Adolescent Idiopathic Scoliosis

Introduction

• Scoliosis is defined as an abnormal coronal plane curvature of the spine, usually appearing as a C-shaped or S-shaped curve.

• A spinal curve measuring greater than ten degrees is considered scoliosis.

• Hippocrates (four hundred sixty to three hundred seventy-seven before Christ) was the first to describe abnormal spinal curvature and coined the term scoliosis, derived from the Greek word skolios, meaning crooked.

• Claudius Galen (one hundred thirty-one to two hundred one after Christ) classified spinal deformities into scoliosis, kyphosis, and lordosis.

• The Growing Spine Study Group and the Children Spine Study Group define early onset scoliosis as any spinal deformity present before ten years of age, regardless of cause.

• Adolescent idiopathic scoliosis refers to abnormal spinal curvature developing during the growth spurt between ten and eighteen years of age.

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Idiopathic Scoliosis

• Idiopathic scoliosis has no identifiable cause and is not associated with other systemic diseases.

• Subtypes according to the Scoliosis Research Society:

  1. Infantile idiopathic scoliosis: younger than three years

  2. Juvenile idiopathic scoliosis: four to ten years

  3. Adolescent idiopathic scoliosis: ten to eighteen years

• Curve severity:

  • Mild: less than twenty-five degrees

  • Moderate: twenty-five to fifty degrees

  • Severe: greater than fifty degrees

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Epidemiology and Demographics

• Most common form of scoliosis.

• Positive family history is frequently present.

• Affects up to four percent of adolescents.

• Incidence:

  • Curves between ten and twenty degrees: approximately three percent

  • Curves greater than thirty degrees: approximately zero point three percent

• Sex distribution:

  • Small curves: equal male to female ratio

  • Curves greater than thirty degrees: female predominance of approximately ten to one

• Curve patterns:

  • Thoracic curves are more common than lumbar curves

  • Most common pattern is a right thoracic curve

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Pathophysiology

• Exact cause remains unknown.

• Proposed contributing factors include:

  • Genetic influences

  • Neurological factors

  • Hormonal and metabolic abnormalities

  • Skeletal growth imbalance

  • Biomechanical forces

  • Environmental and lifestyle factors

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Clinical Presentation and Examination

History

• Age at first detection of deformity

• Rate and pattern of progression

• Perinatal and developmental history

• Family history of scoliosis

• Menstrual history in female patients

Clinical Presentation

• Commonly detected due to cosmetic concerns raised by parents

• Often identified during school screening programs

• A scoliometer reading greater than seven degrees during the Adams forward bending test correlates with a coronal plane curve of approximately twenty degrees

• Typically painless

• Neurological symptoms are uncommon

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Physical Examination

General Inspection

• Shoulder asymmetry or scapular prominence

• Deviation of the spine from the midline

• Head not centered over the pelvis

• Rib or lumbar prominence on one side

• Pelvic asymmetry and uneven waistline

• Asymmetric skin creases

• Inability to stand erect without compensation

Associated Findings

• Café-au-lait spots suggesting neurofibromatosis

• Nevi

• Cavovarus foot deformities suggesting neural axis abnormalities and warranting magnetic resonance imaging

• Serial height measurements to identify peak height velocity

• Limb length discrepancy causing compensatory scoliosis

Spine Examination

• Midline skin abnormalities such as dimples or hairy patches suggesting spinal dysraphism

• Rib rotational deformity

• Adams forward bending test to assess structural curves

• Sitting forward bending test to exclude limb length discrepancy

Neurological Examination

• Motor and sensory assessment

• Deep tendon reflexes

• Abdominal reflexes

• Assessment for clonus, Hoffmann sign, and Babinski response

• Gait analysis

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Adams Forward Bending Test

• Most reliable clinical screening test for scoliosis

• Patient bends forward with arms hanging freely

• Symmetry of the trunk is assessed

• Rib or lumbar hump suggests structural scoliosis

• Scoliometer may be used to measure trunk rotation

• Trunk rotation less than seven degrees is considered normal

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Curve Progression

Risk Factors

1. Curve magnitude at presentation

2. Curve pattern

3. Remaining skeletal growth

Assessment of Skeletal Maturity

• Tanner staging

• Risser staging

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Risser Staging

• Assesses remaining growth potential using pelvic radiographs

• Based on ossification of the iliac apophysis from lateral to medial

Stages:

