Page 268 - Biomedical Engineering and Design Handbook Volume 1, Fundamentals

CHAPTER 10

FINITE-ELEMENT ANALYSIS

Michael D. Nowak
University of Hartford, West Hartford, Connecticut

10.1 INTRODUCTION 245 10.5 CASE STUDIES 250
10.2 GEOMETRIC CONCERNS 246 10.6 CONCLUSIONS 255
10.3 MATERIAL PROPERTIES 247 REFERENCES 256
10.4 BOUNDARY CONDITIONS 249

10.1 INTRODUCTION

In the realm of biomedical engineering, computer modeling in general and finite-element modeling
in particular are powerful means of understanding the body and the adaptations that may be made to
it. Using the appropriate inputs, a better understanding of the interrelation of the components of the
body can be achieved. In addition, the effects of surgical procedures and material replacement can
be evaluated without large numbers of physical trials. The “what if” and iterative aspects of com-
puter modeling can save a great deal of time and money, especially as compared with multiple bench
testing or series of live trials.
In attempting to understand the human body, much can be learned from material and fluids test-
ing and cadaveric examination. These processes do not, in general, determine the relative forces
and interactions between structures. They are also neither able to determine the stresses within
hard or soft tissue, nor the patterns of flow due to the interaction of red blood cells within the vascular
system.
Every aspect of the human body and devices to aid or replace function fall within the realm of
computer modeling. These models range from the more obvious arenas based on orthopedic and vas-
cular surgery to trauma from accident (Huang et al., 1999) to the workings of the middle ear (Ferris
and Prendergast, 2000).
There are an increasing number of journals that include articles using finite-element analysis
(FEA) in evaluation of the body and implants. These range from the journals dedicated to the engineering
evaluation of the body (such as The Journal of Biomechanics and The Journal of Biomechanical
Engineering) to those associated with surgical and other specialties (such as The Journal of Orthopaedic
Research, The Journal of Prosthetic Dentistry, and The Journal of Vascular Surgery).
As with any use of FEA results, the practitioner must have some understanding of the actual
structure to determine if the model is valid. One prime example of error when overlooking the
end use in the FEA realm is that of the femoral component of hip implants. If one only examines
loading patterns, the best implant would be placed on the exterior of the femoral bone, since the
bone transfers load along its outer material. Doing so in reality would lead to failure because the
nutrient supply to the bone would be compromised, and the bone would resorb (bone mass would
be lost).

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