Congenital Scoliosis

Congenital scoliosis is a lateral curvature of the spine caused by vertebral malformations present at birth: failure of formation (wedge vertebra, hemivertebra), failure of segmentation (unilateral bar, block vertebra), or a mixture of both. The malformation produces unbalanced growth, so the curve can progress throughout childhood.

It affects about 0.5 to 1 in 1000 live births, with a slight female predominance, and most cases are sporadic (the recurrence risk in a sibling is about 1 to 5%).

Associated anomalies are common: 20 to 40% have an intraspinal anomaly (tethered cord, diastematomyelia, syrinx, Chiari malformation), 20 to 30% have a renal or urinary tract anomaly, and 10 to 15% have a cardiac anomaly.

The condition may be part of VACTERL association, Klippel-Feil syndrome, spondylocostal dysostosis, Alagille syndrome or Goldenhar syndrome. Maternal diabetes in early pregnancy is a risk factor.

The risk of progression depends on the pattern. A unilateral unsegmented bar with a contralateral hemivertebra progresses fastest (often more than 5 degrees a year, and over 10 degrees a year in some), then a unilateral bar, then a fully segmented hemivertebra, while a block vertebra and an incarcerated hemivertebra progress least. Complications are severe deformity, trunk imbalance, thoracic insufficiency syndrome (a thorax unable to support normal breathing or lung growth), pain in adulthood, neurological compromise and psychological distress.

Pathophysiology.

The vertebral column forms from somites between weeks 4 and 6 of gestation, and a fault in somite formation or separation leaves an abnormal vertebra. Variants in genes of the segmentation clock (DLL3, MESP2, LFNG, HES7, TBX6) and deletions at 16p11.2 are found in a minority. A hemivertebra has its own growth plates and adds growth on the convex side, while a unilateral bar stops growth on the concave side, so the curve lengthens with every growth spurt.

The deformity is often found at birth, on a prenatal scan, or during assessment of another anomaly. It presents as trunk asymmetry, a tilted head or shoulder, a short neck, a rib prominence, a pelvic tilt, or a curve noticed in the first years of life. Back pain is uncommon in children.

Examine the skin of the back (hairy patch, dimple, naevus), the feet (cavus, asymmetry), neurological state (tone, reflexes, abdominal reflexes, gait), chest wall expansion and breathing, the heart, limbs and hands, and the neck. A cavovarus foot or asymmetric reflexes suggest intraspinal disease.

• Radiographs: full spine posteroanterior and lateral views at a low radiation dose, with serial Cobb angle measurement on the same technique at each visit. Classify the anomaly (wedge vertebra, fully segmented, semi-segmented or incarcerated hemivertebra, unilateral bar, block vertebra, mixed) and note the spinal region and rib anomalies.
• CT with three dimensional reconstruction defines the anatomy before surgery, using a low dose technique.
• MRI of the whole neuraxis in every child before any surgery, even with a normal neurological examination, because intraspinal anomalies are found in 20 to 40%.
• Renal ultrasound and echocardiography at diagnosis. Pulmonary assessment (chest wall volume, ventilation) in thoracic curves with rib fusions.
• Genetic testing (chromosomal microarray, exome or gene panel) when other anomalies exist; prenatal ultrasound may show the malformation from 18 to 20 weeks.

Differential diagnosis.

• Infantile and juvenile idiopathic scoliosis.
• Neuromuscular and syndromic scoliosis (neurofibromatosis type 1, skeletal dysplasia, Marfan syndrome).
• Scoliosis from a spinal tumour or syrinx.
• Postural curve or curve secondary to a leg length difference.

The aim is to control progression early, keep a balanced trunk, protect the spinal cord, and allow lung and spine growth.

Observation. Clinical review and a radiograph every 4 to 6 months in the first years, until the pattern is clear. Curves with a low risk of progression (block vertebra, incarcerated hemivertebra, balanced hemivertebra) may need only observation.

Orthoses. A brace does not control the congenital curve itself. It is used for flexible compensatory curves proximal or distal to the congenital segment to limit secondary structural change, with limited benefit.

Surgery (before the curve becomes severe, usually between 1 and 5 years of age).

