Spine Biomechanics,Spine Biomechanics,Intervertebral Disc &LBPIntervertebral Disc &LBP

SpineSpine

Cervical SpineCervical Spine

Seven vertebrae Seven vertebrae –– C 1C 1--77

More flexibleMore flexibleSupports the headSupports the headWide range of motionWide range of motion–– Rotation to left and rightRotation to left and right–– FlexionFlexion

Up and downUp and down

Peripheral nervesPeripheral nerves–– ArmsArms–– Shoulder, Chest and diaphragmShoulder, Chest and diaphragm

Thoracic SpineThoracic Spine

MidMid--back or dorsal regionback or dorsal regionTwelve vertebrae Twelve vertebrae –– T 1T 1--1212Ribs attached to vertebrae Ribs attached to vertebrae Relatively immobileRelatively immobilePeripheral nervesPeripheral nerves–– IntercostalIntercostal

Lumbar SpineLumbar Spine

Lower backLower backFive vertebrae Five vertebrae –– L 1L 1--55Carries the the weight of the upper body Carries the the weight of the upper body –– Larger, broader Larger, broader Peripheral nervesPeripheral nerves–– LegsLegs–– PelvisPelvis

Sacral and Coccygeal regionSacral and Coccygeal region

SSacrumacrum–– Triangular structure Triangular structure –– Base of the spineBase of the spine–– Connects spine to pelvisConnects spine to pelvis–– Nerves to pelvic organsNerves to pelvic organsCoccyxCoccyx–– Few small bonesFew small bones–– Remnant of tailRemnant of tail

LordosisLordosis

In the sagittal planeIn the sagittal plane–– ‘‘SS’’ shapeshape

As a small childAs a small child–– When starts to sitWhen starts to sit–– Cervical lordosisCervical lordosis

Toddler and adultToddler and adult–– When starts to standWhen starts to stand–– Lumbar lordosisLumbar lordosis–– Allows springAllows spring--like actionlike action

Compressive Strength of SpineCompressive Strength of Spine

StressStress--Strain CurveStrain Curve

Failure Strength of Spinal LigamentsFailure Strength of Spinal Ligaments

Motion SegmentMotion Segment

Two adjacent vertebraeTwo adjacent vertebraeIntervertebral discIntervertebral discSix degrees of freedomSix degrees of freedom–– FlexionFlexion--extensionextension–– Lateral flexionLateral flexion–– Axial rotationAxial rotation

Types of motionTypes of motion

Motion SegmentMotion Segment

Motion of Entire SpineMotion of Entire Spine

Motion of Entire SpineMotion of Entire Spine

Weight bearing properties of Weight bearing properties of motion segment unitmotion segment unit

Intervertebral DiscIntervertebral Disc

Soft fibroSoft fibro--cartilaginous cushionscartilaginous cushions–– Between two vertebraBetween two vertebra–– Allows some motionAllows some motion–– Serve as shock absorbersServe as shock absorbersTotal Total –– 23 discs23 discs¼¼ thth of the spinal column's lengthof the spinal column's lengthAvascular Avascular Nutrients diffuse through end platesNutrients diffuse through end plates

Intervertebral Disc FunctionsIntervertebral Disc Functions

Movement of fluid within the nucleusMovement of fluid within the nucleus–– Allows vertebrae to rock back and forthAllows vertebrae to rock back and forth–– FlexibilityFlexibilityAct to pad and maintain the space between Act to pad and maintain the space between the twentythe twenty--four movable vertebraefour movable vertebraeAct as shock absorbersAct as shock absorbersAllow extension and flexion Allow extension and flexion

Intervertebral Disc AnatomyIntervertebral Disc Anatomy

Spongy center Spongy center –– Nucleus pulposusNucleus pulposus

Surrounded by a Surrounded by a tougher outer tougher outer fibrous ring fibrous ring –– Anulus fibrosusAnulus fibrosus

Anulus FibrosusAnulus Fibrosus

Strong radial tireStrong radial tire––like structure like structure Series of lamellaeSeries of lamellaeConcentric sheets of collagen Concentric sheets of collagen fibers fibers –– Connected to end platesConnected to end plates–– Orientated at various anglesOrientated at various angles–– Under compressionUnder compression

Become horizontalBecome horizontal

Encloses nucleus Encloses nucleus pulposuspulposus

AnnulusAnnulus

In Bending In Bending –– Increased tensile force posteriorly Increased tensile force posteriorly –– Increased compressive force anteriorlyIncreased compressive force anteriorlyIn Rotation In Rotation –– Reorientation of collagenous fibersReorientation of collagenous fibers–– Tightening of fibers traveling in one directionTightening of fibers traveling in one direction–– Loosening of fibers traveling in opposite Loosening of fibers traveling in opposite

directiondirection

Nucleus PulposusNucleus Pulposus

Has more water and PGsHas more water and PGsPG are macroPG are macro--molecules molecules –– Attract and retain waterAttract and retain water–– Hydrophilic gelHydrophilic gel––like matter like matter

