Date of Award

12-2012

Degree Name

MS in Biomedical Engineering

Department

Biomedical and General Engineering

Advisor

Scott Hazelwood

Abstract

Osteoporosis affects the human skeleton through the direct effects of the disease on the function and structure of bone. Individuals who are affected by osteoporosis may be subject to serious fractures and it is estimated that annually approximately 1.5 million fractures can be attributed to this disease [1]. The disease is categorized as the direct side effect of increased bone porosity and bone loss and is directly linked to estrogen deprivation [2]. Animal models are often used to make initial conclusions about the effects of the disease or pharmacological treatments. In this study, sheep were chosen as a representative animal model due to their similar metabolic characteristics to that of a human. Like most animals, the ovine does not undergo a natural menopause and an ovariectomy was necessary to replicate the condition. The study objective was to quantify compact bone density present in ovine at three months post ovariectomy.

The study included 112 ovine separated into different treatment groups. The treatment groups were separated into 4 groups of 28 based on season of surgery: autumn, winter, spring, and summer. Each seasonal group was further divided into 2 groups of 14; the first group underwent an ovariectomy; and the second group underwent a sham surgery, in which the ovaries were visualized and handled but left in the abdomen. One group was sacrificed 3 months post operatively and the other group was sacrificed at 12 months post operatively. This study specifically looks at ewe sacrificed at 3 months. The radius from each sheep was cut into the anatomical sectors: cranial, caudal, craniolateral, craniomedial, caudomedial, and caudolateral. Each anatomical sector was turned into a microradiograph for analysis. Densitometry was performed to determine the density of each specimen using the estimated thickness of aluminum (ETA) as the key. Statistical analysis assessed the resulting data to understand the effects of treatment, season of sacrifice, season of surgery, and anatomical sector by comparing both mean ETA and standard deviation ETA to understand changes in bone density.

The results revealed significant differences between the ovariectomy and sham groups as well as variation within season of surgery and season of sacrifice in both groups. Anatomical sector showed no significant variation. The differences in the thickness of aluminum seen in the sheep that underwent a sham operation can be attributed to the presence of estrogen. The sheep that underwent an ovariectomy showed differences in the estimated thickness of aluminum that can be attributed to other seasonal characteristics including the influence of Vitamin D. The results and conclusions within this study can be used to influence bone material characteristics and bone loss test protocols in future osteoporosis and estrogen depletion studies.

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