The ability to control balance and stability are essential to prevent falls during locomotion. Maintenance of stable locomotion is challenging especially when complicated by amputation and prosthesis use. Humans employ several motor strategies to maintain stability during walking on complex terrain: decreasing walking speed, adjusting stride length and stance width, lowering the center of mass, and prolonging the double support time. The mechanisms of selecting these motor strategies by the primary motor cortex are unknown and cannot be studied directly in humans. There is also little information about dynamic stability of prosthetic gait with bone-anchored prostheses, which are thought to provide sensory feedback to the amputee through osseoperception. Therefore, the Specific Aims of my research were to (1) evaluate dynamic stability and the activity of the primary motor cortex during walking with different constraints on the base of support and (2) develop an animal model to evaluate mechanics and stability of prosthetic gait with a bone-anchored prosthesis. To address these aims, I developed a feline model that allows for investigating (1) the role of the primary motor cortex in regulation of dynamic stability of intact locomotion, (2) skin and bone integration with a percutaneous porous titanium implant facilitating prosthetic attachment, and (3) dynamic stability of walking on a bone-anchored prosthesis. The results of Specific Aim 1 demonstrated that the area and shape of the base of support influence the margins of dynamic stability during quadrupedal walking. For example, I found that the animal is dynamically unstable in the sagittal plane and frontal plane (although to a lesser degree) during a double-support by a forelimb and the contralateral hindlimb. Elevated neuronal activity from the right forelimb representation in the primary motor cortex during these phases suggests that the motor cortex may contribute to selection of paw placement location and thus to regulation of stability. The results of Specific Aim 2 on the development of skin-integrated bone-anchored prostheses demonstrated the following. Skin ingrowth into 3 types of porous titanium pylons (pore sizes 40-100 μm and 100-160 μm and nano-tubular surface treatment) implanted under skin of rats was seen 3 and 6 weeks after implantation, and skin filled at least 30% of available implant space. The duration of implantation, but not implant pore size (in the studied range) or surface treatment statistically influenced skin ingrowth; pore size and time of implantation affected the implant extrusion length (p<0.05). The implant type with the slowest extrusion rate (pore size 40-100 μm) was used in a feline model of prosthetic gait with skin-integrated bone-anchored prosthesis. The developed implantation methods, rehabilitation procedures and feline prostheses allowed 2 animals to utilize skin- and bone-integrated prostheses for dynamically stable locomotion. Prosthetic gait analysis demonstrated that the animals loaded the prosthetic limb, but increased reliance on intact limbs for weight support and propulsion. The obtained results and developed animal model improve the understanding of locomotor stability control and integration of skin with percutaneous implants.

The potential of the crural fascia to increase the articulation of the posterior thigh muscles through the in series connection of the structures, suggests that the crural fascia may influence the endpoint force direction of the muscles by partially redirecting the muscular force output. Furthermore, not only the in series connections should be considered but also how the parallel alignment of the crural fascia and the triceps surae may influence the force direction from the muscles. A redirection in force may, in turn, affect the intra-limb coordination or contribute to the selection of a task variable muscle activation pattern. The central objective was to evaluate the role of the synergistically located, posterior, distal musculature and connective tissue during locomotion. The central hypothesis was that the crural fascia would redirect the force output from the posterior thigh muscles to the endpoint and consequently increase propulsion within the limb. We selected to perform our studies in the spontaneously locomoting decerebrate cat, which allows us to investigate acute treatments applied to the hindlimb. The overall objective was accomplished by: (1) evaluating the role of the crural fascia during level walking; (2) determine the acute effect of denervating the triceps surae muscles and disrupting the crural fascia during level walking; and (3) evaluating the change in force direction output of selective stimulation of muscles in different limb configurations before and after complete fasciotomy. Our findings demonstrated that the crural fascia not only assists in propulsion but also acts to stabilize the distal limb. Furthermore, the acute denervation of the triceps surae resulted in a decrease in leg length and an increase in ankle yield during the weight acceptance phase of stance. This suggests that the conservation of the limb length as a task level variable is an adaptation rather than an immediate response.

Thesis (Ph.D.)--University of Wyoming, 2008. / Title from PDF title page (viewed on Dec. 4, 2009). Includes bibliographical references.

Whether there are sex differences in the kinematic organization of non-reproductive behaviors is rarely addressed. In this thesis, evidence is presented that male and female rats organize their posture and stepping differently during a food protection task, contact righting, skilled reaching, and vertical rearing. Neonatal gonadal steroid exposure can alter sex-typical patterns of movement organization. Whether these differences are due to sex differences in body morphology or central nervous system (CNS) was also addressed using gravid females and tfm males. The results reveal that sex differences in movement are CNS based. Furthermore, the expression and choice of sex-typical patterns of movement can be altered by CNS injury. Finally, evidence is presented that sex differences in movement organization are also present in marsupials and insects. The implications of these results for our understanding of the evolution of sex differences in CNS anatomy and behavior will be discussed. / xvi, 249 leaves : ill. ; 28 cm.

With the vast array of genetically altered (knockout) mice becoming available there is a need for quantitative, repeatable, and efficient methodologies to characterize the phenotypic consequences of knocking out specific genes. Since knockout animals often have the ability to compensate for a single missing gene, it is important to examine the structural, material and morphological properties to obtain a thorough understanding of the changes occurring. For this project, femurs of knockout mice were first scanned using microcomputed tomography (micro-CT) to obtain high-resolution images of the trabecular bone in the distal femur, as well as cortical bone in the mid-diaphysis. After scanning, the femurs were tested to destruction in four-point bending at the mid-diaphysis about the medial lateral axis of the femur. These methodologies allowed quantification of (1) morphologic properties such as bone volume fraction, trabecular properties and 2nd moment of the area (2) structural properties such as stiffness, maximum load at failure, and post yield deformation and (3) material properties such as bone mineral density, elastic modulus and yield strength. As part of two independent studies, two different knockout mice, cyclooxygenase-2 (COX-2 -/-) and Apolipoprotein E (APOE -/-), were examined for structure-function relationships using these methodologies. COX-2 knockout mice were found to have decreased mineral content in their femurs, and increased post yield deformation. APOE knockout mice at 10 weeks of age had decreased bone mass and structural properties. However, by 40 weeks of age APOE deficient mice caught up to and exceeded the structural properties and bone mass of their wild type counterparts.