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

SpineSpine

Cervical SpineCervical Spine

Seven vertebrae Seven vertebrae – C 1-7C 1-7

More flexibleMore flexible Supports the headSupports the head Wide 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

Mid-back or dorsal regionMid-back or dorsal region Twelve vertebrae Twelve vertebrae

– T 1-12T 1-12

Ribs attached to vertebrae Ribs attached to vertebrae Relatively immobileRelatively immobile Peripheral nervesPeripheral nerves

– IntercostalIntercostal

Lumbar SpineLumbar Spine

Lower backLower back Five vertebrae Five vertebrae

– L 1-5L 1-5

Carries 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 organs

CoccyxCoccyx– Few small bonesFew small bones– Remnant of tailRemnant of tail

LordosisLordosis

In the sagittal planeIn the sagittal plane– ‘‘S’ shapeS’ shape

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 spring-like actionAllows spring-like action

Compressive Strength of SpineCompressive Strength of Spine

Stress-Strain CurveStress-Strain Curve

Failure Strength of Spinal LigamentsFailure Strength of Spinal Ligaments

Motion SegmentMotion Segment

Two adjacent vertebraeTwo adjacent vertebrae Intervertebral discIntervertebral disc Six degrees of freedomSix degrees of freedom

– Flexion-extensionFlexion-extension– 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 fibro-cartilaginous cushionsSoft fibro-cartilaginous cushions– Between two vertebraBetween two vertebra– Allows some motionAllows some motion– Serve as shock absorbersServe as shock absorbers

Total – 23 discsTotal – 23 discs ¼¼ thth of the spinal column's length of the spinal column's length Avascular 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– FlexibilityFlexibility

Act to pad and maintain the space between Act to pad and maintain the space between the twenty-four movable vertebraethe twenty-four movable vertebrae

Act as shock absorbersAct as shock absorbers Allow 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 tire–like structure Strong radial tire–like structure Series of lamellaeSeries of lamellae Concentric 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 pulposusEncloses nucleus pulposus

AnnulusAnnulus

In Bending In Bending – Increased tensile force posteriorly Increased tensile force posteriorly – Increased compressive force anteriorlyIncreased compressive force anteriorly

In 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 PGs PG are macro-molecules PG are macro-molecules

– Attract and retain waterAttract and retain water– Hydrophilic gel–like matter Hydrophilic gel–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 water Develops internal pressureDevelops internal pressure Pressure 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 (cont’d)Theory of weight bearing (cont’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 shear Similarly under normal physiologic activitiesSimilarly under normal physiologic activities

– Pure tensile loading doesn’t occurPure tensile loading doesn’t occur– But annulus undergoes tensile loading duringBut annulus undergoes tensile loading during

Bending Bending Axial rotationAxial rotation ExtensionExtension

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 L3-Inserted in vivo in L3-4 disc4 disc

Pathology of Intervertebral Disc InjuryPathology of Intervertebral Disc Injury

Annular InjuryAnnular Injury– Annular rings Annular rings

SoftenedSoftened Overstretched 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 mechanism Nerve 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 back To 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 LBP of LBP

DysfunctionDysfunction Predisposing 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 crest Posterior superior iliac spine (PSIS)Posterior superior iliac spine (PSIS) Anterior superior iliac spine (ASIS)Anterior superior iliac spine (ASIS) Spinous processesSpinous processes Muscle tightnessMuscle tightness GaitGait

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 bending

Hands are pushing in Hands are pushing in opposite directionopposite direction

Tissues from skin to Tissues from skin to central corecentral core– Elongate posterior Elongate posterior – Compress anteriorCompress anterior

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

to pelvisto pelvis

Back ExaminationBack Examination

Nerve tension signsNerve tension signs Nerve 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 flexion of flexion

Passive hip flexionPassive hip flexion

Hip hyperflexedHip hyperflexed– Lumbar spine flattened Lumbar spine flattened

Over 90Over 9000 of flexion of 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 raised Femoral flexionFemoral flexion AdductionAdduction Internal rotationInternal rotation Increase 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 pain Modalities Modalities MedicationMedication

– Support the regionSupport the region– Biomechanical counseling / restBiomechanical counseling / rest

Continue supportContinue support– Begin non-destructive movementBegin non-destructive movement– Decrease destructive behaviorDecrease destructive behavior

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

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

Neuromuscular efficiencyNeuromuscular efficiency Dynamic stabilizationDynamic stabilization

Establishment of limitsEstablishment of limits MovementMovement LoadsLoads PositionsPositions Frequencies Frequencies

Treatment OptionsTreatment Options

CryotherapyCryotherapy ThermotherapyThermotherapy

– Superficial heatingSuperficial heating– Deep HeatDeep Heat

Injection Therapy & Soft tissue injectionsInjection Therapy & Soft tissue injections ElectrotherapyElectrotherapy

– Transcutaneous electrical nerve stimulation Transcutaneous electrical nerve stimulation (TENS)(TENS)

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

ManipulationManipulation Traction Traction MassageMassage Physical therapy and exercisesPhysical therapy and exercises AcupunctureAcupuncture Corsets and bracesCorsets and braces Surgerical treatmentSurgerical treatment

ScoliosisScoliosis

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

– TypesTypes Structural Structural NeuromuscularNeuromuscular IdiopathicIdiopathic Non-structuralNon-structural

– TreatmentTreatment ExercisesExercises BracingBracing

Detection of ScoliosisDetection of Scoliosis

KyphosisKyphosis

An exaggerated curvature in the An exaggerated curvature in the sagittal planesagittal plane

Long 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

http://www.spineuniverse.com/displayarticle.http://www.spineuniverse.com/displayarticle.php/article1331.htmlphp/article1331.html