Pediatric idiopathic scoliosis

Introduction

Scoliosis is a coronal curvature of the spine measuring > 10°. This article focuses on idiopathic scoliosis, which is a diagnosis of exclusion. The differential diagnosis is vast (see table below); however, the majority of scoliosis cases – about 80% – are idiopathic. The age at onset is used to define/group idiopathic scoliosis:

• Infantile (0-3 years old)
• Juvenile (4-10 years old)
• Adolescent (11-17 years old)
• Adult (?18 years)

Infantile Idiopathic Scoliosis (IIS)

• Male:Female = 3:2
• Incidence: 0.5%
• Associated conditions include plagiocephaly, hip dysplasia, congenital heart disease, and mental retardation
• Increased incidence of neural axis abnormalities (ie, Chiari malformation, syringomyelia, brain stem tumor, etc)
• Majority of curves resolve spontaneously and are self-limiting; curves developing within first year of life have greatest likelihood of resolving

Juvenile Idiopathic Scoliosis (JIS)

• Male:Female = 1.6:1 if < 6 years old and 1:2.7 if > 6 years old at presentation¹
• Incidence: 10.5%
• Often progressive with potential for severe trunk deformity
• More likely to progress and require surgical intervention
• Curves ?30° nearly always progress if left untreated
• Rate of progression
  • 1-3°/year before age 10
  • 4.5-11°/year after age 10¹

Adolescent Idiopathic Scoliosis (AIS)

• Equal male to female ratio for smaller curves
• Male:Female = 1:8 for progressive curves requiring treatment
• Most common form of idiopathic scoliosis; incidence: 89%²
• About 2% of adolescents have a scoliotic deformity ?10°; only 5% of those progress to > 30°

Anatomy

• Three-dimensional deformity including coronal plane, sagittal plane, and torsional malalignment of the spinal column
• Curve location (based on apex of curve)
  • Cervical: C2-C6
  • Cervicothoracic: C7-T1
  • Thoracic: T2-T11
  • Thoracolumbar: T12-L1
  • Lumbar: L2-L4
• Major curve: Largest measured curve based on the Cobb angle
• Minor curve: Lesser magnitude curves; compensatory curves to balance the spine over the pelvis
• Structural vs. non-structural curves: Defined based on curve magnitude on side-bending AP radiographs³
  • Structural: ? to 25°
  • Non-structural: < 25°
• Lenke et al incorporated sagittal plane alignment into curve classification;³ structural criteria for minor curves include:
  • Proximal thoracic kyphosis (T2-T5) ?20°
  • Main thoracic kyphosis (T10-L2) ?20°
  • Thoracolumbar/lumbar kyphosis (T10-L2) ?20°
• Normal+ sagittal alignment:
  • Thoracic kyphosis averaging 30-35° (T5-T12)
  • Lumbar lordosis averaging 50-60° (T12-S1)
  • Scoliosis is associated with decreased thoracic kyphosis
  • Right-sided thoracic curve the most common deformity for AIS
  • Left-sided thoracic curve more common in IIS
• “Hump” on back is caused by rib prominence due to rotational deformity of vertebrae and rib cage

Classification

Lenke Classification System for Scoliosis

Curve types in the Lenke Classification System³

Criteria for each curve type in the Lenke Classification System³

King-Moe Classification System

Pathogenesis

• Unknown etiology, hence the term “idiopathic”
• However, many theories exist:
  • Genetic: Increased incidence of scoliosis in families of affected individuals.
    • 11.1% incidence in first-degree relatives²
    • In monozygotic twins, frequency of scoliosis in both twins when one is affected is 73%-92%
    • In dizygotic twins, frequency of scoliosis in both twins when one is affected is 36%-63%^5,6
    • Specific responsible genes remain unknown
  • Tissue deficiencies: Conditions affecting the structural architecture of the spine (bone, muscle, ligament, disc) often associated with scoliosis, including fibrous dysplasia, Duchenne muscular dystrophy, and Marfan syndrome
    • Osteopenia also suggested as a cause
      • Lower bone mineral density of vertebral bodies in girls with scoliosis aged 12-14 years compared to matched controls^7-9
  • Vertebral growth abnormalities: Onset and progression of scoliosis related to adolescent growth spurts, giving rise to theories suggesting abnormalities in vertebral growth as an etiology
    • Disparate growth rates between right and left sides of the spine leading to asymmetry^10-15
    • Altered growth with increased length of anterior column results in relative thoracic lordosis; subsequently, spine rotates and buckles its apical segments laterally to effectively shorten anterior column and maintain global sagittal balance ¹⁶
    • Increased levels of growth hormones found during growth spurts also linked to development of scoliosis;^17,18 however, no definitive relationship has been established
    • Asymmetric growth and wedging of spine occurs as disease progresses following the Heuter-Volkmann principle; compression of spine at the concavity results in reduced growth
  • Central nervous system: Greater asymmetry of cerebral cortices, abnormalities in equilibrium/vestibular function, and syringomyelia noted, but no causal relationship established ^19-23
    • Melatonin deficiency and elevated calmodulin levels also postulated, again with no clear relationship

