Master of Science (MS), Ohio University, 2013, Mechanical Engineering (Engineering and Technology)

In this study I investigate the changes in the mechanical properties of trabecular bone due to altered loading. The bone samples come from porcine mandibular condyles of treated and untreated pigs from a previous study. The treated animals wore one of two kinds of occlusal splints which presumably altered the loading on the mandibular condyle. This study uses micro-CT images of the mandibular condyles to render a finite element mesh of the trabecular structure. Uniaxial compression was then simulated with finite element analysis to determine the apparent modulus of the bone samples. It was found that one of the splinting treatments significantly reduced the apparent modulus and bone volume fraction in the central region of the mandibular condyle. This study also used experimental uniaxial compression tests of fresh bone samples to validate the finite element model. It was found that there was 30% agreement between the finite element model and the experimental results for the apparent modulus in the anterior-posterior, and medial-lateral directions.

Committee: John Cotton (Advisor) Subjects: Biomechanics

Doctor of Philosophy, The Ohio State University, 2017, Anthropology

The objective of this research was to test the hypotheses that ontogenetic patterns of change in tibial subchondral trabecular and cortical bone microstructure are age and condyle site-specific due to differential loading associated with changing joint kinetics and body mass. High-resolution computed tomography (HR-CT) images were acquired for 31 human tibiae, ranging in age from 8 to 37.5 years. The skeletal samples are from Norris Farms #36 site, a cemetery mound in the central Illinois River valley associated with the Oneota culture, dating to A.D. 1300. This bioarchaeological sample was chosen for this study because of its cultural and biological homogeneity, high number of subadult individuals, extensive archaeological context, and excellent preservation. Proximal epiphyses were digitally isolated for analysis as regions of interest (ROIs) using Avizo Fire 6.2 and 8.1.1. 3D resolution-corrected morphometric analysis of subchondral bone architecture was performed for 11 cubic volumes of interest (VOIs) using the BoneJ plugin for ImageJ. VOIs were positioned within and between the tibial condyles within the epiphyseal region. The analysis of the subchondral cortical plate was accomplished through dual-threshold cortical masking. Ontogenetic patterns in the epiphysis of the proximal tibia were described using eight 3D morphological parameters: bone volume fraction (BV/TV), mean trabecular thickness (Tb.Th), mean trabecular spacing (Tb.Sp), structure model index (SMI), connectivity density (Conn.D), degree of anisotropy (DA), trabecular number (Tb.N), and cortical thickness (Ct.Th) in the subchondral cortical plate. Kruskal-Wallis and Wilcoxon signed rank tests were used to examine the association between region, age, and each of the eight structural parameters. For analysis, individuals were divided into four age categories: child, adolescent, young adult, and middle age. The findings of this study indicate that age-related changes in mechanical loading have (open full item for complete abstract)

Committee: Samuel Stout PhD (Advisor); James Gosman M.D, PhD (Committee Member); Mark Hubbe PhD (Committee Member); Clark Larsen PhD (Committee Member); Scott McGraw PhD (Committee Member) Subjects: Aging; Anatomy and Physiology; Archaeology; Behavioral Sciences; Biology; Biomechanics; Evolution and Development; Microbiology

Doctor of Philosophy, The Ohio State University, 2016, Anthropology

The significance of the microstructural interface between trabecular and cortical bone in the long bone metaphyses as a mechanically-adapted feature of skeletal morphology is largely unexplored, despite the role of these structures as critical for the transmission of axial loads from the trabecular network to the cortical diaphysis. These cortical-trabecular junctions (CTJs) are studied here within the context of bone ontogeny and from the perspective of mechanobiology, which seeks to interpret skeletal morphology as a product of its mechanical-functional demands. Aligned to the theoretical paradigm of bone functional adaptation, which states that bone adapts to its mechanical environment during life, this study tests several hypotheses regarding various associations between body mass and age on the one hand and various measures of CTJ structure on the other, including elements of cortical-trabecular connectivity and bone volume distribution. Anatomical site variability and mechanical adaptability in CTJ ontogeny was further addressed by examining these skeletal features in two separate skeletal elements with vastly different mechanical functions. This study was performed conducted using the Norris Farms (NF) No. 36 skeletal series, an archaeological sample of skeletons derived from a late-prehistoric group of Oneota Native Americans living in present day west-central Illinois ca. 1300 A.D. Micro-computed tomography was used to acquire high-resolution images of NF adult and sub-adult tibiae and humeri for non-invasive and non-destructive analysis of internal bone microstructure. Two computer image analysis programs (Avizo Fire 8.1.1 and ImageJ 1.49v) were used to isolate and quantify volumes of interest, and all statistical analyses were carried out in SPSS v.22. Results show a complicated picture of CTJ ontogeny in which mechanical adaptability appears to be an important driver of CTJ structural development, but not to the exclusion of other, less clear factors. (open full item for complete abstract)

