0758 - Fatigue Fracture of the Proximal Femur

INTRODUCTION In the United States, there are over 300,000 hip fractures annually, resulting in over $13 billion in medical costs (1). About 90% of these have been reported to be the consequence of falls (1). The remaining 10% are thought to be the result of fatigue of the bone tissue (spontaneous fracture). Repeated falls may increase fracture risk by affecting the integrity of the bone tissue; microscopic cracks may propagate to full-scale fractures during cyclic loading. Microstructure, bone geometry, and bone material properties are important mechanical concerns that influence the incidence of hip fracture. Specifically, bone mineral density (BMD) has been directly related to bone strength, and is measurable by dual-energy x-ray absorptiometry (DXA). Monotonic strength of the proximal femur has been attributed to the distribution of trabecular and cortical bone as relfected in a global measurement of BMD (R=0.78-.92) (3,5). Previous studies have not predicted a relationship between BMD and fatigue fracture of whole bone specimens. We chose to compare cyclic loading to DXA measurements of the proximal femur. In addition, monotonic fracture data of contra-lateral hip specimens was available.