VEPTR and Growing Rods for Early-Onset Scoliosis

Elongation-derotation-flexion (EDF) casting under general anaesthesia on a specialised frame (Risser or Mehta table) with longitudinal traction, a derotational moulding force applied over the rib prominence (not directly on the apex, to avoid rib deformation), and windows cut anteriorly for chest expansion and posteriorly over the concavity to allow the thorax to derotate into the space.

• Who: progressive infantile idiopathic scoliosis, ideally started before age 2 with curves under approximately 60 degrees — this population can achieve full resolution (Mehta's series showed curve resolution in the majority treated before 2 years).
• Predictors of progression (Mehta, 1972): rib-vertebra angle difference (RVAD) greater than 20 degrees, and phase 2 rib (convex rib head overlapping the apical vertebral body on the PA film). Draw the RVAD: on the apical vertebra, the angle between a perpendicular to the endplate and a line along each rib neck; convex angle subtracted from concave angle.
• Technique points: casts changed every 8 to 12 weeks (more frequently in the youngest); each change is an anaesthetic — balance against progression risk; transition to bracing once correction is held.
• In non-idiopathic EOS: casting rarely cures but is a legitimate delay tactic — buying spinal height and postponing the first implant (each year gained matters).

Thoraco-lumbo-sacral orthoses hold rather than correct in EOS. Roles:

• Maintaining correction after casting.
• Delaying surgery in slowly progressive curves.
• Poorly tolerated and less effective in neuromuscular and syndromic groups; chest-wall compliance concerns in infants mandate careful fitting.

Bracing is a bridge, not a destination, in progressive structural EOS — the decision it defers is when, not whether, to instrument.

• Observe: infantile idiopathic curve with RVAD less than 20 degrees, phase 1 rib, curve under 25 degrees — the majority resolve.
• Cast: documented progression, RVAD greater than 20 degrees or phase 2 rib, age under 2 to 3, curve roughly 25 to 60 degrees.
• Flip to surgery: progression despite casting/bracing beyond approximately 50 to 60 degrees; congenital anomalies with predicted relentless progression; thoracic insufficiency syndrome with declining respiratory function or SAL deterioration; age and remaining growth determine growth-friendly versus (rarely, near maturity) definitive fusion.
• Which factor changes the operation: fused ribs and constricted hemithorax push towards VEPTR; need for repeated anaesthetics avoided pushes towards MCGR; hyperkyphosis or very small stature limits MCGR (actuator length and rod contouring constraints); neuromuscular pelvic obliquity mandates pelvic anchors.

Indication: progressive EOS (typically greater than 50 to 60 degrees) with substantial growth remaining, failed or unsuitable for casting, without fused ribs demanding thorax-based treatment. Contraindication: active infection, insufficient bone stock for foundations, kyphosis beyond actuator tolerance (MCGR), very small stature precluding actuator (MCGR). Why this over alternatives: spine-based distraction gives more powerful curve correction than VEPTR; MCGR over TGR when reducing anaesthetic exposure is a priority.