Committee: Clark Larsen (Advisor); James Gosman (Committee Member); Amanda Agnew (Committee Member); Paul Sciulli (Committee Member); Sam Stout (Committee Member) Subjects: Anatomy and Physiology; Archaeology; Biomechanics; Human Remains; Physical Anthropology; Soil Sciences

Doctor of Philosophy, The Ohio State University, 2007, Anthropology

The goal of this research was to study trabecular bone microarchitecture during growth and development, producing new quantitative and structural knowledge about the development and remodeling of normal trabecular structure as demonstrated in a subadult archaeological skeletal sample from the Late Prehistoric Ohio Valley. Trabecular bone microarchitecture has a predictable relationship to functional and external loading patterns applied throughout ontogeny and maturity. Relatively little research has been directed toward the structure of and variation in trabecular bone during ontogeny, creating a deficiency in the foundation upon which trabecular bone adaptation can be used for bioarchaeological inferences. This research project tests hypotheses characterizing the temporal sequence and variation in trabecular bone volume fraction and degree of anisotropy as a reflection of growth and development, as associated with the timing and acquisition of normal functional activities (initial and maturation of bipedal gait), and as associated with changing body mass. A selected skeletal sample from the Late Prehistoric site (A.D. 1200-1300) of SunWatch Village consisted of 37 subadult and three young adult proximal tibiae. The sample as a whole, as well as four maturity stage-related groups, was analyzed. The analyses consisted of nondestructive microCT scanning of the proximal metaphyseal tibia visually demonstrating the microarchitectural trabecular structure, and quantitative 3-D structural analyses measuring bone volume fraction, degree of anisotropy, trabecular thickness, and trabecular number. Bone volume fraction and degree of anisotropy are highest at birth, decreasing to a low value at one year of age, and then gradually increasing to the adult range around six to eight years of age. Trabecular number is highest at birth and lowest at skeletal maturity; trabecular thickness is lowest at birth and highest at skeletal maturity. The results of this study provide quantit (open full item for complete abstract)

Committee: Clark Larsen (Advisor) Subjects: Anthropology, Physical

Master of Sciences (Engineering), Case Western Reserve University, 2010, EMC - Mechanical Engineering

Structurally intact trabecular bone allografts are an attractive tissue choice due to their osteoconductive structure and ability to provide some mechanical stability to the graft site. To prevent disease transmission, allograft bone is subjected to gamma sterilization. Irradiation has been shown to reduce the mechanical properties of cortical bone and change micro-damage accumulation in dense bovine trabecular bone. This study seeks to assess the effect of gamma sterilization on the yield properties of human trabecular bone across a range of bone volume fractions. Cylindrical human trabecular specimens (distal and proximal) irradiated to 29.45kGy were compared with non-irradiated controls. Specimens were compressed to past yield and analyzed using histological sections. Mechanical and histological analysis showed no differences between irradiated and control specimens. This suggests that structurally intact trabecular bone allograft, across a range of volume fractions, does not experience significant degradation in strength, stiffness or damage accumulation following gamma irradiation.

Committee: Christopher Hernandez (Advisor); Claire Rimnac (Committee Member); Joseph Mansour (Committee Member) Subjects: Engineering; Mechanics

