Infantile Idiopathic Scoliosis

Infantile Idiopathic Scoliosis typically presents in the first year of life (usually noticed by parents while bathing).

• The "Molded Baby" Syndrome: Often associated with intrauterine packaging issues, leading to Plagiocephaly, Torticollis, DDH, and Metatarsus Adductus.
• Epidemiology:
  • Rare in North America (0.5%).
  • Much more common in Europe/UK (historical association with prone sleeping position, though incidence dropped after "Back to Sleep").
  • Boys are more commonly affected than girls.
  • Left Thoracic curves are the canonical pattern. (A Right Thoracic curve in a male infant is highly suspicious for syrinx).

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The Mehta Angle (RVAD) Described by Min Mehta in 1972.

• Concept: Since ribs attach to vertebrae, as the vertebra rotates, the rib on the convex side is pushed posteriorly (hump) and the rib on the concave side is pushed anteriorly.
• Measurement: Line along the vertebral endplate relative to a line along the rib head/neck.
• Difference: Convex angle minus Concave angle.
• Rule of 20:
  • RVAD less than 20 degrees = Resolving.
  • RVAD greater than 20 degrees = Progressive.

Rib-Head Phases

• Phase 1: No overlap of rib head on vertebral body apical corner.
• Phase 2: Rib head overlaps the vertebral body. (Indicates severe rotation and pending progression).

History:

• Age: Onset? (Must be less than 3).
• Development: Is the child hitting milestones?
• Pain: Pain is rare and suspicious.

Physical Exam:

1. Head: Check for Plagiocephaly.
2. Neck: Torticollis (sternocleidomastoid tight?).
3. Spine: Left sided prominence? Flexibility?
4. Hips: Ortolani/Barlow.
5. Neurology: Tone, reflexes (Abdominal!), clonus.

X-rays:

• PA and Lateral whole spine.
• Supine vs Standing: Infants are usually imaged supine or sitting.
• Measurement: Cobb angle + RVAD (Mehta).

MRI:

• Mandatory.
• Sedation usually required (General Anaesthesia) for high quality feed-and-wrap MRI is difficult in older infants.
• Must see the entire neuraxis from craniocervical junction to sacrum.

1. The Mushroom Window Infants breathe primarily with their diaphragm / abdomen. A tight abdominal cast will cause respiratory distress. The anterior window must be large and "mushroom shaped" - wide at the bottom over the belly, narrower at the top over the sternum.

2. Over-the-shoulder?

• Under arm: For low thoracic / lumbar curves.
• Over shoulder: Required for upper thoracic curves (Apex T6 or higher) to control the upper lever arm.

3. Skin Care The most common complication is skin breakdown (iliac crests, scapula). Meticulous padding and molding are essential. Educate parents on keeping the cast dry.

4. The Risser Table The casting frame (Risser table) is critical. It allows the patient to be suspended by the head (halter) and pelvis, allowing the surgeon 360-degree access to the torso for molding. The longitudinal traction itself provides significant correction before any rotation force is applied.

Cast-Related Complications

Skin Breakdown Prevention

Skin complications are the most common issue with serial casting. Key prevention strategies include:

• Meticulous padding of bony prominences (iliac crests, scapulae, clavicles, spinous processes)
• Appropriate window cutting for pressure relief while maintaining correction
• Parent education on skin inspection, cast hygiene, and early signs of problems
• Regular cast changes (typically every 2-3 months) to assess skin integrity

Respiratory Monitoring

Infants rely predominantly on diaphragmatic breathing. A restrictive cast can cause respiratory compromise:

• Warning signs: Increased respiratory rate, accessory muscle use, poor feeding, irritability
• Prevention: Large mushroom-shaped abdominal window, careful molding to avoid chest restriction
• Management: Immediate cast removal if respiratory distress suspected

Progressive Curves Despite Treatment

Some curves continue to progress despite optimal casting. Risk factors for casting failure include:

• Initial RVAD greater than 40 degrees
• Phase 2 rib head at presentation
• Late presentation (after age 2 years)
• Underlying syndromic or neuromuscular cause

For refractory cases, transition to growing rod constructs may be necessary to control the curve while preserving thoracic growth.

Cast Care Instructions

• Hygiene: Casting requires keeping the cast dry (sponge baths only). Use "Moleskin" or "Petal" tape around edges to prevent skin irritation.
• Reflux: Gastric reflux can be worsened by the abdominal pressure. Recommend smaller, more frequent feeds.
• Development: Casting generally does NOT delay walking, but may make infants "top heavy" initially.

