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Fig.2.2Measurementof the slip angle.Theangle is made bythesuperior end plate ofthecaudal vertebrae and the
inferior end plate of the cranial vertebrae. The slip angle of a L5-S1 spondylolisthesis is measured by a line
perpendiculartotheposterioraspectofsacrumandalinedrawnalongtheinferiorendoftheendplateofL5.
Fig.2.3Measurementofthediskheight.Alineisdroppedfromthemidlineinferiorendplateofthecranialvertebraeto
the upper end plateof thecaudal vertebrae.The ratiobetween this distance and the midline vertebral height of the
cranialvertebraeiscomparedondynamicviews.
Full-length standing coronal and sagittal radiographs are used for assessment of the
overallcoronalandsagittalbalanceusingthecentersacralverticalline(Fig.2.4)andC7
plumbline (Fig. 2.5). The bisector of the center sacral vertical line is also useful for
finding the proximal neutral vertebra. Sagittal balance is measured by the C7 sagittal
plumbline,andlumbarlordosisisusuallymeasuredfromtheupperendplateofT12tothe
endplateof S1.Shoulder height,apical vertebral translationof thethoracic andlumbar
curves, curve magnitudes, and flexibility should be documented. Common local
deformities seen on radiographs include an L2-L3 apex deformity, lateral listhesis or
rotatory subluxation (Fig. 2.6), lumbar hypolordosis, and short reciprocating curves.
Laterallisthesisorrotatorysubluxationismeasuredbythehorizontaldistancebetweenthe
supero-lateral corner of the caudal vertebra and the inferolateral corner of cephalad
vertebra. Bending radiographs can differentiate stiff curves from flexible curves, but is
moreimportantfordecidingontheinstrumentationlevelsduringsurgery.MRIisusefulto
assess disk degeneration and spinal stenosis. Deformity correction is required for these
symptoms and may require more complex operations such as osteotomies and long
fusions.
Fig. 2.4 Measurement of central sacral vertical line. Using the top of the iliaccrest tocontrol fortilting, a vertical
perpendicularlineisdrawnupfromthecenterofS1.Theproximalneutralvertebracanbebisectedfromthisline,andin
thisfigureitwouldbeL2.
Fig.2.5MeasurementofsagittalC7plumblineisdonebydroppingaverticalperpendicularlinetothehorizontalfrom
theC7vertebralbody and comparing its horizontal position withthe positionof theposterosuperior cornerof theS1
superiorendplate.Sagittalimbalanceisnormallyconsideredtobe>5cmdeviationfromtheS1posterosuperiorcorner,
andinthisfigurethereisapositivesagittalbalance.
Fig. 2.6 Lateral subluxation is measured by the horizontal distance between the superolateral corner of the caudal
vertebraandtheinferolateralcornerofthecephaladvertebra.
DiagnosisofLegPain
The classic presentation of nerve root compression is buttock pain that radiates to the
lower extremitiesand neurogenic claudication.Radicular or legpainpoints to spinalor
foraminal stenosiscaused by facetjoint and ligamentum flavumhypertrophy,foraminal
narrowingduetovertebralrotatorysubluxation,orreductionoftheinterpediculardistance
on the concavity of the curve. These patients usually develop burning or aching pain
starting in the buttock that radiates down the appropriately involved dermatome to the
lowerleg. Clinicalidentificationof theinvolveddermatome providesagood cluetothe
likelynerverootaffected.Thiscanthenbeconfirmedifthereiscorrespondingweakness
inthesamemyotome.Typically,impingementoftheL4nerverootleadstoanteriorshin
numbnesswithankle dorsiflexionweakness(tibialisanterior),an L5nerverootinvolves
theposterolateralcalfandfootdorsum,withextensorhallucislongusweakness,andanS1
nerve root involves the posterior calf and sole, with weakness of the flexor hallucis
longus.
Neurogenicclaudicationcommonlypresentswithinsidiousonsetofbuttock,thigh,and
calfpaintriggeredbywalking.Theusualdisabilityisthusdiminishedwalkingtolerance.
Vascular claudication is an important differential diagnosis. Patients with vascular
claudicationmayalsopresentwithdiminishedwalkingtoleranceduetocalfcrampingon
exertionorasensationoftightnessthatproceedsfromdistaltoproximal.Thiscontraststo
neurogenic claudication where discomfort with numbness proceeds from proximal to
distal.Objectivesensoryexamination shouldpinpointthespecificdermatome orsuggest
whichnerve rootiscompressed. Motorweaknessusually suggestsamore long-standing
nervecompression.Vascularexaminationshouldbeperformed,includingobservationfor
trophic changes in the skin and nails of the lower limbs and diminished distal pulses,
whichwouldsuggestavasculogeniccauseforthepain.
