Updated: 7/8/2022

Adolescent Idiopathic Scoliosis

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  • summary
    • Adolescent Idiopathic Scoliosis is a coronal plane spinal deformity which most commonly presents in adolescent girls from ages 10 to 18.
    • Diagnosis is made with full-length standing PA and lateral spine radiographs. 
    • Treatment can be observation, bracing, or surgical management depending on the skeletal maturity of the patient, magnitude of deformity, and curve progression.
  • Epidemiology
    • Incidence
      • most common type of scoliosis
        • incidence of 3% for curves between 10 to 20°
        • incidence of 0.3% for curves > 30°
    • Demographics
      • most commonly presents in children 10 to 18 yrs
      • 10:1 female to male ratio for curves > 30°
        • 1:1 male to female ratio for small curves
        • right thoracic curve most common
          • left thoracic curves are rare and indicate an MRI to rule out cyst or syrinx
  • Etiology
    • Pathophysiology
      • unknown
      • potential causes
        • multifactorial
        • hormonal (melatonin)
        • brain stem
        • proprioception disorder
        • platelet
        • calmodulin
        • abnormal development of neurocentral synchodrosis (NCS)
          • cartilaginous plate that forms between the centrum and posterior neural arches
          • closure occurs in characteristic order
            • cervical NCS by 5-6 years old
            • lumbar NCS by 11-12 years old
            • thoracic NCS by 14-17 years old
      • most have a positive family history
    • Curve Progression
      • risk factors for progression (at presentation)
        • curve magnitude
          • before skeletal maturity
            • > 25° before skeletal maturity will continue to progress
          • after skeletal maturity
            • > 50° thoracic curve will progress 1-2° / year
            • > 40° lumbar curve will progress 1-2° / year
        • remaining skeletal growth
          • younger age
            • < 12 years at presentation
          • Tanner stage (< 3 for females)
          • Risser Stage (0-1)
            • Risser 0 covers the first 2/3rd of the pubertal growth spurt
            • correlates with the greatest velocity of skeletal linear growth
          • open triradiate cartilage
          • peak growth velocity
            • is the best predictor of curve progression
              • in females it occurs just before menarche and before Risser 1 (girls usually reach skeletal maturity 1.5 yrs after menarche)
              • most closely correlates with the Tanner-Whitehouse III RUS method of skeletal maturity determination
            • if curve is >30° before peak height velocity there is a strong likelihood of the need for surgery
        • curve type
          • thoracic more likely to progress than lumber
          • double curves more likely to progress than single curves
  • Classification
    • King-Moe Classification
      • five part classification to describe thoracic curve patterns and help guide surgeons implanting Harrington instrumentation
      • link to King-Moe classification (not testable)
    • Lenke Classification
      • more comprehensive classification based on PA, lateral, and supine bending films
      • helps to decide upon which curves need to be included within the fusion construct
      • link to Lenke classification (not testable)
  • Presentation
    • School screening
      • patients often referred from school screening where a 7° curve on scoliometer during Adams forward bending test is considered abnormal
        • 7° correlates with 20° coronal plane curve
    • Physical exam
      • special tests
        • Adams forward bending test
          • axial plane deformity indicates structural curve
        • forward bending sitting test
          • can eliminate leg length inequality as cause of scoliosis
      • other important findings on physical exam
        • leg length inequality
        • midline skin defects (hairy patches, dimples, nevi)
          • signs of spinal dysraphism
        • shoulder height differences
        • truncal shift
        • rib rotational deformity (rib prominence)
        • waist asymmetry and pelvic tilt
        • cafe-au-lait spots (neurofibromatosis)
        • foot deformities (cavovarus)
          • can suggest neural axis abnormalities and warrant a MRI
        • asymmetric abdominal reflexes
          • perform MRI to rule out syringomyelia
  • Imaging
    • Radiographs
      • recommended views
        • standing PA and lateral
      • Cobb angle
        • > 10° defined as scoliosis
        • intra-interobserver error of 3-5°
      • spinal balance
        • coronal balance is determined by alignment of C7 plumb line to central sacral vertical line
        • sagittal balance is based on C7 plumb from center of C7 to the posterior-superior corner of S1
      • stable zone
        • between lines drawn vertically from lumbosacral facet joints
      • stable vertebrae
        • most proximal vertebrae that is most closely bisected by central sacral vertical line
      • neutral vertebrae
        • rotationally neutral (spinous process equal distance to pedicles on PA xray)
      • end vertebrae
        • end vertebra is defined as the vertebra that is most tilted from the horizontal apical vertebra
      • apical vertebrae
        • the apical vertebraeis the disk or vertebra deviated farthest from the center of the vertebral column
      • clavicle angle
        • best predictor of postoperative shoulder balance
    • MRI
      • should extend from posterior fossa to conus
      • purpose is to rule out intraspinal anomalies
      • indications to obtain MRI
        • atypical curve pattern (left thoracic curve, short angular curve, apical kyphosis)
        • rapid progression
        • excessive kyphosis
        • structural abnormalities
        • neurologic symptoms or pain
        • foot deformities
        • asymmetric abdominal reflexes
        • a syrinx is associated with abnormal abdominal reflexes and a curve without significant rotation
  • Treatment
    • Based on skeletal maturity of patient, magnitude of deformity, and curve progression
    • Nonoperative
      • observation alone
        • indications
          • cobb angle < 25°
        • technique
          • obtain serial radiographs to monitor for progression
      • bracing
        • indication
          • cobb angle from 25° to 45°
          • only effective for flexible deformity in skeletally immature patient (Risser 0, 1, 2)
          • goal is to stop progression, not to correct deformity
        • outcomes
          • 50% reduction in need for surgery with compliant brace wear of at least 13 hours a day
          • poor prognosis with brace treatment associated with
            • poor in-brace correction
