Femur Model for Predicting Strength and Fracture Risk - Computational Biomechanics of the Musculoskeletal System - page 105

9 Femur Model for Predicting

Strength and Fracture Risk

He Gong, Yubo Fan, and Ming Zhang

ContentS
Summary ........................................................................................................................................ 105
9.1 Introduction .......................................................................................................................... 105
9.1.1 Linear versus Nonlinear Finite Element Analysis .................................................... 106
9.1.2 Isotropic versus Anisotropic Bone Material Model .................................................. 106
9.1.3 Bone Tissue Heterogeneity ....................................................................................... 106
9.1.4 Effects of the Loading Condition .............................................................................. 106
9.2 Development of Femur Models to Predict Strength and Fracture Risk ............................... 107
9.2.1 Quantitative CT Scanning Procedure........................................................................ 107
9.2.2 Three-Dimensional Modeling of the Proximal Femur ............................................. 107
9.2.3 Bone Tissue Heterogeneity ....................................................................................... 107
9.2.4 Nonlinear Finite Element Analysis for the Estimation of Femoral Strength ............ 108
9.3 Results from the Model Analysis .......................................................................................... 108
9.4 Applications of the Model ..................................................................................................... 110
Acknowledgments .......................................................................................................................... 111
References ...................................................................................................................................... 112

Summary
Hip fractures often occur as a result of bone fragility due to osteoporosis, particularly in the elderly,
and have been recognized as a major public health problem given the ever-increasing number of
elderly people. In clinics, osteoporosis is often defined in terms of bone mineral density. However,
density alone cannot accurately determine bone strength in practice. Many hip fractures occur in
people whose hip bone mineral density (BMD) is not severely reduced. Other factors, such as bone
geometry, bone internal architecture, and tissue properties, may affect bone strength. Accurate
evaluation of hip fracture risk in patients can identify those at high risk so that preventive measures
can be taken. It is very important to develop better measures to assess femoral strength and fracture
risk using clinically available information. Subject-specific finite element (FE) analysis is a very
powerful tool to obtain more sophisticated evaluations of bone strength and the related fracture risk.
In this chapter, subject-specific, image-based, nonlinear FE modeling of the proximal femur will be
introduced to predict proximal femoral strength and locations of failure.

9.1 IntroduCtIon
Whole bone strength is mainly determined by architecture, geometry, and material properties.
Architecture and geometry include the gross morphology (size and shape) and the arrangement of
the internal trabecular architecture. Bone material properties depend on the degree of mineraliza-
tion, collagen characteristics, and micro-damage (Seeman and Delmas, 2006). For a more accurate
and reliable diagnosis, it is necessary to know the mechanical parameters of bone, especially stiff-
ness and strength, because these parameters reflect bone fracture risk.

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