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Title: Towards an understanding of how hip musculature modifies fall-related stress patterns in the ageing femur : a computer simulation approach
Author: Collins, D. P.
ISNI:       0000 0004 7428 5256
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2017
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Hip fracture is one of the most severe complications of falls in older people and is considered a major public health issue. Current clinical assessment tools for hip fracture include measurements of bone mineral density (BMD) via dual energy x-ray absorptiometry (DEXA). Decreased BMD is associated with decreased bone strength and thus increased fracture risk. However, BMD is insufficient for predicting fracture risk and many individuals who suffer fracture are considered to have normal, healthy values of BMD. Subject-specific finite element (FE) models constructed from patient computed-tomography (CT) scans offer an alternative approach for assessing bone strength and fracture risk. Finite element analysis (FEA) is an increasingly mature technique that shows improved performance in the prediction of fracture risk compared to assessments of BMD. Nonetheless there are still inconsistencies between experimental results and those obtained through FEA. This thesis explores the effect of concurrent, sideways fall-related impact and hip muscle forces on femoral neck stresses in orthotropic FE models of the ageing femur. This is achieved by integrating data from the following three independent, computational methods: 1) threedimensional micro-computed tomography imaging and analysis to determine structural anisotropy of older peoples' femoral trabecular bone, 2) multibody dynamic analysis (MDA) to determine a range of potential impact and muscle forces resulting from sideways falls and 3) FEA to determine stress patterns within orthotropic FE models (constructed using data obtained using method 1) of the ageing proximal femora as a result of impact and muscle forces (derived from method 2). The results from this thesis demonstrate that 1) the architectural arrangement of trabecular bone in the head and neck regions of the ageing proximal femur is region specific but that there exists a high degree of inter-specimen similarity for each of these regions, 2) impact and, in particular, muscle forces at impact are heterogeneous in nature and finally, despite this heterogeneity, 3) impact forces from sideways falls consistently produce highest stresses in the superior femoral neck while contraction of hip muscle forces concurrent with an impact force act to increase femoral neck stress magnitudesresulting from a sideways-fall impact and create principal stress trajectories that are sub-optimally aligned with cortical and trabecular bone principal fabric directions. These findings have relevance for future work, particularly FEA, seeking to investigate the aetiology of and predict hip fracture.
Supervisor: Bates, Karl ; Crompton, Robin Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral