Congenital scoliosis

Definition

a spinal deformity resulting from underlying spinal malformations

Numbers

The incidence of congenital scoliosis (CS) worldwide is 0.5–1 per 1,000 births.

CS accounts for 10% of all scoliotic deformities.

It is noted that many asymptomatic cases may not be diagnosed until a radiograph is taken incidentally showing a congenital vertebral malformation (CVM).

Natural history

Progression

Depends on the

Patient's age

Age of Presentation:

Progression is fastest

Before the age of 5 AND

If deformities are evident during the first year of life, the worst prognosis must be predicted.

During the growth spurt in adolescence (ages 11–14)

Curves clinically present before the age of 10 have a poor prognosis due to their growth potential.

Location of the curve

The fastest progression to slowest

Thoracolumbar area > Midthoracic area > Upper thoracic area

Type of anomaly

Worst prognosis is the association of a unilateral bar with a contralateral hemivertebra.

For a unilateral unsegmented bar, the progression is also influenced by the extent of the bar.

Best prognosis for progression is the complete block vertebra or an incarcerated hemivertebra.

A completely segmented hemivertebra surrounded by healthy disc spaces predicts a higher rate of progression.

Has two growth plates

If there is more than one hemivertebra present, the progression rate may be faster.

A fused rib or a bar can act as a tether, thereby accelerating curve progression

Magnitude of the curve

Progression is unlikely if the curve's Cobb angle is less than or equal to 25°.

Rates

Approximately 25% of congenital curves do not progress
Roughly 25% progress mildly or slowly
50% (some say 70%) progressing quickly: Need treatment

Aetiology

Embryologic Basis

Disruptions in somitogenesis.

Somitogenesis is the process where somites, which are precursor cells for structures like the spine, develop from the paraxial mesenchyma in the trilaminar germ disk.

This crucial developmental mechanism occurs between day 20 and day 35 after conception.

Disruptions during this period lead to congenital vertebral malformations (CVM) that cause CS.

Signaling pathways involved in this process include Notch1, Wnt, FGF, and HOX.

Genetic Factors

Evidenced by a familial risk of 5–10% for CS in siblings of a patient with multiple vertebral anomalies.

Associated with numerous congenital syndromes, such as VACTERL, CHARGE, and Klippel–Feil.

Specific gene mutations proposed to be associated with CS include:

A compound inheritance of a null mutation and a hypomorphic allele of the T-box 6 (TBX6) gene, which is responsible for approximately 10% of sporadic CS.
LFNG mutations linked to CVM, which may cause a spectrum of presentations including CS and SCD (spondylocostal dysostosis).
The FBN1 gene, also associated with Marfan syndrome, identified with an autosomal dominant trait pattern for CS, potentially causing monogenic CS.

CS is also related to connective tissue disorders like Beals or Marfan syndrome, congenital muscular dystrophies, hypotonia, spinal cord malformations, and leg length discrepancy.

Environmental Factors

Evidenced by cases of monozygotic twins where one presented with CVM while the other remained asymptomatic.

Exposures thought to contribute to CS include:

Maternal Health: Gestational diabetes, prolonged febrile states, and hyperthermia exposing the fetus to high temperatures.
Toxins/Substance Exposure: Exposure to carbon monoxide from cigarette smoke, which can induce hypoxia and reactive oxygen species; hypoxia itself; and environmental toxins such as boric acid.
Medications and Intake: Treatment with antiepileptics (like valproic acid) and alcohol intake (associated with Klippel–Feil syndrome).
Nutritional Factors: Rickets, malnutrition, and vitamin deficiency.
Other Factors: Cancer and tumors of the spine.

In contrast to idiopathic scoliosis, endocrine factors have not been shown to cause CS.

Clinical feature

Physical Examination Findings

Although the Spinal deformities are present at birth (congenital), the abnormal curvature may or may not be evident on physical examination at birth.

Musculoskeletal examination

Anatomical deformities in the spine
Asymmetry in the upper and lower limbs.
Evaluating pelvic and truncal balance.

Cognitive assessment

Height and weight examination

Skin evaluation

Neurological exam.

Indicators of associated intraspinal abnormalities (like tethered cord) can sometimes be detected via neurocutaneous markers or reflex anomalies.

