Congenital Kyphosis

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.

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).

A sharp, rigid, angular kyphosis (gibbus) in a child is congenital until proven otherwise, but several other causes produce a kyphotic spine and must be distinguished — the management and neurological risk differ sharply.

Neurological Complications

Surgical Complications

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.

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

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

Natural History by Type

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

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

Global epidemiology. Congenital kyphosis is rare and substantially less common than congenital scoliosis. It affects males and females roughly equally, the apex lies at the thoracolumbar junction (T10-L1) in about two-thirds of cases, and roughly 60 percent of patients have at least one associated anomaly within the VACTERL spectrum. There is no high-quality population registry for congenital kyphosis; the evidence base is built from single-centre series, so practice is consensus-driven rather than registry-driven.

Side-by-side guidance. No single society publishes a dedicated congenital-kyphosis pathway, so principles are drawn across bodies:

The genuine point of difference between regions is not whether to operate but which technique (in-situ vs instrumented posterior fusion vs anterior release vs VCR) and how early, driven by deformity rigidity, magnitude and neurological status rather than geography.

High- vs limited-resource practice variation.

• Well-resourced centres: routine multimodal neuromonitoring, 3D-CT planning, single-stage posterior VCR, cell salvage and paediatric intensive care — enabling aggressive correction of severe deformity at acceptable risk.
• Limited-resource settings: later presentation with established neurology and larger curves is common; monitoring may be unavailable, pushing surgeons toward safer in-situ posterior fusion, the wake-up test, and staged rather than single-stage correction. Early prophylactic posterior fusion of a small progressive curve is the highest-value, lowest-cost intervention and should be prioritised wherever follow-up is reliable.

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.

The topic's central recommendation - early posterior fusion, even at age 1-2 - is in direct tension with a complication it names but never develops: the crankshaft phenomenon (listed under complications as "anterior growth continues despite posterior fusion in young children. May need anterior fusion," and again in the controversies as a reason to hesitate). Because we deliberately fuse the very youngest, skeletally immature spines here, this is the key trade-off to understand.

These are exactly the patients in whom congenital kyphosis pushes us to fuse early - which is why crankshaft is a real, not theoretical, concern here.

How it is mitigated:

For congenital kyphosis the calculus differs from idiopathic early-onset scoliosis: the lethal endpoint is paraplegia, not trunk-height loss, so arresting a progressive Type I curve takes priority and crankshaft is an accepted, managed risk rather than a reason to delay. (General growth-modulating and growing-rod strategies for non-congenital early-onset deformity are covered in the early-onset-scoliosis topic.)

The guidelines table and the Kamerlink evidence both make multimodal SSEP + MEP monitoring the standard of care and refer to a "documented stop/checklist protocol for monitoring loss," and VCR is repeatedly said to "require neuromonitoring" - but the topic never explains what is monitored or what you actually do when the signal drops. This is core viva material, and the stakes are uniquely high here because the cord is draped over the kyphotic apex and supplied by a watershed anterior spinal artery, so correction can both kink and devascularise it.

What the two modalities watch (and why you need both):

• SSEP monitors the dorsal columns (posterior cord) - good for global cord integrity but can stay normal while the motor tracts are injured.
• MEP / transcranial motor-evoked potentials monitor the corticospinal (motor) tracts in the anterolateral cord - the territory of the anterior spinal artery, which is exactly what is at risk in anterior-apex kyphosis correction. MEP is the more sensitive alarm for the ischaemic anterior cord that kyphosis surgery threatens, which is why SSEP alone is insufficient.

The structured response to a true alert (a real, reproducible loss - not artefact): act in parallel, do not "watch and wait."

The goal is to act before a transient monitoring change becomes a fixed deficit - in large series most monitoring changes occur before or during the correction and, if addressed promptly, do not result in permanent injury.

The literature is entirely retrospective Level IV, so several management questions remain genuinely unsettled and are favourite viva discussion points.

• Timing of fusion in the very young. Early posterior fusion (even age 1-2) arrests progression and prevents paraplegia, but sacrifices growth and risks the crankshaft phenomenon. The unresolved trade-off is how small a curve justifies fusing a toddler's spine — most accept fusing a documented progressive Type I, but the threshold is judgement, not evidence.
• In-situ vs instrumented posterior fusion. Modern pedicle-screw constructs allow correction and shortening, but instrumentation in tiny pedicles carries pull-out and neurological risk. Some still advocate simple in-situ posterior fusion to halt progression in the youngest patients.
• Need for anterior surgery. Combined anterior/posterior fusion historically reduced pseudarthrosis and addressed the crankshaft, but posterior-only osteotomy/VCR now achieves correction without thoracotomy morbidity in many hands. Whether anterior support still adds value in severe rigid curves is debated.
• VCR versus lesser osteotomy. VCR gives the most powerful correction but carries roughly a 10-20 percent neurological complication risk and high blood loss; the boundary at which a PSO or anterior release is "enough" is not defined by trials.
• Decompression for established deficit. When there is cord compression with T2 signal change, the relative roles of anterior decompression, posterior shortening and the achievable neurological recovery are uncertain, and prognosis with established myelomalacia is guarded.

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.