basic biomechanic

8/16/2019 Basic Biomechanic

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Basics of Musculoskeletal

Biomechanic

Ahmad Fauzi

Divisi Orthopaedi & Traumatologi

Ilmu Bedah FK !I"A


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• Biomechanic of Trauma

• Biomechanic of The Hip

• Biomechanic of The Knee• Biomechanic of The Ankle


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BIOM#$%A!I$ OF TAMA

'Fracture(


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BIOM#$%A!I$)

• The study of forces acting on & generated within

the body

• The study of forces & their effects on living

biologic systems

• Interdisciplinary approach anatomy! physiology!

mechanics! medicine! engineering! psychology"


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• Basis of biomechanical principle # $ewton%s

aws

' *st "a+ , Body will remain at rest ( move witha constant velocity if the resultant force acting

on it is e)ual to *ero+


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!e+ton-s "a+s

• .nd "a+ , If the resultant force acting is not e)ual

to *ero the body will have an acceleration thatis directly proportional to the magnitude of the

force & inversely proportional to the mass

•/rd

"a+ , ,or every action

reaction e)ual inmagnitude & opposite in direction


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Basic Biomechanics

,orce! -isplacement & .tiffness

AppliedForce

-isplacement

.lope / .tiffness /

,orce(-isplacement


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• oads # ,orces that act an a body

0ompression! tension! shear! torsion "

• -eformations # Temporary elastic" orpermanent 1lastic " change in the shape of the

body+ 0hange in load produce changes in

deformation


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Basic Biomechanics

• 2lastic -eformation

• 1lastic -eformation• 2nergy

#nerg0

A1sor1ed

,orce

-isplacement

1lastic2lastic


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• .trength of bone composite structure

' collagen providing the tensile strength &

' hydro3yapatite providing the compressive

strength


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• $ormal cortical bone lamellar bone" highly

organi*ed and relatively hypocellular

• $ortical 1one 456 of the skeleton!

' 0omposed tightly packed Haversian system!

' 0haracteri*ed # slow bone turnover rate

Bone Biomechanics


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• $ancellous 1one less dense!

' Higher turnover rate! and

' 7ndergoes greater remodelling according

to the lines of stress 8olff%s law"


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)chematic Diagram of a "ong Bone


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Bone Biomechanics

• 1roperties of the bone that important in resisting

a fracture #

' 2nergy absorbing capacity!

' 9oung%s modulus of elasticity E " represents the material stiffness & ability to

resist deformation when a force is applied

$/:;" or 1ascals 1a"+ ' ,atigue strength! and

' -ensity


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Fracture Biomechanics

• ,actors for production of fractures ' :agnitude!

' -uration!

'-irection of the forces acting on the bone! and

' The rate at which the bone is loaded

• 1rincipal stress planes

Bending

A3ial loading # tension! compression

Torsion


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• 0haracteristics of the force causing fractures

' single force of significant magnitude! or

' repetitive low magnitude forces

• 0lassified by :echanism of In


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• 0ombination of the bone%s material strength &

e3cessive anisometric e3t load stress properties

FA$T# & 2attern of fracture


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• Bending

• A3ial oading

' Tension ' 0ompression

• Torsion

Bending 0ompression Torsion


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,igure from# Browner et al# .keletal Trauma ;nd 2d! .aunders! =>>4+


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The Fracture 2attern of "ong Bones

$orresponding to the T0pe of #3ternal "oad


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• Bending load,

' 0ompression strength ?

tensile strength

' ,ails in tension

,igure from# Tencer+ Biomechanics in @rthopaedic

Trauma! ippincott! =>>+


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• 0ombined bending & a3ial load ' @bli)ue fracture

' Butterfly fragment

,igure from# Tencer+ Biomechanics in @rthopaedic



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Torsion

• The diagonal in the direction of the applied force

is in tension cracks perpendicular to this

tension diagonal

• .piral fracture C to the long a3is

,igures from# Tencer+ Biomechanics in @rthopaedic



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esultant Tension $rack 10 a Torsional "oad


