before puberty) | After growth complete |
| Associated Anomalies | Isolated | Multiple congenital anomalies |
Long-term Function
- Activities of Daily Living: Most patients independent
- Sports Participation: Low-impact activities after fusion consolidation
- Career: Wide range possible, avoid heavy labour
- Quality of Life: Generally good with successful treatment
Evidence Base
- Defined the Winter Classification (Types I, II, III)
- Type I has the worst prognosis
- Early posterior fusion recommended
- Natural history of congenital kyphosis
- Type I progresses 5-10 degrees per year on average
- Neurological deficit occurred in 25% of Type I patients
- Posterior osteotomy for congenital kyphosis
- Mean correction of 45 degrees
- Neurological improvement in most patients with preoperative deficits
- Posterior VCR for severe congenital kyphosis
- Good correction achieved
- Complication rate of 15%
- Review of spinal cord damage in congenital kyphosis
- Direct mechanical compression and vascular ischemia contribute
- MRI signal change correlates with irreversible damage
Viva Scenarios
Practice these scenarios to excel in your viva examination
The Infant with a Gibbus
"1-year-old infant. Angular kyphosis at T12. MRI shows no cord compression. Neurologically normal."
This is likely a Type I Congenital Kyphosis (Failure of Formation). Even though the child is neurologically normal now, the natural history is progressive kyphosis and eventual cord compression. I would recommend **early posterior spinal fusion** to arrest progression. Waiting is dangerous. CT scan to plan instrumentation. VACTERL screening.
Late Presentation with Paraparesis
"10-year-old presents with bilateral lower limb weakness. Kyphosis of 80 degrees at T11. MRI shows cord compression and T2 signal change."
This is an **emergency**. The T2 signal change suggests cord edema or myelomalacia, indicating established injury. The goal is to decompress the cord and stabilize the spine. I would perform an **anterior decompression** (corpectomy) with cage reconstruction, followed by **posterior instrumented fusion**. Alternatively, a posterior VCR if safe. The neurological prognosis is guarded due to existing signal change.
VACTERL Association
"Neonate with imperforate anus and radial club hand. Spine X-ray shows a vertebral anomaly at T10."
This is VACTERL association. The spine anomaly should be characterized with MRI and CT. Likely congenital scoliosis or kyphosis. However, the **immediate priority** is the anorectal and cardiac anomalies (life-threatening). Orthopaedic management of the spine can be staged after neonatal surgery. The radial club hand is a functional issue for later. I would coordinate with Neonatology, Cardiology, and Paediatric Surgery.
MCQ Practice Points
Classification MCQ
Q: Which type of congenital kyphosis has the worst prognosis? A: Type I (Failure of Formation). It progresses the fastest and has the highest neurological risk.
Pathomechanics MCQ
Q: What is the mechanism of cord injury in congenital kyphosis? A: Mechanical compression of the cord over the kyphotic apex and vascular ischemia of the anterior spinal artery territory.
Treatment MCQ
Q: Is bracing effective for congenital kyphosis? A: No. The deformity is rigid. Bracing does not alter progression.
Anatomy MCQ
Q: What is the most common level for congenital kyphosis? A: Thoracolumbar junction (T10-L2). This puts the conus medullaris at risk.
Prognosis MCQ
Q: What is the neurological risk with Type I congenital kyphosis? A: 25-50% risk of paraplegia if untreated due to progressive cord compression.
Investigations MCQ
Q: What imaging is mandatory before surgery for congenital kyphosis? A: MRI to assess cord compression, intraspinal anomalies (tethered cord, diastematomyelia).
Australian Context
- Referral: Urgent referral to a Paediatric Spine centre for any congenital kyphosis.
- Neuromonitoring: Intraoperative neuromonitoring (SSEP, MEP) is standard in all Australian tertiary centres.
- Multidisciplinary: VACTERL screening involves Cardiology, Nephrology, and Paediatric Surgery.
CONGENITAL KYPHOSIS
High-Yield Exam Summary
CLASSIFICATION
- •Type I (Formation)
- •Type II (Segmentation)
- •Type III (Mixed)
- •Type I is WORST
RISK
- •Paraplegia 25-50%
- •Progression Certain
- •Bracing Fails
- •Early Fusion Indicated
WORKUP
- •MRI Cord
- •CT Anatomy
- •Echo (VACTERL)
- •Renal US
SURGERY
- •Posterior Fusion
- •Anterior Release
- •VCR (Severe)
- •Neuromonitoring
Deep Dive: MRI Cord Signal
T2 Hyperintensity at the Apex
- Indicates cord edema, gliosis, or myelomalacia.
- Edema: Potentially reversible if decompressed urgently.
- Myelomalacia: Established damage. Irreversible.
Clinical Correlation
- Patients with MRI signal change and neurological deficit have a worse prognosis even after surgery.
- The goal is to intervene BEFORE signal change develops.