Spinal Deformity

Question 1

What is a coronal plane imbalance?

Answer 1

Defined as lateral deviation of the normal vertical line of the spine > 10 degrees

Question 2

What is a sagittal plane imbalance?

Answer 2

defined as radiographic sagittal imbalance of >5cm

Question 3

Where is the location of idiopathic vs degenerative scoliosis?

Answer 3

▪ idiopathic scoliosis is more common in the thoracic spine

degenerative scoliosis occurs more commonly in the lumbar spine.

Question 4

What is the patho-anatomy of degenerative scoliosis?

Answer 4

◦ degenerative scoliosis results from the asymmetric degeneration of disc space and/or facet joints in the spine.

may occur in the coronal plane (scoliosis) or the sagittal plane (kyphosis/lordosis)

factors contributing to loss of sagittal plane balance:

• osteoporosis
• preexisting scoliosis
• iatrogenic instability
• degenerative disc disease

Question 5

What is the prognosis of degenerative scoliosis?

Answer 5

worse prognosis with

if symptoms progress to the side of curve convexity

sagittal plane imbalance

Question 6

What is the most reliable predictor of clinical symptoms in adults with spinal deformity?

Answer 6

sagittal plane balance is the most reliable predictor of clinical symptoms in adults with spinal deformity

Question 7

What are the predictors of progression in scoliosis?

Answer 7

• depends on curve type

thoracic > lumbar > thoraco-lumbar > double major

right thoracic curves (1 degree per year)

right lumbar curves (0.5 degree per year)

thoracolumbar curves (0.25 degree per year)

• depends on curve magnitude

curves <30 deg rarely progress

curves >50 deg commonly progress

• additional risk factors for progression
• increased risk when inter-crestal line is below L4-5
• preexisting rotational changes exist

Question 8

What is the difference between classic neurogenic claudication and neurogenic claudication in patients with scoliosis?

Answer 8

unlike classic claudication, patients with scoliosis + stenosis do not obtain relief with sitting / forward flexion

Question 9

What is C7 plumb line (C7PL)?

Answer 9

From center of C7 to postero-superior corner of S1

Question 10

Treatment Algorithm

Answer 10

Nonoperative

Observation with non-operative modalities

Indications: coronal curves < 30 degrees rarely progress

• NSAIDS
• tricyclic antidepressants help with sleep disturbance
• Physical therapy
• includes core strengthening (walking, cycling, swimming, selected weight lifting)
• Corticosteroid injections and nerve root blocks
• diagnostic and therapeutic
• Bracing: may slow progression and increase comfort

Operative surgical curve correction with instrumented fusion

• curve > 50 degrees of the following type
• sagittal imbalance
• curve progression
• intractable back pain or radicular pain that has failed nonsurgical efforts
• cosmesis (controversial)
• cardiopulmonary decline

thoracic curves >60deg affect pulmonary function tests

thoracic curves >90deg affect mortality

techniqueposterior only curve correction and instrumented fusionindications

thoracic curves > 50 degrees

most double structural curves > 50 degrees

selecting technique is patient and surgeon specific

combined anterior/posterior curve correction with instrumented fusionindications

isolated thoracolumbar

isolated lumbar curves

extremely rigid curves requiring anterior release

Question 11

What are the Goals of surgery in scoliosis?

Answer 11

1. Restore spinal balance

sagittal plane balance is the most reliable predictor of clinical symptoms postoperatively

can be measured by C7 plumb line (C7 sagittal vertical axis)

correction of sagittal plane deformity requires intense preoperative planning

correct lumbar lordosis to normal anatomic range:

PI = LL+/- 9°

LL ≤ 45° - TK - PI

most predictive of sagittal plane correction maintenance

2. relieve pain

3. obtain solid fusion

Question 12

What to extend montage fusion to ilium in surgical correction of spinal deformity?

Answer 12

▪ Indications: consider this if sacrum is included in fusion involving >3 levels

Question 13

most significant risk factor for a major perioperative complication during posterior spinal fusion for adult spinal deformity correction

Answer 13

Age > 60

Question 14

What is the incidence of major complications following adult spinal deformity surgery?

Answer 14

10-15%

Question 15

In a patient with adult degenerative scoliosis, what is the radiographic parameter that most strongly correlates with visual analog pain scores and disability?

