Background: Osteoarthritis (OA) is a debilitating joint disease marked by cartilage and bone changes. Morphological and mechanical changes to bone, which are thought to increase overall bone stiffness, result in distorted joint mechanics and accelerated cartilage degeneration. Using a parametric finite element (FE) model of the proximal tibia, the primary objective of this study was to determine the relative and combined effects of OA-related osteophyte formation, and morphological and mechanical alterations to subchondral and epiphyseal bone on overall bone stiffness. The secondary objective was to assess how simulated bone changes affect load transmission in the OA joint. Methods: The overall geometry of the model was based on a segmented CT image of a cadaveric proximal tibia used to develop a 2D, symmetric, plane-strain, FE model. Simulated bone changes included osteophyte formation and varied thickness and stiffness (elastic modulus) in subchondral and epiphyseal bone layers. Normal and OA related values for these bone properties were based on the literature. “Effective Stiffness (K)” was defined as the overall stiffness of the proximal tibia, calculated using nodal displacement of the loaded area on the subchondral cortical bone surface and the load magnitude. Findings: Osteophyte formation and thickness or stiffness of the subchondral bone had little effect on overall bone stiffness. Epiphyseal bone stiffness had the most marked effect on overall bone stiffness. Load transmission did not differ between OA and normal bone. Interpretation: Results suggest that epiphyseal (trabecular) bone is a key site of interest in future analyses of OA and normal bone. Results also suggest that observed OA-related alterations in epiphyseal bone may result in OA bone being more flexible than normal bone.

Disuse of weight bearing bones has been shown to cause bone loss. This poses a health concern for people exposed to microgravity, such as astronauts. Animal studies are used to study factors related to bone loss and countermeasures to prevent bone loss. This study used a hindlimb unloaded (HU) rat model to simulate microgravity and a muscle stimulation countermeasure to simulate resistive exercise. Uniaxial strain gages were implanted on the antero-medial aspect of the proximal tibia to measure the mechanical strain during a typical exercise session. In a separate but parallel study, the exercise was shown to be an effective countermeasure to disuse related bone loss. The current study sought to understand the loading of the bone during the exercise. To determine if the strain response changes during a protocol using this countermeasure, strains were measured on a group of weight bearing animals and a group that were hind limb unloaded and received the countermeasure for 21 days. Strain magnitudes and rates were considered and related to torques at the ankle joint. No significant differences in strain magnitudes were noted between the baseline control group and the hindlimb unloaded group that received the countermeasure. The two kinds of contractions used in an exercise session are isometric and eccentric. The isometric contractions are used to adjust the stimulation equipment for the eccentric contractions, which constitute the exercise. Peak strain levels during the isometric contractions ranged from 900 to 2200 microstrain while the eccentric were 38% lower and ranged from 600 to 1400. Eccentric strain rates were 62% lower than the isometric contractions strain rates. These results indicate that the strain environment during the isometric contractions may be causing more of the osteogenic response than the eccentric contractions, which have previously been thought to be the primary part of the countermeasure.

In this study, trabecular architecture is considered as a cellular solid structure, including both intact and damaged bone models. ??Intact?? bone models were constructed based on ideal versions of 25, 60 and 80-year-old specimens with varying trabecular lengths and orientations to 5%, and 10% covariance of variation (COV). The models were also flipped between longer transverse and longer longitudinal trabeculae. With increasing COV of lengths and orientations of trabecular bone, the apparent modulus is linearly decreased, especially in the longer transverse trabeculae lengths. ??Damaged?? bone models were built from the 25 year old model at 5% COV of longer transverse trabeculae, and with removing trabeculae of 5% and 10% of trabecular volume in transverse and longitudinal directions, respectively, as well as in combination to total 10% and 15%. With increasing percent of trabeculae missing, the apparent modulus decreased, especially dramatically when removal was only in the transverse direction. The trabecular bone models were also connected to a cortical shell and it was found that the apparent modulus of an entire slice was increased in comparison to the modulus of trabecular bone alone. We concluded that the architecture of trabecular bone, especially both lengths and percent of trabecular missing in the longitudinal direction, significantly influences mechanical properties.

