7R23. Bone Mechanics Handbook, 2nd Edition. - Edited by SC Cowin (CUNY, New York NY). CRC Press LLC, Boca Raton FL. 2001. ISBN 08-493-9117-2. \$169.95.

Reviewed by JJ Telega (Inst of Fund Tech Res, Polish Acad of Sci, Swietokrzyska 21, 00-049 Warsaw, Poland).

Bone mechanics belongs to one of the oldest and best-developed fields of biomechanics. It is still being developed, both from the traditional and modern points of view. New trends in bone mechanics owe much to the micromechanics, particularly to homogenization and tissue engineering, as well as to cell and molecular biology.

This impressive volume (over 950 pp), edited by a well-known specialist in bone mechanics, also includes these new developments and trends. It clearly shows that bone mechanics has become a strongly interdisciplinary field of research.

The book consists of six sections, each of which in turn includes several mostly review articles written by various acclaimed authors. The first section is concerned with basic biological aspects of bone including some molecular techniques applied to measure skeletal gene expression. The following topics have been discussed: i) integrated bone tissue physiology: anatomy (WSS Jee), $ii)$ cell biology of bone (RJ Majeska), $iii)$ molecular biology techniques to measure skeletal gene expression (MF Young and SC Dieudonne´), $iv)$ creating transgenic mice to study skeletal function (MF Young and T Xu), and $v)$ bone mineralization (AL Boskey). To grasp the content of Section I the reviewer had to study a book on molecular biology and biochemistry first.

Section II opens with a paper by SC Cowin on basic notions of the mechanics of materials presented at the simple and lucid level of strength of materials. Two subsequent papers (one by CH Turner and DB Burr, another by GSP Fritton and CT Rubin) deal with testing methods applicable to bone as a structure and material. Micro- and nano-testing, as well as acoustic tests, have also been concisely described. Bone has a hierarchical architecture, and an important problem is to perform tests on single lamellae and trabeculae. In bone mechanics not only human bones are tested, but a lot of research has been devoted to animal models for biomechanical tests. Advantages and disadvantages of tests performed on animals are briefly discussed. Of the other two experimental papers mentioned, the second one deals with the development of strain gauges for use with bone and tabulates the in vivo strain measurements recorded over the years to quantify the mechanical loading environment of the skeleton. The tabulated data, obtained by various authors over the years, are of great value. In the last paper of Section II by P Ru¨egsegger, the available techniques of bone structure imaging are described. The techniques include X-ray, computer tomography (CT), micro-CT, synchrotron-CT, magnetic resonance imaging (MRI), and micro-MRI. Spatial resolution, advantages, disadvantages, and applicability of each of these techniques have been analyzed.

Section III, the longest one, contains 11 papers. The first of them by XE Gao, strongly related to the experimental papers of Section II, is concerned with mechanical properties of the cortical bone and cancellous bone tissue. Microindentation and nanoindentation tests used to characterize the bone tissue properties have also been characterized. The second paper, by R Lakes, deals with the bone viscoelasticity, a topic always somewhat controversial. The author claims that the physical cause of viscoelasticity is, at least partially, due to fluid flow in a porous material like bone and to interfaces such as the cement lines (the biological significance is not known). The authors of some of the previous papers claimed that cement lines contribute to plastic (time-independent) behavior of wet bone. The unanswered question is: is the mechanical behavior of cement lines time-dependent or time-independent? In the subsequent paper, E Lucchinetti reviews some approaches to macroscopic bone modeling where bone is treated as a composite. For instance, consider a bone as a two-phase material. This is an old problem in the mechanics of composites and micromechanics. The author has reviewed older approaches, like those due to Voigt and Reuss, as well as newer ones proposed by biomechanicians. Unfortunately, vast possibilities offered by modern micromechanics, homogenization, and bounding techniques have not been exploited except for a contribution on reiterated homogenization. (This reviewer and his coworkers wrote many papers on application of homogenization methods to bone modeling See the relevant papers in Acta Bioeng. Biomech, Vol 4, Supplement 1, 2002—Proc of 13th Conf of Europ Soc Biomech, September 1–4, 2002, Wrocław, Poland). In a subsequent paper, Lucchinetti reviews the results concerning the increasing evidence that the mechanical properties of the bone depend not only on its microstructure, but also on the molecular structure of the organic and inorganic components.

Three subsequent papers are exclusively devoted to cancellous bone. The purpose of the first paper, by A Odgaard, is to overview available methods for quantification of the architecture of cancellous bone. Only the methods applied to histological sections and 3D reconstructions have been discussed. The author claims that “The trabecular arrangement in cancellous bone is obviously not random” and provides some arguments for this. His arguments prove the contrary: the cancellous bone architecture may be viewed as random and described by using the geometry of random fields. The second paper, by B van Rietbergen and R Huiskes, is concerned with the anisotropic behavior of cancellous bone and how it is related to its microstructure. Particular emphasis has been placed on micro-finite element analyses, unfortunately requiring usage of supercomputers. It has been shown that orthotropy is a good approximation for cancellous bone. Relationships based on fabric tensors have also been discussed. In the third paper, TM Keaveny overviews the strength properties of trabecular bone and identified areas where unresolved problems and gaps exist. The strength criterion usually used in trabecular bone mechanics is the Tsai-Wu criterion, primarily developed for fiber-reinforced composite materials. In fact, this criterion should be called Hoffman criterion (see Jemioło and Telega, Fabric tensors in bone mechanics, Engineering Transactions, 46(1), 1998, pp 3–26.

