Research On Anisotropic Bone Remodelling Theory Model And Simulation Of Osteoporosis

Bone tissue has an ability to adapt to mechanical entironment , which is called bone functional adaptation. In 1884 Wolff suggested an important hypothesis that bone grows where is needed and resorbs where isn't needed . That is to say, bone's growth, resorption and reconstruction are all relative to its mechanical environment . People usually call it Wolff's Law. Wolff also pointed out that trabeculae are arranged along principal sress direction and trabeculae change their directions when principal sress directions happen to change . This indicates that adaptation of bone structure-to-mechanical entironment is anisotropic . There are two adjusting mechanisms at different level in bone tissue : cellular adjustming mechanism and tissue adjusting mechanism. Cellular adjustment mechanism is that the change of local mechanical entironment is perceived through biomechanical senses (osteocyte) in bone tissue , and then biomechanical senses transmit siganl to reactor cells (osteoblast,osteoclast) ,which arouses the change of bone structure. In 1987 Frost defined the mechanism adaptive to mechanical entironment in bone as mechanostat . Mechanostat reflects the relation between bone mass and strain . Mechanostat points out that bone tissue can adjust the relation between bone mass and strain through tissue level adjusting mechanism. The theory points out that bone can adapt to mechanical entironment by adjusting bone quality , bone quantity , structure , the integrality of microstructure . Bone is in a state of functional adaptation , when bone tissue strain is within the range of usual physiology strain . After 1970's , prevalent application of computer made it possible to quantify bone functional adaptability . Some researchers tried to express the concepts by using math equation to research and predict bone tissue structure and remodelling . There are several principles establishing reliable quantitative bone remodelling model . Firstly the process of simulation accords with bone physiologic accommodation fact . Secondly the result of simulation is correct . Quantitatively bone remodelling model is developed on the basis of bone physiologic accommodation, which accords with bone physiologic accommodation theory and embodies the anisotropy of remodelling process and mechanical property . Huiskes (1987, 1989, 1991) and Weinans (1992) described bone functional adaptability by using math method respectively. Their bone remodelling models were both isotropic models which canned not describe the anisotropy of bone remodelling process and bone mechanical property . Jacobs (1997) and Doblare (2002) put forward anisotropic bone remodelling models respectively . But their models did not embody bone physiologic accommodation mechanism . At present , many investigators have done much research on osteoporosis , and most focused on bone physiology and the effects of medicine to treat of osteoporosis . Thus biochemical markers of osteoporotic structure were often investigated. There are also many experiments dealing with the occurrence of osteoporosis , but unfortunately little is done about the basic quantitative model . By combining it with FEM the structure of bone can be predicated. The dissertation is quantitative research based on the actual physiology and results of many experiments . In this dissertation , new quantitative models of bone functional adaptation were put forward based on the bone physiologic accommodation process and the outcomes of some experiments . We investigated and discussed on the following two aspects: new quantitative bone remodelling models and computer simulation of osteoporosis . Most of works are as follows : 1 . Anisotropic bone remodeling self-organizational control model based on damage-repair theory was put forward . This model was applied to the study of the remodelling evolution of the proximal femur, results of apparent density and principal stresses trajectories were indicated similar toexperimental data . Anisotropic characteristic of the model was accordant with bone remodeling practical physiologic behavior and bone mechanical property . The introduction of self-organizational control process embodied cellular level mechanics apperception mechanism . 2 . Anisotropic bone remodelling model with mechanostat was developed . The model was applied to the study of the remodelling evolution of 2D squareplate model , obtaining very good results . The introduction of mechanostat made bone remodelling numerical simulation consistent with physiologic process . 3 . Anisotropic bone remodeling model based on wolff's law was put forward . Two implements methods were put forward in details . Simulations were done on cantilever beam model and simple supported girder model respectively to obtain very good results . The model was based on wolff's law . The technology of bone structure remodelling and prediction was studied in details . A new bone remodelling idea was put forward creatively to realize the anisotropy of bone remodelling process and bone mechanical property . The credible and perfect quantitative bone remodelling model can predict bone structure more accurately under mechanical entironment , which is important to study bone . The simulation and prediction of bone structure are the basis of bone biomechanics . It directly instruct clinic treatment of orthopaedics too , such as the design of orthopedic implement . At the same time it has widespread aspects in fields of medicine and biomedical engineering . 4 . Osteoporosis was simulated using anisotropic bone remodelling model with mechanostat combining with finite element method at meso-structural level . The effect of mechanical factor and biological factor on osteoporosis was simulated . Especially the process of osteoporosis in women was simulated at meso-structural level . The simulation results showed that pure menopause factor results to a fall of 7~12% bone mass . Bone mass declines 38.50%~40.44% from menopause to 80 years old . Commonly after 60 osteoporosis occurs in women . The prevention by physical activity were simulated with computer at the same time . The effect of load-dropping form on simulation result of osteoporosis in...