IDIOPATHIC SCOLIOSIS

Aetiology

Structural differences

· all thought to be effect rather than cause

Intervertebral disc

· decrease in glycosoaminoglycan content in nucleus pulposis with increase in collagen content found

· changes also present in scoliosis due to other causes

Vertebral body

· structures on concave side hypoplastic

· structures on convex side hypertrophied

Paravertebral musculature

· differences in muscle fibres on either side of curve

Ligaments and tendons

· collagen metabolism found to be normal

· posterior longitudinal ligament thickened

Endocrine system

· patients with idiopathic scoliosis often taller

· growth hormone levels found to be normal

· studies on somatomedin levels conflicting but significant differences found

Postural equilibrium

· abnormalities in the vestibular system in the brain stem in scoliotics have been demonstrated

· scoliosis induced in bipedal rats by destruction of brain stem

· proof not conclusive

Neurotransmitter

· scoliosis experimentally produced by removing pineal gland in chickens

· no specific neurotransmitter defect identified

Genetics

· increased incidence in affected relatives found

· sharp drop from first-, second-, and third-degree relatives

· chance that child will have scoliosis with affected relative

· mother and father - 80%

· mother and sister - 20%

· mother - 10%

· sister - 3%

· indicative of multifactorial mode of inheritance

· other studies have disputed a genetic explanation

pathogenesis

Lordosis

· may be biomechanical initiator of deformity

· thoracic lordosis lies in front of normal axis of rotation

· this causes rotation of lordotic section in flexion

· changes of vertebral shape are effects secondary to rotation of lordosis

· right-sided prevalence explained

· normal asymmetry of spine to right identified

· probably due to descending aorta on left

· increased incidence in girls explained

· normal flattening of thoracic kyphosis age 12

· corresponds to female growth spurt

Classification

· classified according to time of onset

Scoliosis Research Society

Infantile

· curve occurs between birth and age 3

Juvenile

· curve occurs between age 3 and onset of puberty (about age 10)

Adolescent

· curve occurs between onset of puberty (about age 10) and cessation of skeletal growth (about age 20)

Dickson

· some problems with SRS classification

· juvenile-onset is heterogenous group and may not exist

· early juvenile may actually be missed infantile

· no clear distinction between late juvenile and early adolescent

· alternative classification proposed

Early onset

· curve occurs before age 5 yrs

Late onset

· curve occurs after age 5 yrs

Adolescent idiopathic scoliosis

epidemiology

· overall prevalence is 25 per 1000

· small curves are more common

curve severity prevalence

5^o 77 per 1000

10^o 23 per 1000

20^o 5 per 1000

30^o 2 per 1000

40^o 1 per 1000

· various curve patterns (in decreasing incidence)

· right thoracic

· double major - right thoracic and left lumbar

· thoracolumbar

· double major - right thoracic and left thoracic

· left lumbar

Natural history

Progression

· progression is signified by an increase in the curvature

· difficult to accurately quantify

· Cobb's angle lacks exact precision (variations of +/- 3^o between examiners)

· mild postural and positional changes can affect measured curvature

· progression is defined as

· two sequential x-rays showing more than 5^o of change OR

· a minimum increase of 10^o

· not all curves progress

progression incidence

improved 10%

unchanged 20%

<10^o 30%

10-20^o 20%

>20^o 20%

Prognostic factors

· most likely to progress

· female sex

· young age

· skeletally immature (early Risser)

· sexually immature (premenarche)

· significant rotation

· single thoracic curve

· large curve

Growth potential

· rapid progression occurs during rapid growth

· growth potential evaluated by a number of factors

1. historical

· age

· menarche

· growth spurt (outgrowing shoes and clothes)

2. clinical

· height

· Tanner’s sign (breasts and pubic hair)

3. radiological

· Risser

· hand (Gruber and Pyle)

Menarche

· distinct milestone

· actual age varies (range 11-15 yrs)

