Mechanical-biological Factor Coupled Simulation For Osteoporotic Process Of Cortical Bone Endosteal

As a health problem, osteoporosis has caught all the world's attention andthere are more and more people pay more and more attention on it. For thepopulation aged, there is an increasing trend of the incidence of the osteoporosisthat is bad to the health of the elderly. Human's research regarding the relationbetween mechanical environment and bone's structure was from qualitativeanalysis to experimental research, and now to computational simulation. In 1884Wolff suggested an important hypothesis that bone grows where is needed andresorbs where isn't needed. That is to say, bone's growth, resorption andreconstruction are all relative to its mechanical environment. People usually call itWolff's Law. Roax (1895) set forth the principle of bone's functional adaptation,which means bone adapts to its function by practice. At the same time he indicatedthat by reproduction and atrophy bone has adapted to animal's living condition andaccorded with the maximal-minimal criteria, i.e. it has obtained the maximalstructural stiffness using the least material. The classical studies based onhypothesis of Wolff's Law show the general scheme for remodeling, which hasbeen studied qualitatively but not quantitatively, since heavy computing power areneeded to explore the implications of this theory. After 1970's, prevalentapplication of computer made it possible to quantify bone's functional adaptability.Computer simulation has recently been cited as the 'third method of science' afterlogic and experimentation. And several attempts to quantify the bone-remodelingprocess so as to investigate and predict the structure and remodeling behavior ofbone have been reported in the literature.At present it is a hot point to do computational simulation based on theoutcomes of certain experiments. In this dissertation, a mechanical-biologicalfactor coupled computational model at Basic Multicellular Units (BMUs) level wasput forward, which can describe osteoporotic process of cortical bone endostealwith time course based on the outcomes of some experiments. It was used tosimulate osteoporosis caused by disuse, and caused by decrease in mechanicalusage as well. And the contributions of mechanical factor and biological factor tothe development of osteoporosis were discussed.Why does bone loss in aging adults come from? Both mechanical usage andbiological factors have their contributions to this problem. Most aging adults losemomentary muscle strength and the intensity of their physical exercise becomesweaker. The effects of ageing, menopause, drug treatment are known as biologicalfactors, which could modulate the system by means of changing mechanicalthresholds, or changing the intensities of certain signals. The computational modelfor osteoporosis can provide theoretical basis and computational method for thetreatment and prevention of osteoporosis. However, little has been done in thisaspect of research all over the world. Hazelwood et al. put forward a mechanicalmodel of bone remodeling, which obtained different dynamical response inoverload and disuse, but it was difficult to realize the numerical simulation ofosteoporosis caused by biological factors. Hernandez and his colleagues put muchstress on biological factors, such as BMU activation frequency, bone-remodelingspace, peak bone mass, menopause, mineralization lag time to bone loss. In theircomputational models, mechanical factors were assumed as constant. During thedevelopment of ostroporosis, the effects of mechanical factors and biologicalfactors are coupled. It is necessary to build a mechanical-biological factor coupledcomputational model at Basic Multicellular Units (BMUs) level to be more inaccordance with the physiological process of bone remodeling.Based on bone functional adaptation and Frost's Mechanostat theory, amechanical-biological factor coupled computational model at Basic MulticellularUnits (BMUs) level was put forward following the physiology of bone remodeling,,which can describe osteoporotic process of cortical bone endosteal with timecourse. It was applied to simulate osteoporosis caused by disuse and aged. In thisarticle we discussed the results respectively two conditions when biological-factorwasn't induced and biological-factor was induced. The second result wereconsistent with clinical data presented. Furthermore, it can provide theoretical basisand computational method for the treatment and prevention of osteoporosis.The research in this dissertation was supported by Natural Science Foundationof China(10372034).