Cortical Bone Fracture

Abstract

AbstractThe fracture of bone is a major health concern, particularly among the elderly. It is therefore of importance to understand the mechanics and mechanisms of how bone fails. There have been numerousin vitrostudies that have evaluated the relevant fracture properties of human cortical bone, but a complete understanding of the actual fracture mechanisms, and more specifically what processes play a role in “toughening” bone, is still lacking. This chapter seeks to provide an overview of the current state of knowledge on the fracture of cortical bone, and to address this issue, when possible, in the context of the relevant microstructural features of bone from a perspective of providing a mechanistic interpretation of how cortical bone fractures. As will be discussed, much of the early work on cortical bone fracture has used fracture mechanics to determine how factors such as age, orientation, location, species, morphology, loading mode, and crack velocity affect the measured single‐value toughness (e.g.,Kcor Gc), determined from the peak load at overload failure. More recently, it has been shown that, akin to many composites or toughened ceramics, the toughness of bone is best described in terms of rising resistance‐curve (R‐curve) behavior, where the evaluated toughness increases with crack extension. Through the use of the R‐curve, the intrinsic and extrinsic factors affecting the toughness are separately addressed from a mechanistic viewpoint, where extrinsic toughening mechanisms are those that act primarily in the wake of a crack, causing rising toughness with crack extension. Furthermore, what little is known about how R‐curve behavior and the associated mechanisms of bone toughening are affected by such factors as age, species, orientation, and location is also presented. Finally, the issue of fatigue failure in cortical bone is addressed in from a mechanistic perspective.