· menarche is late event in puberty

· growth spurt begins 12-18 months before puberty

· risk of progression unrelated to age of menarche

· clearly related to whether menarche has occurred

· risk prior to menarche - 50%

· risk after menarche - 20%

Risser sign

· progressive ossification of the iliac crest

· indicates skeletal maturity and physiological age

· progression 3 times more likely if Risser II or less

· risk at or before Risser II - 50%

· risk after Risser II - <20%

Age at diagnosis

· significant if chronological and physiological age consistent

· if so, risk of progressing 10^o or more is 3 times greater under age 12

Sex

· incidence of mild scoliosis relatively equal

· larger curves more common in females

curve F:M ratio

<10^o 1:1

10-19^o 2:1

20-30^o 5:1

>30^o 10:1

· risk of progression greater in preteen females but equal in adolescents

Curve severity

· larger curves are more likely to progress

· curve progression usually at 1^o per mth

curve risk

20^o 20%

30^o 60%

50^o 90%

Curve pattern

· varying risks according to curve location

location risk

thoracic high

double major high

thoraco-lumbar intermediate

lumbar low

Lonstein pogression factor

· devised by Lonstein and Carlson

· attempt to quantify risk factors

· PF = (curve - 3 x Risser) / chronological age

· progression risk curve can be constructed

· PF 1 = 20% risk

· PF 1.5 = 50% risk

· PF 2 = 80% risk

· PF 2.5 = 100% risk

Progression after skeletal maturity

· long-term study by Weinstein and Ponsetti

· showed that 70% of curves progress after skeletal maturity

· progress an average of 20^o

· curves less than 30^o tend not to progress

· curves of 50-75^o usually progress

· esp. thoracic curves

· rate of 1^o per year

· risk factors in thoracic curves

· vertebral rotation (Mehta angle > 30^o, apical rotation > 30^o)

· risk factors in lumbar spine

· vertebral rotation

· direction of curve (right)

· position of L5 (not below intercrest line)

Untreated scoliosis

Back pain

Thoracic

· slightly increased incidence of back pain

· unrelated to magnitude of curve

· usually not a significant problem

· exception is lumbar curve > 45^o

· esp. with substantial apical rotation

Cardiopulmonary function

· affected in thoracic curves

· inverse correlation between magnitude of curve and

· forced vital capacity (FVC)

· forced expiratory volume in one second (FEV₁)

· may develop restrictive lung disease

· may lead to

· respiratory failure

· cor pulmonale and right heart failure

· respiratory function is reduced by

· nil with curve < 60^o

· 1/3 with curve 60-100^o

· 1/2 with curve > 100%

· cor pulmonale occurs

· in 40s and 50s

· if curve > 80^o

· problems more severe with early-onset deformities

· affects development of lungs

Mortality

· only increased if curve >100^o

Cosmesis

· appearance is major concern in most patients

Psychosocial effects

· severe psychosocial problems may occur

· especially in adolescents

clinical features

History

· how curve was detected

· presence of progression

· associated complaints

· pain

· neurological symptoms

· respiratory symptoms

· general health

· family history

· of spinal deformity

· of familial conditions

· status of growth

· growth

· menarche

· changes of puberty

Examination

· assessment of back

· area of curve

· deviation of plumb line from C7 (cm)

· shoulder elevation (cm), scapular prominence

· flank prominence, asymmetrical loin creases

· Adam's forward bending test

· presence and height of rib hump (spirit level, cm)

· hump corresponds to convexity of curve

· deviation to one side during bending

· angulation when viewed from side

· neurological examination

· assessment of physical maturity

· signs of other conditions

Radiology

Plain x-ray

Films

· standing PA or AP film of whole spine on one film

· PA gives less radiation to breasts and ovaries

· AP has less magnification

Measurement of curve

· curve measured using Cobb technique

· end vertebrae of curve selected

· those that are most tilted from horizontal or whose end plates are last to converge

· line drawn along upper end plate of upper end vertebra and lower end plate of lower end vertebra

· perpendiculars drawn from these lines

· angle of intersection measured

· for double curve, one vertebra is upper end vertebra for lower end curve and lower end vertebra for upper curve (transitional curve)

· only one line drawn on this vertebra

· in future, measurement should always be from same vertebrae

Shortcomings

· true size and anatomy concealed

· true size of curve demonstrated on film taken perpendicular to plane of apical vertebra (plan d’election’)

· hypokyposis demonstrated on film taken at 90^o to this

· error in measurement

· is +/- 3^o (ie. up to 6^o variation)

Additional x-rays

Lateral bend films

· supine with maximum voluntary lateral bend

· determines flexibility

· differentiates structural from compensatory curves

· indicated in preoperative evaluation for

· double curve

· low curve to see if L4 corrects

Lateral films

· standing

· to measure kyphosis and lordosis

· use Cobb's method

Bone scan

· if bone tumour or infection suspected

MRI

· if intraspinal pathology suspected

· indications

· left-sided

· male

· painful

· rapidly progressive

· neurological abnormality

· findings

· 20^o of right curves have pathology

· 80^o of left curves have pathology

Assessment of rotation

· no definite association between

· lateral curvature

· rotation

· rib hump

Rib hump

· use scoliometer

· <5^o tilt = < 30^o rotation

· >7^otilt = > 30^o rotation

Perdrolli protractor

· inaccurate

Stereophotogrammetry

· projection of grid on spine

· stereocamera

Moe and Nash ratio

· amount pedicle displaced across body

· expressed as percentage of width of body

Tangential x-ray

· difficult to interpret

CT scan

· most accurate

classification

King

Type I - lumbar dominant (10%)