            • hypokyphosis (relative contraindication)
            • male
            • obese
            • noncompliant (effectiveness is dose-related)
          • the number needed to treat (NNT) is four in highly compliant patients 
          • Sanders staging system
            • predicts the risk of curve progression despite bracing to >50 degrees in Lenke type I and III curves
            • uses anteroposterior hand radiograph and curve magnitude to assess risk of progression despite bracing
    • Operative treatment
      • posterior spinal fusion
        • indications
          • cobb angle > 45°
          • can be used for all types of idiopathic scoliosis
          • remains gold standard for thoracic and double major curves (most cases)
      • anterior spinal fusion
        • indications
          • best for thoracolumbar and lumbar cases with a normal sagittal profile
      • anterior / posterior spinal fusion
        • indications
          • larges curves (> 75°) or stiff curves
          • young age (Risser grade 0, girls <10 yrs, boys < 13 yrs)
            • in order to prevent crankshaft phenomenon
  • Techniques
    • Bracing
      • recommended for 16-23 hours/day until skeletal maturity or surgical intervention deemed necessary (actual wear minimum 12 hours required to slow progression)
      • brace types
        • curves with apex above T7
          • Milwaukee brace (cervicothoracolumbosacral orthosis)
            • extends to neck for apex above T7
        • apex at T7 or below
          • TLSO
          • Boston-style brace (under arm)
          • Charleston Bending brace is a curved night brace
      • bracing success is defined as <5° curve progression
      • bracing failure is defined
        • 6° or more curve progression at orthotic discontinuation (skeletal maturity)
        • absolute progression to >45° either before or at skeletal maturity, or discontinuation in favor of surgery
      • skeletal maturity is defined as
        • Risser 4
        • <1cm change in height over 2 visits 6 months apart
        • 2 years postmenarchal
    • Posterior spinal fusion
      • fusion levels
        • goals
          • fusion should include enough levels to adequately maintain sagittal and coronal balance while being as minimal as safely possible to preserve motion
          • typical fusion from proximal end vertebra to one or two levels cephalad to the stable vertebra
          • double and triple major curves fuse to the distal end vertebra
        • Harrington technique
          • recommends one level above and two levels below the end vertebrae if these levels fall wilthin the stable zone
        • Moe technique
          • recommends fusion to the neutral vertebrae
        • Lenke technique
          • recommends including all major curves in the fusion and minor curves that are not flexible or are kyphotic
        • L5 level
          • Cochran found increase incidence of low back pain with fusion to L5, and to a lesser extent L4.
            • therefore, whenever possible, avoid fusion to L4 and L5
        • pelvis
          • it is almost never required to fuse to the pelvis in idiopathic scoliosis
      • pedicle screw fixation
        • screw insertional torque correlates with resistance to screw pullout
        • resistance to screw pullout increases by
          • undertapping by 1mm
      • curve correction
        • segmental pedicle screw fixation allows increased coronal plane correction while lessening the need for anterior releases
    • ASF with instrumentation
      • advantage
        • better correction while saving lumbar fusion levels
      • disadvantage
        • increased risk of pseudarthrosis when thoracic hyperkyphosis is present
      • fusion levels
        • typically fuse from end vertebra to end vertebra
    • Neurologic Monitoring
      • monitoring with somatosensory-evoked potentials (SSEPs) and/or motor-evoked potentials (MEPs) is now the standard of care
        • motor-evoked potentials can provide an intraoperative warning of impending spinal cord dysfunction
      • neurologic event defined as drop in amplitude of > 50%
      • if neurologic injury occurs intraoperatively consider
        • check for technical problems
        • check blood pressure and elevate if low
        • check hemoglobin and transfuse as necessary
        • lessen/reverse correction
        • administer Stagnaras wake up test
        • remove instrumentation if the spine is stable
  • Complications
    • Neurologic injury
      • paraplegia is 1:1000
      • increased risk with kyphosis, excessive correction, and sublaminar wires
    • Pseudoarthrosis (1-2%)
      • presents as late pain, deformity progression, and hardware failure
        • an asymptomatic pseudarthrosis with no pain and no loss of correction should be observed
    • Infection (1-2%)
      • presents as late pain
      • incision often looks clean
      • Propionibacterium acnes most common organism for delayed infection (requires 2 weeks for culture incubation)
      • attempt I&D with maintenance of hardware if not loose and within 6 months
    • Flat back syndrome
      • early fatigability and back pain due to loss of lumbar lordosis
      • rare now that segmental instrumentation addresses sagittal plane deformities
        • decreased incidence with rod contouring in the sagittal plane and compression/distraction techniques
      • treat with revision surgery utilizing posterior closing wedge osteotomies
        • anterior releases prior to osteotomies aid in maintenance of correction
    • Crankshaft phenomenon
      • rotational deformity of the spine created by continued anterior spinal growth in the setting of a posterior spinal fusion
        • can occur in very young patients when PSF is performed alone and the anterior column is allowed continued growth
        • avoided by performing anterior diskectomy and fusion with posterior fusion in very young patients
    • SMA syndrome (superior mesenteric artery [SMA] syndrome)
      • compression of 3rd part of duodenum due to narrowing of the space between SMA and aorta
      • SMA arises from anterior aspect of aorta at level of L1 vertebrae
      • presents with symptoms of bowel obstruction in first postoperative week
        • associated with electrolyte abnormalities
        • nausea, bilious vomiting, weight loss
      • risk factors
        • height percentile <50%; weight percentile < 25%
        • sagittal kyphosis
      • treat with NG tube and IV fluids
    • Hardware failure
      • late rod breakage can signify a pseudarthrosis
  • Prognosis
    • Natural history
      • increased incidence of acute and chronic pain in adults if left untreated
      • curves > 90° are associated with cardiopulmonary dysfunction, early death, pain, and decreased self image

