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Biomechanics in Human Body

Biomechanics in Human Body. الميكانيكية الاحيائية في جسم الانسان. Mechanics -study of forces and motions for the body. Mechanics. Statics deal with nonmoving parts (equilibrium). Dynamics deal with moving systems. Kinematics

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Biomechanics in Human Body

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  1. Biomechanics in Human Body الميكانيكية الاحيائية في جسم الانسان

  2. Mechanics-study of forces and motions for the body. 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

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

  4. Biomechanics Engineering (Mechanics) Anatomy Physiology 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 • Balance and stability • Centre of gravity • Elasticity • Forces (action & reaction) • pressure • power • Bending moment • Torque moment • Friction • Wear • Density • Momentum • Velocity • Time • Acceleration • Deceleration • Mass • Inertia • Dimensions • Viscosity

  7. Biomechanical principles associated with basic movement patterns Running Stopping

  8. General Motion Most movements are combination of both Linear motion Angular motion • Newton’s First Law • Law of inertia • Newton’s Second Law • Law of Acceleration • Newton’s Third Law • Law of Action and Reaction

  9. JOINTREACTIONFORCES

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

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

  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: • Mechanical advantage = • ResistanceForce • or • Mechanical advantage = • Length of force armLength of resistance arm

  21. Biomechanics of the denture Bitting Force • Human female bite = 360 N • Human male bite = 564 N • Boxer can punch with 10,528 N 18 • Lion bite down with 5,533 N 10 • Dog bite = 1,410 N2.5

  22. Fluid biomechanics (blood flow). Vascular Biomechanics • Continuity Equation: • mass in = mass out Q = ((P1-P2)..R4)/(8.µ.L) Assumptions - Laminar Flow - Newtenian fluid - Incompressible fluid - Single phase

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

  24. Atherosclerosis

  25. Velocity Pathlines • Steinman, 2000

  26. Wall Shear Stress Contours Augst et al, 2007 Jamalian Ardakani, 2010 In healthy vessels, tw 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 material • (modulus is dependent upon the direction of loading). • Bones are: • strongest in compression. • weakest in shear. • Ultimate Stress at Failure Cortical Bone • Compression < 212 N/m2 • Tension < 146 N/m2 • Shear < 82 N/m2

  29. Mechanical Properties of Bone • DuctileorBrittle • Depends on ageand rate at which it is loaded • - Younger bone is more ductile • - Bone is more brittle at high speeds return to original shape after fracture

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

  31. Bending of a Long, Solid Bone: Tension Tension Bending of a Long, Hollow Bone:  =M . y / I Stress Free in the middle I = .(R4-r4)/4 Compression Compression Save weight & keep strength:

  32. Biomechanics Bone fixation External fixation Internal fixation

  33. Biomechanics of External Fixation • Number of Pins • Two per segment • At least 3 pins

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

  35. Biomechanics of Internal Fixation Plate Fixation • Functions of the plate Compression Neutralization Buttress

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

  37. Biomechanical principlessimilar to those of external fixators Stress distribution

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

  39. Treatment or Total Knee Replacement • Moving surfaces of the knee are • metal against plastic UHMWPE

  40. Structural Alignment Genu Varum (Bowlegged) Genu Valgum (knock kneed) Hyperextension

  41. Biomechanics of Flat Foot

  42. Biomechanics of motion of human body Gait Cycle Swing Phase Stance Phase Heel Strike Midstance Toe off To design artificial lower limb

  43. Ground reaction force (by force plate “platform”) 1.3 W

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

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

  46. Numerical Study of Prosthetic Socket

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

  48. Contours of Equivalent Von Mises Stress Distribution Contours of Deformation Distribution

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