· S-shaped curve

· both thoracic and lumbar curves cross midline

· lumbar curve larger or more rigid

Type II - thoracic dominant (33%)

· S-shaped curve

· both thoracic and lumbar curves cross midline

· thoracic curve larger or more rigid

Type III - thoracic (33%)

· thoracic curve

· lumbar curve does not cross midline

Type IV - long thoracic (10%)

· long thoracic curve

· L5 over sacrum

· L4 tilted into curve

Type V - double thoracic (10%)

· double thoracic curve

· T1 tilted into upper curve

· upper curve structural

prevention

· school screening

· performed by school nurses

· usually at

· age 10 (girls)

· age 12 (boys and girls)

Technique

Visual observation

· parental permission

· examine genders separately

· strip to underwear

· observe from front, side and behind

· look for

· shoulder height

· scapular prominence

· thoracic contour

· loin creases

· distance from medial epicondyle to waist

· iliac crest prominence

· view in Adam’s forward bend position

· prominence of thoracic cage

· lumbar flank prominence

Other

· mechanical device

· inclinometer

· photographic device

· moire fringe topography

Findings

· referral rate is high on visual inspection (10%)

· high incidence of schooliosis

· abnormalities of body topography

· pelvic tilt from mild leg length discrepancy (40%)

· can be lowered by use of inclinometer

· 3% referred if cutoff of 7^o used

Effect

· increase in early referrals

· increase in

· decrease in incidence of surgery

· decrease in magnitude of curve at surgery

· increase in referrals to spinal service

Result

· screening discontinued in UK, USA and Canada

treatment

Decision making

· three forms of treatment

· observation

· nonsurgical treatment

· surgical treatment

· depends on

· magnitude of curve

· growth potential

· for convenience, growth divided as follows

· rapid growth precedes menarche (girls) and axillary hair (boys) and Risser II

· decreased growth occurs after this

curve treatment

rapid growth decreased growth

<20^o observation observation or discharge

20-29^o observation observation

brace if progressive

30-44^o brace observation

>45^o surgical surgical or observation

Observation

· review every 3-6 months while significant growth potential

· frequency depends on magnitude of curve

Nonsurgical treatment

Indications

· still growing

· Risser 0, I or II

· around onset of menarche (girls) or axillary hair (boys)

· add bone age if unclear

· curve 25^o to 45^o

· 25-29^o and documented progression

· 30^o (progression not required)

· patient

· co-operative

· compliant

Milwaukee brace

· developed in 1945 by Blount and Schmidt

· standard orthosis for adolescent thoracic idiopathic scoliosis

Description

· pelvic girdle that reduces lumbar lordosis

· two posterior uprights

· one anterior upright

· neck ring with throat mould anteriorly and two occipital pads posteriorly

· was distraction device in past

· caused significant problems with dentition

· L-shaped thoracic pad that pushes at apex on convexity

· lumbar pad that similarly pushes at convexity

· provides passive correction by pressure on convex side and active correction by muscle contraction pulling body away from pads

Indications

· effective for growing children with curves 20^o-45^o

· curves <20^o usually do not progress and do not need orthosis

· curves >45^o respond poorly to orthosis

· only used for curves 20^o-29^o if progressive

· used immediately for curves 30^o-45^o

· preferable if Risser 0, I or II

· not used if reached Risser IV

· may be used on trial basis if curve >45^o

· if 30% improvement in 6 months not achieved, surgery indicated

Management

· initial x-ray should show 30-50% improvement in curve

· patient not weaned into brace

· seen after 2-3 weeks for adjustment

· then seen every 3-6 months

· brace adjusted

· x-ray taken to assess response

· in brace to assess progression

· brace worn 23 hours a day

· allowed out to play sport

· if curve progresses beyond 45^o, surgery indicated

· weaning commenced once skeletal maturity reached

· full height achieved with no further progress of curve

· Risser IV achieved

· weaned as follows

· 20 hrs for 4 mths

· 16 hrs for 4 mths

· 12 hrs for 4 mths

· night-time only for 4 mths

Compliance

· underestimated

· true compliance may only be 20%

· may use device to measure actual hours brace worn

· part-time bracing (16 hours) may be more effective than thought

Results

· brace is holding device that may prevent deterioration

· cannot provide permanent curve improvement

· most common result

· produces 50% correction in curvature in first 6 months

· when bracing discontinued, curve is 15% better than when started

· 5 yrs after brace discontinued, increase in curve to pre-brace value

· brace may improve rib hump more than Cobb angle or rotational deformity

· about 85% of patients have satisfactory result (no need for surgery)