Thoracic Insufficiency Syndrome (TIS):

Assessment of TIS is a very important part of the evaluation, typically done using the thumb excursion test.
TIS involves the halting of lung growth due to the loss of thorax compliance and can lead to respiratory complications, especially when vertebral anomalies are associated with multiple rib fusion or absence.

Risk

Familial Risk

Siblings of a patient presenting with multiple vertebral anomalies have an estimated 5–10% risk of developing CS.

Sex/Anomaly Distribution

Intraspinal anomalies, such as syrinx or tethered cord

Sex

Preponderance in women among patients with failures of segmentation.

Associated Anomalies

Intraspinal Anomalies (Spinal Dysraphism):

These are frequently associated with CS, having a prevalence of 17–37%, even when neurological symptoms are absent.
Common abnormalities include syrinx (syringomyelia), tethered cord, and diastematomyelia.

Non-Vertebral Anomalies:

Genitourinary: CS can be associated with up to 20% of urinary tract malformations.
Musculoskeletal
Cardiac anomalies
Rib anomalies.

Classification

The vertebral abnormalities that cause congenital scoliosis (CS) are classified into groups based on two primary types of imbalance:

Scoliosis caused by longitudinal imbalance (Classification of congenital vertebral anomalies)

Usually located at the apex of the curve

Winter et al.

Type I - failure of formation

Failure of vertebral body formation

Hemivertebrae

most commonly in the thoracolumbar transition area of T11–L2

Wedge vertebrae
Butterfly vertebrae

More common
More serious

because they lead to a sharp angular kyphosis that may cause paraplegia.

Type II - failure of segmentation

Failure of vertebral segmentation

Block vertebrae
Bar (Unilateral longitudinal)

The presentation is typically in childhood with worsening kyphosis and neurologic deficits such as neurogenic bladder, lower-extremity weakness, and paresthesias.
Spinal fusion is the treatment of choice.

Type III - mixed failure of formation and segmentation

(A) Failure of formation (A1: semisegmented; A2: fully segmented; A3: wedge vertebra),
(B) failure of segmentation (B1: Bar; B2: Vertebral block)
(C) mixed deformities.

Scoliosis caused by rotational imbalance.

Spinal traction anomalies.

Spinal pushing anomalies.

Mixed anomalies.

Hemimetameric shift

An additional pattern

Results from the presence of two contralateral hemivertebras separated by one normal vertebra.

Imaging

General

Aims

Diagnosing congenital scoliosis
Classifying the specific vertebral anomalies
Monitoring the progression of the curve.

Imaging should include the whole spine.

Plain X-Rays

Anteroposterior (AP) and lateral plain X-rays are considered the gold standard modality for confirming the diagnosis, classifying the anomaly, and following up on curve progression.

They are used to measure the curve's severity using the Cobb angle:

Cobb angle measurement: lines drawn from the upper endplate of the upper vertebrae and the lower endplate of the lower vertebrae.

For patients diagnosed before they start walking, radiographs can be taken while the patient is supine.

Sequential weight-bearing radiographs every 6 months are recommended during periods of maximum spinal growth (the first 3 years of life and during puberty) to monitor curve progression.

CT

Find bony abnormalities

Can uncover up to 50% of additional abnormalities that were not visible on plain radiographs.

Determine the presence of thoracic insufficiency syndrome (TIS)

perform lung volume calculations and correlate them with lung function in patients presenting with CS.

Pre op planning for instrumentation and osteotomies

Cons

Radiation
Unable to tell curvature of spine under load.

Magnetic Resonance Imaging (MRI)

visualise the neural elements.

MRI must be performed on CS patients prior to any surgical intervention because of the high incidence of intraspinal anomalies.

Screen for

Spinal dysraphism (intraspinal anomalies) regardless of neurological symptoms.
Common intraspinal abnormalities

Syrinx (syringomyelia)
Diastematomyelia
Tethered cord
Dural bands
Cysts
Tight filum terminale

Urinary tract evaluation

Renal ultrasound
Abdominal MRI

Management

General

The ultimate goal of treatment for congenital scoliosis (CS), whether it is observation or surgery, is to prevent curve progression while achieving spinal balance.