Resists compressionResists compression

Amount of waterAmount of water–– Activity related Activity related –– Varies throughout the day Varies throughout the day

Theory of weight bearingTheory of weight bearing

Nucleus pulpous Nucleus pulpous imbibes waterimbibes waterDevelops internal pressureDevelops internal pressurePressure exerted in all directionsPressure exerted in all directions–– Lateral forces Lateral forces

Against annulusAgainst annulus–– Superiorly and inferiorly directed forces Superiorly and inferiorly directed forces

Against end platesAgainst end plates–– Increases stiffness Increases stiffness

Of end plate and annulus fibrosusOf end plate and annulus fibrosus

Theory of weight bearing (contTheory of weight bearing (cont’’d)d)

Mechanical CharacteristicsMechanical Characteristics

Tensile stiffness of the disc annulus in different directionsHighest along – 150

Lowest along – the disc axis

StrengthStrength

Highest – Along normal direction of annulus fibers( 3 times stronger than that along horizontal direction)

Stiffness Coefficients of IV discStiffness Coefficients of IV disc

Creep CharacteristicsCreep Characteristics

Grade 0 - Non-degenerative disc ( more viscoelastic)Grade 2 – Mild degenerative disc (less sustenance)

Grade 3 – Severe degenerative disc ( more deformation)

Shear & Tensile CharacteristicsShear & Tensile Characteristics

In direct shear testsIn direct shear tests–– Shear stiffness in horizontal directionShear stiffness in horizontal direction

260 N/mm260 N/mm22

Spine rarely fails in pure shearSpine rarely fails in pure shearSimilarly under normal physiologic activitiesSimilarly under normal physiologic activities–– Pure tensile loading doesnPure tensile loading doesn’’t occurt occur–– But annulus undergoes tensile loading duringBut annulus undergoes tensile loading during

Bending Bending Axial rotationAxial rotationExtensionExtension

Compressive load characteristicsCompressive load characteristics

Cancellous boneCancellous bone–– Large deformationLarge deformation

Up to 9.5% before failureUp to 9.5% before failure

Cortical boneCortical bone–– Small deformationSmall deformation

Up to 2% before failureUp to 2% before failure

Measurements of In vivo LoadsMeasurements of In vivo Loads

Needle pressure Needle pressure transducer transducer CalibratedCalibrated–– Introduced into nucleus Introduced into nucleus

pulpous of cadaveric pulpous of cadaveric functional unitfunctional unit

Inserted in vivo in L3Inserted in vivo in L3--4 disc4 disc

Pathology of Intervertebral Disc InjuryPathology of Intervertebral Disc Injury

Annular InjuryAnnular Injury–– Annular rings Annular rings

SoftenedSoftenedOverstretched Overstretched Torn Torn

–– Normal viscoelasticity is exceededNormal viscoelasticity is exceeded–– Cannot stabilize or limit motionCannot stabilize or limit motion–– Nucleus pulposus exerts pressure on weak partNucleus pulposus exerts pressure on weak part–– Buckling occurs Buckling occurs -- Disc BulgeDisc Bulge

Pathology of Intervertebral Disc InjuryPathology of Intervertebral Disc Injury

ExtrusionExtrusion–– Fragmentation of Fragmentation of

nucleus pulposusnucleus pulposus–– Nuclear material Nuclear material

dissects its way dissects its way through breaches in through breaches in annulus fibrosusannulus fibrosus

Pathology of Intervertebral Disc InjuryPathology of Intervertebral Disc Injury

ProlapsesProlapses–– Fissures provide Fissures provide

pathway for irritating pathway for irritating nuclear fluid to nuclear fluid to escape onto escape onto perineural tissue *perineural tissue *

Persistent and chronic Persistent and chronic back painback pain

** -- Hampton et alHampton et al

Back PainBack Pain

Pain is a protective mechanismPain is a protective mechanismNerve endings near the spine receive abnormal Nerve endings near the spine receive abnormal stimulation stimulation Signals are transmitted from affected area to the Signals are transmitted from affected area to the brainbrain–– They are interpreted as painThey are interpreted as pain

A reflex action follows in the backA reflex action follows in the back–– Muscles go into spasm Muscles go into spasm

To protect the backTo protect the backTo keep the damaged area immobileTo keep the damaged area immobile

Types of painTypes of pain

Based on sourceBased on source–– MechanicalMechanical–– ChemicalChemical

Based on affected regionBased on affected region–– LocalLocal–– ReferredReferred

Based on natureBased on nature–– TransientTransient–– Acute Acute –– Chronic Chronic

CausesCauses of LBPof LBP

DysfunctionDysfunctionPredisposing factorsPredisposing factors–– Postural stressPostural stress–– Work related stressWork related stress–– Disuse and loss of mobilityDisuse and loss of mobility–– ObesityObesity–– Debilitating conditionsDebilitating conditions

Precipitating factorsPrecipitating factors–– MisuseMisuse–– OveruseOveruse–– Abuse or traumaAbuse or trauma