Underarm orthoses

· thoracolumbar spinal orthosis (TLSO)

· made from thermoplastic material, from cast of patient in corrected position

· worn and weaned as for Milwaukee brace

Indications

· flexible curves <40^o

· apex below T8

Advantages

· more cosmetically acceptable

· compliance higher

Disadvantages

· provides passive correction only

· three-point holding system

· may be less effective than Milwaukee brace

Results

· prospective study by SRS

· 10-15 yr followup

· brace vs electrical stimulation vs observation

· brace effective in preventing progression in 75%

· stimulation and observation effective in 33%

Electrical stimulators

· skin electrodes applied to spine

· applied laterally at upper and lower end of convex side of curve

· electrical stimulation produces contraction of muscles on convexity of curve

· worn for 8 hours a day (at night)

· proved to be ineffective and has been abandoned

Physical therapy

· shown to be of no benefit

Surgical treatment

Indications

· general indications are

· documented progression to 40-45^o

· marked imbalance

· special considerations with

1. double curve

· often balances itself out

· does not progress unless > 60^o

2. low lumbar curve

· surgery produces problems

· early - pseudarthrosis and loss of lordosis

· late - caudad degeneration

· most common indication is

· adolescent or young adult

· idiopathic thoracic curve

· progression to 40-50^o

Rationale

· correction of cosmetic defect

· prevention of respiratory insufficiency

Goals

· reduction of rib hump

· correction of rotation

· achievement of rigid fixaton to obtain solid fusion

Selection of fusion area

Principles

· must fuse structural curve and not compensatory curve

· must not fuse less than the measured curve and usually more

· avoid fusion to L5 (L4 or sacrum)

· avoid fusion above T1

· centre lower end of fusion on vertical line from centre of S1

· fuse down to

· neutral vertebra (pedicles symmetrical on PA film)

· stable vertebra (one bisected by vertical line through sacrum in level pelvis)

General

· fuse level above and level below measured curve

· fuse down to neutrally rotated vertebra above to neutrally rotated vertebra below (pedicles symmetrical on PA film)

Specific

· from Twin Cities (King, Moe, Bradford, Winter)

· King 1

· fuse both curves to lower vertebra

· no lower than L4

· King II

· selectively fuse thoracic curve only

· lower level at stable (rather than neutral) vertebra

· King III

· fuse measured thoracic curve

· lower level at first stable vertebra

· King IV

· as for King III

· usually stop at L4

· King V

· fuse both thoracic curves

· lower level at stable vertebra

Posterior

Surgical principles

· complete facet joint excision on both sides (convex and concave)

· replacement of facet joint area by autogenous bone

· complete decortication of all exposed laminae and transverse processes

· addition of extra autogenous graft from iliac crest

Instrumentation

· instrumentation is adjunct to fusion rather than replacement for fusion

· provides

· internal correction of rib hump and rotation

· internal stabilisation

Harrington instrumentation

· was standard for scoliosis surgery

· consist of distraction rods, flexible compression rods and various hooks through which rods pass

· hook placed top and bottom and distraction rod placed between hooks

· spine then distracted

· high rate of implant-related complications

· no longer used

Luque instrumentation

· L-shaped rods and sublaminar wires

· rod on either side fixed at each level with wire under lamina

· first segmental fixation system

· can preserve and improve sagittal curves

· significant drawbacks with wires, esp. neurological complications

Winsconsin instrumentation

· attempt to use segmental fixation without problems of sublaminar wires

· uses Harrington rod, Luque rod and wires passed through spinous processes

· no longer used

Cotrel-Dubousset instrumentation

· most recent development

· scoliosis corrected by combination of initial distraction and subsequent rotation

· two rods used, one on concavity and one on convexity

· segmental fixation with laminar and pedicle hooks that fasten to rod

· rods cross-linked with transverse linkage bars to form rectangle

· advantages

· rigid fixation so no postoperative support necessary

· greater correction achieved (50%-75%)