The majority of CS cases require surgical treatment due to their progression

Non-surgical management

Observation and Monitoring

Block vertebra and wedged hemivertebra, can be managed conservatively (non-surgically).
Patients should be followed up frequently:

Every 6 months during the first 5 years of life (until age 4).
Once a year before puberty.
Every 6 months during the pubertal growth spurt.

The time of presentation is critical, as an abnormal curvature presenting at a young age is more likely to progress and requires management until after skeletal maturity.

Bracing

Primary bracing is generally discouraged for congenital curves because they are typically rigid and inflexible.
Bracing could be advised for compensatory curves.

Progression Thresholds

Progression is unlikely if the curve’s Cobb angle is less than or equal to 25°.

Surgical management

General

Surgical treatment is required in the majority of congenital scoliosis (CS) cases, as non-operative management typically fails.

Aims

To prevent curve progression
Achieve spinal balance.

Surgery should be tailored according to the

Patient's age
Magnitude of the curve (Cobb angle)
Type of malformation

Before any surgical intervention, MRI must be performed on CS patients due to the high incidence (17–37%) of associated intraspinal anomalies (e.g., tethered cord, syrinx, diastematomyelia). A tethered cord should be addressed before the scoliosis surgical correction.

Algorithm

For age: < 6


---
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---

flowchart TB
    A["Age &lt; 6"] --> B["CA &lt; 40°"] & I["CA ≥ 40°"]
    C["X-rays / 3 months"] --> D["&lt; 5° progression"] & n1@{ label: "<span style=\"background-color:\">≥ 5° progression</span>" }
    E["X-rays / 6 months"] --> F["&lt; 5° progression"]
    I --> J["Age &gt; 6 months<br>+ type II rib<br>deformity"] & L["Age &gt; 3 years<br>+ Thoracic insufficient<br>syndrome"] & M["40° &lt; CA &lt; 50°<br>+ No lordosis in the<br>region"] & O["CA ≥ 50°<br>+ Hemivertebra at<br>apex"] & Q["Fully segmented<br>vertebra<br>+ CA &lt; 70°<br>+ 10° &lt; Sagittal angle<br>&lt; 50°"]
    J --> K["VEPTR"]
    L --> K
    M --> N["Posterior in situ<br>fusion"]
    O --> P["Hemivertebra<br>resection"]
    Q --> R["Hemiepiphysiodesis<br>+/- posterior concavity<br>distraction or Growing<br>rods"]
    B --> C
    H["X-rays / 3 months"] --> I & E
    n1 --> H
    D --> E
    F --> G["X-rays / 12 months<br>until puberty"]

    n1@{ shape: rect}

For age: 6 < Age < Puberty


---
config:
  layout: dagre
---
flowchart TB
    A["6 &lt; Age &lt; Puberty"] --> B["CA &lt; 40°"] & G["CA ≥ 40°"]
    C["X-rays / 6 months"] --> D["&lt; 5° progression"] & n1@{ label: "<span style=\"background-color:\">≥ 5°</span>progression" }
    G --> H["40° &lt; CA &lt; 50°<br>+ No lordosis in the<br>region"] & J["CA &gt; 40°<br>with flexibility in the<br>anomalous segment"] & L["Congenital anomaly<br>with a long compensating<br>structural curve"] & M["Complex deformity"]
    H --> I["Posterior in situ<br>fusion"]
    J --> K["Growing rods"]
    L --> K
    M --> N["Osteotomies"]
    B --> C
    n1 --> F["X-rays / 6 months"]
    D --> E["X-rays / 12 months<br>until puberty"]

    n1@{ shape: rect}

Indications

The ideal indications for corrective or prophylactic surgery are:

The association of a unilateral bar with or without a contralateral hemivertebra.
A curve magnitude greater than 40°.
Deformities showing aggressive progression that present before the age of 5 years.

Four Primary Surgical Principles

Fusion techniques

In Situ Fusion

Indication

Prophylactic procedure at a younger age for progressive, non-deforming curves with angles less than 40° and extending along a short segment.

Procedure:

Via a posterior approach. Fusion extends one level above and below the deformity, often followed by postoperative bracing.

