Change of mechanical vertebrae properties due to progressive osteoporosis: combined biomechanical and finite-element analysis within a rat model
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For assessing mechanical properties of osteoporotic bone, biomechanical testing combined with in silico modeling plays a key role. The present study focuses on microscopic mechanical bone properties in a rat model of postmenopausal osteoporosis. Female Sprague–Dawley rats were (1) euthanized without prior interventions, (2) sham-operated, and (3) subjected to ovariectomy combined with a multi-deficiencies diet. Rat vertebrae (corpora vertebrae) were imaged by micro-CT, their stiffness was determined by compression tests, and load-induced stress states as well as property changes due to the treatment were analyzed by finite-element modeling. By comparing vertebra stiffness measurements with finite-element calculations of stiffness, an overall microscopic Young’s modulus of the bone was determined. Macroscopic vertebra stiffness as well as the microscopic modulus diminish with progression of osteoporosis by about 70 %. After strong initial changes of bone morphology, further decrease in macroscopic stiffness is largely due to decreasing microscopic Young’s modulus. The micromechanical stress calculations reveal particularly loaded vertebra regions prone to failure. Osteoporosis-induced changes of the microscopic Young’s modulus alter the fracture behavior of bone, may influence bone remodeling, and should be considered in the design of implant materials.
KeywordsOsteoporosis Biomechanics Young’s modulus Bone histology Rat model
Our appreciation is to Gunhild Martels (Justus-Liebig-University, Gießen) for excellent technical support and to Anita Ignatius and Lutz Dürselen (University of Ulm, Medical Faculty) for making the compression tests possible. We thank Michael Kücken for critically reading the manuscript. This work was supported by the Deutsche Forschungsgemeinschaft (DFG) through SFB/TR 79. We gratefully acknowledge support from the German Excellence Initiative via the Cluster of Excellence EXC 1056 “Center for Advancing Electronics Dresden” (cfAED). The authors thank the Center for Information Services and High Performance Computing (ZIH) at the Dresden University of Technology for computational resources and the Cluster of excellence “Center for Regenerative Therapies Dresden” (CRTD) for additional help.
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