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(OBQ18.41) The neurocentral synchondrosis (NCS) develops between which 2 spinal elements and closes in which order?

QID: 212937

Centrum & anterior neural arches; cervical, thoracic, lumbar



Centrum & anterior neural arches; cervical, lumbar, thoracic



Centrum & posterior neural arches; cervical, thoracic, lumbar



Centrum & posterior neural arches; lumbar, thoracic, cervical



Centrum & posterior neural arches; cervical, lumbar, thoracic




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(SBQ18SP.32) A 13-year-old female presents to clinic after being told that she has scoliosis. She has no pain and has had no treatment up to this point. Figure A shows her radiograph with a 32° curve. An MRI showed no spinal cord abnormalities. What is the most appropriate treatment and expected outcome given her age and degree of scoliosis?

QID: 211454

Observation with a 100% chance of progression to >50° deformity



Rigid TLSO for 2 hours/day with a 75% decrease in the need for surgery



Rigid TLSO for 13 hours/day with a 50% decrease in the need for surgery



Rigid TLSO for 24 hours/day with a 100% decrease in the need for surgery



Posterior spinal fusion



L 1 A

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(OBQ14.38) A 16-year-old female with adolescent idiopathic scoliosis undergoes posterior spinal fusion with instrumentation. The thoracic pedicle screws were placed using a tap 1 mm smaller than the screw diameter and a straightforward trajectory that runs parallel to the superior endplate. This techniques allows for which of the following:

QID: 5448

Anatomic placement of the screws.



