Early Onset Scoliosis (EOS)

Early Onset Scoliosis is a time-based definition (Age less than 10). It encompasses a heterogeneous group of diagnoses.

• Pulmonary Impact: The primary concern is Thoracic Insufficiency Syndrome (TIS).
  • Alveoli multiply rapidly until age 8.
  • Severe deformity restricts lung volume, leading to restrictive lung disease to Pulmonary Hypertension to Cor Pulmonale to Early Death.
• Epidemiology:
  • Infantile Idiopathic: Rare (under 1% of all idiopathic scoliosis in most series). Male predominance. Left-sided thoracic curves are typical. Higher incidence historically reported in Europe than North America.
  • Juvenile Idiopathic: Female predominance. Right-sided thoracic curves (like AIS). Progression is common and often relentless without treatment.

The Mehta Angle (Rib-Vertebral Angle Difference - RVAD) This is the angle between the rib neck and the vertebral body.

• Measured at the apical vertebra.
• Calculation: RVAD = Angle on Concave side - Angle on Convex side.
• Significance:
  • Less than 20 degrees: 80% chance of spontaneous resolution. (Resolving).
  • Greater than 20 degrees: 80% chance of progression. (Progressive).

Rib Head Phases (Mehta)

• Phase 1: Prominent gap between rib head and vertebral body.
• Phase 2: Rib head overlaps the vertebral body. Indicates progression.

History:

• Birth Hx: Prematurity? NICU admission?
• Development: Walking age? Milestones? (Neuromuscular).
• Family Hx: Neurofibromatosis? Marfan?

Physical Exam:

1. Skin: Café-au-lait spots (NF1), Hairy patch (Spinal dysraphism), Laxity (Ehlers-Danlos).
2. Neurology: Full exam. Abdominal reflexes are critical for Syringomyelia.
3. Spine: Assess flexibility. Can you correct it with traction/bending?
4. Chest: Pectus deformities? Rib hump?

Imaging:

• Whole Spine X-ray (PA and Lateral): Measure Cobb, Kyphosis.
• Bending Films / Traction Films: Assess flexibility.
• Mehta Angle (RVAD): Calculate on apical vertebra.

MRI (Whole Spine):

• Mandatory for all patients.
• Look for: Chiari Malformation, Syrinx, Tethered Cord, Diastematomyelia, Intraspinal tumors.

Genetic Testing:

• Consider if syndromic features present (Microarray).

1. The Law of Diminishing Returns With traditional growing rods, every time you go in to lengthen (every 6 months), the spine gets stiffer (auto-fusion). By the time you do the final fusion, the spine may already be fused in a less-than-perfect position. MCGR helps avoid this "Law of Diminishing Returns" by avoiding open surgery.

2. Crankshaft Phenomenon If you fuse the posterior elements (or they auto-fuse) but the anterior vertebral body growth plates remain open, the spine will twist and rotate as it grows anteriorly.

• Prevention: In young children (less than 10), definitive fusion often requires Anterior and Posterior fusion to stop all growth centers.

3. Hemiepiphysiodesis For a congenital hemivertebra:

• You can fuse the convex side (epiphysiodesis). The concave side continues to grow, potentially correcting the curve over time.
• Or: Resect the hemivertebra entirely (more aggressive, better correction).

• Bracing: Most growing rod patients wear a brace post-op to protect the anchors.
• Physio: Essential to maintain flexibility (auto-fusion prevention).
• Follow-up: Lengthening schedule (MCGR: Clinic every 3 months. TGR: Surgery every 6 months).

• Pulmonary: The main goal is survival. Early fusion (less than age 5) results in severe TIS and death. Delaying fusion until age 10-12 significantly improves pulmonary volume.
• Deformity: complete correction is rarely the goal. "Control" is the goal.
• Final Fusion: Usually performed at skeletal maturity (Age 12-14 females, 14-16 males) to lock in the correction.

• RVAD threshold: The classic 20-degree Mehta cut-off is challenged — long-term data suggest an optimal threshold nearer 17 degrees and warn against relying on a single index measurement (Lloyd et al, 2020). Serial RVAD and Cobb trends are more reliable than any one value.
• MCGR metal ions and reliability: Magnetically controlled rods reduce open lengthenings, but elevated serum titanium, actuator/pin failure, and progressive loss of distraction (a residual "law of diminishing returns") generate ongoing debate about long-term safety and true cost-effectiveness.
• Casting vs early surgery: When to abandon casting for a growth-friendly construct is not standardised. Casting can be curative if started under age 2, but late or stiff curves respond poorly.
• Rib-based vs spine-based anchors: VEPTR (rib-based) directly expands the thorax but has high migration/cutout rates; spine-based anchors give better deformity control but less direct chest-wall benefit. The optimal hybrid is unsettled.
• Graduation strategy: Whether to perform definitive fusion, "watchful waiting" with retained rods, or remove implants at skeletal maturity remains individualised, with no consensus on the best endpoint.
• Crankshaft prevention: The need for anterior growth arrest (combined anterior/posterior fusion) in very young children is debated in the era of all-pedicle-screw posterior constructs.

Global epidemiology

• EOS is a heterogeneous, time-based group (onset under age 10). Idiopathic infantile scoliosis accounts for under 1% of idiopathic curves in most series, with historically higher reported rates in Europe than North America. Congenital and neuromuscular aetiologies dominate the structural/progressive end of the spectrum worldwide.

Society guidance, side by side

Registry and multicentre evidence

• Practice is driven largely by multicentre prospective EOS registries (e.g. the Pediatric Spine Study Group / Growing Spine Study Group datasets) rather than national arthroplasty-style registries, given device diversity and small numbers. These cohorts underpin the data on dual-rod growth rates, MCGR diminishing returns, and complication profiles.

High- vs limited-resource practice variation

• High-resource settings: ready access to whole-spine MRI, MCGR (avoiding repeated open lengthenings), VEPTR, intraoperative neuromonitoring and multidisciplinary paediatric pulmonology/spine teams.
• Limited-resource settings: greater reliance on serial casting and traditional growing rods (lower implant cost but repeated GA), with MRI and MCGR access constrained. Halo-gravity traction is a valuable low-cost adjunct for severe rigid curves. Late presentation with established thoracic insufficiency is more common.

The Mehta Technique Min Mehta revolutionized the treatment of infantile scoliosis.

• Principle: The spine grows rapidly in the first 2 years. If you can hold it straight, the growth will correct the deformity (Hueter-Volkmann law).
• Technique:
  • General Anaesthesia.
  • Risser Table (Traction frame).
  • Derotation: Correct the rotation, not just the lateral bend. Mold over the apical rib hump.
  • Window: Cut a large anterior "mushroom" window for belly breathing (infants are diaphragmatic breathers).
• Result: Can result in a permanent cure for idiopathic curves if started early.