Correction

Correction with fusion is limited to 10°, or up to 15° with instrumentation.

Limitations

Correction can be lost over time due to pseudarthrosis and fusion mass bending.

Crankshaft Phenomenon

An isolated posterior fusion risks conserving anterior growth potential, leading to vertebral rotation progression and the crankshaft phenomenon

Particularly in patients under 10 years old or with curves over 50°.

Occurs after fixing a skeletally immature patient,

Occur secondary to continued growth of the anterior elements of the spine after solid posterior spinal fusion

An anterior release with diskectomies can provide a more solid fusion and help avoid this phenomenon.

Convex Hemiepiphysiodesis

Principle

Aims to arrest the growth potential of the convex side of the curve, allowing the concave side to continue growing and progressively correct the deformity.

Procedure:

Removes the lateral halves of the discs and fuses the vertebrae anteriorly and posteriorly.

Indications:

Ideal Patient Profile:

Fully segmented hemivertebra AND

It is perfect for a fully segmented hemivertebra anomaly but pointless for a unilateral block vertebra deformity.

Age less than 5 years AND

Only suitable when the convex side has growth potential (i.e., in patients young enough for significant correction)

Short segment (maximum five vertebrae) AND
A curve less than 70° without a major kyphotic component

Correction:

Results are unpredictable, with correction rates varying (20% to 70%).
Better results (mean correction of 35.47% of the Cobb angle) were shown in patients under 3 years old with isolated hemivertebra and curves less than 35°.

Resection techniques

Hemivertebra Excision (Resection)

Procedure

Involves the removal of the hemivertebra and adjacent discs, along with its lamina and pedicles, often for severe truncal imbalance.
It can be done via a posterior approach or a combined anterior and posterior approach.

Correction

Superior curve correction compared to in situ fusion and hemiepiphysiodesis.
Correction rates of up to 40° have been reported.

Indication

Hemivertebra, preferably in the lumbar region where the spinal cord is less susceptible to manipulation, with a curve greater than 40°.

Corrective Osteotomies (Vertebral Column Resection)

Procedure

Involves removing segments of the spine, including the vertebral body, lamina, transverse process, and ribs,
Performed via a posterior or combined approach.

Indication:

This is considered a salvage procedure for cases of rigid residual curve, neurological deficits, and failure of other conventional methods.
The procedure aims to restore truncal balance by shortening the spine and removing previous fusion masses.

Correction:

Studies show an average correction rate of 46% to 62% of the Cobb angle.

Growth-friendly techniques (distraction and instrumentation without fusion).

Growth-Friendly Techniques (Instrumentation Without Fusion)

Rationale

Designed to preserve the growth potential of the spine and gain spinal length to maintain normal pulmonary function, typically used for long segment deformities.

Procedure

Rods are attached by interconnectors, fixed above and below the curve by hooks and local fusion, and subsequently lengthened every 4–6 months until a definitive fusion is performed.
The dual rod technique is recommended over the single-rod technique for better correction and a more solid construct.

Correction

Growing rods can improve the Cobb angle by 20–50%.

Complications

However, this technique carries a high rate of implant-related complications (up to 50%) and risks growth inhibition due to auto-fusion.
Frequent procedures and repeated X-ray exposure are also concerns.

Rib distraction (specifically for thoracic insufficiency syndrome).

Rib Distraction (VEPTR-Vertical Expandable Prosthetic Titanium Rib)

Rationale

This procedure addresses Thoracic Insufficiency Syndrome (TIS), which occurs when vertebral anomalies are associated with multiple rib fusion or absence, leading to compromised lung growth and respiratory complications.

Procedure

Involves multiple open wedge thoracotomies followed by the insertion of Vertical Expandable Prosthetic Titanium Rib (VEPTR) devices along the concave side of the curve.
Distraction is performed at 5–6 month intervals to prevent curvature progression.

Indication:

Absence or fused ribs (type II) and especially if the deformity is combined with TIS.
While VEPTR can be used from 6 months up to skeletal maturity, waiting until age >3 years is preferable for stronger fixation points on the ribs.

Complications

High rate of neurological complications (7%), with brachial plexus palsy being the most common
Rib and lamina fracture
Infection