Increased depth insertion of the screws.



Increased maximal insertional torque.



Decreased resistance to screw pullout.



Decreased stability of the construct.



L 3 C

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(OBQ13.138) A 12-year-old girl who is 3 months postmenarchal undergoes full-time brace treatment for scoliosis. The posteroanterior radiograph (Figure A ) taken at that time reveals a right thoracic curve measures 28 degrees, and the left lumbar curve measures 23 degrees. At age 15, after 3 years of bracing, a repeat posteroanterior radiograph is obtained, now revealing a right thoracic curve measuring 11 degrees and the left lumbar curve measuring 19 degree, and Risser 4. Which statement best represents the indicated course of action in this patient?

QID: 4773

Discontinuation of bracing as she has reached skeletal maturity.



Continue full-time bracing until skeletal maturity.



Continue nocturnal bracing until skeletal maturity.



Posterior spinal fusion.



MRI of the cervical, thoracic and lumbar spine.



L 4 B

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(OBQ13.61) The 'Risser sign' is one of the most commonly used markers for skeletal maturation and growth potential in patients with adolescent idiopathic scoliosis. What 'Risser sign' has been shown to correlate with the greatest velocity of skeletal linear growth?

QID: 4696

Risser 0



Risser I



Risser II



Risser III



Risser IV



L 4 B

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(SBQ12SP.34) A 17-year-old girl with severe adolescent idiopathic scoliosis requires an osteotomy in the lumbar spine to correct her saggital imbalance. Figure A shows the pre-operative plan and surgical technique for this procedure. What would be the most common complication with this type of spinal column osteotomy?

QID: 3732

Spinal cord ischemia



Descending aorta injury









Neurologic deficit



L 5 C

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(OBQ12.144) Skeletal maturity is an important variable in the progression of idiopathic scoliosis. Figures A-E are radiographs showing varying stages of skeletal maturity. The patient represented by which Figure would be expected to have the highest risk of progression of an idiopathic scoliotic curve?

QID: 4504
















L 2 B

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(OBQ12.176) A 12-year-old female is referred to the office by a community orthopaedic surgeon concerned that her shoulders appear to be at different heights. With Adam's forward bending, she is noted to have a significant right thoracic rib prominence. She denies pain. A detailed neurological examination reveals no abnormalities. Radiographs of her spine show an apex left lumbar curve measuring 32 degrees and an apex right thoracic curve measuring 28 degrees. She had her first menses last month and her Tanner-Whitehouse staging is consistent with an adolescent steady state. The most appropriate treatment would be?

QID: 4536

Posterior spinal fusion



Spinal manipulations



Observation and referral to an endocrinologist



Thoracolumbosacral orthosis



Halo-gravity traction



L 2 B

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(OBQ12.178) The orthosis shown in Figure A is indicated for the treatment of the spinal deformity shown in which of the following radiographs?

QID: 4538

Figure B



Figure C



Figure D



Figure E



Figure F



L 1 B

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(OBQ12.70) Which of the following methods of determining skeletal maturity correlates most closely with the curve acceleration phase for children with idiopathic scoliosis?

QID: 4430

Lenke classification method



Greulich and Pyle method



Oxford method



Tanner-Whitehouse III



Risser sign



L 5 C

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(OBQ11.49) A 13-year-old girl is referred to the orthopedic clinic for evaluation of scoliosis. She denies back pain and states she began her menses 3 months ago. On Adams forward bending, she measures 6 degrees. She has 5 of 5 motor strength in all muscles groups in her lower extremities and symmetric patellar and Achilles reflexes. A standing PA and lateral radiograph is shown in Figures A and B. All of the following should be performed as part of her evaluation EXCEPT:

QID: 3472

Evaluation of leg lengths



Assessment of abdominal reflexes



Evaluation of waist asymmetry



Evaluation for café-au-lait spots






L 1 C

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(SBQ09SP.17) In patients with adolescent idiopathic scoliosis, bracing is indicated in which of the following conditions:

QID: 3380

Any patient with a curve of greater than 25 degrees



A 11- year-old boy boy with a Cobb angle curve of 50 degrees



A premenarchal girl with a Cobb angle curve of 30 degrees



A growing child with 6 degrees of progression with a 12 degree curve



A girl who is Risser 4, Sanders 7, with a 30 degree curve.



