Osteonecrosis of the femoral head remains a challenging orthopaedic problem. The disease frequently progresses to femoral head collapse, leading to debilitating osteoarthritis in the affected hip(s). Since a major goal of pre-collapse interventions is to forestall the need for hip arthroplasty, it is important that any animal models used to develop or study such interventions also have a natural history of progression to femoral head collapse. The emu (Dromaius novaehollandiae), a large flightless bird native to Australia, consistently progresses to femoral head collapse when osteonecrosis is experimentally induced cryogenically. Full biomechanical characterization of the demands this animal places on its hip is an important consideration in future usage of this model. This study reports in vitro measurement of the contact stress distributions on the emu femoral head during stance phase of the gait cycle, using Fuji pressure-sensitive film. Applied hip loadings were based upon ground reaction forces and hip flexion angles recorded in vivo. The contact stress data showed reasonable homology with the human hip, both in terms of stress magnitude and sites of habitual loading on the femoral head.
Bibliographical noteFunding Information:
We appreciate the technical assistance of Mr. Tom Baer in developing the loading fixture. Additional technical help was provided by Mr. Todd Howatt and Dr. Wanda Gordon. Financial assistance was provided by an NSF Graduate research fellowship (KLT), by a grant from the Roy J. Carver Foundation (TDB, MGC), and by NIH grants #AR46601 and #AR49919 (TDB, MGC).
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