Natural History

• Incidence of back pain among patients with scoliosis is similar to that in the general population
• Early-onset idiopathic scoliosis more likely to be progressive
• Rib-vertebra-angle-difference (RVAD) of more than 20° associated with high likelihood of progression for IIS²⁴
• In JIS, curve apex at T8, T9, or T10 indicates an 80% chance that spinal fusion will be needed by age 15¹
• Curve progression is greatest during peak skeletal growth
• Thoracic curves with apex above T12 more likely to progress than lumbar curves; curves with greater magnitude more likely to progress^25-28
• Curves may progress after skeletal maturity:
  • Thoracic curves < 30° tend not to progress
  • Thoracic curves between 50° and 75° progress at 1° per year
  • Lumbar curves > 30 ° tend to progress^29,30
• Severe curves may lead to cardiopulmonary compromise and increased mortality rate^31,32

Clinical Presentation

Patient History

• Often presents after routine school screening examination
• Obtain a focused history
  • Neurological history: Positive findings suggest a non-idiopathic cause
    • Symptoms include weakness, sensory loss, ataxia, radiating pain, paresthesias, numbness, persistent headaches, visual disturbances, bowel/bladder incontinence
  • Back pain: Severe back pain suggestive of a non-idiopathic etiology
    • For example, scoliosis with associated osteoid osteoma commonly presents with significant back pain
  • Family history: Three times more likely to occur if a parent is affected; seven times more likely if sibling is affected³³
  • Surgical history: May also rule out idiopathic scoliosis if associated congenital condition identified
  • Growth history: Recent growth useful in predicting curve progression; breast development and menses may serve as key landmarks in history for females

Physical Findings

• Evaluate pubertal development: Tanner staging may be performed
• Evaluate body/trunk asymmetry
  • Shoulder height, scapular positioning, waist crease symmetry, pelvic tilt, truncal shift
  • Adam’s forward bend test evaluates rotational deformity of spine
• Neurologic exam
  • Gait, motor, sensory, and reflex examination for all four extremities and abdomen
• Evaluate limb lengths; discrepancies may cause compensatory curvature of spine
• Cutaneous examination: Skin lesions may indicate associated diseases, such as:
  • Café au lait spots and axillary freckles: Neurofibromatosis
  • Hairy patch or skin dimpling in lumbosacral area: Spina bifida, diastemetomyelia
  • Skin/joint laxity: Marfan syndrome, Ehlers-Danlos, other connective tissue disorders

Imaging and Diagnostic Studies

• Standing PA spine X-ray: Entire spine from T1 to pelvis on one cassette
• Lateral spine X-ray: Usually obtained after diagnosis is confirmed unless back pain or sagittal deformity noted on physical exam
• Lateral bending X-ray: Used to assess structural vs. non-structural curves for surgical treatment; typically performed supine, but may also be done standing or over a bolster
• Stagnara oblique view: Taken perpendicular to the rib prominence; provides more accurate view of large curves³⁴
• MRI, CT, and bone scans may be used in select patients with associated neurologic findings, atypical curves, and/or severe back pain suspicious for an associated condition (eg, spondyloysis, tumor, infection)
• Examine radiographs for soft tissue abnormalities, congenital bone abnormalities (eg, hemivertebrae, bar formation, spina bifida), bone lucency (may suggest tumor or infection), and curvature
• Cobb method used to measure magnitude of each curve

Cobb's angle evaluates curves in scoliosis based on an AP radiograph of the spine (image from xray2000, www.e-radiography.net)

• Compare most recent X-rays to X-rays from the original and previous visits for analysis of curve progression
• Vertebral rotation may be assessed on radiographs through asymmetry of pedicles and/or shift of spinous processes:
  • Cobb method
  • Nash-Moe method
  • Perdriolle method³⁵
  • Stokes’ method
• Assess growth potential radiographically:
  • Risser sign
  • Triradiate cartilage closure
  • Greulich and Pyle method
  • Sauvegrain et al method³⁶
• Tanner-Whitehouse-III RUS scores and digital skeletal age maturity scoring system correlate highly with curve acceleration phase for girls with idiopathic scoliosis^37,38

