Biomechanics in Human Body
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
Basic Biomechanics • Biomechanics-apply mechanics to the structure and function of the human body. Is the scientific study of the mechanics of biological systems.
Biomechanics Engineering (Mechanics) Anatomy Physiology 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 • 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
Biomechanical principles associated with basic movement patterns Running Stopping
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
Loads The external forces that act on the body impose loads that affect the internal structures of the body.
Humans moves through a system of levers There are 3 classes of levers. First class lever Second class lever Third class lever
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 = • ResistanceForce • or • Mechanical advantage = • Length of force armLength of resistance arm
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
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 • DuctileorBrittle ( is a solid material's ability to deform under tensile stress) • Depends on ageand 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. return to original shape after fracture
Type of Loading Fracture Mechanics Bending Torsion • Bending load: • Compression strength greater than tensile strength • Fails in tension Axial Loading Compression 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
Biomechanical principlessimilar to those of external fixators Stress distribution
Treatment or Total Knee Replacement • Moving surfaces of the knee are • metal against plastic UHMWPE
Biomechanics of motion of human body Gait Cycle Swing Phase Stance Phase Heel Strike Midstance Toe off To design artificial lower limb