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Estimating cancellous bone properties of the rat from mechanical testing of the femoral neck
Abstract
The rat has become a popular model for studying the aphics. effects of ovariectomy on bone properties. Testing the femoral neck has likewise become more popular in an attempt to estimate mechanical properties of cancellous bone in the rat. An inherent difficulty with this, however, is that the femoral neck consists of a cortical shell surrounding a cancellous core. A composite beam model was developed to calculate the cancellous bone modulus and stress distribution through the cross section. Also, the femoral midshaft modulus was improved by including shear, and indenting deformation, as well as bending, in the calculations. Other intrinsic properties, including energy density, were improved by assuming a binocular stress-strain curve to describe the behavior of bone in the femoral midshaft. Properties of the cancellous bone in the distal femur were also measured to compare with the results from the femoral neck composite beam model. Twenty-six, ninety-seven day old, Sprague-Dawley rats were divided evenly into two coups. One group was ovariectomized, and the other was sham operated. Thirty-five days after ovariectomy, the animals were sacrificed and the femurs removed. The femurs were tested in three-point bending. The femoral necks were tested in cantilever bending using a notched hole in a plate to support the femur. Slices of the distal femur were tested in a reduced-platen compression test to measure the mechanical properties of the cancellous core. The composite beam model calculated the cancellous modulus as lower than the cortical bone modulus when the cortical bone modulus was estimated to be between 42% and 67% of the modulus of the cortical bone in the midshaft as determined from three-point bending. The stress distribution through the cross section of the femoral neck showed a low stress level within the cancellous core, suggesting that the cancellous core carries very little of the load during the femoral neck test. The contribution of shear and indenting deformation to the modulus diminished the difference in modulus between groups. The binocular assumption illustrated that the elastic assumption underestimates the energy density calculations. The compression the intrinsic properties of cancellous bone.
Description
Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references (leaves 109-112).
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Citation
Groves, Jennifer Ann (1998). Estimating cancellous bone properties of the rat from mechanical testing of the femoral neck. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1998 -THESIS -G76.
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