· rotational deformity corrected so rib hump addressed

· allows preservation and recreation of sagittal contour

· versatile because pedicle fixation possible

· disadvantages

· technically more difficult

· increased risk of neurological complications

· implants large and may be palpable

· very expensive

Anterior

Indications

· to achieve mobility

· rigid curve

· to achieve growth arrest

· skeletally immature patient

· to supplement anterior fusion

· neuromuscular curve

Advantages

· less levels instrumented

· less so with new posterior segmental instrumentation

· better rotational correction

Disadvantages

· requires anterior approach

· does not produce lumbar lordosis

· can be overcome with allograft shape

Instrumentation

· Dwyer system was first system used

· largely replaced by Zielke system

· indications

· instrumentation of flexible lumbar or thoracolumbar curve

· initial stage of two-stage anterior and posterior spinal instrumentation and fusion for rigid thoracolumbar or lumbar curve

· advantages

· fewer levels included in arthrodesis

· easier achievement of derotation

· disadvantages

· higher pseudarthrosis rate

· kyphosis across fused segment

· need for postoperative immobilisation

Costoplasty

· partial excision of 5 or 6 ribs

· corrects rib hump

· good source of autograft

· does not increase morbidity

Early complications

Neurological injury during surgery

· incidence is 1% in adolescents and 2% in adults

· may be minimised with spinal cord monitoring

· wake-up test often used

Blood loss

· risk of transmission of disease with transfusion

· techniques of conservation used

· autologous donation

· hypotensive anaesthesia

· autotransfusion

Wound infection

· prophylactic antibiotics indicated

Pneumothorax

· occurs during subperiosteal spine exposure, esp. area between adjacent thoracic transverse processes on concave side

Dural tear

· during ligamentum flavum removal or hook or wire insertion

Abnormal sagittal alignment

· inadvertent 'flat-back'

Incorrect fusion levels

· from incorrect preoperative choice or from incorrect intraoperative placement

Inappropriate ADH secretion

· postoperative SIADH

· decreased urinary output, decreased serum osmolality and increased urine osmolality

· if not diagnosed, iatrogenic fluid overload and even death may occur

Late complications

Pseudarthrosis

· occurs in about 1%

· 5% with fusion to sacrum

· solid fusion should occur by 6 months

Rod or wire breakage

· due to pseudarthrosis or fatigue failure

· if pain persists or correction lost, fixation must be removed

Back pain

· appears to be due to

· fusion below L4

· loss of lumbar lordosis

· fusion level and back pain

· L5 - 80%

· L4 - 60%

· L3 - 40%

· L2 - 20%

Infantile idiopathic scoliosis

features

· more common in males

· usually produces a thoracolumbar curve to the left

· curve usually longer

· curve regresses spontaneously in 90% of cases

· the remainder are progressive and lead to severe deformities

· more likely to cause cardiorespiratory compromise

progression

Mehta angle

· rib-vertebral angle distance (RVAD)

· difference in angle at which rib meets spine at apex of curve on either side on AP x-ray

· if angle >20^o, curve likely to progress

Degree of curve

· likely to progress if curve >35^o

treatment

Indications

· progressive curves

· curves > 35^o

· RVAD >20^o

Nonoperative

· treatment of choice is Milwaukee brace

· some patients can be cured

· brace must be worn until curve maximally and permanently corrected

Operative

· if curve continues to progress, surgery indicated

Instrumentation without fusion

· to avoid interference with growth

· in form of subcutaneous Harrington rod

· spine exposed at ends for hook insertion

· requires adjustment

· surgical extension every 6 mths

· requires second stage

· posterior fusion at age 10

· requires bracing until instrumented fusion performed

· high-risk procedure

· spontaneous fusion not uncommon

Hemiepiphyseodesis

· for large curve

· fusion of convex side

· to stop progression

· can be added to instrumentation without fusion

Posterior instrumented fusion

· not indicated in young children as causes crankshaft effect

· anterior growth continues

· curve enlarges as ‘squeezes out’

· can be safely performed at age 12 (girls) or 14 (boys)

Anterior and posterior instrumented fusion

· avoids crankshaft effect

· inhibits growth

Juvenile idiopathic scoliosis

· does not usually resolve spontaneously

· usually progress and produce severe deformities

· treatment indicated if curve >20^o

· if curve <60^o, best treatment is Milwaukee brace

· permanent correction may be achieved during growth

· minimum of 2 years bracing required

· brace must be worn even part-time while growth continues

· if curve progresses despite bracing, instrumentation protected with brace used

· arthrodesis performed at age 12-14, or earlier if curve continues to deteriorate