Supplementum 1+2/2010 - Společnost pro pojivové tkáně

to possibility to study several concrete bonerelated diseases using this model.RANKL-RANK-OPG pathway mediatesmany of the above mention biochemicalfactors. Moreover, RANKL levels alsoreflect microcrack density. Hence, it isessential to incorporate this pathway intoour model. The connection will be enabledthrough the amount RANKL-RANK bondsthat are one of the components of thedeveloped model, noted as RR. Kineticsof RANKL-RANK-OPG pathway was addedwhich enables us to add other biochemicalfactors that are actually translated throughthis pathway as NO, estradiol.ResultsWe may now simulate the response ofbone remodelling to changing environment,both mechanical and biochemical.Similarly, as was described in our previouswork, density distribution patterns may beobtained using FEM. The results from theprevious section will be used.Example – menopause: During menopause,a decline in estradiol levels occur. Insome women, the decrease is very dramatic(a drop bellow 5 pg/ml is observed, whereasa standard serum level is 40–60 \pg/ml)while in some not (serum level remainsabove 20 pg/ml). Further it was observedthat, together with estradiol, there is a declinein nitric oxide levels. An example ofa woman who is physically active (correctmechanical stimuli on regular daily basis,i.e. approximately 20000 steps per day) butin a consequence of menopause has decreasedserum levels of estradiol will be shown.The presented model predicts a decreaseof 8% in bone tissue density, which doesnot seem to be osteoporosis yet. This maybe because menopause is accompanied bymore effects than these two mentioned(as the mentioned decrease in NO) andalso most probably because they are lessphysically active (may be caused by pain).If we combine the 8% decrease caused bymenopause alone with another 9% decline(not yet published results) caused byimproper loading, we get a significant dropby almost 20% in the overall bone densityof the femur, which can be considered asosteoporotic state. One possible treatmentof bone loss connected with menopauseis treated with hormone therapy (HRT).Simulation of such a treatment that increasedestradiol serum levels to 20 pg/mlwill be shown. Again, the importance ofmechanical stimulation shown when increasedphysical activity (running 30 minutesevery other day) increases bone densityin similar fashion as HRT treatment. Andbest results are reached when both effectsare combined and even the original bonetissue density can be restored.References1. Beaupré, G. S., Orr, T. E. and Carter,D. R. (1990). An approach for time-dependentbone modeling and remodeling-application:a preliminary remodeling simulation, Journal ofOrthopaedic Research 8: 662–670.2. Carter, D. R. (1987). Mechanical loadinghistory and skeletal biology, Journal ofBiomechanics 20: 1095–1109.3. Doblaré, M. and García, J. M. (2002).Anisotropic bone remodelling model based ona continuum damage-repair theory, Journal ofBiomechanics 35(1): 1–17.4. Huiskes, R., Weinans, H., Grootenboer,H., Dalstra, M., Fudala, B. andSlooff, T. (1987). Adaptive bone-remodelingtheory applied to prosthetic-design analysis.,ambul_centrum@volny.cz221