biomechanics notes

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UNIT I Introduction to Biomechanics: Biomechanics has participated in virtually every modern advance of medical sciences and technology.Itisatoolfordesignandinventionofdevicestoimprovethequalityoflife.The methodofbiomechanicsisthemethodofengineering,whichconsistsofobservation, experimentation, theorization, validation and application. It is the branch of science that explains the mechanics of life and living. From molecules to organisms, everything must obey the laws of mechanics. What is Biomechanics? Mechanics - Study of action of forces on particles and mechanical systems. Bio Prefix for life/living organisms Biomechanics - Applicationoftheprinciplesofmechanicstothestudyoflivingorganisms(i.e) application of mechanical principles to living organisms. Basic concepts in Biomechanics: The study of biomechanics ranges from the inner workings of a cellto the movement and developmentoflimbs,thevasculature,themechanicalpropertiesofsofttissueandbones.By applyinglawsandconceptsofphysics,biomechanicalmechanismsandstructurescanbe simulated and studied. This includes bioengineering, the research and analysis of the mechanics oflivingorganismsandapplicationofengineeringprinciplestoandfrombiologicalsystems. Researchandanalysiscanbecarriedforthonmultiplelevelsfromthemoleculeswherein biomaterials such as collagen and elastin are considered, up to tissue and organ level. Simple examples of biomechanics research include the investigation of forces that act on limbs,theaerodynamicsofbirdandinsectflight,thehydrodynamicsofswimminginfish, general locomotion in all forms of life from individual cells to whole organisms. The biomechanics of human beings is core part of Kinesiology. Plant biomechanics is application of biomechanical principles to plant and plant organs. Fieldswhichplayprominentroleinstudyofbiomechanicsare,thermodynamicsand continuummechanicsinAppliedMechanicsandfluidmechanicsandsolidmechanicsin mechanical engineering. Biomechanics as a sports science, Kinesiology where laws of mechanics and physics areappliedtounderstandhumanphysiologyandperformanceinathleticeventsthrough modeling, computer simulation, stimulation, gesticulation, mastication and measurement. Common methods used for analysis: Elements of mechanical engineering ( eg. Strain gauge) Electrical engineering (eg. Digital filtering) Physics/Dynamics (eg. Moment of inertia) Computer science (eg. Numerical methods) And Clinical neuron physiology (eg. Surface EMG) Relevantmathematicaltoolsincludelinearalgebra,differentialequations,vectorand tensor calculus, numerics and computation techniques such as finite element method. The study ofbiomaterialsisalsoofcrucialimportancetobiomechanics.Forexamplethevarioustissues withinthebodyorganssuchasskin,boneandarterieseachpossessuniquematerialproperties. Passive mechanical response of a particular tissue can be attributed to characteristics of various proteins,suchaselastin,collagen,livingcells,groundsubstancesproteoglycansandthe orientations of fibers with in the tissue. For example if human skin is largely composed of a protein other than collagen many of itsmechanicalpropertiessuchasitselasticmoduluswouldbedifferent.Alsothepropertiesof living tissue can be affected by applied loads and deformations. Ingeneral,humanmovementisbroughtaboutbythemusculoskeletalsystem (skeleton,joints,skeletalmuscles)underthecontrolofnervoussystem.Allmovementsand changes in movements are brought about by action of forces. Two most common types of forces arepushingandpullingbuttherearemanyvariationssuchas,liftingabookfromatable, holding a pen, turning a door handle, kicking a ball and throwing a discus. The muscles pull on thebonesinordertocontrolthemovementsofthejointsandindoingso,controlsthewhole body movement. Keytounderstandbiomechanicsisthoroughunderstandingofconceptsofforce, Newtons laws of motion, work and energy. Scope of Biomechanics in Medicine: Sincebiomechanicsisthescienceinvolvingthestudyofbiologicalsystemfroma mechanical perspective, it is helpful -to address problems related to human health and performance -tounderstandhowcertainphysiologicalsystemfunctions(eg.Cardiovascular system) -To model the system -To aid in the system of prosthesis Scope in Medicine field: -Molecular biology -Surgery -Cardiovascular system -Orthopedics -Trauma -Atheroscelerosis -Endothelial cells -Pulmonary organs Molecular Biology: Makes understand the formation, design, function and production of molocules. Surgery: Eventhoughthisseemstobeunrelatedtomechanics,yethealingandrehabilitationare intimately related to the stress and strain in tissues. CardioVascular system: Inventionandanalysisofprosthesisheartvalves,developmentofheartassistdevices, extracorporealcirculationdevices,heart-lungmachinesandtheheamodialysismachines.Also in heart transplantation and artificial heart replacement. Trauma: Helpssolvingproblemsofpostoperativetrauma,pulmonaryedema,pulmonary atelectasis, arterial pulse wave