Radiographicassessmentwasdescribedabove(seeDiagnosisofBackPain).
FactorsthatMayLeadtoCurveProgression,Hencethe
NeedforSurgicalTreatment
Ingeneral,theissueofwhethercurvesprogressisdebatedintheliterature,andtherateof
progression ishighly variable. Curvesmay progress 1 to6 degrees peryear (average 3
degreesperyear).
6,7
Riskfactorsforprogressionincludeapriorhistoryofprogressionand
radiographic risk factors such as asymmetrical disk degeneration, lateral disk wedging,
andosteophyteformation.
8–10
Comparingthetwosidesofaspinalsegment,lessthan80%
oflateraldiskwedgeandmorethan5mmoflateralosteophytedifferencemayindicatean
unstablesegment.
9
ProgressionhasbeensuggestedtooccurwithCobbanglesgreaterthan
30degrees,lossoflumbarlordosis,apicalrotationlargerthanNash-Moegrade2(convex
pedicle migrates 25% of the vertebral body width and the concave pedicle gradually
disappears),laterallisthesisof6mmormore,oraprominentordeeplyseatedL5disk(in
relationship to the intercrestal line).
11–14
The presence of rotatory subluxation, lateral
spondylolisthesis,anddiskdegenerationintheupperlumbarlevelsalsosuggestsariskof
progressivedeformity.
12
Duetospinecoupling,rotatory deformityof thespineisrelated
tothedevelopment oflateral spondylolisthesis. Thus,apical vertebralrotation may also
predictscoliosisprogression. Spinalsegmentsproximaltothe scoliosissharetheload to
compensate forspine imbalance. With diskdegeneration, this compensatorymechanism
fails, and progressive deformity occurs. Fusion surgery is required to prevent curve
progression,and thelengthof fusionisdependent onthepresence ofcoronalor sagittal
imbalance.
Management
Management of adult deformities should be tailored to each patient because the
symptomatologyis differentin everycase. Treatmentis dependenton theexperience of
thesurgeon,thepatient’spreference,thepatient’sageandfunctionalstatus,magnitudeof
deformity,therateofprogression,andthepresenceofcomorbidities.Sometimesthecause
ofpainisdifficulttodifferentiatebasedsolelyonclinicalandradiologicalexamination.In
thesecases,transforaminalepiduralinjections,selectivenerverootblocks,andfacetjoint
blocksarecommonlyutilizedtoidentifythepaingenerator.
Nonoperativemanagementisusuallyreservedforpatientswithmildsymptomsarising
from stenosis, radicular or back pain, curve magnitude of less than 30 degrees, lateral
subluxation ofless than 2mm, and reasonablecoronal and sagittalbalance.
14
Common
indications for surgery include axial back pain, symptomatic deformity, neurologic
symptoms,anddissatisfactionwithappearance.Thefinaldecisionshouldbeabalanceof
themagnitudeof surgery, thequalityoflife gain,andtheriskofsurgicalcomplications.
Patientswithsevere deformitymayrequiremajorsurgerytoachievefullcorrection,and
theriskofcomplicationswilldramaticallyincrease.Complicationratesofupto80%have
beenreportedinsomeseries.
15,16
Conversely,decompressiononlyorlimited fusionmay
besufficienttoprovidereasonableandlasting reliefforpatients.Thefollowingsections
discuss the authors’ experience in surgical decision making, choosing between
decompressiononlyandshortorlongfusion,andthepitfallsofmanagingadultdeformity.
CriticalFactorsinDecisionMakingforSurgery
Thegoalofsurgeryforthesepatientsshouldbetoperformthesmallestoperationpossible
thatwouldhelprelievethesymptomsandpreventarecurrence.Wefindithelpstobreak
downthecomponentsofpatientcomplaintsinordertomakeanappropriatedecision.
1.Legpain
a.Nerverootcompression/spinalstenosis—localdecompression
b.Degenerativespondylolisthesis—localdecompression±fusion
2.Backpain
a.Forlocaldegenerationorinstability—shortfusion
b.Forflexibleorcorrectablesagittalorcoronalimbalance—longfusion
c.Forstifforuncorrectablesagittalorcoronalimbalance—longfusion+osteotomies
3.Progressivedeformity
a. Long fusion to prevent progression, seldom would be performed alone in the
absenceofsymptomsabove
SurgicalDecisionMaking
DecompressionOnly
Decompressionaloneisindicatedfor patientswithneurogenicclaudicationwithoutback
painorasymptomaticorprogressivedeformity.Decompressionisusuallyintheformof
posterior fenestration or laminectomy, although other approaches, including anterior
indirectdecompression and endoscopictransforaminal approaches,have beendescribed.
