CanadianSocietyforBiomechanicsAnnualMeeting–July20,2016

ErikaNelson-Wong,MichalGlinka,MamikoNoguchi,HeleneLangevin,RhondaMaple,JimFox,andJackCallaghan

AMultifactorialProblem

MechanisticPathoanatomicSpinalLesions

Imaging≠diagnosis

Kent&Keating,2005

Behavioral/PsychosocialKinesiophobiaà Hypokinesia

Roleofmechanics?

Leeuwetal.,2007

AlteredMovementStrategiesMaladaptiveMovement

Causaloradaptive?

Hodges&Smeets,2016Nelson-Wongetal.,2010,2013

PathophysiologicalModelConnectiveTissue(perimuscularfascia)

InflammatoryProcessesInadditiontoabovefactors

Langevin&Sherman,2007

¡  FunctionoftheTLF§  Sustains/distributesloads§  Stabilizesspinalstructures§  Attachmentpointformuscles§  Sensesbodypositionandpain

¡  DecreasedTLFshearplane

mobilityinpeoplewithns-LBP▪  Langevinetal.,2011

¡  ReplicatedinporcinemodelwithsurgicalinjurytoTLF

▪  Bishopetal.,2016 Willardetal.,JAnat(2012)221,507-536

¡  Investigatetheinfluenceofasimulatedmuscle‘sprain’injuryonthestressrelaxationresponseoftheTLFusingaporcinemodel§  Expectedsamplesfrominjuredpigstohavedecreasedstressrelaxationresponse(lowerstressdecay)thanthosefromhealthypigs.

StrainEnergyandHysteresisGlinkaetal.,Poster#T49,Thursday

StiffnessNelson-Wongetal.,ASB,poster

•  10domesticswineàInjured(n=5)andControl(n=5)•  Unilateral surgical injury (4 cm2 at the L3/4 level) à usual

activity•  Euthanizedat8weeks, tissueblocksexcisedcontralateral to

injury•  Frozenat-80°C,shippedtoWaterlooformechanicaltesting

Nelson-Wongetal.,submittedJBiomech,2016

Bishopetal.,2016

¡  Displacementcontrolled§  %initialrakewidth

¡  Measureforce§  transverse,longitudinal

¡  Rakedisplacement§  ‘stretchratio’=amountof

displacementrelativetoinitial

Uniaxiallongitudinalconfigura0on

Biaxialconfigura0on

¡  ThreeLoadingConditions§  UniaxialLongitudinal§  UniaxialTransverse§  Biaxial–analyzedindependentlyasBiaxial

Longitudinal,BiaxialTransverse

0

200

400

600

800

1000

1200

1400

0

200

400

600

800

1000

1200

1400

1600

1800

0 200 400 600 800 1000 1200 1400

Force(m

N)

Displacemen

t(um

)

Time(sec)DisplacementForce

240s

25%

35%

45%

240s

240s

5cycles

Pre-tensionto10mNPrecondition:5cyclesat10%

Nelson-Wongetal.,submittedJBiomech,2016

¡  Stresscalculatedfrommeasuredforceandinitialsampledimensions:

¡  Normalizedtopeak,time-varyingplotscreatedforeachcondition

¡  StressRelaxationResponseexpressedasstressdecay:

Stress = TensileForceInitialCrossS ec tionalArea

SRR =100%−EquilibriumStress

PeakStress

Injured

HealthyControl

Group

Uniaxial

Biaxial

Loading

Transverse

Longitudinal

Orientation

25%

35%

45%

StretchCondition

Interestedinmaineffectofinjurygroupand/orsignificantinteractionswithinjurygroup

40

45

50

55

25% 35% 45%

StressRelaxa+

onRespo

nse(%

Decrease)

StretchCondi+on

Control Injured

*p=.02NS

NS

¡  Simulatedmuscle‘sprain’withsurgicalinjury§  Inflammationwithoutstructuraldamage§  Lowbackmechanicsunchanged(theoretically)§  Testedtissuecontralateraltoinjurysite

¡  Stressrelaxation§  Time-dependent,viscoelasticresponseinbiologicaltissues

§  Allowsdeformedtissuestoreturntorelaxedstressstate§  Potentiallyminimizestotalstressinthetissue

¡  Decreasedrelaxationwithinjuryat45%stretch§  45%stretchratiomaybenearend-rangelimitsofphysiologicalflexion

§  Coulddisruptloadsharingbetweenpassiveconnectivetissues,impactmuscleactivation(flexionrelaxation?)

§  PotentialmechanismforLBPrecurrence/chronicityfollowingmuscleinjury(inflammation)?

MechanisticPathoanatomic

Mechanicaleffectson

fascia

Behavioral/PsychosocialHypokinesia

Decreasedmobilityimpactsfascia

Bishopetal.,2016

AlteredMovementStrategies

Connectivetissueimpactsmuscle

function

PathophysiologicalModelConnectiveTissue(perimuscularfascia)

InflammatoryProcessesRelatedtoabovefactors

Langevin&Sherman,2007

Biochemicalstudiesrequiredtoisolatepotentialmechanisms

Thankyou!

Dr.LangevinissupportedthroughNCCHIResearchGrantR01AT004400