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Biomechanics in Human Body الميكانيكية الاحيائية في جسم الانسان.

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Presentation on theme: "Biomechanics in Human Body الميكانيكية الاحيائية في جسم الانسان."— Presentation transcript:

1 Biomechanics in Human Body الميكانيكية الاحيائية في جسم الانسان

2 Mechanics Statics deal with nonmoving parts (equilibrium). Dynamics deal with moving systems Kinematics Describes motion and includes consideration of time, displacement, velocity, acceleration and mass. Kinetics Describes forces that cause motion of a body -study of forces and motions for the body. Mechanics -study of forces and motions for the body.

3 Basic Biomechanics -apply mechanics to the structure and function of the human body.Biomechanics -apply mechanics to the structure and function of the human body. Is the scientific study of the mechanics of biological systems.

4 Engineering (Mechanics) Anatomy Physiology Biomechanics Applications Biomechanics - Improved the performance ( Human movement) - Preventing or treating injury - Design prosthesis & orthosis or artificial limb

5 Biomechanics Biomechanics is be used to: –To understand the biomechanical analysis (motion) (Gait cycle) (for normal and patient human). –To understand function of vascular system in order to analysis the fluid biomechanics (blood flow). –To analysis the biomechanics of : soft tissue (muscle) hart tissue (bones). –To model these systems to aid in the design of prosthetic devices (e.g. artificial artery or artificial limb)

6 Principles associated to biomechanical analysis Density Momentum Velocity Time Acceleration Deceleration Mass Inertia Dimensions Viscosity Balance and stability Centre of gravity Elasticity Forces (action & reaction) pressure power Bending moment t Torque momen t Friction Wear

7 Biomechanical principles associated with basic movement patterns forces forces acceleration and deceleration acceleration and deceleration Newtons laws Newtons laws friction friction Stopping Running forces (action/ reaction) forces (action/ reaction) motion (straight line) motion (straight line) momentum momentum friction friction

8 General Motion Most movements are combination of both Newtons First Law – Law of inertia Newtons Second Law – Law of Acceleration Newtons Third Law – Law of Action and Reaction Linear motion Angular motion


10 Loads The external forces that act on the body impose loads that affect the internal structures of the body.

11 First class lever There are 3 classes of levers. Second class leverThird class lever Humans moves through a system of levers

12 First Class Levers Up and down movement of the head about the atlas joint.

13 First Class Levers Using a crowbar to move a rock.

14 First Class Levers Using a hammer to pull out a nail.

15 First Class Levers A see-saw.

16 Second Class Levers The movement of the foot when walking. (the calf muscle provides the effort and the ball of the foot is the pivot)

17 Second Class Levers Opening a bottle with a bottle opener

18 Second Class Levers Pushing a wheel barrow.

19 Third Class Levers Biceps curl.

20 Levers The mechanical advantage of levers may be determined using the following equations:The mechanical advantage of levers may be determined using the following equations: Mechanical advantage = Resistance Force or Mechanical advantage = Length of force arm Length of resistance arm

21 Bitting Force Dog bite = N Dog bite = 1,410 N 2.5 Lion bite down with 5,533 N 10 Boxer can punch with 10,528 N 18 Human female bite = NHuman female bite = 360 N Human male bite = NHuman male bite = 564 N Biomechanics of the denture

22 Continuity Equation: mass in = mass out Assumptions - Laminar Flow - Newtenian fluid - Incompressible fluid - Single phase Fluid biomechanics (blood flow). Vascular Biomechanics Q = ((P 1 -P 2 )..R 4 )/(8. µ.L)

23 Atherosclerosis Blood viscosity 0.0035 kg/m.s Blood density 1060 kg/m3

24 Atherosclerosis

25 Velocity Pathlines Steinman, 2000 Steinman, 2000

26 Wall Shear Stress Contours Augst et al, 2007Jamalian Ardakani, 2010 In healthy vessels, w is low (~ 15-20 dynes/cm)

27 Velocity Pathlines Model 1 (peak of systole)Model 1 (peak of diastole)

28 Bone Biomechanics (Hard tissue) Bone is anisotropic materialBone is anisotropic material (modulus is dependent upon the direction of loading). Bones are: strongest in compression. weakest in shear. Ultimate Stress at Failure Cortical BoneUltimate Stress at Failure Cortical Bone Compression < 212 N/m 2 Compression < 212 N/m 2 Tension < 146 N/m 2 Tension < 146 N/m 2 Shear < 82 N/m 2 Shear < 82 N/m 2

29 Mechanical Properties of Bone return to original shape after fracture Ductile or Brittle Depends on age and rate at which it is loaded - Younger bone is more ductile - Bone is more brittle at high speeds

30 Bending Type of Loading Torsion Axial Loading Compression Tension Fracture Mechanics Bending load: –Compression strength greater than tensile strength –Fails in tension

31 Tension Compression Stress Free in the middle Bending of a Long, Solid Bone: Save weight & keep strength: Tension Compression Bending of a Long, Hollow Bone: =M. y / I I =.(R 4 -r 4 )/4

32 Biomechanics Bone fixation External fixation Internal fixation

33 Biomechanics of External Fixation Number of PinsNumber of Pins –Two per segment –At least 3 pins


35 IM Nails (Rod) Stiffness is high proportional to the 4 th power. Biomechanics of Internal Fixation

36 Plate Fixation Functions of the plate Compression Neutralization Buttress Biomechanics of Internal Fixation


38 Bending moment = F x D F = Force D D = distance from force to implant F = Force D The bending moment for the plate is greater due to the force being applied over a larger distance IM Nail Plate

39 Biomechanical principles similar to those of external fixators Stress distribution

40 Osteoarthritis may result from wear and tear on the joint The medial (inside) part of the knee is most commonly affected by osteoarthritis.

41 Moving surfaces of the knee are metal against plastic Treatment or Total Knee Replacement UHMWPE

42 Structural Alignment Hyperextension Genu Valgum (knock kneed) Genu Varum (Bowlegged)

43 Biomechanics of Flat Foot

44 Gait Cycle Swing Phase Stance Phase Heel Strike MidstanceToe off Biomechanics of motion of human body To design artificial lower limb

45 Ground reaction force (by force plate platform) 1.3 W

46 Hip, knee, and ankle joint centers lie along a common axis. - Socket alignment -Static alignment -dynamic alignment Biomechanics of motion of human body

47 (Interface pressure sensor between socket and skin) Numerical Study of Prosthetic Socket


49 Theoretical Part -Stress - Max. Normal Stress - Max. Shear Stress - Von Mises stress -Deformation - Linear - Angular -Fatigue ratio -Strain energy -Failure index -Safety factor

50 Contours of Deformation Distribution Contours of Equivalent Von Mises Stress Distribution

51 Thanks you for listening

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