Eachapproachhasmeritandwouldbedependentonthesurgeon’sexperience.Adetailed
discussion of their relative merits is beyond the scope of this chapter. As a general
principle, inthose patients undergoingdecompression alone, asmuch facet jointand as
manyposteriorligamentousstructures aspossibleshouldbepreservedtoreducetherisk
offutureprogressionandiatrogenicinstability.
One should always be prepared to carry out a local fusion if more extensive bone
resectionis necessary.Thisis notuncommonas suchindividualsoften havetightspinal
canals,andincidentaldurotomiesarenotinfrequent.Ifawidelaminectomyisperformed
fortherepair,alocalfusionwithpediclescrewfixationmaybeadvisable.
Usualindicationsfordecompression-onlysurgeryincludelegpainwithminimalorno
backpain,Cobbanglesoflessthan30degrees,lessthan2mmoflateralsubluxation,and
normal coronal and sagittal balance indicated by the center sacral vertical line and C7
plumbline.
14
Despite combined back and leg symptoms that may warrant fusion,
decompression alonemay be indicatedfor patients withsignificantly high surgicalrisk.
This maybe the bestoption for an elderlypatient with neurogenicclaudication, a mild
deformity,andpoorbonequality.Patientsundergoingdecompressionaloneshouldalways
be warned of a risk of progression of the deformity that may require a future fusion
procedure.
Fusion
Fusionsurgeryisindicatedforthetreatmentofbackpainduetodegenerativechangesor
instability,aswellastopreventprogressionofthe deformity.Itmaybe performedalone
orincombination withdecompressioninpatientswith radicularsymptoms.Shortfusion
may beuseful to stabilize curves withsignificant apical rotation orwhen translation or
laterallisthesisisgreaterthan3mm.
6,12,17,18
However,ifthereissymptomaticcoronalor
sagittalimbalance,realignmentandlongfusionisadvisable.
Determination of fusion levels for adult scoliosis is based on the severity of spinal
deformityand the globalappearance anddegenerative changesof the entirespinopelvic
axis.Thereisnouniversalagreementonthelengthoffusionandtheselectionmethodof
theendvertebraeforinstrumentation.
Shortfusionwithinthedeformitynotexceedingtheendvertebraeaimstostabilizethe
spinalsegmentswithoutcorrectingthewholedeformity.Itsmajoradvantageisthelower
riskofcomplicationsfromtheanesthesiaorthesurgery;thusitisindicatedinthosewith
back pain butwithoutcoronal or sagittal imbalance. Long fusions orfusions extending
beyond the end vertebrae is useful for correction of large curvatures with coronal or
sagittalimbalance,butthisprocedureneedstobebalancedagainstincreasedcomplication
rates.
Typical patients who may be managed with short fusions (Fig. 2.7) are those with
smaller Cobb angles (less than 30 degrees) and minor rotatory subluxation (lateral
subluxationsofmorethan2mm).
14
Backandlegpainandsegmentalinstabilitycausedby
widedecompressionscanallbetreatedwithshortfusions.
Longfusions(Fig.2.8),whichgenerallymeansfusiontoL5orthesacrum,andtoT10
or above, yield better surgical correction of the scoliosis and restoration of lumbar
lordosis.Theyaretypicallyindicatedforpatientswhosecurvesarelikelytoprogress,such
as patients with Cobb angles greater than 45 degrees, more than 2 mm of lateral
subluxation,andcoronalandsagittalimbalance.
14
Theaimofthelongfusionistoachieve
balance in both the coronal and sagittal planes, not absolute Cobb angle correction.
19
Glassmanetal
20
demonstratedthatpositivesagittalbalanceisthesinglebiggestpredictor
of clinicalsymptoms in adultdeformity and takes priorityover other parameters.Thus,
long fusions should always be considered in patients with global coronal or sagittal
imbalancetoachievebetterfunctionaloutcomes.
Itshouldbeborneinmindthatinstrumentationshouldnotendatthelevelofjunctional
kyphosisorspondylolisthesis.Anylevelofsevererotatorysubluxationshouldbeincluded
withinthefusionblock.Tobalance thespine,themosthorizontalvertebrashouldbe the
upper instrumented vertebra (UIV).
21
Instrumentation should not end at a level with
posteriorcolumndeficiency,withlisthesisinanydirection,atalevelofarotatedsegment,
withjunctionalkyphosis,attheapexofthedeformityinthecoronalorsagittalplane,orat
adegeneratedlevel.
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