Clinical Biomechanics.

Clinical Biomechanics Dvir Z, ed. Philadelphia, PA 19106, Churchill Livingstone Inc, 2000, hardcover, 287 pp, illus, ISBN: 0-443-07945-5, $49.95.

Dr Dvir's goal was to write a clinically oriented book that would serve as a reference rather than a textbook. To carry out the task, he assembled a team of 16 contributors, including 2 physical therapists. The book contains 10 chapters, each written by a different author or group of authors and each with a slightly different organization. Although only the shoulder and thoracolumbar regions are given chapters of their own, the practical aspects of biomechanical investigation in most regions of the body are at least discussed.

Chapter 1 is an introduction to measurement in biomechanics. Fundamental concepts are presented in an understandable, if less than rigorous, way. The use of models as a way of simplifying the analysis of complex problems is introduced, along with free body diagrams, coordinate systems, and a short discussion of vectors and tensors. The chapter authors then introduce the equipment used to measure position, acceleration, and force and briefly discuss when to select goniometers, load cells, strain gauges, force plates, electromyography, and optical and nonoptical motion analysis systems.

The next 3 chapters are devoted to the mechanical properties of non-contractile soft tissues, bone, and muscle. Chapter 2 is particularly well-organized, with sections on properties of cartilage, collagen, the intervertebral disk, ligaments, and tendons. Each section covers biomechanical modeling, clinical features, effects of aging, and injury and repair. The section on cartilage is somewhat more detailed than the others, with more information at the molecular level. Chapter 3 discusses the mechanical properties of bone, and it is well done from the mechanical standpoint, including fracture mechanics. However, the chapter contains limited information on piezoelectricity, healing, bone transport, or the effects of aging. Chapter 4 provides an excellent discussion of how muscle physiology and mechanical properties interact, with brief reference to muscle models.

Chapter 5 covers thoracolumbar spine biomechanics, including the role of bony deformation within the vertebral bodies in shock attenuation. The chapter author examines the current evidence regarding the role of muscles and the thoracolumbar fascia in stabilizing the spine, and he offers some pertinent and well-informed ideas on the prevention of back injuries.

Chapter 6 contains reasonably comprehensive coverage of stability and mobility around the shoulder. The chapter is written from the clinician's point of view, and it offers a survey of current clinical research on shoulder function, while providing limited discussion of current biomechanical shoulder models. Much of this material is available in current biomechanical texts.

Chapter 7 emphasizes the consequences of loss of force production resulting from the impaired motor control associated with many neurologic disorders. The chapter's primary focus is on cerebrovascular accidents (CVA). The author provides well-written, evidence-based critiques of current clinical practice.

Chapter 8 discusses the biomechanics of standing posture, emphasizing recordings of postural sway and frequencies of sway in people without impairments, patients with CVA, and patients with amputations. Using a 5-segment model, the chapter author proposes to identify the features of postural sway that can serve as a means of diagnosis and a focus of rehabilitation.

Chapter 9 addresses biomechanical issues in manual therapy, primarily spinal manipulative therapy. The chapter authors make the distinction between manipulation as a "high-speed thrust" and mobilization techniques that have "slow loading rates." Using a lumbar spine model, methods for describing joint

motion, applied force, and response to manipulation are presented, along with a limited discussion of tissue effects. The authors make a good effort to outline the important variables that must be studied more fully in order to understand the mechanism of spinal manipulative therapy. Readers wishing an even more detailed discussion of these issues may wish to consult Clinical Biomechanics of Spinal Manipulation by Walter Herzog, one of the chapter's coauthors.

Chapter 10 deals with biomechanics of lower-extremity orthoses. The chapter author discusses the gait cycle, classification of orthoses, and structural properties of orthotic materials. The lack of current research on load distribution within an orthosis is underscored, and the author suggests ways to measure the effectiveness of orthotic intervention. A significant section of the chapter is devoted to the indications and appropriate prescription of several types of lower-extremity orthoses.

Although the book's emphasis on evidence-based practice underscores the paucity of data available in some areas, the distinguished chapter authors should be congratulated for attempting the difficult task of presenting biomechanics from a clinical point of view. In spite of some differences in presentation, they generally do a good job of summarizing their particular subjects and pointing the way toward testable clinical hypotheses.

Roy Bechtel, PT, PhD University of Maryland Baltimore, Md

Dr Bechtel is Assistant Professor of Physical Therapy. He teaches courses on biomechanics and spinal orthopedics. His doctoral work focused on the biomechanics of the sacroiliac joint.