VEPTR and Growing Rods for Early-Onset Scoliosis

The child with early-onset scoliosis has two coupled problems: a progressive spinal deformity and a growing respiratory system that depends on a growing thorax.

• Spinal growth: T1-S1 gains roughly 2 cm per year from birth to age 5, slows to about 1 cm per year from 5 to 10, then accelerates again in the adolescent spurt (Dimeglio). Around half of final sitting height is achieved by age 5.
• Thoracic growth: the thorax reaches about 30 percent of adult volume by age 5 and about 50 percent by age 10. An adult T1-T12 height of approximately 18 to 22 cm is regarded as the threshold for adequate lung volume; a fused short thorax cannot reach it.
• Lung growth: alveolar multiplication is most rapid in the first 2 years and largely complete by around age 8; thereafter lungs enlarge mainly by alveolar hypertrophy. Deformity control before age 8 therefore protects irreplaceable alveolar development — this is the biological deadline that frames every decision.
• Thoracic insufficiency syndrome (Campbell): the inability of the thorax to support normal respiration or lung growth — seen with fused ribs, constricted hemithorax, severe early scoliosis, and hypoplastic thorax syndromes (Jeune asphyxiating thoracic dystrophy, Jarcho-Levin spondylothoracic dysostosis). The windswept, rotated thorax reduces the space available for lung on the concavity.

Space-available-for-lung (SAL) ratio: on an upright PA radiograph, measure the height of the concave hemithorax from the apex of the most cephalad rib to the centre of the ipsilateral hemidiaphragm, and divide by the same measurement on the convex side. A ratio below approximately 0.8 to 0.9 indicates significant concave hemithorax constriction and supports thorax-based (VEPTR) treatment.

Untreated progressive EOS carries excess cardiorespiratory mortality in adulthood (Pehrsson's Swedish natural history series), which is why observation of a clearly progressive curve is not an option — but neither is early fusion. Hence: control the curve while the spine and thorax keep growing.

All EOS patients need whole-spine MRI before instrumentation: neural axis anomalies (syrinx, Chiari, tethered cord, diastematomyelia) occur in roughly one in five infantile idiopathic curves and more frequently in congenital scoliosis.

Implant-specific additions: TGR — rod fracture (commonest at tandem connectors), anchor pull-out. MCGR — metallosis and elevated tissue titanium around the actuator, failure to lengthen, actuator pin fracture, MRI compatibility caveats (image quality artefact and rod behaviour concerns), and episodes of regulatory scrutiny including temporary market suspension in some jurisdictions. VEPTR — rib cradle migration, rib erosion, brachial plexus traction. Shilla — sliding-interface metal debris, adding-on deformity.

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• T1-T12 height: proxy for thoracic and lung volume growth; target trajectory towards 18 to 22 cm at maturity; normal growth about 1.4 cm per year in this age range (Dimeglio) — compare achieved gain against this benchmark.
• T1-S1 height: total spinal growth achieved by the programme.
• Cobb angle: control, not necessarily cure; expect the best correction at index surgery.
• Space-available-for-lung ratio: thorax-specific measure, particularly for VEPTR.
• EOSQ-24: validated parent-reported quality-of-life instrument for EOS — increasingly the headline outcome, since radiographs do not capture the burden of repeated surgery.
• Complications per patient and unplanned returns to theatre: report honestly.

When the child approaches skeletal maturity (or the construct is exhausted and the spine autofused), three options exist:

• Definitive posterior fusion: traditional default — formal exposure, implant exchange to a definitive construct, correction of residual deformity. Reality check: the autofused, stiff, previously distracted spine yields limited additional correction, and complication rates at final fusion are meaningful (Flynn's Growing Spine Study Group data).
• Retention in situ ("graduate without fusion"): leave the mature construct undisturbed if alignment is acceptable and the spine is effectively autofused — avoids a large final operation; risk of late rod fracture and slow curve creep requires surveillance.
• Implant removal without fusion: occasionally chosen for infection or prominence; risk of deformity progression after removal even in apparently stiff spines — least favoured for structural curves.

The decision weighs residual deformity, sagittal balance, autofusion extent, implant integrity, infection history and family priorities. There is no consensus — this is a legitimate "discuss the options" viva answer.

• Global epidemiology: EOS is uncommon relative to adolescent idiopathic scoliosis but disproportionately morbid; congenital and syndromic causes dominate surgical caseloads worldwide, while presentation is later and curves larger in resource-limited settings where casting infrastructure and device access are constrained.
• Society guidance: the Scoliosis Research Society Growing Spine Committee consensus defines EOS as onset before age 10 and endorses growth-friendly strategies over early fusion; the SRS-endorsed EOS classification (Williams — aetiology, Cobb, kyphosis, progression modifier) standardises communication. POSNA and BSCOS practice statements support serial casting as first-line for progressive infantile idiopathic curves. AAOS and NICE have no dedicated EOS implant guidance; NICE and MHRA involvement has centred on MCGR device safety review, including a period of restricted use pending investigation of metallosis and actuator concerns — candidates should know MCGR has faced genuine regulatory scrutiny.
• Registry and study-group evidence: national arthroplasty-style registries do not capture EOS; the field's registry equivalents are the Growing Spine Study Group and the Children's Spine Study Group / Paediatric Spine Study Group, whose pooled multicentre data underpin most complication and outcome figures quoted above.
• Practice variation by resource setting: MCGR cost and controller availability limit use in many health systems; TGR and Shilla (no scheduled lengthenings) remain workhorses where repeated theatre access or magnetic controllers are unavailable; casting programmes are highly cost-effective and exportable, and several global outreach programmes prioritise establishing EDF casting before implant services.

• MCGR versus TGR overall benefit: MCGR clearly reduces anaesthetic episodes, but total revision burden, metallosis significance, and cost-effectiveness remain debated; randomised data are sparse.
• Graduation strategy: definitive fusion versus retention in situ versus removal — no consensus; observational data suggest many "graduates" do acceptably without formal final fusion, but selection bias is heavy.
• Optimal proximal anchor: screws versus hooks versus rib anchors for PJK prevention — biomechanically argued, clinically unresolved.
• Distraction frequency: more frequent small MCGR distractions are argued to be more physiological; the ideal interval is unknown.
• How much correction matters: whether aggressive Cobb correction improves pulmonary outcomes beyond height and SAL gains is unproven — thoracic growth, not radiographic cosmesis, is the goal.