Biomechanics in Human 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

Mechanics-study of forces and motions for the body.

Basic Biomechanics

• Biomechanics-apply mechanics to the structure and function of the human body.

Is the scientific study of the mechanics of biological systems.

Engineering(Mechanics)

Anatomy Physiology

Biomechanics

Applications Biomechanics

- Improved the performance ( Human movement)- Preventing or treating injury- Design prosthesis & orthosis or artificial limb

Biomechanics• Biomechanics is be used to:

–To understand the biomechanical analysis (motion) 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)

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• Torque moment

• Friction• Wear

Biomechanical principles associated with basic movement patterns

forcesacceleration and decelerationNewtons lawsfriction

StoppingRunning

forces (action/ reaction)motion (straight line)momentumfriction

General Motion

Most movements arecombination of both

• Newton’s First Law–Law of inertia

• Newton’s Second Law–Law of Acceleration

• Newton’s Third Law–Law of Action and

Reaction

Linear motion

Angular motion

JOINTREACTIO

NFORCES

LoadsThe external forces that act on the body impose loads that affect the internal structures of the body.

First class lever

There are 3 classes of levers.

Second class lever Third class lever

Humans moves through a system of levers

First Class Levers

Using a crowbar to move a rock.

First Class Levers

Using a hammer to pull out a nail.

First Class Levers

A see-saw.

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)

Second Class Levers

Opening a bottle with a bottle opener

Second Class Levers

Pushing a wheel barrow.

Third Class Levers

Biceps curl.

Levers• The mechanical advantage of levers may be

determined using the following equations:Mechanical advantage =

ResistanceForceor

Mechanical advantage =Length of force arm

Length of resistance arm

Bitting Force

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 = 360 N• Human male bite = 564 N

Biomechanics of the denture

Bone Biomechanics (Hard tissue)

• Bone is anisotropic material (An anisotropic material is a material which does not behave the same way in all directions.)

• 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

Mechanical Properties of Bone

return to original shape after fracture

Ductile or Brittle ( is a solid material's ability to deform under tensile stress)

Depends on age and rate at which it is loaded

- Younger bone is more ductile- Bone is more brittle at high speeds

Brittle hard but liable to break easily.

Bending

Type of Loading

TorsionAxial LoadingCompressionTension

Fracture Mechanics

•Bending load:– Compression strength greater

than tensile strength– Fails in tension

Biomechanics Bone fixation

External fixation

Internal fixation

Biomechanics of External Fixation

• Number of Pins– Two per segment– At least 3 pins

Biomechanics of Internal Fixation

Plate Fixation• Functions of the plate Compression Neutralization Buttress

Biomechanics of Internal Fixation

Biomechanical principlessimilar to those of external fixators

Stress distribution

• Moving surfaces of the knee are metal against plastic

Treatment or Total Knee Replacement

UHMWPE

Biomechanics of Flat Foot

Gait Cycle

Swing Phase

Stance Phase

Heel Strike Midstance Toe off

Biomechanics of motion of human body

To design artificial lower limb

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