Follow-Up Protocol

Regular monitoring is essential during serial casting treatment:

• In-cast X-ray: Obtained 1-2 weeks after each cast application to confirm correction
• Clinical review: Every 2-3 months with cast change under general anaesthesia
• Curve measurements: Track RVAD and Cobb angle progression
• Growth monitoring: Weight, length, and thoracic development

Family Education and Support

Infantile scoliosis treatment places significant burden on families. Key support measures include:

• Clear explanation of the treatment rationale and expected duration
• Written instructions for cast care and warning signs
• Access to multidisciplinary team (physiotherapy, occupational therapy, social work)
• Parent support groups and online resources
• Psychological support for managing repeated general anaesthetics

Transition from Cast to Brace

Once the curve has been corrected to less than 10 degrees with RVAD less than 0:

• Transition to a custom TLSO brace
• Initial full-time wear (23 hours per day)
• Gradual weaning based on maintenance of correction
• Continue monitoring until skeletal maturity

Resolving Curves (80-90%)

The majority of infantile scoliosis cases resolve spontaneously without intervention:

• Spontaneous resolution: Typically occurs within the first 2-3 years of life
• No treatment required: Observation with periodic radiographs only
• Excellent long-term prognosis: No residual deformity or functional limitation
• Normal growth: Thoracic development and lung function unaffected

Progressive Curves - Treated Early

For progressive curves identified early and treated with serial casting:

• Cure rate (curve less than 10 degrees): 70-80% with optimal casting technique
• Conversion to non-progressive: Many curves can be stabilized for brace management
• Normal thoracic development: Early treatment preserves lung growth
• Avoidance of surgery: Many children avoid the need for growing rods or fusion

Progressive Curves - Delayed Treatment or Refractory

Untreated progressive infantile scoliosis leads to severe deformity:

• Curve progression: Relentless progression to greater than 100 degrees without treatment
• Thoracic Insufficiency Syndrome (TIS): Restricted lung development and respiratory compromise
• Cor pulmonale: Right heart failure from chronic hypoxia
• Reduced life expectancy: Significant impact on survival if severe deformity develops

Long-Term Follow-Up Considerations

All patients with infantile scoliosis require monitoring until skeletal maturity:

• Growth spurts: Risk of curve progression during adolescent growth
• Residual deformity: May require bracing or surgical intervention
• Pulmonary function: Serial monitoring for thoracic insufficiency
• Transition to adult care: Appropriate handover for ongoing surveillance

Global epidemiology

• Infantile idiopathic scoliosis (onset before age 3) is the least common idiopathic form, historically more frequent in Europe/UK than North America. The European incidence fell after the "Back to Sleep" campaign shifted infants away from prone sleeping.
• Male predominance and left thoracic curves are the canonical pattern - the reverse of adolescent idiopathic scoliosis (female, right thoracic).
• Roughly 80 to 90% of curves resolve spontaneously; the minority that progress carry a high risk of thoracic insufficiency if untreated.

Society guidance, side by side

Registry / collaborative evidence

• Multicentre early-onset scoliosis registries (e.g. Children's Spine Study Group, Growing Spine Study Group) underpin most modern casting and growing-rod outcome data and pool cases across institutions because individual centre volumes are low.

High- vs limited-resource practice variation

• Well-resourced settings: repeated GA for cast changes, MCGR (fewer surgical lengthenings), and dedicated multidisciplinary scoliosis clinics (surgeon, orthotist, physiotherapist, anaesthetist).
• Limited-resource settings: late presentation is common (window for cure missed); traditional growing rods or definitive fusion may be the only options; repeated anaesthesia and magnet-rod technology may be unavailable, shifting practice toward casting/bracing for as long as feasible.

• MRI for every infant, or selective screening? Dobbs (2002) found 21.7% intraspinal anomalies and recommended MRI for all curves over 20 deg; Pahys (2009) found only 13% and argued close observation may be a reasonable alternative for some. Most units still obtain whole-neuraxis MRI before committing to treatment because a normal neuro exam does not exclude pathology.
• Casting: cure vs delay. Casting can genuinely reverse flexible curves started early (Mehta, Regan), but in older or non-idiopathic children it mainly delays surgery while preserving thoracic growth (LaValva). Where the true "window" closes is debated (commonly cited as before age 2 to 2.5).
• EDF (Cotrel) vs Mehta technique. Both use traction, derotation and a flexion/derotation moment; the relative contribution of each component and the optimal cast interval (8 to 12 weeks) are not standardised.
• MCGR vs traditional growing rods vs casting-to-rods. Magnetically controlled rods reduce repeated lengthening surgery but raise concerns over metallosis, rod failure and diminishing returns ("law of diminishing returns") with repeated distractions; long-term comparative data remain limited.
• Adolescent recurrence. Apparently cured curves can recur at the adolescent growth spurt (Regan), so the duration and intensity of surveillance to skeletal maturity is unsettled.
• RVAD reliability. The Mehta RVAD rule of 20 is the classic predictor but has measurement variability; some advocate combining it with rib-head phase and serial Cobb trend rather than a single threshold.

1. Identify the Apical Vertebra: The most rotated/deviated vertebra.
2. Draw the Endplate Line: A line along the perpendicular of the vertebral body endplate.
3. Draw the Rib Line: A line bisecting the head and neck of the corresponding rib.
4. Measure the Angle: The angle between these two lines on the Convex side and Concave side.
5. Calculate: Difference = Convex Angle minus Concave Angle.
   • Example: Convex 35 deg - Concave 10 deg = RVAD 25 deg. (Progressive).