Doctor of Philosophy, University of Akron, 2022, Integrated Bioscience

Opioids have become one of the most misused classes of prescribed medication. Synthetic opioids (e.g., fentanyl) have been responsible for most opioid overdose deaths since 2017. As this epidemic shows no signs of slowing, it is imperative to study the effects of opioids on various aspects of health including bone maintenance. Endogenous opioids (e.g., met-enkephalin) are involved in osteogenesis and bone remodeling. Exogenous opioids can interfere with bone maintenance directly through binding to osteoblasts, limiting bone formation, or indirectly through a cascade of effects limiting sex hormone production. To understand how opioids affect bone microarchitectural and biomechanical properties we first examine bone microstructure throughout the human lifespan to see natural changes occurring without the effects of opioids. Using both Synchrotron Radiation micro-Computed Tomography and confocal laser microscopy, we found bone and lacunar volume fractions to decrease with advancing age while pore diameter increased in the anterior midshaft femur. After finding how bone changes with age under normal circumstances, we sought to examine how prolonged opioid administration affected trabecular microstructure in a model organism (rabbit). We used μCT to examine the proximal tibia by anatomical quadrant (e.g., anterior, posterior). We found that morphine animals had greater bone volume fraction and less trabecular separation than controls. Fentanyl animals had significantly thicker trabeculae and increased trabecular spacing than controls. Detected differences by anatomical region followed the same overall pattern, suggesting biomechanical or anatomical variation rather than due to opioids. We finally examined overall bone strength in a non-weight bearing bone (rib) of the rabbit using uniaxial compression testing to determine how opioids affect overall mechanical competency. We found no difference in mechanical variables between opioid and control groups. Only rib span leng (open full item for complete abstract)

Committee: Brian Bagatto (Advisor); Janna Andronowski (Committee Co-Chair); Henry Astley (Committee Member); David Cooper (Committee Member); Christine Dengler-Crish (Committee Member); Nita Sahai (Committee Member) Subjects: Biology; Biomechanics; Histology; Pharmaceuticals; Physiology

Master of Science (MS), Ohio University, 2014, Mechanical Engineering (Engineering and Technology)

This study improves the agreement between two stiffness measurement techniques of trabecular bone harvested from porcine mandibular condyles. The previous method of Zaylor (2013) measured stiffness with digital finite element and experimental compression tests using 2 mm bone cubes. The current study improves the agreement between methods by examining the effect of sample size using 3 mm and 4 mm cubes, the effect of strain range used in compression tests, and investigating the geometric accuracy of the digital finite element models. It was found that larger specimens improved the stiffness agreement in mediallateral, and superior-inferior directions of the condyles, (R² > 49). The agreement was not affected by the strain limits of 0.4-0.5%, 0.5-0.6%, and 0.4-0.6%. The average digital cube lengths were 2% smaller than the physical lengths. The improved agreement justifies digital modeling of trabecular bone to measure the stiffness of mandibular condyles.

Committee: John Cotton (Advisor) Subjects: Biomedical Engineering; Mechanical Engineering

Doctor of Philosophy, Case Western Reserve University, 2011, EMC - Mechanical Engineering

It has been suggested that bone remodeling targeted to microscopic tissue damage can impair trabecular bone biomechanical properties, potentially modifying overall bone strength. In this study, we evaluate microscopic tissue damage and remodeling cavities using experimental and computational methods. Cyclic loading experiments were performed on isolated rat caudal vertebrae (n=24) to evaluate the progression of microscopic tissue damage in trabecular bone in-vitro. Vertebrae were potted in bone cement and subjected to cyclic loading between 0 – 260N. Cyclic loading was terminated at secondary and tertiary phases of the creep-fatigue curve. Trabecular microfracture was the primary form of damage in trabecular bone and the number of microfractures increased with the amount of cyclic loading. Only small amounts of microscopic tissue damage were observed in the cortical shell, demonstrating that the damage occurs in trabecular bone prior to complete fracture of vertebrae. Modifications to the rat tail loading model developed by Chambers and colleagues were considered to evaluate the feasibility of using the model to generate microscopic tissue damage in trabecular bone without fracturing the vertebrae in-vivo. Protocols were developed to apply cyclic loading to caudal 8th vertebrae (C8) in-vivo (n=20) or in-situ (n=15). Two pin types: smooth and threaded, two pin sizes: 1.6mm and 2.0mm dia. and four time points after the surgery: 0, 1, 2 and 4 weeks were considered. Our results indicated that the rat tail loading model may not be used for generating microscopic tissue damage in trabecular bone in-vivo. Finite elements models of idealized trabeculae were generated to determine a potential range for stress concentrations factors of remodeling cavities. Two types of trabecula: rod-like and plate-like and two types of loading conditions: pure tension and pure bending were considered. Finite element models of two rod-like and three plate-like rat trabeculae were generated (open full item for complete abstract)

Committee: Christopher Hernandez (Committee Chair); Clare Rimnac (Committee Member); Joseph Mansour (Committee Member); Eben Alsberg (Committee Member) Subjects: Biomechanics; Biomedical Engineering; Mechanical Engineering