• Position: prone on a radiolucent table, chest and pelvic bolsters, abdomen free, head in a padded holder or Mayfield in the very small; all pressure points padded.
• Imaging/equipment: fluoroscopy; multimodal neuromonitoring (SSEP and MEP) mandatory; cell salvage in small children; MCGR external remote controller checked and rods templated for actuator length.
• Preparation: prophylactic antibiotics; tranexamic acid per protocol; whole-spine MRI reviewed preoperatively.
• Approach: two limited midline (or paramedian muscle-splitting) incisions over the planned proximal and distal foundations only — do not expose the intervening spine, to limit autofusion.
• Dissection: subperiosteal exposure confined to foundation levels; proximal foundation typically T2-T4 with 4 anchor points (pedicle screws, or hooks/rib anchors in poor bone — hooks or rib-based proximal anchors may reduce PJK by preserving the posterior tension band); distal foundation 2 levels of pedicle screws below the end vertebra; iliac or S2-alar-iliac screws for pelvic obliquity.
• Reduction/Reconstruction: rods contoured to sagittal profile (limit contour near the MCGR actuator — it must remain straight over the actuator segment), tunnelled submuscularly (submuscular passage has lower infection and rod fracture rates than subcutaneous), connected via tandem connectors (TGR) or as single actuator rods (MCGR); gentle distraction with monitoring stable.
• At-risk structures: spinal cord (monitor throughout, especially during distraction), pleura at proximal thoracic anchors, great vessels with mal-directed screws, skin envelope in thin children.
• Closure: layered, watertight; local antibiotic powder used by many units.
• Aftercare: TGR — surgical lengthening every 6 months, day-case where feasible; MCGR — outpatient magnetic lengthenings every 1 to 3 months, small increments, distraction confirmed by ultrasound or radiograph; brace rarely needed with dual rods.
• Pitfalls: exposing the mid-spine (accelerates autofusion); over-distraction causing PJK or neurological signal change — distract to soft endpoint, never force; MCGR actuator placed where kyphosis contour is needed.
• Salvage of failure: rod fracture — exchange; anchor pull-out — augment or extend foundation; deep infection — debridement with implant retention early, staged exchange if chronic; construct exhausted — proceed to graduation strategy.

Indication: thoracic insufficiency syndrome — fused ribs with congenital scoliosis, constricted hemithorax (SAL below approximately 0.8), Jeune and Jarcho-Levin thoracic hypoplasia, flail chest wall after resection. Contraindication: inadequate rib stock for cradles, absent diaphragm function making thoracic expansion futile, poor soft tissue coverage. Why this over growing rods: it treats the thorax, not merely the spinal curve — rib-based anchors and thoracostomy directly enlarge the constricted hemithorax and can avoid spine exposure altogether.

• Position: lateral decubitus (concave hemithorax up) for thoracostomy and rib-to-rib devices; prone for rib-to-spine or rib-to-pelvis hybrids.
• Imaging/equipment: fluoroscopy; neuromonitoring including upper-limb SSEPs for brachial plexus surveillance; CT with 3D reconstruction reviewed for rib anatomy and fusion mass.
• Approach: curvilinear thoracotomy-type incision along the concavity; muscle flaps preserved for coverage.
• Dissection and expansion thoracostomy: the fused rib mass on the concavity is divided as an opening wedge (Campbell's expansion thoracostomy) — the constricted hemithorax is levered open, acutely increasing concave volume; extraperiosteal dissection around cradle ribs preserving intercostal neurovascular bundles and pleura where possible.
• Reconstruction: superior cradle around a structurally sound rib — second rib or below (never the first rib); inferior anchor on a caudal rib, a lumbar lamina hook, or the pelvis (Dunn-McCarthy S-hook over the iliac crest) depending on construct; device expanded to hold the thoracostomy open.
• At-risk structures: brachial plexus (cephalad cradles, over-distraction elevating the first rib), intercostal bundles, pleura/lung, and the thin overlying skin.
• Closure: robust muscle coverage over the device is critical; chest drain if pleura breached.
• Aftercare: expansion through small incisions every 6 months; monitor SAL, T1-T12 height and respiratory function.
• Pitfalls: rib cradle migration and erosion through osteopenic ribs (commonest device problem); wound breakdown over prominent hardware in cachectic children — plastic surgical involvement early; modest coronal correction — do not promise growing-rod-level Cobb correction.
• Salvage of failure: migrated cradle — move to an adjacent intact rib or convert to a hybrid rib-to-spine or spine-based construct; recurrent wound failure — flap coverage or device removal and strategy change.

Indication: EOS with a discrete apex amenable to limited fusion, in families/settings where repeated lengthenings are impractical (a genuine consideration in resource-limited settings). Principle: the apex (typically 3 to 4 levels) is corrected, instrumented and fused with fixed screws; cephalad and caudad, non-locked "Shilla" screws capture but do not lock the rods, allowing the spine to slide and grow along them.

• Trade-offs: no scheduled lengthenings versus metal-on-metal debris at sliding interfaces (documented histologically), unpredictable guidance with adding-on deformity, and the need for rod exchange if growth exceeds rod length. McCarthy's originating series showed comparable radiographic outcomes to TGR with fewer total operations.