Osteonecrosis, an important unsolved problem in orthopaedics, results from insufficient blood perfusion to the weight-bearing cancellous bone in the femoral head. Over 1--5 years, affected bone becomes progressively weaker, frequently leading to articular surface collapse and osteoarthritis. Delaying or preventing femoral head collapse is the goal of most early interventions.; Many animal models have been used to evaluate various treatments, but since most "traditional" animals (e.g. dogs, mice, rats) do not naturally progress to femoral head collapse when osteonecrosis is induced, the overall effectiveness of the treatment cannot be determined. The emu, a large bipedal bird, has been shown to consistently progress to femoral head collapse when osteonecrosis is induced. This dissertation work expands the general knowledge base about emu hip biomechanics, with the goal of using this animal to investigate surgical interventions to treat osteonecrosis.; Three studies were conducted to reproducibly create and quantify necrotic lesions in the emu femoral head. First, a cryo-insult probe capable of producing necrotic lesions in the emu femoral head was developed. Second, a thermal finite element model of the probe was developed to investigate the effect various parameters had on the frozen region. Third, an image-analysis algorithm was developed to quantify necrotic regions of bone from histological sections.; Four additional studies were conducted to compare the biomechanics of emu and human hips. First, the activity of emus was quantified. Second, a mechanical testing apparatus was built to simulate muscle groups used by the emu during ambulation. Fuji pressure-sensitive film was used to determine the contact stress distributions across the femoral head during gait. Third, four-point bending tests were performed to determine the material properties of emu cortical bone. Fourth, contact stress data were used as boundary conditions for a 3D structural finite element model of an emu proximal femur. Simulated lesions were modeled to explore the effect of lesion size and placement on the femoral head's propensity to collapse.; The combination of these studies has advanced the knowledge base in this field. As a result, the emu is significantly closer to being a useful model to evaluate the effectiveness of femoral head-preserving interventions.
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