Preface

The purpose of this book is to educate readers who have a background in engineering and science and are familiar with topics such as statics, dynamics, mechanics of materials, thermodynamics, fluid mechanics, etc. There is absolutely no need for readers to have a background in anatomy, physiology, or even biology. Every chapter begins with a brief assessment of the related biological background followed by identification and explanation of the necessary features of the associated biomechanics problems.

Multiple topics such as biomechanics of human blood, orthopedics, and risk analysis have been discussed and analyzed in a variety of applications. Biological processes are amazing in their complexity and optimization. Blood, being no exception, is extremely evolved and adapted to the different scenarios necessary to maintain life. Consisting of plasma, white blood cells, platelets, and red blood cells, it is able to transport vital molecules around the body, including oxygen and clots in the case of injury. Since red blood cells make up approximately half the volume of blood, blood flow mechanics are largely related to the properties of red blood cells defined under a soft solid. Large deformability is essential in the life cycle and function of red blood cells as capillaries are extremely small. Blood clotting is a very important function of blood. All these concepts are admirably discussed in one chapter and readers with different backgrounds will follow and learn in an effective manner. The same concept applies to other chapters.

We all know that bone is a hard biological tissue. It is made up of cells located in the bone matrix, which is made up of mainly collagen fibers, amorphous ground constituent, and a mineral phase. The key components of bone mineral are known to be calcium carbonate and calcium phosphate. The mineral constituents contain primarily hydroxyapatite crystals and amorphous calcium phosphate. It is very well stablished that bone is the main reservoir for calcium in the human body. It also protects important organs such as heart and liver, provides mechanical stability, and is responsible for locomotion and movement of the human body. Bone structure is known to be hierarchical and is intended to be effectively optimal. Bone implants are considered as medical devices meant to substitute or provide fixation, or to substitute articulating surfaces of a joint. In other words, bone implants are designed to either support or substitute broken or damaged joints and bones. Bone implants are primarily made up of titanium alloys and stainless steel for their strength and are often co-used with a particular polymeric material as artificial cartilage. The main job of these implants is to decrease the stress in the implants and at the articulating surfaces. There are implants that are cemented into place and some that are pressfit, in a way the bone tissue in the vicinity of the implant can grow into the implant, hence, providing more strength and stability. The main aspect that guides bone healing is known as the interfragmentary movement, which regulates tissue strain and therefore the cellular response in the healing zone. The chapters in this area discuss comprehensively all these concepts in plain language.

**II**

**Chapter 6 87**

Trapeziometacarpal Joint: A Mechanical Explanation of Total

Prosthesis Failures *by Victoria Spartacus* Finally, I would like to thank my exceptional student, Emily Earl, who has been helping me throughout intellectually and technically in editing this book.

### **Hadi Mohammadi, PhD, PEng**

**1**

Section 1

Introduction

Assistant professor of mechanical and biomedical engineering and surgery, The Heart Valve Performance Laboratory, School of Engineering, Faculty of Applied Science, University of British Colombia, Kelowna, Canada

Section 1 Introduction

**3**

**Chapter 1**

Introductory Chapter:

Biomechanics or biomechanical engineering is the application of mechanical engineering and its concepts and principles in biological systems, living tissues/ organs, and medical devices. Mechanical properties of tissues can be characterized as anisotropy, hyperelasticity, viscoelasticity, viscoplasticity, preconditioning performance, and the existence of residual stresses [1]. Most experiments on the mechanical characterization of tissues are based on the laboratory work. Often, samples are removed from cadavers or animals and are cut in order to be tested which are either fresh or after storage. Testing machines are often based on electromechanical or hydraulic systems which are often performed in living animals or patients. Mathematical interpretation of data is often considered an important part of tissue mechanics such as 3D modeling of stress-strain behavior. Modeling may be either phenomenological, which is to some extent seeking to define behavior using model systems that do not reference structure, or plainly based on information of tissue construction. Phenomenological models are often based on linear or quasilinear viscoelastic theory. Constitutive equations, mostly those based on improvement of strain energy density functions, are often as a means to explaining tissue

Tissue mechanics or tissue biomechanics is the field of endeavor that seeks to understand and describe the correlations between structure, composition, and mechanical functionality in a variety of tissues such as connective tissues, cardiovascular tissue, epithelial tissues, etc., in the human body [2]. Much of the research work has been done in the connective tissues of the body, such as the bone, tendons, cartilage, arteries, and skin, where mechanical demands are greatest; however, all tissues have mechanical features of interest. An interesting area of research could be made around the (1) use of structural anatomy as a means to understanding natural design, (2) mechanical engineering analysis of structures based on continuum mechanics, and (3) materials science study of detailed links between structure and function. As all natural tissues are composite materials, understanding their mechanical function requires study of the mechanical properties and architectural arrangement of the individual structural components, particularly strong, stiff collagen fibers; the physiological rubber elastin; hydroxyapatite mineral; and proteoglycan sol/gels. The mechanical features of tissues include marked anisotropy, nonlinear stress-strain relations, viscoelasticity, preconditioning behavior, and the presence of residual stresses. Most studies of the mechanical behavior of tissues have been carried out in the laboratory, with samples removed from cadavers or animals, cut or machined to shape, and tested either fresh or after storage. Commercial testing machines based on electromechanical or hydraulic systems are

Biomechanics

behavior under random loading.

*Hadi Mohammadi*

**1. Introduction**

### **Chapter 1**
