Change of Microscopic Elastic Properties of Vertebrae of Rats Due to Ovariectomy and Special Diet: Finite Element Analyses and Bone Growth Simulation


Materials Science Engineering (MSE2012) | event contribution
Sept. 25, 2012 - Sept. 27, 2012 | Darmstadt

For testing of new implant materials and bone substitutes in osteoporotic bone, small animal models with well defined bone status of osteoporosis are needed. In the present paper, the mechanical behaviour of vertebrae of the spine in normal and osteoporotic bone of rats is compared. Mature Sprague Dawley rats were divided randomly into groups before Sham surgery or ovariectomy (OVX). The Sham group had free access to food and water. The OVX rats were either fed a compromised diet or received s.c. glucocorticoid (dexamethason-21-isonicotinat) injection twice per week. The rats were scanned at 0 (baseline), 1 and 3 months p.o. to assess bone properties (bone mineral density and content). Computer tomograms of whole vertebrae of the rats with resolution of about 6 m voxel size were transformed into a voxel-based finite element model and uniaxial compression tests of the vertebrae similar to real tests were simulated. By comparing the simulation results with the real measurements, the microscopic Young's modulus of the bone was determined, assuming isotropic elastic properties of cortical and trabecular bone with Poisson's ratio of 0.3. Relationships between morphological and mechanical features of the vertebrae for the different rat groups are discussed. For a better understanding of osteoporotic bone development, a voxel-based mathematical model of bone growth was established, which includes a finite element calculation of the bone deformation under loading. The gained information on the changing microscopic mechanical bone properties due to osteoporosis was included in the simulation of bone remodeling. The microscopic bone stiffness affects the volumetric strain in the bone, which is thought as mechanical stimulus for bone formation. The effect of changing elastic bone properties on the osteoporotic bone development was investigated in our simulations. The computer experiments could help in tailoring of implants for osteoporotic bone.


Authors

Change of Microscopic Elastic Properties of Vertebrae of Rats Due to Ovariectomy and Special Diet: Finite Element Analyses and Bone Growth Simulation


Materials Science Engineering (MSE2012) | event contribution
Sept. 25, 2012 - Sept. 27, 2012 | Darmstadt

For testing of new implant materials and bone substitutes in osteoporotic bone, small animal models with well defined bone status of osteoporosis are needed. In the present paper, the mechanical behaviour of vertebrae of the spine in normal and osteoporotic bone of rats is compared. Mature Sprague Dawley rats were divided randomly into groups before Sham surgery or ovariectomy (OVX). The Sham group had free access to food and water. The OVX rats were either fed a compromised diet or received s.c. glucocorticoid (dexamethason-21-isonicotinat) injection twice per week. The rats were scanned at 0 (baseline), 1 and 3 months p.o. to assess bone properties (bone mineral density and content). Computer tomograms of whole vertebrae of the rats with resolution of about 6 m voxel size were transformed into a voxel-based finite element model and uniaxial compression tests of the vertebrae similar to real tests were simulated. By comparing the simulation results with the real measurements, the microscopic Young's modulus of the bone was determined, assuming isotropic elastic properties of cortical and trabecular bone with Poisson's ratio of 0.3. Relationships between morphological and mechanical features of the vertebrae for the different rat groups are discussed. For a better understanding of osteoporotic bone development, a voxel-based mathematical model of bone growth was established, which includes a finite element calculation of the bone deformation under loading. The gained information on the changing microscopic mechanical bone properties due to osteoporosis was included in the simulation of bone remodeling. The microscopic bone stiffness affects the volumetric strain in the bone, which is thought as mechanical stimulus for bone formation. The effect of changing elastic bone properties on the osteoporotic bone development was investigated in our simulations. The computer experiments could help in tailoring of implants for osteoporotic bone.


Authors