L 2 B

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(SAE07PE.98) A 12-year-old girl who is Risser stage 3 has had intermittent mild midback pain for the past 4 weeks. The pain is worse after prolonged sitting and after carrying a heavy backpack at school. She occasionally takes acetaminophen, but the pain does not limit sport activities. Examination reveals a mild right rib prominence during forward bending. Neurologic examination is normal. Radiographs show a 20-degree right thoracic scoliosis with no congenital anomalies or lytic lesions. Management should consist of

QID: 6158

back muscle stretching and reduced weight in the backpack.



consultation with a pain management specialist.



MRI of the thoracic spine.



a technetium Tc 99m bone scan.



a thoracolumbosacral orthosis.



L 2 E

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(SAE07PE.25) What risk factor is most associated with progression of idiopathic scoliosis to a curve requiring surgery?

QID: 6085

Curve magnitude of more than 20 degrees at menarche



Curve magnitude of more than 30 degrees at the peak height velocity



Curve magnitude of more than 30 degrees at skeletal age 12 years



Curve magnitude of more than 30 degrees at Risser grade 2



Curve flexibility of less than 50% at Risser grade 2



L 2 E

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(OBQ07.79) A 12-year-old female presents with a left thoracic rib prominence. Physical exam shows absent abdominal reflexes in the upper and lower quadrants on the left side, but present on the right. A PA standing radiograph is shown in Figure A. What is the next step in management?

QID: 740

Observation with repeat radiographs in 6 months



Bracing with a thoraco-lumbar-sacral orthosis



Magnetic resonance imaging (MRI)



Posterior spinal fusion with instrumentation



Anterior and posterior spinal fusion with instrumentation



L 1 C

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(SBQ06SN.19) An isolated long-segment instrumented posterior spinal fusion is considered in which of the following clinical situations?

QID: 1704

A 13-year old female, Risser 3, with adolescent idiopathic scoliosis (AIS) and a Cobb angle of 55 degrees



A 5-year old male, with juvenile idiopathic scoliosis (JIS) and a Cobb angle of 55 degrees



A 2-year old female with infantile idiopathic scoliosis (IIS), a flexible curve with a Cobb angle of 35°, and a RVAD of 25°



A 7-year-old with a progressive spinal deformity. Imaging demonstrates a T9 failure of formation with contralateral segmentation failure



A 13-year old female Risser 2, with AIS and a Cobb angle of 27 degrees



L 2 D

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(OBQ06.17) In the treatment of thoracolumbar idiopathic scoliosis using an anterior single rod technique with interbody cages, which of the following variables has been associated with pseudoarthrosis.

QID: 28

Thoracic curve coronal correction of > 40%



Thoracolumbar/lumbar curve coronal correction > 50%



Smaller adolescents (<50 kg)



Failure to maintain lumbar lordosis of > 45 degrees



Thoracic hyperkyphosis (>40 degrees )



L 4 D

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(OBQ06.35) A mother and her 16-year-old daughter present to your clinic because the daughter has noticed asymmetries in her back. She has no back pain and no neurologic symptoms. She is two years post-menarcheal. After a complete history and physical, you order PA thoracolumbar radiograph, which is seen in figure A. The cobb angle is 38 degrees. When discussing the natural history of the disease, you tell the family they should expect:

QID: 146

difficulty with vaginal child birth in the future.



decreased pulmonary function in the future



to undergo an MRI to rule out any underlying neurologic pathology, as this is an abnormal curve



an increased risk of chronic back pain over her lifetime



this curve magnitude has the highest curve progression rate without operative intervention



L 1 C

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(OBQ04.144) When compared to normal controls, adults with untreated idiopathic scoliosis and a Cobb angle of greater than 60 degree at the time of skeletal maturity have a higher rate of which of the following?

QID: 1249

Acute and chronic back pain



Premature death






Clinical depression



Limitation in activities of daily living



L 2 C

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Evidence (126)
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