Differential Diagnosis

Treatment

Observation

• Curves < 25° monitored every 4 to 12 months with clinical and radiographic exams
• IIS with RVAD < 20° should be followed every 4-6 months.
• Patients during peak height velocity require monitoring every 4-6 months
• Curves > 50° at skeletal maturity should be monitored every 5 years

Casting

• Serial casting may be performed for those with IIS or JIS

Bracing

• Goal of bracing: Maintain or slow progression of current deformity
• Indications:
  • Growing children/adolescents with curves 25°-45°
  • Growing patients with curves < 25° but with a markedly significant increase in curve magnitude from previous measurements
• Bracing for 23 hours/day has been recommended until completion of growth
• Several brace types available, including:
  • Milwaukee brace
  • Boston brace
  • Wilmington brace
  • Charleston brace
• Skepticism exists regarding the effectiveness of part-time bracing^39-43
  • For curves 36°-45°, 83% of the curves treated with Charleston brace had curve progression, versus 43% treated with Boston brace.
    • Recommended that Charleston brace be reserved for single lumbar or thoracolumbar curves less than 35°⁴⁴

Surgical Intervention

• Goals of surgery: Obtain curve correction, restore spinal balance, prevent future progression
• Indications (guidelines and not absolute indications):
  • Thoracic curves > 45° in the skeletally immature
  • Thoracic curves > 50° in the skeletally mature with symptoms and/or progression
• Techniques
  • Posterior instrumentation and fusion
    • Originally popularized by Harrington
    • Most commonly employed technique
    • Can be performed with hooks, screws, and/or sublaminar wires with rigid rod fixation
  • Anterior instrumentation and fusion
    • Generally limited to deformities with a single curve
    • Saves fusion segments
    • Can minimize or prevent crankshaft phenomenon
    • Need an access surgeon
    • May have negative effects on pulmonary function
  • Combined anterior and posterior fusion
    • Large rigid curves (ie, > 75° curves with bend correction < 50°)
    • Those at risk for crankshaft deformity
    • Less common with use of periapical releases and osteotomies
  • Instrumentation without fusion
    • Used in younger children with large progressive curves despite cast and/or brace treatment
    • Instrumentation placed subcutaneously or subfascially spanning the deformity; sequential distraction performed every 6 to 12 months until growth and correction optimized, followed by definitive instrumentation and fusion

Postoperative Care

• Thorough neurologic evaluation
• Wounds monitored for signs of infection
• Assess patients for post-operative ileus and be vigilant for SMA syndrome
• Routine clinical and radiographic evaluation of spinal alignment, hardware positioning, and arthrodesis
• Physical therapy for mobilization and conditioning

Outcome

• Bracing more effective than observation in preventing progression of scoliosis; may not have negative impact on patients' quality of life^45-47
• Patient satisfaction after surgical correction of AIS is often evaluated using Scoliosis Research Society-22 (SRS-22) domain scores
  • At 2 years, there is a statistically significant change in all the SRS domain scores, with improvement from preoperative status
  • However, there is low to moderate association between the change in SRS-22 scores and patient satisfaction with treatment
  • May be due to a ceiling effect in “satisfaction” domain or lack of responsiveness of the SRS-22 to measure clinically relevant changes in activity, pain, and mental health 2 years after correction of scoliosis in adolescent population ⁴⁸

Complications

Complications from Bracing

• Skin break down
• Non-compliance and curve progression

Complications from Surgery

• Intra-operative issues:
  • Blood loss
  • Neurologic injury
    • Direct trauma
    • Traction
    • Ischemia
  • Pneumothorax
  • Vascular Injury
• Post-operative issues:
  • Infection
  • Hematoma
  • Neurological deterioration
  • Pneumonia
  • Ileus
  • VTE
• Delayed issues:
  • Pseudarthrosis
  • Failed Instrumentation
  • Loss of curve correction
  • Adjacent level degeneration
  • Adjacent level deformity
  • Back pain

Pearls and Pitfalls

• Idiopathic scoliosis is a diagnosis of exclusion; other pathologies must be ruled out
• Early screening and referral followed by prompt treatment can minimize long-term physical and psycho-social sequelae
• Compliance with brace treatment is a major issue and must be addressed frequently and often with the family
• Save motion segments when possible
• Use osteotomies and releases to improve correction and limit hardware fatigue
• Use neurophysiologic monitoring to minimize peri-operative neurologic injury
• Maintain mean arterial pressure at 80 mm Hg during curve correction and instrumentation to minimize ischemic injury
• Restoration and maintenance of sagittal alignment critical for long-term success

References

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