• Hemivertebra excision (posterior approach, with short segment instrumentation) for a fully segmented hemivertebra with progression, especially at the lumbosacral junction; correction is about 50 to 70%.
• Short segment in situ fusion for small, progressive curves; convex hemiepiphysiodesis in very young children with growth potential on the concave side.
• Growth friendly systems for long, progressive curves or thoracic insufficiency: dual growing rods, magnetically controlled growing rods, and expandable rib based implants (with opening wedge thoracostomy when ribs are fused). Lengthening is repeated every 6 months (every 1 to 3 months with magnetic rods).
• Definitive fusion near skeletal maturity.
• Intraoperative spinal cord monitoring (motor and sensory evoked potentials). Neurological injury occurs in about 1 to 2%, higher in patients with intraspinal anomalies and in vertebral resections. Other risks: rod fracture, infection, implant prominence, proximal junctional kyphosis, and crankshaft progression after posterior fusion in a young child.
• Neurosurgical correction of a tethered cord, syrinx or diastematomyelia may be needed before or with spinal surgery.

Operative antibiotic prophylaxis. Cefazolin 30 mg/kg to a maximum of 2 g intravenously (2 g in adolescents; 3 g when weight is 120 kg or over) within 60 minutes before incision, repeated after 4 hours or blood loss over 1500 mL (or 25 mL/kg); with severe penicillin allergy, clindamycin 10 mg/kg (maximum 900 mg) intravenously or vancomycin 15 mg/kg intravenously starting 90 to 120 minutes before incision as a single dose, with levels and creatinine checked in prolonged cases.

Tranexamic acid (spinal surgery). Tranexamic acid 50 mg/kg intravenously over 15 minutes before incision, followed by 5 mg/kg/hour until wound closure (maximum 100 mg/kg in total, or 4 g); avoid with a history of thromboembolism, active intravascular clotting or seizures, and reduce the dose with creatinine clearance under 50 mL/min; watch for seizures at high doses.

Analgesia.

• Paracetamol 15 mg/kg orally or intravenously every 4 to 6 hours (maximum 75 mg/kg daily and not exceeding 4 g daily).
• Morphine by patient controlled analgesia (bolus 10 to 20 micrograms/kg, lockout 5 to 10 minutes, maximum 0.3 mg/kg in 4 hours) for 24 to 72 hours, then oral morphine 0.1 to 0.2 mg/kg every 4 hours as needed (maximum 10 mg a dose); monitor sedation, respiratory rate and oxygen saturation; prescribe a laxative and ondansetron 0.1 mg/kg intravenously or orally (maximum 4 mg a dose) every 8 hours as needed.
• Gabapentin 5 mg/kg orally (maximum 300 mg) at night, increased to 5 to 10 mg/kg three times daily (maximum 900 mg three times daily; reduce at creatinine clearance under 60 mL/min) for up to 2 weeks; monitor sedation and dizziness.

Thromboprophylaxis. Early mobilisation; mechanical measures in adolescents; no routine pharmacological prophylaxis in children under 14 years.

Monitoring. Radiographs every 3 to 6 months while growing, growth and trunk balance, rod lengthening schedule, neurological state at each visit, and respiratory function in thoracic curves. MRI of the spine if neurological signs appear. Renal and cardiac follow up when anomalies exist. Wound and neurological checks daily in hospital after surgery, then review at 2 weeks, 6 weeks, 3 months, 6 months and 12 months.

Referral and escalation. Refer every infant or child with a vertebral anomaly to a paediatric spinal service at diagnosis. Urgent referral for a rapidly progressing curve (over 10 degrees in 6 months), neurological signs, thoracic insufficiency, or breathing difficulty. Emergency referral for a new neurological deficit.

Special groups.

• Infants with VACTERL association: coordinate cardiac, renal, gastrointestinal and spinal care.
• Thoracic insufficiency syndrome: early expansion thoracoplasty with expandable rib based implants.
• Genetic counselling for families: recurrence risk is low (1 to 5%); folic acid 400 micrograms daily from before conception to 12 weeks of pregnancy (5 mg daily with diabetes, obesity or a previous neural tube defect).
• Untreated adults with large curves: pain, cardiopulmonary monitoring and surgery for decompensation.