Page 244 - Biomedical Engineering and Design Handbook Volume 1, Fundamentals

CHAPTER 9

BONE MECHANICS

Tony M. Keaveny
University of California, San Francisco, California and
University of California, Berkeley, California
Elise F. Morgan
University of California, Berkeley

Oscar C.Yeh
University of California, Berkeley

9.1 INTRODUCTION 221 9.5 MECHANICAL PROPERTIES OF
9.2 COMPOSITION OF TRABECULAR BONE 231
BONE 222 9.6 MECHANICAL PROPERTIES OF
9.3 BONE AS A HIERARCHICAL TRABECULAR TISSUE MATERIAL 236
COMPOSITE MATERIAL 222 9.7 CONCLUDING REMARKS 237
9.4 MECHANICAL PROPERTIES OF ACKNOWLEDGMENTS 237
CORTICAL BONE 226 REFERENCES 237

9.1 INTRODUCTION

Bone is a complex tissue that is continually being torn down and replaced by biological remodeling.
As the main constituent in whole bones (which as organs contain other tissues such as bone
marrow, nerves, and blood vessels), the two types of bone tissue—cortical and trabecular bone—
have the functional task of withstanding substantial stress during the course of locomotion and
strenuous activities such as lifting heavy weights or fast running. Since bones are loaded both
cyclically and statically, fatigue and creep responses are important aspects of their mechanical
behavior. Indeed, there is evidence that a primary stimulus for bone remodeling is the repair of
damage that accumulates from habitual cyclic loading. 1,2 With aging, however, the balance
between bone loss and gain is disrupted, and bone deteriorates, leading to a variety of devastating
clinical problems. In modern populations, fractures from osteoporosis are becoming increasingly
common, the spine, hip, and wrist being the primary sites. Implantation of orthopedic prostheses
for conditions such as disc degeneration and osteoarthritis require strong bone for optimal fixa-
tion, a difficult requirement for sites such as the aged spine or hip, where bone strength can be
greatly compromised. The goal of this chapter is to summarize the highlights of what is known
about the mechanical behavior of bone as a material. With a focus on the behavior of human bone,

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