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PROCEEDINGS OF THE FIFTH INTERNATIONAL CONFERENCE ON ENGINEERING COMPUTATIONAL TECHNOLOGY
Edited by: B.H.V. Topping, G. Montero and R. Montenegro
Detecting and Tracking Effect of Mechanical Stimulation on the Osteoporotic Bone of OVX Rats Using In-Vivo Micro-CT and Micro Finite Element Analysis
C.Y. Ko1, T.W. Lee1, D.G. Woo1, B.Y. Lee2 and H.S. Kim1
1Research Institute for Medical Instrumentation and Rehabilitation Engineering, Department of Biomedical Engineering, College of Health science, Yonsei University, Korea
C.Y. Ko, T.W. Lee, D.G. Woo, B.Y. Lee, H.S. Kim, "Detecting and Tracking Effect of Mechanical Stimulation on the Osteoporotic Bone of OVX Rats Using In-Vivo Micro-CT and Micro Finite Element Analysis", in B.H.V. Topping, G. Montero, R. Montenegro, (Editors), "Proceedings of the Fifth International Conference on Engineering Computational Technology", Civil-Comp Press, Stirlingshire, UK, Paper 187, 2006. doi:10.4203/ccp.84.187
Keywords: whole body vibration (WBV), ovariectomy, morphological characteristics, structural modulus.
Osteoporosis, a disease characterized by the progressive loss of bone tissue, is one of the most common complications related with aging. A public health problem and national economy are increased by osteoporosis accompanied with several injuries like a vertebral fracture. Osteoporotic vertebral fractures are a major health care problem in the world. Some researchers investigated the beneficial effect of mechanical stimulation in ovariectomized OVX rats bone. Oxlund et al.  investigated that mechanical stimulation appeared to prevent the decrease in the strength of the bone in OVX rats. Rubin et al. [2,3,4] reported that low magnitude and high frequency in mechanical stimulation appeared to weaken decrement rate of bone mass in animal. Flieger et al.  reported that mechanical stimulation was effective to prevent bone loss in OVX rats.
In the present study, not only morphologies but also mechanical characteristics in the lumbar vertebra of rats were investigated. The effects of whole body vibration(WBV) using finite element (FE) models were studied based on micro computed tomography (Micro-CT, Skyscan-1076, Skyscan, Belgium).
For this study, 14-weeks old Sprague-Dawley rats were used. Nine rats were randomly assigned to five groups(CON : 2, SHAM : 2, WBV 17 : 1, WBV 30 : 2 and WBV 45 : 2) for study. All the rats except the SHAM group were ovariectomized to induce osteoporosis. The subject in the WBV groups were stimulated with vibration (magnitude: 1 mmpeak-peak and frequency 17Hz, 30Hz and 45 Hz, 30 minutes/day for 5 days/week) for eight weeks. The fourth lumbars of the rats were scanned by Micro-CT with 35μm resolution at week 0 (just before vibration) and again at week 8 (after vibration). Voxel models with 70×70×70μm cubic blocks for finite element analysis were generated from the acquired images. Simulated compression tests of 3D FE models, 4mm×4mm×4mm cubic specimens, were performed to investigate the mechanical characteristics in the whole vertebral bone model of the 4th lumbar vertebra. Displacement boundary conditions were applied to the specimens to simulate a compression test. Structure parameters of trabecular bone were investigated and analyzed by using in-vivo micro-CT.
The results showed that 45Hz vibration was the smallest quantity loss and the least change of structure shape in the trabecular bone. The relative values of structural modulus in groups of WBV 17Hz and 45Hz were bigger than CON. The present study investigated the effect of whole body vibration in OVX rats bone. Vibrations with magnitude 1mmpeak-peak, and frequency 17Hz, 30Hz and 45Hz respectively were stimulated to WBV groups. The group of WBV 45Hz showed that decrement rates of structure parameters in trabecular bone were the smallest. The result indicated that vibration with 45Hz, 1mmpeak-peak was possible to reduce the loss of trabecular bone mass and have a beneficial effect on the trabecular bones of OVX rats. Relative values of the structural modulus in groups of WBV 17Hz and WBV 45Hz increased. These result showed that vibration with 17Hz and 45Hz was able to prevent reducing bone strength.
In the present study, some vibrations, especially 45Hz and 1mmpeak-peak, had a beneficial effect on the quality of OVX bones as well as quantity. The use of this kind of vibration will be able to prevent bone loss in osteoporosis and weakening bones and replace medicines (such as estrogen-hormone or bishosphonates) by vibration.
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