Currently Dual energy X-ray Absorptiometry (DXA) and Quantitative Ultrasound (QUS) are used readily in the clinical environment for the assessment of bone quality. However, neither measure is a direct mechanical measure of bone. A Mechanical Resonance Tissue Analyzer (MRTA) has been developed that looks at the ulna’s deformation curve to vibration to achieve the measure of EI, cross sectional bending stiffness. This study investigated the relationships between MRTA to that of QUS and DXA. Regression analysis found significant linear correlations between EI to BMD and BMC, however, no significant relationships were found between EI and the variables of QUS. However, this technology is seen to have a potential for the assessment of in vivo bone quality. Furthermore, an improved configuration of the MRTA device is described, in addition to how preliminary results correspond to theoretical results.

Currently Dual energy X-ray Absorptiometry (DXA) and Quantitative Ultrasound (QUS) are used readily in the clinical environment for the assessment of bone quality. However, neither measure is a direct mechanical measure of bone. A Mechanical Resonance Tissue Analyzer (MRTA) has been developed that looks at the ulna’s deformation curve to vibration to achieve the measure of EI, cross sectional bending stiffness. This study investigated the relationships between MRTA to that of QUS and DXA. Regression analysis found significant linear correlations between EI to BMD and BMC, however, no significant relationships were found between EI and the variables of QUS. However, this technology is seen to have a potential for the assessment of in vivo bone quality. Furthermore, an improved configuration of the MRTA device is described, in addition to how preliminary results correspond to theoretical results.

Osteoporosis is a debilitating and costly disease of the skeleton characterized by low bone mass and structural deterioration of bone tissue leading to bone fragility and an increased susceptibility to fractures of the hip, spine, and wrist. Current data suggest that at present time, 7.8 and 21.8 million women have osteoporosis and osteopenia respectively. The development of osteoporosis and related fracture in later life depends not only on the rate of bone loss in adulthood, but also on the amount of bone present at skeletal maturity. Oral contraceptives (OC), because of their capacity to diminish concentrations of free testosterone and estrogen, have been purported to affect bone mass in young adult women, but results have proven inconsistent. Further, positive skeletal effects of exercise training are thought to be compromised by use of OCs in skeletally immature females. PURPOSE: To assess the independent and synergistic effects of OC use on bone mineral density (BMD) and long bone mechanical bending stiffness (EI) in college-aged females after unilateral isokinetic resistance training. METHODS: Forty six females (age 20 +/- 1.4 yr, height 163.8 +/- 6.2cm, weight 58.9 +/- 8.6kg, fat 27.9 +/- 4.8%) were categorized as OC users (OC, N=22) or non-users (NOC, N=24). Subjects participated in 32 weeks (3 d/wk) of unilateral arm and leg training at an angular velocity of 60 degrees/s using isokinetic dynamometers. BMD and EIMRTA were assessed using dual-energy x-ray absorptiometry (DXA) and mechanical response tissue analysis (MRTA), respectively. RESULTS: Total leg and arm muscular strength of the trained limb increased by 16% and 15%, respectively (p < 0.001), beyond changes observed in the control limbs. Total body BMD increased from baseline for NOC subjects (p < 0.05), but not for OC users. This difference failed to show significance (p = 0.069) when comparisons were run between NOC and OC groups. Increases in ulnar BMD (p < 0.01 for all limbs) and BMD of the trained total hip (OC, p < 0.001; NOC, p < 0.05) occurred irrespective of contraceptive status. Positive changes in EI were conflicting, occurring in the trained ulna for the NOC group (p < 0.05), and trained tibia for OC users (p < 0.05). Tibial BMD increased only for the untrained leg in NOC subjects (p < 0.01). No between group differences were found to be significant, nor were differences between trained vs. untrained, and weight bearing (tibia) vs. non-weight-bearing (ulna) limbs found to be significant. CONCLUSION: These results suggest that oral contraceptives may limit attainment of total body peak bone mass in young adult females. Skeletal maturation in the ulna appeared to be unaffected by exercise training and OC use. Positive effects of exercise training on the total hip were seen in both groups, irrespective of OC status. Conversely, exercise training and use of OCs use may limit the attainment of bone mass in the tibia. Further studies are needed to determine the interactive effects of OC use and isokinetic resistance training on measures of total body and site-specific bone status. / Master of Science

