Impact of sagittal plane Impact of sagittal plane spinal deformity on the spinal deformity on the

spino-pelvic relationship and spino-pelvic relationship and gravity line position in adultsgravity line position in adults

Virginie Lafage, Frank Schwab, Francisco Rubio, Jean-Pierre Virginie Lafage, Frank Schwab, Francisco Rubio, Jean-Pierre FarcyFarcy

Maimonides Medical Center - NYU HJD, New York

SRS - 2006

Context

Adult Sagittal Adult Sagittal Imbalance Remains Imbalance Remains poorly understood poorly understood

and challengingand challenging

Loss of global alignment Loss of global alignment (Plumbline shift anteriorly)(Plumbline shift anteriorly)

=> Increasing disability=> Increasing disabilitySF-12, SRS-29, ODI SF-12, SRS-29, ODI (p<0.001)(p<0.001)

=> Lumbar kyphosis marked disability=> Lumbar kyphosis marked disabilitySRS-29, ODI (p<0.05)SRS-29, ODI (p<0.05)

Degenerative, Pathology, Degenerative, Pathology, IatrogenicIatrogenic

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X-raysX-rays Global alignment Global alignment Spinal parameters (SVA, Spinal parameters (SVA,

kyphosis, lordosis, …)kyphosis, lordosis, …) Pelvic Parameters (incidence, tilt, Pelvic Parameters (incidence, tilt,

sacral slope)sacral slope)

Forceplate technologyForceplate technology Location of anatomical Location of anatomical

components components Gravity Line (GL) Gravity Line (GL) and Feetand Feet

Compensatory mechanismsCompensatory mechanisms– Pelvis (rotation / translation)Pelvis (rotation / translation)– Lower extremitiesLower extremities– feetfeet

Force Plate and X-ray Analysis

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Investigate differences between Investigate differences between asymptomatic adultsasymptomatic adults and patients and patients

with with sagittal plane spinal deformitysagittal plane spinal deformity

Are there changes* in the Are there changes* in the relationship between GL and spino-relationship between GL and spino-

pelvic parameters?pelvic parameters?

PurposePurpose

*Group differences were evaluated by independent sample t-tests.

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Clinical Group

Group N Group N

No sagittal plane deformityNo sagittal plane deformity

44 volunteer subjects44 volunteer subjects

Mean age = 57y.o.Mean age = 57y.o.

Prospective IRB

Group SGroup S

Sagittal pane spinal deformitySagittal pane spinal deformity

SVA > 5 cm SVA > 5 cm OROR pelvic tilt > 20 pelvic tilt > 20°°

40 subjects40 subjects

Mean age = 65y.o.Mean age = 65y.o.

Inclusion criteriaInclusion criteriaAge > 18 y.o.Age > 18 y.o.

No Previous spine surgeryNo Previous spine surgery

Cobb angle < 20Cobb angle < 20C7 Frontal Imbalance < 5cmC7 Frontal Imbalance < 5cm

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Frontal & Sagittal XRaysFree standing positionFree standing position

pressure distribution feetForce PlateForce Plate

MethodSimultaneous assessment of X-Rays and load distribution

Gravity Line (GL) and heel line projected on X-rays

Offsets between:Offsets between: GL, Heel line and GL, Heel line and

anatomical landmarksanatomical landmarks

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X-rays parameters Differences over the 2 groups

Group IncidenceSacral slope

Pelvic Tilt

Lordosis

Kyphosis

Global inclinatio

nSVA

N 51 38 13 58 -43 -12 0

S 60 34 27 46 -51 -3 8

Significant differencesSignificant differences

Pelvic Incidence increasesPelvis Tilt increases*Lordosis Decreases

Forward Trunk FlexionSVA increases*

* Inclusion criteria

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Sagittal planeForceplate & x-ray

Group NGroup N Group SGroup S

Gravity LineGravity LineHeels LineHeels Line

GL vs. Heels = constant

Pelvis shifts posteriorly

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Sagittal planeForceplate & x-ray

Group N

Group S

Pelvic Pelvic Parameters:Parameters:

Pelvic Incidence increasesPelvic Tilt increases*

Spinal Spinal Parameters:Parameters:

Trunk tilts forward

GLGLParameters:Parameters:

GL - Heels offset does not change

Pelvis shifts backward

Lordosis decreases SVA increases *

Incre

asin

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blin

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d p

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ic r

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ion

* Inclusion criteria

GLHeels Line

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Force Plate and Balance assessment

Gravity line varies little vs. heel positionGravity line varies little vs. heel position

Pelvis translates vs. GLPelvis translates vs. GL– Posteriorly with age and some pathologiesPosteriorly with age and some pathologies

– Global inclination more anterior with Global inclination more anterior with

age/pathologyage/pathology

Pelvis rotates around femoral headsPelvis rotates around femoral heads– Retroversion with age (?) and pathologyRetroversion with age (?) and pathology

ConclusionsKey points

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Sagittal Balance

Schematic Representation !!!!Schematic Representation !!!!

Young Adult

How to How to maintain maintain

balance if the balance if the trunk inclines trunk inclines

or shifts or shifts forward ?forward ?

Gravity Line vs. Heel = Gravity Line vs. Heel = ConstantConstant

Required to keep standing position

Age and pathologies do not affect this constraint

By definition, the whole body mass is equally distributed around the gravity line

What do we know ?What do we know ? Pelvis moves

backward Pelvic tilt increases Feet do not move

Only possible if lower Only possible if lower extremities are involvedextremities are involved

Hip flexion ? Knee flexion ?

Ankle regulation ?

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Wide variation of SVA / pelvic tilt can be toleratedWide variation of SVA / pelvic tilt can be tolerated– compensatory mechanisms to maintain standing compensatory mechanisms to maintain standing

balancebalance– Evaluation requires foot positionEvaluation requires foot position

Balance formula ?Balance formula ?– regional spinal and pelvic parametersregional spinal and pelvic parameters– global parametersglobal parameters– foot positionfoot position

all adding up to a rather fixed GL-heel offset (GHO)all adding up to a rather fixed GL-heel offset (GHO)

Conclusion