Disuse of weight bearing bones has been shown to cause bone loss. This poses a health concern for people exposed to microgravity, such as astronauts. Animal studies are used to study factors related to bone loss and countermeasures to prevent bone loss. This study used a hindlimb unloaded (HU) rat model to simulate microgravity and a muscle stimulation countermeasure to simulate resistive exercise. Uniaxial strain gages were implanted on the antero-medial aspect of the proximal tibia to measure the mechanical strain during a typical exercise session. In a separate but parallel study, the exercise was shown to be an effective countermeasure to disuse related bone loss. The current study sought to understand the loading of the bone during the exercise. To determine if the strain response changes during a protocol using this countermeasure, strains were measured on a group of weight bearing animals and a group that were hind limb unloaded and received the countermeasure for 21 days. Strain magnitudes and rates were considered and related to torques at the ankle joint. No significant differences in strain magnitudes were noted between the baseline control group and the hindlimb unloaded group that received the countermeasure. The two kinds of contractions used in an exercise session are isometric and eccentric. The isometric contractions are used to adjust the stimulation equipment for the eccentric contractions, which constitute the exercise. Peak strain levels during the isometric contractions ranged from 900 to 2200 microstrain while the eccentric were 38% lower and ranged from 600 to 1400. Eccentric strain rates were 62% lower than the isometric contractions strain rates. These results indicate that the strain environment during the isometric contractions may be causing more of the osteogenic response than the eccentric contractions, which have previously been thought to be the primary part of the countermeasure.

La Osteosíntesis biológica no es un implante, sino un concepto que puede efectuarse con los elementos habituales de osteosíntesis. Pretende dar la estabilidad suficiente con reducción indirecta, sin pretender reducciones anatómicas de fragmentos que pueden dañar la vascularización de ellos y sin tocar el foco de fractura. Se realizó un estudio descriptivo-retrospectivo en el cual se evaluaron los resultados de 15 pacientes con fracturas diafisiarias de fémur (05) y tibia (10) tratados mediante la técnica de Osteosíntesis con plaqueado minimamente invasivo; los cuales fueron tratados durante el periodo Enero 2001 y Diciembre 2002. La edad media fue de 50.2 y 32.5 años respectivamente. Todas las fracturas femorales fueron cerradas, 08 fracturas fueron cerradas y 02 expuestas de I (según Gustillo) entre las fracturas tibiales. De acuerdo a la clasificación AO hubieron, 2 del tipo B2, 1 del tipo C1 y 2 del tipo C2 entre las fracturas de fémur y 3 del tipo B1, 3 del tipo B2, 2 del tipo C2, y 2 del tipo C3 entre las tibiales. El promedio de tiempo de apoyo total para las fracturas de fémur fue de 16.6 semanas y 14 semanas para las de tibia; mientras el promedio de tiempo de unión por radiografía fue de 18.8 semanas y 15.6 semanas respectivamente. Se presentó un caso de infección superficial, un caso de perdida de fijación de fractura y no se presentaron casos de fallas de material de osteosíntesis. Una fractura consolidó con un alineamiento en varo de 10° y recurvatum de 15° y una fractura con recurvatum de 15°, estas pertenecientes al grupo de las fracturas tibiales. Los resultados del tratamiento para fracturas diafisiarias de fémur y tibia obtenidos con ésta técnica compara favorablemente con otras series usando técnicas diferentes sin la morbilidad asociada de grandes abordajes y autoinjerto óseo. Sin embargo la técnica quirúrgica demanda un cuidado especial para restaurar el alineamiento axial.

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Thesis (MAppSc in Physiotherapy) -- University of South Australia, 1993

Thesis (M.S.)--Ohio University, March, 1995. / Title from PDF t.p.

Thesis (M.Sc. (Anatomy))--Mahidol University, 1984.

Thesis (M.S.)--University of Alabama at Birmingham, 2007. / Title from PDF title page (viewed Sept. 23, 2009). Includes bibliographical references (p. 66-77).