منو منو

Adolescent Idiopathic Scoliosis

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

  • Emergency department visits

    • most often for minor medical complaints 

      • associated with older age at the time of surgery and more fusion levels 

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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