Answer 15

Thoracolumbar kyphosis

Question 16

How to determine the sagittal vertical axis offset or sagittal imbalance?

Answer 16

Sagittal vertical axis offset, or sagittal imbalance, is determined by measuring the distance from the C7 plumb line (dropped from the center of the C7 vertebral body) to the posterior-superior corner of the S1 vertebral body on a standing lateral radiograph

Question 17

What is major advantage of extending the fusion to the sacrum as opposed to ending at L5 in patient with spinal deformity?

Answer 17

Improved correction and maintenance of sagittal balance

Question 18

What is the most common type of curve in AIS?

Answer 18

right thoracic curve most common

Question 19

What to do with left thoracic curves?

Answer 19

are rare and indicate an MRI to rule out cyst or syrinx

Question 20

What is the Pathophysiology of AIS?

Answer 20

◦ unknown

potential causes

multifactorial

hormonal (melatonin)

brain stem

proprioception disorder

platelet

calmodulin

abnormal development of neurocentral synchondrosis (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

Question 21

What is the prognosis of AIS?

Answer 21

▪ 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

Question 22

What are the risk factors for progression (at presentation)?

Answer 22

1- 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

2- 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 tri-radiate 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

3- Curve type

thoracic more likely to progress than lumber

double curves more likely to progress than single curves

Question 23

What are the special tests for AIS?

Answer 23

▪ 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

Mid-line 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

Café-au-lait spots (neurofibromatosis)

Foot deformities (cavo-varus): can suggest neural axis abnormalities and warrant a MRI

Asymmetric abdominal reflexes: perform MRI to rule out syringomyelia

Question 24

What are the indications to obtain MRI in the setting of AIS?

Answer 24

• 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

Question 25

What is the treatment of AIS based on?

Answer 25

1- skeletal maturity of patient 2- magnitude of deformity 3- curve progression

Question 26

What is the treatment algorithm for AIS?

Answer 26

**1- observation alone:** cobb angle \< 25° **2- bracing:** 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) *_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 **3- Operative treatment:** posterior spinal fusionindications 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 fusionindications larges curves (\> 75°) or stiff curves young age (Risser grade 0, girls \<10 yrs, boys \< 13 yrs) in order to prevent crankshaft phenomenon

Question 27

What are the recommendations for bracing in AIS?

Answer 27

recommended for 16-23 hours/day until skeletal maturity or surgical intervention deemed necessary (actual wear minimum 12 hours required to slow progression) brace typesCurves with apex above T7Milwaukee 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

Question 28

How is bracing failure defined?

Answer 28

▪ 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

Question 29

Skeletal maturity is defined as

Answer 29

▪ Risser 4 \< 1cm change in height over 2 visits 6 months apart 2 years post-menarchal

Question 30

What are the complications of surgery for AIS?

Answer 30

**Neurologic injury**: paraplegia is 1:1000 increased risk with kyphosis, excessive correction, and sub-laminar wires **Pseudo-arthrosis (1-2%)** presents as late pain, deformity progression, and hardware failure an asymptomatic pseudo-arthrosis 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 fatiguability 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

Question 31

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

Answer 31

The neurocentral synchondrosis (NCS) develops between the centrum and posterior neural arches. Closure occurs first in the cervical spine, followed by the lumbar spine and then the thoracic spine. The NCS is a cartilaginous growth plate that has been implicated as a potential cause of adolescent idiopathic scoliosis (AIS). The closure of the synchondroses is dependent upon the location of the vertebra: the cervical NCS closes by 5-6 years old, then the lumbar NCS closes by 11-12 years old, and finally the thoracic NCS closes by 14-17 years old.

Question 32

What Risser sign shown to correlate with the greatest velocity of skeletal linear growth?

Answer 32

Risser 0 Risser 0 covers the first 2/3rd of the pubertal growth spurt and correlated with the greatest velocity of skeletal linear growth.

Question 33

Most common complication of pedicle substraction osteotomy?

Answer 33

Non union

Question 34

Method of determining skeletal maturity that correlates most closely with the curve acceleration phase for children with idiopathic scoliosis?

Answer 34

Tanner-Whitehouse III

Question 35

What increased the risk of non union in patient with AIS treated with anterior approach?

Answer 35

Thoracic hyperkyphosis \> 40 degrees