• Risser zero: no ossification, significant growth remaining

• Risser one: up to twenty-five percent ossification

• Risser two to four: progressive ossification

• Risser five: skeletal maturity

Natural History After Maturity

• Thoracic curves greater than fifty degrees progress one to two degrees per year

• Lumbar curves greater than forty degrees progress one to two degrees per year

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Imaging: Radiographs

• Standing posteroanterior and lateral radiographs recommended

• Images should include the iliac crest distally and cervical spine proximally

• Supine side-bending radiographs used for surgical planning

• Radiographic assessment includes:

  • Cobb angle

  • Apical vertebra

  • End vertebrae

  • Neutral vertebrae

  • Stable vertebra

  • Curve location and direction

  • Risser sign

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Radiographic Parameters

Cobb Angle

• Scoliosis defined as curvature greater than ten degrees

• Measurement error ranges from three to five degrees

Spinal Balance

• Coronal balance assessed by alignment of the seventh cervical vertebra plumb line with the central sacral vertical line

• Sagittal balance assessed by the relationship of the seventh cervical vertebra to the posterior superior corner of the first sacral vertebra

Clavicle Angle

• Best predictor of postoperative shoulder balance

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Vertebral Definitions

• Apical vertebra: most laterally deviated and rotated vertebra

• End vertebrae: most tilted vertebrae at the upper and lower ends of the curve

• Neutral vertebra: first vertebra without rotation above and below the apex

• Stable vertebra: vertebra most closely bisected by the central sacral vertical line

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Vertebral Rotation: Nash–Moe Method

• Estimates vertebral rotation based on pedicle displacement

• Grades range from zero to four

• Advantages:

  • Simple and reproducible

• Limitations:

  • Provides only an approximate estimate of rotation

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Imaging: Magnetic Resonance Imaging

• Imaging extends from posterior cranial fossa to conus medullaris

• Used to detect intraspinal abnormalities

• Indications include:

  • Left thoracic curve

  • Rapid progression

  • Excessive kyphosis

  • Neurological symptoms

  • Structural abnormalities

  • Foot deformities

  • Asymmetric abdominal reflexes

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Classification Systems

• Schulthess classification

• Ponseti and Friedman classification

• King–Moe classification

• Lenke Classification (most widely used)

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Lenke Classification System

• Developed to overcome limitations of earlier systems

• Uses standing, lateral, and bending radiographs

• Three-step approach:

  1. Identification of primary curve

  2. Lumbar modifier determination

  3. Thoracic sagittal modifier assignment

• Defines forty-two distinct curve patterns

• Guides surgical fusion levels

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Management Considerations

• Remaining growth potential

• Curve magnitude

• Curve pattern

• Sex

• Genetic risk profiling

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Non-Surgical Management

Observation

• Indicated for curves less than twenty-five degrees

• Serial radiographic monitoring:

  • Mild curves: every six to twelve months

  • Moderate curves: every four to six months

Bracing

• Indicated for progressive curves between twenty-five and forty degrees in skeletally immature patients

• Full-time or part-time wear depending on curve and compliance

• Common orthoses:

  • Cervicothoracolumbosacral orthosis

  • Thoracolumbosacral orthosis

  • Night-time bending braces

• Successful bracing reduces surgical requirement by approximately fifty percent

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Surgical Management

Goals of Surgery

• Correct deformity

• Maintain coronal and sagittal balance

• Preserve pulmonary function

• Minimize pain and morbidity

• Optimize long-term function

Indications

• Progressive curves greater than forty degrees in skeletally immature patients

• Curves greater than fifty degrees in skeletally mature patients

Surgical Techniques

• Posterior spinal instrumentation and fusion (most common)

• Anterior spinal instrumentation and fusion

• Combined anterior and posterior fusion for severe or rigid curves

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Complications

• Neurological injury (approximately one in one thousand)

• Excessive blood loss

• Pseudarthrosis

• Superior mesenteric artery syndrome

• Implant-related complications

• Infection, often presenting late

• Flat back syndrome

• Crankshaft phenomenon in immature patients

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Conclusion

• Adolescent idiopathic scoliosis is a complex three-dimensional spinal deformity.

• Early detection, accurate assessment, and individualized management are essential.

• Advances in classification, bracing, and surgical techniques have significantly improved outcomes.

• Long-term success depends on appropriate patient selection, meticulous technique, and structured follow-up.