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Date of Award

2003

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Medical Sciences

Supervisor

Dr. Colin E. Webber

Abstract

This work encompasses two primary studies utilizing peripheral quantitative computed tomography (PQCT) in the assessment of bone characteristics at the distal radius. PQCT enables separate analyses of cortical, trabecular and total bone density, content and geometry. Further analysis of the pQCT image with specialized software permits in vivo trabecular structure assessment. The first study is a two-year prospective trial evaluating the effects of five different medication regimens (hormone replacement therapy (HRT), etidronate , alendronate, etidronate plus HRT and alendronate plus HRT) used for the treatment of osteoporosis in 123 postmenopausal women with low bone mass. Results of analyses on baseline data found that trabecular structure indices could significantly discriminate between osteoporotic and osteopenic groups of women. Longitudinal data at the lumbar spine (LS) and femoral neck (FN) for women taking any medication ('Any-Tx') showed similar results to those of large clinical trials. For example, the 'Any-Tx' group gained significant bone mineral density (BMD) over baseline at 2 years at the LS (5.5%, p<0.001) and FN (1.6%, p<0.05). Women on combination therapy gained significantly more BMD than women taking one medication over 2 years at the LS and FN. Data suggests that alendronate plus HRT may produce the largest BMD gains at the LS and FN at 2 years. Longitudinal pQCT data for total, cortical and trabecular compartments at the distal radius in the control group over the 2 years suggest endocortical resorption and trabecular thinning with age. PQCT data in the 'Any-Tx' group show gains in total and cortical bone density and cortical content, but losses in trabecular density, content and area. This suggests that anti-resorptive medications promote endocoritcal apposition and reduce intracortical porosity. The second study evaluated five different clinical measurement tools in the prediction of in vitro failure load at the distal radius and found that cortical content measured by pQCT was a significantly better predictor than ultrasound or digital x-ray radiogrammetry.

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