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,ractures

• A single trauma incident

• Depetitive stress

• Abnormal weakening of the bone


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• :ost ,ractures are caused sudden and

e3cessive force

' -irect force

' Indirect force


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A direct force

• The bone breaks at the point of impact

' .oft tissues also must be damaged

' a direct blow usually causes a transverse

fracture and damage to the overlying skin

' 0rushing E comminuted fracture with

e3tensive softFtissue damage


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A direct force


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A direct force


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A direct force


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A direct force


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An indirect force

• The bone breaks at a distance from where force

is applied

• .oftFtissue damage at the fracture site is not

inevitable• Almost fractures are due to a combination of

forces


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• Bending

• Tensile

• 0ompression• Twisting


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An indirect force


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)pine


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.ummary• Biomechanics # The study of forces acting on &

generated within the body

• Basis of biomechanical principle # $ewton%s

aws

• 0ombination of the bone%s material strength &e3cessive anisometric properties cause fracture

• :echanism of in


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Biomechanic of The %ip


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• Anatomical considerations

The Acetabulum

The ,emoral Head

The ,emoral $eck

• Kinematics

Dange of :otion .urface


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• @ne of the largest and most stable


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Anatomy

• 0omposed of #

Head of femur

Acetabulum of pelvis

• =4 = >

• 8ide range of motion

• 8alking! sitting! s)uatting


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Anatomy

• .urrounding large! strong muscles


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Acetabulum

• 0oncave component of ball

and socket joint

• 0over with articularcartilage

• 1rovide with static stability


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The femoral head

• ,emoral head # conve3 component

• TwoFthird of a sphere

• 0over with cartilage

• Dydell =>" suggested # most load

superior )uadrant


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The femoral neck

• ,rontal plane the neckFtoFshaft angle"

• Transverse plane the angle of anteversion"


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• $eckFtoFshaft angle #

=;C! vary from >5C to =JC

• 2ffect # lever arms


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$eckFtoFshaft angle & Abductor muscle

force


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• Angle of anteversion # =;C

• 2ffect # during gait

?=;C # internal rotation

=;C # e3ternal rotation


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medial trabecular systemmedial trabecular system

Joint reaction forceJoint reaction force

Frankel4 *567


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Kinematics

• Hip motion takes place in all three planes #

sagittal fle3ionFe3tension"

frontal abductionFadduction"

transverse internalFe3ternal rotation"

• :uscle! ligament and configurationL

asymmetric


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Kinematics

• Dange of motion # sagittal! frontal! transverse

0~1400~140 0~300~300~150~15 0~250~250~900~90 0~700~70


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Kinematics

@ld man # shorterstrides

• -ecrease#

Dang of hip fle3ion!

e3tension

1lantar fle3ion of ankle

HeelFfloor angle

Old man Young man


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Biomechanic of The Knee


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• Ti1iofemoral 8oint

J plane# sagital! frontal! transversal


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Instant center T,


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0ontact point

• Tangensial / gliding

2 t i fl i di t ti i


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23tension ' fle3ion distraction ' compression


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Meniscus


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Biomechanic of The Ankle

Ankle Goint Biomechanics


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• Ankle -orsifle3ion

' Anterior Talar -ome

8ider

' :ore .tability ' :ore Tibiotalar 0ontact

' ,ibula :oves aterally


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• Tibial 1lafond Jo Malgus


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Arch .upport


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Arch .upport

• Beam and Truss

• $o :uscle Activity with

Dela3ed .tanding

• 1lantar ,ascia


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!ormal 9ait

• Bipedal :ode of ocomotion

• Noals

' :obility ' :inimal 2nergy 23penditure

' :inimal .tress on

• Bones

• Goints

• :uscles

!ormal 9ait


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!ormal 9ait


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!ormal 9ait

Heel .trike,latfootHeel DiseToe @ff

)TA!$# 2%A)#):I!9 2%A)#


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• 8eightFBearing 1rogresses fromateral Heel to Nreat Toe


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basic biomechanic

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