Examinations to locate back painExaminations to locate back pain

StandingStanding–– Observation and Palpation Observation and Palpation

Iliac crestIliac crestPosterior superior iliac spine (PSIS)Posterior superior iliac spine (PSIS)Anterior superior iliac spine (ASIS)Anterior superior iliac spine (ASIS)SpinousSpinous processesprocessesMuscle tightnessMuscle tightnessGaitGait

Examinations of back painExaminations of back pain

Movement TestingMovement Testing–– Forward bendingForward bending–– Backward bendingBackward bending–– Lateral bendingLateral bending–– RotationRotation–– Leg extension and backward bendingLeg extension and backward bending

Forward bendingForward bendingHands are pushing in Hands are pushing in opposite directionopposite directionTissues from skin to Tissues from skin to central corecentral core–– Elongate posterior Elongate posterior –– Compress anteriorCompress anterior

Assessing Assessing lumbolumbo--pelvic pelvic congruencycongruency–– Palpation from cervical spine Palpation from cervical spine

to pelvisto pelvis

Back ExaminationBack Examination

Nerve tension signsNerve tension signsNerve compression signsNerve compression signs

Examination of back painExamination of back pain

Supine TestingSupine Testing–– Passive hip flexionPassive hip flexion–– Faber positionFaber position–– Straight leg raise (SLR)Straight leg raise (SLR)–– Force is directed to right femurForce is directed to right femur

Posterior to anterior force directed to femur Posterior to anterior force directed to femur –– In flexed and vertical positionIn flexed and vertical position

–– Passive knee flexion in a prone positionPassive knee flexion in a prone position–– Passive internal and external hip rotation Passive internal and external hip rotation

knee at 90knee at 9000 of flexionof flexion

Passive hip flexionPassive hip flexion

Hip Hip hyperflexedhyperflexed–– Lumbar spine flattened Lumbar spine flattened

Over 90Over 9000 of flexionof flexion

Force transmissionForce transmission–– To extensor of hipTo extensor of hip

Posterior rotary Posterior rotary movement on iliummovement on ilium

–– Spinal flexionSpinal flexion

Straight leg raise (SLR)Straight leg raise (SLR)

Straight leg raisedStraight leg raisedFemoral flexionFemoral flexionAdductionAdductionInternal rotationInternal rotationIncrease in tensile Increase in tensile forceforce–– On sciatic nerveOn sciatic nerve

Related to ischial Related to ischial tuberositytuberosity

Phases of Treatment for Phases of Treatment for lumbopelvic disorderslumbopelvic disorders

Treatment of painTreatment of painModalities Modalities MedicationMedication

–– Support the regionSupport the region–– Biomechanical counseling / restBiomechanical counseling / restContinue supportContinue support–– Begin nonBegin non--destructive movementdestructive movement–– Decrease destructive behaviorDecrease destructive behavior

Phases of Treatment for Phases of Treatment for lumbopelvic disorders (contlumbopelvic disorders (cont’’d)d)

Discontinue supportDiscontinue support–– Begin proprioceptive and kinesthetic strength trainingBegin proprioceptive and kinesthetic strength training

Neuromuscular efficiencyNeuromuscular efficiencyDynamic stabilizationDynamic stabilization

Establishment of limitsEstablishment of limitsMovementMovementLoadsLoadsPositionsPositionsFrequencies Frequencies

Treatment OptionsTreatment Options

CryotherapyCryotherapyThermotherapyThermotherapy–– Superficial heatingSuperficial heating–– Deep HeatDeep HeatInjection Therapy & Soft tissue injectionsInjection Therapy & Soft tissue injectionsElectrotherapyElectrotherapy–– Transcutaneous electrical nerve stimulation Transcutaneous electrical nerve stimulation

(TENS)(TENS)

Treatment Options (contTreatment Options (cont’’d)d)

ManipulationManipulationTraction Traction MassageMassagePhysical therapy and exercisesPhysical therapy and exercisesAcupunctureAcupunctureCorsets and bracesCorsets and bracesSurgerical treatmentSurgerical treatment

ScoliosisScoliosis

A medioA medio--lateral lateral curve of the curve of the vertebral columnvertebral columnExceeding 10Exceeding 1000

–– TypesTypesStructural Structural NeuromuscularNeuromuscularIdiopathicIdiopathicNonNon--structuralstructural

–– TreatmentTreatmentExercisesExercisesBracingBracing

Detection of ScoliosisDetection of Scoliosis

KyphosisKyphosisAn exaggerated curvature in the An exaggerated curvature in the sagittal planesagittal planeLong rounded curveLong rounded curve((round backround back))Sharp posterior angulation Sharp posterior angulation ((hump backhump back))Possible causesPossible causes–– Wedge compression fractureWedge compression fracture–– Ankylosing spondylitisAnkylosing spondylitis–– Senile osteoporosisSenile osteoporosis–– Destructive tumors of spineDestructive tumors of spine

Video on description of Spinal ColumnVideo on description of Spinal Column

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