The following papers are concerned with damage in bone. The first of them, by KJ Jepsen, DT Davy and O Akkus investigates three complementary methods of characterizing damage in bone: the process of damage based on property degradation, the physical characterization of damage via histological and histomorphometric means, and real-time characterization of damage based on AE (accoustic emission). Explaining residual strain the authors have not stressed the important role played by anisotropy, inhomogeneity and remodeling. The paper by TD Dwight and KJ Jepsen provides an overview of model suitable for modeling bone damage. The models discussed include also fatigue damage and micromechanical models. Unfortunately, damage and repair models, important for the description of bone remodeling, have been limited to one-dimensional models.

The second to last in Section II (by JD Currey) provides some answers related to ontogenetic changes in (mainly) compact bone material properties. The discussion ranges from fetal bone to senescent changes and clearly shows that a lot has to be done to better grasp this aspect of bone behavior. The last paper in this Section RB Martin and NA Sharkey reviewes three topics: i) postmortem changes in mechanical properties of bone (for instance, influence of cell death), $ii)$ the mechanical effects of preserving bone (freezing, chemical preservation), and $iii)$ the mechanical effects of storing and treating allograft bone (lyophilization, irradiation, methanol and chloroform treatment, thermal sterilization).

Section IV includes five papers on various aspects of fluids flow in bone. The physiology of blood flow in bone is reviewed by H Winet. More precisely, the author discusses the vascular levels, typical for blood circulation: arteries→arterioles→arteriolar capillaries→capillaries→venular capillaries→ venules→veins. Next, ML Knothe Tate focuses her review on various aspects of interstial fluid flow, including molecular transport mechanism in bone. This paper is somewhat complementary to the subsequent article by Cowin who reviews possible application of poroelasticity to flow of bone fluids. Among many aspects of this flow, it is worth noting that poroelasticity and electrokinetics can be used to explain strain-generated potentials in bone. The article by SR Pollack synthesizes the historical perspective of the passage from piezoelectricity to streaming potentials (in wet bones) and discusses current views on electrokinetics in living bone. It is now commonly believed that just electrokinetics is the underlying phenomenon accounting for the mechanoelectric observations in bone at frequencies less than $106 Hz.$ In the last paper of Section IV, YP Arramon and EA Nauman discuss lucidly the various terms, theories, and conventions used in the study of the permeability within the context of fluid flow through cancellous bone.

Section V, comprising seven interrelated papers, is concerned with a very broad spectrum of bone adaptation problems: from cell level to macroscopic modeling. In the first paper, AE Goodship and JL Cunnigham discuss the role of the genetic component and mechanical loads as well as transduction pathways in bone remodeling. It seems that we still lack mathematical models incorporating the component mentioned. In the next paper, TD Brown reviews the instrumentation and protocols that have evolved for in vitro mechanostimulus testing of bone cells, for instance hydrostatic compression, direct platen contact, substrate distension or bending fluid shear and combined stimuli. The subsequent two papers, the first by EH Burger and the second by SC Cowin and ML Moss, deal with mechanosensitivity and mechanotransduction phenomena in bone. Though many aspects remain purely speculative, the role of osteocytes in the mechanosensory process has been established experimentally (Burger). Severe criticism of what came to be known as “Wolff’s law” has been provided by SC Cowin. This author traces back the original development of functional adaptation of bone to loading and provides purely static arguments why the trajectorial theory is false. A review (not exhaustive) of models describing functional adaptation of cortical and trabecular bones is provided by RT Hart. In the reviewer’s opinion, most of the available models are just modifications and possibly extensions of the adaptive elasticity model (viscoelasticity may be treated similarly). In the subsequent paper, PJ Prendergast and M van der Meulen review the biology of bone healing and the theories that describe the regulation of bone regeneration by mechanical forces.

The last section entitled “Clinically related issues” consists of four papers. In the first paper, ML Villarga and CM Ford synthesize the state-of-the-art in the understanding of hole-bone mechanics, and in particular as it relates to whole-bone fracture. Next, JJ Kaufman and RS Siffert discuss methods for noninvasively measuring skeletal integrity (X-ray densitometry, ultrasonic techniques, micro-CT, MRI). In the subsequent paper, Prendergast shows that replacement or augmentation of bone by prostheses has led to a prolific number of devices with one common aim—to alter the load transfer in bone fissue. More precisely, this author briefly discusses biomaterials used for replacement of bone in the human body (metals, ceramics, and polymers), design of bone prostheses, analysis and assessment of implants including preclinical tests and clinical data. The last paper in this book, by SJ Hollister, TMG Chu, JW Halloran and SE Feinberg, summarizes current work on scaffold design and fabrication for bone tissue engineering. The authors discuss three topics: design, fabrication, and overall concept from design to in vivo testing.

This reviewer really enjoyed reading Cowin’s book, though it is by no means self-contained, particularly in respect to notions from genetics and molecular biology. If a third edition of the book is planned, this reviewer suggests publishing the book in two volumes and include a comprehensive chapter on indispensable ideas and notions from biology, genetics, and molecular biology. Having read the book, the reader still will have no clear idea what terms, such as plasticity and yielding really mean, unless he is well acquainted with metal plasticity. Despite this, the amount of valuable material and often tabulated data is strikingly enormous. The book is well balanced and covers almost all currently important aspects of bone mechanics. Existing controversies and indications for future research are discussed in many of the papers. This reviewer strongly recommends Bone Mechanics Handbook, 2nd Edition to biomechanicians, not only to those interested in bone mechanics. Since the mechanical aspects of bone behavior have been presented in a lucid manner, the book will also be very useful to biologists and biophysicians involved in bone research. Having in mind the rich contents of the book, its price is by no means elevated.