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Introduction
  • Defined as idiopathic scoliosis in children 10 to 18 yrs
    • most common type of scoliosis
  • Epidemiology
    • incidence of 3% for curves between 10 to 20°
    • incidence of 0.3% for curves > 30°
    • 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
  • Pathophysiology
    • unknown
    • potential causes
      • multifactorial
      • hormonal (melatonin)
      • brain stem
      • proprioception disorder
      • platelet 
      • calmodulin
    • most have a positive family history
  • Prognosis
    • natural history
      • increased incidence of acute and chronic pain in adults if left untreated q 
      • curves > 90° are associated with cardiopulmonary dysfunction, early death, pain, and decreased self image
  • 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 kyphosisq
      • 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
        • poor prognosis with brace treatment associated with
          • poor in-brace correction
          • hypokyphosis (relative contraindication)
          • male
          • obese
          • noncompliant (effectiveness is dose related)
        • 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
 

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