analysis, phonoangiography. Atheroscelerosis: Analysisofturbulentnoiseasindicationsofatheroscelerosisorstenosisinarteries.Itis studied intensely as a heamodynamics disorder because the locations ofatheroscelerotic plaques seems to correlate with certain features of blood flow. Endothelial cells: Stress acting in endothelial cells and response of endothelial cells to the stress are studied for treatment. Orthopedics: Mostfrequentusersofthesurgeryroomsarepatientswithmusculoskeletalproblems. Biomechanics is used in surgery planning, for prosthesis, implantable materials Andartificiallimbs.Alsoincellularandmolecularaspectsofhealinginrelationtostressand strain and in tissue engineering of cartilage, tendons and bones. Veryimportantly,applicationofbiomechanicsintraumaandinjury&rehabilitationis becoming more essential to society. Because people injured automobile road accidents and other incidences are younger and hence the economic impact on the society is bigger. Biomechanics in sports and exercise: Biomechanicsofsportsandexerciseisthestudyoftheforcesthatactonandwithin the human body and the effects of these forces on the size, shape, structure and movement of the body.Insportsandexercise,biomechanicsisthescienceunderlyingtechnique,everytimea coach / instructor attempts to improve an individuals technique (i.e) to improve the coordination of the forces produced by various muscle groups. [Mechanics of individual movement] Benefits of Biomechanics: Greater understanding of physiological behavior of living tissues, researchers are able to advance the field of tissue engineering as well as develop improved treatment for a wide array of pathologies. Applications of Biomechanics: -Improving physical function (Surgery planning in cerebral palsy) -Musculoskeletal Health (Replacing injurious falls by older adults preventing bone loss) -Product design (Athletic shoes, Prosthetics) -Forensic Biomechanics (Accident Investigation) Uses of Biomechanics: -Improvingsportsperformancebymeansofbettertechniqueandtrainingandalso better equipment -Sports injury byidentifying safer techniques, reducing therisk of injuryby training, and also by developing protective equipments( eg. Knee brace) -OccupationalInjuryprevention[Ergonomics]eg.Lowbackpain,hand&wrist trauma -Injury rehabilitation by identifying when safe to return to activity Who uses Biomechanics? Physicaleducationteachers,Coachers,Trainers(personal/Athletic),Physicians, Athletes, Physical Therapist, Occupational Therapist, Engineers and Researchers. Mechanics of Hard Tissue: Hard tissue, mineralized tissue and calcified tissue are the bone synonyms for describing structureandpropertiesofbone/tooth,whereassofttissuesarenothingbutmammaliantissue. Mineralized and calcified in the sense in addition to principle protein Collagen and other proteins Glycoprotein and Polysaccharides comprising about 50% of the volume, the major constituent of boneisCalciumPhospate,intheformofcrystallinecarbonateapatite,similartonaturally occurring minerals. Bones: Skeletal structures are adapted to support musculoskeletal loads. The structural properties andfailureforceofskeletalstructureiswelladaptedtofunctionalloads.Theprimary responsibilityoftheskeletonistoprovidestructuralsupportforthebody.Inthisrole,the skeletonisthebasisofposture,opposesmuscularcontractionresultinginmotion,withstands functional load bearing function and protects internal organs. Bones are rigid organs that forms part of the endoskeleton of vertebrates. Theyfunction to move, support and protect the various organsof the body, produce red and white blood cells andstoreminerals.Bonetissueisatypeofdenseconnectivetissue.Becausebonescomeina varietyofshapesandhaveacomplexinternalandexternalstructuretheyarelightweight,yet strongandhard,inadditiontofulfillingthismanyotherfunctions.Oneofthetypesoftissues thatmakesupboneinisthemineralizedOsseous tissue,alsocalledbone tissue.Thisgivesits rigidity and a honey comb like three dimensional internal structure. Other types of tissues found intheboneincludesbonemarrow,endosteumandperiosteum,nerves,bloodvesselsand cartilage. Generally, adults have 206 bones and infants have about 300 bones. The Longest bone found in humans is thigh bone called Femur.Definition and properties: Boneisananisotropic,heterogeneous,inhomogeneous,nonlinear,thermorheologically, complexviscoelasticmaterial.Itexhibitselectromechanicaleffects,presumedtobedueto streaming potentials both in vivo and in vitro when wet. It exhibits piezoelectric properties in dry state. Composition of Bone: Thecompositionofbonedependsonalargenumberoffactorssuchasspecies,which bone,locationfromwhichthesampleistaken,agesex,typeofbonetissue.Byvolume,rough estimateforoverallcompositionisonethirdofApatitecrystallites,onethirdofCollagenand other organic components and one third of water. Composition of human bones is given as1)water 25-30% 2)Minerals 60-70% (resists compression) Calcium phosphate 85% Calcium carbonate 10% Calcium fluoride 2-3% Magnesium fluoride 2-3% 3)Protein(Collagen) 5-