Browsing by Author "Clement, John"

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    Age-related changes in femoral head trabecular microarchitecture
    (Buck Institute for Age Research, 2017-10-11) Greenwood, Charlene; Clement, John; Dicken, Anthony; Evans, Paul; Lyburn, Iain Douglas; Martin, Richard M.; Stone, Nick; Zioupos, Peter; Rogers, Keith
    Osteoporosis is a prevalent bone condition, characterised by low bone mineral density and increased fracture risk. Currently, the gold standard for identifying osteoporosis and increased fracture risk is through quantification of bone mineral density using dual energy X-ray absorption. However, many studies have shown that bone strength, and consequently the probability of fracture, is a combination of both bone mass and bone ‘quality’ (architecture and material chemistry). Although the microarchitecture of both non-fracture and osteoporotic bone has been previously investigated, many of the osteoporotic studies are constrained by factors such as limited sample number, use of ovariectomised animal models, and lack of male and female discrimination. This study reports significant differences in bone quality with respect to the microarchitecture between fractured and non-fractured human femur specimens. Micro-computed tomography was utilised to investigate the microarchitecture of femoral head trabecular bone from a relatively large cohort of non-fracture and fracture human donors. Various microarchitectural parameters have been determined for both groups, providing an understanding of the differences between fracture and non -fracture material. The microarchitecture of non-fracture and fracture bone tissue is shown to be significantly different for many parameters. Differences between sexes also exist, suggesting differences in remodelling between males and females in the fracture group. The results from this study will, in the future, be applied to develop a fracture model which encompasses bone density, architecture and material chemical properties for both female and male tissues.
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    Contrasting the crystallinity indicators of heated and diagenetically altered bone mineral
    (Elsevier, 2010-10-01) Rogers, Keith; Beckett, Sophie; Kuhn, Samira; Chamberlain, Andrew; Clement, John
    Modifications to bone mineral as a result of diagenesis or heating include a marked increase in crystallinity. Although these processes are not completely understood a number of simple, pragmatic approaches are in general use to quantify crystallinity and thus provide a relative metric for features such as preservation state. A preliminary investigation into the interpretation of crystallinity as measured by X-ray diffraction has been undertaken. The microstructural changes associated with diagenetically altered (archaeological) and heated contemporary bone have been examined. A common analysis approach was adopted and thus direct comparison between the physical features of these material systems has been possible. The data clearly demonstrate the pronounced anisotropic nature of the crystallite microstructure for both diagenetically altered and contemporary bone. The limitations of adopting simple crystallinity indices for characterising such materials are explored. Crystallite size and strain were shown to be dependent upon crystallographic direction. Overall, the diagenetically altered bone mineral possessed greater long range lattice order than that of contemporary heated bone. Further, significant differences between the directional nature of the microstructure of diagenetically altered and modern heated bone were observed. This study has enabled a direct comparison of the effects of heating and diagenesis upon bone mineral. It has demonstrated the need to consider bone microstructure anisotropically.
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    The use of μCT and fractal dimension for fracture prediction in osteoporotic individuals
    (Elsevier, 2019-12-11) Arnold, Emily; Clement, John; Rogers, Keith D.; García-Castro, Fabio; Greenwood, Charlene
    Osteoporosis (OP) is a widespread condition with commonly associated fracture sites at the hip, vertebra and wrist. This study examines the effects of age and osteoporosis on bone quality by comparing the efficacy of using parameters which indicate bone quality (both traditional clinical parameters such as bone mineral density (BMD), as well as apparent Young's modulus determined by finite element analysis, among others) to predict fracture. Non-fracture samples were collected from the femoral heads of 83 donors (44 males, 39 females), and fracture samples were obtained from the femoral heads of 17 donors (female). Microarchitectural parameters (Bone Volume/Total Volume [BV/TV], Bone Surface/Bone Volume [BS/BV], Tissue Mineral Density [TMD, etc.]) were measured from μCT of each sample as well as 2D and 3D fractal dimension (D2D and D3D respectively). A cube was cropped from μCT images and an isotropic hexahedral element was assigned to each voxel. Finite element analysis was used to calculate the Young's modulus for each sample. Overall, values for microarchitectural characteristics, fractal dimension measurements and Young's Modulus were consistent with values within literature. Significant correlations are observed between age and BV/TV for non-fracture males and females, as well as between age and volumetric BMD (vBMD) for the same groups. Significant differences are present between age-matched non-fracture and fracture females for BV/TV, BS/BV, vBMD, TMD, D2D, D3D, (p < 0.01 for all). Properties which are not age dependent are significantly different between age-matched non-fracture and fracture specimens, indicating OP is a disease, and not just an accelerated aging process.