The mechanical response tissue analyzer (MRTA) tests long bone quality through low frequency, low amplitude vibration in vivo. The MRTA measures complex stiffness over a range of low frequencies, offering a wealth of information on bone composition. Previous MRTA interpretation used lumped parameter algorithms focused on reliably estimating the bone's bending stiffness (EI). To interpret the stiffness response, the first finite element (FE) simulation of the MRTA test of a human tibia was developed to identify dominant parameters that will possibly make linear prediction algorithms more suitable for estimating bone quality. Five FE models were developed in stages by adding complexity. Starting with a solid mesh of the diaphysis, each model was created from its predecessor by sequentially adding: a medullary canal, linear elastic (LE) cancellous epiphyses, linear viscoelastic (LVE) cancellous and cortical bone, and a LVE skin layer. The models were simulated in vibration using a direct steady-state dynamics procedure in ABAQUS to calculate the complex stiffness response. Natural frequency analysis (ABAQUS) verified that the FE models accurately reproduced previous experimental and computational resonances for human tibiae. A solid, LE cortex roughly matched the dominant frequency from experimental MRTA raw data. Adding the medullary canal and LVE properties to bone did not greatly spread the peak or shift the resonant frequency. Adding the skin layer broadened the peak response to better match the MRTA experimental response. These results demonstrate a simulation of the MRTA response based upon published geometries and material data that captures the essence of the instrument. / Master of Science

In Latin America, a social revolution is statistically far more likely to fail than to succeed. Yet there is little understanding as to the contributory factors of revolutionary failure or success. Many researchers look for commonalities by examining multiple revolutions across the region or even around the globe and throughout large periods of time, but their analysis frequently lacks commonality in the underlying conditions of the insurgencies. The case of Peru, however, provides a unique opportunity to examine multiple revolutions in the fairly homogenous environment of one state during a short and constrained timeframe of thirty years. In the history of the Republic of Peru, there have been only four social revolutions. These insurgencies were contained within two discreet periods of time: the MIR and ELN in the 1960’s, and Shining Path and MRTA in the 1980’s to 1990’s. While each of these revolutions experienced varying levels of success, each ultimately failed due, in no small part, to a particular set of structural and socioeconomic variables. / text

The ability of current clinical tools to predict bone fractures is poor, likely because these tools focus on bone mass and mineral content and neglect bone quality and the collagen phase. The Mechanical Response Tissue Analyzer (MRTA) is an instrument that provides a non-invasive mechanical measurement of the whole bone. It has traditionally been used to obtain a bone stiffness constant (Kb), but can provide a bone damping constant (Bb) that has not previously been considered. The goal of this research is to determine whether the MRTA can detect three damage modes that do not alter bone mass or mineral density: γ-irradiation, collagen over-crosslinking, and fatigue. The MRTA detected a reduction in Bb due to over-crosslinking. Fatigue was found to increase Bb and decrease Kb, and these changes were confirmed through dynamic bending tests. The MRTA shows potential to diagnose increased fracture risk in scenarios where damage is currently undetectable.

The ability of current clinical tools to predict bone fractures is poor, likely because these tools focus on bone mass and mineral content and neglect bone quality and the collagen phase. The Mechanical Response Tissue Analyzer (MRTA) is an instrument that provides a non-invasive mechanical measurement of the whole bone. It has traditionally been used to obtain a bone stiffness constant (Kb), but can provide a bone damping constant (Bb) that has not previously been considered. The goal of this research is to determine whether the MRTA can detect three damage modes that do not alter bone mass or mineral density: γ-irradiation, collagen over-crosslinking, and fatigue. The MRTA detected a reduction in Bb due to over-crosslinking. Fatigue was found to increase Bb and decrease Kb, and these changes were confirmed through dynamic bending tests. The MRTA shows potential to diagnose increased fracture risk in scenarios where damage is currently undetectable.

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